Cleaning, Finishing & Machining

Finishing and machining operations can have a significant impact on the overall cost of a casting. The labor involved, time spent and equipment needed to remove excess metal or machine features can drive up the cost, which encompasses more than simply the materials needed to make the casting. Total cost also includes, labor, energy, tooling, etc. Although there are several fixed costs, the casting processes offer several ways to reduce costs in other areas. By exploiting the ability of casting processes to produce complex shapes and internal passageways, machining can be minimized significantly. And by producing near-net-shape components, cleaning and finishing costs can be drastically reduced.

“Now more than ever we are working with our customers to reduce weight, take out stock and reduce machining because it can be more expensive than the casting,” Marlatt said. “In most metalcasting facilities, the cleaning room is the biggest cost driver because there are so many operations that are still being manually performed. Cleaning and finishing equipment is self-destructive; the less pressure required, the greater the opportunity to reduce costs.”

That opportunity comes from the casting design. Features, such as holes and passageways, can be cast-in to save money. These require cores, which add cost but may be more cost-effective than machining or cleaning and finishing operations.

“Determine if there are features you can design that will save money in the cleaning room,” Marlatt said. “You have to understand your customer’s cleanliness criteria. If a parting line of ± 0.79 in. (20.7 mm) is acceptable and the process is capable of holding that, grinding will not be necessary. And, if the gating system can be designed so it breaks off cleanly (and the metalcasting facility can keep the process within those limits), you might be able to eliminate or limit the amount of gate grinding.”