Special production process for the fabrication of products from engineering plastics comprising two or more different types of plastic; illustrated by the example of producing bellows

摘要

Engineering plastics, such as PTFE, PTFE-glass compound, PTFE-carbon compound ..., require a different moulding pressure in the production of the semifinished article for optimum compression. In the case of blanks comprising two or more types of plastic, it is of course possible only to operate with one moulding pressure, which results in overcompression and undercompression of the individual types of material. In our problem solution, the semifinished blank is designed such that it is divided into the same number of segments as the number of types of plastic. These segments are then compression-moulded and sintered individually, achieving optimum compression. The plastic segments obtained are subsequently pre-machined in such a way as to produce a loose fit by the tongue-and-groove principle. Thereafter, two segments at a time are fitted together and welded by means of heating appliances and band heaters and are later finish-machined. An optimally compressed, absolutely homogeneous and durable plastic product is obtained; it can be used for the chemical industry, apparatus and plant construction, instrumentation and control engineering.