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What is the Reason Why Die Casting Manufacturers Encounter Under Casting During the Die Casting Process?

May. 12, 2020

As a Die Casting Parts Supplier, share with you. Die casting is a metal casting process characterized by the use of mold cavities to apply high pressure to molten metal. Molds are usually machined from high-strength alloys, some of which are similar to injection molding. Most die castings are iron-free, such as zinc, copper, aluminum, magnesium, lead, tin and lead-tin alloys and their alloys. Depending on the type of die casting, a cold chamber dies casting machine or a hot chamber die casting machine is required. Casting equipment and molds are expensive, so the die casting process is usually only used for mass production of large quantities of products.

Zinc Alloy Die Cast Part

Zinc Alloy Die Cast Part

The reasons for the lack of casting in the process of die casting are:

(1) Poor underground conditions, poor filling conditions, irregular metal condensation; walls (even thinner than the average wall thickness), cylindrical hole walls, etc. are primed. The mold temperature is too low; the alloy pouring temperature is too low; the position of the inner gate is not good, forming a large resistance to movement. 

2) The gas is blocked and the surface of the casting part is lubricated, but the shape is irregular. It is difficult to open the overflow system and gas is accumulated; when the molten metal moves, the turbulence is intense and the gas is entrained.

3) Residual paint or spraying method in the cavity of the plastic mold is improper, resulting in local paint deposition. The insertion gap of the molded part is too large, or the sliding fit gap is too large. It will penetrate into the metal during the filling process, and after removing the casting, it cannot be completely removed, but appears in the form of a thin plate sandwiched in the gap. When the type of metal plate (thickness is the size of the gap) is more protruding to the surrounding contour, when the mold is closed, the height of the protrusion will be changed to a wall thickness suitable for casting, so future castings will have penetration here (For wall thickness) grooves. The penetrating groove becomes a special form of underground casting. In the case of deep cavities composed of mosaics, this phenomenon of insufficient casting occurs. Insufficient pouring (including excess material is too thin). On vertical die casting machines, the lower punch is not sufficient to open the nozzle hole during the injection process, which can result in a series of poor filling conditions.

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