RAPID PROTOTYPING - AN OPPORTUNITY FOR CHANGE

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More commonly referred to as 3D Printing and touted as the future in 2013. A report of mine about it from 20 years earlier!

"This report investigates the opportunities available to the Thorn Lighting Group by using 'Rapid Prototyping' technologies. It considers the implementation issues and cost / benefit analysis. The report indicates several paths forward."

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RAPID PROTOTYPING - AN OPPORTUNITY FOR CHANGE

  1. 1. RAPID PROTOTYPING - ANOPPORTUNITY FOR CHANGE?By Simon Major,Technology Centre, Thorn Lighting Group,October 1993.Summary:This report investigates the opportunities available to the ThornLighting Group by using Rapid Prototyping technologies. Itconsiders the implementation issues and cost / benefit analysis.The report indicates several paths forward.
  2. 2. Page iiBRIEF CONTENTS1. Introduction........................................................................................................................52. The Available Technologies ..............................................................................................93. Trials ..................................................................................................................................224. Approaches ........................................................................................................................285. The Future..........................................................................................................................386. Contacts..............................................................................................................................417. Recommendations..............................................................................................................478. Conclusions........................................................................................................................49Index ......................................................................................................................................50
  3. 3. Page iiiDETAILED CONTENTS1. Introduction........................................................................................................................51.1. Aim......................................................................................................................51.2. Objectives............................................................................................................51.3. What is Rapid Prototyping? ................................................................................51.3.1. The Subtractive Alternative..................................................................51.3.1.1. Opportunities within the Thorn Lighting Group ...................61.3.2. The Additive Processes ........................................................................71.4. Thorn Lightings Current Approach ....................................................................72. The Available Technologies ..............................................................................................92.1. Model Production................................................................................................92.1.1. Model Preparation ................................................................................92.1.1.1. Orientation.............................................................................92.1.1.2. Subdivision............................................................................112.1.2. The STL File.........................................................................................112.1.2.1. Packing the Machine .............................................................122.1.2.2. STL Manipulation by the Specialist......................................122.2. The Processes......................................................................................................132.2.1. Photo Curing (Stereolithography) ........................................................132.2.1.1. Raster Scanning verses Masking...........................................132.2.1.2. Post Curing............................................................................142.2.2. Selective Laser Sintering (SLS) ...........................................................142.2.3. Laminated Object Manufacture (LOM)................................................152.2.4. Deposition ............................................................................................152.2.5. Selective Binding..................................................................................162.3. The Machines......................................................................................................162.4. Comparisons........................................................................................................192.5. The Bureaux........................................................................................................203. Trials ..................................................................................................................................223.1. The History of Mk 14 Pop Pack..........................................................................223.2. The Son Pak ........................................................................................................233.3. The Adagio Arm..................................................................................................233.4. The Jubilee Line Extension.................................................................................264. Approaches ........................................................................................................................284.1. Applications ........................................................................................................284.1.1. Freeform Styling and Geometry...........................................................284.1.1.1. Prosthetics .............................................................................284.1.2. Rapid Tooling.......................................................................................294.1.2.1. Currently Feasible Techniques ..............................................294.1.2.2. Processes Under Development..............................................294.2. Resources ............................................................................................................314.2.1. In-house................................................................................................314.2.2. External Bureaux..................................................................................324.2.3. The ‘Thorn Lighting Bureau’ ...............................................................32
  4. 4. Page iv4.2.4. Collaborations ......................................................................................324.3. Philosophy...........................................................................................................324.3.1. Concurrent Engineering........................................................................334.3.1.1. Testing...................................................................................334.3.1.2. Production and Standards Engineering .................................344.3.1.3. Assembly...............................................................................354.3.1.4. Packaging ..............................................................................354.3.1.5. Marketing ..............................................................................354.3.2. Right First Time ...................................................................................354.3.2.1. The Son Pak...........................................................................364.3.2.2. Competitive Designs .............................................................365. The Future..........................................................................................................................385.1. The Interface........................................................................................................385.2. Processes .............................................................................................................385.3. Specialist Production...........................................................................................406. Contacts..............................................................................................................................417. Recommendations..............................................................................................................477.1. The Short Term ...................................................................................................477.2. The Long Term....................................................................................................478. Conclusions........................................................................................................................49Index ......................................................................................................................................50Figures........................................................................................................................50Tables .........................................................................................................................50Plates ..........................................................................................................................50General Index .............................................................................................................51
  5. 5. Page 51. INTRODUCTION1.1. AIMThe aim of this report is to identify the opportunities open to the Thorn Lighting Groupregarding the use of ‘Rapid Prototyping’.1.2. OBJECTIVES• To identify all the Rapid Prototyping techniques and characterise their differences.• To determine the opportunities that Rapid Prototyping presents.• To carry out cost/benefit analysis on the techniques.• To identify the pit falls of pursuing the different avenues.1.3. WHAT IS RAPID PROTOTYPING?‘Rapid Prototyping’ is the generic name given to a group of techniques for achieving acommon end. This end is to produce a physical representation from any visual one in a shorttime. The qualifier of ‘in a short time’ is vague - the only consistent definition is: a smallfraction of the time taken to produce the required production tooling (or program) and thenmanufacture the first part. The initial visual representation must be three dimensional in orderfor the physical representation to be produced. The visual representation used is therefore athree dimensional CAD model.Rapid Prototyping techniques cannot produce a part at competitive long run productionprices. It can therefore only be used to produce one off items or prototypes - hence its name.The approaches to forming a component can be classified as: additive, uniting1, casting2,subtractive and reforming. This list is in descending order of flexibility of the geometry thatmay be produced. Rapid Prototyping techniques generally use processes belonging to the firstclassification. It will be demonstrated that the first three techniques have to be used inconjunction to achieve the desired results.1.3.1. The Subtractive AlternativeThe alternatives to the specialist additive techniques are the more limited subtractive ones. Inpractice this is the automatic programming of CNC machining centres direct from a CADmodel. This is a very useful capability if the company is in the business of producingcomponents by CNC machining - the Thorn Lighting Group is not. These techniques may beused for more generic prototyping, but the geometry that can be produced is limited. Most1 This process requires sub-components that are usually produced by other techniques.2 This process requires a mould to be produced. The mould must be manufactured by other techniques.
  6. 6. Page 6machines in use are three axis ones; such a three axis boring or milling machine cannotproduce the following simple geometry without human intervention:Figure 1 ‘Free Hand Sketch of a Non 3 Axis Geometry’.It would be possible to make this shape automatically using a four axis machine. It is notdifficult define geometries that will defeat a five or six axis machine. At this level ofcomplexity the machines are extremely expensive.There have been some successful applications of subtractive Rapid Prototyping techniques:some motor manufactures, e.g. Renault uses 5 axis machines to rough out the shapes for theirbody styling model makers; another application area is ‘bottle’ modelling. The model is solidand produced in two halves. A common piece of CAD/CAM software used for this isDelcam. It is necessary to form to halves of a mould and two halves of a core to make ahollow bottle. In contrast the additive techniques can produce these geometries directly - thenew fluted Coca Kola bottle was prototyped this way.1.3.1.1. Opportunities within the Thorn Lighting GroupThere is a single three axis milling machine within the Thorn Lighting Group UK, and this isat Hereford. The situation regarding the foreign operations is unknown. The investigation ofthe use of Bridgeport Interac 4 machine has not resulted in any success. The situation hasbeen left with the manufacturer pursuing the software problems; but it is the authors opinionthat there is no future down this avenue.1.3.2. The Additive ProcessesAll the Additive techniques used in Rapid Prototyping ‘grow’ a model in layers. The threedimensional shape is divided into sheets that are stacked to form the model. This cycle isdepicted in the following exaggerated figure:
  7. 7. Page 7Figure 2 ‘Lamina Model Construction’.The figure demonstrates that there is a vertical tolerance of a lamination thickness. Thisdistance is of the order of a tenth of a millimetre. This gives the impression that such a laminamodel is very coarse. The problem is mitigated by a significantly higher accuracy in thehorizontal plane; however surface finish is probably the largest weakness in the currentgeneration of technologies.1.4. THORN LIGHTINGS CURRENT APPROACHThe company uses three general classes of components:1. Fabricated sheet metalwork.2. Plastic mouldings and metal castings3. ExtrusionsThe sheet metalwork components do not need a special prototyping process as it is easy tomake these by hand; and it is not very difficult to program the flexible production machines;also neither of these methods are expensive. The same cannot be said for the remaining
  8. 8. Page 8classes. There is therefore the potential for the application of Rapid Prototyping techniques.Both of the remaining classes follow one of two routes3:Direct development of production tooling - lower cost production tooling is produceddirectly from the detail designs. These tools tend to be single impression in the case ofmoulds. This approach has the danger that the design may not be perfect. The toolthen has to be reworked and the costs have risen significantly above the originalestimates.Using soft tooling - a lower cost single impression tooling is used for pre-production work.This tooling has a short term life span as it not made of hardened material. When thedesign is finalised the production tooling is produced.Either route is normally preceded by prototypes made in the model shop4. These models areconstructed from fabrications and machined pieces. These techniques work well for mostcomponents. The exceptions are: if the geometry is too complex; or the component is toosmall and fiddly. It should be noted that some capabilities are sub-contracted.3 The author is not aware of any use of permanent casting moulds; therefore there is no equivalent to using softtooling in the case of castings.4 This is extremely restricted in the case of extrusions.
