The principle behind thermoforming products is quite simple in theory. Heat a sheet of Polystyrene (HIPs), Polypropylene or similar plastic sheet or film and by process of vacuum and air pressure, pull the sheet down over a solid mould to obtain the desired shape. Anything from a car dashboard to a key fob can be vacformed this way.
The majority of thermoforming production is by Roll Fed machines. Sheet Fed machines are used for the smaller volume applications. Larger production units have in house sheet extrusion equipment. Because of the complexities in synchronising sheet extrusion equipment and the thermoforming machines, the two processes can be carried out independently of each other. The extruded sheet being produced in advance of production schedules.
With very large volumes a fully integrated in-line, closed loop system can be justified. The line is fed with plastics raw material, with extruders fed directly into the thermoforming machine.
The plastic sheet is softened at the heating station. It then indexes to the forming station where the mould tools are located. The forming of the sheet is by a combination of air pressure and male core plugs. Certain designs of thermoforming tool facilitate the cropping of the article being formed within the thermoforming tool.
The high volumes of articles being produced demand that a parts stacker is integrated into the forming machine. Once stacked the finished articles are now packed into boxes for transportation to the end customer. The separated skeletal is either wound onto a mandrill, for subsequent chopping, or passes through a chopping machine which is in line with the thermoforming machine.