Reasons for undercasting of die castings

In the process of production, die castings will encounter many quality problems, which are common quality defects of die castings. Among them, undercasting is one of the defects. What causes undercasting of die castings are analyzed according to the knowledge as follows:

In the forming process of die castings, the filling of some parts is incomplete, which is called undercasting. When the Undercast part is serious, it can be regarded as the shape of the casting does not meet the requirements of the drawings. Generally speaking, undercasting is not allowed to exist.

The causes of undercasting are as follows:

1) Poor filling conditions, irregular condensation metal in Undercast parts;

When the pressure is insufficient, the metal solidification at the active front is too early, resulting in undercasting at the corner, deep concave, thin wall (even thinner than the average wall thickness), cylindrical hole wall and other parts.

Mold temperature is too low.

The pouring temperature of the alloy is too low.

The position of the inner gate is not good, which causes great resistance to movement.

2) Gas obstruction, surface lubrication of Undercast parts, but irregular shape

It is difficult to set up the parts of the discharge system and accumulate gas.

When molten metals move, turbulence is intense and gases are entrapped.

Residues in Plastic Mold Cavity

The improper amount of paint or spraying method results in local coating deposition.

The insertion gap of forming parts is too large, or the sliding cooperation gap is too large, when filling into metal, the casting can not be completely brought out after stripping out, showing a sheet clamped on the gap. When the sheet metal (the thickness of the metal sheet is the size of the gap) is protruded on the surrounding surface, the protruding height can be changed into the appropriate thickness of the casting under the condition of die closure, so that future castings will have trenches penetrating (for wall thickness). This penetrating groove is a special form of undercast. This phenomenon of undercasting occurs mostly in the case of deep cavity formed by mosaic.

Insufficient castables (including excessive savings).

In vertical die-casting machine, the lower punch is moved down to make the nozzle orifice inadequate, resulting in a series of poor filling conditions.

This article is organized by Foshan Jinju Qiwei Die Casting Co., Ltd., a die-casting manufacturer. The service hotline of aluminium alloy die-casting is 0757-25500218! Website: http://www.jjqw.com/.