Machining Plastics: Machining Plastics
The Essential Guide to Materials,Tools and Techniquesmachining plasticsMachining Plastics:
machining plasticsTable of ContentsTriStar Delivers Plastics Machining Expertise . 5Plastic is not metal . 6Machining Plastic has Unique Challenges . and Rewards. 6Material Selection: Thermoset vs. Thermoplastic. 9Thermoset plastics. 9Thermoplastics. 9Why machine plastics?. 11Machining Plastics 101: Limit Heat!. 11Drilling Operations. 12How do I reduce heat while machining plastics?. 12Drilling tips to maintain heat levels. 13Turning operations and heat levels. 14Turning tips for form or plunge cutting. 14Threading and Tapping . 15Threading and tapping tips. 15Milling and Cutting. 16Tips for milling with adhesive tapes. 16Beware of burrs. 17To remove burrs, consider . 172
machining plasticsSawing Operations. 18Sawing tips. 18The Coolant Connection. 19Machining Materials: Case Studies. 20Machining UHMW. 20Common applications of UHMW. 20The TriStar Advantage for Machining UHMW: Burr elimination forsmooth finish. 21Machining Nylon . 22Common applications of nylon. 22The TriStar Advantage for Machining Nylon: Reduced scrap and lowerlabor costs. 23Machining Acrylic. 24Common applications of acrylic. 24The TriStar Advantage for Machining Acrylic: Plasma pretreatment. 25Machining PTFE. 26Common applications of PTFE/Rulon. 26The TriStar Advantage for Rulon/PTFE: Noise reduction, improvedwear and performance . 273
machining plasticsMachining PEEK. 28Common applications of PEEK. 28The TriStar Advantage for Machining PEEK: Reduced part distortion forhigher production . 29Machining Composites. 30The TriStar Advantage for Machining Composites: Turnkey solutionreduces delivery time. 31Machining Plastics: Consider the benefits of outsourcing. 32TriStar’s machine shop features. 33TriStar’s equipment inventory includes. 33CNC Swiss Screw Machines. 33CNC Milling. 33CNC Turning. 334
machining plasticsTriStar Delivers Plastics Machining ExpertiseTriStar Plastics offers complete plastic manufacturing, machining, surfacemodification and distribution — we are your source for one-stop-shopping ofengineered plastics. With the latest CNC machining, turning and milling equipment,we can guarantee your parts will meet design specs and are fully inspected andcertified. We can also help you save on component costs by suggesting alternateTriStar offers the latestmaterials, or providing machining tips to help you reduce scrap; we’ve built a solidmachining equipmentreputation in over 70 industries. And since we do it all in-house, we’ll help youstaffed by experiencedreduce fabrication delivery time so that you can meet your production deadlines.operators trained in the latestIn addition to the one-on-one support we offer, we have a number of onlineresources at tristar.com you can take advantage of. They include: Our interactive Material Database Design Worksheets Instructional video library Technical email updates Monthly technical briefs Direct support from TriStar engineers via our Ask the Expert ufnPrototypesEducationact u ri n gMaterials5Sciencetechniques to help you makethe most of your materialinvestment.
machining plasticsPlastic is not metal.This is the first lesson many fabricators discover when attempting tomachine plastics for the first time. While both materials are technically“machinable,” the similarities end there.Metals are generally pure materials, while plastics are a hybrid of different components.Whereas metals retain their shape and have a predictable melting point, plasticscan expand to five (or more) times their original dimension and offer varying heattolerances. Machining metals follows a predictable pattern with minimal creep. Whenmachining plastics, quick adjustments must be made to accommodate substantial creep— not to mention that the material has a strong propensity for chipping and meltingduring machining.Plastic materials areSimply stated, the basic principles of machining metals do not apply when machiningchallenging to machineplastics.given substantial creep,varying heat tolerances anda propensity for chipping andMachining Plastic has Unique Challenges . and RewardsWith the right material selection, proven handling techniques, plus the proper toolsand coolants, machining plastic parts is not only attainable, but achievable by manymachine shops.The goal of this technical guide is to demystify the art of machining plastics. We’llexplore plastic properties, selection criteria, price points, expansion rates, tolerances,and nuances of material and tool selection and review machining techniques. Becausewhen you fully understand the significant differences between machining plasticsvs. machining metals, you can improve your design and, ultimately, the quality andperformance of your product.6melting.
