Design Geometry Considerations for Die Casting

Design Geometry Considerations for Die Casting

Producing a top quality die cast component part starts with a solid and well thought out design. The goal of any die cast design is to create a casting that will maximize the function of the part, while being one that can be produced fairly quickly, efficiently, with few defects, and little to no secondary operations necessary.

There are many factors that need to be taken into consideration when designing a die, such as:
• Wall thickness
• Wall thickness uniformity
• Draft
• Pockets
• Fillets and corners
• Ribs and bosses
• And more

Wall thickness
Wall thickness is the distance between two parallel (or nearly parallel) surfaces and will vary depending on the thickness to length ratio of the entire part. If your part is very long it is difficult to maintain a very thin wall. You want your wall thickness to be as thin as possible while maintaining the strength and overall functional requirements necessary for your specific application.

Typical minimum wall thickness:

Wall thickness uniformity
Ideally, you want a design that creates uniform wall thickness all around the casting. This doesn’t mean that it needs to be 100% the same on all sides, only that you should strive to minimize drastic wall thickness variations. Dramatic variations in wall thickness can result in different rates of cooling along the cast wall which can alter the dimensions of the finished part. Uniform thickness also allows you to better control the flow of the metal into the die in order to ensure a complete fill.

When it comes to die casting a draft refers to the slope or taper that run in the direction of the die’s opening. The taper should be greater on the interior of the die walls than it is on the exterior walls so that when the alloy cools and solidifies it will shrink and fit more tightly on the inside of the casting. The greater the interior draft, the easier the finished part will be to remove from the die and the more precise the finished product will be.

If your part needs to be light, pockets are excellent inclusions in die cast designs. Basically these pockets, also referred to as metal savers, are open spaces or holes placed in the design of the die. Strategically placed pockets make your final part lighter without compromising any of the structural integrity.

Fillets and corners
Fillets are the curved parts of the casting where two surfaces would normally have come together at a sharp angle. They are added to a die casting to eliminate hard edges and corners that are not desired in the final part. It is best to utilize large inner and outer corner radii for the cast part. The larger the radii the stronger the final part will be.

Ribs and bosses
Bosses generally serve as stand-offs and mounting points, while ribs are added to provide support without increasing wall thickness. If it is possible, design any necessary ribs and bosses directly into the die cast. These features help eliminate sharp corners and help increase the overall strength of the finished part.

Consulting with an experienced die caster during the design phase will help eliminate any potential problems affecting tooling and production of your new part.

How can A&B help?
A&B Die Casting leads the industry with a trusted worldwide reputation for unique economical approaches and value-added services for all of your die casting solutions. We pride ourselves on doing the hard work upfront so that we can generate the most value to our customers for years to come.

Need assistance or want to get started on your next die cast project? Contact A&B Die Casting today!

Assembly Methods for Die Cast Parts

Assembly Methods for Die Cast Parts

Die casting is an extremely popular manufacturing process for creating metal products. Die cast parts produce high quality, uniform pieces that can be created in just about any size, part geometry, surface texture, or finish. They can require minimal secondary processes since many features can be integrated into the design such as studs, hinges, drill holes, and bosses, to name a few. There are quite a few methods to assemble individual die cast parts made from aluminum or zinc.

These methods include:
• Adhesive bonding
• Attachment systems
• External threads
• Forming or self-cutting fasteners
• Injected Metal Assembly (IMA)
• Inserts
• Interference fits
• Threaded fasteners

Adhesive bonding
Adhesive bonding between metals is becoming a more popular practice among die casters. The adhesive “wets” the entire surface to be joined and must have a lower surface tension than the materials being joined. Joints that are subjected to high tension are generally not suitable for adhesive bonding. Adhesive bonds are also prone to thermal degradation and peeling. Adhesive bonding is extremely popular for bonding sheet steel in automobile bodies.

Attachment systems
Attachments that require plastic deformation of the casting is usually limited to alloys with high ductility, such as zinc.

Attachments of this nature include:
• Crimping
• Staking
• Swaging

Adhesive bonding has become much more popular since the stresses are spread out more uniformly and exposed surfaces are not disturbed. They also offer other benefits such as sealing, insulating, and corrosion barriers.

External threads
It is possible to cast external threads on cylindrical features under specific circumstances. Threads can be formed across the parting line of the die with either slides or solid components. Flash can get left in threads with slides, or made across parting lines, which can be quite difficult to remove. If the flash isn’t severe, it can be removed through the process of the bolt and nut installation. Many manufacturers prefer casting flats at the root of the thread on the parting line so that the flash forms on the flats making it very easy to remove.

