CNC Machining PEEK Services: How to Pick a Supplier

• 1
  What matters before you send a PO
• 2
  PEEK grade vs what it does to your quote
• 3
  How to compare two PEEK machining quotes
• 4
  Why PEEK behaves differently from POM or aluminum
• 5
  Annealing and stress relief: the check most buyers miss
• 6
  Tooling, feeds and the tolerances you can actually hold
• 7
  Certifications, traceability and clean handling
• 8
  What drives price and schedule on a PEEK job
• 9
  7 steps to qualify a PEEK machining supplier

PEEK has a glass transition around 143 °C and a melting point near 343 °C. That heat resistance is the reason engineers pick it, and the reason it is hard to cut. The material does not conduct heat away like aluminum. Friction at the tool tip stays in the chip and the workpiece, so a dry cut can push the surface above the glass transition and leave a smeared, gummy finish.

Thermal expansion is the second issue. PEEK expands roughly three to four times more than steel per degree. A part machined at 25 °C and inspected at 25 °C will match the drawing. The same part measured after a warm afternoon in a non-climate-controlled shop can read 0.02–0.05 mm larger on a 100 mm length.

Moisture pickup is low, which is why PEEK holds size in humid or wet service. It is not zero. Thin sections can still move slightly after long exposure, so leave a small allowance if the part will sit in a sterilization cycle or a hydraulic system.

Chip control matters more than spindle speed. PEEK wants high surface speed and a firm feed per tooth so the cutter shears instead of rubbing. Too light a feed and you will see a polished, burned edge that looks fine in the machine and fails dimensional inspection.

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  Glass transition 143 °CKeep the cut below it or the surface smears.
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  High thermal expansionMeasure at a stable temperature, ideally 20 ± 2 °C.
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  Low moisture uptakeGood for wet service, not a substitute for annealing.

Extruded PEEK bar and plate carry locked-in stress from the mill. When you remove material, that stress releases and the part bends or grows. The effect is small on a 20 mm cube and obvious on a long, thin seal or a 200 mm frame. A shop that skips annealing may still hit the drawing on the first article, then miss it on part twelve.

A proper cycle roughs the part, leaves 0.3–0.5 mm of stock, anneals, then finishes. Annealing typically runs in steps up to 200–250 °C with a controlled ramp, a hold, and a slow cool. Rushing the cool-down just reintroduces stress. For unfilled grades, a two-stage cycle is common. Filled grades need a gentler ramp because the filler network can crack.

Ask for the furnace chart. A supplier who anneals in-house can show ramp rate, hold time and cool rate for your lot. A supplier who sends PEEK out for heat treatment loses control of the schedule, and that is where 2–4 days of lead time quietly disappear.

If the part is thick, the core cools slower than the skin. That gradient is where internal stress lives. A wall over 25 mm usually needs a longer hold, not a faster cut. Tell the shop the section thickness when you request a quote.

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  Rough, anneal, finishLeave 0.3–0.5 mm before the stress-relief cycle.
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  Ramp and cool slowlyA fast cool-down undoes the whole step.
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  Ask for the chartRamp rate, hold time and cool rate for your lot.

Unfilled PEEK is abrasive enough that high-speed steel will not last a shift. Carbide works, and diamond coating pays for itself on runs over a few hundred parts. Two-flute and three-flute end mills with a positive rake and polished flutes clear chips well. A low helix angle reduces the pull on thin walls.

For roughing unfilled PEEK, surface speeds around 200–400 m/min and feeds of 0.05–0.15 mm per tooth are a reasonable starting window. Filled grades run slower, often 100–250 m/min, because the abrasive filler dulls the edge. Climb milling leaves a better finish on the finished wall. Coolant is optional; if you use it, use air or a mist, not a flood that swells the chip and packs the flutes.

Holding ±0.005 mm on PEEK is possible on a stabilized part, but it is not the right default. For most seals, bushings and insulators, ±0.05 mm is enough. Tighten only where the function needs it, because every tight tolerance adds an inspection step and a re-cut risk.

Finishes land around Ra 1.6–3.2 μm as machined, Ra 0.8–1.6 μm with a careful finish pass, and Ra 0.2–0.8 μm on sealing faces. PEEK does not polish like metal. A light diamond pass leaves a matte, slightly textured surface, which is often exactly what a dynamic seal wants.

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  Diamond-coated carbidePays back on runs over a few hundred parts.
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  Slower speeds for filled grades100–250 m/min keeps the edge alive.
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  Do not default to ±0.005 mm±0.05 mm covers most seals and insulators.

PEEK shows up in spine implants, dental instruments, semiconductor fixtures and aerospace insulators. Those industries do not buy the same paperwork, but they all buy traceability. A general ISO 9001 shop can machine PEEK well and still fail a medical audit because it cannot show which lot went into which part.

ISO 13485:2016 is the standard that matters for medical work. It requires documented lot control, clean handling and a validated process. If your part touches a patient, ask how the shop segregates PEEK from steel and brass chips. A shared deburring area is a real contamination path, even with good intent.

IATF 16949:2016 applies if the PEEK part goes into a vehicle. ISO 27001:2022 covers information security, which matters if you are uploading CAD for a defense or medical program. Ask which certificate covers the PEEK cell, not just the company.

Traceability runs from the mill certificate to the job traveler to the final inspection report. If a shop cannot connect those three documents, a customer complaint six months later becomes a guessing game. That is the real cost of a missing lot number.

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  ISO 13485 for medicalLot control plus a validated, clean process.
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  IATF 16949 for automotiveRequired when the part enters a vehicle program.
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  ISO 27001 for dataCovers the CAD and drawings you upload.

PEEK stock costs far more than aluminum per kilogram, and the buy-to-fly ratio is worse because the material is often supplied in near-net bar or plate. A part that wastes half a plate wastes a lot of money. Designing a shape that nests well on standard stock sizes is the fastest way to cut cost.

Annealing adds a step and a day or two. It also saves money on rework, so treat it as insurance rather than overhead. The second cost driver is tool life. Filled grades can wear a cutter in a fraction of the time of unfilled PEEK, and the shop has to price that replacement into the job.

Lead time splits into three parts: material availability, machining and annealing, and inspection. Standard unfilled bar is usually on the shelf. Specialty compounded grades can take longer to source. Ask which grade is in stock before you promise a date to your own customer.

There is no minimum order quantity at GreatLight. One prototype and a 10,000-part run go through the same process plan, which is what keeps the first article and the production parts comparable. Quotation and a free DFM analysis come back within 12 hours, and production can start within 24 hours once the design is frozen.

That speed only helps if the process plan is right. A fast quote on a part that needs annealing, diamond tooling and a temperature-controlled inspection is not a fast part. Push on the plan, not the promise.

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  Nest the partStandard bar and plate sizes cut material waste.
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  Annealing is insuranceOne extra day beats a scrapped batch.
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  Freeze the design firstProduction can start within 24 hours after that.