  9. 9. Page 92. THE AVAILABLETECHNOLOGIESThe production sequence that is common to all the processes shall be described before theprocesses themselves. The following sections of the report will demonstrate that there is nowinner or ranking between the processes - different applications favour different processes.All the processes have some common limitations.2.1. MODEL PRODUCTIONAll the specialised processes occupy the same role in the Rapid Prototyping cycle:1. Three dimensional CAD design.(2. Model preparation to decrease cost and improve quality).3. File Generation.(4. The option of file manipulation if stage 2 was bypassed).5. The Rapid Prototyping building process.6. Post processing.(7. Model Reassembly).(8. Replication Casting).The stages 1 to 3 are completed by the in-house design function. The first four stages have aprofound impact on the cost and quality of final models; their influence is probably assignificant as the choice of process in stage 5. The issues regarding these early stages willnow be addressed.2.1.1. Model PreparationThere are choices that can be made regarding the orientation and the possible subdivision of amodel. These decisions respectively affect the quality and cost of the model. Further costsavings may be achieved by hollowing out parts of a model. The last point only applies tocertain processes.2.1.1.1. OrientationThere are three issues regarding orientation:1. Overhangs.
  10. 10. Page 102. Curved detail.3. Height.Overhangs do not affect some processes at all. All the other processes can cope with smalloverhangs; but the model will distort if large ones are present. There are two possibleremedies: the easiest, if it is possible, is to invert the model thus turning an overhang into abase. If the large overhangs cannot be eliminated this way then supports have to be modelledaround it.In section “1.3.2. The Additive Processes” the difference in horizontal and vertical accuracywas described. The effects of this are most noticeable in the curved details of a model.Consider the modelling of a cone: if this is oriented with its axis vertical then it constructedfrom a stack of circular discs; however if oriented with its axis horizontal then it isconstructed from a stack of triangles. A second example is a plain hole: with its axis verticalit is perfect; whereas if it is horizontal it has a stepped circumference.In section “2.1.2.1. Packing the Machine” the importance of filling the modelling volume isdiscussed. The volume that needs to be filled is not the maximum capacity of the machine -the depth need only be slightly greater than the height of largest model. It is thereforedesirable to orient a model to minimise this height. The situation is not as simple as orientingall the components for minimal height if the process requires model supports. This isdemonstrated in the following figure:Figure 3 ‘Stacking in a Rapid Prototyping Machine’.Vertical stacking of models that are not self supporting is not very practical. The figuredemonstrates that complex supports with complete bases may be needed. If vertical stackingis not used it can be seen that orienting all the components for minimum height is not the best
  11. 11. Page 11approach for the example shown in the figure. It is generally the case that processes that donot need support can achieve much greater packing densities. These processes also allow therule of minimum height orientation to be used all the time.2.1.1.2. SubdivisionThere are three reasons for subdividing a model:1. Size.2. Packing efficiency.3. Variable geometry complexity.4. Height reduction.The size of component that may be produced in one piece by Rapid Prototyping is limited.The size ranges from ‘small’ machines with a base in the order of 10" square; to the largestmachines with a base approximately 20" square. Larger components can therefore limit thechoice of machine.The parts modelled using Rapid Prototyping have complex geometries - simple geometriescan be made by other means. These complex geometries contain a large volume of emptyspace within the envelope of their overall dimensions; consequently they do not pack veryefficiently into the volume of the machine. It the parts envelope volume that most commonlydetermines the cost of the model. It is therefore desirable to subdivide the model into severalcomponent parts that are more volume efficient.A model may consist of a section of complex geometry joined to a bulky piece of simplegeometry. Rapid Prototyping only the complex section may save money in suchcircumstances. The rest of the part is produced by other means and then the two are reunited.The need to reduce the height of the model in the machine was discussed in section “2.1.1.1.Orientation”. If the highest point of a part is the tip of a significant protrusion; this can besliced off and modelled separately.2.1.2. The STL FileRapid Prototyping requires a transfer of geometric information between a CAD machine andthe building machine. There are a large number of incompatible CAD information formats -an interchange format is required. The de facto standard is the STL file format that wasdeveloped by the original supplier - 3D Systems.The cost reducing measures described in the in the preceding sections can either by applied tothe CAD representation or the STL representation. The former requires that the originator hassome prototyping expertise; whereas the latter can be dealt with by the Rapid Prototypingspecialist. The latter option would seem preferable as some of the activities refer directly tothe machine.
  12. 12. Page 122.1.2.1. Packing the MachineOnly some of the building processes can recover the material not used in the manufacture of amodel. If a process cannot recover the waste then this waste must be minimised; therefore thevolume of the machine must be packed with models as tightly as possible.It is also beneficial to pack a machine that uses a process that can recover waste. Theproduction time for a machine building 30 parts is considerably shorter than the than 30 timesthe production time of the same machine producing a single part. The production time is animportant consideration because the cycle times are extremely long - typically 3 to 30 hours!2.1.2.2. STL Manipulation by the SpecialistThe model originator would produce a STL version of the basic model and pass this to thespecialist; they would then carry out all the manipulation to produce the cheapest, highestquality models. The only problem with this scenario is the STL file format itself. The formatwas made compatible with all the CAD systems by making it a universal simplification. TheSTL version is a faceted approximation rather than a true representation of a geometry - allthe surfaces of the model become meshing triangles. Any manipulation of STL file will notcompletely correlate to the true model. If the same manipulation is carried out on the CADmodel and to a STL file it is then possible to convert the new CAD model to a STL versionfor comparison. It is not likely that the two STL files exactly match! The differences will besmall and so the errors are normally insignificant; however it will be shown that a RapidPrototyping model is prone to accumulate errors.The facetting may either be fine or coarse. If the facets are similar in size to the laminathickness then there is no degradation of the final model. Very large facets will be visible infinal model. This facetting introduces a normally insignificant amount of dimensional error. Italso spoils the appearance of an already poor surface finish. The irony is that the problem isnot with areas of high geometric complexity; instead it is with the simple features such as acylindrical wall! The standard practice is to smooth the surface by removing material. Thisalso introduces dimensional error.These errors make Rapid Prototyping unsuitable for modelling extremely precise functionalfeatures such as interference and tolerance fits. This is not a problem for the Thorn LightingGroup as the components that would prototyped are not of such high precision.One problem Thorn Lighting does not have is with the CAD models. The company uses asolid modelling CAD environment - which is the best possible type for STL file generation.Other systems can produce problems that require the STL file to be ‘fixed’ by the specialist.The company also has the software to convert its CAD files to STL files. What it would nothave is any control over the process. This is because the company has no STL viewing ormanipulation capabilities.Viewing facilities can be implemented by converting the STL format generated back into aCAD file. This file is not the same as the original geometry; instead it is a CAD model offaceted object that is similar to the original. Any problems, such as large facets, would thenbe visible in the CAD system. The best facilities available allow the coarseness of the STLconversion to be adjusted; they even allow this to be set differently for different parts of the
  13. 13. Page 13model. Thorn Lighting is unlikely to get any of these facilities from Hewlett Packard as ourSTL generator was supplied free and without any support.Is there any alternative to STL? There are a couple of competing proprietary file formats thathave not taken off. There is a need for a new format. The development in this area isdiscussed in section “5.1. The Interface”.2.2. THE PROCESSES2.2.1. Photo Curing (Stereolithography)There are a number of different suppliers that use variants of this process; while the otherprocesses are only used by single suppliers. This is the original, and hence the mostcompetitive, form of Rapid Prototyping. The majority of people only know this process ifthey are even aware of Rapid Prototyping. This process was used in over 93% of the worldsmachines in early 1992, but this figure is falling.The layers of the model are produced by the selective curing of photosensitive polymer resins.There is a wide variation on how this is achieved. Most of these systems require supports forlarge overhangs; but all of them recover waste. The systems that do not require supports havea more complex layer building cycle: after a new layer is cured the uncured resin is removedand replaced by a support material, e.g. wax. The quality of models produced using thesetechniques are dependent upon both the physical methods used and the qualities of the photo-polymer. It is very easy to overlook the effects of the latter.The most ignored part of the Rapid Prototyping cycle is the cleaning stage - the removal ofunused material from the model. In the systems that are not self-supporting the model comesout of the machine covered in uncured resin. This is thick and sticky. It must be removed withthe use of unfriendly solvents. The support material used in self supporting systems isintended to be easily removed; however it should be remembered that the mixed materialfrom such a process has to be removed from the machine as one large solid block!2.2.1.1. Raster Scanning verses MaskingThere are two possible approaches to selective curing: raster scanning and masking. In theformer the area to be cured is raster scanned by a laser. The masking technique is morecomplicated: a mask of the area is prepared photographically or by electrostatics. The mask isthen used to shield the layer that is bathed in light. After the layer has cured onto the modelthe mask is cleared and the cycle repeats.The two techniques have different implications for material properties of the model. Differentmanufactures will argue over which method is superior. The author is inclined to think thatthe masking systems result in higher quality models; but these systems are more expensive.The two techniques have different weakness: raster scanning causes stresses within each layerthat are dependent upon the scanning patterns; masking avoids such stresses but according toraster manufacturers it can suffer from weak inter layer bonding. The result of is that the less
