plastic injection mold setup

What Is Two-Shot Injection Molding?

Sometimes called dual-shot, overmolding, or even multiple-shot molding, the two-shot injection molding process is preferred for companies looking to create parts, components, substrates, and finished goods with different colors.

Without the two-shot process, companies would be forced to mold one substrate or part at a time. They would then need to add an assembly step, or steps, to join two or more substrates together. By molding two separate substrates in a single process, companies can save considerable time and money. The result is a low-cost, durable, and visually appealing product.

Let’s look into how this process works when compared to traditional plastic injection molding. 

The Two-Shot Injection Molding Process Explained

Injection mold

In plastic injection molding, a thermoplastic resin is gravity-fed from a hopper into a conveyor. A heating coil controls that conveyor’s temperature. As the heat along the conveyor increases, the resin is ground by a large screw controlled by a separate motor. The heat of the conveyor and grinding of the screw turns the resin into molten plastic, which is directly deposited into a mold. It is then force-cooled, and the substrate is ejected from the mold.

With two-shot injection molding, there’s an extra step. After the first substrate is molded and cooled, it is moved to another part (mold or chamber) of the machine. This movement might be robotic or involve an operator or technician manually moving the substrate or part.

The substrate is then rotated 180 degrees and set in place. Once secure, the second thermoplastic resin goes through the same heating and grinding process and is bonded to the original substrate. Just like with single-shot injection molding, the new combined part is cooled and ejected from the mold.

Industry Applications

Just like traditional plastic injection molding, there are infinite consumer, commercial, and industrial applications for two-shot injection molding. In fact, it would be nearly impossible to find an industry that doesn’t use this process when manufacturing finished goods.

Examples of everyday items that are made with two-shot molding including soft-touch staplers, power tool grips, electric toothbrushes, seals, and gaskets. For industrial applications, the automotive and aerospace markets are heavily reliant on two-shot injection molding to lighten the weight of their frames.


The immediate benefit of the two-shot molding process is the savings in time and money. The ability to mold two or more components in a single process means companies save considerable money and labor by avoiding multiple assembly tasks and QC inspection steps.

The overall benefits include:

  • Part Savings: Companies can eliminate redundant and repetitive work tasks by molding multiple substrates into a single finished good.
  • Increased Quality: Eliminating assembly steps means companies can avoid issues with misaligned or out-of-tolerance components. Two-shot molding is an exacting process that guarantees part tolerances.
  • Increased Efficiency: Two-shot injection molding eliminates the need for manual process steps such as assembly, welding, or joining two separate components.
  • Repeatability: Eliminating manual assembly processes means eliminating the high costs of human error. With two-shot molding, you produce the same part with the exact dimensional tolerances.

Learn More About Two-Shot Molding

Do you want to learn more about two-shot molding? Talk to our experts at Silver Basis Engineering. Founded over 20 years, we provide a wide array of award-winning services, including two-shot injection molding, to manufacturers worldwide. Contact us today to schedule a consultation with one of our specialists or to request a quote.