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Start with the Die Cast Finish

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die casting starts with the surface finish

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

Aluminum Magnesium Zinc Die Casting Design Assistance

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:

die casting surface finishes quick guideCWM’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.

Die Casting Surface Finish Webinar thumbnailSurface 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.

CArticle on Corrosion-Resistant Trivalent Chromate surface finish for die castingorrosion-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 Die Cast Finishing Checklist thumbnailNADCA’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.

Key Questions to Ask When Sourcing the Best Die Caster for Your Project

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After months of research, deFindDCveloping a die casting design concept and validating it, you’re ready to move into the next phase of the project:  selecting a die caster to turn the concept into a reality.  Unless you have an existing relationship with a reputable die casting supplier that you’ve established, finding the best metal die caster to produce your product can be an arduous task.

There are some key areas that should be considered when choosing a die caster, whether it is for aluminum, magnesium, or zinc materials.   Certainly, the cost of die cast tooling and production will carry much weight in the decision process, but a good die caster will offer much more than a competitive price.  And, if you’re just comparing on price alone, be aware that some additional services may be included in the cost to build the tool.  In such cases, one quote for metal die casting may be higher than another so that you may not be comparing apples to apples.  Be sure to have a full understanding of what is included in the quote.  Also, a quote with additional services may cost more upfront but it can literally save you thousands of dollars over the life of your product. That’s why it’s important to consider several areas when selecting a good metal die caster and understand what’s included in the quote.

Before building an expensive tool for your metal die casting design, be sure to request a comprehensive description of the engineering consultations that will be held with your team.  The die casting engineers should fully understand your concept and its performance requirements in the end product.  With that understanding, the engineers can optimize your drawing for maximum performance in both the die casting process and its function in the end product.  The die casting engineer’s preplanning and analysis can recommend cost saving measures —or prevent costly mistakes over the project life.

With the initial engineering consultation, does the die casting supplier have the ability to take advantage of advanced technology using process simulation software (e.g., Magmasoft®) before the tool is built? Using your CAD file, they can use the software to predict and optimize metal flow, air entrapment, metal velocity, thermal balance, hotspots etc., during the die casting process.  This will assure a quality die casting design, shorten lead times and can lower production costs.

Can you trust that you’re getting an unbiased opinion about the correct metal alloy to use for your project?  There are multiple alloys (aluminum, zinc, and magnesium at CWM) and each has its own unique properties with advantages and disadvantages to each.   If your product requires post-finishing, it’s even more important to choose the right alloy because the physical properties of each alloy may or may not work with each type of finish.  Along with getting the right metal alloy recommendation, be sure that your die casting supplier fully understands all the finishing options available and can guide you to the right finish.  The die casting engineer must know all these variables from the project onset or it can result in costly quality issues later on.   Finishing can be a complex subject so we’ll talk more about it in another post.

Article on Selecting Best Die Cast Supplier for Aluminum, Magnesium, or Zinc


CWM created a 10-Point Checklist to Find the Right Die Caster to help OEM’s find the best metal die caster for their application.  There are many other important considerations than the few mentioned here.  Download the checklist from our Die Cast Design Center (DC2) and be prepared to ask all the right questions when you’re ready to choose a die caster for your next project.


The Insourcing Boom: Updated In-Depth Look at the Comeback of Manufacturing to the U.S.

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OEM Tech Brief Die Casting Article, The Insourcing Boom.  Chicago White Metal recognizes the increase in domestic die casting interest – and manufacturing, in general.  In many ways, domestic die casting becomes an ideal solution for several reasons, many of which convert to major benefits that contribute to the overall efficiency when deciding to use a U.S. die casting supplier.  The benefits can be anything from attention to detail, engineering ability, accessibility, U.S. control standards, and other capabilities.  When looking at an offshore provider or considering a U.S. die cast supplier, this article gives an insight on why domestic manufacturing is increasing.

After years of offshore production, U.S. companies are moving much of their far-flung manufacturing operations back home. General Electric is an early example, but it is not alone. Whirlpool, from China to Ohio; Otis, from Mexico to South Carolina; even Wham-O, from China to California.

Charles Fishman, award-winning investigative and magazine journalist writing in the Atlantic magazine, explores what he calls a startling, sustainable, just-getting-started return of industry to the United States. Read a TechBrief PDF condensation of his in-depth article and the reasons for these major production shifts that he labels “The Insourcing Boom.” Directly download the PDF here.


CWM Wins NADCA 2012 Aluminum Die Casting Award

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CWM Wins NADCA 2012 Aluminum Die Casting AwardAluminum Die Casted Archery Bow for Children

Key aluminum handle riser component for the new compound bow developed for young archers by industry leader Bowtech, produced as a high-tech die casting by Chicago White Metal Casting, won the 2012 NADCA International Die Casting Competition in the under one lb. classification.

Specifications called for the aluminum die cast riser to meet exacting professional bow tolerances at a targeted marketing price, plus conformance to a machined “hogout” appearance with all evidence of casting gates absent.

Download the Case Study of this riser die casting, in the Case Study section of the OEM Die Cast Design Center.

CWM Wins NADCA 2012 Magnesium Die Casting Award

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The central housing for an advanced spotting scope by Leupold & Stevens, world’s leading producer of high-performance sports optics, is designed to offer the sharpest, brightest viewing at distances greater than possible with premium binoculars. Impressive housing specifications called for lightweight portability, absolute ruggedness and 100% waterproof construction— nitrogen filled and guaranteed for life.  The scope housing requirements were met with an ideal solution – die casting magnesium (Mg) parts in order to fill the tall order.  The use of a magnesium alloy for die casting allows the spotting scope housing to be as lightweight as possible while still being able to withstand outdoor elements.

Die Cast Magnesium Housing for a Leopold Spotting Scope

The housing is produced by CWM as a hot-chamber, high-precision die cast magnesium housing, weighing just 8.0 oz. (226.8 gm) with thin-wall sections as narrow as 0.039 in. (1.0 mm). It received an award in the 2012 NADCA International Die Casting Competition in the over .5 lb. classification.

Download Case Study No. 42 of this spotting scope die cast magnesium housing component, with photographs, at this site’s DC2 Die Cast Design Center Case Studies page.