Die Casting Mold Optimizations | Improve Efficiency - Dynacast

A high-quality die cast component starts with high-quality tooling. The quality of your die cast tool not only determines the tolerances you’re able to hold and how many shots you can get out of a single mold, but also the repeatability, strength, and complexity you’re able to achieve throughout the life of your project.

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We’ve covered what drives the cost of your die cast tool as well as the top three reasons Dynacast tooling is more precise, but now we’d like to cover our tooling manufacturing process, capabilities, and what to take into consideration when purchasing a die cast tool. Discover why optimizing tool design and partnering with an experienced tooling supplier is critical to the success of your component’s production and gaining the most ROI from your project.

What is die cast tooling?

Tooling, or the die cast mold, contains a cavity in which molten metal is injected and formed. Once hardened, the tooling is separated into multiple pieces, allowing for the removal of the castings. Dynacast offers both our proprietary multi-slide die cast tooling, as well as conventional die cast tooling. Each method offers unique strengths depending on the specifications and scale of the project.

The tool design process

At Dynacast, all of our die cast molds are manufactured and produced with high-quality steel at our tooling division in Germantown, Wisconsin. There are twenty toolmakers and three design engineers at this facility with over 40 years of tooling experience.

When designing the tooling, our team of engineers takes into consideration all aspects of the mold and the end-part itself—from material selection, potential runner sites, tolerance stackups, and more. State-of-the-art magma flow software helps to analyze the castability of certain design features and the best sites for runner systems and cooling ports before the tool is manufactured. Features like cooling ports limit the amount of tool wear, prolonging the life of your die cast tool and ensuring an even porosity and high strength in the final casting.

Designing for optimal manufacturability

All of the value engineering that goes into designing the tool for success and longevity before the mold itself is cut is part of the Dynacast core concept, designing for manufacturing (or, DFM). When it comes to die cast tooling, designing for optimal manufacturability is what makes a true high-quality die cast tool. Not only does DFM expediate the tool design process by delivering a successful tool that will last the life of the project, but also makes for a more consistent, high-performing component than lower-quality tools.

Tooling care and maintenance

Aside from engineering a high-quality die cast tool, tooling care and maintenance should always be top of mind for your die cast supplier. While our tooling is designed for longevity, repeated cycles of heating (to over °F) and cooling will inevitably degrade the tool over time. Tools experience gate erosion and core wear, requiring occasional light maintenance during their service life. As with most machinery, adherence to a rigid maintenance program extends the lifespan of the tool and ensures the consistent and timely production of high-quality parts. And depending on your alloy selection and process, some tools require more maintenance than others.

For example, with proper design and maintenance, multi-slide tooling for zinc components can withstand approximately one million shots before needing replacement, while conventional tooling for aluminum components can withstand roughly 200,000 shots.

The average number of shots a tool can withstand varies depending upon project requirements, selected materials, and component complexity, among other variables. To get an accurate assessment of your project’s tool life, please consult with one of our engineers.

With tool wear taken into consideration before the mold is cut, your tooling maintenance and likelihood of total tool replacement is greatly reduced. At Dynacast, all tools are kept in “like new” condition throughout the life of your project. And when the tool requires maintenance to retain its “like new” condition, your maintenance is covered. All of our tooling maintenance programs are incorporated into the cost of your tool up-front—so when you invest in your die cast tool, you’re making a one-time investment over the entire life of your tool.

Getting the most ROI from your die cast tool

When choosing a die cast supplier, manufacturers want to know they’re getting the most ROI out of every step of their production process—including tooling. Some manufacturers may be tempted to cut corners by purchasing a cheaper, lower quality tool. While these tools may incur a lower up-front ticket price, they virtually guarantee greater investment down the line in the form of costly, unnecessary maintenance, tool replacement, and part defects. By investing in higher quality tooling, manufacturers are able to recoup greater ROI with prolonged tool life, lower scrap yield through the life of the project, and improved part performance.

In addition to being weary of a lower ticket prices, there are a few things manufacturers can do to engineer value into their die cast tools. When designing your component, the following should be considered to ensure a robust and long-lasting tool that produces high-quality parts:

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• Be mindful and plan for flexibility when it comes to draft angles. Increasing draft angles of non-critical design elements allows for easier part extraction, which extends the service life of the tool
• Allow for lenient tolerance zones on non-critical design elements
• Get involved with your supplier as early as possible! Collaborate with our team of engineers to make adjustments unique to your specific part early on in the design phase to avoid costly re-designs.

Every part is different, but we are here to help. Get in contact with our team of engineers to get started on optimizing your tool design and engineering value into every step of your manufacturing process today.