  14. 14. Page 14sophisticated resins tend to produce models that are brittle. No photo-polymer resins haveparticularly good machining properties.Raster Scanning manufactures compete with each other on the grounds of the fine detail oftheir scanning techniques. This can be deceiving as the final quality is highly dependent onthe resins used.2.2.1.2. Post CuringIf the layers are cured by raster scanning then there are two options: the area may be curedcompletely by the laser, or it can be partially cured by the laser and the completed model isthen cured later. This post curing is achieved by bathing the model in light whilst it rotates ona table. The difference between the two processes is that the partial curing allows the layers tobe built more quickly. The problem with post curing is that it causes shrinkage and distortion.This tendency is highly dependent on the quality of the resins.If the geometries are highly curved and thick walled then the model is self reinforcing. In thiscase there is no distortion. Distortion is most likely to occur in thin walled, large area, flatsurfaces.2.2.2. Selective Laser Sintering (SLS)The layers are produced by selective local sintering of powdered material. The localisedsintering is achieved by raster scanning with a laser. Presently the process is used without anypost sintering. The unsintered material is recovered after the completion of the model. Beforethis the unused material fully supports the growing model. The process has another advantage- the material does not have to be specialised, and can therefore be changed among productionmaterials. The ease and speed of a material change are issues. Any implementation that wouldrequire frequent material changes is not likely to be successful: apart from the change overtime it increases work in progress and the throughput time. This can be explainedhypothetically: if it takes 10 parts to economically fill the machine then the work in progressis at least 10 parts, i.e. you must wait for a ten part backlog to accumulate before you can runthe machine. The work in progress and the throughput time are doubled if the machine is usedequally for parts in two different materials. The process therefore becomes half as ‘rapid’.The process is not perfect - it achieves a sintered density equivalent to that of only a lowquality production sinter process. On the positive side the process does not suffer anyshrinkage or distortion, and the model is in a production material.The cleaning process for selective laser sintering is easy and environmentally friendly. Thenon hazardous powder is blown from the model using compressed air.2.2.3. Laminated Object Manufacture (LOM)This is a very simple system with that has unique advantages and disadvantages. The materialis neither a fluid or a powder; instead it is a roll of specialised sheet material. The sheet is a
  15. 15. Page 15bulk material that has a thermally setting adhesive on the back. The bulk material can bemetal or plastic, but it is usually paper!The roll is wound across the top of the stack of model and support material. A new layer isadded by winding on a length of roll; then cutting out the profile of the layer with a laser;finally the layer is completed by passing a heated roller over the length of the stack. Thisbinds the layer to the one below using the adhesive.The advantages of the process are: that the machine is cheap to purchase and run; the model isself supporting and suffers no shrinkage or distortion; and a paper/adhesive laminate comesout with material properties and appearance of wood. Wood is very easy to rework. This is animpressive list; unfortunately the it has a huge disadvantage at the cleaning up stage. Themodel comes out of the machine in a fused block with the support material and has to hackedout. For the same reason the process is hopeless for enclosed volumes because it becomesimpossible to dig out the waste material.2.2.4. DepositionThere is one established deposition technology, though there are several particle depositiontechnologies in development. These are discussed in the section “5.2. Processes”. Theestablished technology extrudes a fine stream of thermoplastic paste. An unflattering analogyis to imagine modelling with tube of toothpaste. This process can be adjusted between, slowbut high quality, or fast and coarse. There is no waste and a single part may be produced justas economically as many. This allows the work in progress to be low which makes this themost rapid Rapid Prototyping for low volume users. The process can use a variety ofmaterials that can be changed over easily.The principle limitation of the system is that there is no support material and it is very poor atunsupported geometry. This problem could be cured by having a second tool extrudingsupport material. The system would then be extremely effective. The system is clean enoughto be office based and there is no clean up stage required.2.2.5. Selective BindingSelective binding is presently a more specialised technique. It is used the rapidly produceceramic shell castings. The approach is most closely related to selective laser sintering. Thematerial in this case is a ceramic powder; and instead of local sinter there is local spraying ofa binding agent using inkjet technologies. The model is fired after completion. This process isof little interest to the Thorn Lighting Group.2.3. THE MACHINESThis section contains a brief summary of the details of every Rapid Prototyping system thatthe author has been able to find. The descriptions refer to the definitions in section “2.2. TheProcesses”. The manufacturers are listed in order of market share; or if their market share isunknown then they are placed towards the end of the list.
  16. 16. Page 16Manufacturer Product Details3D Systems SLA-500 The original Rapid Prototyping manufacturer.The machines use a UV raster scanned photo-curing process with post curing. The process isnot self supporting.They have been developing their resinscontinually; these are supplied by Ciba-Geigy.Model size: 20"×20"×24"Capital: $420000 @ Dec. 92SLA-250 Model size: 10"×10"×10"Capital: $210000 @ Dec. 92SLA-190 Model size: 7.5"×7.5"×9.8"Capital: $95000 @ Dec. 92Stratasys threedimensionalModellerDeposition system that can change among 3materials: a nylon like thermoplastic; amachineable wax; and an investment castingwax. Its biggest benefit is that its model costsdo not soar at low levels of utilisation. Theprocess cannot cope with significantoverhangs.Model size: 9"×12"×13"Capital: $178000 @ April 91Cubital Solider 5600 This is the Rolls Royce of the RapidPrototyping world. The process is photo-curingbut it is self supporting UV masked and thereis no post curing. The models produced haveone of the best surface finishes; they are verystrong for a photo-polymer; and the models donot shrink or warp. The Solider is designed forvery high throughput of models with manymodels packed into a single production cycle.The machine is huge and permanently manned;if not used at capacity it is extremelyexpensive. It has good facilities: layers can beerased if something goes wrong; if a model issplit the software will automatically hole anddowel the mating surfaces to assist inreassembly. The post processing consists ofdissolving off the support wax in a mild acidbath.Model size: 20"×20"×14"Capital: $550000+ @ Dec. 92
  17. 17. Page 17DTM Sinterstation2000The process is selective laser sintering. Thematerials currently available are nylon,polycarbonate and an investment casting wax.Model size: 15"×12"∅Capital: $95000 @ Dec. 92Helisys LOM 1015 The process is laminated object manufacture.The rolls available are paper, polyester andmetallic. A feature of this machine is itscompactness.Model size: 14.5"×10"×14"Capital: $95000 @ Dec. 92LOM 2030 This is a new larger model.Model size: ? 20+" (Worlds largest)Capital: $180000 @ Dec. 92Soligen Inc. DSPC The process is selective binding using ceramicpowders and colloidal oxide binders toproduce ceramic shell castings. Thetechnology is based upon that developed byMIT.Model size: 12"?×12"?×24"?Capital: $200 - 250000? @ Dec. 92Light SculptingInc.LSI-0609 An alternative photo-curing process that usesmasked UV.Model size: 6"×6"×9"Capital: $99000 @ Dec. 92LSI ? Newer model(s). These may use very fast LCDmasking technologies.Model size: ?Capital: $159000 @ Dec. 92SOMOS(EOS)(Teijin Seiki)The chemical giant du Pont developed a photo-polymer resin in conjunction with the SOMOSsystem. High hopes were expected of this butthey delayed before licensing the technologyout. They felt that the market was developedenough. The licensed technology is quite‘new’ and therefore an unknown. Theprocesses fully cures the resin by rasterscanning; however the model is later heated totoughen it.Model size: 12"×12"×12"Capital: ?
  18. 18. Page 18Table 1 ‘Currently Available Rapid Prototyping Machines’.2.4. COMPARISONSThe reader is by now aware of the complexity of the issues affecting the selection andperformance of a Rapid Prototyping system. The most comprehensive comparison carried outwas by the Chrysler Motor Corporation. It is possible to choose models and throughput ratesthat will cause any of the listed systems to win. In Chryslers case the deck was favouredCubitals Solider. If the Solider is ignored the table can be used to make some reservedcomparisons.Quadrax LaserTechnologies Inc.Mk 1000LMSThis US firm uses a photo-curing process. Thelayers are fully cured with a very high powervisible light sophisticated Raster Scanninglaser. In most Rapid Prototyping systems themodel lowers into the vat, etc. as new layersare added. In this system the model remainsstationary and the optics rise.Model size: 12"×12"×12"Capital: $195000 @ April 91Sony SCS The Sony and the Mitsubishi products are notknown about except for the fact that they areboth photo-curing processes.Mitsubishi ? see aboveCMET SOUP This is an unknown Japanese photo-curingsystem. There is the possibility that this couldbe the Sony or Mitsubishi products mentionedabove.DMEC SolidCreationSystemSee above (this probably the Sony systemSCS).
