01
Parts that grow or shrink after machining
POM takes on moisture slowly and then swells. If the shop machines wet stock to a dry drawing, bores close up and shafts no longer fit. Assemblies jam at the customer, and you eat the rework.
POM / Acetal · Engineering Plastics
Delrin CNC Machining
We turn Delrin (POM-H) and acetal copolymer into gears, bushings, insulators and slide parts. Tolerances hold because the material absorbs little water and cuts clean. One part or 10,000.
±0.005 mm toleranceRa 0.8–1.6 μm finishPOM-H and POM-CNo minimum order12-hour quote + DFM
127High-precision CNC machines
16Simultaneous 5-axis centers
±0.005 mmMachining tolerance
15 yearsMachining plastics and metals
Where plastic parts go wrong
Four failures we see on Delrin drawings
Most problems with this material start before the first cut. Here is what they cost you.
02
Fuzzy edges and chatter on thin walls
Delrin cuts clean when the tool and feed are right. Run it too fast and you get melted edges, stringy chips and chatter marks on walls under 2 mm. Cleaning those burrs by hand adds days.
03
Gears that wear out before their rating
A gear blank cut on a metal setup often carries the wrong surface finish and tooth profile. It runs hot, wears fast, and fails well before the load rating suggests. The root cause is the process, not the resin.
04
Quotes that ignore material grade and stress
POM-H and POM-C behave differently under load and heat. Shops that quote both as generic acetal hide the risk. You find out at first article, after tooling and lead time are already spent.
How we run it
Machining strategy built around the resin, not the machine
Delrin rewards the right cutter, the right stock condition and the right fixturing. Here is how we set up.
Stock and setup
Dry stock, stable temperatures, no surprises at inspection
We machine from controlled stock and let parts equalize before final inspection, so the dimensions on the report match the dimensions at your bench. Cutting stress is managed with conservative depths of cut and sharp, polished tooling.
Delrin has low water absorption. That is the property that makes it useful for close-tolerance parts, but only if the shop respects it from the first operation.
- 1Sharp, polished carbideReduces heat and melted edges on POM
- 2Staged cutsKeeps internal stress from springing the part
- 3Relax before final inspectionReadings hold after the part settles
Tolerances and finish
±0.005 mm where it matters, Ra 0.8–1.6 μm on wear faces
Bearing bores, gear hubs and sliding fits get the tight side of ±0.005 mm. Cosmetic and non-critical surfaces stay at a sensible Ra 1.6–3.2 μm to keep cost down. We machine Delrin on 3-axis, 4-axis and 5-axis centers, up to 4,000 mm in one setup for long profiles.
Delrin is self-lubricating and quiet in service, so many parts need no grease. That also means the surface finish you leave behind is the surface the part runs on.
- 1Wear facesRa 0.8–1.6 μm for bushings and cams
- 2Insulating partsClean edges, no conductive smearing
- 3Long partsUp to 4,000 mm on the large mills
Material choice
Delrin (POM-H) vs acetal copolymer (POM-C) vs nylon
Pick by load, moisture and chemical exposure, not by price per kilo.
| Property | Delrin POM-H | Acetal POM-C | Nylon PA |
|---|---|---|---|
| Stiffness | Highest of the three | Slightly lower | Lower, tougher |
| Water absorption | Low | Low | High, swells |
| Machined tolerance | Holds ±0.005 mm well | Holds well | Harder to hold |
| Wear and friction | Self-lubricating, quiet | Good | Good, but louder |
| Best fit | Gears, cams, close fits | General acetal parts | Impact parts |
What we machine
Plastic and metal work under one roof
Delrin jobs rarely travel alone. Most programs need a mix of processes.
01
CNC milling and turning
Delrin gears, bushings, insulators, manifolds and housings on 3-axis, 4-axis and mill-turn centers.
02
5-axis machining
Complex contours and multi-face parts in one setup. 16 simultaneous 5-axis centers.
03
Rapid prototyping
Machined Delrin prototypes to test fit and wear before committing to a run.
04
Surface finishing
Bead blasting, tumbling, polishing and laser marking on plastic parts.
05
Sheet metal and die casting
Brackets, frames and housings that pair with your plastic components.
06
Assembly and inspection
Sub-assembly, 100% inspection before shipment and reports on request.
Program scope
What a Delrin order includes
The same scope whether you order one prototype or 10,000 parts.
| Item | Standard | Notes |
|---|---|---|
| Tolerance | ±0.005 mm | Critical fits; looser where allowed |
| Finish | Ra 0.8–1.6 μm | Wear faces; Ra 1.6–3.2 μm elsewhere |
| Maximum size | 4,000 mm | Larger travel on the big mills |
| Quantity | 1 to 10,000+ | No minimum order quantity |
| Lead time | 3–5 days | After quote and DFM sign-off |
| Inspection | 100% before shipment | Reports available on request |
Why GreatLight
Numbers we can stand behind
Capacity and quality figures, not adjectives.
