PEI (Ultem) CNC Machining
PEI / Ultem CNC machining: Ultem 1000, 1010 and aviation grades with 24-hour aging route, diamond-coated tooling and +/-0.005 mm class capability.
Polyetherimide (PEI / Ultem) Machining
PEI is the machinable high-strength, inherently flame-retardant amorphous polymer behind cabin interiors, semiconductor fixtures and electrical insulators. Grade data below follows the Mechanical Design Handbook 6th ed. Vol. 1, table 3.4-55, cross-checked with the KGL engineering standard (2022-01-08).
Grades and Typical Data
| Grade | Density g/cm3 | Yield tensile MPa | HDT 0.45 MPa C | Class and typical use |
|---|---|---|---|---|
| Ultem 1000 | 1.27 | 104.8 | 210 | General purpose, flame V-0/5V: insulators, fixtures |
| Ultem 1010 | 1.27 | 104.8 | 207 | High-flow variant for thin-wall machined features |
| Ultem 9075 class | - | 94.4 | 190 | Aviation class: low smoke, chemical resistant, cabin parts |
| Ultem 9065 class | 1.32 | - | - | Aviation class: high impact, low smoke interiors |
| Ultem AR9100 | 1.32 | 119.9 | 209 | Aviation class, 10% glass fiber, flame and low smoke |
| Ultem CRS5311 | 1.52 | 165.4 | 217 | 30% glass fiber: structural brackets, fixtures |
| Ultem CRS5211 | 1.42 | 137.9 | 221 | 20% glass fiber: dimensionally stable housings |
| Ultem CRS5001 | 1.28 | 99.9 | 209 | Medical class, high flow, V-0 |
How We Hold Tolerance on PEI
- Roughing, 24-hour stress-relief aging, then finish passes, so residual stress leaves the part before final dimensions are cut
- Light low-speed cuts with diamond-coated tooling and cold-air cooling: PEI creeps under clamping force and melts if cut fast
- Conformal flexible fixtures spread clamping load instead of denting the part
Benchmark result: PEI aerospace parts held to +/-0.02 mm overall with surface finish below Ra 0.8, replacing 3D printing and injection molding. The stock for that program came direct from Röchling in Germany with mill-certificate traceability. Details in the PEI aerospace case study.
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Questions buyers ask
Is PEI (Ultem) flame retardant without additives?
Yes. Unfilled Ultem 1000 is inherently flame resistant with UL94 V-0 and 5V classification and low smoke generation, which is why it appears on cabin interior and electrical insulation callouts.
Which Ultem grade should I pick for a machined bracket?
Unfilled Ultem 1000 machines well and covers most fixture and insulator work. If the bracket carries real load, the 20% to 30% glass-fiber grades (CRS5211, CRS5311) roughly halve deflection with yield tensile to 165 MPa.
Can you certify aviation-grade PEI stock?
Yes. Aviation-class Ultem (9075, 9065, AR9100 families) is sourced direct from Röchling in Germany, lot-traceable to the mill certificate, with material certificates and our incoming inspection record on every shipment. On the benchmark wastewater program this traceability carried the FAI package without a single material deviation.