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Vacuum forming

Forming process where a first plastic sheet is heated and then pulled down against a mold by vacuum.

Illustration of Vacuum forming

The process

Before processing can begin, a mold [1] is designed with the same shape as the finished workpiece. The mold is usually designed with a draft angle of 3 degrees to facilitate removal of the finished product from the mold. The plastic disc [2] to be processed is then clamped and a heater [3] then heats up the plastic sheet to a temperature suitable for processing. A vacuum pump is then activated to create a vacuum in the space [4] between the plastic sheet and the mold. This leads to the plastic disc being drawn down against the mold and assuming the shape of the mold.

Shaping is often done with a mobile platform for the mold which is pressed up against the heated plastic before vacuum is activated.

Advantages and disadvantages
In comparison with alternative methods
Cost effective: Low tool cost
Useful for large batches
Design Flexibility
Deeper pieces may get warped
Possible distortion of the bubbles and air pockets
Slower cycle
Limited forms can be produced