Understanding the Extrusion Thermoforming Process
There is no much difference between thermoforming and extrusion thermoforming processes. Since you have an idea about extrusion and thermoforming processes, it is easy to understand the extrusion thermoforming process. Usually this process is also called in line thermoforming. In this case an extrusion unit is attached to the thermoforming unit and the both processes are done in one step.
As in the case of thermoforming, the extrusion thermoforming process begins with forming a sheet of material that is formed by the extrusion process. If the material is thin (thickness is less than 1/16 inch), then it is fed in rolls in to the mold. If the material is thick (thickness is up to ½ inch), then it is fed in sheets.
Next step is to heat the sheet to a pliable temperature for ease of formation using electric heaters. Controlling this temperature is very important to get the desired results. Once heated, the sheet is flexible but not liquid or gooey. Without any winding, the thermoforming unit is fed by the sheets which are coming directly from the die. This is one of the main differences in thermoforming and extrusion thermoforming.
Now the soften sheet is placed on the mold and the desired shape is obtained by applying an external pressure.
Finally finishing processes such as trimming, drilling, etc. are carried out when the shape is cooled and hardened. Then the final product is obtained.