Custom Injection Molding vs. Compression Molding: What’s the Difference?

custom injection molding

Molding is one of the most common manufacturing processes involving materials such as plastics, rubber, and similar polymers. However, it is essential to note that molding processes vary from each other. For example, custom compression and injection molding, the two most popular molding processes, remain mysterious to some people. And the following guide offers a basic overview of both methods.

injection mold

What Is Custom Injection Molding?

We’ll start with a consideration of how injection molding works. Custom injection molding is the most utilized manufacturing process for fabricating plastic parts. It is a plastics manufacturing technology capable of very high production volumes.

Injection molding is a process that applies the “injection” technique.

The process is carried out by injecting liquid plastic into a stainless-steel mold, where the product is gradually formed under high pressure. The mold is outfitted with various customized cavities to form the product. When the melted plastic has been injected, the material begins filling out the cavities and the rest of the mold. The products are left to cool and are later ejected by pins.

Because of its versatility, injection molding is regularly used for various applications. Everything from automotive parts to small, intricate pieces of surgical equipment can benefit from the process. Its other applications involve medical devices and dental parts, food & beverage packaging, engineering prototypes, cable assemblies, and window and door components.


What Is Compression Molding?

Compression molding is more suitable for medium-sized production, usually rubber and silicone. The compression molding tool makes even stiff, high-durometer rubber materials perfectly vulcanized and dimensionally stable.

In general, compression molding is defined by applying heat and pressure. Although this is similar to injection molding, the procedure is completely different. The compression molding process involves heating a mold and placing preheated material inside. After that, the mold is closed to heat and compress the contents into the desired shape. The heating process—also known as curing—ensures the final product maintains integrity and shape. Once cooled, products are removed from their molds.

Compression molding gives strong and durable products. Thus, many industries tend to employ this technique for their applications. For example, some typical compression molding applications include body armor, circuit breakers, plastic dinnerware, and electrical and electronic components.


Custom Injection Molding vs. Compression Molding

 custom injection molding vs. compression molding

Injection Molding: Pros & Cons

(1) Advantages:

  • Efficient and Fast Production of Uniform Components

Injection molding is a high-volume production method that can produce millions of parts per machine annually.

Injection molds have shorter cycle times and fewer secondary operations. Additionally, multi-cavity tooling injection molding allows multiple parts to be produced every cycle, which benefits high-volume part production.

  • Enhances Versatility and Customization

Equipped with various customized cavities, this molding type is highly versatile. Besides, consumer products can be easily updated.

  • Low Production Costs

With shorter cycle times and repeatable manufacturing, injection molding lends itself to lower scrap and piece prices due to tooling efficiency.

  • Supports Complex Mold Designs

The desired shape can be simple to complex with the help of computer-aided design for specialized items.

(2) Disadvantages:

Custom injection molding requires a large investment cost. Foremost, the price of the machine itself can be high. Secondly, as it requires very high plastic injection pressures, the mold must be built to withstand these pressures. This adds cost to the tooling. Also, it’s costly for a small number of products. But you can always find a reliable supplier instead of investing in the production lines alone.

Custom injection mold design costs may be high, but keep in mind that these costs are easy to recoup over long and large production runs.

Compression Molding: Pros & Cons

(1) Advantages:

  • Ease of Maintaining Mold Tooling

Since the process often employs high-strength materials, many products created via compression molding are sturdier and more resilient than those manufactured using other molding processes.

  • Low Initial Tooling Costs and Investment

The cost of molding equipment is low, so the initial investment in compression mold is less expensive.

  • Enable More Efficient Color Changeovers

Like injection molding, compression molding is considered to be cost-effective and highly efficient. What’s more, it provides more color changeovers to satisfy unique requirements.

  • Preserve The Mechanical and Chemical Properties of Materials

Compression molding can make composite panels using sheet and bulk molding composites. These panels do not have continuous fiber-impregnated sheets, but rather chopped fiber strands distributed throughout the bulk material.

(2) Disadvantages:

The disadvantage of molding is that mold manufacturing requires secondary machining. And the molding cycle of the whole production process is long and inefficient, and it has a large physical consumption for the staff. Limited by the press, it is most suitable for mass production of small and medium-sized composite products.

custom injection molding


This article presented the topic of custom injection molding vs. compression molding, explained what they are, and discussed the different attributes of each.

The type of molding best suited for your project will depend on many factors. When those factors point to injection molding as the most effective option, partnering with an experienced service provider makes a significant difference in the outcome that you experience, influencing factors from quality to speed. Find expert help with custom injection mold solutions on your project today from Abery and explore the advanced options available to you now.