Summary:  Aluminum injection molds are finally gaining a foothold in the plastic injection industry, which can no longer ignore its benefits over traditional metals.

Guide to Aluminum Injection Molds Design

In the injection molding industry, bad tooling practices and selection of aluminum alloys have given rise to a pervasive myth that aluminum is ‘tooling for prototypes only’.

This is, however, changing quickly, and aluminum along with 3D printed molds are competing with traditional metals in the plastic injection market.

Modern aluminum injection mold offers superior quality with lesser scrap, faster turnaround times, tighter tolerance, and process consistency, significantly saving on production costs. The range of applications for aluminum in injection molding plastic manufacturing is limitless.

How to Make Aluminum Injection Molds? 

Aluminum injection molds are gaining prominence as they help achieve reduced costs. Also, as aluminum tends to cool at an even rate, the cycle times drop, allowing for quicker production. Aluminum molds are generally less expensive as compared to steel and have a faster build time.

Aluminum CNC machining has become the predominant method of making molds with varying degrees of complexity, accurate detailing, and lower turnaround times.

In some cases where cavities need to have sharp corners, the process may require additional EDM (Electrical Discharge Machining) as regular milling may not help achieve it.

The basic injection molding process involves two mold halves separating at the end of the cycle to eject the part. With this simple structure, the part cannot have undercut or overhanging features as the mold halves would catch on to each other when separating.

When the mold is used to make complex plastic parts, additional complexity is added. Slides are added to the mold to accommodate such features. The overall processing is mainly machine-based; there is no thermal processing or specialized tooling involved. An aluminum injection mold takes about 10-15 days on average to complete.

How Does an Aluminum Injection Mold Cost?

The cost of an aluminum injection mold can vary depending on a number of factors. High-quality molds with tighter tolerances, longer production life, and more cavities would take longer to build and cost more. However, a superior quality mold offers considerable long-term savings that outweigh the upfront cost. These molds last longer and require less maintenance as compared to poor-quality tools.

Aluminum Mold for Plastic Injection

Injection molding companies are seeing aluminum as an attractive option for plastic injection because it can speed up mold construction, reduce cycle times to a great extent, and cut down tooling costs.

An application in aluminum mold runs 20-40 percent faster than the same part running in a steel mold. This efficiency is increasingly making the plastic injection industry more competitive globally.

This means the inherent efficiencies brought about by the use of aluminum in injection molding can ensure you never lose orders or contracts to traditional steel-based plastic injection molding companies with similar offerings. Steel mold operators cannot compete with an aluminum under similar conditions and requirements.

Molders are likely to be surprised in the beginning to see how quickly an aluminum mold reaches its processing temperature due to its high thermal conductivity. This means you not only get more parts produced per shift but also get reduced machine downtime for changing molds.

With an increased machine utilization, you can produce more parts with less equipment. Molding operators can also save time at different points during the plastic injection as aluminum heats and cools faster.

The Life Expectancy of Aluminum Injection Mold 

The life expectancy of an injection mold is of great interest to toolmakers and injection molders. With proper care and maintenance, aluminum injection mold can reach the mark of a million shots with multiple resins and in different situations. While there is no single set of guidelines for aluminum tool maintenance, each tool needs a custom maintenance plan depending on numerous factors.

Some of the most important factors to take into consideration when determining a maintenance schedule for an injection mold include the type of resin, mechanical actions, the presence of coating, and the gate type.

Several material-related cautions should be practiced, to extend the life expectancy of an aluminum injection mold. A Nibore coating is a popular method to prevent the wearing of gate area due to filled resins. The coating also reduces the oxidation in the tool to further extend its life expectancy.

There are a few molding parameters that affect how the aluminum mold should be maintained. Excessive temperatures and pressure during an injection can damage the tool quickly and reduce its life period.

As a part of a regular maintenance routine, the aluminum mold should be cleaned thoroughly after every run, of parts and resin residue. It may often run 5-7 days before having to be cleaned, but in some cases, may need cleaning every 2-3 days for different reasons.

Regardless of the length of the run, aluminum molds need cleaning after they are out of the press and before storing for the next order. Routine maintenance should also include regular checking for wear and galling. Regular care also promotes the quality of parts and optimal performance of the molds. This consideration and thermal benefits make aluminum a preferred choice for many injection molds today.


In the hyper-competitive business environment that we live in today, cost savings and efficiencies, no matter how insignificant, can no longer be ignored. Such competitive forces are finally forcing injection mold operators away from the status quo and towards alternatives to traditional methods.

With this, the time for widespread acceptance of aluminum tooling has finally arrived, and thanks to numerous improvements in the grading of aluminum alloys, and effective tooling and molding practices, there is no better time to make the transition.