POLYCARBONATE MACHINING & VAPOR POLISHING
Polycarbonate polish is the most commonly polished transparent plastic. It is second only to acrylic in clarity. Machining Polycarbonate is readily polished via vapor polishing and is typically the method of choice for most applications. Vapor polishing can be used to enhance component features on materials such as polycarbonate or acrylic. Vapor polishing is ideally suited to the polishing polycarbonate of small features and offers improvements to internal and external surface finishes. Minor scratches and other small surface irregularities can be removed from machining polycarbonate parts by vapor polishing. The process is performed with a chemical vapor, which attacks the surface of the plastic and smoothes it. When done properly, vapor polishing can provide optical quality finishes. Methylene chloride vapor is normally used in the process for polycarbonate polish. The vapor is created by heating a container with methylene chloride to the boiling point. utilizes vapor to flow the surface of the component.The parts are exposed to the methylene chloride vapor for less than three seconds.The whole process must be performed in a closed and well ventilated room, that prevents the operator from coming in contact with the fumes. Parts must not come in contact with liquid methylene chloride. After the polishing process, parts must be allowed to dry, in order to evaporate the methylene chloride. The polycarbonate polish process requires specialized equipment and handling to achieve the desired results. With precise machining by a skilled plastic machinist, an optical quality component can be achieved. Conversely, if the machining has been done improperly, vapor polishing can actually make the situation worse and the feature takes on an opaque white look. Dirt particles and all foreign matter, such as oils and greases should be removed from the machining polycarbonate by carefully cleaning and drying before polishing. Finally the parts are gradually heated in an air circulation oven and kept at 120 ºC for one hour to release surface stresses and to evaporate the entrapped methylene chloride. Polycarbonate is a stress sensitive material. While polycarbonate has great impact resistance, such things as simply overtightening screws can cause stress cracking or crazing. For the most stable, stress free component always specify an annealing cycle after machining. Vapor polishing always requires an annealing cycle afterwards otherwise stress cracking will occur in service.