Why Choose Metal Casting?
Pouring molten metal into a sand, metal, or ceramic mold is one of the most common ways to mass produce a complex part. According to the American Foundry Society, highly engineered metal castings are part of 90 percent of durable goods. And since metal casting is one of the oldest industrial manufacturing processes, you’re never more than 10 feet away from a part that was created that way.
Foundries mix custom combinations of elements, iron, aluminum, magnesium, zinc, steel, and copper to create different appearances, corrosion resistance, and strength characteristics. When castings are removed from their molds they are near net shape with minimal finishing work needed.
Alternatives to castings are fabrications, forgings or parts machined from bar stock. Some non-cast parts are required to be made in multiple pieces and welded together. Compared to the alternatives, metal casting is more cost-effective and produces stronger parts.
Cost-effective Production of Complex Parts
Metal casting is a more cost-effective option for mass producing complex parts because of time, material, and overhead savings alone. When original equipment manufacturers (OEMs) convert a machined and welded part to single form casting, they often cut their production costs and timeline by nearly 50%.
Multiple castings can be made at once, and since they are in near net shape when removed from the mold, little to zero time is needed to machine the parts into their final dimensions and finished look. Additionally, with high-grade material and the capability to cast walls as thin as 1/8 of an inch, foundries like Stainless Foundry & Engineering can produce complex parts without heavy duty stress concentrations.
A single form cast part can be more structurally sound than a welded machined part because welded seams can weaken over time. Foundries combine metals to create alloys with different chemical properties and varying levels of strength. Stainless Foundry & Engineering pours more than 250 alloys for different applications. Our alloy casting table provides details on some of our more popular alloys.
The pattern used to make casting molds last through thousands of impressions and years of use, producing the exact same measurements every time. They also are easily replicable when needed.
The Differences between Investment Casting and Sand Casting
The investment casting, or lost wax process involves wax injected into an aluminum die block. The wax impression is removed from the die, then dipped in a slurry to create a ceramic stucco shell. The wax is melted out of the shell and then heated in an oven to prepare for pouring. Then molten metal is poured in the shell. Once cooled, the ceramic outer layer is removed and the part proceeds to a cleaning room for final cutting and grinding.
Figure 1 – Investment Casting Process
Investment casting is preferred for its near net shape with a close tolerance to the final finished part and a naturally smooth finish. Investment casting creates the same accurate part over and over, within thousands of an inch. While investment casting is ideal for highly complex designs – it can cast 1/8-inch walls at the thinnest and work with both ferrous and non-ferrous metals – investment casting does have weight and size limitations. It is more costly than sand casting and requires longer lead times.
The sand casting or sand molding process uses a wood or Polyurethane pattern set in a box to create the shape of the part. Sand mixed with a chemical bonding agent is dumped into the box, compacted and allowed to harden. Then the mold box is stripped and the mold halves are washed with a chemical agent to reduce mold/metal reaction. If the product has internal passage ways, a core is set in one mold half before the two mold halves are closed. Now the molten metal is poured into the mold. Once cooled, the sand is removed and the parts proceed to the cleaning room for final cutting and grinding operations.
Figure 2 – Sand Casting Process
Sand casting achieves net shapes within a quarter of an inch and has a rougher surface finish. Parts are machined to achieve the exact tolerance and look for the finished part. Sand casting is more versatile with size and weight capabilities than investment casting. Nearly any part configuration that can be made in another material can be produced using sand casting.
Investment and sand casting are reliable, cost-effective, quality manufacturing processes that allow for flexibility in budgets, timelines, and design. If you are considering the design of a new part to be cast, or exploring how converting from machining to casting could save time and money, please contact us. Our engineering team can get you the information you need to determine if casting is right for you.
Stainless Foundry & Engineering
Posted on: 2019-05-22 09:34:20