Thermoforming
Thermoforming creates shapes from thermoplastic sheet that has been heated to its softening point. Applied vacuum or pressure draws or pushes the softened sheet over an open mold or form where it is then cooled to the conforming shape. The process of stretching the sheet over the form or mold causes thinning of the wall, especially along the sides of deep drawn features.
The Forming Cycle
The forming cycle in the thermoforming process begins by sealing the clamped, pre-heated sheet to the mold. If pre-stretching is required, it is accomplished with a partial vacuum, air pressure or plug assist. Then, while the sheet is still within the proper forming temperature range, vacuum or air pressure is applied to form the sheet onto or into the mold, or matching male and female molds come together to form the sheet. The sheet is held fast to the mold while the part cools. After the part has sufficiently cooled, it is removed from the mold, either manually or with automatic ejection systems, for post-forming work. The process is then repeated for next sheet.
Methods of Thermoforming
The thermoforming process can use single-step or multiple-step methods. Single-step thermoforming forms the heated sheet in one operation. Multiple step thermoforming involves pre stretching the heated sheet to help ensure an even distribution of material in the finished part.
Post-Forming
After the thermoformed sheet has been removed from the clamping frame, the part undergoes post-forming steps to bring the part into its final configuration. Waste or scrap around the edges is trimmed and holes are cut. Finishing often includes filing or sanding rough edges left behind by trimming and cutting tools, and polishing to remove scratches .Thin packaging lids and trays are easily trimmed using standard techniques.
