PEEK CNC İşleme: 2026 Tam Mühendislik Kılavuzu (Sınıflar, Toleranslar, Sterilizasyon)

What PEEK is and where it wins

PEEK is a semi-crystalline thermoplastic in the polyaryletherketone (PAEK) family, originally developed by Victrex (opens in new tab) in the 1970s and now produced by several global resin makers including Solvay, Evonik and Ensinger. The crystalline regions are what give it the heat resistance, chemical resistance and creep stability that put it on aerospace and medical bills of materials. Compared to a typical engineering plastic like nylon or acetal, PEEK behaves more like a soft metal: stiffer, dimensionally stable, but also fussier under the cutter.

• Continuous service temperature: 250 °C (with brief excursions to 310 °C). Stays above nylon, acetal, PTFE, polysulfone, and most other thermoplastics.
• Tensile strength: 90–100 MPa natural-grade, climbing to ~170 MPa for CF30 (30% carbon-fibre-filled).
• Chemical resistance: insoluble in nearly every industrial solvent, fuel, hydraulic fluid and weak acid below 60 °C. Hot concentrated sulphuric acid is one of the few exceptions.
• Biocompatibility: medical grades meet ISO 10993 (opens in new tab) and USP Class VI; widely used in implantable spinal cages, dental abutments and surgical instruments.
• Sterilisation: survives steam autoclave (>1000 cycles), gamma, EtO, and dry heat — see the matrix below.
• Radiolucency: nearly transparent to X-rays, useful for imaging-friendly implants and fixtures.

You spec PEEK when a part has to be lighter than metal, more dimensionally stable than other plastics, and bulletproof against heat, chemicals or sterilisation cycles. Below those thresholds, cheaper polymers (PEI, PPS, nylon) usually win on cost — see our material selection guide for the broader decision tree.

PEEK grades you can actually order

When a customer says "PEEK part" they almost always mean one of seven grades. The headline names (Victrex, Solvay KetaSpire, Ensinger TECAPEEK, Quadrant Ketron) are brands; the underlying chemistry is broadly similar within each grade family. Specify the grade by behaviour rather than brand wherever possible — that keeps your supply chain resilient.

The thermal-conductivity problem

PEEK's thermal conductivity is roughly 0.25 W/m·K — about 800× lower than aluminium. Every joule of heat the cutter generates stays in the workpiece, instead of dissipating through the part the way metal does. The consequence: a tool that runs cool on aluminium can push PEEK's local temperature past its 143 °C glass-transition (Tg), at which point the polymer softens, smears, and your dimension drifts as the part cools and contracts.

Three engineering levers control heat in the cut: (1) sharp positive-rake tooling that shears rather than rubs, (2) high surface speed with moderate feed so chips evacuate heat, and (3) compressed-air cooling that lifts chips and convects heat without thermal-shocking the part. The parameter tables below are tuned to keep the local temperature below 100 °C in normal operation. For sub-millimetre features in PEEK we route the job to our micro-machining cell where spindle speeds and feeds can be controlled even more tightly.

Pre-machining: annealing and drying

Extruded and moulded PEEK stock carries residual stress from the manufacturing process. If you machine straight from raw stock and remove material asymmetrically, the part warps as those stresses redistribute. Anneal first. The sequence below is what our shop runs for every PEEK production order:

1. 1

   1. Stock receipt + lot record

   Verify resin certificate of analysis. Log the lot number against the work order for full traceability.

2. 2

   2. Pre-anneal

   Slow ramp into a fan-circulated oven at 150–180 °C depending on stock thickness (see table below).

3. 3

   3. Soak

   2–10 hours hold at temperature. Long enough that internal regions reach soak temperature plus 30 min.

4. 4

   4. Controlled cool

   Same slow ramp down to room temperature. Rapid cooling re-introduces stress.

5. 5

   5. Drying (immediately before machining)

   4 hr at 120 °C to drive off absorbed moisture (PEEK absorbs 0.15–0.5% at typical shop humidity).

6. 6

   6. Rough machine

   Remove bulk material with generous stock left for finishing — typically 1 mm on diameters, 0.5 mm on faces.

7. 7

   7. Second anneal (tight tolerance only)

   Repeat the anneal step for parts targeting ±0.05 mm or better. Stress exposed by roughing can warp the finishing pass.

8. 8

   8. Finish machine + inspect

   Temperature-stabilised inspection room; measurements logged against the work-order traveller.

For tight-tolerance parts (±0.05 mm or better) we anneal a second time after rough machining — material removal exposes stress that pre-machining annealing couldn't reach. Dry the stock at 120 °C for 4 hours immediately before machining; PEEK absorbs 0.15–0.5% moisture from atmosphere and that swells nominal dimensions enough to wreck a precision fit.

Tooling, cutting parameters and cooling

PEEK is abrasive to cutting edges — especially CF30, which contains hard carbon fibre — so tool life is shorter than metals. Standard practice across our shop: carbide tooling for natural and GF grades, PCD (polycrystalline diamond) for CF30 production runs of more than 50 pieces. HSS is technically usable but rounds off quickly and produces poor finishes.

