Everything You Need to Know About Die Casting:
Toward A new Generation of Components
The die casting process for many years was more of an art than a science. Techniques for transporting metal to the die cavity, injecting the molten metal, controlling solidification, and ejecting the casting were developed on an empirical basis. The industry tended to practice those techniques that appeared to work best.
In the 1970s, basic research was initiated by several organizations within the die casting and metals industries to better understand the fundamentals of thermodynamics, heat transfer and fluid flow that govern the die casting process. The relevant factors have been quantified and transferred to the die casting industry. This technology transfer has elevated die casting from a proprietary art to an applied science.
Many die casters are applying this science to produce castings with wall thicknesses, surface finishes and dimensional tolerances that were unthinkable a few years ago. Cored holes, hubs and other features are being produced with zero draft and very close tolerances, eliminating costly finish machining operations. The specific capability is often proprietary, and it varies with the alloy being cast and the individual die caster. It cannot, therefore, be quantified into industry-wide standards.
Perhaps the most obvious product capability now possible through the new casting technologies is the minimum allowable wall thickness. Previously, minimum wall thicknesses for structural features were too often specified according to the minimum that could be cast, rather than the mechanical and structural requirements. Decorative components required sufficient wall thicknesses to bury porosity in order to ensure a quality surface.
In all applications, die castings can now be designed with more emphasis on structural criteria and less restraint from process limitations. Die casters are using shot control systems that measure, control and monitor the flow of metal into the die. As discussed, automatic vacuum systems are reducing or eliminating porosity. Electronic surveillance of the die casting process is being employed to alert the die caster to impending defects before they occur.
Comprehensive standards for die cast products are published in the ADCI Product Standards Manual, which defines the product design criteria that should apply for the most economical casting production. This 94-page volume, under continuous revision, includes standards for draft requirements, dimensions for fillets, ribs, and corners, and criteria for flash removal.
Designers can realize the benefits of high technology die casting by indicating the finished form of the product on their drawings, rather than attempting to define the as cast form and provide finish stock. The designer can then review designs in process with an advanced technology die caster to reduce finish-machining operations and reduce product cost.
The cycle of research, technology transfer and application is an ongoing process that is keeping the die casting industry competitive. Product designers who work closely-and early-with their custom die caster will maximize material and process benefits and enhance their position in the world marketplace.
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