  19. 19. Page 193DSystems3DSystemsCubitalSolider5600DTM 2000 Stratasys3DModellerHelisysLOM1015Cost of Equipment (#) $210 000 $420 000 $490 000 $397 000 $182 000 $85 000Depreciation Cost / hr(5 yr. 85%)$5.24 $10.61 $13.16 $10.66 $4.89 $2.55Service Contract / yr. $36 000 $85 000 $49 000 $68 000 $7 000 $17 000Pre-processing Time(hr:min)00:34 00:34 00:21 00:35 04:20 00:46Build Time (hr:min) 05:06 04:44 09:26 03:00 08:00 09:51Post-processing Time(hr:min)01:45 01:45 01:00 01:19 00:15 00:25Total Process Time(hr:min)07:25 07:03 10:47 04:54 12:35 11:02Maintenance Cost /part$24.66 $54.03 $1.88 $27.40 $7.52 $22.49Pre-processing Cost $38.02 $38.02 $23.35 $38.69 $288.82 $51.36Build Cost lessAttendant$28.77 $53.40 $3.76 $31.99 $39.11 $22.49Post-processing Cost $38.50 $38.50 $22.00 $29.27 $5.50 $9.24Total Material Cost $4.00 $4.00 $31.43 $5.89 $4.00 $3.82Cost of AttendedOperation$0.00 $0.00 $6.29 $66.00 $0.00 $0.00Total Part Cost $133.95 $187.95 $88.71 $199.24 $344.95 $109.40# Prices 10/06/92 33 partstogetherTable 2 ‘Chryslers Rapid Prototyping Benchmark’.The most useful pieces of information are the timings and the maintenance and depreciationcosts that probably convert at the rate of $1 equals £1. It is immediately apparent that aninternal facility has very high overheads.2.5. THE BUREAUXThe Rapid Prototyping market is very young; with a low number of machines in the country.There are some machines used in internal facilities; but these subsidise themselves by alsoacting as bureaux. The known UK bureaux are listed in the following table in the authorsorder of preference:
  20. 20. Page 20Table 3 ‘UK Rapid Prototyping Bureaux’.Bureau Machine(s) DetailsFormationEngineeringServices3D SystemsSLA 250This firm offers very good service at acompetitive price. They offer the best value formoney pricing structure: it is related to themodel volume rather than the overall dimensionenvelope.They come recommended by Hewlett Packard.Rover Group 3D Systems(all sizes)The most extensive user of Rapid Prototypingwith 4 SLA machines running continuously.They quote from experience rather than aformula.SherbrookAutomotive(CubitalsSolider)They carry out the preparatory work and thensub-contract the Solider time from Schneider inGermany. If there is any re-assembly orreplication casting to be done then this is carriedout by Sherbrook. They quote by envelopevolume - at 93 prices per cubic centimetre:0 - 500 £350501 - 1000 £5751001 - 3000 £8503001 - 5000 £16755001 - 10000 £277510001 - 20000 £415020001 + £ P.O.A.Umak HelisysLOM 1015They charge £100 + £50 / hour exclusive ofVAT.In the past models requiring the LOM 2030 havebeen produced at Helisys facility in LosAngeles.RP&TConsortium(WarwickUniversity)HelisysLOM 2030RP&T is a collaboration with Rover Group.They have only just started.Rolls Royce 3D Systems ? Rolls Royce has purchased the technology andthey have a desire to sell machine time. Nodetails or contacts are known.
  21. 21. Page 213. TRIALSRapid Prototyping is a very impressive facility; but is it economically viable or even useful tothe Thorn Lighting Group? The only way to answer these questions is to have a look at somecosts and quotations.3.1. THE HISTORY OF MK 14 POP PACKA line of investigation was to consider the impact that Rapid Prototyping could have had onone of our most important products. There are two types of mouldings used in Pop Pack: thespine end caps, and the diffuser end caps. The development of the spine end caps shall nowbe considered. There are two of these: the single and the twin lamp holder versions. Theywere developed using single impression soft tooling. The history of this development issummarised in the following table:Table 4 ‘Popular Pack Spine End Cap History’.Quotations have not been sought for these components; but estimates can be made basedupon the Adagio arm. The later would cost £845 for the polymer model; therefore the twoPop Pack components should cost no more than £1200; they could cost less than £845! Theoriginal design had to be modified after visual appraisal and test assembly using theprototype. It shall be assumed that the original Rapid Prototyping model would also beincorrect, an that it cannot be modified. A new Rapid Prototype model is therefore produced -another £1200. The rework caused a delay in the completion of the component of over threemonths. The changes made are only minor; therefore the Rapid Prototyping approach wouldcause a delay of under a month. If the change to production tooling was made at this pointthere would have been a saving of at least £880 pounds. The contribution from eliminatingtwo months of delay is impossible to calculate.The most likely Rapid Prototyping approach would probably be more cautious - correctmaterial replicas would be produced for thermal and strength testing. The Adagio estimatewould indicate something like £1600 pounds for a short run of replication mouldings. Thismore cautious approach would make the Rapid Prototyping approach more expensive thanthe one; but this would be offset by all the time savings.Requirement Date PRNumberPriceSingle Impression Soft Tooling 11/01/92 117298 £2500.00Modification to the SoftTooling13/04/92 119834 £780.00250 Single and 250 TwinMouldings from the softtooling04/06/92 122669 £252.50
  22. 22. Page 223.2. THE SON PAKThe new Son Pak was to have a one piece polycarbonate moulding for its body. Quotationswere therefore sought for Rapid Prototyping both this and the front cover. The quotationswere obtained from several bureau services:Table 5 ‘Ian Thorniwells Son Pak Quotations’.The models are quoted for without any cost saving preparation, i.e. subdivision. The body ofthe Son Pak is not very volume efficient; it is also quite large. It is a shame that the Formationquote is for producing the model from drawings rather than a STL file because then the costwould be lower. The biggest surprise is the poor competitiveness of the LOM model. This isprobably due to the large model height of the Son Pak body.3.3. THE ADAGIO ARMHalf of the Adagio arm was used as a STL file transfer test. This component had been‘rapidly prototyped’ without using the specialist technology; it was therefore decided to seekquotations for comparison. The medium level of complexity in the component is visible in thefollowing plate:Bureau Quotation for Son PakFormation (SLA) £21922 weeks from two dimensionaldrawingsUmak (LOM) £2632£686= £33181 week (+£520 from twodimensional drawing)DTM £1600(6 off £7200)This is not a normal bureauquotation - the quotation is fromthe manufacturer. The price islow because this would be anexperimental collaboration.from STLSherbrook (Solider) £3910£785=£46952 weeks from STL
  23. 23. Page 23Plate 1 ‘The Adagio Arm (half)’.Two quotations were sought to compare the prices of two bureaux offering an identicalservice. These are then compared with the more conventional approach used. Thisinformation is represented in the following three tables.Table 6 ‘Rover Groups Quotation for the Adagio Arm’.Service Supplier CostStereolithographic Master.1 off of single half.Rover Group Ltd. £1112Vacuum Casting Mould1 off (produces single half)Rovers internal facility is overworked, ∴sub-contracted to ??10 off Urethane resinvacuum castingsas above ?
  24. 24. Page 24Table 7 ‘Formation Engineerings Quotation for the Adagio Arm’.Table 8 ‘Cost of the Two Halves of the Adagio Arm without Using Rapid Prototyping’.Why does Rapid Prototyping compare badly? The tapers that make the geometry complicatedwere ignored in the CNC model. This was acceptable for this application. The geometry couldtherefore be produced fairly cheaply using CNC techniques. Their price was neverthelesssurprisingly low and their methods should therefore be investigated if possible. It may be thatService Supplier CostStereolithographic Master.1 off of single half.Formation Engineering Services Ltd. £845(delivery 1week)Vacuum Casting Mould1 off (produces single half)Formation Engineering Services Ltd. £69010 off Urethane resinvacuum castingsas above 10 × £72= £720Service Supplier CostCNC approximate Master.1 off of each half.Aycliff Tool & Gauge,Unit 3, All Saints Industrial Estate,Shildon,County Durham. DL4 2JU(0388)776298 (fax)£350(delivery notknownPR126955)Vacuum Casting Mould1 off (produces both halves)A.T.O.M. (Industrial Model Makers) Ltd.Hope Works,High Street,Sunningdale,Ascot,Berkshire. SL5 0NG(0344)20001(0344)28028 (fax)£375(completion1 week)10 off Urethane resinvacuum castingsas above 10 × £50+ £100= £600(delivery 1week)
  25. 25. Page 25they are using the automatic profiling technology described in section “1.3.1. The SubtractiveAlternative”. The quotations reinforce the notion that Rapid Prototyping is best suited tocomponents of very high complexity.Replication casting is an important optional part of the Rapid Prototyping cycle. Thequotations supply evidence that this aspect of the service offered by the bureau services is notthe most competitive. Rovers in-house replication facility is over worked; they therefore havea list of replication casting sub-contractors. These are likely to be more competitive. If ThornLighting becomes involved in Rapid Prototyping it should compile its own list that is asexhaustive as possible.3.4. THE JUBILEE LINE EXTENSIONCost savings at the pre-production stage are not the only reasons to carry out RapidPrototyping: bid support is another. The largest potential project in Thorn Lighting at the timeof writing is the London Underground Jubilee Line Extension. The platform fitting hasalready been concept designed by London Underground. Thorn Lighting is bidding to proveand manufacture the fitting. To do this prototypes are required. This is a project with enoughfinancial impetus to act as a pilot project for the use of Rapid Prototyping.The question remains whether the technique is suitable for the components of this fitting. Thefitting consists of an extrusion and two end caps of similar cross-section. The extrusion is toolong to fit in any machine in one piece. It is also unlikely that it will be cost effective tomodel this even if the component is manufactured in identical replicated sections. This hasbeen quoted for anyway in case there is a lead-time problem with the competing soft tooledextrusion approach.The cross sections of all the parts restrict the quotations to the largest Rapid Prototypingmachines available. It would be a good idea to obtain a quotation for the end capsmanufacture on a LOM 2030 machine - this may be more competitive for these geometries.The deciding factor whether not the end caps are suitable for Rapid Prototyping is theirgeometric complexity - the situation may be the same as the Adagio arm.The quotations following are based upon the partial details available when the company firstreceived the London Underground assembly drawings:
  26. 26. Page 26Table 9 ‘Quotations for Jubilee Line Extension Platform Fittings’.Supplier Part Details CostRover Extrusion(3 off)SLA Polymer only quote £112242 End Caps(3 sets)SLA Polymer only quote £2518SherbrookAutomotiveExtrusion(for 3 off)Solider Polymer only - 1 off master forduplication casting (306 mm length sections)Duplication aluminium casting and reunionCompletion of polymer master: 2 weeksDuplication casting: +3 weeksThese quotations are provisional as onlypartial details were supplied.£3900£ ?2 End Caps(for 3 sets)1 off each end polymer masterDuplication aluminium casting (insufficientdetail)All prices exclusive of VAT and couriercharges @ cost from Germany.£3140?
