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Acrylic Polishing

Polished acrylic components are a very popular option for engineers when considering the design of optical devices. Acrylic is known for its excellent light transmittance, clarity and lack of color. Unfortunately, acrylic does not polish to an optical finish as easily as other materials such as polycarbonate, polysulfone and ultem. Interior surfaces such as tapped holes are difficult to achieve high clarity.

Acrylic polishing can give the best clarity and light transmittance of all the clear plastics. In both the extruded and cast form, acrylic is readily polished. Depending on configuration of the component, any of the four polishing techniques may be used; vapor polishing, buffing, flame polishing and direct machine polishing.

Vapor polishing utilizes a solvent vapor to flow the surface of the acrylic plastic. This method is good for internal features however its effect on acrylic is to produce more of a translucent finish. Typically, the better the machined finish, the better the end result with vapor polishing. Part cleanliness is critical. We are happy to vapor polish your machined acrylic plastic parts; however, for best results, both machining and acrylic polishing should be done by Connecticut Plastics.

Buffing of acrylic produces a good finish. Buffing is mostly used on exterior surfaces in larger components. Buffing utilizes a spinning cotton wheel with cutting compound. Being a mechanical process, the wheel leaves microscopic scratches and can leave a haze or uneven clarity on acrylic.

Flame polishing utilizes a hot flame to flow a surface. Much like spray painting, finish quality depends on the operator’s skill level. Done properly, flame polishing can produce some of the clearest finishes.

Direct machine plastic polishing utilizes specialty tooling to produce polished finishes directly from a machine tool. This method, while the most technical, can produce complicated surface profiles with near flawless finishes.

Acrylic polishing requires special skill since acrylic is a stress sensitive material and is fairly brittle. It can surface stress crack or craze due to poor machining or stresses setup from polishing. For the most stable, stress-free component, always specify an annealing cycle after machining, otherwise stress cracking will occur in service.