Question

Describe the steps involved in carrying out investment casting. Use appropriate illustrations to clarify your answers. Compare and contrast the capabilities and limitations of the investment casting and die casting processes.

Answer 1

basic steps of the investment casting process are

Production of heat-disposable wax, plastic, or polystyrene patterns
Assembly of these patterns onto a gating system
“Investing,” or covering the pattern assembly with refractory slurry
Melting the pattern assembly to remove the pattern material
Firing the mold to remove the last traces of the pattern material
Pouring
Knockout, cutoff and finishing.

Comparison b/w investment casting and die casting

Material Selection
Most die cast parts are made from non-ferrous metals like zinc, aluminum, and magnesium. Investment casting is capable of casting cast those metals along with ferrous metals, including stainless steel. If you are looking to use a non-ferrous material, both processes offer comparable features. However, if you are looking to use stainless steels or copper alloys, investment casting is the better option.

Annual Volume
When deciding which casting process to use, decide what your desired payback period is for the tool cost. How many parts created versus the cost of the tooling to “break even.” While investment casting tooling may be cheaper and suitable for lower volume projects, die casting is ideal for larger production runs and high-volume projects.

Tolerance
With any casting process, tolerance capabilities are largely influenced by the shape of the part and the type of material used. The table below compares general linear tolerances for conventional die casting and investment casting. The multi-slide die casting process is capable of holding even tighter tolerances.

Cycle Time
While investment casting and die casting both produce complex parts, the cycle times differ greatly. Traditional investment casting is a timely process that requires quite a bit of labor and hours of work, while die casting can produce 3-4 shots per minute for conventional die casting and upwards of 45 shots per minute with multi-slide die casting. A die cast part can often times be created without the touch of a human hand—complete automation!

Cost
Cycle time determines up to 60% of your final part cost so it is no surprise here, that per part, investment casting generally costs more than die casting. Its highly manual processes yield parts very similar to that of a die casting, but the cycle time is much longer.

When casting in high volume, die casting is more cost effective than investment casting. If you are casting only a few parts or require larger size or stainless steel, investment casting may be the lower cost option.

While both investment casting and die casting create parts with comparable features, when extremely high-volume manufacturing is desired, the associated costs and longer cycle times can make investment casting a less-suitable option depending on your needs and deadlines.