machining plasticsMaterial Selection: Cost vs. performanceHow do you select the ideal material for your application? There’s still awidespread belief that “traditional” metals outperform plastics, when actuallythe opposite is true. Plastics are an excellent replacement for bronze, stainlesssteel, and cast iron, and they excel in high-temperature and extreme workingenvironments.But this high level of performance comes at a cost. Plastics are not “the cheapstuff,” and some high-performance formulas are substantially more expensive thanPlastic materials are ametal. For example, Polybenzimidazole (PBI-Celazole) is 25x the price of cold-superior replacement forrolled steel, and 15x more costly than Type 303 stainless steel. Given these pricetraditional metals, bronze,points, it is critical to employ expert machining techniques to use costly materialsstainless steel and cast iron.efficiently and reduce scrap.Ultimately, the decision of material type should come down to an investment inperformance. Choosing a higher-quality material will yield a higher-quality part.And higher-quality parts can save you from in-field failures or costly recalls downthe line. Better to invest up-front and avoid these hazards.When should you choose plastic over metal materials? Consider the advantages ofplastic machined parts, they have the ability to: Reduce component weight Eliminate corrosion Lower noise level Improve wear performance Extend service life Insulate and isolate (thermally and electrically)7
machining plasticsRelative Cost of Plastic MaterialsPVC0.5UHMC0.6NYLON 1.8NORYL2.2STEEL2.3POLYSULFONE3.7BRONZE4.4ULTEM PEI4.8POLYETHERSULFONE5.4STAINLESS STEEL6.7TEFLON PTFE7.1KYNAR PVDF9.1Consider the cost vs.performance when choosingmaterials to make the most ofyour investment.RULON LR 16.9TECHTRON PPS 17.8PEEK 25.1RULON J 25.7TORLON PAI 30.5POLYIMIDE 79.5CELOZOLE PBI 101.40204086080100120
machining plasticsMaterial Selection: Thermoset vs. ThermoplasticNow that we’ve established the costs associated with plastic materials, the questionthen becomes which category of plastics should you choose?Thermoset plastics retain their solid state indefinitely and include just a fewtrade names. Thermoplastics can be melted more than once to form new shapesand comprise the largest group of plastics. They are also the type best suited tomachining. Don’t be fooled by similar-sounding names; as each “thermo” categoryboasts unique characteristics.Thermoset plastics: Do not melt since they chemically change in molding Are usually brittle and chip easily Often incorporate fillers as part of a composite Common formulas:àà Phenolicàà Epoxyàà PTFEàà Micartasàà MelaminesThermoplastics: Largest class of plastics Melt and reform without changing chemically Include a diverse list of trade and generic names including:àà Acetal, Acetal, ABS, Nylon, Polyethelene, PVC, Teflon Filler options include:àà Glass fibers, Carbon fibers, Graphite, Carbon, Molybdenum disulfide,PTFE9
machining plasticsIn an industry where brand name recognition can lead to an automatic materialorder, beware of the plastic material “name game” — where each processor names“their” material for what is essentially a trade product. For instance, the materialAcetal is a generic material, yet there are several different market names for it.DuPont calls its version Delrin . Hoechst uses the name Hostaform . Celcon is the Celeanse trade name, and Quadrant calls certain Acetal versions Acetron ,while Ensinger-Hyde uses the name Hydex . That marks five different names for asingle product — no wonder there is confusion in the marketplace!To learn more about the hazards of unknowingly purchasing counterfeit materials,check out our free companion paper, Rulon Bearings: How to Recognize GenuineWhile cost is important,and Avoid Counterfeit.ultimately, materials shouldbe selected based on theirapplication performance andtrue trade name.10
machining plasticsWhy machine plastics?Once you’ve selected the proper plastic material, the next question becomes oneof machining vs. injection molding. Most plastic components are produced viainjection molding, which is the most cost-effective method. But machining is thebetter fit based on: Low initial costs – molding equipment requires a large initial investment intooling equipment. Machining is more economical for lower volumes andprototypes. With plastics, alwaysTight tolerances – machining allows for much tighter dimensional tolerancesconsider heat tolerances andthan can be achieved with injection molding.keep in mind that drillingPhysical property limitations – some materials such as PTFE and UHMWare impossible to mold and require machining. Stress factors – injection molded parts are subjected to more stress thanextruded rod, tube, and sheet. Machining will produce more consistentresults.Typical applications for machining plastics include semiconductor processingcomponents, heavy equipment wear parts, and food processing components.Machining Plastics 101: Limit Heat!The most important consideration in machining is to limit the amount of heatbuildup, as the very act of machining generates friction, and thus, heat. Be awarethat anytime you machine plastics, your cutting tool can instead become a “meltingtool.” Heat also presents dimensional challenges, so you must be aware that as apart expands it becomes more difficult to hold tolerances.11generates more heat than anyother machining technique.
