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Turbo-Finish Technical White Paper

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    Turbo-Finish Technical White Paper Turbo-Finish Technical White Paper Document Transcript

    • Society of Manufacturing Engineers3rd INTERNATIONAL Machining & Grinding Conference [CONFERENCE & TABLE-TOP EXHIBITS]OCT. 4-7, 1999, Westin Hotel, Cincinnati, OHTECHNICAL PAPERTITLE: Turbo-Abrasive Machining and Turbo-Polishing in the Continuous Flow Manufacturing Environment.AUTHORS: Dr. Michael L. Massarsky David A. Davidson Turbo-Finish of America, Inc. 44 Kearsarge Street Bartlett, New Hampshire 03812-0248 (T) 603.374.2341 (F) 603.374.2366 (e) michael@turbofinish.com (e2) ddavidson@mgnh.dyndns.org (i)www.turbofinish.comINDEX TERMS: Non-traditional Grinding Non-traditional Machining Super-Polishing Deburring Edge Contour Surface Finishing Loose Abrasive Edge Finishing Super-Finishing Surface ConditioningABSTRACT: Turbo-Abrasive Machining and Turbo-Polishing are loose abrasive processes that can develop functionally important edge and surface effects on rotating and non-rotating components. The processes are characterized by rapid cycle times, single-piece as opposed to batch processing, and minimization or elimination of troublesome effluent steams. The processes facilitate automation of burr removal as well as edge and surface conditioning of components with complex geometries that present serious challenges to conventional mechanical finishing methods. This paper outlines process characteristics and mechanics of both processes, and discusses their application within the context of enhancing manufacturing flow in the post-machining areas of deburring and edge/surface final finish.
    • Deburring and surface finishing; still an industry challenge. Deburring and surface conditioning complex machinedand turned parts is one of the most troublesome problems faced by the metalworking industry. In many cases, parts with complex geometric forms which are manufactured with very sophisticated computer controlled equipment are deburred, edge finished and surface conditioned with manual or hand held power tools. This labor-intensive manual handling often has a considerable negative impact on manufacturing process flow, productivity and uniformity of features on the final product, as well as part-to-part and lot-to-lot uniformity. It has been a long- standing industry-wide paradox that the final surface conditioning operations utilized on many types of precision parts have nowhere near the level of sophistication of the preceding machining operations. Conventional mechanical finishing methods and unmet challenges. Mass finishing techniques such as barrel and vibratory finishing have long been recognized as the primary tools for metal part deburring and surface conditioning, and as such, have wide application throughout industry. As metalworking techniques have evolved in recent years, it seems that an increasing number of parts require more sophisticated deburring and surface conditioning methods. Many parts routinely manufactured now have size and shape considerations that preclude the use of conventional mass media finishing techniques. Additionally, manufacturers of high value parts now prefer manufacturing methodologies in which parts are processed singly and continuously rather than in batches, obviating the possibility that large numbers of parts will be scrapped or reworked due to human error or process maladjustment. Another important consideration in evaluating current mass finishing processes is their wet waste effluent stream; the treatment cost of which often approaches the cost of the actualTURBO-ABRASIVE MACHINING CENTER - deburring or surface conditioning operations themselves. IndustryEdge Finishing on turbine and compressor disks has long had strong incentive to seek out mass finishing methodsis performed by a combination of high-speed part that could achieve surface finish objectives in a dry abrasiverotation and a granular abrasive fluidized bed. operation. In contrast with current methods, “TAM” operations are completely dry, and produce surface effects rapidly, insingle part operations. (Some parts lend themselves to multiple spindle or multiple fixture operations when single partprocessing is not an important quality control objective).TAM combines mechanical finishing simplicity with machining-like sophistication. The “TAM” method providesmanufacturers with the ability to utilize a high-speed precision final machining and finishing