• Chip evacuation is non-negotiable. PEEK chips re-cut quickly and re-cut chips concentrate heat. Use chip-clearing pecks on every drilling cycle and high air-blast pressure (≥4 bar) on milling.
• Climb-mill, don't conventional-mill. Climb milling produces a thinning chip that exits clean; conventional milling rubs at the start of each pass and generates heat.
• Replace tools at the first sign of edge wear. A dulling tool rubs instead of cuts and the temperature spike is immediate. On CF30, plan PCD inserts for the runtime rather than running carbide to failure.

Workholding and fixturing

PEEK is stiff for a polymer but it's still a polymer: clamping forces that wouldn't touch a steel part will distort PEEK enough to wreck a tight tolerance. Two rules: support broadly and clamp gently.

• Use soft jaws machined to the workpiece diameter. A standard 3-jaw chuck on PEEK rod stock will leave three flat impressions and a tri-lobed bore. Custom-bore soft jaws for every job above ±0.05 mm tolerance.
• Prefer 6-jaw or collet for round stock. Force is distributed over more contact area and clamping pressure can be lower.
• Vacuum chucks for plate. For thin PEEK plate (≤10 mm), a vacuum chuck eliminates the screw-down clamping forces that warp the part during machining.
• Support unmachined sections. Wrap a tailstock onto long turned parts; use a follower rest if length-to-diameter exceeds 4:1. PEEK rod will deflect under cutter pressure more than you expect.
• Keep clamp pressure logged. For repeatable production we record collet/chuck pressure in the work instructions, not as a "tighten by feel" decision.

Tolerances achievable in production

Vendors who quote ±0.0002" / ±0.005 mm on PEEK are quoting metallurgical-tolerance numbers that PEEK can technically be machined to in a lab. In production, with thermal-expansion drift and post-machining stress relief factored in, here's what we actually deliver and stand behind. For projects that need the tightest practical tolerances, our precision manufacturing line couples ±0.005 mm machining with full CMM verification.

Common defects and how to prevent them

Sterilisation and medical-grade considerations

PEEK is one of the few engineering plastics that survives repeated medical sterilisation cycles, which is why it dominates re-usable surgical instrumentation, spinal implants and dental device markets. The cycle compatibility differs by method, though, and CF30 / GF30 grades aren't typically allowed in implant applications.

PEEK vs PEI, Torlon and PPS

PEEK is rarely the only option. Three other high-performance polymers compete for the same engineering slots; the deciding factors are usually temperature, sterilisation requirements and budget.

Cost expectations and sourcing tips

PEEK part cost decomposes into three roughly equal blocks: raw material (~35%), machine time including annealing and slower cutting (~35%), and QA + documentation, especially for medical (~30%). Optimisation lever depends on which block dominates your part.

• Design to standard stock diameters (5, 10, 12, 16, 20, 25, 30, 40, 50, 80, 100, 150, 200 mm). A 48 mm OD from 50 mm rod costs 30% less than a 52 mm OD that has to come from 80 mm rod.
• Skip exotic grades you don't need. If the application is short-temperature-cycle non-medical, natural PEEK is half the price of GF30 and PEEK-OPTIMA is 3× more again. Spec by performance not brand.
• Plan production batches. Annealing cycles are fixed-cost; a 10-piece run shares the same anneal as a 50-piece run. Per-unit cost drops substantially over 25 pieces.
• Provide drawings with thermal-expansion notes. If a critical fit needs to hold at a specific operating temperature, tell your supplier; tolerance can be biased so the part is on-target at use temperature rather than 20 °C inspection.
• Ask for the resin certificate. Even on industrial grades, the resin CoC tells you exactly which Victrex / Solvay / Ensinger lot you're getting. Critical for change-control and re-orders.
• Qualify your supplier before the production order. A first-article inspection (FAI) on 3–5 pieces flushes out any process issues at low cost. See our supplier qualification guide for the questions to ask.

DFM checklist for PEEK parts

• Minimum wall thickness ≥ 1.5 mm wherever practical. Thinner walls warp during machining and are fragile in service.
• Internal corner radius ≥ 0.5 mm. Sharp internal corners concentrate stress and crack in service or after sterilisation cycling.
• Thread depth ≤ 1.5× thread diameter for direct-tapped holes; use brass or stainless threaded inserts for higher pull-out load.
• Avoid press-fits over 0.05 mm interference on PEEK — it creeps under sustained stress. Use a tolerance fit + threaded fastener instead.
• Specify post-machining annealing if the part has asymmetric features or sees thermal cycling in service.
• Call out medical resin by full name (e.g. "Invibio PEEK-OPTIMA LT1, USP Class VI") on the drawing. "PEEK" alone is not a spec for a regulated device.
• Tell your supplier the operating temperature. Dimensions on the print are at 20 °C; thermal expansion at 80 °C operating temperature can be 0.03% per axis.

Frequently asked questions

These are the questions we hear most often from procurement and design engineers evaluating PEEK for a new part.