Causes analysis and improvement methods of bulges deformation in die casting.

Posted on : March 24, 2022 By  GREFEE

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What is die casting products bulging?

Bulges mean the protrusion of the local area of the surface. In some cases, it will generate fissures, which affect appearance and size.

Causes of bulges:

1.local area has air bubbles under the skin, the air bubbles inflate, or even exploding after molding.

2.The diameter eject-rod is small and the stressed area of ejection is small.

3.Pressure holding time is short. the mold open and eject without complete solidification.

4.The local surface of mold is damaged and sinks.

5.Slow injection speed is fast – the liquid alloy has air trapped when the material cup pushes inside. 

6.Rapid injection initiates early with fast speed, causing the air in the cavity has been exhausted in time. 

7.Exhausting groove position and structure are not suitable.

How to improve the problem of bulges in die casting?

Bulges are mainly measured visually or are easy to be found after the spray painting.

1.Only bulges without sinks, even bulging in the meantime — knock the bulge and shows it is empty. Adjusts the technique or the exhaust system to exhaust the gas. 

2.The eject-rod mark sinks evidently at the position with bulges – adjusts an eject-rod with a bigger diameter or adds up the number of eject-rod. 

3.The eject-rod mark sinks evidently at the position with bulges – strictly follow the pressure holding time according to the guides.

4.Knock the bulges and shows is solid not empty — repairs the mold.

5.Lower the full pressure injection speed.

6.Adjusts the rapid injection initiate position and speed properly – improves the exhaust groove and structure.

Key inspection areas of die casting parts

The opposite side has an ejector pin, whereas the thin or thick areas have bubbles.

How does bulge affect the products?

It mainly affects the appearance, especially the appearance part of baking paint. In some situations, the bulges will interfere with the assembly of products due to the negative influence on assembly positions.

Improves the bulges of die casting parts

In addition to the above reasons, temperature and vacuum environment are also the factors that cause bulges. When the mold temperature is too high, the products which have been cooled completely will have local bulge deformation. Sometimes, when the interior gas is too much, the gas will slip into the baking paint layer, causing bulge deformation.

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