Manufacturing companies that make items such as electronic components, automobile and aircraft parts, packaging, and toys are amongst those which often use a process that molds heated, thin sheets of plastic into the desired shapes. This industrial process is called thermoforming, and it can be done in one of several ways, all of which result in the production of plastic, molded objects.
Different approaches may be used, depending the the size and shape of the items being molded, as well as the kind of plastic used, but the process follows the same basic principles in all of its forms. A plastic sheet is secured down and placed inside an industrial oven, where it is heated to a pre-determined temperature. When the plastic is soft, it is then stretched over the mold, cooled down using fans, and left to become rigid. There are several types of plastic that may be used, but the most common is HDPE, or "high density polyethylene".
A vacuum thermoform process involves the use of a temperature-controlled vacuum unit in which both the mold and the sheet of plastic are placed, with the latter positioned above the former. The plastic is heated until soft, then the mold is raised to contact it, while air is suctioned out from underneath, creating an airtight fit which forms the desired shape.
Pressure forming implements compressed air which is released out of the top of the thermoform machine and exerts a force anywhere from 15 to 300 pounds per square inch onto the softened plastic. The amount of force required depends on the size of the form. The plastic is pushed into or around the molded shape from the air pressure.
Mechanical forming is that which uses a double-mold that has a negative bottom half and positive top half. The plastic sheet is placed over the bottom of the mold, heated until it is pliable, and then covered with the top half of the form which squeezes the softened plastic in the particular shape being made. Air vents in the bottom piece provide ventilation.
Other types include pressure diaphragm forming which fabricates plastic parts using a vacuum and pressurized fluid. Also, twin sheet forming is used particularly for joining two parts that are separated by a hollow space, and it involves first melting two sheets of plastic then joining them together.
This process is often preferred over injection molding by manufacturers since it provides several advantages. For one, thermoform equipment costs a fair deal less than that used for injection molding, and secondly it is much easier and cost efficient to design and build a suitable prototype for this kind of forming.
Different approaches may be used, depending the the size and shape of the items being molded, as well as the kind of plastic used, but the process follows the same basic principles in all of its forms. A plastic sheet is secured down and placed inside an industrial oven, where it is heated to a pre-determined temperature. When the plastic is soft, it is then stretched over the mold, cooled down using fans, and left to become rigid. There are several types of plastic that may be used, but the most common is HDPE, or "high density polyethylene".
A vacuum thermoform process involves the use of a temperature-controlled vacuum unit in which both the mold and the sheet of plastic are placed, with the latter positioned above the former. The plastic is heated until soft, then the mold is raised to contact it, while air is suctioned out from underneath, creating an airtight fit which forms the desired shape.
Pressure forming implements compressed air which is released out of the top of the thermoform machine and exerts a force anywhere from 15 to 300 pounds per square inch onto the softened plastic. The amount of force required depends on the size of the form. The plastic is pushed into or around the molded shape from the air pressure.
Mechanical forming is that which uses a double-mold that has a negative bottom half and positive top half. The plastic sheet is placed over the bottom of the mold, heated until it is pliable, and then covered with the top half of the form which squeezes the softened plastic in the particular shape being made. Air vents in the bottom piece provide ventilation.
Other types include pressure diaphragm forming which fabricates plastic parts using a vacuum and pressurized fluid. Also, twin sheet forming is used particularly for joining two parts that are separated by a hollow space, and it involves first melting two sheets of plastic then joining them together.
This process is often preferred over injection molding by manufacturers since it provides several advantages. For one, thermoform equipment costs a fair deal less than that used for injection molding, and secondly it is much easier and cost efficient to design and build a suitable prototype for this kind of forming.
About the Author:
Genevive B. Mata has over 20 years of professional sales experience, 10 of them directly in the plastic pallets and materials handling industry. On her spare time she works on applied-sustainability projects. If you are interested in industrial plastic pallets, she suggests you check out her friends www.ptm.com/global.
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