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What to consider when choosing the right casting process.
Casting is one of the oldest manufacturing techniques dating back to 1838. While the basic casting process hasn’t changed much, today’s machines are more advanced and with improvements in technology, there are a several different ways to reach your end product—or part so to speak. Two common and very similar processes are die casting and investment casting. Keep reading and we’ll discuss the difference between each process and help you to understand the advantages and disadvantages of each so that you can choose the right process for your next project.
The Die Casting Process
Simply put, when die casting a part, molten metal is injected into a hardened steel die cavity. When the metal solidifies it is ejected from the tool and the process is repeated. The process varies slightly depending on the material you choose—see hot chamber and cold chamber die casting. The hardened steel Mould is capable of creating anywhere from 150,000 shots to over a million shots before it would need to be repaired or replaced.
The Investment Casting Process
Creating a part using the investment casting or “lost wax” process is typically a more time-consuming process where a wax prototype of your part is made and then repeatedly dipped into liquid ceramic. The ceramic hardens and then the wax is melted out leaving you with a ceramic Mould. Molten metal is then poured into the ceramic cavity where the wax once was. Once the metal solidifies, the ceramic Mould is broken and removed leaving the metal casting. The Mould used to create the wax pattern can be used many times however the ceramic Mould is broken and discarded with each part. However, Signicast has automated every aspect of the investment casting process making one week lead times possible where the industry average is 8-16 weeks.
Which Process Is Right for My Project?
No two casting projects are the same and with different projects, there are different solutions. Here are a few things to consider before you start your next project to help you choose which process is right for your component.
Most die cast parts are made from non-ferrous metals like zinc, Aluminium, 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.
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.
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.
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 Labour 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!
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. It is best to speak with an experienced casting engineer to determine which casting process is best suited for your next project—contact our team today!