Can CNC Machining of Acrylic (PMMA) Achieve a Mirror Finish?

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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Yes, but not all plastics can achieve this. Dense, polishable materials such as acrylic, PC, POM, and PEEK, when processed with diamond tooling and polishing, can consistently reach surface roughness below Ra0.4μm, achieving a high-gloss, mirror-like appearance. Glass or carbon fiber-filled grades, due to exposed fibers, can only achieve a matte or satin finish, which we will clarify in advance.

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This is typically caused by excessive cutting heat. Acrylic has low thermal conductivity, so slow feed rates, high speeds, or dull tools cause chips to melt and stick to the tool, resulting in haze and stress-induced whitening. Our approach uses monocrystalline diamond tools with high RPM and small depths of cut, along with air cooling or minimal lubrication to dissipate heat. We leave a 0.05-0.1mm finishing allowance before final machining to prevent heat accumulation on already processed surfaces.

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Scratches on transparent plastic parts mostly occur during handling rather than machining. We isolate processes to prevent damage: protective films are applied throughout, independent trays prevent stacking between stations, and dedicated fixtures ensure proper positioning. Final inspection is performed under standard light boxes to check each unit's appearance. We guarantee a high-gloss, scratch-free, and flawless finish, not just "imperceptible" defects.

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Acrylic is more transparent, reaching up to 92% light transmission; when polished, it resembles optical glass and resists yellowing outdoors. Clear PVC looks similar after polishing but is less expensive and inherently flame-retardant (UL94 V-0), making it suitable for machine windows or protective shields that do not require the highest optical clarity.

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