Challenges of large casting design

By C.A. Lawton | November 17, 2021
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Large casting design is a high-stakes game: If you win, you’re a hero to your company and the OEM whose products they’re used on. If you lose, you tend to lose big. Here are some ways to increase your odds of success when designing large castings.

Because of their size and cost, castings over 2,000 lbs. present a number of unique challenges to design engineers and foundries:

The cost of R&D is very high: With smaller castings, the foundry can afford to sacrifice a handful of them to identify and solve any visible defects. It’s an accepted part of the iterative process of achieving a high-quality casting. With large castings, it’s hard to justify destroying even a single casting for the sake of R&D. To achieve high first-pass yield, The C.A. Lawton Co. must optimize the mold’s design to ensure consistent, low-cost manufacturability.

A strong dialogue with the customer is critical: The earlier in the design process the sales engineer can talk to a customer, the better. Lawton’s goal is to reduce the overall manufacturing cost of the end product while meeting the customer’s performance requirements.

The dialog throughout the process helps to ensure that the castings can be produced at a reasonable cost: What many design engineers don’t realize is that even seemingly simple changes to a part design – such as making a wall thinner – can make a casting significantly more expensive to produce. By eliminating cores, loose pieces, and change pieces, the cost of a large casting can be significantly reduced. Up-front dialog helps the Lawton sales engineer work through the trade-offs with the customer – what’s essential, and what can be eliminated or changed.

Customer education is essential: Many manufacturers tend to view castings as commodities. In reality, they are highly engineered products that must be customized to ensure maximum quality at a reasonable cost. For that reason, Lawton offers “Iron 101” and “Iron 102” courses to educate designers and purchasing managers on the many elements that go into creating a successful casting.

Many engineering managers who attend Iron 101 and are shocked by how little they actually know about the casting process. There is a specialized art and science to it. By attending these classes, they are better able to design parts that are more castable, at a reasonable cost.

Technology plays a bigger role: Because it’s not practical to do destructive testing of large castings, the casting engineer must rely heavily on flow and solidification software to optimize the design of the part. This software simulates how molten metal flows into a mold. It helps the casting engineer predict and eliminate defects so when the foundry casts the part, it’s made right the first time.

Lawton aims for a win-win-win

Often, Lawton’s large casting customers manufacture assemblies that go into a piece of equipment. Once in the field, the casting must hold up under a variety of application- and environment-related stresses. That means it’s essential to think through the durability of the casting all the way to its end-use.

The Lawton team pays close attention to cost and lead time. If the casting is too expensive, it could cause the end product to be too costly to meet market needs. If lead time becomes a problem, it could delay the launch of the OEM’s new machine by three to six months or longer.

Lawton’s philosophy is that its castings must be a win for everyone.