Thermoforming forming press

Products, such as point-of-purchase and berry box rigid containers often require multiple punch steps. The first punch forms holes or slots in the product. The second punch separates the product from the trim. Although multiple punches can be accomplished on a single trim press, there is always a concern about the first punch trim-out causing problems with the second punch. As a result, tandem trim presses are usually used (Fig. 16.15). Set up and alignment of two presses often take substantially more time than the set-up time of the thermoforming forming press. 

Dow s patented scrapless forming process is identified as the SFP process. An extruder produce a biaxially oriented sheet (Chapter 5). In turn the sheet is slit and cut into square blanks. These blanks are heated and pressed into circular disc with a lip. Immediately or latter after reheating, the disc is thermoformed into a shape such as a cup. 

Thermoforming consists of forming a preheated plastic sheet or film into a desired shape against a mold surface. Forming can take place pneumatically or mechanically. In the first case, a differential air pressure is used, either vacuum on the mold side, compressed air on the other, or both. In the second case, the preheated sheet of material is pressed into the mold using either a preform, a plug, or by a combination of both. Viitually all thermoplastics can be thermoformed. However, because of limitations in the material characteristics, some can only be used for simple shapes with small draw ratios. 

Compressed air thermoforming is a technique borrowed from sheet steel processing its main use in plastics processing is in plastic cup production. Machines are also coming into use for the production of engineering components, such as computer covers. A flexible-pressure pad is used to press the hot sheet into the mold cavity, with the aid of an air cushion maintained under pressure. Compared with vacuum forming, this... 

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. 

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