The thermoplastic injection moulding is basis for all other spraying casting processes and at the most frequent used plastics processing technology at all.
Until 1956 one used piston injection moulding machines. The today usual in-line screw injection moulding machine draws usually plastics into form of granulates from a funnel into the flights, divided and shears it. The friction warmth resulting from it provides in connection with the warmth supplied by the heated cylinder for a relatively homogeneous melt. This collects itself before the point of the back-yielding snail.
In the so-called injecting phase the snail is pressurized back hydraulically or by mechanical Kraft. The melt under high pressure (usually between 500 and 2000 bar) is pressed by the nozzle pressed in slightly to the tool and the runner into the form-giving cavity of the spraying casting tool kept at a moderate temperature. Reduced a pressure works as reproduction still so long to the melt, until the fluid soul is rigid (frozen). Thus the volume shrinking developing with the cooling becomes to a large extent balanced. Accuracy to size and the desired surface quality are reached by this measure. Afterwards the rotation of the snail begins. While the Schussgewicht for the following shaped part is prepared in this way, the shaped part in the tool knows still cooling. The tool opens and ejects the finished shaped part.
The dead head can be separated. Also dead headless injection moulding is possible with appropriate dead head organization. Shaped parts fall from the tool or by handling devices out of the tool are taken and arranged put down or equal a subsequent treatment supplied.
Spritzgussteile can be manufactured with weights between some Milligramm and approx. 50 kg. The finished thermoplastic plastics are modified by additives and fillers for the spraying casting processing and the later use. Among them also very hard inorganic fillers are very often such as glass balls or glass fibers.
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