method that canaccommodate the current trend toward continuous processing of individual parts. Many larger and more complexrotationally oriented parts, which pose a severe challenge for conventional mechanical finishing methods, can easily be processed. Many types of non-rotating parts can also be processed by fixturing them on disk like fixtures. Increasingly complex parts are being fashioned in today’s four and five axis turning and machining centers and “TAM” technology provides the method in which needed surface improvements can be made on these types of parts with a minimum of direct labor and tooling costs. “TAM” as a surface conditioning method is a blend of current machining and surface finishing technologies. Like machining processes, the energy used to remove material from the part is concentrated in the part itself, not the abrasive material interfacing with part surfaces. Like many surface-finishing processes, material removal is not accomplished by a cutting tool with a single point of contact, but by complete envelopment of the exterior areas of the part with abrasive materials. 2
    • Consequently, deburring, edge finishing, surface blending and smoothing and surface conditioning are performed on all features of the part identically and simultaneously. Many metal parts that are machined by being held in rotational work-holding devices (for example: chucks, between centers, rotary tables, etc.) are potential candidates for “TAM” processes. In many cases these final deburring and surface conditioning operations can be performed in minutes if not seconds. TURBO-ABRASIVE MACHINING CONCEPT. The basic concept underlying TAM operations is the placement of a rotating or oscillating metal component or work piece in a low-speed air- abrasive stream (fluidized bed) that is contained by a specially designed chamber. Surface finishes and effects can be generated on theentire exterior of complex parts, and specially fixtured non-rotational components. (Simple interior channels on someparts can also be processed). Various surface finish effects can be obtained by controlling variables of the process suchas rotational part speed, part positioning, cycle times, abrasive particle size and characteristics and others. Additionalsurface effects can be developed by utilizing processes that make use of sequential abrasive and/or polishing mediacombinations. Several machine designs have beendeveloped which can accommodate parts as small as 2-3inches (50mm) in diameter to very large and cumbersomerotational parts up to four feet (1200mm) in diameter andlarger. High intensity abrasive effect. Surface finish effects aregenerated by the high peripheral speed of rotating partsand the large number and intensity of abrasive particle topart surface contacts or impacts in a given unit of time(200-500 per mm2/sec. or 129, 000 to 323,000 per in-2/sec.) These factors make this equipment capable ofgenerating one of the highest rates of metal removal tobe found in any type of free abrasive surface finishing -operation today. Yet, with proper media selection andprocess adjustments, very refined finishes can be achieved.Parts with an initial surface roughness profile of 2-5 µmRa (80 - 200 µinch Ra) have been reduced to 0.2-0.4 µmRa (7-15 µinch Ra) in single operation in time cycles of only a few minutes. It should be noted, that surface finish effects developed from this process depart significantly from those obtained from air or wheel blasting. TAM processes can produce much more refined surfaces by virtue of the fact that the rotational movement of parts processed develop a very fine finish pattern and a much more level surface profile than is possible from pressure and impact methods. Random finish pattern vs. linear grinding patterns. Another very important functional aspect of TAM technology is its ability to develop needed surface finishes in a low temperature operation, (in contrast with conventional wheel and belt grinding methods), with no phase or structural changes in the surface layer of the metal. A further feature of the 3
