Die Casting Defects Causes and Solutions Part One

From more than a decade of professional die casting process experience, Sieg-Huao has summarized 10 types of common die casting defects and obtained a complete set of preventive measures.

One: Flow marks and patterns

Appearance Inspection: In the surface of the diecast product there are grains in the same flow direction with the metal liquid, and obvious non-directional pattern which has different color with the metal matrix, and no development trend.

The reasons for this phenomenon: 

1) Mold temperature is too low.

2) The sprue is poorly designed.

3) Material temperature is too low.

4) Low filling speed and short filling time.

5) The pouring system is not reasonable.

6) The venting is poor.

7) Irrational spray.

The solution and prevention methods:

1) Adjust the area or position of the sprue.

2) Improve the diecast temperature.

3) Adjust the runner speed and pressure.

4) Select appropriate paint and adjust dosage.

Two: Turtle crack

Appearance Inspection: In the surface of die castings there are reticulated and hairy humps or recessions, and it enlarges and extends as the number of die casting increases.

The reason for this phenomenon:

1) There are cracks on the surface of the die casting mould.

2) Preheating of die casting mould is not uniform.

The solution and prevention methods:

1) The diecast mould should be regularly annealed to eliminate the internal stress of the cavity.

2) If the surface of the cavity has been cracked, the surface should be polished and the crack layer removed.

3) Preheat the mould evenly.

Three: Cold Shut

Appearance Inspection: In the surface of diecast products there are obvious, irregular and linear pattern, and the shape is small and narrow. Sometimes the edge is smooth, and there is a possibility of disconnection under external force.

The reasons for this phenomenon:

1) Die casting temperature or casting temperature is low.

2) The runner is not in the right position.

3) Filling speed is low.

The solution and prevention methods:

1) Raise the casting temperature properly.

2) Increase the pressure.

3) Improve the exhaust and filling conditions.

Four: Shrinkage Depression

Appearance Inspection: In the surface of castings there are smooth grooves (like dishes)

The reasons for this phenomenon:

1) Wall thickness differs a lot.

2) The cooling system design is not reasonable.

3) The die casting temperature is too high.

4) Open die prematurely.

The solution and prevention methods:

1) The wall thickness should be uniform, the thickness of the transition should be moderate.

2) Reduce pouring temperature and mold temperature properly.

3) Local temperature should be partially cooled.

4) Improve discharge conditions.

Five: Contact trace

Appearance Inspection: In the contact surface between castings and die casting cavity there are contact trace or ladder trace.

The reasons for this phenomenon:

1) The adjustment of ejector pin is inconsistent.

2) The mounting part is loose.

3) The removable part is loose or got damaged.

The solution and prevention methods:

1) The ejector pin length should be adjusted to the appropriate position.

2) Tighten the block or other moving parts.

3) Improve die casting structure to eliminate the insert form of die casting mould and improve die casting mould structure.

To be continued...