During compounding, plastic raw materials are melted with fillers or additives, extruded into thin strands and then cut into granulate. This process allows the characteristics of the plastics to be adapted for special applications, for in-stance by improving the sliding friction properties or in-
creasing electrical conductivity.
Pressure and temperature-regulated extrusion is a continu- ous production process in which plastics are plastified in an extruder and then forced at pressure through a specially shaped die. The cross-section of the resulting geometric shape equates with the used die or calibration. The extrusion process is an efficient method of manufac- turing semi-finished products, also known as stock shapes, with large wall thicknesses and dimensions. The portfolio of semi-finished products comprises rods, tubes and plates in a wide variety of dimensions and colours.
Injection moulding is a highly productive forming process for the mass manufacture of finished components capable of immediate commercial use. The plastic is melted using an extruder, plasticized and then injected at pressure into the injection moulding tool. The cavity of the tool deter-mines the shape and surface structure of the finished com-ponent. The injection moulding process is usually only economical for large production runs due to the tooling costs involved.
Compression moulding / sintering
Compression moulding and sintering are used to produce stress-relieved semi-finished products and custom castings with a minimal tendency to warp. The so-called compres-sion moulding technique is used to manufacture semi-fin-ished products. The process uses powdered particles which are pressed at high temperature under pressure into a mould. Because of the amount of time involved and the materials used, this process is relatively labour intensive and costly. Unlike the compression moulding method, the matrix compression or direct forming technique allows the direct production of off-tool custom castings. As a special mould is required, this process is generally only profitable for a production run of around 1,000 pieces.
Pressureless custom casting has proved to be a particularly successful method for the production of bulky thick-walled components which are almost fully finish processed. Alongside custom casting, cast polyamide semi-finished products can also be produced using the semi-finished
product casting technique in the form of plates and rods with substantially larger dimensions than when using the extrusion method.Semi-finished products and custom castings produced us-ing this method have a lower intrinsic stress level than ex-truded products. Casting methods are ideally suited for small and medium-sized production volumes in a weight range of 0.5 to 900 kg.
Machining is the fastest, most economical way to arrive at a finished plastic component, in particular for small produc-tion runs. Using the machining technique, finished com-ponents with extremely close tolerances can be produced from engineering and high-temperature plastics. This en-tails the use of CNC milling machines, lathes or saws fitted with special tools for machining plastics to shape the fin-ished parts from plastic stock shapes or pre-produced injec-tion-moulded components.