Forming or self-cutting fasteners
This type of assembly utilizes hard steel fasteners that anchor to the die cast part itself by either forming to or cutting into the part as they are installed. Die cast alloys are typically relatively soft and readily accept these types of fasteners.

These types of fasteners include:
• Spring clips
• Stamped nuts
• Self-tapping screws
• Thread-forming screws

In most cases properly sized holes can be cast into the part to accept the required fastener. Spring clips and stamped nuts develop a relatively low retention force where as self-tapping and thread-forming screws have a much higher retention capability. Though, fasteners that cut form small chips where they bite into the metal part which may not be tolerable in certain finished projects, such as sensitive electronic equipment.

Injected Metal Assembly (IMA)
The IMA process is very similar to the adhesive bonding process except IMA utilizes a molten alloy to bond components together. The process creates a strong, permanent, mechanical “lock” that can withstand high loads and can also bond metals to non-metal parts. The process requires no special surface preparations and issues such as thermal degradation and peeling are not very common.IMA bonds also perform exceptionally well in harsh environments.

Small components of just about any material can be joined utilizing IMA, such as:
• Ceramic
• Elastomers
• Fibers
• Metals
• Paper
• Plastics

Inserts are used when the design will impose conditions that exceed the capabilities of the alloys such as excessive thread wear, concentrated loads, abrasion, and wear at a bearing point. However, inserts cause residual stress within the cast part so proper planning for long term retention is vital. There are two types of inserts that can be installed – cast-in-place or post-installed inserts. The cycle time and the cost are usually what determine which type of inserts is used.

Cast-in-place inserts allow for a wider range of mechanical lock securing options since the alloy is cast directly around the insert. They are required to be as dimensionally accurate as the die into which it is inserted, which increases both the cycle time and cost per part. However, with very large castings it is more economical to use cast-in-place inserts since the cycle time is already increased due to the size of the cast part.

Examples of cast-in-place inserts

Post-installed inserts are more economical for faster run, smaller parts produced on highly automated machines and projects which have less stringent tolerances.

Interference fits
These types of fits are used to retain components, such as bearing and dowel inserts. If the interference is light (0.001 in./in [0.001 mm/mm] or less), the installation can take place with both parts at room temperature. Heavy interference usually requires the parts to be heated and may also cause metal removal which will lead to a reduction in retention. The removal of metal on the parts depends on the hardness of the metals, the amount of interference, lubricant use, and the leading edge of each part.

Threaded fasteners
Threaded bolts, or studs, are commonly used to join die cast parts together. If the attachments are made in sections with thin walls clearance holes are needed in order to allow the bolt to pass through. The bolt would then be secured in place with a nut.

Bosses are capable of being designed into the casting itself to receive bolts or studs into tapped holes. Though the boss diameter will need to be at least twice the size of the bolt’s diameter since die cast joints are more prone to dilation.

Also, keep in mind that in order to minimize porosity in the cast area where the thread is present, the tapped holes need to be cored. Both coarse and fine threads can be tapped although coarser threads are generally preferred.

The process of die casting and any secondary assembly operations have a symbiotic relationship; meaning they are heavily dependent upon each other and they work together to create the final product. Planning ahead for the assembly method you will use can help to minimize any potential problems as well as reduce costs and speed up production time.

Need a hand? With over 75 years of die casting expertise, our team of experienced engineers will evaluate your requirements to help you decide which would be the best fastener option to join your components to achieve the desired result for your part. Our in-depth knowledge and experience allows us to control the entire pre- and post-operative processing, as well as provide turn key part solutions with a variety of options, to meet our customer’s individual needs. Contact A&B Die Casting today to get started on your next project!

Design Assistance Brings Parts Online Faster

Design Assistance Brings Parts Online Faster

Asking for design assistance early in the process saves time and costs.

Atecs, Inc., produces high-quality products and services for aerospace and energy clients worldwide. Atecs uses their 64 years of experience to provide harsh-environment solutions for engine test, aero support equipment, constructed facilities, space flight components and energy service products.

When Atecs decided to introduce a fire-resistant version of their vent damping controller, die casting was an obvious choice for a part that needed to be strong, light, and fire-resistant. Since A&B also has a long history working with manufacturing clients, Atecs engineers shared their design with A&B engineers to make sure the part would be appropriate for die casting, as well as economical to produce.

A&B engineers carefully reviewed the client’s design requirements and suggested many ways to improve the original design.

