Industries which produce items such as packaging, automobile and aircraft parts, toys, and electronic components often employ a manufacturing process that consists of heating thin sheets of plastic and applying them to molds to form numerous shapes. This method is called thermoforming, and it can be done in several ways which all produce molded plastic 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 temperature-controlled vacuum unit is used for the vacuum thermoform technique. The mold is placed in the unit with the sheet of plastic directly above it. As the plastic is heated, the mold is raised until it contacts it directly, as air is pulled out from underneath it, resulting in a airtight connection, that enables the shape to take form.
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.
A mechanical process uses a two-piece mold that has a top and bottom part. The plastic sheet is laid on top of the bottom, or negative half of the mold, and is then heated until soft, at which point the top or positive mold is lowered onto it, squeezing the plastic into the desired shape, and allowing air to escape through vents in the bottom piece.
Pressure diaphragm forming can be used to produce plastic parts by means of pressurized fluid and a vacuum. Twin sheet forming is useful for joining two plastic parts divided by a empty space, it works by melting the parts, and then attaching them to each other.
Many manufacturing companies prefer the thermoform approach over injection molding because it offers several advantages. The biggest benefit is that it costs much less for the equipment than it does for injection molding machines, in particular for larger sized objects. Developing a suitable prototype is also more easily facilitated and affordable for thermoform processes.
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 temperature-controlled vacuum unit is used for the vacuum thermoform technique. The mold is placed in the unit with the sheet of plastic directly above it. As the plastic is heated, the mold is raised until it contacts it directly, as air is pulled out from underneath it, resulting in a airtight connection, that enables the shape to take form.
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.
A mechanical process uses a two-piece mold that has a top and bottom part. The plastic sheet is laid on top of the bottom, or negative half of the mold, and is then heated until soft, at which point the top or positive mold is lowered onto it, squeezing the plastic into the desired shape, and allowing air to escape through vents in the bottom piece.
Pressure diaphragm forming can be used to produce plastic parts by means of pressurized fluid and a vacuum. Twin sheet forming is useful for joining two plastic parts divided by a empty space, it works by melting the parts, and then attaching them to each other.
Many manufacturing companies prefer the thermoform approach over injection molding because it offers several advantages. The biggest benefit is that it costs much less for the equipment than it does for injection molding machines, in particular for larger sized objects. Developing a suitable prototype is also more easily facilitated and affordable for thermoform processes.
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 plastic pallet suppliers, she suggests you check out her friends www.ptm.com/global.
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