What is Plastic Molding?
Definition: Plastic molding (also known as polymer molding or plastic shaping) is a process in which the heated molten or softened plastic is introduced into a mold cavity and it is allowed to solidify to gain the desired shape.
Plastic molding is used to manufacture various components like plastic cups, electrical plugs and switches, cookware handles, blower fan blades, plastic bottles, dinnerware, radio/TV cases, etc.
Types of plastic molding processes
Different types of plastic molding process are listed below.
- Extrusion molding
- Compression molding
- Transfer molding
- Injection molding
- Blow molding
- Slush molding
- Plastic lamination
Let me tell you few interesting things about all these plastic shaping (or plastic forming) processes.
#1) Extrusion molding
Extrusion molding (also known as polymer extrusion or plastic extrusion) is a process of manufacturing long products that have constant cross section, by forcing the softened polymer through a die opening.
By using an extrusion molding process, the products like rods, pipes, sheets, wire insulation coatings, etc can be manufactured.
Extrusion molding is also used to manufacture small shaped components which can be cut from the long extruded part.
#2) Compression molding
Compression Molding is a plastic molding process in which the heated polymer is placed into an open heated mold, and then it is compressed to get the desired shape.
Compression molding process is generally used for molding of thermosetting plastics.
The raw material used for compression molding can be either in powder form, liquid form or in the form of pallets.
In plastic compression molding, the plastic is preheated with the help of infrared heaters or ovens which softens the plastic and helps in proper deformation.
#3) Transfer molding
Transfer molding is a process in which a polymer is preheated and loaded into a holding chamber (called pot) and then it is forced into a preheated mold cavity to get the desired shape.
Transfer molding process is similar to the compression molding process, but the difference is that in compression molding, the raw material is placed in an open mold. While in transfer molding, the raw material is kept in a closed holding chamber.
#4) Injection molding
Injection molding (also known as polymer injection molding) is a process in which the molten polymer is forced into a mold cavity under a high pressure, which is then allowed to solidify to get the final component.
By using injection molding process, a high production output rate can be achieved with automated work.
Also the final component ejected from the mold is well finished and it does not require more post production work.
#5) Blow molding
Blow molding of plastics is a manufacturing technique that is used to create hollow plastic parts by filling the heated plastic tube with air until it occupies a desired shape.
By using blow molding, the parts like bottles and containers with different shapes can be manufactured.
Plastic blow molding is also used in manufacturing a wide range of small and large components like small water bottles, shampoo bottles, as well as large storage drums, tubes, etc.
Polymer Calendering is a polymer molding method in which the heated polymer is passed between the two rollers that apply heat & pressure and force the polymer into a sheet.
This plastic sheet can be further passed through other rollers for extra surface works like embossing, surface finish, adding gloss, etc.
Calendering is generally used for manufacturing PVC sheets as well as sheets of other polymers.
Polymer calendering is also used to give finishing work to the already manufactured plastic sheets.
Thermoforming of plastics is the operation in which a thermoplastic sheet is heated to its softening point, stretched into a single sided mold and then it is holded in a place till it cools and solidifies into a desired shape.
Thermoforming of plastics is mainly used for manufacturing of food packing boxes, toys, trays, aircraft windshields, etc.
There are 3 types of thermoforming operations used for molding of plastics.
- Vacuum thermoforming
- Pressure thermoforming
- Mechanical thermoforming
#8) Slush molding
Slush molding process is a type of plastic molding process in which hollow plastic components are manufactured.
In slush process, the molten polymer is poured in the mold and it is allowed to cool for a very short time such that only the outer surface polymer gets solidified.
The excess molten polymer is then poured out of the hollow shell.
And finally, the hollow component is obtained when the halves of mold are separated.
Slush molding is used to manufacture various hollow components like rain boots, toys, shoes, dolls, etc.
The main advantage of slush molding is that it uses less material as compared to that of solid components. Thus the final molded part is lighter and cheaper.
#9) Plastic lamination
Plastic lamination is a process of applying a thin plastic sheet on any item to make it tear-proof and waterproof.
Lamination process is used to cover and protect the frequently handled items like menus, identity cards, printed instructions, etc.
Lamination helps in preserving the material for years without losing color and without causing any damage to it.