The three processes involved in making non-ferrous castings
Sand casting, gravity die casting and high-pressure die casting compared: costs, accuracy, surface finish and where each suits non-ferrous castings.
While working with the finest non-ferrous metals, the guesswork in the engineering process is eliminated by adopting specialised casting techniques and methodologies that deliver aluminium components to match client specifications. Iron-free metals such as zinc, tin, lead and magnesium possess unique properties that are put to use by innovative product-shaping processes.
The most popular metals cast for industrial applications are aluminium alloys, copper-based alloys and zinc alloys. Non-ferrous castings can be made using one of the following three processes: the sand casting process, the gravity process and the high-pressure die casting process.
Processes used in making non-ferrous castings
- Sand casting process
Considered one of the simplest methods for producing non-ferrous castings, sand casting is the most economical process of the three. The castings take shape when molten aluminium, zinc or copper is poured into a sand mould.
The sand casting process is chosen for a few reasons: producing a small number of castings, castings with complex or intricate shapes, or very large castings.
With a sand mould, the largest casting sizes can be achieved thanks to its general versatility. The disadvantage, however, is that production times are longer than with the other two processes.
- Gravity die casting process
The gravity die casting process makes use of steel or cast-iron moulds that allow aluminium or zinc castings to be produced more accurately and at a lower cost. A better surface finish, as well as excellent mechanical properties, can be achieved through this casting process.
The tooling cost is a fraction of that needed for pressure die casting. Non-turbulent mould filling ensures that gravity castings have minimal porosity.
Gravity die casting machines usually have a range of microprocessor-controlled hydraulics that mechanise the movements of the die. They offer tilt pouring and up to four axes of hydraulic movement.
- High-pressure die casting process
High-pressure die casting is the shortest route from molten metal to the finished component. It is done by injecting molten metal into a sturdy steel mould and allowing it to solidify under the pressure created inside the mould before ejecting it.
The high-pressure die casting process allows precise, quick and cost-effective production using aluminium or zinc as raw materials. This process meets the needs of high-tech industries where dimensional tolerances and product appearance are critical.
Most high-pressure die casting machines have locking forces ranging between 220 and 530 tonnes. Other features of this process include automatic ladling, real-time shot control, and automatic casting extraction and cooling.
Aluminium castings produced using one of the above-mentioned processes have applications in the automotive industry for cylinder heads, engines and manifolds. They are also used in electrical appliances, cooking equipment and the food packaging industry.
