PEEK CNC Machining Services: How to Choose a Supplier
PEEK is expensive and easy to scrap. This guide is for engineers and sourcing staff comparing PEEK CNC machining services. Read it and you can judge a shop by its tooling, annealing cycle, inspection data and quote terms instead of by its brochure.
In this article
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Key takeaways
What separates a capable PEEK shop from a risky one
Use this as a scorecard when you compare two or three PEEK CNC machining services.
| Check | Weak answer | What to look for |
|---|---|---|
| Tooling | General-purpose carbide, no notes | Polished carbide or PCD, positive rake, sharp edges |
| Speeds and feeds | Same program as aluminum | High surface speed, light radial cut, air blast |
| Annealing | Not mentioned | Documented stress relief before and after roughing |
| Tolerance | ±0.05 mm on a plastic part | ±0.005 mm only where the drawing needs it |
| Finish | Ra 3.2 μm and call it fine | Ra 0.8–1.6 μm stated per surface |
| Inspection | Sample check | 100% inspection before shipment, report on request |
| Certifications | ISO 9001 only | ISO 9001 plus the cert your industry requires |
| Quote terms | Price only | Grade, finish, tolerance and lead time in writing |
What a usable PEEK quote should contain
If any line is missing, the price you are comparing is not the same as the next one.
| Line item | Why it changes the price |
|---|---|
| Resin grade and filler | Unfilled, glass-filled and carbon-filled price differently |
| Stock form and size | Rod, plate or near-net shape changes waste |
| Tolerance per feature | Tight bands add passes and inspection time |
| Surface finish per face | Polished sealing faces add a second operation |
| Annealing cycle | Pre- and post-rough anneal adds furnace time |
| Inspection level | 100% inspection with a report costs more than sampling |
| Certification needed | ISO 13485 traceability adds documentation work |
| Lead time and shipping | Rush work changes scheduling and freight |
The short version
Choose a PEEK supplier on annealing discipline, tooling and inspection data, not on the lowest unit price. If the shop cannot describe its stress-relief cycle and its measurement method, the cheap quote will cost you a rejected batch.
Why PEEK breaks the habits of a metal shop
PEEK is a semi-crystalline thermoplastic with a melting point near 343 °C and a glass transition around 143 °C. It absorbs far less moisture than nylon or POM, and it holds stiffness at temperatures where most plastics go soft. That combination is why it shows up in seals, bushings, insulators, surgical instruments and aerospace brackets.
The same properties make it awkward to cut. Thermal conductivity is roughly a thousand times lower than aluminum, so heat stays at the cutting edge. If a programmer reuses an aluminum toolpath, the chip welds to the flute, the surface tears, and the part comes off the machine with internal stress that shows up two days later as a warp.
Chip evacuation matters more than spindle speed. PEEK chips are light, stringy and prone to wrapping. Compressed air through the spindle is usually better than flood coolant, because coolant gets absorbed at the surface and can leave the part looking cloudy after it dries.
A shop that machines PEEK every week will tell you this before you ask. A shop that treats it as another plastic will quote it cheaply and then ask for a tolerance waiver. The questions below separate the two.
How tight can PEEK CNC machining services actually hold
GreatLight works to ±0.005 mm (±0.0002 in) on PEEK when the drawing justifies it. That number belongs on bearing bores, seal grooves and mating faces. It does not belong on a 200 mm long cover, where thermal expansion alone will move the part more than the tolerance band.
The coefficient of thermal expansion for unfilled PEEK is around 47 μm/m·K. A 100 mm part that leaves the machine at 30 °C and is measured in a 20 °C inspection room shrinks about 0.047 mm. That is ten times a ±0.005 mm tolerance. Either you measure at controlled temperature, or you accept a wider band on long dimensions.
Wall thickness is the other limit. Thin walls under 1 mm deflect under clamping and cutting force, and PEEK springs back after the vise opens. Ask the shop how it plans to support the part: soft jaws, vacuum fixture, or a sacrificial backing plate. The answer tells you whether they have cut this material before.
For long, slender parts, consider designing in a machining allowance and finishing with a light pass after stress relief. It adds a day to the schedule and saves the whole batch.
Annealing, tooling and the parameters that hold dimensions
PEEK stock arrives with residual stress from extrusion. Rough machining removes material unevenly and releases that stress, so the part bends. The fix is a documented anneal: rough to leave 0.5–1.0 mm, anneal, then finish. Unfilled PEEK is usually annealed in steps up to about 200 °C, held, then cooled slowly. Glass-filled and carbon-filled grades need their own cycle.
