What is Die Casting Overflow - Design Tips of Die Casting Overflow

The performing of the die casting process relies on the mold with a specific shape, overflow is part of the die casting mold, which has an impact on the quality of castings. In this article, let’s learn about the overflow in die castings, including its definition, uses, and design.

What is Overflow in Die Casting?

Overflow in die casting mold refers to the cavities and passages used as a vent for air escape and a trap for the flow of excess metal. Die casting overflows can reduce the porosity in the die casting parts and assist the molten metal fill in the mold cavity. 

What Does Die Casting Overflow Do?

– Remove the cold dirty metal liquid such as gas, coating, and residue in the cavity, cooperate with the exhaust slot to quickly lead out the gas in the cavity.

– Control the flow state of liquid metal filling to prevent local eddy current.

– Transfer the location of shrinkage cavity, porosity, air hole, and cold lap.

– Adjust the temperature of each part of the die, improve the thermal balance of the die, and reduce the flow marks on the casting surface, cold shut, and insufficient pouring.

– Help the casting demould and set out to prevent casting deformation or thimble marks on the casting surface.

– The total volume of the overflow groove accounts for 10% – 30% of the alloy content. Considering the cavity volume and casting wall thickness, the overflow area is 60% – 75% of the nozzle area; The overflow thickness is 0.25-0.5mm, and the overflow thickness shall not be greater than the inner gate thickness to ensure the pressurization effect. The overflow is connected with the exhaust tank to reduce the pressure in the chamber and discharge gas. The quantity depends on the number of positions required.

Design Tips of Die Casting Overflow

1. Set it at the place where the metal flow initially impacts to exclude the condensed metal flow entering the cavity at the end, and the volume is slightly larger than the condensed metal flow.

2. It can be set at the place where the two metal flows meet to eliminate the cold insulation of die castings, and the volume is equivalent to the metal volume in the range of cold insulation.

3. It can be arranged around the cavity, and its volume shall be enough to remove the liquid metal mixed with gas and the gas in the cavity.

4. It can be set at the thick parts of die casting, and its volume is equivalent to 2-3 times the volume of hot joint or shrinkage defect.

5. It can be located where the vortex is easy to occur, and its volume is equivalent to the cavity volume of the vortex generating part.

6. Set it at the place where the mold temperature is low, and its volume is suitable to improve the mold temperature distribution.

7. It can be set at the dead corner on both sides of the inner gate, and its volume is equivalent to that of the die casting defect.

8. It can be set at the position with poor exhaust, and the push rod shall be set at the back.

9. Set an integral overflow tank to prevent deformation of die castings.