Why PEEK, and why CNC machining specifically
PEEK (polyether ether ketone) is the high-performance plastic that keeps showing up whenever a metal part would be too heavy, a filled plastic would be too unstable, or both sterilizability and dimensional stability matter. It holds mechanical properties up to 250 °C continuous service, survives aggressive chemicals, and handles hundreds of steam autoclave cycles without softening. That combination is why PEEK dominates in medical instrumentation, semiconductor wafer handling, and aerospace bushings.
CNC machining is the right process when you need tolerance, surface quality, or complex internal geometry that injection molding can't produce economically below ~10,000 parts. Our typical PEEK customer is ordering 5–2,000 pieces with features in the ±0.02 mm range, often with specific material traceability (medical COA, Class VI, or ITAR) that a job shop running generic stock can't provide.
Virgin PEEK — the default for medical and pharma
Unfilled virgin PEEK (Victrex 450G is our standard stock, PEEK-Optima for implants) has the widest process window, the most predictable dimensional behavior, and the cleanest surface finish. Typical applications we see: surgical instrument handles, orthopedic trial components, catheter connectors, pharma fluid path fittings, and reusable medical device housings. For tissue-contact implants, we restrict to certified PEEK-Optima LT1 or CGF with full chain-of-custody documentation.
Machining parameters: we run virgin PEEK at ~200 m/min surface speed with sharp carbide tooling, low feed per tooth (~0.05 mm), and flood coolant. Compressed air alone is fine for short runs but coolant prevents the localized heat buildup that can cause surface pitting. PEEK springs back slightly after bore cuts, so we finish holes with a reamer sized 0.02 mm under nominal to hit tolerance.
30% glass-filled PEEK (GF30) — the structural workhorse
GF30 trades some ductility for stiffness. Modulus roughly doubles, creep resistance improves dramatically, and dimensional stability under load is excellent. Typical applications: structural brackets, semiconductor wafer carrier rings, gears running in dry service, pump impellers, and retaining clips. It's more abrasive on tooling — we replace endmills ~3× faster than on virgin PEEK — and leaves a slightly rougher as-machined finish (Ra ~1.6 µm vs ~0.8 µm on virgin).
30% carbon-filled PEEK (CF30) — thermal and tribological
Carbon-filled PEEK is stiffer than GF30 (~3× virgin), thermally conductive, and slightly electrically dissipative. Common applications: aerospace bushings and bearing cages, high-speed gears, and any part where a metal bushing would normally run but weight or corrosion forces a plastic alternative. For ESD-safe semiconductor handling, we specify PEEK-CA30 or equivalent electrically dissipative grades (10^6–10^9 Ω·cm resistivity).
Carbon fiber abrades cutting edges hard. We run CF30 with PCD-tipped tooling where economical, and accept ~4× faster tool wear on standard carbide for low-volume jobs. The finished surface is noticeably darker (nearly black) and has a satin appearance that customers often prefer visually.
Annealing — why most PEEK problems trace back to skipping it
Raw PEEK stock arrives with residual stress from extrusion. When you cut it — particularly when you rough large features and leave asymmetric material — the stress redistributes and the part warps. On thin sections, you can see 0.1 mm of dimensional drift days after machining. The fix is annealing: rough to +0.5 mm stock, soak at 200 °C for 2 hours with a slow ramp and cool-down, then finish machine. We run this as the default for anything over 15 mm thick or any part with deep asymmetric pockets. For flat plate work under 10 mm, we often skip annealing; the stress doesn't have enough cross-section to cause problems.
Tolerance, inspection, and documentation
We hold ±0.02 mm on critical features up to 50 mm envelope on virgin PEEK, ±0.03 mm on GF30 and CF30. Inspection is on calibrated Mitutoyo CMM for geometric features and on optical comparator for thread and radius checks. For medical or aerospace customers, every lot ships with material COA (linking heat number to your PO), first-article inspection report against your drawing callouts, and Certificate of Conformance. See the quality control process page for full documentation scope.
What to send us for a PEEK quote
Best-case: STEP file for geometry, PDF drawing with tolerances and GD&T, a specific PEEK grade callout (Victrex 450G, PEEK-Optima LT1, PEEK-GF30, etc.), and whether you need autoclave compatibility or biocompatibility certification. If you only know "PEEK," we'll propose the best-fit grade and document it in the quote. For semiconductor and medical work, tell us about packaging, cleanliness, and sterilization requirements up front — retrofitting those into an existing quote doubles the price and adds lead time.