    • process is that it produces a more random pattern of surface tracks than the linear abrasive methods such as wheel grinding or belt grinding. The non-linear finish pattern that results often enhances the surface in such a way as to make it much more receptive as a bonding substrate for subsequent coating and even plating operations. Metal improvement and peening. TAM processes have strong application on certain types of parts, which have critical metal surface improvement requirements of a functional nature. Significant metal improvement has been realized in processes developed with both abrasive and non-abrasive media material. Because of the intense nature of media particle contact with exposed features, it has been observed that residual compressive stresses of up to 400-600 MPa can be created in selected critical areas. Tests performed on rotating parts for the aerospace industry that were processed with this method demonstrated a 40%-200% increase in metal fatigue resistance when tested under working conditions, when compared with parts which had been deburred and edge finished with lessFigure 1 - Electronic Microscope photo of sophisticated manual treatment protocols.TAM abrasive tracks at 400X The Physics of Turbo-Abrasive Finishing ProcessIn turbo-abrasive machining, while the part is rotating in a fluidized bed of abrasive grain, the part surfaces aresubjected to a microimpact effect, which develops from high-speed collision and interaction of abrasive grain and partsurfaces themselves. It has been proven that metal removal intensity in TAM machining greatly depends on a partsrotational speed. High rotational speeds (RPM=1000-5000) and small area of abrasive grain contact cause metalstress exceeding the Gf fluidity limit. Owing to this, a surface plastic deformation takes place, while exceeding metalfatigue strength limit leads to micro cutting itself. These results have been confirmed by an electronic scan microscopestudy of mark tracks on polished part samples (Fig.1). The above mentioned mark tracks have confirmed that a surfaceformation is accompanied by the physical processes of micro cutting with prevailing plastic deformation of the metal FIGURE 2 Metal removal dependence on part orientation angle in fluidized bed 2.8 2.4 2Qm, micron/min 1.6 1.2 0.8 0.4 0 30 45 60 75 90 degrees 2 3 1 Brass Bronze Steel 4
    • surface. During repeated collisions of abrasive grains and plastically altered metal, the latter is either subjected to micro cutting for the second time, or is recurrently altered and then refined as a result of mass interaction of abrasive grain with the material being machined. Depending on abrasive material and its shape either abrasive cutting or plastic deformation takes place in the finishing process; or both processes may work together. For example, micro cutting process prevails with silicon carbide abrasive media, while plastic deformation of thin metal layers is a result of treatment by electric corundum or zirconium corundum abrasive grain. [Ed. Note: Turbo-Abrasive Machined surfaces are characterized by a randomly oriented pattern of abrasive tracks. Although the abrasive materials utilized in TAM are similar to the material utilized in conventional pressure blast processes, the nature of abrasive media/part surface contact is quite different, as is the nature of the resulting surface effects. Blasting is a very directionalized process where media contact is almost entirely of a perpendicular nature. The primary surface effect is generated by the overlap of high-speed impact craters in the part surface. In TAM the primary abrasive to surface contact is of a rolling or linear nature caused by the rotational movement of the part. This rolling, linear method of contact produces micro-abrasive tracks with raised edges or ridges on the longitudinal edge of the track. The plastic deformation referred to above is a reference to the developing of; and then removal of these raised edges by subsequent abrasive contact. TAM surfaces are created by an iterative process in which these raisedFigure 3 – TAM edge finish effects and edge exposed micro-edges or ridges are continuously beingorientation in relation to vector. created and then removed.] The rising airflow presses pulsating abrasive particles onto the surface being treated/machined with a normal force Py and abrasively scores it in the depth h. The relation between normal force Py and abrasive track depth h can be shown as h = bPyn [1], FIGURE 4 Radius rounding off (edges) Rz, Rx and Ry dependence on abrasive grain size Dg and different RPM 1. Dg - 80, 2. Dg - 46, 3. Dg - 30 mech 0.024 Rz Rx 0.048 0.036 0.016 0.024 0.008 0.012 0 0 1000 1500 2000 RPM 1000 1500 2000 RPM 1 2 3 1 2 3 Ry 0.08 0.064 0.048 0.032 0.016 0 1000 1500 2000 RPM 1 2 3 5
