What metal should you use for injection molding molds?

Injection molding is an efficient and versatile manufacturing method that creates complex and precise parts by injecting molten material into a mold cavity. In order to produce high-quality parts at a low cost and with a fast turnaround time, choosing the right material for the molds is critical. Molds made from the wrong material can wear out quickly, warp, corrode, or fail to provide the necessary detail and surface finish. In this blog post, we will discuss the main options for metal injection molding molds and their key properties and applications.

Aluminum

Aluminum is one of the most popular materials for injection mold tooling due to its high thermal conductivity, low density, and good machinability. Aluminum molds can withstand high temperatures and pressures and offer good dimensional stability and corrosion resistance. They are also relatively affordable and easy to modify or repair. However, aluminum is not suitable for some types of resins that are highly abrasive, corrosive, or have high viscosity, as they can cause wear, galling, or cold welding on the mold surface. In addition, aluminum molds have a lower hardness and a shorter lifespan than steel molds, which makes them more suitable for prototyping and short-run production.

Steel

Steel is the most common metal used for injection molding molds, particularly for high-volume production. Steel molds offer superior hardness, toughness, and wear resistance, which ensure a long tool life and consistent performance. They also provide a high degree of precision and surface quality, which is essential for many applications in industries such as automotive, medical, and aerospace. Steel molds can be made from several types of steel alloys, including pre-hardened steels (such as P-20 and H-13), stainless steels, and tool steels (such as D-2 and A-2). Each type of steel has its own advantages and limitations in terms of machinability, thermal conductivity, corrosion resistance, and cost. Some steel molds may require additional post-treatment, such as nitriding, coating, or polishing, to enhance their performance and durability.

Other metals

While aluminum and steel are the most commonly used metals for injection molding molds, there are other metals that can be used in specific circumstances. For example, copper alloys (such as beryllium copper or tellurium copper) can offer high thermal conductivity and resistance to thermal fatigue, which make them suitable for molds that need to rapidly cool down the resin after injection. However, copper alloys can be expensive, difficult to machine, and have limited surface finish options. Magnesium alloys can also be used for molds that require low weight and high stiffness, but they are more prone to corrosion and have limited availability.

Conclusion

Choosing the right metal for injection molding molds depends on various factors, such as the resin type, the production volume, the part design, and the budget. While aluminum and steel are the most common choices, they have different properties and applications that should be carefully evaluated. Other metals, such as copper and magnesium, can provide additional benefits in specific scenarios but require more specialized knowledge and equipment. Ultimately, selecting the best metal for injection molding molds requires a balance between performance, cost, and feasibility, and can significantly impact the success and profitability of the production process.