Assignment 7
Objective
Understanding the process
Types
Thermoforming
To understand and practice the process of Vacuum thermoforming.
Thermoforming is a general term that refers to the process of transforming a plastic sheet into a 3-dimensional shape by using heat, vacuum, and pressure.
The process includes heating a thermoplastic sheet to its softening point, then sheet is stretched across a single-sided mold and then manipulated. Then, it cools into the desired shape.
-
Vacuum Forming The specific process that involves forming a part by heating and stretching the plastic across a mold using a vacuum. Normally the mold is open and the force involved with forming the sheet is limited to about 15 psi.
-
Pressure Forming This process adds a pressure box to the tooling package. It utilizes both vacuum and positive air pressure. This process generates as much as three to four times the forming pressure as vacuum forming does. Therefore, fine details such as surface textures can be formed on the mold without incurring excessive extra costs
-
Mechanical forming The thermoplastic sheet is mechanically forced into or around the mold by direct contact. Typically, a core plug will push the sheet into the mold cavity and force it into the desired shape.
Exercise
To exercise the process of vacuum thermoforming, I made a mold in the form of a face mask. The mold was made by carving the PU foam.
The machine was turned ON, and the sheet was loaded to get heated.
​
The mold was placed over the vacuum mesh, and the machine bed was raised by pulling the lever.
​
Soon as the mold touched the heated sheet, the vacuum button was pressed to generated the vacuum.
​
When the sheet was formed completely, the machine was switched OFF and the sheet was taken out.
