Thermoforming machines

A compressed air thermoforming machine is essentially a deep drawing machine with a controlled heat shield, except that, in place of an upper ram, a pressure bell is used. The heated rubbery material is pressed into the molding tool using a differential pressure of up to 100 psi. After cooling and demolding, the formed part is precisely shaped. 

Another type of machine uses three or more stages. They are usually built on a horizontal circular framed that rotates (Fig. 5-14). The rotary table 

Other stations can be included, such as decorating. Multicavity molds are used extensively. As is typical of injection molding and extrusion machines (Chapters 2 and 3), they can have sophisticated computer controls to ensure proper operation of all machine and material functions. 

Trimming of plastics, if not performed correctly, can be damaging to formed parts and slow down or stop the output. Tools for trimming include shear discs, steel rule dies, and saws. The cutting action can be done with the usual punch press, as well as press brakes and other devices. Punch and 

In-line thermoforming production lines, particularly those being fed directly from an extruder, have to be completely synchronized, or inferior parts result, and/or the cost of the operation goes up. For example, if the trimmer operation has to be slowed down, the extruder output has to be reduced. In fact, a slowdown can result in a shutdown if the extruder cannot operate at the slower speed required. All functions and stations have to be properly interrelated. 

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Safety at injection moulding machines Safety at blow moulding machines Safety at thermoforming machines... 

Injection and extrusion are the main processes used. Thermoforming, machining and welding are used for secondary transformations. 

Code of Practice for Safety in the Use of Thermoforming Machines , British Plastics Federation, London, 1987. 

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 feeding directly into the thermoforming machine. 

Injection Molding Machines Blow Molding Compresion Presses Transfer Presees Thermoforming Machines Molds Dies Auxiliary Equipment Liquid Depeneing Systems Impregnators Plotters... 

Exxon Chemical researchers changed their PP to overcome its deficiencies. They developed a proprietary catalyst and reactor technology to extrude thermoformable sheet and film. Their material has a rubbery plateau region and a high dynamic modulus so that it is processable in conventional thermoforming machines. 

Sheet is an extruded product that is greater than 10 mils in thickness (below this the product is identified as film), 40 mils being typical. Resin is extruded through a die and passes through a cooling roll stack and conveyed to nip rolls, after which sheet is wound on rolls or cut and stacked or conveyed directly to a thermoforming machine. Sheet width is usually between 2 and 7 ft. 

Fig. 2. Schematic of small thin-gauge thermoforming machine (Kiefel GmbH, Freilassing, Germany). Used with permission of Hanser Publications.

Heavy-Gauge Machines. There are several common designs for heavy-gauge thermoforming machines. The simplest and most widely used is the shuttle machine (Fig. 5) (14), where the sheet, cut to size and palletized, is loaded, one... 

Sag bands or metal rods that mn length of the thin-gauge oven have been used for polymers that sag excessively when heated. Some heavy-gauge shuttle thermoforming machines are equipped with ovens that completely seal the sheet between the heaters. These ovens are equipped with vacuum and compressed air, so that the sheet is lifted when it begins to sag. 

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