Vacuum forming

Vacuum forming is a casting process.

Benefits

The vacuum forming process is characterized by applying a vacuum to stabilize the mold. In contrast to other methods, one can largely dispense with the drafts of the cast workpieces that are intended for easier lifting of the mold from the model here. A further advantage of the method is a high dimensional accuracy at the same high surface quality. The burr at the division levels to the core marks and is also low. Can be cast by all known present state of castable metals and alloys, the maximum vergießfähige weight, depends only on the casting not on the method. The vacuum casting process tolerance deviations of up to 0.3 to 0.6 percent can be observed.

Implementation

As a model to submit a duration model is used, with which one produces the lost mold of quartz sand. The solidification of the molding sand is carried out by applying a bar pressure of about 0.3 to 0.6 in the interior of the mold. To this end, the model is provided with small nozzle holes, so that a film of 0.05 to 0.1 mm thick deep drawn, ie can be pulled over the half of the model. The film is heated prior to thermoforming means of a heating coil a few seconds, which is plastically deformable. During deep drawing, the film comes true to contour and close to the model.

The free-flowing, binder-free silica sand is then poured onto this contour. After the formation of the pour cup and the feeder of the molding box is covered with a further foil. The compression of the molding sand is done by the vacuum between the two sheets, which causes the generation of frictional forces between the sand grains so that an inhibition of the movement between the sand grains occurs. Then you can remove the mold from the pattern generated. Both sides, upper and lower case are shaped in this way after the folding form the mold cavity, which is then poured out. Until the complete solidification of the casting after casting the vacuum between the two films is maintained in the upper and lower box. The vacuum is only parked for removing the finished casting. The quartz sand is then reusable. With this method, small to large lot production.