Quality Control 101: Common Defects in Aluminium Die Casting and How to Fix Them
In the die casting industry, the cost of poor quality is astronomical. Industry estimates suggest that internal scrap rates for unoptimized die casting processes can run as high as 10-15%, whereas top-tier manufacturers aim for less than 3%.
Defects don’t just waste metal; they compromise the structural integrity of safety-critical parts in EVs and industrial machinery. Here is a breakdown of the most common enemies of a perfect casting and how we defeat them.
1.Gas Porosity
The Defect: Small, round bubbles/holes visible inside the part after machining.
The Cause: Air gets trapped in the mold because the metal was injected too fast or the venting was poor.
The Fix: Using Vacuum-Assisted Die Casting to pull air out of the mold before injection, and optimizing overflow wells design.
2.Shrinkage Porosity
The Defect: Jagged, spongy holes found in the thickest sections of the casting.
The Cause: Metal shrinks as it cools. If a thick section cools too slowly without “feeding” more metal, a void forms.
The Fix: DFM (Design for Manufacturability). We redesign the part to have uniform wall thickness or use cooling channels (spot cooling) in the die to equalise temperatures.
3.Cold Shuts
The Defect: A visible line or crack on the surface where two streams of molten metal met but didn’t fuse.
The Cause: The metal cooled down too much before being filled into the mould.
The Fix: Increasing the injection temperature, speed, or modifying the gate positioning to shorten the flow path.
4.Flash
 The Defect: Excess thin metal protruding from the parting line of the die.
The Cause: Injection pressure forced the die halves slightly apart.
The Fix: Improving the die locking force (using a higher tonnage machine) or repairing worn-out die surfaces.