This guide is written from the perspective of a job shop that machines all six materials weekly. It compares them on machining speed, achievable tolerance, surface finish, cost-per-cm³ of finished part, and which application each is genuinely best at. By the end you'll be able to specify the right material on your next drawing without sending an engineer down a Google rabbit hole.
1. The 6 materials we machine and what each is for
Quick orientation — we'll go deep on each in the next sections:
- UHMWPE (PE1000). Ultra-wear-resistant, low friction, low strength, soft. Liners, rollers, ice rink boards, food chutes.
- HDPE (PE100/300/500). Cheaper UHMWPE-cousin, less wear-resistant, fine for cutting boards, ground mats, splash plates.
- POM (Delrin / Acetal). Stiff, strong, low-friction, dimensionally stable. Gears, sliders, conveyor parts, automotive bushings.
- PA6 / PA66 (Nylon). Strong, tough, can be glass-filled. Bushings, sleeves, cams, structural brackets.
- PTFE (Teflon). Best chemical resistance, best low-friction, terrible mechanical strength. Seals, anti-stick liners, chemical handling.
- PEEK. Highest temperature, highest strength, hospital-grade chemical resistance. Aerospace, medical, semiconductor.
2. CNC machinability comparison
From the perspective of getting metal off in the chip pan:
| Material | Cutting speed (m/min) | Tool wear | Chip type | Achievable tolerance | Surface finish (mill) |
|---|---|---|---|---|---|
| UHMWPE | 300-500 | Very low | Long stringy | ±0.1 mm (sub-100 mm part) | Ra 1.6 µm |
| HDPE | 300-500 | Very low | Long stringy | ±0.15 mm | Ra 3.2 µm |
| POM | 200-400 | Low | Short curl | ±0.05 mm | Ra 0.8 µm (mirror-able) |
| PA6 (cast) | 150-300 | Low-medium | Medium curl | ±0.05 mm (controlled humidity) | Ra 0.8 µm |
| PA6 GF30 (glass-filled) | 100-200 | High (use carbide) | Short broken | ±0.05 mm | Ra 1.6 µm |
| PTFE | 200-400 | Very low | Crumbly powder | ±0.1 mm | Ra 1.6 µm |
| PEEK | 100-250 | Medium-high | Short curl | ±0.03 mm | Ra 0.4 µm |
3. Cost comparison for a typical CNC part
Indicative price for a 100×100×20 mm milled part with simple pocket and 4 holes (one piece, batch of 10), ex-Qingdao, June 2026 prices:
| Material | Material cost (US$/kg) | Part price (US$, batch of 10) | Cost vs UHMWPE |
|---|---|---|---|
| HDPE virgin | 2.40 | 11.50 | 0.65× |
| UHMWPE PE1000 | 4.80 | 17.50 | 1.0× (baseline) |
| POM (Delrin natural) | 5.90 | 20.00 | 1.14× |
| PA6 cast natural | 5.40 | 19.00 | 1.09× |
| PA6 GF30 | 7.20 | 24.50 | 1.40× |
| PTFE virgin | 18.00 | 55.00 | 3.14× |
| PEEK natural | 120.00 | 320.00 | 18.3× |
4. Choosing the right material — decision tree
Answer in order:
- Will it touch food, drinking water, or pharma product? → UHMWPE FDA grade, POM FDA, PEEK food-grade, or PTFE virgin.
- Operating temperature > 100 °C? → PA6 to 130 °C, PEEK to 250 °C, PTFE to 260 °C. Drop UHMWPE/HDPE/POM.
- Continuous heavy abrasion (rocks, sand, ore)? → UHMWPE wins, PE9000 if extreme. Avoid POM/PA6.
- Sliding metal-on-plastic, low load, no lube? → POM acetal first choice. PA6+oil-impregnated second. UHMWPE third (cheapest if size allows).
- Dynamic load, high stiffness needed? → PA6 GF30 or PEEK. Avoid UHMWPE (too soft).
- Aggressive chemicals (acids, solvents)? → PTFE first, PEEK second.
- Default — wear part with moderate load? → UHMWPE. Cheapest acceptable solution wins.
5. Common machining mistakes per material
UHMWPE — don't rush feeds; the chips weld back to the cutter. Use compressed air, not flood coolant.
POM — keep tools sharp; dull tools cause chatter and dimensional drift on long runs.
PA6 — absorbs moisture (up to 8% by weight). Machine and inspect at controlled humidity, or part dimensions will drift.
PTFE — chips become powder; airborne PTFE dust is a respiratory hazard. Vacuum extraction is mandatory.
PEEK — use sharp carbide, peck-drill deep holes (chips pack and re-melt), and never let temperature exceed 150 °C in the cut.
6. Material certifications and traceability
What we can supply with each material:
- UHMWPE / HDPE / POM / PA6: FDA, EU 10/2011 food-contact letters; REACH SVHC declaration; per-batch MTC.
- PTFE virgin: FDA, USP Class VI medical-grade letter, REACH.
- PEEK: USP Class VI, ISO 10993 biocompatibility, full lot-trace from Victrex/Solvay supplier.
- UL94 V-0 fire rating: PEEK, glass-filled PA6 V-0 grade, PTFE.
- 3.1 / 3.2 mill certificates available for any material on request.
❓ Frequently Asked Questions
❓ Why is PEEK so much more expensive?
Raw resin is ~US$120/kg vs ~US$5/kg for UHMWPE. PEEK is also harder to machine (slower feeds, more tool wear). For most applications PEEK is overkill — only specify it when temperature, chemicals, or biocompatibility demand it.
❓ Can you supply colored POM or PA6?
Yes — standard colors black, blue, red, green, yellow. Custom RAL on orders ≥100 kg of resin.
❓ What's the largest single PEEK part you can machine?
Stock plate availability limits us to ~600×400×50 mm in single piece. Larger needs jointing.
❓ Is HDPE strong enough for a structural bracket?
Usually no — HDPE creeps under sustained load. Use PA6 cast for structural brackets.
❓ Do you machine glass-filled or carbon-filled grades?
Yes — PA6 GF30, PA6 GF50, POM GF20, PEEK CF30 are all in regular production. Tooling cost is higher — carbide only.
❓ Lead time difference between materials?
UHMWPE/HDPE/POM/PA6 same lead time (10-15 days for batch of 100 medium-complexity parts). PTFE +3 days, PEEK +7-10 days due to slower machining and import paperwork.
❓ Can you do prototypes in one material then production in another?
Yes — common workflow is POM prototype (fast, dimensionally stable for fit checks) then PEEK production. We adjust feeds/tolerances for each.
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