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Category Archives: Material Selection

CWM and A-Dec Dental win the prestigious IMA Award for Die Casting!

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International Magnesium Association presents Chicago White Metal with the prestigious Magnesium Die Casting Award for Excellence in Design.

Chicago White Metal does it again!  To add to the collection of die casting awards, CWM teamed up with A-Dec to create a part that fulfills and exceeds the high standards and quality of A-Dec’s parts, which ultimately became an award-winning duo.

The International Magnesium Association (IMA) was founded in 1943 with a mission in mind – “promote the use of the metal magnesium in material selection and encourage innovative applications of the versatile metal.”

A-Dec produces high-end dental products with exceptional quality.

This Award of Excellence is an annual award that is given to the company demonstrating an outstanding example of the use of magnesium.  With the rear housing and driver die castings being the first magnesium parts to be used in A-Dec’s LED Operatory Dental Light, the benefit of a decreased mass, ease of movement, and satisfaction of the customer proved to be a winner in itself, even without the award.

LED-Light-Housing-Magnesium-Die-Casting-Part

 When asked why a magnesium die casting was chosen for this application, a presentation given by Jon Miller a the Closing Banquet said the following:

“Magnesium’s strength-to-weight ratio and thin wall casting capability allowed for a thin-walled, lightweight part, which in turnallowed for a slender, stylish, ergonomic support structure.  Magnesium’s low mass enables the LED light to be easily maneuvered/positioned and minimizes issues with drift, inertia, or vibration.  Magnesium’s ability to dissipate heat allowed for passive cooling of the circuit board and diode connection points.  This means fewer moving parts and helps the unit achieve an estimated 20-year service life.  Magnesium’s ability to be die cast with excellent surface finish, and to readily accept commercial RoHs-compliant pre-treatment and po

magnesium-die-casting-driver-componentswder paint allowed the light housing to have a highly cosmetic appearance, matching the uniformity of the mating molded plastic and painted tubular structure.”

Congratulations to CWM and to A-Dec for amazing teamwork on this magnesium die casting duo!  

Aluminum vs. Magnesium vs. Zinc: Alloy Properties in a Nutshell

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Aluminum, magnesium, and zinc are the most common alloys used in the die casting process.  Aluminum and magnesium are considered to be relatively “lightweight” metals, and zinc alloys are a preferred metal to use in the miniature die casting processes and applications requiring thinner walls.

Deciding which alloy is best suited for a specific application of a die cast part is usually based on the design specifications – the alloy usually provides physical and mechanical properties that fit the end product application.  It is important for a product designer seeking a die casting supplier to understand each type of alloy being offered and what benefits are involved.

Aluminum Die Casting Alloy

Metal Die Casting Worker is hand filing an aluminum component at the parting line.

Aluminum is by far the most frequently used alloy in die casting.  The most common aluminum die casting alloy is A380, which offers the best combination of material properties and castability.  Aluminum alloy die castings are used in a wide variety of industries.  It is common to see this alloy in electronics, communications equipment, automotive components, gear cases, lawn mower housings, hand and power tools, and many other products.

There are a number of aluminum alloys used in die casting.  Each alloy has its own unique set of properties.  Aluminum alloys for die casting have superior machining characteristics in comparison to iron, steel, and titanium.  Amongst the other types of aluminum alloys, A380 has better than average machining characteristics.

Aluminum die casting alloy informational sheet from NADCA.

For more information on Aluminum Alloys for Die Casting:
Click Here to Register and Download “NADCA Alloy Data: Aluminum Alloys” White Paper.

 

 

Magnesium Die Casting Alloy

Magnesium alloys are Magneisum die casting used as a Kodak camera housing.the lightest of the commonly used structural metals used for die casting.  Magnesium alloy AZ91D offers the highest strength of all commercial magnesium die casting alloys.  It is also the most widely used.  AZ91D Magnesium is a high purity die casting alloy which offers the following qualities:

–          Excellent Corrosion Resistance

–          Excellent Castability

–          Excellent Strength

Corrosion resistance is achieved by enforcing strict limits on three metallic impurities: Iron, Nickel, and Copper.

Some of the more common applications for magnesium die castings are:

Automotive: cam covers, steering columns, steering wheels, brake and clutch pedals, clutch housings, seat frames, and dashboard supports; Portable tools such as: chain saws, drills, grinders, lawn mowers, string trimmers and pruners; portable electronics such as: projectors, cameras, radar indicators, calculators, and navigation devices; telecommunications equipment, levels; and recreational products such as: snowmobile components, archery bows, spotting scopes, etc.

While there are special precautions to take when machining or grinding magnesium die castings, magnesium alloys machine easily, requiring less power to machine than the other die casting alloys.

Finishing magnesium castings is similar to other alloys and any special treatments and coatings are usually taken into account when considering the end product and application.

magnesium alloys for die casting - information sheet from NADCA.  For more information on Magnesium Alloys for Die Casting: 
Click Here to Register and Download “NADCA Alloy Data: Magnesium Alloys” White Paper.

