Aluminium Castings

Aluminium Castings are moulds that produce metal components when molten aluminium is poured into them. Once cooled, which happens very quickly, the actual component is created. The moulds can be made from sand or metal.

To choose the right aluminium casting alloy from DAC Industries, match your choice to your project goals. Select LM25 for strong, pressure-tight, weldable load-bearing parts, or LM4 for general-purpose use that requires high wear resistance and easy machining.

Common Casting Alloys & Uses

LM25 (Al-Si7Mg): Heat-treatable with great corrosion resistance and impact strength. Best for automotive structural parts, aerospace fittings, and pressure-tight housings.

LM4 (Al-Si5Cu3): General-purpose option with medium corrosion resistance, high wear resistance, and good machinability. Best for standard automotive castings. [1]

Key Selection Factors
Strength & Load: Choose heat-treatable alloys like LM25 for structural integrity.
Machinability: Choose LM4 if your part requires extensive post-casting machining.
Environment: Look for high silicon/magnesium mixes if corrosion resistance is vital. 

The main difference is the mould material and reusability. Sand casting uses a one-time-use mould made of compacted sand, ideal for complex shapes and low volumes. Gravity die casting uses a reusable metal mould (steel or iron), relying on gravity to fill it, which gives a smoother finish and higher strength for large production runs. 

Sand Casting
Mould: Made of sand mixed with a binder; destroyed after each cycle.
Tooling Cost: Low initial setup cost.
Surface Finish: Rougher as-cast surface texture.
Best Uses: Prototypes, large or highly complex parts, and low-volume production. 

Gravity Die Casting
Mould: Made of durable metal (steel or cast iron) and reused many times.
Tooling Cost: Higher initial investment for the metal dies.
Surface Finish: Smooth surface with high dimensional accuracy.
Best Uses: High-volume manufacturing, structural components, and parts needing repeatable strength. 

You can read more detailed comparisons on our Blog: Sand Casting vs Gravity Die Casting: Which Is Right for Your Project? 

Yes, aluminium castings can be machined. Our post-casting operations routinely include machining and finishing to achieve tight tolerances, smooth functional surfaces, and exact dimensions required for sectors like automotive and aerospace. 

Machining Considerations for Aluminium Castings

Alloy Choice: Different aluminium alloys (such as those heat-treated to T6) offer good machining characteristics. 

Casting Method: Sand castings often require more post-machining due to wider tolerances and rougher surface finishes, whereas gravity or pressure die castings yield smoother near-net shapes that minimise required machining.

Process Steps: Castings undergo trimming, deburring, and CNC machining post-solidification to produce final component features like holes, threads, and mating surfaces. 

Yes, aluminium castings are routinely heat-treated. Our thermal processing alters the metal's internal microstructure to optimise mechanical characteristics such as tensile strength, hardness, and dimensional stability. 

Key Heat Treatment Processes

Solution Heat Treatment: Heating the casting to 500°C–550°C to dissolve alloying elements into a solid solution, followed by rapid water quenching. 

Quenching: Rapidly cooling the material post-solution treatment to lock elements in a supersaturated state. 

Ageing (Precipitation Hardening): Reheating the alloy to a lower temperature so particles precipitate out, substantially increasing overall strength. 
Stress Relieving: Heating below solution temperatures to clear residual mechanical stresses and prevent later cracking. 

Yes, DAC Industries produces metal prototypes. They use an air-set sand casting process, which has low initial tooling costs, making it ideal for one-off prototype parts and small batches before moving to full-scale production. 

Prototype Services

Air-Set Sand Casting: Best suited for low-volume prototypes and complex shapes in materials like aluminium, brass, bronze, and zinc.

CAD & CNC Pattern Making: Patterns for prototypes are created using modern CAD models and CNC machines for accuracy.

On-Site Machining: Offers full machining capabilities from prototypes up to full-scale production runs. 

We don't publish a fixed, generic lead time because delivery windows depend heavily on the specific casting method, tooling requirements, alloy availability, and order volume. We utilise forward-planned scheduling and real-time data to provide realistic, project-specific estimates rather than quoting ideal conditions. 

Key Factors Affecting Lead Time

Casting Process: Sand casting typically features shorter initial tooling lead times and flexibility for small batches, whereas gravity die casting involves a longer upfront tooling and development phase followed by faster production cycles. 
Design & Tooling: Upfront design optimisation and complex die manufacturing directly influence total project timelines before production casting begins. 
Material Availability: Sourcing specific non-ferrous alloy grades can alter schedules, though the foundry works with customers to propose compatible alternative grades or adapted processes if delays occur.