Delrin China CNC Machining

Delrin (POM) machining — stress relaxation and chip control on acetal

Delrin — POM, acetal — is the engineering plastic that machines like soft brass, and the difficulty is not the cutting but the dimensional stability. POM has a coefficient of thermal expansion roughly ten times that of steel, so a part cut at 25 °C and measured at 20 °C measures differently because the material contracted. A tight tolerance on POM is a tolerance that the temperature can invalidate, and the buyer who specifies a ±0.003 mm band on a POM feature without accounting for the thermal expansion is asking for a number the material cannot hold.

The cutting is straightforward. Sharp, polished, positive-rake carbide at high surface speed and a feed that keeps the chip light — POM chips cleanly when the shear is clean, and the surface finishes itself. Flood coolant or air-blast both work; air-blast is cleaner because it avoids the thermal shock a cold fluid applies to a hot cut. The built-up edge that plagues softer plastics is less of an issue on POM because the material is rigid enough to shear rather than rub, but a dull tool still smears the surface. The tool life is long because POM is not abrasive, and the cycle time is short because the surface speed is high.

The stability is the lever. POM relaxes stress over time — a part cut from a stress-containing billet moves as the stress redistributes, and the movement is in the dimensional result. The workable sequence is to rough the part, let it rest — hours or overnight, depending on the section — then finish-machine the stabilised blank. A shop that runs POM straight from billet to finishing reports a number that drifts; a shop that roughs and rests reports a number that holds. You should ask for the stress-relief sequence in the quote, alongside the tolerance band.

The measurement condition is the second lever. The part should be stabilised to the inspection room temperature before the Hexagon CMM reads it, because the expansion coefficient is high and a hot part measures smaller than the same part at equilibrium. The facility behind this guide runs POM on 100+ CNC machines including 3/4/5-axis milling at ±0.003 mm and Swiss-type turning at ±0.002 mm, with Hexagon CMM verification in a temperature-controlled inspection environment, and Ppk ≥ 1.67 initial on key characteristics and Cpk ≥ 1.33 in production under ISO 9001:2015 and IATF 16949:2016 (design clause 8.3 excluded). Specify the service temperature and ask for the stress-relief sequence. Contact Felipe Iglesias at [email protected] or +86 13126536955.

The shop behind this Delrin guide — stabilisation sequence in the process

Backing this guide is a 6,800 m² plant at No. 8, Shuibian Songyuan Road, Hengli Town, Dongguan, Guangdong, China 523470, running 100+ CNC machines — Mazak VARIAXIS I-600 and INTEGREX I-250H S, TSUGAMI B0206-III/B0205-III, STAR SR-32JII / SR-32J Type N, Citizen Cincom A20-3F7 — plus 3-, 4- and 5-axis milling and turning, 5+ wire EDM and a Hexagon CMM bench with 20+ gauges.

Milling holds ±0.003 mm, turning ±0.002 mm, and grinding or wire EDM ±0.002 mm, all checked on a Hexagon CMM with the 10:1 gauge rule applied to every feature. Capability: Ppk ≥ 1.67 initial and Cpk ≥ 1.33 in production on key characteristics. Certified to ISO 9001:2015 (116024/A/0001/UK/En), IATF 16949:2016 (131941/A/0001/SM/En, design clause 8.3 excluded, openly disclosed) and ISO 14001:2015 (116024/B/0001/UK/En), held by Dongguan Zhuohang Ltd, USCC 91441900MA4UWT6X39, established 2005. Customers across Austria, Belgium, the Czech Republic, Denmark, France, Germany, Greece, Hungary, Ireland, Italy, the Netherlands, Spain, Sweden and the United Kingdom in Europe; Brazil, Canada, Mexico and the United States in the Americas; China, Israel, Japan, Singapore and Sri Lanka in Asia; Australia and New Zealand in Oceania; and South Africa in Africa are supplied from China, worldwide. Contact Felipe Iglesias at [email protected] or +86 13126536955 to begin the quote, and ask for the certificate numbers, the machine list and a past CMM report together.

Sourcing Delrin parts from China changes what you should verify, because the material and the certificate travel with the part. These notes are written for you vetting a Chinese Delrin supplier, so the quote and the certificate can be checked in the same pass.

What Delrin is and why it is chosen

Delrin - the DuPont name for POM acetal - is the engineering plastic that fills the gap between a metal that is overkill and a commodity plastic that is too soft. It combines high stiffness, low friction, natural lubricity and excellent dimensional stability, and it absorbs far less moisture than nylon, so it holds its size in humid conditions. Gears, bearings, bushings, rollers and precision plastic parts are where it earns its keep.

Homopolymer or copolymer

POM-H, the homopolymer, has the highest strength, stiffness and hardness. POM-C, the copolymer, trades a little stiffness for better chemical and hot-water resistance and slightly better dimensional stability. The distinction matters in service: a part in hot water or aggressive chemicals leans copolymer, a dry high-load gear leans homopolymer. Naming the grade - or at least the service conditions - lets the shop pick correctly instead of guessing.

Machining, tolerance and heat

Delrin machines cleanly with sharp tools and holds a good surface. The one discipline is heat: it softens around 175°C, so an overheated cut or a dull tool smears the surface, and thick sections are annealed to relieve internal stress. The shop holds the drawing on a Hexagon CMM, and the anneal-before-finish sequence is what keeps a nominally in-spec plastic part from drifting later.

Cost, finishing and lead time

Delrin is economical and fast to run, so a quote is mostly cycle time. MOQ is 1 piece and lead times run roughly 3 / 7 / 30 days. Send the drawing to Felipe Iglesias at [email protected] or +86 13126536955 and ask for the grade recommendation - POM-H or POM-C - alongside the quote.

