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Your Guide to the Types of Plastic Molding

It’s always great to be aware of the types of plastic molding, which all include some advantages and disadvantages. Choose what’s best for your product needs. Read the details below.

Your Guide to the Types of Plastic Molding - KB Delta

There are different types of plastic molding and each is best suited for the end-product that is expected.

Therefore, your choice of which should be determined by the parts you’re out to make and your budget. The latter can be tied to the cost-efficiency of some molding processes more than others.

Now walk with us as we show you the different plastic molding processes to employ during manufacturing.


What is Plastic Molding?

Molding is a manufacturing process that involves the use of a mold or matrix to shape a liquid or pliable material. And when it comes to plastic molding, powder or liquid polymer (polyethylene or polypropylene) is often inserted into a hollow mold.

The placement of the powder or polymer in the mold allows the substance to conform to the shape of the mold.

Coupled with that, different heat and pressure ranges can be applied to the mold yield the end product. The amount of heat or pressure applied is dependent on the plastic molding process employed.


Types of Plastic Molding

The different types of plastic molding are:

1. Injection Molding

Injection molding is also a manufacturing process and it is employed in making custom plastic parts.

Here, molten plastic material is injected at high pressure into a metal mold. After the injection of the molten plastic into the mold, the mold is cooled before it is accessed to reveal the solid plastic.

The injection molding process can be compared to a Jello mold that is often filled before it is left to cool to aid in the creation of the end product.

Injection molds are made from aluminum and steel, hence they are expensive. The high effect of this cost is curbed due to the high number of parts that are created.

Here, the cost per part is economical and could be beneficial, especially if you’re making thousands of parts each year. That aside, it might take tooling around 12-16 weeks and a few more weeks for production.

​Uses of Injection Molding

Some uses of injection molding include:

Making High Volume Plastic Parts:

When plastic parts are to be made in high volume, injection molding is employed. A large injection molding machine can be used in molding car parts.

Coupled with that, there are small injection molding machines that aid in the creation of plastic parts for surgical applications.

Different plastic resins and additives can also be used during the process, which provides more flexibility in design.

2. Rotational Molding

Rotational molding is also known as rotomolding and it is used in producing products with large hollow parts.

In this manufacturing process, powder or liquid resin is placed in a metal mold and rotated in an oven. The rotation is carried out until there is a coating of the resin within the mold.

What’s more, the mold’s constant rotation creates a centrifugal force that allows the product to have even walls. And as the mold cools, the hardened plastic is transported from the mold.

Uses for Rotational Molding

Some uses of rotational molding include:

1. Creation of Large Hollow Plastic Products

Rotational molding is used in the creation of large hollow plastic products.

These products are not limited to marine buoys, storage tanks, bulk containers, car parts, pet houses, road cones, kayak hulls, recycling bins, and playground slides.

2. Molding a Range of Products

This process aids in molding a wide range of products.

The molds used in this process may include curves, inserts, contours, logos, and slots for metal or plastic inserts that will be inserted after the molding of the product.

Benefits of Rotational Molding

This manufacturing prevents the high wastage of material since excess material is re-used. The ability to re-use material makes this process economical and environmentally friendly.

3. Blow Molding

Blow molding is employed in making custom plastic parts with hollow, thin-walls. Its use is evident in products with uniform wall thickness and where the shape is of the essence.

In this process, the blow molding machine heats the plastic and injects air which blows the hot plastic like a balloon.

What’s more, the plastic is blown into the mold and as it expands, it takes shape of the mold.

Uses for Blow Molding​

Some uses of blow molding are evident in the creation of bottles, fuel tanks, and plastic drums.

This process is ideal for creating around a hundred thousand plastic bottles.


Your Guide to the Types of Plastic Molding - KB Delta


4. Compression Molding

Compression molding involves a plastic material being placed in a heated mold before it is pressed to get the desired shape. Upon being compressed to get the shape, the heating process helps the plastic to retain its maximum strength.

There is a final step that involves the cooling, trimming, and removal of the plastic part from the mold.

The compression molding process is more ideal for small parts that are to be produced in high volumes.

Uses of Compression Molding

Compression molding is employed in the replacement of metal parts with plastic parts.

The automotive industry, for instance, relies on compression molding since the final products it produces are strong and durable.

Benefits of Compression Molding

The cost of a compression mold is high due to factors such as the number of cavities, complexity of the pieces, the size of the parts, etc.

However, the cost of each part is low at high quantities. Hence, it’s better to resort to making parts in high quantities to benefit from the low cost.

5. Extrusion Molding

Extrusion molding can be likened to injection molding, but it is employed where a long continuous shape is needed.

Also, this method uses a die instead of a mold, which determines the product’s final shape. And in the creation of extruded parts, hot material is squeezed through the custom die.

Uses of Extrusion Molding​

One of the uses of extrusion molding in the creation of hoses, straws, PVC piping, and so much more.

Benefits of Extrusion Molding

The cost of this process is lower than other processes due to the die’s simplicity.

Despite this, there is a limitation to the product types that can be made using this process.

6. Thermoforming

Thermoforming involves the heating of a plastic sheet to a pliable forming temperature. The product is formed based on the shape of the mold before it is trimmed to the desired shape.

Uses of Thermoforming​

Thermoforming is employed in creating disposable cups, blisters, lids, trays, containers, clamshells, and other products.

It is worth noting that the cost of a thermoform mold is dependent on the size of the part that is to be created.



These are the different types of plastic molding to employ in your manufacturing process. They have their advantages and disadvantages, hence, choose one that improves your manufacturing process while offering a great cost.


Your Guide to the Types of Plastic Molding - KB Delta

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