Does PEI (Ultem) Need Drying Before Machining?

Yes. Acrylic is one of the few plastics that can achieve a mirror finish directly through cutting. We use single-crystal diamond tools for precision machining, followed by flame polishing or diamond grinding. Surface roughness is consistently controlled within Ra0.4μm, delivering a high-gloss appearance free of scratches or defects, resembling a mirror. No secondary coating is required. For batch production, identical parameters are used to ensure consistent mirror finish quality.

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Temperature and cost guide selection. PEI offers long-term service up to 170°C (Tg 217°C), inherent flame retardancy, and lower cost than PEEK, ideal for aerospace interiors, electrical insulation, and medical device structural parts. PEEK withstands long-term temperatures up to 250°C with better chemical and wear resistance, suitable for high-heat, corrosive, or implant-grade applications. For temperatures below 170°C, PEI is usually more economical.

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The criteria for judgment are consistent: high gloss, high-shine surface, no scratches, and no defects. The difference lies in the process—aluminum parts rely on anodizing and polishing, while plastic parts use diamond cutting and flame polishing or mechanical polishing. When aluminum and plastic parts are mixed in the same batch, we standardize color swatches and gloss samples to avoid visual discrepancies between the two materials on the same product.

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Appearance quality is a core strength. We use a three-stage control process: during machining, sharp tools with high RPM and shallow cuts prevent tool marks and roughness; between processes, all parts are film-wrapped and transferred in individual stations to avoid stacking scratches; before shipping, each piece is inspected under standard light sources against strict criteria for glossy, scratch-free, and blemish-free finishes. Batch consistency is guaranteed by fixed parameters and fixtures, not manual picking.

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Common choices are PPSU, PSU, PEI, and PEEK. PPSU withstands over 1,000 cycles at 134°C with the best impact resistance; PEI is heat-resistant to 170°C at a lower cost; PEEK has the highest heat tolerance and is suitable for implant-grade applications. PC and ABS are unsuitable for repeated high-pressure sterilization, as they are prone to stress cracking or yellowing after just a few cycles.

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