Aluminum, "Don't Prototype-Cast Me."
Manufacturers looking to cut costs, often drive the innovation of existing practices to achieve their goals. This produces new practices to continue growth while maintaining a competitive edge. While forward movement is necessary in all aspects of business, it is especially so in the injection mold industry. With increasing competition from overseas tool makers and pressure from customers at home to offer lower priced options, mold builders have increased the measures utilized to cut costs. One of these measures has been the increased use of aluminum as a material in production tools opposed to traditional tool steel.
While utilizing aluminum as a material for injection molds is hardly a new practice, the processes that have increased the lifespan of aluminum tooling are next level. Previously, it was accepted that an aluminum mold was simply used for prototyping or short-run before making the jump to a steel tool. The steel molds have always been the industry standard for the high production, class 101 needs that many plastic parts require. However, with the introduction of new aluminum alloys of greater strength and the coating and plating wizardry of leading innovators, the aluminum mold is quickly becoming an attractive alternative to traditional steel.
Aluminum offers several intriguing options to injection molding that could benefit both mold builders and the end users molding the finished product. Aluminum is easier to cut, reducing machining hours and offering faster delivery times than tool steel. It cools an a more even and efficient rate than steel which can, theoretically, reduce cycle times by the molder and eliminate possible hot spots. Aluminum is also much lighter than steel making it easier to deal with from a logistics standpoint.
The traditional views that kept aluminum tethered to prototype and short-run tooling was primarily based on the strength and hardness of the material. With modern advancements in alloy development and coatings, you can now feasibly achieve cycles of 1 million and higher with aluminum tooling. The advancements in nickel boron and electro-less nickel coatings can raise a traditionally soft aluminum, 18 HRC, up to a more production friendly 45 HRC. This coupled with the corrosion resistance, surface finish, and lubricity of these coatings are all huge gains for aluminum as a lasting tool material.
These breakthroughs do not eliminate all of the concerns when working with aluminum however. Preventative maintenance measures are always a must with any injection mold, but aluminum requires special attention to ensure optimal performance. In the event that a part sticks in the mold an object made of aluminum or a lighter material should be used to remove the part. Never use a screwdriver or any other steel tool for removal. Also, when a repair or revision is needed on a coated aluminum mold the coating must be completely removed prior to welding or machining and reapplied once the process is complete.
Resin options carry a high impact when considering injection molding and can be even more of an issue with an aluminum mold. While aluminum has proven effective as a tooling option for many applications, it is best used with less abrasive materials such as polypropylene, thermoplastic poly-olefin, or acrylic as opposed to glass filled resins. While the more abrasive resins such as ABS can be used, it is best to first consider what the life of the tool is going to be prior to deciding on the construction material.
Today, aluminum is being utilized in injection molds producing parts in the automotive industry, for medical devices, and everything in between. With these new advancements to the viability of aluminum molds, producers’ ever increasing cost awareness, and decreasing delivery times, the future looks very bright for aluminum in the injection molding industry.
Further Reading:
Expanding Aluminum’s Potential, Mold Making Technology, May 2015 by Robert Lammon and Harry Raimondi http://www.moldmakingtechnology.com/articles/expanding-aluminums-potential
General Guidelines for Building Aluminum Production Injection Molds Aluminum Injection Mold Company, by David Bank http://aluminuminjectionmold.com/files/Dave_Bank0310.pdf