Tooling comes second. Sharp, polished carbide with a positive rake and a large helix clears chips instead of rubbing them. Polycrystalline diamond (PCD) tooling lasts longer on glass-filled grades, where glass fibers abrade carbide quickly. If a shop quotes glass-filled PEEK at the same price as unfilled, ask which insert they plan to use.
Cutting parameters sit in a narrow band. Surface speed runs high, often 200–500 m/min for finishing. Radial depth of cut stays light, 0.1–0.3 × tool diameter, with a healthy axial depth. Feed per tooth is generous enough to cut rather than rub. Rubbing is what generates heat, and heat is what ruins the finish.
GreatLight runs 16 simultaneous 5-axis machining centers and 16 mill-turn centers, which matters for PEEK parts with angled ports or contoured seal faces. Fewer setups means fewer re-clamps, and every re-clamp on a plastic part is a chance to lose position.
Match the grade and finish to the application
Unfilled PEEK gives the best chemical resistance and the cleanest machined surface. It is the default for seals, valve seats and pump components. Glass-filled PEEK adds stiffness and creep resistance but is abrasive and tends to chip at edges. Carbon-filled PEEK is the stiffest and the most dimensionally stable, and it is the usual choice for structural brackets and wear parts.
Finishing options are limited compared with metal. PEEK can be bead blasted, tumbled or polished. Laser marking works and needs a minimum character height of 1.5 mm to stay legible on a dark, slightly translucent surface. Plating and anodizing do not apply.
If your part needs a specific surface roughness, put the number on the drawing per face. Ra 0.8–1.6 μm is a realistic machined finish for PEEK. Ra 0.2–0.8 μm takes a separate finishing pass and a longer cycle, and it should be reserved for sealing faces.
Ask the shop to quote the grade by name. The price difference between unfilled and carbon-filled PEEK is large, and a quote that says only "PEEK" is not a quote you can compare.
Step by step: vetting a PEEK supplier
- 11. Send the drawing with the grade namedState unfilled, glass-filled or carbon-filled PEEK, plus the tolerance and finish per face. A vague RFQ gets a vague price.
- 22. Ask for the machining planRequest tool type, cutting parameters and fixture concept. A shop that answers in specifics has cut PEEK before.
- 33. Ask about annealingLook for a documented stress-relief cycle before finishing, with furnace temperature and hold time.
- 44. Confirm the measurement methodAsk how tight features will be checked and at what temperature. CMM, optical or gauge, it should be named.
- 55. Check certifications against your industryISO 9001:2015 covers general work. Add ISO 13485:2016 for medical and IATF 16949:2016 for automotive.
- 66. Order one prototype firstGreatLight has no minimum order quantity, so a single part is a fair test of tolerance and finish.
- 77. Compare the report, not the promiseAfter delivery, read the inspection data. That tells you whether the shop can repeat the result at 10,000 parts.
Questions buyers ask about PEEK machining
Can PEEK be machined to the same tolerance as aluminum?
On short, stiff features, yes. GreatLight holds ±0.005 mm on PEEK where the drawing calls for it.
On long parts, thermal expansion and residual stress set the real limit. A 100 mm PEEK part can move about 0.047 mm between a 30 °C machine and a 20 °C inspection room, so tolerances on long dimensions should be relaxed unless the shop measures under controlled temperature.
Is annealing always required before finishing?
For anything with a tight tolerance, thin walls or an asymmetric shape, yes. Rough, anneal, then finish is the standard sequence for controlling movement.
Simple, thick, low-tolerance parts can sometimes skip it. Ask the shop to justify the decision rather than accept a blanket answer.
What is the minimum order quantity for PEEK parts?
GreatLight has no minimum order quantity and runs from one prototype to 10,000+ part runs.
Because PEEK stock is costly per kilogram, a one-off part carries a higher unit material cost than a nested batch. That is a material effect, not a setup fee.
How long does a PEEK order take?
Quotation and free DFM analysis come back within 12 hours. Production can start within 24 hours, and parts ship in 3–5 days.
If your drawing calls for pre- and post-rough annealing plus polished sealing faces, add furnace and finishing time to that window.
Which certifications should a PEEK supplier hold?
At minimum ISO 9001:2015. Medical device work generally needs ISO 13485:2016, and automotive work needs IATF 16949:2016.
If your drawings are sensitive, ISO 27001:2022 covers information security, and an NDA is available on request.
Can PEEK parts be plated or anodized?
No. PEEK is a polymer, so anodizing and plating do not apply.
Bead blasting, tumbling, brushing, polishing and laser marking are the realistic options. Laser marking needs a minimum character height of 1.5 mm to stay readable.
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