Die casting problems and design


The problem

Pouring line overflow

Requirements for the straight runner of the die on the cold chamber horizontal die casting machine:

① The diameter of the pressure chamber should be selected according to the required specific pressure and the full degree of the pressure chamber. At the same time, the deviation of the inner diameter of the gate sleeve should be appropriate to enlarge a few wires than the deviation of the pressure chamber diameter, so as to avoid the problem of punch stuck or serious wear caused by the different diameter of the gate sleeve and the pressure chamber, and the wall thickness of the gate sleeve can not be too thin. The length of the gate sleeve should generally be less than the ejection lead of the ejection punch to allow the paint to come out of the pressure chamber.

② The inner hole of pressure chamber and gate sleeve should be polished after heat treatment, and then grinded along the axis direction. The surface roughness is less than or equal to Ra0.2μm.

③ The concave cavity of the shunt and the formation of the coating, the concave depth is equal to the depth of the runner, the diameter of the gate sleeve diameter, along the direction of the demoulding has a 5° slope. The filling degree of the pressure chamber can be improved by shortening the effective length of the pressure chamber.

Mould requirements

① The entrance of the horizontal runner of the cold horizontal mold should generally be located at more than 2/3 of the inner diameter of the upper part of the pressure chamber, so as to avoid the metal liquid in the pressure chamber from entering the cross runner prematurely under the action of gravity and beginning to solidified in advance.

② The cross-sectional area of the cross runner should be gradually reduced from the straight runner to the inner runner. In order to expand the cross section, negative pressure will appear when the liquid metal flows through, which is easy to inhale the gas on the parting surface and increase the eddy current gas trapping in the liquid metal flow. Generally, the outlet section is 10-30% smaller than the inlet section.

③ The cross runner should have a certain length and depth. The purpose of maintaining a certain length is to stabilize the flow and guide the flow. If the depth is not enough, the liquid metal cooling fast, the depth is too deep, because the condensation is too slow, both affect the productivity and increase the amount of return charge.

④ The cross-sectional area of the runner should be greater than the cross-sectional area of the inner runner to ensure the speed of liquid metal entry. The cross-sectional area of the main runner shall be greater than that of the branch runner.

⑤ The bottom of the runner should be rounded on both sides, so as not to appear early cracks, two sides can make about 5 degrees of slope. The surface roughness of the cross runner is less than or equal to Ra0.4μm.


① The parting surface should not be closed immediately after the metal liquid enters the type, and the overflow groove and exhaust groove should not impact the core positively. The flow of liquid metal into the type as far as possible along the cast ribs and heat sink, from the thick wall to the thin wall filling.

② When choosing the location of the inner gate, the liquid metal flow should be as short as possible. In the case of multi-spool inner gate, it is necessary to prevent the convergence and mutual impact of several strands of metal liquid after entering the mold, resulting in defects such as eddy current air inclusion and oxide inclusion.

③ The thickness of the inner gate of the thin-walled parts should be smaller to ensure the necessary filling speed. The setting of the inner gate should be easy to remove, and do not make the casting body have defects (meat).

The overflow tank

① The overflow groove should be easy to remove from the casting, and try not to damage the casting body.

② When the exhaust groove is opened on the overflow groove, attention should be paid to the position of the overflow port to avoid blocking the exhaust groove prematurely, so that the exhaust groove does not work.

③ Should not open several overflow openings or open a very wide and thick overflow opening on the same overflow tank, so as to avoid the cold liquid, slag, gas, paint and so on in the liquid metal to return to the cavity from the overflow tank, resulting in casting defects.


Under the premise of satisfying the product function, reasonable design of die casting, simplify die casting die structure, reduce the cost of die casting, reduce the defect of die casting and improve the quality of die casting parts. Because the injection molding process is derived from the casting process, the die casting design guidelines are in some ways very similar to the plastic design guidelines. For detailed design of die casting parts, refer to the book “Guide to Product Design for Manufacturing and Assembly” published by China Machine Press.

Rounded corners

(including the Angle) the casting diagram is often marked with no fillet R2 and other requirements, we should not ignore the role of these fillet when we open the mold, never make a clear corner or too small fillet. The casting round corner can make the liquid metal fill smoothly, make the gas in the cavity discharge in order, and can reduce the stress concentration, prolong the service life of the mold. (The casting is also not easy to crack or various defects due to improper filling). Standard oil pan die supernatant Angle more, relatively speaking, at present brother oil pan die open the best, heavy oil pan is also more.


In the direction of the demold, it is strictly prohibited to cause the side concave (often the casting is stuck in the mold when the mold is tested, and the wrong method is used to deal with it, such as drilling, hard chiseling, etc., so that the local concave).


Molding parts, pouring system should be in accordance with the requirements of careful lighting, should follow the direction of stripping lighting. It takes only 0.01-0.2 seconds for the liquid metal to enter the pouring system from the pressure chamber and fill the cavity. In order to reduce the resistance of liquid metal flow, the pressure loss as little as possible, need to flow through the surface of the finish is high. At the same time, the heating and erosion conditions of the gating system are relatively bad, and the worse the finish, the more easily the mold is damaged.

The mold forming part of the hardness of aluminum alloy: HRC46° or so copper: HRC38° or so processing, the mold should try to leave a repair margin, do the upper limit of size, avoid welding.