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5 Types Of Plastic Molding For Custom Plastic Products Manufacturers

5 Types Of Plastic Molding For Custom Plastic Products Manufacturers

There are two types of plastics: thermoplastic and thermo-rigid. Thermoplastics are meltable and thermoplastic are not. The difference is in how the polymers are formed. Polymers, or chains of atoms, are like one-dimensional strings in thermoplastics, and if they melt, they can take on a new shape. In thermo-rigid they are three-dimensional networks that always retain their shape. A wide variety of processes are used to form or mold plastics, some only serve for thermoplastics, others only for thermo-rigid and some processes serve both.

Liquid Silicone Rubber (LSR) Injection Molding Manufacturers
Liquid Silicone Rubber (LSR) Injection Molding Manufacturers


Extrusion is a molding process that begins with “raw” plastic material such as granules, powder, or pearls. A hopper feeds plastic into a rotating chamber. The chamber, called an extruder, mixes and melts the plastic. The melted plastic is forced out through a die and takes the shape of the finished product. The item falls on a conveyor belt in which it is cooled with water and cut. Some products that can be manufactured by extrusion include sheets, film and tubes.


Injection molding

Injection molding uses the same principle as extrusion. The raw plastic is fed from a hopper into a heating chamber. However, instead of being forced to pass through a die, it is forced into a cold mold under high pressure. The plastic cools and solidifies, and the product is cleaned and finished. Some products made by injection include butter packaging, bottle caps, toys and garden furniture.


Blow molding

Blow molding uses air injection after a plastic has been extruded or injected. Extrusion blow molding uses a die that creates a hot plastic tube with a cooled mold around it. Compressed air is injected through the tube to force the plastic to take the shape of the mold. This allows manufacturers to create continuous and uniform hollow shapes, but to have to injection-mold each of them. Injection-blowing also uses an injection mold, but instead of obtaining a finished product, the mold is an intermediate step in which the plastic is heated to be blown to its final shape in a separate cold mold.


Compression molding

Compression molding is the process of taking a pre-specified volume of plastic, placing it in a mold, and then using another mold to crush or compress it into the first mold. The process can be automatic or manual and is suitable for both thermoplastic and thermo-rigid materials.



Thermoforming is the process of heating a plastic film without melting it, softening it enough to take the form of a mold against which it is pressed. The manufacturer makes the plastic take the desired shape using high pressure, vacuum or a male mold. After the finished product has cooled, it is removed from the mold and the remnants are recycled to be used in new film.


Plastic injection molding process

Injection molding is one of the main methods of making plastic. The first step in the injection molding process is to feed plastic granules into the hopper, which then feed the granules into the cylinder. The barrel is heated and contains an alternate screw or ram injector. An alternative screw is normally found on machines that produce smaller parts. The reciprocating screw crushes the granules, making it easier for the plastic to be liquefied. Towards the front of the barrel, the reciprocating screw drives the liquefied plastic forward, injecting the plastic through a nozzle and into the empty mold. Unlike the barrel, the mold is kept cold to harden the plastic into the correct shape. The mold plates are held closed by a large plate (referred to as a movable plate). The movable plate is connected to a hydraulic piston, which exerts pressure on the mold. The closed clamping of the plastic mold prevents it from escaping, which would create deformations in the finished parts.

Liquid Silicone Rubber (LSR) Injection Molding Manufacturers
Liquid Silicone Rubber (LSR) Injection Molding Manufacturers

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