Injection Molding vs Compression Molding – Which Do You Choose?

The goal in the manufacturing of auto parts is to make products fast, consistently, and at the lowest possible cost. After decades of advancements, two popular methods for molding plastic into the desired shape have emerged: injection molding and compression molding.

What is the difference and which method is best for your business? Nova looks at the pros and cons of injection molding vs compression molding.

An Overview of Injection Molding

Injection molding is a process in which heated liquid material is “injected” into a mold. Once the material cools and hardens, it forms the shape of the mold. Nova injects melted plastic into molds to create auto parts or a single component of a larger part. It provides an easy, efficient and cost-effective way to mass-produce auto parts and components.

This method is also commonly used to produce glass, metal furniture, and other products.

An Overview of Compression Molding

The process for compression molding is slightly different. This method uses compression and heat to produce plastic parts and components. Instead of liquid plastic, thermosetting resins are poured into a heated mold cavity. The resin is forced down into the cavity until it fills the mold completely. The pressure is kept steady until the material has taken the shape of the mold.

Compression molding is a good method for basic plastic products that demand high-volume output.

Injection Molding vs Compression Molding

Now that you understand the basic molding differences, how do you decide which is better for your business? There are many pros and cons of injection molding vs compression molding.

Pros of Injection Molding:

  • Versatility – Injection molding is ideal for producing a variety of complex shapes. It is also highly versatile for producing most any part you need. There are around 20,000 plastic components that can be used for injection molding, making it suitable for a wide variety of auto parts or other plastic products, as well as products for different industries.
  • Versatility+ – You can also use multiple materials together in a process called co-injection for even more versatility.
  • Speed – Mass production becomes easier and faster as injection molding can be done completely through mechanical means. Once the mold is created, machines take over with no need to slow down or stop for adjustments in the assembly process. This method also allows for faster production changeover times.
  • Consistency– Injection molding is used to create even the most complex shapes at high volume and with consistent form and quality. Each part is an exact replica of the original design. It can even be used for multi-layer applications in order to tailor to specific mechanical properties or maintain a certain visual appeal. These results would be nearly impossible to produce with any other method, especially at the volume needed for mass production.
  • Cost Efficiency – Injection molding can produce parts at exceptionally high volume at a low cost. Although injection molds themselves do cost more, one mold can be used to produce hundreds of thousands of impressions. It is also easier to alter the cavity of the mold, in order to produce different parts, without having to update and re-machine the aluminum or steel tooling.
  • Gate feature – Injection molds use something called a “gate” through which the heated material is injected into the cavity (mold). The injection method allows the mold to have built-in features like tamper evidence (often used for bottle caps or food) without any post-molding actions, such as creating a “slit” in a bottle cap.
  • Less waste– Injection molding also produces less environmental waste as what little scrap that is produced can be re-melted and reused.

H3: Pros of Depression Molding

  • Cost-effectiveness – Depression molding is one of the cheapest ways to mass-produce plastic products and components. However, it does not allow for the same complexity of design.
  • Highly efficient – Depression molding generally requires low maintenance, making it easier to produce at a high volume. It provides the ability for more efficient color changeovers, with less downtime required as well.
  • No gate – Having a gate can reduce overall production time. However, the gate feature can also have an impact on the design, size, and aesthetics of the final product. It can even sometimes cause warping.
  • Low waste – Because there is no “gate”, the opening of depression molds is larger, which means the material gets into the cavity without any obstruction. This results in a low amount of material being lost in the transfer.

Cons of Depression Molding

While depression molding is an easy and low-cost method of producing products at high volume, it has limitations when it comes to complex geometric designs.

Takeaways: Injection Molding vs Compression Molding

Is injection molding better for your needs? There are a few things to consider.

  • Injection molding is ideal for more complex parts and components.
  • The injection method makes it easier to change sizes and is more efficient due to the ability to independently control the inner cavity.
  • It also allows for a higher degree of versatility, including the ability to use multiple materials and multi-layer applications.
  • Products can also be mass-produced quickly and with a high degree of consistency.

Compression molding is more suited for simple products that need to be manufactured at a very high volume.

Plastic Injection Molding Possibilities

There are many things to consider when weighing injection molding vs compression molding. Injection molding has become one of the most reliable, cost-efficient ways to mass-produce plastic auto parts and components. There’s a reason why it remains one of the most popular methods in manufacturing. Improvements in the quality, efficiency, and cost-effectiveness have made it even more accessible and profitable.

Nova produces some of the best products for a wide range of clients, including tier one automotive OEMs and tier two suppliers working with OEMs. We produce both complete parts and the components used to build larger systems.

We will work with you through the entire manufacturing process, from engineering and design to delivery of the final product. If you’d like to learn more about how injection molding can work for your business, Nova can be your partner. Request a free quote from us today and see how easy it is to get production rolling.

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