machining plasticsDrilling OperationsHeat-related changes are more prevalent with some plastics than others. Many ofthe plastics with high-expansion rates have low-melt temperatures. For instance,UHMW, has an expansion rate 20x that of steel and a melt temperature of 266 F.Fillers add another new level to expansion rates. Unfilled PEEK expands 26 X 10’6in/in/OF while 30% carbon fiber filled PEEK is 10. In contrast, adding PTFE only toPEEK raises the expansion rate to about 30, yet none of these fillers change the melttemperature.DrillingDrill PointAngleGroundReliefMORE HEAT IS GENERATED IN DRILLINGTHAN IN ANY OTHER OPERATIONTwist drills with twist angles between12 and 18 degrees- Large flute area assists inchip removalCutting lip should be ground so one edgeis .005” to .010” longer than the otherUse blunt angles (115 to 130 degrees) forthinly walled pieces to prevent expandingHelix Anglethe ODHow do I reduce heat while machining plastics?Intolerance to heat can appear as surface finishes that go from smooth to veryrough. Or you may notice small balls of melted plastic on the surface of yourcomponent. To reduce the impact of friction-induced heat, consider the followingpotential causes: Cutting speeds & feed rates Tool designs Cutting tool materials Use of coolants Sharpness of cutting tools12
machining plasticsDrilling tips to maintain heat levels: Drills with twist angles of 12 -18 and with large flute areas will helpremove chips and heat from the drilling hole. Grinding relief onto the drill will also reduce friction. Angles will vary bymaterial, but 20 -50 is a good starting point. For softer materials, high-speed steel drills are adequate, but highly-abrasiveplastics (filled materials), require carbide (Titanium Nitrite/TiN/AlTiN), CVD(chemical vapor deposition) diamond, or PCD ( polycrystaline diamond)tooling. Remove the drill from the hole (pecking) frequently to remove chips andgive the material a chance to cool slightly. Slower RPMs than technically called for can be beneficial depending on thematerial and other conditions. Never use any tool that has already drilled metal, as it is too dull and willimpact tolerances and surface finishes.Drill Size Vs RPMDrill SizeRPMNo. 60 thru 335,000No. 32 thru 173,000No. 16 thru 3/81,3007/161,0001/21,000A thru D2,500E thru M1,700N thru Z1,30013
machining plasticsTurning operations and heat levelsThe number one challenge in turning — just as in general machining — ismaintaining proper heat levels. Turning operations require inserts with positivegeometries and ground peripheries. Ground peripheries and polished-top surfacesgenerally reduce material build-up on the insert, which can improve the finalsurface finish. A finely-grained C-2 carbide or PCD is generally the best option forturning operations. Try to mill the slot across the outer diameter to break up chips.Plunge cutting or peck (interrupted cut) drilling is a good way to remove materialand to provide dimensional repeatability, but there are a few rules to follow.Turning tips for form or plunge cutting: Insert the tool width at less than the minimum diameter of the component Consider feed rates, which are dependent on the stiffness of the stock (butgenerally 0.004 TO 0.010“/REV) Surface finish at the bottom of the cut is best controlled by approachingthe bottom of the cut slowly, reaching the bottom, and clearing the toolimmediately. Use the smallest width possible to turn across. Do not dwell at termination, or you may experience drag that alters thesurface finish. When turning (lathing), use single-point or partial threading inserts. Thisresults in cleaner threads and provides ample room for chips. For milling, use single-form thread milling cutters for soft materials; multiform for harder materials.14
machining plasticsThreading and TappingAll plastics are notch sensitive, meaning that small sharp “V” threads can causeproblems such as tearing. By putting a chamfers on the rod ends or into the holesbefore a threading operation, you can reduce the tendency of the initial thread totear. We often recommend the use of coolants when threading and tapping. Andremember that any instrument that has tapped metal is not sharp enough to tapplastics.Threading and tapping tips: Threading is best achieved with a single point using a carbide insert andtaking four to five 0.001” passes at the end. Use H-3 for smaller diameters, H-5 for larger. There are .003”/.005” oversized taps available that can achieve a qualifiedthread size with softer materials. Many soft materials will expand out, thenclose back in when tapped. Thread-milling gives you better size controlwhen the size and depth is friendly for the feature. Two flute taps with enlarged flutes will help remove chips and keep the tapsclear. If the tapped area must withstand heavy stresses or continued insertion andremoval of connectors, the use of metal threaded inserts is preferred over atapped plastic piece. Inserts can be pressed into place, ultrasonically inserted, or threaded into theplastic using self-tapping features. Ultimately, the structural integrity of the material (hard or brittle) willdetermine the best insert type.15