    • where b and n are plasticity constants, experimentally determined for different materials. Part rotation creates tangential force Pz. (Tangential force Pz is a result of a part rotation). Taking into account the fact that abrasive grain in the fluidized bed (besides mostly having a vertically oriented circulation) travels intensively in a pulsating manner, reminiscent of the Brownian type of movement. One can come to a conclusion that the surface being machined is undergoing (or is subjected to) particle collision impact ranging from 0 up to 90 degrees. Along with this, part of the abrasive media (besides the cutting and sliding processes), while rotating on the surface, creates substantial rotating moment, which causes micro-layer of metal to be plasticized by the abrasive grains’ cutting edges.Figure 5 - Uniform edge contour effects produced by TAM in 3-4 The most efficient interaction isminutes of machine time, replace multi-hour manual procedures. determined by the correlation of forces Py / Pz, which depends on the physicaland mechanical properties of the metal being treated, as well as abrasive properties of the media and grain sharpness.Here, kinetic energy of abrasive grain would be most fully used at an angle of approximately α=45°, when the °tangential and the normal components of a cutting force have the highest values.The above mentioned facts have been proven experimentally for steel and brass materials, where the maximum intensityof metal removal process is achieved at the angles of α=30–60° ( SEE Fig 2 ABOVE). °Special experiments have shown that the most intensive metal removal takes place when a part speed vector doesn’tcoincide in its direction with a part’s longitudinal roughness; otherwise, due to the polydispersion of the fluidized bed, theabrasive grain not only works on the peaks of micro surface roughness, but also in their cavities.After having being treated by TAM a surface has an unoriented or random microrelief, consisting of a large number ofshort scratches or abrasive tracks. This gives the surface high adhesion properties as a substrate, allowing for strongbonding with different types of coating, such as plasmatic, galvanic, lacquer polishing, etc. As one can see, extensive research shows that the metal removal process in TAM can involve the following: - micro-cutting; - micro plastic deformation; - residual fatigue removal of metal. The outcome of the above described interaction between the abrasive grain and the surface being treated has become a foundation for developing processes and designing industrial equipment for TAM of complex part surfaces, as well as for the processes of deburring, rounding off sharp edges and preparation for different coatings. Automated Deburring and Edge Contouring of Complex Rotating PartsFigure 6 - Radius effects produced both broachslot and counter-bore features of turbine disk Extensive experimentation has shown that TAM process is one of the most technologically advanced methods to beused for automation of deburring processes and rounding off sharp edges. At the present time many of these operationsare performed by conventional methods, requiring significant use of skilled manual labor (for example, in theaerospace industry). 6
    • A study of the interaction between abrasive grain and differently oriented part edges was conducted both on turbineand compressor disks. In order to evaluate the uniformity of the TAM process, the radii of part edges coinciding with the direction of coordinate axes have been controlled: (refer to Fig 3 diagram above). - Axis X is parallel to disk rotational spin; - Axis Y is parallel to radius direction; - Axis Z is parallel to speed vector. The part edges positioned at an angle of α=30-90° in relation to ° part vector Vsp are rounded off more intensively than edges parallel to Vsp. For example, titanium alloy disks after having been treated with zirconium corundum grain [ZA – 1548 /36] Figure 7 - TAM processes have removed burrs and radiused mesh during four minutes at RPM - features, including difficult to access slot areas on this titanium disk 1800 reached the following values:- Rx = .018 - .025 (rounding off radius on edge x [Rx], parallel to part spin axis).- Ry = .025 - .045 (edge Y parallel to part radius).- As Rz = . 007 - . 