  27. 27. Page 274. APPROACHESIn this section of the report the applications, implementation and the philosophy behind RapidPrototyping are considered.4.1. APPLICATIONSRapid Prototyping has so far been described as an alternative tool for use with currentpractices. The technique permits changes in practice that are elaborated upon in section“4.3.1. Concurrent Engineering”. There are also some unique capabilities that it offers.4.1.1. Freeform Styling and GeometryRapid Prototyping excels with complex geometries. This fact can be extrapolated to: ‘RapidPrototyping facilitates the production of geometries that would otherwise be too expensive todevelop’. The companys products geometries consist of straight lines, circles and slightlyrounded corners. The designs look ‘modern’, but the geometries are analogous to motor carsof early eighties. Cars of the nineties are taking on freeform geometries that give them asophisticated futuristic look. A good example of this is the Mazda car company: their mostextreme example being the Xedos 6 - it probably does not contain a single straight line or flatsurface on the exterior! Such influences will ultimately filter through to the lighting industry.There are two possible approaches to prototyping freeform geometries: clay craftsmen orRapid Prototyping techniques. The increase in the use of freeform geometries will probablybe the biggest medium term driving force behind Rapid Prototyping. The trickle down isfollowing the path of fashion conscious products. It probably started in the late eighties withthe personal consumer electronics industry5. In an environment of highly competitive marketsand rapid technological advancement, if one does not have a large technical edge over thecompetition then it is important to have an aesthetic one. There are parallels in the lightingmarket: the preference for low glare recessed fittings for general purpose areas. The choice isaesthetic rather than functional.4.1.1.1. ProstheticsThe freeform capabilities of Rapid Prototyping have been applied to the unique geometry thatis an individuals body. The geometry is ‘scanned’ into the system using either threedimensional digitising; CAT scans or NMR scanners. This has already been used for artificiallimb mounts and replacing a severed ear with a silicone replica of the remaining one6! Asuggested application is to use models to practise experimental brain surgery. Thesefascinating applications are of no interest to the Thorn Lighting Group.5 The glassware industry has always used free form geometries because of the nature of the material. The zenithof this styling is probably the perfumery industry.6 Naturally the geometry was produced in mirror image.
  28. 28. Page 284.1.2. Rapid ToolingRapid Prototyping has been described as a solution seeking the problem. There are pressuresthat will inevitably lead to the ‘revolution’, but they are not sufficiently developed yet. Theadvocates of Rapid Prototyping have therefore been looking for additional applications thatwill lead to market growth. The application that is mainstay of current research is RapidTooling. At the moment this application is nothing more that experimental; however if thisdelivers on its promises then it will have as large an impact on manufacturing as CNCmachining and robotics combined! The technology promises to produce production tooling inthe same time as Rapid Prototyping. The impact of this can be emphasised by an example: abrief is supplied for a simple moulded component; the design on CAD would only take a dayor so because of its simplicity. The tooling would be rapidly produced and production wouldbegin in under a week! The benefits of reduced time to market are extolled in section “4.3.1.Concurrent Engineering”.There are many avenues of Rapid Tooling that are under investigation. The main problemwith the technology at the moment is the surface finish. The surface finish on current RapidPrototyping models is not wholly acceptable. Current Rapid Tooling has an identical surfacefinish. The surface finish on tooling determines the surface finish on the productioncomponent; and a product surface finish equivalent to that of current Rapid Prototypingtherefore falls far short of the mark. In time the technology will become available. There ispresently no need for the technology; but the combined influences of competition andconsumerism will create the need as soon as technology is available.4.1.2.1. Currently Feasible TechniquesThe current surface finishes are suitable for some sand casting techniques. The reusablepatterns and core moulds are produced by Rapid Tooling techniques. The benefit is are thevery short lead times compared to the production of wooden patterns by craftsmen. Thedanger is that components made by sand casting tend to be large. This would make the RapidTooling model expensive. This can be alleviated by producing a hollowed tool that can befilled with a cheap packing material. This technique has been successfully used in theautomotive industry.Several processes offer one off investment casting modelling materials. This is presently notsuitable for one off production processes - only for producing one off metal prototypes.4.1.2.2. Processes Under DevelopmentSome of the techniques described below are a long way off. To be effective Rapid Toolingtechniques need to improve their surface finish by at least one order of magnitude. This willtake some time; but this problem is not fundamental and so success will ultimately beinevitable. It is presently not possible to say how long this process will take; a wild guesswould be 5 to 10 years to fully mature.
  29. 29. Page 29Sintering dies - Rapid Tooling polymer dies have been used to press powder components forsintering. The bound component is removed from the die and sintered in an oven. Theuse of plastic as a tool material limits the die pressure. In turn the low pressure limitsthe materials that can be pressed in preparation for sintering. The best results havebeen achieved with pure copper. Unfortunately there is not much demand for purecopper components; however it is ideal for single or multiple EDM electrodeproduction.One of investment casting - Rapid Tooling models can be made directly in investmentcasting material. These can be used for a single investment cast component. Thiswould be a very expensive method to use for production; however it could be used asan intermediate process, e.g. to investment cast an injection moulding die. Thistechnique is of interest to the Thorn Lighting Group. Such an application wouldrequire extremely high surface finishes - higher than that acceptable on a finishedproduct. This is a very big hurdle.One off ceramic core and shell production - this is almost identical to the last processregarding application. The direct production of ceramic shells is the same asinvestment casting with one of the stages already completed.The same technique can directly produce ceramic cores for use in another castingprocess. This application would be extremely rare.Investment casting mould production - Rapid Tooling could be used to produce mould fora run of investment casting wax positives.Laminated punch and die tooling - a metal film LOM structure is not particularly strong inmost respects. Its compressive strength perpendicular to the laminations is itsstrongest line of action. If loadings can be restricted to this direction then it can beused for limited tooling applications. The research carried out to date has used thematerial as a low pressure sheet material profile punch. The low pressure caveat limitsthe application to thin sheets of material that are not too tough. The tooling would bebetter at forming actions than punching and shearing actions.Such tooling would not be capable of punching fiddly features such as small diameterholes. This problem could be dealt with by using tool steel dowels for these punchparts. The dowels would be mounted in the full depth of the laminated tooling. Shearactions would result in a very high rate of tool wear that would limit the tooling tovery short production runs. This would not be the case for a purely compressiveforming application.Such tooling may be useful for other compressive die applications. For example, itmay make a better die than a polymer in the ‘Sintering dies’ application describedearlier. The sheet metal applications are of interest to the Thorn Lighting Group;especially regarding short run products.
  30. 30. Page 30EDM electrode manufacture - a problem with Rapid Tooling techniques is that they cannotdirectly produce tools of the toughest materials. Electrode Discharge Machining7 issuitable for producing the most complicated geometries in such materials usingcustom tooling. The electrodes are negatives of the surface to be produced and theytherefore have complex geometries. Such electrodes can be produced using RapidTooling techniques. This may be the ‘Sintering dies’ process or any one offproduction process.EDM can only achieve a low material removal rate and is therefore best suited tofinishing operations. The most rapid Rapid Tooling would therefore be produced byanother method with a lower surface finish. This would then be finished using EDMwith electrodes produced by Rapid Tooling Techniques. In the long term RapidTooling may reduce product life cycles to the extent that very hard tooling is no longerrequired.Direct metal component production - an expensive production process in which metalliccomponents are produced directly by a Rapid Prototyping process. This could possiblybe the cheapest technique for one off production of metal components with complexgeometries. There are questions over the material properties of such a component.This is not necessarily a limitation - the properties could end up being superior!There have been some exotic applications suggested for this: it is the most flexibletechnique for the applications described in section “5.3. Specialist Production”; it canalso be used for field repairs to reduce spares stocks. The suggested needs for this are:on an aircraft carrier and in a space station! Alternative Rapid Tooling techniquescould be used for these applications but they would require secondary processes.Direct metal tooling production - this is the same process as the preceding one except that itis used to produce tooling rather than one off components. This approach has muchwider applications and is of interest to the Thorn Lighting Group.4.2. RESOURCESThere are a number of implementation approaches available.4.2.1. In-houseThe current technologies require large capital expenditure and they result in high overheads.This approach is valid only if the company produces a high number of models. The internalfacility would give a company control over the process, especially regarding quality. Modelsproduced internally are several times cheaper than those made externally if the machine canbe fully utilised.7 This is also the case for ECM (Electrochemical Machining). This process achieves a higher surface finish thanEDM but is less flexible regarding geometry.
