The seed trays Thermo Pressure Forming Process
The clamp frame ensures the plastic sheet is held firmly in place during the pressure forming process.
Radiant heaters are normally used to heat the sheet which has been positioned over the aperture of the pressure forming machine. For thicker sheet both surfaces may need to be heated and more sophisticated machines allow this. Heaters move into position both above and below the sheet.
The hot sheet is transferred to the forming station, the upper mold (or pressure box) and lower mold are brought together and compressed air is introduced through the pressure box pushing the material against the mold.
Where a deep draw is required a top "plug" may be used to push material into the mold during the pressure forming process.
The material is allowed to cool. The cooling process may be shortened with blown air or even a fine water spray. The molding may then be released from the mold by introducing a small air pressure.
After pressure forming the part, any mold finishing may be performed, such as: trimming, cutting, drilling, polishing, painting, screening, etc.