⚪ DELRIN / ACETAL

Stamping Delrin and Acetal: Die-Cutting Thin Sheet vs Machining Everything Else

Acetal, sold as Delrin in its homopolymer form, is one of the most machined plastics in industry, and that reputation tells you most of what you need to know about stamping it. Thin acetal sheet die-cuts cleanly into flat parts, but acetal's stiffness and elastic recovery mean it does not cold-form into shaped parts; it springs back or cracks. The line between 'stampable' and 'machine it' falls at flat versus three-dimensional.

ISO 9001ISO 13485IATF 16949
The genuine stamping application for acetal is blanking and die-cutting thin sheet, roughly 0.010 to 0.062 inch, into flat parts: washers, thrust washers, spacers, insulating shims, wear pads, and gasket-style components. Acetal's low friction and good wear resistance make it ideal for these parts, and steel-rule or matched-metal dies punch them at high volume far more economically than machining each one. This is shearing, not forming. The die produces a flat profile from flat stock and the part stays flat. Acetal cuts cleanly with sharp tooling, producing crisp edges with minimal burr, which is one reason it is a favorite for high-volume flat wear and insulating parts. The process is mature and well understood; the main constraints are sheet thickness (thin enough to shear cleanly) and keeping tooling sharp, since worn edges leave a rougher cut and slight burr on the tough polymer.

Why acetal resists cold forming

Acetal is a stiff, highly crystalline thermoplastic with high tensile strength (around 9,000-10,000 psi) and, importantly, strong elastic recovery, it is the 'springy' engineering plastic. Those properties are great for snap fits and living-feature machined parts, but they fight cold forming: try to bend acetal sheet permanently and it either springs back to flat or, past its limited yield, crazes and cracks. It does not take a permanent cold set the way ductile metal does. So cold-stamping a formed 3D shape into acetal is not viable. Where a formed thin acetal feature is needed, thin sheet can be thermoformed by heating it toward its softening range, but acetal has a relatively narrow processing window and is less commonly thermoformed than amorphous plastics. For any real three-dimensional acetal part, the dominant methods are CNC machining from rod, plate, and tube, where acetal genuinely excels, and injection molding for high volumes. The takeaway: acetal die-cuts flat but is machined or molded for shape.

Homopolymer vs copolymer: which to die-cut

Delrin (acetal homopolymer, including the Delrin 150 grade) offers slightly higher strength, stiffness, and surface hardness than acetal copolymer, which makes it the choice for high-load wear washers and parts needing maximum mechanical performance. The tradeoff is that homopolymer can have a porous center in thick sections (centerline porosity) and is a little more sensitive to certain chemicals and to processing; for thin die-cut sheet this matters less, but it is a known consideration. Acetal copolymer trades a small amount of strength for better chemical resistance, better resistance to hot water and hydrolysis, and freedom from centerline porosity, making it the choice for parts exposed to harsh media or hot fluids. Both die-cut cleanly. The selection is application-driven: homopolymer (Delrin) for maximum strength and wear in dry parts, copolymer for chemical and hot-water exposure and where thick-section integrity matters. For thin flat die-cut parts the cutting behavior is similar, so the choice comes down to the service environment, not the stamping process.

Frequently Asked Questions

Yes, in the form of die-cutting or blanking thin acetal sheet into flat parts, but not in the sense of cold-forming a three-dimensional shape. Blanking thin acetal sheet, roughly 0.010 to 0.062 inch, into washers, thrust washers, spacers, shims, wear pads, and gasket-style components is a real and economical high-volume process using steel-rule or matched-metal dies, and acetal's low friction and wear resistance make it well suited to these flat parts. This is pure shearing, producing a flat profile from flat stock with clean edges and minimal burr. What you cannot do is cold-stamp acetal into a bent or drawn 3D part, because acetal is stiff and springs back elastically or cracks rather than taking a permanent cold set. For shaped parts, acetal is machined from rod and plate, where it excels, or injection molded at high volume. So acetal stamping is real for flat die-cut parts and not viable for cold-formed shapes.
Acetal is a highly crystalline engineering thermoplastic with high stiffness and strong elastic recovery, which is exactly the property that makes it good for snap fits and resilient machined features but bad for cold forming. When you bend acetal sheet, it stores the deformation elastically and springs back toward flat when released, and if you push past its limited yield it crazes and cracks rather than flowing into a permanent set. Ductile metals deform plastically by dislocation slip and hold a cold bend, but acetal's polymer structure does not rearrange permanently at room temperature, so it recovers its shape. This is why cold-stamping a formed acetal part does not work. To shape acetal in three dimensions you machine it from solid stock, mold it, or, for thin sheet and gentle geometry, thermoform it by heating toward its softening range, though acetal has a narrow processing window and is thermoformed less often than amorphous plastics. The springiness that defeats cold forming is the same property that makes molded acetal snap-fit parts work so well.
For thin die-cut flat parts, both cut cleanly, so the choice is driven by the service environment rather than the cutting process. Delrin acetal homopolymer, including grades like Delrin 150, offers slightly higher strength, stiffness, and surface hardness, making it the better choice for high-load wear washers and parts needing maximum mechanical performance in dry conditions. Its known limitations, centerline porosity in thick sections and somewhat lower resistance to hot water and certain chemicals, matter less for thin sheet but are worth noting. Acetal copolymer trades a little strength for better chemical resistance, much better resistance to hot water and hydrolysis, and no centerline porosity, so it is preferred for parts exposed to hot fluids, harsh chemicals, or where thick-section integrity is important. So pick homopolymer (Delrin) for maximum strength and wear in benign environments, and copolymer for chemical exposure, hot water, or hydrolysis resistance. For the die-cutting itself, the behavior is similar; the decision is about where the part will live.
It comes down to part geometry and volume. Die-cutting thin flat acetal parts is very economical at volume: a steel-rule or blanking die has modest tooling cost and then produces flat washers, shims, and gaskets at pennies each, far cheaper per part than machining them individually. The catch is that die-cutting only makes flat parts from thin sheet; the moment you need a three-dimensional shape, a thick section, threads, or precise 3D features, you must machine or mold. CNC machining acetal has no tooling cost and handles any geometry and thickness, and acetal machines beautifully with excellent surface finish and tight tolerances, but it is slower per part and costs more per piece, so it wins at low volume or for complex shapes. Injection molding has high tool cost but the lowest per-part price for complex parts at high volume. So the rule is: flat thin parts in volume, die-cut; complex or thick parts at low volume, machine; complex parts at high volume, mold. Matching the process to geometry and quantity is where the real cost savings are.

Related Pages

Delrin / Acetal CNC MachiningDelrin / Acetal Swiss MachiningDelrin / Acetal EDM / Wire EDMDelrin / Acetal Laser CuttingDelrin / Acetal Welding & FabricationDelrin / Acetal Injection MoldingAluminum StampingStainless Steel StampingCarbon Steel StampingTitanium StampingInconel / Nickel Superalloys StampingCopper Stamping

Last updated: July 2026

Find Delrin / Acetal Stamping Suppliers

Search verified shops that handle Delrin / Acetal stamping.

Search Manufacturers →Get Your Shop Listed (Free)

No logins. No email gates. Just results.