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Most common die casting defects during production

by Adhecogen

A Die Casting Machine, also known as a Hot-Chamber and as a Gooseneck Machine
Tiny bubbles and surface imperfections appearing on a mold made out of steel and zinc.

Zinc is one of the most malleable metals; many similar pieces need to be manufactured for it to be easily worked. For this, die casting is the cheapest and most effective technique. Molds in this type of production usually last between 60,000 to 100,000 castings.

 

What are the main errors in the zinc die casting process?

The zinc dies casting process is highly effective and inexpensive but is not error-free. During the production process, many faults are inherent to the technique, which can affect the quality of the product if not corrected.

Surface imperfections: Since steel has a higher melting point than Zinc, it can be used as a mold to make many different parts without losing its shape. However, the heat does dilate the steel, creating tiny bubbles and imperfections in the zinc contents.

Alloy problems: The quality of the metal alloy is one of the main factors that define the final result in the casting process. If the alloy is too malleable, the part will lose its shape once it is used, but if it is too solid, it may fracture.

Impurities: There are harmful contaminants commonly found in Zinc die casting alloys, including iron, lead, tin, cadmium and other elements. A certain amount of lead, tin and cadmium in the alloy can cause low strength, intergranular corrosion and changes in volume and size. The alloy’s quality will not be affected if these impurities are minimal.

Dioxide slag: Molds with corners may not receive sufficient ventilation, which causes the slag to oxidize; this causes a fracture that may be yellow or whitish and can be found during anodizing, pickling or alkaline washing. The fracture can also be discovered by mechanical processing, fluoroscopy or X-ray; this affects the strength and quality of the part.

How to solve Zinc die casting problems?

First, the purity and proportion of the metals used in the alloy must be analyzed. An adequate balance of metals guarantees that the part will be resistant and functional and suffer minor wear and tear.

During the Zinc die casting process, it is essential to follow the cycle correctly and at the correct temperature so that the part obtains the expected shape and strength. The combustion process also produces gasses that must be regulated, and the resistance to corrosion and oxidation depends on them.

In the case of imperfections, the metal parts can be polished to eliminate unnecessary reliefs and give a better finish and functionality to the piece.

Outgassing Zinc die casting

Outgassing describes the phenomenon of trapped gasses released during the melting process. When this gas passes through the coating, it creates tiny holes, which are not visible on high-quality-looking parts. Causes of outgassing can be attributed to substrate material, a surface contaminant, or the powder applied.

One method to avoid outgassing problems is to preheat the part. Before applying the powder coating, the part must be preheated at a temperature above the curing temperature of the powder coating. Additionally, the preheating process will take the same amount of time as the curing process, allowing the part to release trapped gasses before the curing process.

For any custom design solutions, contact ADHECOGEN.