Die casting process has become quintessential to manufacturing across industries, and therefore sits at the center of our supply chain strategies. Minimising costs on this widely used process is critical to improve profitability. Read more about the to-dos for reducing your costs with die casting.

Die casting is a process of injecting molten material into a mould cast under high pressure. The mould casting is made of two halves, typically from non-ferrous alloys of steel.

Casting of components is a relatively simple process, with low incremental costs. However the machining of the moulds itself requires high capital, and therefore this process is used for high volume requirements.

There are many factors that contribute to the complexity and thus cost of the die casting process. Here we look at 9 ways of designing your components to reduce costs:
  1. Minimise the number of undercuts
    An undercut is a shape in the component that obstructs its withdrawal from a mould without additional operations. They are classified as external and internal undercuts based on whether they’re located on the exterior or inside the part.

    Molding undercuts requires side actions that can add 15-30% to the overall cost. This is due to an increase in machining complexity and longer cycle times. Thus the fewer undercuts in your design, the more economical your die casting will be.

  2. Minimise the wall thickness
    Keep wall thickness of components as close as possible to the minimum acceptable level required for the application. This reduces the cycle time (injection time and cooling time), and volume of material consumed.

    Decreasing the volume of raw material required has a direct correlation to the component cost. Shorter cycle times also reduce the production cost, hence thin walls are the preferred choice for die casting.

  3. Keep wall thickness uniform
    Designing walls with varying thickness can result in uneven cooling, causing deformation of the cast components. They include the formation of bubbles, hot tears, ejector marks, dimensional inaccuracies etc.

    A high number of components with defects ending up in the reject pile greatly increases production costs. Not only do the time and resources spent on bad products go to waste, but also more inefficient cycles are required to meet the desired final output.

  4. Use fillets and radii in the mould cast
    Sharply angled corners in the design cause stress concentration and possible fracture of the cast. Avoid this by including fillets (inner corners) and radii (outer corners), which provide rounded corners, in your design.

    Bear in mind that increasing radius too much can induce shrinkage porosity. Thus your design needs to use optimum dimensions.

  5. Minimise number of side-action directions
    Instead of just two halves of the mold coming together to form the part, another piece (or pieces, as required) is created that moves in from the side. This allows surfaces to be formed that would otherwise not be possible, while the part is easily released from the molds.

    This refers mostly to the use of side-cores to cast components with undercuts. Each additional direction typically increases component costs by 10-20% in addition to the tooling cost itself. Even if your production needs side-actions, try to align them all to one side to reduce die casting costs.

  6. Include appropriate draft angles
    All component walls parallel to the parting direction require to be offset by a small angle to facilitate their removal from the mold. Here are some standard draft angles, based on the material being cast:

    Aluminum: 1° for walls, 2° for inside cores
    Magnesium: 0.75° for walls, 1.5° for inside cores
    Zinc: 0.5° for walls, 1° for inside cores

    Holes and windows require more draft, compared to inside and outside wall features. Using incorrect draft or excluding it can result in damaged components and extended production times.

  7. Include ribs (and webs)
    Ribs (and webs) can increase stiffness and add strength to the component, resulting in a lighter part that’s more sturdy. In fact, a thin wall with ribs is sturdier than a thicker wall of uniform width. The resulting component is both lightweight and durable.
    Remember to use an odd number of ribs in your design. This eliminates the buildup of stress across to an adjacent rib and reduces the formation of thick intersections.

  8. Design sturdy bosses
    Bosses are integral features added to a casting, typically to serve as stand-offs and mounting points. A boss may also refer to a mounting feature that will receive a screw or thread-forming screw.

    Use ample fillets and ribs in your design to ensure that molten material can easily flow into the boss area. Avoid surface shrinks by using ribs to connect a boss to a wall. Designing bosses poorly can result in the entire mold needing to be redone, so be sure to pay attention to details.

  9. Decide on hot chamber vs cold chamber casting
    Hot-chamber casting machines feature a built-in furnace in which metal is heated to achieve a molten state. Whereas in cold-chamber casting, the metal is heated in a separate furnace before being fed into the casting machine.

    Hot chamber casting can only be used with materials that have low melting points. It reduces the lifetime of the mold cavity, but speeds up cycle times. Typical cycle times are as short as 15-20 mins.

    Materials with high melting points require cold chamber casting. Higher mold cavity life, but longer cycle times. Production times are usually in multiples of those for hot chamber casting.

    Keep this in mind while choosing the material and type of casting for your parts.

We hope these methods help you design better and reduce your expenditure on die casting.

At Zetwerk, we leverage our global network of manufacturing hubs to deliver a wide range of manufacturing products. With 15,000+ MT/month fabrication capacity and 500+ custom projects executed, we are a reliable partner to outsource your manufacturing.

Contact us if you’d like help with optimising your design, or any manufacturing process.

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