 

Zinc and ZA Die Casting Alloys

Zinc and ZA alloys are Zinc and ZA Alloys have ingots and recycled zinc, ZA8, Zamak 3 die casting scraps.  commonly used for smaller die castings or die castings that require thinner sections.  Zinc alloys generally allow greater variation in section thickness and can maintain closer tolerances.  The impact strength of zinc die cast components are higher than the other common metal alloys, with the exception of brass.  Also, because Zinc and ZA alloys require lower pressure and temperatures in comparison to magnesium and aluminum alloys, the die life is significantly longer and maintenance is relatively minimal.

Zamak alloys all contain approximately 4% aluminum and a smaller percentage of magnesium to make sure strength, hardness, and corrosion resistance properties can be achieved.

When it comes to miniature die castings, zinc is definitely the route to take.  Miniature zinc die castings can be produced at high volume using special hot-chamber die casting machines that yield castings which are flash-free, with minimal draft and very close tolerances, requiring no secondary trimming or machining.

Zamak #3 is the most common of the Zinc alloys for die casting, offering the best combination of mechanical properties, castability, and economics.  These zinc alloy metals have the ability to produce castings that have intricate details and surface finish at high production rates.

ZA alloys have more aluminum and copper content in them than the Zamak group for several reasons:  higher strength, superior wear resistance, superior creep resistance, and lower densities.  ZA-8 is the sole ZA alloy that can be die cast by the faster hot-chamber process.

Machining characteristics of Zamak and ZA are very good and both alloys have the ability to accommodate high-quality surface finishes when routine guidelines for machining zinc are followed.

zinc, miniature zinc, ZA8, and zamak alloy groups explained in this NADCA information sheet about die casting alloys.  For more information on Zinc Alloys for Die Casting: 
Click Here to Register and Download “NADCA Alloy Data: Zinc and ZA Alloys” White Paper.

 

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magnesium zinc and aluminum die casting engineer at work.

If there are any suggestions to be made to gain more information, it is this:  have that initial discussion with a die casting specialist or engineer regarding the product and its application!  This will increase the understanding from a product design standpoint in order to know what options are available and best for your product.

 

North American Die Casting Association. “NADCA Alloy Data: Aluminum Alloys,” “NADCA Alloy Data: Magnesium Alloys,” “NADCA Alloy Data: Zinc and ZA Alloys.”  NADCA Product Specification Standards for Die Castings. 9th ed. Vol. #402. Arlington Heights, IL: NADCA, 2015. N. pag. Print. NADCA Publication.

Tactics for Optimal Product Design for Die Casting

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Developing an optimum product design for die casting is similar, in most respects, for any material/process combination. In capitalizing on today’s advanced die casting processes, however, specific attributes of die casting alloys and the die casting process offer opportunities for distinct product advantages and cost reductions that require somewhat different tactics. These should be applied when a totally new product is being developed, and are critical when an existing product made from another material or process is being redesigned for die casting.

An engineer going over a CAD design for custom die casting designWhen a custom die casting design (or any design) is started from a clean sheet of paper, the designer must disassociate the design constraints from the materials and processes traditionally employed. This is the path to the optimum cost-effective results. Three principles are helpful:

• Think function, before traditional form.
• Performance must be sufficient, not equal.
• Match material properties to performance specifications.

Function Before Traditional Form
In many cases form does not reflect function, but is instead determined by the traditional material and process employed. Therefore, it is essential to think of the function(s) that the component is to perform, and disregard the traditional or previous process form. For example:

• A powdered metal part may have relatively thick walls in structural areas, with throughholes to remove excess material. A die casting typically achieves maximum structural properties by utilizing thin walls with corrugated sections or rib reinforcements.

• An injection molded plastic component may be attached with through bolts and nuts, which are required because the viscoelastic (relaxation) behavior of the plastic makes it necessary to apply only compression loads. Or it may utilize metal inserts. A die casting with superior creep and relaxation properties can employ tapped threads to an advantage.

• A billet machined part may have block like features to obtain functions, for example: square pockets, sharp edges, flat and cylindrical surfaces. The same part designed as a custom die casting may obtain function with smooth filleted pockets, generously radiused edges and contoured and shaped surfaces.

The function before traditional form principle can often be applied to die castings made a few years ago. In many cases, wall thicknesses have been dictated by the limitations of then existing casting technology, so that the die casting component was over designed in terms of functional and structural criteria. Yesterday’s die castings can often be redesigned and produced by today’s advanced, custom die casting technology with thinner walls, reduced draft, and closer tolerances that more nearly reflect the functional criteria.

It is important to note that the definition of form in “function before traditional form” is the traditional shape that is required by specific manufacturing processes. This is not to be confused with a purposely designed form or shape that may provide value or function to the product design. The die casting process easily produces complex design shapes that may be difficult, costly or impossible to produce with other manufacturing processes.
Zinc Magnesium Aluminum Die Casting Optimization

To read more, Chicago White Metal Casting published a technical paper titled, “Developing an Optimum Product Design, Capitalizing on Die Casting.”  The paper reviews two additional designing principles mentioned in this post: 1) Performance must be sufficient, not equal and 2) Match material properties to performance specifications.  The technical paper is available as a free download in our Die Casting Design Center (DC2) to any subscriber.  Subscribe now and download the technical paper.

Contact CWM today to discuss your custom die casting project!

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

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:

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.