Delrin and Acetal Machining Suppliers in Austin, TX

They are closely related but not identical, and the distinction matters when you specify a part. Acetal is the general name for the polymer polyoxymethylene, or POM, and it comes in two chemistries: homopolymer and copolymer. Delrin is a brand name, specifically DuPont's trade name for acetal homopolymer, so Delrin is a type of acetal, namely acetal homopolymer made by DuPont, and the two terms are often used loosely as if interchangeable. When someone says Delrin, they mean acetal homopolymer; when someone says acetal without qualification, they could mean either homopolymer or copolymer, so it pays to clarify. The practical difference between the two chemistries is real. Acetal homopolymer, which is what Delrin is, has somewhat higher mechanical strength, stiffness, hardness, and better fatigue and creep resistance, making it the choice for high-load mechanical parts, but it can have a small amount of porosity at the center of large-diameter rod and is slightly less resistant to hot water and alkaline chemicals. Acetal copolymer gives up a little strength in exchange for better resistance to hot water and chemicals, no centerline porosity, and slightly better long-term dimensional stability across temperature, so it is preferred for parts exposed to hot water or chemicals and for thick cross-sections. Delrin 150, which you will often see specified, is just a particular common grade of Delrin homopolymer, a medium-viscosity general-purpose acetal that most shops stock as rod and plate. For many general precision parts, either homopolymer or copolymer works fine and the choice comes down to availability and minor preference, but when the application involves high mechanical load, choose homopolymer like Delrin, and when it involves hot water, chemical exposure, or thick sections where porosity matters, choose copolymer. The key point for sourcing is to specify the exact grade you want, Delrin or Delrin 150 for homopolymer, or acetal copolymer, rather than just saying acetal, so the supplier provides the right material for your duty.

You pick between them based on whether the part's priority is maximum mechanical performance or better chemical and thermal-environment resistance, because that is the core tradeoff between the two acetal chemistries. Choose acetal homopolymer, which includes Delrin and Delrin 150, when mechanical performance is the priority. Homopolymer has higher tensile strength, stiffness, hardness, and notably better fatigue and creep resistance than copolymer, so it is the better choice for high-load gears, structural mechanical components, parts under sustained stress, and anything where you want to squeeze the most strength and rigidity out of acetal. Its tradeoffs are a potential for slight centerline porosity in large-diameter rod, which can matter for sealing parts or parts machined from the center of big stock, and somewhat lower resistance to hot water and strong alkaline chemicals. Choose acetal copolymer when the environment is the priority rather than peak strength. Copolymer resists hot water, steam, and alkaline and chemical environments noticeably better than homopolymer, it has no centerline porosity so it is more uniform through thick cross-sections and better for sealing surfaces and large parts, and it offers slightly better dimensional stability over a wide temperature range. You give up a small amount of strength and stiffness for those benefits. So the decision rule is concrete: if the part is a high-load gear, cam, or structural mechanical piece operating in ordinary conditions, lean homopolymer, Delrin; if the part sees hot water, steam, chemicals, or alkaline solutions, or is a thick or sealing part where uniformity and freedom from porosity matter, lean copolymer. For the large middle ground of general precision parts like bushings, rollers, fittings, and moderate-load gears in normal indoor conditions, both perform well and the choice often comes down to which material the shop stocks and slight cost or availability differences. Whatever you choose, specify it explicitly on the print, because the two are not identical and the supplier should not have to guess which acetal your application needs.

Acetal is one of the best plastics for gears, bearings, bushings, and other moving mechanical parts because it combines several properties that those applications specifically demand, in a single easily machined material. The first and most important is its low coefficient of friction combined with self-lubrication: acetal slides smoothly against metal and against itself with little friction and without needing added lubricant, so gears mesh and shafts turn in acetal bushings quietly and efficiently, and the parts do not require greasing, which is a major advantage in clean, maintenance-free, or food and medical applications. The second is excellent wear resistance: acetal holds up to repeated sliding and rolling contact over long service life without rapidly wearing away, so gears and bearings made from it last. The third is stiffness and strength: acetal is rigid and strong enough to transmit meaningful mechanical load, so gear teeth hold their shape under force and bearings carry load without excessive deflection, which lesser, softer plastics cannot do. The fourth is dimensional stability and very low moisture absorption: acetal absorbs almost no water, unlike nylon which swells with humidity, so acetal parts hold their dimensions and fits in service, critical for gears and bearings where clearances and tooth profiles must stay accurate. The fifth is fatigue resistance, especially in homopolymer, so gear teeth and flexing parts survive repeated load cycles without failing. And the sixth is its outstanding machinability, which lets shops cut precise gear teeth, accurate bores, and close-fitting bushings to tight tolerances quickly and with a fine surface finish, and surface finish matters for friction and wear in sliding parts. Put together, acetal gives you a part that is precise, stiff, low-friction, wear-resistant, self-lubricating, and dimensionally stable, which is exactly the recipe for a good gear or bearing. The things to design around are its relatively high thermal expansion, so clearances should account for temperature swings, and the fact that adhesives do not bond well to it, so acetal parts are joined mechanically. For unlubricated, precise, quiet, durable mechanical motion, acetal is hard to beat among plastics.

Acetal is one of the easiest engineering plastics to machine to tight tolerances, but holding those tolerances reliably, especially on precise, thin, or large parts, does call for attention to two things: internal stress and thermal expansion. The stress issue is that acetal, like other semi-crystalline plastics, has residual internal stresses locked into the stock from how it was extruded or cast, and when a machinist removes material, particularly unevenly or in large amounts, those stresses can redistribute and cause the part to warp, bow, or shift dimensions after it leaves the machine. On a loose-tolerance part this is negligible, but on a precision gear, a thin plate, or a part held to a few thousandths of an inch, it can push the part out of tolerance after the fact. The standard remedy is annealing: heating the acetal stock to a controlled temperature to relax internal stress before machining, and for the most demanding parts, annealing again between rough and finish machining so the part has fully relaxed before the critical dimensions are cut. A shop experienced with acetal anneals when the tolerances warrant it, and this is one reason to use a shop that machines acetal routinely. The second issue is thermal expansion. Acetal has a relatively high coefficient of thermal expansion, higher than metals and many plastics, so a part machined precisely at shop temperature can grow or shrink measurably if it operates at a different temperature, which affects tight fits, gear meshes, and bearing clearances. This is handled in design rather than machining: the tolerances and clearances should account for the temperature range the part will see, so a press fit or running clearance specified at room temperature still works hot or cold. Beyond those two, acetal machines beautifully, cutting cleanly at high speed, producing good chips, and taking a fine finish that supports tight tolerances and good surface quality, so it does not fight the machinist the way some plastics do. The summary is that acetal does not require exotic handling, but for precision parts a good shop anneals to control warping and the designer accounts for thermal expansion in the tolerances, and with those two practices acetal holds tight tolerances as well as any machinable plastic.