With the extruding (v. lat.: extrudere = out-push, -) plastics or other viscous hardenable materials in a continuous procedure float by a nozzle are pressed. In addition the plastic becomes - which Extrudat - first melted by an extrusion (also worm extruder called) homogenized by means of heating and internal friction and. Further in extrusion the pressure necessary for flowing through the nozzle is developed. After withdrawing from the nozzle the plastic solidifies usually in a water-cooled calibration. The creation of a pressure causes thereby the resting against the calibration profile. Whereupon often still another cooling stretch follows. The cross section of in such a way developing geometric body corresponds to the used nozzle or calibration.
One calls a similar procedure, which comes during the hot shaping from metals to the employment, which is based on the same transforming principle, extrusion.
That together brought from kind-same or strange plastic melts before leaving the profile nozzle also Coextrusion is called.
By extruding can for example smooth plates, pipes and profiles also over the length constant cross section, in addition, arbitrarily for a long time and mostly on roles wound courses of plastic foil or hoses to be made.
With respect to the anglo-saxon world one differentiates frequently also into the product groups:
Pipe & tube (pipe and hose)/film & Sheet (foil and plate)/profiles (profiles) /Fasern (Fibre).
Plastic containers such as bottles or doses in addition, fuel tanks are manufactured by extruding. An extruded hose is enclosed by a form and blown by means of compressed air to the tool wall. Therefore one speaks of the extrusion blow moulding.
To lay on in the building of forms the procedure of the extruding for it used on the forms an even layer of a paste, which hardens with air contact. The hardened paste is further processed afterwards by manual or automatic procedures, so that accuracy to size is ensured.
- Over the processing of plastics outside - still further materials are processed by the process of the extruding (see under extrusion).
Products of the extruding technology appear in the following areas of application (selection):
Building industry (high and foundation engineering), automobile industry, aircraft industry medical technology, furniture industry (above all kitchen or office furniture), building of fairs, packing, agrarian employment, applications of hoses and granulation.
Usual materials of the processing are:
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» Electron beam melting
» Extruding (finishing technique)
» Extrusion blow moulding