Several types of plastic injection molding are common in the industry
Resource: V1 Mold Technology
2022-10-28 11:06:40

Injection Molding

Injection molding is an extremely popular method for producing structurally sound plastic parts and components en masse using melted polymers and plastics. These are forced into a specially shaped mold cavity, left to solidify, and then extracted from the mold once cooled. It is incredibly efficient at prototyping and mass-producing goods like toys, phone parts, automobile parts and utensils.

Blow Molding

Blow molding follows a similar process to injection molding, where the melted plastic is poured vertically out of a barrel and down into the mold via a special tube that is then placed into the bottom of the barrel. From there, the action of the mold closing on it blows the plastic outwards so that it coats the inside of the mold to form the required shape. As it cools, the inside section hollows out, making it a great technique for bottles, food containers, and tubes.

Structural Foam Molding

This is an oft-chosen method for items that need thicker walls for greater durability and tensile strength. A small quantity of nitrogen or a chemical blowout agent is added to the melted plastic to thicken its consistency. The mixture foams as it enters the mold, forming a plastic "skin" that solidifies to form the walls of the item being constructed. This technique works with any type of thermoplastic that is capable of being injection molded.


Thermoforming takes a different approach to injection molding and other methods that use melted plastic. Sheets of pre-extruded, rigid plastic are heated and sucked back down into hollowed-out cavities. As the sheets cool, they take on the shape of the mold to form the finished piece. This is normally a more reasonably priced way of making plastic parts that have a smaller run than anything that is being mass-produced.

Rotational Molding

This method uses powdered plastic that is fixed around spokes that extend out from a central hub inside a specially prepared mold. As the mold rotates, the hub moves into a furnace room, where the plastic powder melts and sticks to the inside of the mold to form a more durable solution for the mold to be used in the furnace room. The hub then moves to a cooling area, where the hot plastic hardens into a hollow component that fits the exact shape of the mold. This is a slightly costlier process, but a good option for prototypes and pieces that need to be highly accurate but not produced in high numbers.

Compression Molding

Compression molding uses vertical presses as opposed to the horizontal ones found in injection molding. The plastic material is pressed between the two halves of the heated mold to form the required shape. It is then air-cooled, extracted, and passed on to quality control, where it is then used as a fuel source for a variety of applications. The fuel is then used for various purposes. This is a moderately costly process that yields excellent results and elevated levels of accuracy.

Gas Assist Moulding

Finally, gas assist molding uses gas injection molding techniques to create hollow plastic parts that the customer will need to create the desired molding material for the molding process to be completed in the first place. The hot plastic is partially added to the mold and immediately followed by a jet of high-pressure inert gas (e.g., nitrogen) to force it into the right place against the walls of the mold. The process is repeated until the required wall thickness is achieved.

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