  31. 31. Page 31Most processes have a work in progress problem that is exacerbated if the facility is in-house.This problem is described in section “2.1.2.1. Packing the Machine”. It is this problem thatdrives up the cost of parts made externally.4.2.2. External BureauxThis is the obvious approach for a low volume user. The different Rapid Prototypingtechnologies have different specialisms; it can therefore be worthwhile for a higher volumeuser to continue to use bureaux so that they may switch technologies from project to project.A high volume user should also extensively ‘test drive’ the technologies before purchasingfor an in-house facility.4.2.3. The ‘Thorn Lighting Bureau’This is an extension of the in-house facility. This is commonly factored into the costjustification for in-house plant. The external work helps to raise the utilisation as well assupplying revenue. To use this in justifying the expenditure would be dangerous for the ThornLighting Group because of several reasons: everybody else tries to do it; we do not have sub-contract experience; and we have no expertise. The only successful implementation is theRover Group. It works precisely because they do not need to do it. Their corporate identity isalso a help. Following their example: external work should be the icing on the cake and notpart of the base.The only significant hole in the UK bureau market is for the DTM Sinterstation 2000machine. As a bureau machine it offers the largest opportunity to be ‘hyped up’ to attractpotential customers.4.2.4. CollaborationsThere are several collaborations that could be investigated. Some of these are research based;while others are ‘clubs’ with members rates; and others still will be bureaux by anothername.There are a couple of these that may be of interest to the Thorn Lighting Group: the RP&TConsortium looks interesting; and there is a joint project between the CAD/CAM Centre andthe Centre for Industrial Design. It is their intention to provide a Rapid Prototyping facility inthe North East but they have only just started. The Thorn Lighting Group has the opportunityto be a user or a supplier of this project.4.3. PHILOSOPHYFor ninety-nine geometries out of every hundred it is presently cheaper to produce a model bya means other than Rapid Prototyping. It could therefore be asked what future has it? Thebenefit is its rapidity; and the changes in the design and production cycles that can be madewith the availability of prototypes. A prototype model is a form of high fidelity and non
  32. 32. Page 32specialist communication - if a picture is worth a thousand words then a model is worth abook.4.3.1. Concurrent EngineeringThe influences of competition, customer demands and of rapid technological development,are all fuelling the need for reduced time to market. The Thorn Lighting Group has theexperience of the Type-E Ballast to reinforce this. Reduced time to market maximisesrevenue and also allows the product life cycle to be condensed. The benefit of the latter is notobvious. Imagine two competing companies: one that develops short life cycle productsrapidly; and another that develops longer life cycle products more slowly. The slowercompany shall be given the advantage of starting off with the technically superior product.The fast company can close up from behind by mimicry. The companies are now almostlevel. The slow company must develop its products in quantum leaps to maintain superiority -this is difficult and costly. The fast company can evolve their product in small steps - thephilosophy of continuous improvement. This type of development is easy and cheap8. Thefast company can ease ahead of the slower one. The slow company is now chasing but theycannot develop as quickly. The most likely coarse of events is that the slow company will fallbehind at an ever increasing rate. The slow company needs a miracle product to close the gaponce a few product generations are put between the companies. This scenario is the ongoinghistory of the Japanese car industry.The cornerstone of the fastest approach possible is the catch all ‘Concurrent Engineering’.This is easiest to describe in terms of what it is not. It is not a linear approach: concept design,detail design, testing, production engineering and finally production. Any delays accumulatein the linear approach; at the same time any down stream feedback is slow - a productionengineering problem could necessitate a concept design change that would make all theintervening work a waste of money and equivalent to one huge delay. The concurrentapproach involves work on all the stages at the same time. The idea is that the productionengineering problem would be realised early before any of the intervening stages is complete.The concurrent approach also causes the delays in each of stages to be in parallel rather thanend to end. A concurrent approach is only possible with rapid and fluent communicationbetween all the activities.Rapid Prototyping is a method of rapid and fluent communication above all else9. Itsapplication to this effect is described in the following sections.4.3.1.1. TestingTesting can reveal problems with a design. It is therefore desirable to carry out such testing asearly as is possible. The earliest possible testing can be carried out on prototypes that areproduced rapidly. The main problem areas in the testing of Thorn Lightings products arethermal and ingress testing. It is therefore for these tests that it would benefit the company touse Rapid Prototyping. The models should be produced from the ‘first draft’ designs rather8 The small changes mean that the designs can be ‘right first time’ and are therefore unlikely to suffer delays.This in turn stops cost from escalating.9 The exception is testing. In this the model is an inherent part of the process.
  33. 33. Page 33than later ones - resizing a reinforcing flange is unlikely to drastically effect the thermaltesting. The different aspects of the design can separately work through the cycle of design,model, test, design, model test, etc. These different aspects, e.g. a cover plate seal and a lampholder bracket can therefore be developed concurrently if it is possible to produce the models- which is where Rapid Prototyping steps in.There are some issues to remember when using Rapid Prototyping for testing. Namely, themodels are generally not made from production component materials. In cases when they arethe Rapid Prototyping form of the material will have slightly different properties to theproduction material10. Fortunately these discrepancies due to material differences areconsistent; even between different processes. The Rapid Prototyping material can bedescribed as:• Weaker• Less stiff• Less dense• Having a lower maximum service temperature• Less thermally conductiveTherefore testing with the model builds in a big safety factor. The biggest problem is themaximum service temperature and live testing with wound gear - the models could distort,melt or even burst into flames dependent upon the Rapid Prototyping process selected. Thesolution to the testing shortcomings is to replication cast in a closely matched material, or tochoose a process that produces a model in a closely matched material.4.3.1.2. Production and Standards EngineeringThe production engineering function currently works from two dimensional orthographicdrawings. These are currently produced later than a ‘first draft’ Rapid Prototyping modelwould be possible. Production engineers are more than capable of interpreting such drawings;but a model helps the communication process - they are more likely to spot a potentialproblem or a possible improvement on a model than they are on an orthographic drawing.4.3.1.3. AssemblyPrototypes allow mock assembly operations to be carried out. They also allow something thatit is not currently possible - design communication with the shop floor. There is no greaterexpertise on the assembly of the companys products than the combined experience availableon the factory floor. This wealth of knowledge is only just being tapped by the formation of10 The SLS process from DTM can produce polycarbonate models. A production component would be injectionmoulded. This would make the material equivalent to 100% sinter density; while it would also form flow linerelated stress. In contrast the Rapid Prototype model would have a 70-80% sinter density. This would make itweaker and less dense but more brittle. At the same time it would also reduce the components maximumoperational temperature.
  34. 34. Page 34Continuous Improvement teams; but these can only make a contribution after production hasstarted - a concurrent approach requires that their knowledge be available from the start. Thefactory floor would have no problem relating to a Rapid Prototyping model; the beauty ofsuch a model is that nobody in or outside the company has a problem relating to it.All standards testing that was not material dependent could be completed during thedevelopment cycle rather than afterwards.4.3.1.4. PackagingThis is developed very late in the process where it may cause a delay. Earlier access to RapidPrototyping model would allow the packaging to be finalised; hence eliminating anypossibility of delay.4.3.1.5. MarketingThere are several ways in which Rapid Prototyping is beneficial to the marketing department.Rapid Prototyping may be directly by the marketing function. They can use it for marketresearch by talking to the customers and the sales force. This body of knowledge is notcurrently used to the fullest.The company presently has a problem with market brief ‘changing’ during the developmentof a product. This can be due to the market position changing during the present longdevelopment period; though the more common problem is communication. The marketingpeople need to see a prototype to really relate to the design. It is at this stage that they maywant to change something. Presently this point is quite close to the potential completion ofthe design and therefore any changes effectively create long delays. This problem could besolved by showing the product manager a ‘first draft’ model. Minor adjustments after the‘first draft’ are not of interest to the product manager. If the product manager okayed a modelthen they could be held to that.4.3.2. Right First TimeRapid Prototyping is not about shaving a few days off the development cycle by providing analternative route to making a final design verification prototype. It is about ConcurrentEngineering and the Right First Time principle. Rapid Prototyping models are acommunication aide; and communication is the key to Right First Time.4.3.2.1. The Son PakThis project had some Rapid Prototyping quotations that are discussed in section “3.2. TheSon Pak”. These quotations were for a late design verification prototype. The history of thedevelopment can be summarised as:• 1 month to complete concept design.
  35. 35. Page 35• 7 months to complete detail design.• design review.The design review rejected the concept design - thus turning 7 months work into a 7 monthdelay. A ‘first draft’ model reflects the concept design. It is difficult to say how long it wouldtake to get from the concept design complete stage to the ‘first draft’ model stage - but itwould not have taken the 7 months. This would have shortened the delay caused by therejection in the design review. If the concept had been accepted then the design could still failat the testing stage. A model could have been tested - hence the next hurdle would have beeneliminated at the same time!4.3.2.2. Competitive DesignsDesigns can compete both internally and externally. First consider external competition -biding for a contract. The company believes in high technology bid support - it has developedthe Visualisation system for lighting schemes. A model is an essential aide to a bid; thereforea high technology model cannot fail to impress potential clients. Rapid Prototyping could beused to supply several designs for the same bid.The other potential area of competition is internal. Presently a brief is assigned to anindividual who comes up with ideas for the concept design. This limits the pool of ideas thedesign develops from. An alternative suggested to the author is that a brief be thrown open tointernal competition for the concept design by a deadline. The designs would be presentedand the individual who would progress the design would then be selected. They would thengo off and redo the concept design borrowing any useful ideas from the competing designs.This process would increase the pool of ideas several fold.A concept that has competed wins more acceptance. This is important for rapid development.An individual, say a product manager can have slight reservations about a design that will beapparent at a subconscious level. The single design will do, but they feel it could be improvedin some unknown way. The development of this design could be indecisive and subject topetty change in these circumstances. If a design competes and it is then selected, then in theeyes of the selector the design is the best - especially if it is developed to incorporate the bestaspects of the competition. Such a design cannot be changed much because most of thealternative ideas have already been presented and rejected.The internal competition approach can be implemented without Rapid Prototyping. It will bea long time in the future that the costs would be low enough to allow Rapid Prototyping to beused as a competitive internal presentation aide. The point is that it is important to winacceptance of the design from all the individuals involved. A model can be used after thecompetitive stage to win over any reservations. Access to a model would help any dissentingindividuals to constructively voice their subconscious reservations. The value of this lastpoint cannot be overlooked. The approach has a much greater likelihood of being ‘Right FirstTime’.
