There’s increasing interest in the benefits of aluminum tooling for higher volume injection molded applications, especially in automotive. Our firm has been involved with aluminum tooling for prototype and production applications since the early 1990s, and more recently we began to apply that knowledge to the automotive industry.

Just over five years ago, our company, and later some others, began working with Honda and other major automakers to create standards for aluminum tooling and to help the OEMs achieve their goals of lower tooling and production costs while maintaining part quality previously achieved only with carbon alloy steel. Aluminum tooling is being used today on selected high-volume applications at Honda and other OEMs with production runs already reaching hundreds of thousands of parts.

It’s a big opportunity, but our experience also shows that aluminum tooling probably isn’t for every application. It depends on the material, the part being produced, the volumes involved, and the number and kind of secondary operations being performed.

Author Darcy King (left) and Al Standaert, technical sales manager of Unique Tool & Gauge, with examples of aluminum tools that are providing a big payoff in automotive injection molding.

We’re also firm believers that when the first aluminum tooling project is being planned, it’s important to get real buy-in from all parties involved. We have had to develop new ways of designing tools specifically for aluminum, allowing for the softer material and different thermal expansion rates versus steel, and also to develop new operating guidelines, different from those for cutting steel in our mold shop. In addition, we’ve worked closely with molders to test and set new operating guidelines for presses that normally use steel molds. You may travel down this same road as well.

We’ve already worked through a lot of the start-up issues, and we believe a fundamental shift to aluminum tooling for higher volume automotive applications is on the horizon. Here’s why.

HUGE POTENTIAL PAYOFF
Our experience has been that a properly planned and executed aluminum tooling program will result in faster tool construction and overall reduced tooling costs with the potential for truly dramatic molding cycle-time savings and corresponding impact on part cost. Automakers can realize savings of 5% to 10% on construction of new tools for the majority of their applications, as well as the added benefit of shortening tooling lead times by 10% or more vs. steel.

Finally, molding cycle-time reductions of 20% to 40%—or even more—are readily achievable with aluminum tools, given aluminum’s superior thermal conductivity. In addition to faster cycles, aluminum tooling’s thermal-conductivity advantage also helps to produce parts with less warpage and tighter tolerances.

One automotive manufacturer recently concluded that more than 70% of the plastics planned for use in a typical auto being designed today will be TPO, PE, or PP. These polyolefins are ideal candidates for aluminum tooling. As automakers move to lower volumes, the cost efficiencies of aluminum tooling will make it an attractive candidate for even more applications.

GUIDELINES FOR SUCCESS
Unique Tool & Gauge has now worked on several aluminum tooling projects for higher volume applications and we’ve developed a short list of guidelines and best practices that will be of value to tool builders and producers as they consider aluminum tools for higher volume plastics applications.

First, planned secondary operations after the molding process should be thoroughly investigated for potential cycle improvements, so that tool design can be optimized when possible to match the thermal conductivity advantages inherent in aluminum. There will be no advantage in faster molding if the secondary operations can’t keep pace.

As an example, our showcase high-volume application is the tool we built for the Honda Accord rear deck tray, in production since August 2007 and now past roughly 500,000 cycles. Honda is currently realizing molding cycle time savings of approximately 20%, although the savings in this case are actually limited by the number of secondary operations performed in the same manufacturing cell where the part is molded.

If the part in question is to be molded and then moved somewhere else in the plant, or will be immediately shipped out, then the molder can take full advantage of all the benefits of cycle-time reduction.

From a design point of view, applications using less abrasive materials like PP, TPO, or PE, and low-visibility or hidden parts, are probably the best way to go with aluminum tools, at least initially. Start with fairly shallow parts, which have less side molding pressure, and tools should be designed with fairly flat parting-line run offs and with seal-offs that are not extreme—that is, no less than 5°. These types of parts typically lend themselves to high volumes with low tool maintenance. In a similar vein, non-grained parts and parts that don’t require a high surface finish are good places to start with aluminum.

Finally, consider parts that are less likely to have engineering changes.

As regards maintenance, issues like flash and parting lines are considerations for any tool, steel included. Maintenance personnel will need to develop additional skills for welding aluminum. Aluminum is not more difficult to weld than steel, but there are differences in process and technique that must be learned. Most molders we work with have long been able to do small tool weld repairs themselves on P20 steel tools, but send out molds of QC-10 aluminum. We ourselves have had to develop in-house techniques to reduce the “halo effect” common with heat-affected areas when welding aluminum.

I don’t believe this is a significant long-term issue, as aluminum suppliers are now introducing new tools, materials, and techniques to assist maintenance personnel in this area.

FOCUS ON THE FUTURE
In Part II of this series, we’ll delve further into aluminum tooling production issues and opportunities. Are there limitations to the application of aluminum tooling, versus P20 mold steel? Our business hasn’t seen them and we think the future is bright for aluminum tooling. There are very few technologies available to automotive manufacturers today that can match aluminum tooling’s powerful potential for significant reductions in piece part cost over a broad array of applications.