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Twin-Sheet = Vacuum thermoforming with 2 (twin) sheets

Whereas in thermoforming one plate is heated and then formed, in the Twin-Sheet process this is done with two sheets, either one after the other (American Twin-Sheet version) or simultaneously (European or Hombach version = simultanous Twin-Sheet foming).

This produces for the most part hollow bodies, either with a similar design to a tank (using two negative tools) or products similar to panels/housings, whereby one half of the mould is negative and the second sheet is positive, that is to say in the same direction as the first sheet.

Twin-Sheet Process (European / Hombach version):

1. Step
In the first production step, two sheets are inserted into the machine.
They are clamped in tightly and heated by heating elements.

2. Step
Once the material has reached the necessary forming temperature, the heating elements withdraw to the side and two mould halves are applied to the soft plastic material. At the same time a vacuum is produced between the plastic and the mould. This results in the component being formed.

As the two halves of the tool are also pressed together in the same process step, a hollow body (Twin-Sheet part) is produced from the two half-shells, using only pressure and the heat that has previously been applied.

3. Step
The part now cools down inside the tool. This can be accelerated,
where required, by flushing air through the cavity.

4. Step
Once the plastic is rigid enough to be released from the mould, the two tool halves move apart and the unfinished part can be removed. There is usually
a further processing step (e.g. CNC contour milling) following this manufacturing step.

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