  36. 36. Page 365. THE FUTURE5.1. THE INTERFACEThe STL interchange format can only have a limited future because of the problems describedin section “2.1.2.2. STL Manipulation by the Specialist”. Probably the longest termdevelopment is by the Brunel University Consortium. The objective of this is to develop anintelligent converter between STEP and any form of proprietary Rapid Prototyping format,e.g. STL. Any manipulation required is carried out by the converter using the original STEPdata. This avoids the problems of using a more limited Rapid Prototyping format. Theintelligence of the converter would optimise the model, e.g. facet densities in the case ofSTL.Is this of any use to the Thorn Lighting Group? The STEP format is the long term future ofCAD. The company has two three dimensional CAD systems: ME30 and only recently, SolidDesigner. Neither of these use STEP; however Hewlett Packard is developing a STEPinterface for Solid Designer. This will be demonstrated late in this year. The most importantaspect of such a system is what it can do for Rapid Prototypings major limitation - surfacefinish. It would also be useful if it automatically generated supports if necessary; andautomatically packed a machine with multiple parts as efficiently as is possible. If thecompany feels that it needs to redirect any research to better suit its own needs, then it shouldjoin the appropriate consortia.5.2. PROCESSESThe future of Rapid Prototyping systems will split down two pathways that shall be referredto as ‘high end’ and ‘low end’ in this report. All the machines currently available are highend, i.e. expensive. These will develop to the high fidelity systems required for Rapid Toolingas described in section “4.1.2. Rapid Tooling”. The requirements for testing favour processesthat can model in the correct materials. Therefore the selective laser sintering process isprobably the process with the longest future. DTM is current working on partially sinteringceramics and metals in new machines. The high end of the market will also see theintroduction of spray metal deposition processes.The low end of the market is not yet available, but imminent. These are the desktop machinesthat become CAD terminal peripheries. This market was created by the US Ford MotorCompany when it claimed that they would equip every designers workstation throughoutFord with one of these systems, provided that they cost less than $30000. Ford have a verylarge number of workstations! Models produced on low end would not have good materialproperties but they would be cheap.The low end processes are generally referred to as 3D Printing. This name belongs to aprocess developed by MIT. It is used in the Soligen machine presently but it is expected thatit can be put to low end use. The name is unfortunate because it is much better suited to somealternative technologies. These are based on inkjet techniques: the model is sprayed down inlayers along with a support material. These shall be given the name ‘twin jet processes’
  37. 37. Page 37throughout the remainder of this report. The 3D Printing process by MIT is a more generalform of the process described in section “2.2.5. Selective Binding”.Low end processes lower the barriers to entry into Rapid Prototyping techniques. It is difficultto say how useful they are to the Thorn Lighting Group. The specifics of the products are notknown to the author; but the low end processes are likely to have the following traits:• Low end models will have material properties that are worse than high end processes.This point has a high degree of certainty.• Low end processes are likely to be capable of producing small components only. Itshould be remembered that the processes are aiming at desktop application. Asuccessful technique may be expanded to a larger machine in the longer term.• Low end does not necessarily mean a low quality finish. The machines may or maynot start with low quality finish to reduce costs. Ironically it is probably easier to raisethe quality of the low end processes than it is the various high end ones. Quality istherefore a complete unknown regarding low end processes.The new suppliers and technologies known to the author are summarised in the followingtable. This contains information on both high end and low end processes.Table 10 ‘New Rapid Prototyping Systems’.Supplier Product DetailsDTM NewmachinesCeramic and metallic modelling facilities.The models are selectively sintered to alow sinter density; then they are fired in apost processing operation to achieve fulldensity.The ceramics are coated with a materialthat selectively sinters more easily than apure ceramic.BPMTechnology(Incre Inc.)BPM (previously Perception Systems) isdeveloping a twin jet product. BPM standsfor Ballistic Particle Manufacture.Incre Inc. has a spray metal process thatuses technology licensed from BPM. Thisrepresents a large diversity of expertise onthe part of BPM.TexasInstrumentsProtoJet Twin jet process.Visual ImpactCorp.Sculptor Twin jet process.CarnegieMellon(Research) Spray metal techniques for Rapid Tooling.
  38. 38. Page 385.3. SPECIALIST PRODUCTIONRapid Prototypings freeform geometric capabilities give it a unique production capability. Itis capable of producing components that are impossible to manufacture any other way. Theapplications of this are only limited by ones imagination. Two broad groups of applicationsare apparent: articulation and structural. The articulation applications are sealed units withmoving parts, e.g. a high strength ball and socket joint. The structural applications are moreversatile; these will probably be used by the aerospace industry in the not too distant future. Itwill be possible to produce structural components with higher stiffness to weight ratios thanare currently possible. This will be achieved by producing shapes with extremely complexinternal geometries - three dimensional honeycomb and sponge like constructions. This is theconstruction that nature uses for the high stress areas in bones. For these applications thecomponent must be built directly in the required material because replication processes arenot feasible. Selective laser sintering would generally not be suitable - this application willmostly be the province of spray metal techniques.Such production applications are high cost, high performance. It is unlikely that the ThornLighting Group will need these capabilities.
  39. 39. Page 396. CONTACTSSupplier Contact Details3D Systems Inc. Ltd Andrew ChantrillUnit 7, The Progression Centre,Mark Road,Hemel Hempstead,Herts. HP2 7DW.(0442)66699(0442)234535 (fax)Richard Aubin of United Technologies (Pratt & Whitney).0101 203 727 1697He did not return my call regarding contactingthe Visual Impact Corporation.BPM Technology Box 8002,1110 Powdersville Road,Easley,SC 29640.0101 803 282 0033 They are 5 hours behind.They did not return my call.Bridgeport Machine Tools Jez Luing.(0533)531122(0533)539960 (fax)Brunel University Consortium Consists of:the university - Prof. A.J. Medland,CIMIO Ltd.,Formation Engineering Services Ltd.,Rolls Royce Ltd.,Metal Box Plc.,For contact see Prof. A.J. MedlandCalifornia Polytechnic StateUniversityFor contact see Mr Martin KochCarnegie Mellon Institute Len Weiss.Pittsburgh.CMET No details known.
  40. 40. Page 40CIMIO Ltd. Supplier of STEP integrated CAD facilities.Adrian Laud, Managing Director.Brunel Science Park,Coopers Hill Lane,Englefield Green,Surrey. TW20 0JZ(0784)438038(0784)472870 (fax)Cranfield Institute of Technology (0324)750111Cubital Ltd. Israel13 Hasanda St.(P.O.B. 2375),Industrial Zone North,Raanana, 43650Israel.010 972 52 906888010 972 52 919987 (fax)GermanyLiebigstrausse 3,6369 Nidderau-Heldenbergen,Germany.01049 6187 2203701049 6187 25155Dr P.M. Dickens (The most prolific UK academic on the subjectof Rapid Prototyping)Department of Manufacturing Engineering andOperations Management,University of Nottingham,University Park,Nottingham. NG7 2RD(0602)514063(0602)514000 (fax)DMEC No details known.
  41. 41. Page 41DTM Corporation Bureau services USAKent Nutt, Marketing Manager.161 Headway Circle,Building Two,Austin,Texas 78754.USA.0101 512 33929220101 512 3390634 (fax)GermanyKlauss J. Eβer01049 210352265 (fax)EOS GmbH Johann OberhoferPasingerstrasse 2,D-8033 Planegg bei Münich,Germany.01049 89 899131001049 89 8598402 (fax)Formation Engineering Services Ltd. Mr J.R. Andrzejewski, Systems Manager.Nigel Bethell (regarding materials etc.)Unit A3, Spinnaker House,Hempsted,Gloucester,Gloucestershire. GL2 6JA(0452)380336(0452)380497 (fax)Geoff Lart of ProtoMod Ltd.(0234)750875 (fax)For the phone number see Cranfield Institute ofTechnology.Helisys Inc. 2750 Oregon Court,Building M-10,Torrance,CA 90503.USA.0101 310 782 19490101 310 782 8280 (fax)
  42. 42. Page 42IMechE Seminar papers - Rachel ParkinsonLibrary - Millie FitzgeraldInter library loan - Miss Emily Lloyd(071)2227899(071)2228762 (Library fax)Incre Inc. Dave Gore, President.Corvallis,Oregon.Mr Martin Koch Research into Rapid ToolingIndustrial Engineering Department,California Polytechnic State University,San Luis Obispo,CA 93407.USA.Faxed response lost.Light Sculpting Inc. 4851 North Marlborough Drive,Milwaukee,WI 53217.USA.010 414 964 9860Massachusetts Institute of Technology 77 Massachusetts Avenue,Cambridge,MA 02139.USA.010 617 253 5381Prof. A.J. Medland of Brunel ConsortiumCentre for Geometric Modelling and Design,Department of Manufacturing and EngineeringSystems,Brunel University,Uxbridge,Midds. UB8 3PH(0895)274000 #2943(0895)812556 (fax)Dr Unny Menon Rapid Prototyping authority at CALPOL.For contact see Mr Martin KochMitsubishi No details known.Nottingham University For contact see Doc. P.M. Dickens
  43. 43. Page 43Quadrax Laser Technologies Inc. 300 High Point Avenue,Portsmouth,RI 02871.USA.010 401 683 6600Rolls Royce No details known.Rover Group Graham TromansStereolithography,Building 41,Fletchampstead Highway,Canley,Coventry. CV4 9DB(0203)874086(0203)874750 (fax)RP&T Consortium David Wimpenny,Lee Styger.Advanced Technology Centre,University of Warwick,Coventry. CV4 7AL(0203)523687(0203)523387 (fax)Schneider No details known.Sherbrook Automotive Ltd. Richard C. Smith, Sales Manager.Sherbrook House,Swan Mews,Lichfield,WS13 6TX(0543)257131(0543)263816 (fax)(0753)864898 (home base - phone/fax)Soligen Inc. Chick Lewis, Vice President.Northridge,California.Sony No details known.