machining plasticsMilling and CuttingWhen it comes to milling plastics, climb milling is recommended over conventionalmilling. And the most difficult challenge is in keeping the component from movingor vibrating during operation, which can result in chatter marks on the components.To maintain control, we often employ vacuum systems (which require a flatsurface) or fixture clamps (which seem to always get in the way). But be awarethat these methods are acceptable as long as they do not stress or distort the piece.For best results, we often recommend double-sided adhesive tape to prevent partsfrom moving.Other work-holding methods include building holding tools from excess material,making drill-through holes for top clamps and nuts, board mounts, and vacuumchucks (these are often built into CNC routers).Tips for milling with adhesive tapes: Completely clean both the machine surface and the work component beforebeginning. Make sure the surface of the work piece is completely covered in tape. Place the piece onto the machine surface as quickly as possible afterremoving the protective layer. Tap the piece with a rubber mallet to insure it is securely seated To remove the completed piece it may be necessary to dissolve the adhesivewith alcohol and pry apart carefully.16
machining plasticsBeware of burrsA common hazard of milling is burrs, which are created when a tool reaches atravel end and the plastic piece is not supported. To e
Machining metals follows a predictable pattern with minimal creep. When machining plastics, quick adjustments must be made to accommodate substantial creep — not to mention that the material has a strong propensity for chipping and melting during machining. Simply stated, the basic principles of machining metals do not apply when machining
Machining metals follows a predictable pattern with minimal creep. When machining plastics, quick adjustments must be made to accommodate substantial creep — not to mention that the material has a strong propensity for chipping and melting during machining. Simply stated, the basic principles of machining metals do not apply when machining
There are different types of machining process used for sapphire material. The fig. 1 shows a graphical representation of sapphire machining processes i.e. laser machining process, grinding process, polishing process, lapping process, new developed machining process, compound machining process and electro discharge machining process. Fig.1.
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where the use of 5-axis simultaneous machining brings unequalled surface quality. Moreover, it is targeted at prototype machining, 5-axis trimming and special machining where full 5-axis machining is the requirement for quick and accurate manufacturing. Multi-Axis Surface Machining is also an add-on product to Prismatic Machining and Lathe .
Mapping of global plastics value chain and plastics losses to the environment onment 2 Table of contents Table of contents List of Acronyms 4 Types of plastics 5 Executive summary 6 Technical summary 9 1 oduction Intr 17 1.1. Objective 19 1.2. General methodology 19 1.3. Report structure 21 2 Global plastics value chain 23
The milling machining is limited to the XY plane and can thus follow 2-dimensional contours. The machining itself is limited to 2-dimensional contours. The third dimension is achieved by tilting and securing the machining plane. To machine the free -form surfaces, the 5 axes move dynamically and simultaneously. 2D machining . 2½D machining
Engineered Plastics Cope Plastics, Inc. has hired John Thiel as director of sales - engineered plastics. Thiel joins Cope Plastics from All-State Industries where he . territory manager for Quadrant (formerly known as DSM) and has been working as a
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