How to Avoid Die Casting Defects

Die casting is a cost-efficient and rapid method for producing high-volume metal parts in materials like zinc, aluminum, and magnesium. The process involves using custom molds, high-quality die-cast tools, post-process machining, and finishing.

However, producing die-casting parts can be complex and doesn’t always guarantee flawless results. Given that die casting involves injecting molten metal into a mold under high pressure, various factors can affect the quality of the finished products. Failing to address these casting defects can compromise the end product’s quality. Here, we’ll discuss some common die-casting defects and strategies to avoid them.

Gas porosity

Gas porosity occurs when bubbles form in the casting after cooling, creating oval or round structures on die-casting parts with smooth yellow or white surfaces. This defect can be caused by gases trapped during the metal-filling process, mold-releasing agents, or the release of hydrogen from the molten metal. To prevent gas porosity, consider these measures:

  • Melt the raw material in a vacuum or under flux to minimize air exposure to the molten metal.
  • Keep the metal alloy ingot dry and clean.
  • Use discernible injection speeds and precise die-casting parameters.
  • Opt for high-quality mold-releasing agents in suitable amounts.
  • Design the runner and sprue lengths to allow the molten alloy to release gases effectively.

Shrinkage porosity

Shrinkage porosity appears on die-casting parts during solidification and cooling as metal alloys naturally shrink. To minimize this issue:

  • Improve the casting structure overall.
  • Redesign the gate system and incorporate risers to maintain molten metal flow.
  • Regulate casting temperatures.
  • Use cooling aids like coils, ribs, or internal chills for efficient heat dissipation.


Typically caused by metal impurities, inclusions can result in irregular holes on or within die-casting parts. This defect can also arise from low furnace charge purity and interactions between the metal, mold surface, and atmosphere. To prevent inclusions:

  • Ensure the furnace charge is pure.
  • Purify the liquid metal by removing slag.
  • Clean ladles and die cavities thoroughly.
  • Mix and stir mold-releasing agents well, particularly those containing graphite.

To avoid defects in die-casting parts, be sure to work with a die-casting expert like HLH Proto. We collaborate closely with our clients to design well-crafted parts with minimal errors, aiming to reduce their time to market and manufacturing costs. For a comprehensive project review and a free quote, reach out to us.


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