01 (edge Z parallel to vector Vsp).The same radii values were obtained on heat-resistant nickel alloy disks, as well as stainless steel disks.The grain size influence on the radius of rounding off edges is demonstrated on figure 4.Increasing the abrasive grain size from 80 mesh to 30 mesh causes Rx and Ry to grow 2.2 – 2.8 times. The followingvalues were received while abrasive grain size 30 mesh was being used, at RPM = 2000:- Rz = .02 - .03, Rx and Ry = .05 - .06This effect of grain influence is connected with the fact that the impact energy of grain and the surface being machinedis proportional to the mass of abrasive grain (i.e., ~Dg, where Dg is an average grain size). Radius formation process onnickel turbine disks being treated with TAM is demonstrated in Figure 5.Figure 6 presents test results, which were achieved at the Turbo-Finish Lab Center in cooperation with UnitedTechnologies. Here, one can clearly see the radius formed after a nickel alloy turbine disk has been treated with TAMprocess. Geometric parameter measurements have shown that the process does not push the part out of tolerance.Therefore, this is one of the definite advantages of TAM process where controlling technological parameters allows forregulation of disk edge radius within tolerance limits.Figure 7 illustrates post TAM radius formation on a turbine disk made of titanium alloy. Thus, the turbo abrasivetechnology can be successfully applied to treat metals with different physical-mechanical and physical-chemicalproperties. Solid, fragile and those of high plasticity materials can be machined and finished equally well with the turboabrasive process. 7
    • Summary: TAM processes can be easily justified in many types of applications where part size and shapeconsiderations make applying other surface and edge conditioning technologies difficult. The processdeburrs and develops needed edge and surface finish requirements very rapidly in an entirely dry abrasiveenvironment. In contrast with other technologies that utilize single point of contact cutting methods, TAM’scombination of complete abrasive envelopment and rotational motion give each feature in a given symmetryof rotating parts identical and simultaneous processing. When used as a final machining or conditioningmethod exceptional feature-to-feature uniformity can be developed..Significant TAM process characteristics: (1) Very rapid process cycle times, well suited for single piece continuous flow operations. (2) High intensity, small media operation allows for access into intricate part geometries (3) Completely dry abrasive operation creates both edge and surface finish effects. (4) Metal improvement and peening effects are possible for increased metal fatigue resistance. (5) No part on part contact (6) Modest tooling requirements. (7) Primarily an external surface preparation method, though some simpler interior channels can also be processed (8) Many types of symmetrical rotating components can be processed; non-rotational components can be processed also when attached to disk like fixtures. (9) Very refined surface and edge effects can be developed in multi-step processes that utilize successively finer abrasive materials sequentially. 8
    • Turbo-Polishing Turbo-Polishing is a term coined by the authors to describe a group of processes which has been developed to produce super-polish and super-finish surfaces on critical hardware. Like TAM processes, these processes utilize free abrasive material and rotational motion to produce specific edge and surface effects. Unlike TAM processes, parts are processed in a non-fixtured random media environment. The method is useful as a single-piece continuous flow style of final surface machining in that: (1)the parts are isolated within their own processing chamber, with multiple part processing possible inmachinery equipped with multiple chambers, (2) relatively rapid cycle times make it possible toaccommodate cellular and flow-line production. The method utilizes both high- pressure centrifugal and reciprocating motion to produce significant improvement in part surfaces that have demanding surface texture and surface integrity requirements. It is possible to produce functionally valuable surfaces by subjecting critical hardware to a multi-step process in which a series of successively finer abrasive materials are used in sequence. These processes are a variant of batch processes originallydeveloped to produce very refined “near-buff” surface finishes on a variety of consumer articles requiringhighly reflective surfaces for aesthetic reasons. Previously, most of these smaller parts required manualbuffing to produce the high-quality cosmetic or decorative surface finishes required. Although, notimmediately appreciated, the development of this technology also enabled the development of anautomated, uniform and consistent method for producing very low Ra surfaces. Sequentially finer abrasivesteps, using this method, can produce exceptional surface quality with even with the