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.
There are multiple ways to thermoform plastic, but the general process is similar. A plastic sheet is held in place firmly as it's heated to the point of pliability in an industrial oven, it is then stretched over a mold, and cooled down with fans until it is firm. While there are multiple types of plastic that can be used, HDPE or "high density polyethylene" is the most popular. The technique used depends on the type of plastic and size of the mold.
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 is a method which implements the use of compressed air that forces the heated plastic sheet onto or into the mold. The air pressure released can range from 15 to 300 pounds per square inch, depending on how large the molded forms used are. The plastic is pressed into the shape of the mold, forming the desired object.
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.
There are multiple ways to thermoform plastic, but the general process is similar. A plastic sheet is held in place firmly as it's heated to the point of pliability in an industrial oven, it is then stretched over a mold, and cooled down with fans until it is firm. While there are multiple types of plastic that can be used, HDPE or "high density polyethylene" is the most popular. The technique used depends on the type of plastic and size of the mold.
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 is a method which implements the use of compressed air that forces the heated plastic sheet onto or into the mold. The air pressure released can range from 15 to 300 pounds per square inch, depending on how large the molded forms used are. The plastic is pressed into the shape of the mold, forming the desired object.
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 taught plastics molding techniques for over 15 years. He specializes in injection molding and thermoforming. If you are interested in learning more about plastic recycling solutions then he recommends you visit his friends at PTM: Custom Plastics Injection Molding Company.
Enregistrer un commentaire