One common manufacturing process that can be used to make a wide range of products such as toys, parts for cars and aircraft, electronic components, and packaging, involves using a thin sheet of heated plastic and forming it into various shapes. Known as thermoforming, there are several different techniques, but all result in producing items made from molded plastic.
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.
The mechanical technique involves a mold that consists of two halves, a positive upper half and a negative lower half. The sheet of plastic is draped over the bottom part, heated until it is pliable, then the upper part of the mold is lowered onto it, which in turn squeezes the plastic into shape. Air is forced out through vents in the lower half.
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.
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.
The mechanical technique involves a mold that consists of two halves, a positive upper half and a negative lower half. The sheet of plastic is draped over the bottom part, heated until it is pliable, then the upper part of the mold is lowered onto it, which in turn squeezes the plastic into shape. Air is forced out through vents in the lower half.
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.
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 taught plastics molding techniques for over 15 years. He specializes in injection molding and thermoforming. If you are interested in learning more about plastic pallets for sale then he recommends you visit his friends at PTM: Custom Plastics Injection Molding Company.