very high Rainitial surface condition common to castings, forgings and coarsely machined parts. Orbital Pressure Finishing Principles Based on “ferris wheel” physics, four processing chambers are located in opposing positions at the periphery of a rotating turret. Barrels rotate in the opposite direction of the turret rotation, combining a vigorous sliding motion of loose abrasive with the high-pressure contact of media and parts generated from the centrifugal forces of the turret spin. An additional reciprocating movement can be added to this mix, by deliberately mounting the processing chambers at an angle from the horizontal. This added reciprocating movement is useful for developing special edge and surface effects in a number of applications. The high centrifugal forces and high-speed reciprocating slide zones make it practical to develop super-polished and super-finished surfaces that would be impractical with other methods because of the extensive timecycles that would be involved. As the entire part exterior is subjected to the same abrasive, polish orburnishing protocol, it is possible to produce a much more uniform surface on the overall part than is possible 9
    • with single point of contact methods such as hand-held grinding or belt, buff or polish methods. Once process parameters have been established it is also possible to achieve a part-to-part and lot-to-lot consistency of result not possible where manual abrasive methods are utilized. Both TAM and Turbo-polishing are useful tools in developing specific surfaces where important surface texture and surface integrity requirements are an issue for the functionality of critical hardware. An example of this would be the super-polishing or super- finishing of turbine blade foil surfaces. This photograph was taken with an electron microscope at 500x magnification. It shows the surface of a raw unfinished “as cast” turbine blade. The rough initial surface finish as measured by profilometer was in the 75 – 90 Ra (µin.) As is typical of most cast, ground, turned, milled, EDM and forged surfaces this surface shows a positive Rsk [Rsk – skewness – the measure of surface symmetry about the mean line of a profilometer graph. Unfinished parts usually display a heavy concentration of surface peaks above this mean line, generally considered to be an undesirable surface finish characteristic from a functional viewpoint.] This SEM photomicrograph (500X magnification) was taken after processing the same turbine blade in a multi-step procedure utilizing orbital pressure methods with both grinding and polishing free abrasive materials in sequence. The surface profile has been reduced from the original 75 – 90 Ra (µin.) to the 5-9 Ra (µin.) range. Additionally, there has been a plateauing of the foil surface, and the resultant smoother surface manifests a negative skew (Rsk) instead of a positive skew. This type of surface is considered to be very “functional” in both the fluid and aerodynamic sense. The smooth, less turbulent flow created by this type of super-polished surface is preferred in most aerodynamic applications. Another important consideration the photomicrographs indicate is that surface and sub-surface fractures seem to have been removed. Observations with backscatter emission with a scanning electron microscope (SEM) gave no indication of residual fractures. Profilometer tape readings on this and other parts are shown in the APPENDIXBefore and after examples of turbine blade super-polishing using amulti-step recipro-orbital pressure method 10
    • REFERENCES: 1. Dr. M. L. Massarsky and D. A. Davidson, “Turbo-Abrasive Machining Theory and Application,” SME Technical Paper MR95-271, Proceedings of the 1st International Machining & Grinding Conference; Society of Manufacturing Engineers, Dearborn, MI, Sept. 12-14, 1995 2. Dr. M. L. Massarsky and D. A. Davidson, “Turbo-Abrasive Finishing,” SME Technical Paper, Proceedings of the Deburring and Surface Conditioning Symposium; Society of Manufacturing Engineers; Dearborn, MI.; Oct. 26-27, 1993 3. Massarsky, M. L., Davidson, D. A. “Turbo-Abrasive Machining and Finishing”, METAL FINISHING, White Plains, NY: Elsevier Science, p. 29-31, July, 1997 4. Massarsky, M. L., Davidson, D. A. “Turbo-Abrasive Machining – Dry Process Mechanical Finishing for Today’s Complex Components”, FINISHER’S MANAGEMENT, August 1997 5. “Dry Mechanical Finishing for Rotating Components”, SURFACE ENGINEERING, England: Institute of Metals, p. 363-364, 1997, Vol 13, No. 5 6. Massarsky, M.L., The Peculiarities of Part Treatment in Fluidized Bed of Abrasive Grains. - In collection "Progressivnye methody of obrabotki detalej". - LDNTP, [Russian],1977, p.79-84. 