1. The part had to perform under a heavy load of 85 pounds. A&B built fixtures and testing equipment to make sure the load requirements were met.
2. Quality and finish were critical. A&B modified the design of the boss on the original part to make trimming easier and also made modifications to eliminate flash in the gears.
3. Production and tooling needed to be streamlined. The original part design would have required complex tooling. A&B was able to simplify the tooling and help the customer bring the part online faster at a reduced cost.

Overall, A&B reduced the number of secondary operations that would have been needed, which helped to reduce overall production costs. The next time you start a design project, talk to our engineering team to see how we can help you make a product that is better than you imagined.

Better Products Through Better Design

Better Products Through Better Design

Partnering with your die casting vendor can result in better products in less time.

Vendors can be a valuable and often overlooked, resource in the early stages of product design. As an experienced provider of precision die castings, the engineering staff at A&B Die Casting has spent years guiding manufacturing customers through a careful design-for-manufacture review process to make sure their products are not only functional but economical to produce.

A&B staff engineers are always ready to help you with design assistance. The key to getting a better product is a careful evaluation of the application and design requirements of a component or assembly. Special care is taken to see how a new design can be optimized for the die casting process or how an existing design can be improved going forward.

How does this design-for-manufacture evaluation add value for A&B customers?
• Reducing assembly steps, weight and secondary operations.
• Improving product aesthetics.
• Driving down costs while improving the overall part.

Our dedicated and experienced engineering staff will work with you from early in your project until completion to help you choose the materials and methods that will deliver a better product every single time.

Better Tooling with Mold Flow Analysis

Better Tooling with Mold Flow Analysis

A&B improves the tooling design process with valuable simulations of mold performance.

Great castings start with great tooling. And great tooling starts at A&B Die Casting. One of the ways that A&B ensures their in-house tooling performs perfectly from day one is to run advanced computer simulations well before any physical tooling is made.

At the earliest stages of the tooling design process, A&B engineers utilize FLOW-3D Cast software to simulate the entire die casting process. Included in all A&B tooling quotes at no extra charge, mold flow simulations give A&B engineers valuable insight into how the molten metal will flow and solidify.

FLOW-3D Cast’s highly accurate flow and solidification simulations mean that engineers can test a number of ideas to determine the very best tooling designs. For example, one customer approached A&B with a part shape that was highly cosmetic. An A&B engineer tested several design iterations of gates and runners to reduce overflows to the absolute minimum. The integrity of the part was optimized, while easier cleanup of overflows produced a better appearance.

When you buy tooling from A&B Die Casting, we make sure it’s the best it can be.
• All design changes take place before any new die steel is cut, eliminating the costly process of discovering problems after the tooling has already been produced.
• A&B can quickly and reliably evaluate part designs from any CAD system to predict the effects of the casting process and tooling performance.
• Mold flow simulations are run on all in-house tooling designs at no extra charge.

Die casting fill of a 2-cavity mold:

Single cavity mold overflow view:

Engineering Gets F’Real

Engineering Gets F’Real

F’Real Foods and A&B Die Casting create a perfect mix of engineering and aesthetics.

F’Real Foods Inc. makes it possible to whip up your own milkshake, smoothie, or frozen cappuccino in less than a minute from real ingredients — real milk, real ice cream, real fruit — at the push of a button. F’Real designs and builds innovative self-serve blending machines that can be found at convenience stores, college and universities, theaters, and military bases throughout the United States and Canada. So, if you’re dreaming of a chocolate malt at 2 am, you can make it a reality.

F’Real Foods first approached A&B Die Casting with a new design for the machine component that holds and lifts the frozen milkshake cup into the blending mechanism.
A&B Die Casting capitalizes on innovation in high technologies, powerful flexibility, and inexhaustible engineering know-how to not just help customers improve their bottom line, but cross the line to new dimensions in quality and service.

To make sure each F’Real milkshake machine works flawlessly in thousands of locations, A&B was tasked with three key criteria for the design:
1. Produce parts efficiently and economically.
2. Create an aesthetically pleasing design reminiscent of old-time milkshake cups.
3. Maintain dimensional stability to work flawlessly in an automated machine.

A&B engineers worked closely with F’Real engineering staff to review the proposed one-piece design. After analysis, A&B recommended an assembly of three die castings that were each more stable dimensionally than the one-piece design. For the attractive metallic finish, A&B did some searching to find a ceramic coating that gave a perfect retro look of brushed stainless steel to the die castings.

• Make a product that is better than you imagined
• Save money with a design that is efficient to produce
• Get a quality product that maintains dimensionally stability in demanding environments