Aluminum Molds Vs. Steel Molds | Plastic Injection Molding

Aluminum Molds vs. Steel Molds: Five Critical Points of Comparison for Product Designers and Engineers 

The decision to choose between steel and aluminum tooling holds great importance for product designers. The type of tooling used significantly impacts several aspects of the project, such as part quality, cycle time, cost, and time-to-market. Thus, it is essential to understand the performance of each material during the injection molding process to make informed decisions for both present and future requirements.

This blog provides a critical comparison between P20 steel and QC-10 aluminum for five key areas: the cost/time to create and change molds based on the location of the tooling, tool life, thermal conductivity, part size and complexity by mold type, and material and surface finish options for aluminum and steel.

Location of tooling: USA vs. China

The location of tooling plays a crucial role in determining the project’s overall cost and time-to-market. The significant discrepancies in material costs between the USA and other countries, particularly in the case of aluminum and steel as raw materials, affect the overall cost of the tooling.

For instance, in the USA, aluminum is the default material for creating molds because it is cheaper than steel. On the other hand, raw steel is used as the default material in China because it is cheaper than aluminum. The use of different materials in different locations can significantly impact the injection molding process, affecting the cycle time, cost, and time-to-market.

Cost and time to create or change steel molds vs. aluminum molds

The cost of creating an aluminum mold is about 1/4 to 1/2 the cost of creating a steel mold. Therefore, aluminum tooling proves to be the most cost-effective option, even when comparing a quote from a China-based vendor for steel tooling to a USA aluminum quote.

The type of mold also impacts the cost of making changes. Aluminum tooling is roughly 1/10 the cost of changing a steel tool, irrespective of the manufacturing location, as it takes much longer and is harder to machine steel than aluminum.

The time required to create an aluminum tool is about 15-25 business days, while the average time required to create a steel tool is about 35-60 business days. The time required to change an aluminum tool is about 5 business days, compared to an average of 20 business days required to change a steel tool.

Tool life: P20 Steel Tooling vs. QC-10 Aluminum Tooling

The estimated volume for steel and aluminum molds depends on the material selection used during the injection molding process. P20 steel tooling has an average life of 50,000-100,000 parts, while QC-10 aluminum tooling has an average life of 10,000-25,000 parts.

Steel tooling offers a longer tool life than aluminum tooling and can produce a higher volume of parts before requiring maintenance or replacement. However, if the production volume does not exceed the 10s of thousands over the next year or so, aluminum tooling is the best option.

Thermal Conductivity of Aluminum vs. Steel

Aluminum’s thermal conductivity, which is about five times greater than steel, directly impacts the fill, flow, and cycle time of the injection molding process. The material fills the mold faster and more evenly in aluminum molds, and plastic can flow longer distances with less injection pressure, reducing the cycle time. Aluminum molds’ superior thermal control can reduce cycle time up to 40%.

Part size and complexity by mold type

While aluminum is softer than steel, it is a cost- and time-efficient option for high-volume production and larger parts. Steel tooling is more effective for parts and tooling that require extremely thin walls because of the increased hardness of the mold material. Additionally, aluminum molds are better suited for part designs with complex geometries that could cause fill issues due to the superior temperature control.

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  1. Douglas Bryce, Moldmaking Technology, “Why Offer Aluminum Molds for Production”, April 2002
  2. Claudia Zironi, Flowfront Magazine, “Competitive Advantages of Aluminum Molds for Injection Molding Applications: Process Simulation Used to Evaluate Cycle Times”, April 2005

* While steel as a raw material is cheaper than aluminum in both geographies, several other factors including market share, labor, and production costs must be factored into the material of choice in each country.