For Us as a new one, Die Casting means gravity die casting process is a highly technical and complex process, however in reality, it is actually quite simple. It can help to think of it as a method of conversion or a way of turning one thing into another; that is, turning a molten liquid metal – such as aluminium or zinc – into a metal cast part or component. This conversion is permanent, and it can be broken down into just a few easy and understandable steps.
In the following blog, let’s take a look at each of these steps in detail, explaining exactly how the gravity die casting process works and outlining what type of products it can be used to make.
A Guide to Gravity Die Casting in 5 Steps Step-by-Step
Step 1: Preparation
Before the gravity casting process can begin, the first step is to prepare the die itself. Essentially, this involves heating it up to a suitable temperature and spraying it with a refractory coating or lubricant. Not only does this lubricant maintain the temperature of the die during the manufacturing process, but it also prevents premature solidification and aids the removal of the cast once it has set.
The die halves can be closed and clamped tightly together using high pressure.
Step 2: Injection
Following this preparation stage, molten metal is then taken from a furnace and ladled directly into the die via a downward sprue. This can either be done manually or, in some circumstances, using an automated ladle; but either way, the process takes advantage of gravity. No additional forces or pressures are applied. The molten liquid is simply inserted into the die from an upright, vertical position and it makes its own way down into the cast due to the natural pull of gravity.
By avoiding the use of high-pressures, turbulence is significantly reduced and this – in turn – helps to prevent porosity and leads to the production of much smoother components and parts.
Step 3: Cooling
Once the molten metal has been inserted into the cast, it is then left to cool and solidify. The metal should be given sufficient time to take the shape of the mould and it needs to be completely set before the die is unclamped. Removing the cast prematurely can lead to irreversible defects.
Step 4: Ejection
After a sufficient period of time has passed, the die halves are then unclamped and opened, and the cast parts are carefully removed. This can either be done by hand or, in some situations, ejector pins are used to push the cast safely out of the gravity die casting machine.
Step 5: Trimming
The final stage of the gravity casting process is trimming. As the metal continues to cool, any scrap metal – including the gate, runners, sprues, and flash – are expertly removed from the casting. A variety of tools are used to take away any sharp edges and excess material, thus creating the desired component shape, and the part is usually cleaned before despatch to the customer.
