What key points should be noted in the structural design of castings?

In addition to meeting the requirements of the machinery and equipment itself and the machinability requirements, the structural design of castings should also meet the requirements of the casting process. The following points should be noted in the structural design of castings:

I. It should be convenient to manufacture molds, core boxes and perform molding:

1. The external shape of the casting should be as simple as possible to facilitate demolding. The casting parting surface should be a plane as much as possible, and the number should be minimized.

2. The inner cavity of the casting should try not to use or use as few cores as possible during casting. When using cores, it should be convenient for their support, fixation and exhaust and sand removal. If necessary, there should be sufficient process holes.

3. For the internal and external side surfaces and reinforcing ribs of the casting, there should be a certain structural slope in the demolding direction.

4. The boss part on the casting should not differ too much from the casting body. It is best to have the same height. Several bosses on the same surface that are close to each other are best connected into an integral raised part.

II. To reduce the tendency to produce casting defects:

1. The wall thickness of the casting should be as uniform as possible to prevent shrinkage cavities and hot cracks. When the sequential solidification conditions need to be ensured, the wall thickness should be made to change in one direction as much as possible. When the simultaneous solidification conditions need to be ensured, the cross-section wall thickness should be made as equal as possible.

2. The connection between the walls of the casting should strictly prevent sharp corners and metal accumulation. The transition between thick walls and thin walls should be gradual and sudden changes should be strictly prevented to avoid hot spots and stress concentration, resulting in hot cracks, shrinkage porosity, etc.

3. The local thick section of the casting should use hollowed-out or cast hole structures as much as possible and be properly reinforced with reinforcing ribs.

4. The cast holes on the flat wall of the casting should be reinforced with convex edges to reduce the wall thickness.

5. The casting structure should be designed so that it can contract unobstructed during cooling as much as possible.

6. Large horizontal planes in the casting should be avoided as much as possible.

7. For large-area sandwich cavities such as water passages and gas passages in the casting, there should be several connecting columns.

III. To ensure good formability of the casting and control that the minimum wall thickness of the casting is not lower than the allowable value.

Source: China Foundry Association.