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What are the four types of molding?

Views: 5     Author: Site Editor     Publish Time: 2022-08-23      Origin: Site

The manufacture of polymer products involves several different processes, each with specific benefits and applications. Despite the growing popularity of additive manufacturing (often referred to as 3D printing), most rubber and plastic parts are manufactured using traditional molding processes.

This blog post is designed to help you understand how different molding processes can be used to produce durable, high-quality rubber and plastic parts to meet the unique needs of your next project. After a brief definition of molding processes, we will break down the benefits and applications of the four types.

precision molding

What is molding?

Molding is one of the five core processes in rubber and plastic manufacturing, along with casting, molding, machining, and additive manufacturing. While they have some similarities, the processes are very different.

The molding process uses pressure and heat to fill the cavities of the mold, the rigid frame, also known as the matrix. The raw material (usually a flexible raw material such as plastic, glass, or ceramic) is held under pressure until it cures or vulcanizes (i.e., begins to harden)—the advantages of forming include greater accuracy, versatility, and efficiency.

Molding differs from casting in that a liquid or molten polymer is poured into a mold and cured to form the part. No pressure other than gravity is used to fill the mold and form the part. Advantages of casting include durability and greater design complexity - however, it may not be possible to cast large parts.

4 Types Molding Processes: Applications and Advantages

Molding serves various industries and offers superior quality, sustainability and adaptability. Understanding the types of molding processes is critical to ensuring the success of your next project. Here are some of their main applications and advantages.

1. Compression Molding

Compression molding processes are used to make rubber and plastic parts. In rubber compression molding, a preformed portion of rubber is placed into a heated mold, which is then closed and held under pressure until the rubber forms a cavity and vulcanizes. Vacuum-assisted compression molding is similar but is placed under a vacuum to remove any gases and ensure optimal mold filling and shape adhesion.

Compression molding offers several advantages over other processes, including low tooling costs and fast lead times. However, the process requires manual mold and product handling, resulting in slower cycle times.

2. Melt Molding

When applied to thermoplastic materials, compression molding is called melt molding. The polymers are heated above their melting point for this manufacturing technique to take on a liquid form.

The resulting polymer is then allowed to cool and cure in the form of a mold. When temperature conditions are appropriately controlled, melt molding can provide better mechanical properties than compression molding.

3. Transfer Molding

In transfer molding, the material is loaded into a chamber before being forced into the mold. The chamber can be in the molding machine or in the mold itself.

Transfer molding can be used for either rubber or plastic, although the process is slightly different for each material. Mold geometry is slightly more complex than compression molding but less costly than injection molding.

4. Injection Molding

The injection molding process can be used for both thermoplastic and thermoset materials. Injection molding machines inject molten polymer materials into closed molds at high pressures and speeds. Although these molds can be more expensive to manufacture, the process can ultimately provide finished parts at high productivity.

To learn more about the different characteristics and benefits of injection molding complex polymer components, check out our recent blog post on this topic.

Whether you are looking to produce high-volume production or need a short run of custom products, finding a manufacturing partner with various molding processes is the best option. A manufacturer like Shengqi, with multiple precision molding process facilities to meet your specifications, efficiency goals, timelines, and budget, is your best precision molding supplier.


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