What is difference between Low-pressure permanent mold (LPPM) casting and high pressure die casting? how we should to choose? what is the advantage and disadvantage between them; there many customer don’t know the exactly difference between them? therefore we will talk it more detail. keep reading.
As you know, LPDC is one type of permanent mold casting, and cold chamber die casting both metal casting process. they use different machine, also different ingot. besides their character is different.
The characteristics of low pressure die casting
1. There are few sand holes in the casting, heat treatment can be carried out, and the strength of the product can be greatly improved after heat treatment, like make T4 and T6(A356) even exceeding the die casting product.
2. The product has low density and is formed by liquid self-weight. The compactness of the product is lower than that of die casting, and its strength is also slightly worse, but its elongation is higher.
3. The surface finish of the product is not high, and the surface of the cast product is easy to form pits after cooling and shrinking.
4. Slow filling, low production efficiency, and its production efficiency is only 1/4 of high pressure casting, resulting in higher product cost.
5. The life of gravity die casting mould is longer than that of die casting, and the cost of the mold is lower.
6. The process is simple
7. Not suitable for the production of thin-walled parts
The characteristics of die casting
1. Fast filling, high production efficiency
2. Forming under high pressure, product compactness, product strength and surface hardness are high, but the product elongation is low.
3. The surface finish of the product is good, generally reaching Ra3.2.
4. Can produce thin parts with thin wall thickness, aluminum die-casting wall thickness can be as thin as 0.5mm
5. Fast filling, internal gas entrapment, poor product porosity
6. can not be heat treated, the internal gas will expand when heat treatment, resulting in defects such as bulging or cracking of the product.
7. The processing allowance is small (as small as possible is less than 0.25mm), the processing volume is too large, the surface dense layer is destroyed, and the internal pores are exposed, resulting in a decrease in product strength.
8. Die casting mold costs are high. Short mold life.
Gravity vs High vs low pressure die casting
| Comparison | Process | Mold Price | Mold Life | Sand Hole | Heat treatment | Machining allowance | Smooth surface | Suitable product | Production Efficiency |
| High pressure die casting | Complex | High | Short | Exist | None | Small | High | Thin wall parts | High |
| Low pressure die casting | Simple | Low | Long | Less | Can | Big | High | General Parts | Middle |
| Gravity die casting | Simple | Low | Long | Less | Can | Big | Low | Thick-walled parts | Low |