Delrin vs nylon comes up on almost every tooling drawing that involves a wear face, a bushing, or a part that has to slide against something else. Both are engineering thermoplastics, both have been in machine shops for decades, and the usual advice stops at stiffer versus tougher, which is true and not very useful.
The more decisive difference is not on the datasheet at all. Delrin arrives as stock that gets machined. Nylon, in the form we work with it, is sintered directly to shape. That changes what each material lets you design, and on robot tooling it usually matters more than the mechanical numbers do.
Delrin vs Nylon: The Short Answer
Delrin is stiffer, harder, slipperier and far more dimensionally stable in humidity. Nylon is tougher, better at absorbing impact, and can be printed into geometry that machining cannot reach. For a small sliding or bearing surface, Delrin usually wins. For a large tooling body with internal channels and a weight budget, sintered nylon usually wins.
The mistake worth avoiding is treating the choice as material against material when it is really part against part. A machined acetal bracket and a printed nylon bracket rarely have the same geometry, because each process rewards different shapes, so the comparison that matters is between the two finished designs rather than between two rows on a datasheet.
What Each Material Actually Is
Delrin is a DuPont trade name for acetal homopolymer, also written as POM-H, a polymer built from a chain of alternating carbon and oxygen atoms. Acetal copolymer, usually written POM-C, is a closely related material with slightly different chemistry and slightly lower strength. When a drawing says acetal without saying which, that ambiguity is worth resolving before you quote it.
Nylon is the common name for polyamide, and in laser sintering it almost always means PA12. If the naming of the polyamide grades is unfamiliar, our guide to polyamide vs nylon covers what the numbers mean and why PA12 is the sintering default.
One practical point that decides a lot of projects: acetal is not a laser sintering material. There is no standard POM powder for the process, so a part specified in Delrin is a machining job by definition. That is not a limitation of any one supplier, it is a property of the material.
The Numbers Side by Side
The table below puts published values against each other. Delrin figures come from an Ensinger Delrin acetal homopolymer stock shape datasheet, and the PA12 figures come from the EOS PA 2200 material data sheet.
| Property | Delrin, acetal homopolymer | Laser sintered PA12 nylon |
|---|---|---|
| Tensile strength | 75.8 MPa (11,000 psi) at yield, ASTM D638 | 48 MPa, EN ISO 527 |
| Tensile modulus | 3,100 MPa (450,000 psi) at 1 percent strain, ASTM D638 | 1,700 MPa, EN ISO 527 |
| Elongation at break | 25 percent, ASTM D638 | 24 percent, EN ISO 527 |
| Density | 1.41 g per cubic cm | 0.93 g per cubic cm |
| Water absorption | 0.25 percent at 24 hours, 0.90 percent at saturation, ASTM D570 | Low, and the reason PA12 is chosen over PA6 and PA66 for dimensional work |
| Melting temperature | 175 C (347 F), ASTM D2133 | 172 to 180 C, EN ISO 11357-1 |
| Dynamic coefficient of friction | 0.2, ASTM D3702 | Higher than acetal |
| How you get the part | Machined from extruded or cast stock | Laser sintered directly to shape |
Read that table with one important caveat. The Delrin values were measured to ASTM methods and the PA12 values to ISO methods, and the two families use different specimen geometry and conditioning, so the comparison is indicative rather than exact. Beyond that, the Delrin numbers describe machined stock while the PA12 numbers describe laser sintered test bars, and a sintered part carries its own orientation effects. Treat both columns as the shape of the difference, not as a head to head measurement.
Moisture: The Difference That Decides Most Jobs
Acetal absorbs very little water, at 0.25 percent over 24 hours and 0.90 percent at saturation on the Ensinger datasheet, and PA12 is also among the low absorbing polyamides. That makes both of them safe choices in a damp plant, which is exactly why this comparison is more interesting than nylon against PA6 or PA66.
Where it still matters is at tight running clearances. A bushing or a slide that has to hold a few hundredths of a millimetre through a washdown cycle is more predictable in acetal, because it moves less and it moves back. On a large printed tooling body the same absorption is spread over a much bigger part and rarely affects anything the tool has to do.
