Vacuum Forming is the process of converting flat plastic sheet into geometric shapes. Vacuum Forming is accomplished by heating the plastic sheet until it is pliable enough to be vacuumed either into a female mold or over a male mold. The part is then held in the mold by vacuum while it cools. The plastic is annealed by the heating process and a new memory is given to the plastic sheet by the thermoforming process, thereby locking in the shape given to the plastic by the tooling.
Pressure Forming is nothing more than Vacuum Forming with pressure assist to the forming process to enable crisper detail and sharper features. Pressure Forming utilizes pressurized air to push the heated sheet into the cavity. Pressure formed parts can resemble the detail of injection molded parts at a fraction of the tooling cost.
Twin Sheet Thermoforming
Twin sheet thermoforming is the process of thermoforming a product by using two separate sheets of material formed, either simultaneously or one after the other, and uniting the two formed sheets into a single, dual walled part. The two individual components are fused together through the application of tremendous pressure which forces two molds together, thereby fusing the materials together. Different colored material and even totally dissimilar materials can be used in the twin sheet process.