The Types of Plastic Molding

The most popular techniques in plastic molding are rotational molding, injection molding, blow molding, compression molding, extrusion molding, and thermoforming. We’ll cover all these techniques in this guide to help you discover the best process to make your part or product.

Rotational Molding
Rotational Molding, also called rotomolding, is a manufacturing process for producing large hollow parts and products by placing a powder or liquid resin into a metal mold and rotating it in an oven until the resin coats the inside of the mold. The constant rotation of the mold creates centrifugal force forming even-walled products. Once the mold cools, the hardened plastic is removed from the mold.

Very little material is wasted during the process, and excess material is often re-used, making it economical and environmentally friendly.

Common Uses for Rotational Molding
Rotational molding is commonly used to make large hollow plastic products like bulk containers, storage tanks, car parts, marine buoys, pet houses, recycling bins, road cones, kayak hulls, and playground slides.

Rotational Molds Are Highly Customizable And Cost Effective
The mold itself can be highly intricate to facilitate the molding of a wide range of products. Molds can include inserts, curves, and contours as well as logos and slots for plastic or metal inserts to be placed after a product is molded.

Tooling costs are lower with rotational molds than injection or blow molds. The results are lower start-up costs and cost-effective production runs even when producing as few as 25 items at a time.

Injection Molding
Injection molding is the process of making custom plastic parts by injecting molten plastic material at high pressure into a metal mold. Just like other forms of plastic molding, after the molten plastic is injected into the mold, the mold is cooled and opened to reveal a solid plastic part.

The process is similar to a Jello mold which is filled then cooled to create the final product.

​Common Uses for Injection Molding
Injection molding is commonly used for making very high volume custom plastic parts. Large injection molding machines can mold car parts. Smaller machines can produce very precise plastic parts for surgical applications. In addition, there are many types of plastic resins and additives that can be used in the injection molding process, increasing its flexibility for designers and engineers.

​Injection molds, which are usually made from steel or aluminum, carry a hefty cost. However, the cost per part is very economical if you need several thousand parts per year.

With injection molding, tooling usually takes 12-16 weeks with up to four more weeks for production.

Automotive Mold