Sanding and Polishing
The flawless gleam of a mirror polished Aluminum/Stainless Steel part, the smoothness of a semi-gloss or matte part, the high shine of a PMMA part— all are signs of a job done well. And all are made possible by the application of sandpaper. Without proper sanding, any imperfections will be magnified when the final finish coat (e.g. painting) is applied. Therefore, we often apply sanding finishing to prepare a good surface for painting or other finishing procedure.
There is a thumb rule of sanding: Start with a grit coarse enough to quickly remove surface imperfections and graduate to finer ones. Each successive grit erases the scratches left by the previous coarser one, until the scratches become almost invisible to the eye and undetectable to the touch.
Vapor polishing is a frequently-used method of polishing plastic to optical clarity. Parts’ internal and external features can be done well by applying vapor polishing. Normally, the part is exposed to a chemical vapor which causing the surface of the plastic to flow thereby improving the surface smoothness and improving surface transparency. Polycarbonate (PC) is the typical vapor polished material, whose transparency is very similar to the high-polished PMMA’s transparency.