Making Custom Mold Parts

Posted by joseph george on January 4th, 2021

Molds have to be made accurately using the best material to aid in the production of high-quality molded parts. Therefore, making mold is a time and labor intensive process with several considerations.

Material Selection

Mostly, molds are custom made to manufacture parts with desired specifications. Making custom mold parts involves selecting the best material for designing and making mold. There could be several options such as steel and aluminum.

Steel or aluminum?

Usually, molds are made of hardened or pre-hardened steel. Hardened steel or steel treated after machining offers better wear resistance than pre-hardened steel and also lasts longer. Steel molds are highly expensive than the one made from aluminum. They are more durable and ensure a high rate of production before requiring a replacement. It may ask for a large investment upfront, but it is cost-effective in the long run.  

Material Considerations with Steel

Design engineers have to consider several factors such as steel hardness and steel brittleness before selecting the material. Harder the steel, the more brittle it is, and it doesn’t make a great choice for making mold parts that are subjected to impact or side loading.  

Aluminum is known for its rapid cooling characteristics, which makes it suitable for tooling. It can also reduce the time required for building a mold because it is easier to machine than steel. Mold core machining with aluminum ensures faster turnaround time and production cycles. Because it is softer than steel, even hardened aluminum is tough to weld and difficult to maintain. It wears rapidly so, it suitable for prototypes and short runs only. Sometimes, hybrid molds may be an option, if the product design allows. In this case, molds are mostly steel, but have aluminum in low-wear areas.  

Aluminum is never the preferred material for complex mold parts for harder, glass-filled plastics because of wear. Copper alloys may replace aluminum when heat dissipation is essential.

If needed, both steel and aluminum can be given a coating of special materials to enhance their wear resistance property and reduce friction. This is especially true with molding fiberglass-reinforced plastics and to make tooling last longer. Commonly, coating options include nickel-boron and nickel-teflon.

Choosing the best material for making mold parts is highly essential in ensuring the durability and accuracy of mold design that will in-turn impact the final part production. Therefore, material selection, mold part tooling and machining should be discussed with the mold expert before designing mold parts.

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