The Importance of Surface Finish in Components for The Aerospace and Medical Industries


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In the aerospace and medical fields the surface finish of machined components is of utmost importance.

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The Importance of Surface Finish in Components for The Aerospace and Medical Industries

  1. 1. The Importance of Surface Finish inComponents for The Aerospace andMedical IndustriesIntroductionIn the aerospace and medical fields the surface finish ofmachined components is ofutmost importance. Highpressure hydraulic systemsand fuel injections systems inparticular require high qualitysurfaces and precisely definedfeatures, such as o-ringgrooves, if system integrity isto be maintained. In themedical field, equipmentmanufacturers andpharmaceutical producers demand stringent specificationswith respect to surface finish. Literally, lives can be on theline if these systems fail, so it is critical that the quality ofthe machined components is maintained.Nuclead Inc. has over 30 years of experience producingcomponents for the Aerospace and medical fields. Thisarticle describes the capabilities and expertise availablethat has made that possible. First though we begin with anexplanation of surface roughness measurement anddefinition.
  2. 2. Surface FinishSurface finish is defined in terms of 4 factors: Roughness – closely spaced surface irregularities, resulting from the manufacturing process or tools Lay – the overall direction of the roughness pattern which can be affected by the machine and setup. Waviness – longer spaced irregularities caused by machine vibration and material warping among other factors. Flaws – unique surface imperfections in the material or processingSurface finish is measured in terms of RMS (root meansquare), this is the square root of the sum of individualsurface readings over a particular sampling distance.Another way of looking at this is that the higher the RMSvalue that is observed, then the greater the depth of anyirregularities on the piece and as a result the greater thelikelihood of poor functionality of the component.The surface finish requirements depend on theapplication. Low pressure applications may allow a RMSvalue as high as 64 or 128 microinches, a typical static sealmay require a finish with a RMS of 32 microinches, butmany applications in the aerospace and medical fields,particularly in high pressure systems, will require finishes
  3. 3. with a RMS of 8 to 10 microinches. This is well withinNuclead’s capabilities.In addition to RMS, surface roughness can also bemeasured using the value Ra (roughness average) this istypically measured using a profilometer.CapabilitiesFrom the definition of the factors affecting surfaceroughness as noted above, it is clear that achieving thebest in surface finish requires the manufacturer to haveseveral capabilities. These include the highest quality CNCmachines; experience, skilled and talented operators; QCmeasurement capabilities and modern CAD-CAM systems.Nuclead has all ofthese capabilities.The rest of thisarticle will providemore details on thecapabilitiesnecessary toproducecomponents of a quality to satisfy the Aerospace andmedical industries.CAD/CAMCAD/CAM refers to software tools that allow the designand drafting of prints (CAD), the electronic transfer of
  4. 4. those prints and the subsequent manufacture of thecomponent using computer contolled tools (CAM)Computer-aided design (CAD), software allows theoperator to use a computer to streamline the process ofdesigning and documenting components to bemanufactured at a subsequent operation. The output canbe for either print or machine code, and can display bothvector graphics as in traditional drafting or raster graphicsthat display the physical appearance of the finished object.Computer-aided manufacturing (CAM) takes the output ofthe CAD process, transfers it to a computer controlledmachine, like a CNC machine, and then uses the code tocontrol the machining of the component.CAD/CAM increasing efficiency in terms of both time andmaterial comsumption and also improves surface finishcapabilities. CNC Machining CNC stands for computer numerical controller that reads computer generated instructions that are extracted from electronic drawings. This allowscomplex 3 dimensional shapes to be created withinaccurate and repeatable precision. Thus allowing for the
  5. 5. custom fabrication of many components in quantities fromsingle parts to long production runs for both aerospaceand medical applications.As well as CNC machines, Nuclead also uses saws, mills andto produce these sophisticated components.Surface GrindingNuclead has surfacegrinding capabilities up to52" x 20" x 20" (LxWxH),and can hold tolerances of+/- .0001” and surfacefinishes of 6 rms. Nucleadcan OD and ID grind anymaterial to .0001”tolerance with .0001” roundness.Surface grinding is a common grinding operation used inthe finishing process it uses a rotating abrasive wheel tosmooth the flat surface of the workpiece. The workpiece isheld in place on a chuck, either by using a magnet orvacuum and is then moved under the rotating grindingwheel to allow the piece to be abraded.Nuclead offers Blanchard grinding services up to 60”diameter. Blanchard grinding, also know as Rotary SurfaceGrinding, removes large amounts of stock quickly and
  6. 6. efficiently and is ideal for large parts such as rotary tables,mold plates, and vacuum chambers.QC measurementIn addition to a full supply of qualified gages, digital heightsets, granite plates, comparators, profilometers, andinspection equipment, Nuclead also uses CMMs to checksurface profile can component specification. A coordinate measuring machine (CMM) is a device used in manufacturing and assembly processes to test a part or assembly against the design drawings. The CMM measures the X, Y, and Z coordinates positionof preprogrammed positions on the workpiece and thenuses regression analysis to determine to prove that thepart meet specification.Nuclead is an ISO9001:2008 certified company.Experience and ConclusionNuclead’s production machining and custom machiningcapabilities includes all materials used in aerospace andmedical industries, including beryllium, tungsten, nickel,titanium, stainless steel and invar.
  7. 7. For over 30 years, Nuclead’s experienced personal havebeen manufacturing components to high tolerances andsurface finishes that exceed the requirements of both theaerospace and medical industries.