Defects of Die Casting Parts and Solution

Defects of aluminum die casting parts

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• FLOW MARK

Mark looks like stripe shown on the surface of aluminum die casting parts.

The factors that cause problem

1. Two flows fill up cavity at different speed.
2. The temperature of mould is low.
3. Speed for filling up is too high

Solution

1. Adjust of gate dimension.
2. Increase mould temperature.
3. Adjust speed for fill up

• COLD SHUT

The problem happen if melted alloy are not hot enough in cavity.The melted alloy do not go into each other.So there will be a line shown on the surfaces of aluminum die casting parts.
The factors that cause problem

1. Melted alloy or Mould temperature is low.
2. Alloy quality is not good.They can not flow very well.
3. Melted alloy fill up cavity in several times.
4. Runners are too long
5. Speed for filling up is low

Solution

1. Increase tempeture of mould and melted alloy
2. Good quality alloy
3. Improve design of mould
4. Improve ventilation
5. Increase injection speed

3)SCRATCH

The problem happen if metal is stick to mould surface or not proper draft.

The factors that cause problem

1. Draft is not very well
2. There are scratchs on surface of core.
3. The surface of mould is not smooth.
4. The proportion of iron in aluminum alloy are lower than 0.6%

The solution

1. Improve mould draft
2. Polish the surface of core
3. Improve injection system.Lower speed if necessary
4. Proper aluminum alloy
5. SHRIKAGE

There are some areas that shrik on the surface of castings

The factors cause problem

1. Design of castings are not good
2. Shrikage rate is high for alloy
3. Gate dimension is too small
4. Temperature of mould is too high.
   The solution
5. Make uniform wall thickness
6. Improve shrikage rate
7. Improve injection system
8. Add cooling system on mould5)BLISTER

The gas generated underneath surface of castings.It looks like bump on the surface.

The factors cause problem

1. Temperature of mould is too high.
2. Filling speed is too high and get too much air into mould.
3. Vantilation is not well
4. Open mould after injection too earlier.
5. Temperature of melted alloy is too high.

The solutions

1. Cool down mould
2. Lower filling speed
3. Improve vantilation

• BLOWHOLES

There is hollow inside die casting parts but nothing happen on surface.

The factors cause problem

1. Gate is not well
2. Runner design has problem
3. Not filling up
4. Speed too high
5. Not proper vantilation
6. Cavity is too deep

The solution

1. Make proper gate and runner
2. Filling up fully
3. Lower fill speed
4. Put insert in deep area of cavity for good vantilation

7)POROSITY
The problem appear if flows do not fill up totally.

The factors cause problem

1. Melted alloy temperature is too high.
2. Not uniform wall thickness
3. Gate is small
4. Temperature of mould is high

The solutions

1. Lower melted alloy temperature
2. Improve inner design of casting
3. Fully filling
4. Improve injection system

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