Difference between Gravity Casting and Low pressure Die Casting

Low Pressure Casting
Using dry, clean compressed air, the aluminium liquid from the holding furnace is pressed smoothly from the bottom up into the mould cavity of the casting machine through the riser and pouring system, and then the pressure is maintained until the casting has solidified and the pressure is released. This process fills and solidifies under pressure, resulting in the good filling, less shrinkage and high denseness of the casting.

Gravity casting
Gravity casting is a process in which the metal liquid is injected into the mould by the force of gravity on earth, also known as pouring.

So what are the similarities and differences between low-pressure casting and gravity casting?
- Mould selection: Both are divided into metallic and non-metallic types (e.g. sand type). Metal type moulds are relatively expensive to purchase; while wood-type moulds are less expensive to purchase, but if they are not used for a long time or need to be mass produced, a certain amount of maintenance costs will occur.

- Production efficiency: low-pressure metal casting is easy to achieve automatic beat production and high efficiency; resin sand mould shape and internal core box can only be used once and production efficiency is lower.

- Material utilisation: low-pressure casting is suitable for the production of thin-walled castings, and the riser takes up very little material; gravity casting is not suitable for the production of thin-walled castings and requires a riser. (A riser is a supplementary part attached to the top or side of a casting to avoid defects in the casting. The gate is the head of the part and the riser is the tail of the part to see if the cavity is filled to saturation and both need to be removed.)

- Casting materials: Gravity casting for ferrous and non-ferrous metals. Low-pressure casting is mostly used for non-ferrous casting; alloy materials are more expensive and low-pressure casting can reduce riser losses.

- Worker labour environment: low-pressure casting is mostly mechanised, with a good labour environment for workers; while gravity casting has a poor labour environment for workers, especially when carrying out pouring operations.