The sheet is then removed from the oven, placed over a mold, and forced against the mold through the application of a vacuum. The mold is usually at room temperature, hence the shape of the plastic becomes set upon contact with the mold. Because of the low strength of the materials formed, the pressure differential caused by the vacuum is usually sufficient for forming, although air pressure or mechanical means are also applied for some parts.
Typical parts made by thermoforming are advertising signs, refrigerator liners, pack¬aging. appliance housings, and panels for shower stalls. Because thermofroming is a drawing and stretching operation, much like sheet metal forming, the material should exhibit
FIGURE 18.11 Various thermoforming processes tor thermoplastic sheet. These processes are commonly used in making advertising signs, cookie and candy trays, panels for shower stalls, and packaging.
The sheet is then removed from the oven, placed over a mold, and forced against the mold through the application of a vacuum. The mold is usually at room temperature, hence the shape of the plastic becomes set upon contact with the mold. Because of the low strength of the materials formed, the pressure differential caused by the vacuum is usually sufficient for forming, although air pressure or mechanical means are also applied for some parts.Typical parts made by thermoforming are advertising signs, refrigerator liners, pack¬aging. appliance housings, and panels for shower stalls. Because thermofroming is a drawing and stretching operation, much like sheet metal forming, the material should exhibitFIGURE 18.11 Various thermoforming processes tor thermoplastic sheet. These processes are commonly used in making advertising signs, cookie and candy trays, panels for shower stalls, and packaging.
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