The practical rule we use: if the dimension in question is a fit, favour acetal. If the dimension is a footprint, the difference stops mattering.
Wear, Friction and Impact
Acetal is the better sliding material. Its dynamic coefficient of friction is quoted at 0.2 on the Ensinger datasheet under ASTM D3702, and it is harder and stiffer than PA12, which is why gears, cams, bushings and guide rails have been machined from it for decades. If a surface rubs continuously against metal, acetal is the default answer and nylon is the compromise.
Nylon returns the favour on impact. PA12 is the more ductile of the two in practice, which matters on tooling that gets knocked, crashed or dropped, because a stiffer part tends to crack where a tougher one deflects and recovers. On a robot tool, a crash is not a hypothetical, and a part that survives one is worth more than a part that slid slightly better.
The useful synthesis is that these two properties do not have to compete. A printed nylon body with a small machined acetal wear strip where the rubbing actually happens gives you both, and it is a far more common solution than picking one material for the whole part.
Machined or Printed: The Difference That Is Not on the Datasheet
This is where the comparison usually gets decided. Machining removes material from solid stock, so cost tracks the time spent cutting and the geometry is limited to what a tool can physically reach. Laser sintering builds the part up, so cost tracks the volume of the build the part occupies and internal geometry is effectively free.
For robot tooling that difference is decisive, because tooling is mostly air routing, mounting features and structure. A printed nylon tool can carry its vacuum channels inside the body with no drilled passages, plugs or fittings, and it can be lightened wherever the load case allows. The same part in machined acetal is heavier, has to be plumbed externally or drilled and plugged, and pays for every internal feature in setup time.
Acetal keeps the advantage when the part is small, simple and dimensionally critical. A guide block, a bushing, a wear pad or a cam is quick to machine, holds tolerance easily, and gains nothing from being printed. Our design guidelines for SLS set out where the printed side of that boundary actually sits.
Where Each One Belongs in Robot Tooling
We are Anubis 3D Industrial Solutions. We design and manufacture end-of-arm tooling and produce parts by selective laser sintering in polyamide at our facility in Mississauga, Ontario. We do not print Delrin, because acetal is not a laser sintering material, so when a feature genuinely needs it that feature gets machined.
In practice the split on our tools looks like this. The structure, the vacuum plenum, the mounting interface and anything large or geometrically complex is printed nylon, because that is where consolidation and weight saving pay. Threads that get serviced take heat set inserts rather than relying on the polymer. Anything that slides, indexes or wears against metal is a candidate for a machined acetal detail fastened into the printed body.
That hybrid is not a compromise, it is the point. Choosing one material for an entire tool is how you end up either with a heavy tool that slides nicely or a light tool with a worn contact face. Most of the end-of-arm tooling we build mixes the two deliberately.
Delrin and Nylon Questions
Is Delrin stronger than nylon?
In tensile strength and stiffness, yes. Published values put Delrin acetal homopolymer around 75.8 MPa tensile at yield with a 3,100 MPa modulus, against 48 MPa and 1,700 MPa for laser sintered PA12. Nylon is the tougher material under impact, so strongest depends on whether the load is steady or sudden.
Can you 3D print Delrin?
Not by laser sintering. There is no standard acetal powder for the process, so parts specified in Delrin are machined from stock. If a design needs acetal properties in one area only, the usual answer is a printed nylon body with a machined acetal detail fitted into it.
Which absorbs less water, Delrin or nylon?
Acetal absorbs very little, quoted at 0.25 percent over 24 hours and 0.90 percent at saturation. PA12 is also low absorbing compared with PA6 and PA66. The difference matters at tight running fits and is usually irrelevant across a large part.
Which is better for robot tooling?
Sintered nylon for the tool body, because it consolidates geometry and saves weight the robot has to carry. Machined acetal for small sliding, indexing or wearing features. Many tools use both, with acetal details fastened into a printed nylon structure.
Not Sure Which Material Your Part Needs?
Send us the part, the loads it carries and what it rubs against, and our team will tell you what should be printed, what should be machined, and where the line between them falls on your design.
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