Before we get into the specific design tips, let’s take a look at the primary principles that make for successful die casting:

• The molten metal can easily flow through the mold, filling it to produce a solid part.
• The metal solidifies evenly and quickly.
• The part ejects without damaging itself or the tooling.
• The part design minimizes the complexity of the tooling required.
• The part function is prioritized over its shape.
• Tolerances should be kept as open as possible without affecting the fit, form, or function.

By keeping these principles in mind and utilizing the tips below, you will be well on your way to producing a design that can be reliably and economically made. If you have an upcoming die casting project, feel free to start a quote with us today! Our representatives and subject matter experts are here to help guide you through the process and help answer any questions you may have.

Implementing both fillets and radii in your design can be beneficial in several ways. Firstly, they help the metal evenly flow through all areas of the part and reduce concentrated areas of heat around corners and transitions. These are also important features to prevent cold shuts, caused when the metal begins solidifying before it has completely filled the mold cavity. Components that cool evenly lessen the stress on the tooling, thus increasing its lifetime and reducing maintenance. Fillets can also reduce stress concentrations, especially where intersecting features would otherwise create sharp corners. Here are some further guidelines when it comes to adding fillets and radii:

• Add fillets or radii to sharp edges and corners.
• The deeper the corner or pocket, the larger the fillet should be.
• Fillets create smooth transitions between features that promote metal flow and structural integrity. Radii should be generous on intersecting features.
• Constant-radius fillets help maintain edge continuity and smoothness of the part.
• Draft angles are required when the fillet is perpendicular to the parting line. The draft of the intersecting surface will determine the amount of draft needed.

When it comes to wall thicknesses, the most crucial aspect is uniformity. Keeping the walls of the part uniform will help promote metal flow and uniform cooling. Areas with uneven wall thicknesses can cause different shrinkage rates, leading to defects in the part, such as sink marks or cracks. Here are some other considerations to make when it comes to wall thicknesses:

• Molten metal flows more freely with thicker walls.
• Certain alloys such as zinc can produce parts with thinner walls.
• Avoid prominent protruding features that significantly increase wall thickness, which can cause uneven and slower cooling rates.

Ribs are structural features that provide several benefits in die cast parts. Their primary purpose is to provide additional rigidity and strength, especially to areas with thin walls. Ribs also assist the molten metal flow, allowing it to reach and fill connected areas more quickly.

Adding corings, such as the space between ribs or walls, helps reduce material as a metal-saver and provides better cast parts. The purpose of coring is to displace the casting alloy, reducing material usage and resulting in a lighter-weight part. With the proper use of ribs and coring, you can avoid areas of concentrated heat caused by excessive material buildup while also reducing the weight of the part and maintaining its strength. When incorporating ribs and cored features into your design, it’s essential to keep the following in mind:

• Designers should add ribs onto thin-walled sections.
• Design for an odd number of ribs to better distribute internal stresses and avoid forming thick intersections.
• Add fillets to ribs and edges of metal savers to reduce sharp corners and assist with metal flow.
• Avoid having too many ribs too close together, as this can affect the effectiveness of metal savers.
• Include generous draft on the sides of metal saver pockets to assist with mold release and prevent tool wear.

Special consideration should be given to hole and window features, as they present their own unique challenges with the die casting process. The inside surfaces of holes and windows tend to adhere to surfaces of the steel die during the cooling process. This can impact the ejection mechanism and make it harder to release the part from the die, contributing to tool wear and part defects. Additionally, holes and windows can impede metal flow through the casting. Additional techniques such as bridge features or runners can be used for larger windows to ensure proper metal flow; however, this can add extra steps and cost to trim out these features after casting. If your design requires holes and windows, the design guidelines below will help keep your part manufacturable:

• Holes and windows require the highest draft compared with other features.
• Perimeters of holes and windows should be filleted.
• In some cases, it may be better to post-machine holes; however, this will add manufacturing time.

Parting lines are where the die halves meet and interface with each other. When designing your parts, the parting line locations are one of the first aspects to consider. Parting lines can be straight or broken depending on the geometry and die components required to create them. When it comes to the parting line locations, here are the key aspects to consider:

• Parts with straight parting lines will usually be less expensive than one that requires broken parting lines since less complex tooling is needed.
• Quality along parting lines is more difficult to control; therefore, you should avoid having it cross critical or tight tolerance features.
• Parting lines often exhibit flash, a thin web or fin of material that occurs due to the clearances needed for die operation. Flash is removed during trimming, and it should be easily accessible.

The as-cast external surface finish classification should be specified in your design. The class you choose can significantly influence the end cost as higher-grade finishes require additional steps and a more sophisticated die design. That said, you should aim to select the lowest classification that meets your intended application to yield lower costs.

The North American Die Casting Association (NADCA) has guidelines to help you classify your surface finishing requirements in a general sense. Please reference the chart below for these classification guidelines. Note that this is useful for general type classification, and final finish quality requirements are agreed upon between the customer and manufacturer.