  44. 44. Page 44Stratasys Inc. 14950 Martin Drive,Eden Prairie,MN 55344-2019.USA.0101 612 937 30000101 612 937 0070 (fax)Kevin Stubbs of Thorn Lighting Group3, King George Close,Eastern Avenue West,Romford,Essex. RM7 7PP(0708)730888(0708)727370 (fax)(0831)304715 (car)7-268-6252 (internal network)Teijin Seiki Co. Ltd. Kenichi IkariShinjuku NS Bldg.4-1, 2-Chome,Nishishinjuku,Shinjuku-ku,Tokyo. 163-08Japan.01081 3 3348 222701081 3 3348 1050 (fax)Texas Instruments Inc. Steve Penn, Project Manager.McKinney,Texas.Umak Bureau and sole UK agent to Helisys.P.H. Graham, Managing Director.BSA Business Park,Armoury Road,Birmingham,Midlands. B11 2RQ(021)766 8844(021)766 8998 (Fax)
  45. 45. Page 45Visual Impact Corporation George McKinney, Director.Windham,New Hampshire.International directory enquiries cannot locatethem.Warwick University For contacts please see RP&T ConsortiumTable 11 ‘Contacts’.
  46. 46. Page 467. RECOMMENDATIONSRapid Prototyping can either be used as part of a Concurrent Engineering strategy, or it can beused as a simple prototyping tool for some companies products. The best examples of thelatter are engine manifolds. There is no such application within the Thorn Lighting Group asis the case for most companies. There are tremendous opportunities however as part of aConcurrent Engineering strategy.7.1. THE SHORT TERMThe Thorn Lighting Group is not ready to take advantage of Rapid Prototyping. The companyhas a target development time that it should achieve by other means. Applying RapidPrototyping techniques now will not have sufficient benefit to justify the costs. Modelproduction time is not the limiting factor of the current system. The company must more fullydevelop its concurrent approach. When the company has achieved the current target it will beready to take advantage of Rapid Prototyping to halve the development time from the presenttarget!In the mean time it will be possible to apply Rapid Prototyping on a project by project basis.In order for this to be effective the designers must be aware of the issues described in section“2.1. Model Production”. The success rate of this application will be low - as testified by thequotations in section “3. Trials”. The most likely area for success in the short term is inCustom Products for large projects, such as the Jubilee Line Extension.The most important objective in the short term is spreading awareness of Rapid Prototypingthroughout the company.7.2. THE LONG TERMThe pressures that will drive the company to Rapid Prototyping are described in section“4.3.1. Concurrent Engineering”. Now is not necessarily the time to get on board, but it iscertainly the time to try to develop the companys Concurrent Engineering techniques inpreparation. ‘Come the revolution’ the company does not want to be a slow one in a fastmoving world. Before this the company should try to maximise its current resources of CADvisualisation and concept drawings. As soon as the company does this Rapid Prototyping willdrift in as long as people are aware of it.The Thorn Lighting Group is striving to be a World Class company. At this time RapidPrototyping is a technology that is above World Class. In a short time it will descend to aWorld Class technology. This is the point when the Group should be ready to take up thetechnology seriously. In the more distant future Rapid Prototyping could become a necessityfor survival.The best scenario is for the company to develop its concurrent approach over the next twoyears. If this was successfully completed then the timing to buy a machine would be perfect.The low end market should have developed; while the first metal capability machine from
  47. 47. Page 47DTM would be available - sole UK user of this would represent a very interesting bureauopportunity. Investment in plant before the company has met its current target, even in twoyears time, would be a mistake.
  48. 48. Page 488. CONCLUSIONSThe most general conclusions are to be found in the reports recommendations. The mostimmediate point is that there is a need for people to be aware of this new technology. Thereader is directed towards section “1.3. What is Rapid Prototyping?” for a general description.Designers should be aware of the issues raised in section “2.1. Model Production” while themanagement needs a perspective on sections “4. Approaches” and “5. The Future”. The restof the report is reference material.It is felt that the report has been successful in all its objectives. It had been hoped that morecould be done in the way of concrete financial justification, but the company has not recordedthe information that would be required. It may be possible to analyse some future projects, butpeople are defensive about the type of information required.In summary it can be concluded that this exercise was worthwhile. Rapid Prototyping is atechnology that the company needs to be aware of, and that in all likelihood will play a part inits World Class future.Document Reference:Filename: RP2.DOCPrinted on: 19/03/13
  49. 49. Page 49INDEXFIGURES1. ‘Free Hand Sketch of a Non 3 Axis Geometry’.................................................................62. ‘Lamina Model Construction’............................................................................................73. ‘Stacking in a Rapid Prototyping Machine’.......................................................................10TABLES1. ‘Currently Available Rapid Prototyping Machines’. .........................................................192. ‘Chryslers Rapid Prototyping Benchmark’. ......................................................................203. ‘UK Rapid Prototyping Bureaux’. .....................................................................................214. ‘Popular Pack Spine End Cap History’..............................................................................225. ‘Ian Thorniwells Son Pak Quotations’..............................................................................236. ‘Rover Groups Quotation for the Adagio Arm’. ...............................................................247. ‘Formation Engineerings Quotation for the Adagio Arm’................................................258. ‘Cost of the Two Halves of the Adagio Arm without Using Rapid Prototyping’..............259. ‘Quotations for Jubilee Line Extension Platform Fittings’................................................2710. ‘New Rapid Prototyping Systems’...................................................................................4011. ‘Contacts’.........................................................................................................................46PLATES1. ‘The Adagio Arm (half)’....................................................................................................24
  50. 50. Page 50GENERAL INDEX33D Printing............................................383D Systems .........................11, 17, 21, 41SLA Machines...............17, 21, 23, 27AAdagio Arm ..................22, 23, 24, 25, 26Aircraft Carrier......................................31BBallistic Particle Manufacture...............40BPM Technology............................40, 41Bridgeport .........................................6, 41Brunel University Consortium........38, 41CCalifornia Polytechnic StateUniversity..........................................41Carnegie Mellon....................................41Chrysler Motor Corporation............19, 20Ciba-Geigy............................................17CIMIO Ltd. ...........................................42CMET .............................................19, 41CNC Machining..........................5, 25, 29Coca Kola................................................6Competitive Designs.............................36Concurrent Engineering 28, 29, 33, 35, 47Cranfield Institute of Technology.........42Cubital.................................17, 19, 21, 42Curved detail.........................................10DDMEC.............................................19, 42DTM..............................18, 23, 38, 40, 43du Pont ..................................................18EElectrode Discharge Machining(EDM) .........................................30, 31EOS.................................................18, 43FField Repairs.........................................31Ford Motor Company ...........................38Formation Engineering Services21, 23, 25, 35, 43Freeform Geometry.........................28, 40Fused Deposition Modelling.................17GGeometry.....5, 6, 8, 11, 12, 13, 15, 25, 28HHeight..............................................10, 11Helisys.......................................18, 21, 43Hewlett Packard........................13, 21, 38IIMechE..................................................44Incre Inc. .........................................40, 44JJubilee Line Extension..............26, 27, 47LLaminated Object Manufacture ............23Laminated Object Manufacture(LOM) .................15, 18, 21, 23, 26, 30Light Sculpting Inc..........................18, 44MMassachusetts Institute ofTechnology............................18, 38, 44Material Properties........14, 15, 31, 38, 39Mazda....................................................28ME30 ....................................................38Mitsubishi .......................................19, 44
  51. 51. Page 51NNottingham University..........................44OOrientation ........................................9, 11Overhangs ...............................................9PPost Curing............................................14Prosthetics.............................................28ProtoJet .................................................40QQuadrax Laser Technologies Inc.....19, 45RRenault....................................................6Rolls Royce.....................................21, 45Rover Group............21, 24, 26, 27, 32, 45RP&T Consortium ....................21, 32, 45SSchneider.........................................21, 45SCS .......................................................19Sculptor.................................................40Selective Laser Sintering (SLS)14, 15, 16, 18, 38, 40Sherbrook Automotive........21, 23, 27, 45Solid Creation System...........................19Solid Designer.......................................38Solider...........................17, 19, 21, 23, 27Soligen ......................................18, 38, 45SOMOS.................................................18Son Pak ...........................................23, 36Sony ................................................19, 45SOUP ....................................................19Space Station.........................................31Spray Metal Techniques..................38, 40STEP .....................................................38Stereolithography..................................13STL File Format............11, 12, 13, 23, 38Stratasys ..........................................17, 45Surface Finish .......................7, 12, 29, 38TTeijin Seiki......................................18, 46Testing ....................22, 33, 34, 35, 36, 38Texas Instruments...........................40, 46Twin jet processes...........................39, 40Type-E Ballast ......................................33UUmak.........................................21, 23, 46VVisual Impact Corporation..............40, 46WWarwick University........................21, 46XXedos 6 .................................................28

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