PMMA is the best choice for transparent prototype. PC is incomparable to PMMA. There are transparent materials among PC too, but they have to be fumigated to be transparent, and the effect is not as good as the PMMA. CNC machining PMMA prototype can be totally transparent after burnishing, and the transparency can be 95%.
Low hardness plastic is called soft plastic. The hardness ranges from 30-90. It is relatively soft at room temperature. Soft plastic has excellent elasticity, slip resistance, and vibration damping performance. It is necessary during the development of most products. The common soft plastic includes TPE、SBS、TPU、TPV、rubber（SBR）and silica gel, and they are widely used during the process of soft plastic rapid prototype. TPR is softer than rubber, but in terms of tensile strength, fatigue resistance and mechanical performance, it is inferior to perduren.
The principle of 3D printing SLS prototype is stacking. With computer-assisted design and fabrication, the solid powder will be made into 3D parts, and without the limitation of the size and structure. The whole process needs no tools or jigs. As long as the tray is big enough, one person can operate multiple printers, and print multiple parts each time, reducing the cycle time of prototype manufacturing.
3D printing SLA prototype uses liquid photosensitive resin, then undergoes laser curing by layering, and finally stacks up and forms the prototype. By burnishing, electroplating and spraying, the prototype will be done. The advantage is the smooth surface, and high precision, with tolerance between ±0.1mm.
During the process of 3D printing SLM prototype, the metal powder is melted by the heat of laser, and the prototype will be done after cooling and congealing. Equipped with 500 watts fiber optic, collimating system and high precision scanner, the precise facula and optical quality can be got. Therefore, 3D printing SLM prototype is preciser than SLS. The only difference is that the materials are titanium alloy, stainless steel, aluminum alloy, cobalt-chromium alloy or steel, so the price is higher.
CNC turning parts are mainly used to manufacture helicoid parts, like bearings and wheels. By operating the CNC machining program, the cutting of internal and external of columns, cone, surface, whorl and end face, slot turning, drilling, reaming, and fraising can be done automatically with high precision. But for CNC, no matter it is manual programmed or automatic programmed, the technology analysis of the target parts has to be done before the programming, like the cutting point, manufacturing route, as well as manufacturing plan, suitable cutter and quantity of cutting. Finally, only the accurate control of the precision can produce qualified products.