7. Massarskiy M.L., Guzel V.Z., Surface Quality at a New Method of Part Treatment is Turbo- Abrasive Grinding. - In collection "Physika i Tchnologia Uprochenia Poverchnosti Metalla". - Materials of seminar, L., Physicotechnical Institute named after A. F. Joffe, [Russian]1984, p.69-70. 8. Kremen Z.I., Massarskiy M.L., Turbo-Abrasive Grinding of Parts is a New Method of Finishing. - "Vestnik mashinostroyenia",[Russian] 1977, #8, p.68-71. 9. Davidson, D. A., “Mass Finishing Processes”, 1999 METAL FINISHING Guidebook and Directory, White Plains, NY: Elsevier Science, 1999 10. Davidson, D. A. "Current Developments in Dry Process Mass Finishing, Finishers Management, Vol 33., No. 7, September, 1988, p.43-46 11. Davidson, D. A., "Refining Plastic Surfaces by Mass Finishing Methods", Plastics Engineering, April, 1986 12. Davidson, D. A., High Energy Dry Process Finishing, SME Technical Paper MR90-389, International Manufacturing Technology Conference, Sept 6-10, 1990, Dearborn, MI: Society of Manufacturing Engineers 13. Davidson, D. A., “Developments in Dry Process Mass Finishing", SME Technical Paper MR89-147, SME - DSC89 Conference, San Diego, CA., Feb. 13- 16, 1989, 11
    • APPENDIX 1.1 – Typical Surface Profilometer Readings for TAM and Turbo-Polish SurfacesPROFILOMETER TAPE 1 – TURBINE DISK BEFORE TAM PROCESSING [Ra =57.0 micro-inch]Part: Nickel Alloy Turbine disk. As broached and rotary ground, prior to TAMprocessing.Profilometer reading was taken prior to processing to determine initial surfaceroughness and condition. Stylus was tracked on ground surface on part toothprior to TAM processing. Although TAM is looked at as primarily a deburringand edge contour method in this application, considerable refinement andimprovement of surfaces are generated also, as subsequent profilometertapes will show. 12
    • APPENDIX 1.2 - PROFILOMETER READINGS [Profilometer Tape 2] TURBINE DISKAFTER FOUR-MINUTE TAM PROCESSING WITH GRINDING MEDIA [Ra = 22.4micro-inch]As can be seen, Turbo-Abrasive Machining has removed burrs and developed edgecontour in the broach area of the disk in an accelerated automatic process (3-5minute cycles typically). But as an additional corollary effect, substantial surfaceimprovements are generated as can be easily discerned by a comparison of thisprofilometer tape of a reading taken of tooth surfaces after TAM with ZA grindingmedia. Further surface refinement is possible with the use of finer abrasive materialsin a secondary process (SEE Profilometer Tape 3) 13
    • APPENDIX 1.3 - PROFILOMETER TAPE 3 TURBINE DISK AFTER (1) TAMGRINDING (2) TAM POLISHING [Ra = 11.8 micro-inch]Part: Nickel Alloy Turbine disk, (1) TAM w/Grinding abrasives to deburr andedge contour (2) TAM with polish granules to enhance low Ra surfaces in bothedge and surface areasThis part shows even further surface enhancement, it has been processed in a twostep TAM method, utilizing first a grinding media for burr removal and edgecontour, and then a secondary process in which softer granular materials coatedwith micro-fine polishing materials to incrementally clear surfaces of peaks anddevelop the neutral or negative skew surface finishes desirable on this type ofcritical hardware. 14
    • APPENDIX 2.0 – PICTORIAL BEFORE AND AFTER COMPARISON OF TURBINE DISK EDGE AND SURFACE CONDITION (1) BEFORE TAM PROCESSING (2) AFTER TAM PROCESSING (1) Nickel Alloy Turbine disk, prior to TAM processing. Note feature sharp edges and rough rotary ground surfaces with linear. (2) The same disk after TAM, burrs removed, sharp edges replaced with uniform edge contour, and machining/grinding lines on the surface have been blended into a negative or neutral skewed surface profile with a more randomly oriented and finely defined surface pattern. 15
    • APPENDIX 3.0 – Before and after comparison of turbine blade surfaces. The first tape (L) shows initial “as cast” surface condition. The second tape (R) shows readings on the same blade segment after super-polishing or turbo-polishing using recipro- pressure finishing methods with successively finer free abrasive materials.16
    • APPENDIX 4.0 – Even very coarse surfaces can be improved by TAM methods. These tapes are a before and after comparison of very coarsely machined cast- iron bull gears. A short 4- minute process was sufficient to reduce surfaces from approximately 140 Ra micro- inch down into the 40’s (Ra micro-inch)17