One of CWM’s Sales Engineers coined the phrase, ‘Start with the finish in mind.’ This is because the specific design features of a die cast part, in almost every case, has a direct impact on achieving the required surface finish specifications. For this reason, all die casting finishing requirements should be discussed with the die caster early in the design phase.
Die castings and subsequent surface finishes have a symbiotic relationship. That is, the results of each process “work together,” and each benefit from the relationship. For example, aluminum die castings that call for a cosmetic surface will require attention to the location of the casting’s parting line, gate, overflows and vents. If these design features interfere with or blemish any of the part’s designated cosmetic surfaces, undesired results will occur.
The importance of reviewing the finish with the die caster early in the project is also exemplified by the tool design. Cosmetic surface requirements for the custom die casting may require special finishing of the cavities of the die. In addition, the cover die half will generally be used to produce a specified cosmetic surface. This permits the ejector die half to contain the required ejector pins— which assist in ejecting the part cleanly from the die.
It is essential that the die caster understands how parts mate with other components in the final product assembly. The die caster will analyze the design to assure a quality finish, and equally important, to make sure that tolerance specifications will be met. If this step is omitted, it could lead to additional finishing processes that increase piece price costs.
Cost is certainly another driver to have an early discussion with the potential die cast supplier. As discussed earlier, the geometry of the design’s features have a direct impact on the final surface finish. An early review with the die caster can result in minor modifications (i.e., critical surfaces, edges, and mounting features) that reduce the need for surface preparation before the final coating. The end result is increased efficiency which has a direct impact on lowering the final production cost.
Unlike many die casters that only produce raw castings, CWM is a full-service, die cast-to-finish supplier. Over 90% of our castings include additional post-cast finishing operations prior to shipment to our customers. With that high volume of post-finishing experience, coupled with over 75 years of performance, our die cast finishing expertise is unsurpassed. Further, when it comes to recommending the right alloy with the optimal finishing process, CWM is in a unique position to provide unbiased information since we work with the most widely used metals: aluminum, magnesium and zinc. If you would like to tap in to that experience by reviewing your project with a CWM Sales Engineer, please call us at 630-595-4424.
Additional Die Cast Finishing Resources
CWM’s DC2 –
Die Casting Design Center is a valuable free resource to aid you when designing for die casting products. You’ll get access to an educational hub—the largest collection of technical die casting content in the industry—geared to assist OEM design engineers, purchasing specifiers, and OEM design consultants through the die casting process.
All these die cast finishing resources are available for a free download in DC2:
CWM’s Quick Guide to Surface Finishing for Die Castings:
A comprehensive 8-page condensed resource on evaluating surface finishing alternatives and optimizing component finishing decisions for magnesium, aluminum, and zinc die cast products. Contains illustrated die cast surface design guidelines for enhancing finishing results; Describes how part design features can impact your final finishing results; Features a comparison table rating 33 surface coatings on relative cost, appearance, wear and corrosion resistance; Presents recommended finishing steps and optimum coatings and finishes for a range of typical die cast housings and components, from strictly functional components to highly-cosmetic parts and those with fail-safe EMI-RFI shielding requirements.
Surface Finishes for Die Castings – pre-recorded webinar:
This Webinar provides practical knowledge of the different types of surface finishes for die cast parts; the factors to consider when selecting a die cast surface finish; the advantages and limitations of common finishes recommended for die cast components; and important finishing considerations to build in during the die cast design phase.
Corrosion-Resistant RoHS* Compliant Trivalent Chromate Coating:
Latest information on Trivalent chromium, which is now a proven alternative to hexavalent chromium coatings and meets new U.S. and European Union environmental mandates for die cast products. Economical, with a cosmetically pleasing surface finish, it offers high corrosion resistance for CWM aluminum, zinc, and magnesium die castings.
NADCA’s Finishing Checklist:
Provides a convenient method for assuring that important factors involved in the surface finishing of cast parts are evaluated and clearly communicated between the purchaser and the caster.
High Pressure Die Cast Coupons:
When making a decision between different surface finishes for your product, seeing the actual finish on the metal can be a valuable aid to the decision process. CWM offers coupons in three different alloys (aluminum, magnesium, and zinc) with a variety of options for die cast finishing.