Importance Of Tool Design For Precision Fabrication
Twin-sheet thermoforming can yield many interesting geometries in the “parting-line”. This is the area where the two sheets knit or weld together. That being said however, the weld is critical for the functioning of the part. The key concept in twin-sheet thermoforming is to compress the two starting sheets to about 50% of their original thickness during the forming process. That applied pressure aids in the heat-welding of the two sheets. Additionally, the applied pressure displaces material and effectively creates more surface area for the weld.
Accuracy Of Parting Line
Accuracy of the parting line (how it mates to the other mold) is critical in obtaining just the right amount of compression. The importance of the parting line is compounded by the fact that, as the material stretches, it thins, thus creating an inconsistent thickness. Design of the parting line on larger parts or parts with critical weld requirements is even more critical. The fabrication of the parting line has to execute that precision.