Sourcing Delrin from China, the mill certificate and the grade proof travel with the part; the notes below are what a China buyer should verify before the order.

Design rules for Delrin

Delrin machines cleanly, and the design rules are mostly about heat and stress. Keep walls reasonably uniform so they do not sink, remember the material softens around 175 C so it stays out of sustained heat, and for a load-bearing thread use a metal insert rather than the plastic itself. Thick sections should be annealed to relieve internal stress, otherwise a part that measures in spec on day one can drift after machining. If you call out the critical faces and the flatness, you get a part that stays stable.

When Delrin is the right call

Reach for Delrin when a metal part is overkill and a commodity plastic is too soft - gears, bearings, bushings and rollers that need stiffness, low friction and dimensional stability below about 100 C. Against nylon, Delrin absorbs far less moisture so it holds its size in humidity; against PEEK, Delrin is a fraction of the cost but gives up the temperature and chemical range. If you match the plastic to the service temperature and the load, you get the performance without paying for a higher grade than the part needs.

Verifying a Delrin supplier

Confirm the grade - POM-H homopolymer for stiffness, POM-C copolymer for chemical and hot-water resistance - because the two behave differently in service. Ask whether thick sections are annealed, and ask for the material specification with the quote. Delrin is economical to run, so a supplier that is vague about the grade or skips the anneal is cutting a corner that shows up later as a part that moved. If you ask the two questions, you lock the grade and the process in one exchange.

De-risking a first order

Start with a handful of parts to confirm the routing and the tolerance, then scale. The same machines, the same inspection bench and the same certificate numbers apply to a single piece and a production run alike, so a small first batch is the proof that a large one will hold the same numbers.

What this shop actually runs

Capability evidence should come as specifics, not slogans. Behind this guide is a 6,800 m2 plant in Dongguan, China running 100+ CNC machines with 100+ staff. The machine list by category:

• 5-axis machining centres (10+) - Mazak VARIAXIS I-600 (510/910/510 mm travel, 12,000 rpm, 22 kW, 71.6 N·m, 30-tool BT40) and Mazak INTEGREX I-250H S (B-axis 0.0001°, 24 kW, 124 N·m, 38-tool HSK-A63). Made for compound-angle parts, single-setup multi-face prismatic work, and aerospace fittings where datum transfer loss is unacceptable.
• 3-axis / 4-axis machining centres (50+) - Brother SPEEDIO S500Z2N / S700Z2N (10,000 rpm, 14/21-tool ATC, 0.7 s tool-to-tool, Z-axis 2.2 G) and Mazak VCE-430A L / VCE-570C L (10,000 rpm, 118 N·m, 24-tool ATC). Made for prismatic parts, plates, brackets, housings.
• Swiss-type turning centres (10+) - Citizen Cincom A20-3F7 (Φ20 mm, 10,000 rpm), TSUGAMI B0206-III / B0205-III (Φ20 mm, 0.1 µm), STAR SR-32JII / SR-32J Type N (Φ32 mm, 8,000 rpm). Made for long, slender rotational parts at ±0.002 mm.
• CNC turning centres (20+) - HEADMAN T70M/1250 (720 mm swing, 117 mm bore, 3,000 rpm, BMT75 12-station turret). Made for shafts, bushings, flanges up to ±0.002 mm.
• Wire EDM (5+) - Sodick AQ535L (550/350/300 mm travel, ±20° taper, 800 kg workpiece). Made for hardened tool steel, internal splines, sharp internal corners that milling cannot reach.
• Inspection: Hexagon CMM + 20+ gauges - Hexagon CMM for coordinate measurement, plus vision system, profilometer, hardness tester, coating thickness gauge, XRF for material verification. The 10:1 rule (gauge 10x more accurate than the band) is applied to every feature.
• Machine highlights - VARIAXIS I-600: one-setup multi-face 5-axis + MAZA-CHECK auto-calibration; INTEGREX I-250H S: DONE-IN-ONE mill-turn, B-axis 0.0001° + Ai thermal shield; SPEEDIO S500Z2N / S700Z2N: Z-axis 2.2 G + 0.7 s ATC; Swiss-type: guide-bush switchable + 0.1 µm resolution.

Tolerance: ±0.003 mm CNC milling / ±0.002 mm CNC turning / ±0.002 mm grinding and wire EDM. Capability: Ppk >= 1.67 initial on key characteristics, Cpk >= 1.33 ongoing.

Certificates: ISO 9001:2015 (116024/A/0001/UK/En), IATF 16949:2016 (131941/A/0001/SM/En, with design clause 8.3 excluded, stated openly) and ISO 14001:2015 (116024/B/0001/UK/En), issued to Dongguan Zhuohang Ltd, registration 91441900MA4UWT6X39, founded 2005.

Where we ship: Austria, Belgium, the Czech Republic, Denmark, France, Germany, Greece, Hungary, Ireland, Italy, the Netherlands, Spain, Sweden and the United Kingdom in Europe; Brazil, Canada, Mexico and the United States in the Americas; China, Israel, Japan, Singapore and Sri Lanka in Asia; Australia and New Zealand in Oceania; and South Africa in Africa — plus other countries and regions worldwide, shipped from our base in Dongguan, China.

Contact: Felipe Iglesias, [email protected], +86 13126536955.

Frequently Asked Questions

Standards referenced on this page

• ASTM B348/B348M-21 — Standard Specification for Titanium and Titanium Alloy Bars and Billets
• ASTM A582/A582M-12 — Standard Specification for Free-Machining Stainless Steel Bars
• ISO 9001 — Quality management systems — Requirements