Plastic pressure forming starts with an extruded sheet of plastic secured in a clamp frame. Next, the plastic moves into an oven and heated until it reaches a malleable temperature.
Afterward, we removed the clamped sheet from the oven. It is then sandwiched between a pressure box and the forming tool.
To reduce the amount of material thinning in parts with a deep draw, plug assists are often used. This pre-stretches the plastic sheet and reduces the amount of material thinning that can occur.
A Plug Assist is called for when using a negative mold with pre-stretching. The mold is pushed into the heated plastic sheet to create a seal on the edge. At the same time, the plastic sheet pushes into the mold using the plug assist.
As it enters the hot sheet, air between the sheet and the mold is compressed, causing the sheet to undulate around the plug. The hot plastic sheeting is prevented from directly contacting the cooler mold as the sheet stretches. This ensures maintaining a consistent material dimension.
Providien uses a thinner starting gauge plastic, which reduces both raw material and processing cost.
Forming the Part
With the sheet secured, a strong vacuum applies up to 85 PSI pressure to the back of the sheet. The suction pulls the sheet over the tool and formed.
The vacuum pressure forces the part to match the contours of the tool. Following forming, the part cools on the tool. The part is free of molded stress and ready for finishing.
Trimming the Part
The newly pressure formed part gets processed through a 5-axis CNC trimming station. In the CNC station, it is expertly trimmed to its final dimensions. Further fabrication steps may be performed at this point before the final product is ready for release.