15Y
Machining since 2011
Fifteen years of plastic and metal work, three wholly-owned plants and 7,600 m² of floor space in Dongguan and Singapore.
127
CNC machines
16 simultaneous 5-axis centers, 12 four-axis mills, 27 three-axis machines and 16 mill-turn centers. Delrin runs on the right platform.
±0.005
Tolerance in millimeters
That is ±0.0002 in. Held on bearing bores, gear hubs and sliding fits in POM.
99.99%
Qualification rate
Raw material check, in-process monitoring and final inspection on every order.
12h
Quote and DFM
Quotation and free DFM analysis within 12 hours. Production can start within 24 hours.
ISO
Four certifications
ISO 9001:2015, IATF 16949:2016, ISO 13485:2016 and ISO 27001:2022. NDA available on request.
150Technicians
3Plants, Dongguan and Singapore
<2%Historical late-delivery rate
10,000+Part runs supported
Industry fit
Where Delrin parts get used
Automotive and EV
Gears, clips, window regulators and interior mechanisms. Low friction and quiet running matter more than ultimate strength.
- ±0.005 mm
- Ra 0.8–1.6 μm
- IATF 16949
Medical devices
Insulators, valve bodies and dosing components. Clean edges, no porosity and traceable inspection.
- 100% inspection
- ISO 13485
- Reports on request
Electronics
Insulating spacers, coil formers and connector bodies. Delrin keeps its arc resistance in humid rooms.
- Arc resistance
- Low water uptake
- ±0.005 mm
Industrial machinery
Conveyor wear strips, cams, bushings and star wheels. Self-lubricating parts that run without grease lines.
- No grease needed
- Wear resistant
- 4,000 mm max
FAQs
Questions engineers ask before ordering
What is the difference between Delrin and generic acetal?
Delrin is a homopolymer (POM-H). Generic acetal is often the copolymer (POM-C). The homopolymer is stiffer and has slightly better creep resistance, which is why it shows up in gears and close-tolerance cams.
The copolymer is easier to mold and resists some chemicals better. If your drawing says Delrin, tell us. We keep both on the shelf.
How tight can you hold Delrin parts?
±0.005 mm on features that matter, checked after the part has settled. That is ±0.0002 in.
Tighter than that is possible on a small feature, but we would rather talk about it first. POM moves with temperature, so a number tighter than the process supports is a number that will not repeat.
Will moisture change my part dimensions?
Delrin absorbs little water, but not zero. Long exposure to humid air can shift dimensions slightly. Parts machined from dry stock and allowed to equalize before final inspection are the safest route.
For parts that live in a wet environment, tell us at quote. We can bias the nominal size so the part lands in the middle of the tolerance band in service.
Does Delrin need lubrication in a bearing application?
Usually not. The friction coefficient is low and the material is self-lubricating, which is why it runs quietly in bushings and slides.
At high load and continuous speed, a light grease can extend life. We can machine a grease groove or a reservoir pocket if the design calls for it.
What temperature range can the part handle?
Long-term service in the range of -40 to 100 °C is the normal working window for POM. Short excursions above that are survivable but reduce life.
If your application sits near the top of that range, the design should account for thermal expansion. Delrin grows more per degree than steel, so a plastic part in a metal housing needs clearance.
Can you machine one prototype before a production run?
Yes. There is no minimum order quantity. We machine from a single part up to 10,000+ part runs on the same process.
Prototypes ship in 3–5 days after quote and DFM sign-off. Production can start within 24 hours once the design is frozen.
How do you prevent chatter and melted edges on thin walls?
Sharp polished tooling, moderate spindle speed and light radial depth of cut. Delrin is soft, so heat is the enemy, not the hardness of the material.
For walls under 2 mm we add support fixtures or leave a sacrificial web that gets removed in a later operation. That keeps the wall from deflecting into the cutter.
What files do you need for a quote?
A 3D model or a 2D drawing with tolerances, quantity and the material grade. STEP and PDF are the most useful formats.
Send what you have. We return a quotation and a free DFM analysis within 12 hours, and we flag features that will not hold before the chips fly.
Send a Delrin drawing, get a quote in 12 hours
Upload your model and we return pricing plus a free DFM review. No minimum order, from one prototype to 10,000+ parts.
12-hour quote100% inspectionNo minimum orderNDA on request
