Precision casting, also known as lost wax casting, strikes a perfect balance between artistry and precision engineering.

It’s called precision casting because of its ability to create parts with extreme accuracy, achieving tight tolerances as fine as +/- 0.005.

This process is unique, setting it apart from other die-casting methods.

Wax patterns are crafted to prepare an initial ceramic mold, tailored to replicate parts with either highly complex or simple designs.

Lost Wax Casting Process

For parts where achieving tight tolerances is crucial, lost wax casting is used to replicate them from an exact model.

This method allows for the creation of parts with thin walls that, if not intricately designed, often require no surface finishing.

The lost wax casting process involves several steps:

Casting Steps 1-5

1. Model Making: A 3D CAD model of the parts is created, accurately replicating the part’s size, dimensions, and other measurements. This step is crucial for creating an aluminum die.
2. Creating a Mold: A mold is created based on the 3D CAD model, typically using aluminum, which will later be used to produce wax patterns.
3. Wax Pattern Creation: Manufacturers create wax patterns that precisely replicate the original CAD design from the aluminum die using casting wax. The wax, in its semi-solid form, is poured into the die and adjusted to ensure complete coverage. This process is repeated as necessary based on production scale. For producing multiple parts, these wax patterns are connected using a runner.
4. Shell Building: After assembling the wax patterns into a group, the shell-building process begins. The wax mold is dipped into a ceramic slurry, which coats the patterns, forming a hard exterior shell. A small portion of this wax tree is left uncoated to allow the removal of the wax later.
5. Dewaxing: After coating the wax tree, the dewaxing process begins. The casting wax is completely removed from the ceramic shell by baking it. At this stage, the ceramic shell is ready to produce your parts, and this is where the process earns its “lost wax” name.

Casting Steps 6-10

6. Burnout: To ensure no residual wax or moisture remains in the ceramic shell, the wax mold undergoes a burnout process at temperatures around 1035°C. This step not only removes any foreign materials but also solidifies and hardens the ceramic mold.
7. Casting: The burnout process prepares the ceramic mold for casting. Molten metal is poured into the mold, flowing within the ceramic tree with the aid of gravity and pressure, distributing the metal precisely to each part of the mold.
8. Cooling and Shell Removal: Once the metal solidifies, the ceramic shell is removed. This can be done using a hammer, blasting, high-pressure water, or sometimes chemicals. After removing the ceramic shell, the runner is cut away, and the parts are individually separated.
9. Surface Finishing: While parts from lost wax casting often don’t require surface finishing due to their already perfect state, some highly intricate parts may undergo additional finishing processes, such as sandblasting, to remove any residual ceramic or scales.

Variations in the Lost Wax Casting Process

The lost wax process can have many variations, but the one described here is considered standard.

For example, after burnout and before casting, there may be an additional step where the mold is preheated.

The best variation for your parts depends on their design and material.

Lost Wax Casting Metals

Lost wax casting is compatible with a wide range of metals, making it highly versatile.

It works with aluminum, steel, bronze, stainless steel, iron, brass, and more.

Aluminum and its alloys are particularly ideal due to their machinability and corrosion resistance.

The fluidity of aluminum allows for casting parts with thin walls, and when alloyed with other materials, its strength and physical properties can be further enhanced.

Advantages of Lost Wax Casting

In today’s technologically advanced manufacturing landscape, lost wax casting remains a strong contender due to its minimal limitations on part dimensions, size, and design.

• Material Compatibility: It can cast parts for nearly every industry and application without design or material limitations. From aluminum to nickel and other metals, lost wax casting handles them all.
• Smooth Finishes: Most parts don’t require additional surface finishing because the natural finish from lost wax casting is excellent.
• Size Range: Lost wax casting can easily handle parts of any size, dimension, or design complexity and cast them to perfection.
• Production Turnaround: Lost wax casting is a fast and repeatable die-casting process, ideal for high-volume production, with parts ready for shipment immediately after casting.
• Tight Tolerances: The process allows for tight tolerances of up to ± 0.005.
• Production Costs: Lost wax casting requires less time, resources, and manpower, resulting in lower overall production costs.
• Waste Elimination: The process generates little to no waste, and any leftover material can be reused, making it highly efficient.
• Complexity of Designs: Parts produced are lightweight and full of intricate details, offering design flexibility and the ability to choose from nearly any material.

Applications of Lost Wax Casting

Lost wax casting finds applications across various industries, providing precision benefits:

• Aerospace: Outlet manifolds, seal/flaps, bearing housings, vertical supports, airline engines, jet engine airfoils, bearing supports, and nozzle guides.
• Automotive: Engine components, fuel systems, compressor parts, aluminum space frames and suspension systems, gearbox components.
• Oil & Gas: Gate valves, slip linkages, tube handling devices, valve brackets, elevator parts, locking levers made from aluminum, stainless steel, and alloy steel.
• Chemical: Bullhead tees, static cast fillings, catalyst tubes, heater hardware, elbows, and ethylene coils.
• Food: Meat slicers, racks and grills, various poultry processing tools, parts for ice machines.
• Medical: Medical implants, surgical tools, and other medical instruments.

Comparative Analysis with Other Casting Methods

While other casting methods like die casting excel in certain areas like surface finishing and material compatibility, they may fall short in terms of design intricacy.

Lost wax casting, on the other hand, allows for intricate detailing with minimal post-processing for a smooth surface finish.

Conclusion

Lost wax casting’s ability to work precisely with various materials, including aluminum, makes it one of the leading casting processes.

Hengke Metal specializes in aluminum die casting, delivering superior results for your metalworking projects.

Contact us to discuss your die-casting needs.