How does the gravity die casting process work?
Gravity die casting was one of the very earliest processes to be invented for metal and light alloy die casting. In this process which can be fully automated, the molten metal is poured directly from a ladle into a semi-permanent or permanent die.
The goal is to fill the die with minimum turbulence through one or more channels to reduce oxidation and foaming. This minimises porosity and inclusions, giving optimum metal characteristics in the final casting.
Gravity die casting equipment can have a vertical or horizontal mould opening, or tilting technology with 0/90 ° or 0/120 ° tilting provides an alternative. With tilting die-casting, the metal flow at the die inlet is controlled by the tilting angle and speed of the die.
Advantages of the tilting gravity die casting process
One of the advantages of tilting gravity die casting is that it can produce dense, high quality castings with excellent mechanical attributes like strength and stiffness. That makes it very suitable for demanding automotive applications like brake system and suspension components.
Gravity die casting technology’s main advantages include:
- Suitability for high-volume, automated production
- Minimum investment required for small and medium volume production
- Produces parts with excellent mechanical properties that are also suitable for heat treatment
As sand cores can be placed within the mould, gravity die casting can also produce parts with complex shapes.
Application
Gravity die casting technology is ideal for diverse complex aluminium casting production of automotive parts such as: turbos, brake calipers, knuckles, engine cylinder heads, engine blocks and pistons. It suits many other industries too, from lighting components to kitchen tools.
Discover our gravity die casting solutions here:
- Gravity die casting machines and cells:
Integrated solutions for the gravity foundry, with complete flexibility and customization, from design to technical support during production. - Turnkey Fully Automated Cells:
Flexible, fully automated work cells for light alloy casting production. We engineer automated work cells for three die casting processes: high pressure die casting, gravity die casting and low pressure die casting.
Compare High Pressure Die Casting (HPDC) and Gravity Die Casting (GDC)
Process: Gravity Die Casting uses gravity to fill the mould, while Pressure Die Casting employs pressure to inject the molten metal into the mould.
Speed & Volume: Pressure Die Casting is faster and more suited to large-volume production. Gravity Die Casting is slower but produces stronger components.
Design Complexity: Pressure Die Casting is better for complex designs with intricate features and thinner walls. Gravity Die Casting, although capable of high dimensional accuracy, isn’t as good at handling very complex shapes.
Porosity & Strength: Parts produced through Gravity Die Casting are less porous and, therefore, higher strength. Conversely, pressure-cast parts may have reduced strength.
Cost: Again, it’s a balance we have to look at: Gravity Die Casting may be more cost-effective for smaller production runs due to lower setup costs, but Pressure Die Casting is usually more economical for larger volume. It’s faster and can be automated.
Do pressure die casting and gravity die casting have a difference in quality?
Pressure die casting can make very precise and complex castings achievable. Due to the rapid filling of the mould under pressure, castings are dimensionally accurate with thin walls which are also very smooth, reducing the need for secondary finishing or machining.
Although gravity die casting will not match these benefits, the slower speed at which molten metal enters the mould does mean that less folding and turbulence occurs. As a result, less air is trapped in the casting, offering a distinct advantage if casting integrity is important, or if it needs future heat treatment.
Do Pressure Die Cast Parts and Gravity Die Cast Parts Use Different Materials?
Pressure die cast parts and gravity die cast parts can use similar materials, but some alloys may be better suited for one process over the other.
As high pressure diecasting allows the production of thin wall sections, alloys with good fluidity can maximise this benefit. However, the choice of material depends on the specific requirements of the part - such as strength, corrosion resistance and weight - as well as production process and cost considerations.
Do Pressure Die Cast Parts and Gravity Die Cast Parts Have Different Applications?
Due to the differences in their manufacturing processes and resulting properties, pressure die cast parts and gravity die cast parts often have contrasting end uses.
In general, pressure die casting is preferred for producing more complex or lightweight parts that require tight tolerances and higher production volumes. Gravity die casting is typically used for heavier sectioned parts, orparts that do not require as much precision and can be produced more cost-effectively in smaller quantities.
The choice between the two processes depends on the specific requirements of the project, including part size, complexity, material, and production volume. By speaking to the experts at NSD, we can help you to choose the best process to benefit the final application of your component.
Ready to discuss a casting idea?
NSD partners are experts with over 75 years’ experience in the manufacture of high-quality aluminium die castings, across a wide range of applications and industries.
As we can see, Gravity Die Casting and Pressure Die Casting have unique strengths and weaknesses. The choice between the two depends on factors such as volume, complexity, strength requirements, and of course, budget. We can help with all your casting questions and guide you through to what’s best for you and your customers.
NSD VINA CO., LTD - Industrial Solutions
Add: 03, Violet 1, Vinhomes Gardenia, Nam Tu Liem, Hanoi, Vietnam
Tel: 024-6688-2448
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