Meeting the Need for Speed

Rapid manufacturing enables metalcasters to provide fast, flexible solutions.

Denise Kapel, Senior Editor

(Click here to see the story as it appears in April's Modern Casting.)

A variety of additive and subtractive methods exist to produce quick-turn metal castings for applications ranging from proof-of-concept prototypes to high quality preliminary runs and into full production.

Once an experimental field, with some players excelling while others succumbed to economic pressures, rapid manufacturing is hitting its stride. And as engineers and other metalcasting professionals from modern industrial programs move up the ranks, they are bringing their ability to implement these technologies to the forefront.

Competitive Advantage

With an ever growing interest in lean manufacturing practices across all industries, technologies that enable just-in-time supply chain management are gaining traction.

“There’s a point at which production tooling makes sense, but rapid prototyping allows you to ramp up to production quantities and processes as demand for the product increases,” said Reg Gustafson, vice president of business development for Clinkenbeard, an M2M Group company in Rockford, Ill., with 17 vertical milling machines for subtractive mold and coremaking. “The rate of change on this ramp is not always easy to forecast,” he said. “Rapid prototyping allows flexibility and forgiveness to the process. It also allows design changes on the fly.”

Decisions made during the casting design process have far-reaching consequences. “Many manufacturing and performance issues created at this stage have long-term impact on product cost,” said Tom Prucha, vice president, techical services, American Foundry Society, Schaumburg, Ill. Rapid manufacturing technology enables designers and metalcasters to evaluate samples ahead of full production as well as make adjustments as needed.

“You’re losing market share if you can’t bring [a casting] to market when the customer demands it,” said Steve Murray, a consultant with Hoosier Pattern Co., Decatur, Ind., which uses additive sand printing (binder-jetting) equipment for rapid manufacturing. “Metalcasting is competition on price: What is the cheapest way to produce the foundry tooling necessary to get the job done? So, we don’t use a process to make a casting cost more. We use a process or a technology to make it cost less.”

Determining the Right Method

The right process to use, whether traditional patternmaking or rapid, is specific to each job.

“The typical use of additive manufacturing creates a one-off object that can only be used one time, while other rapid prototyping techniques can create either one-off objects, like an expandable pattern for lost foam or investment casting, or tooling that can be used multiple times for low volume runs,” Prucha explained.

While rapid manufacturing usually bears a price premium versus traditional tooling methods, it offers benefits that offset the cost.

“There is no cost in additive manufacturing for complexity,” Murray said. “In a way, the more complex the casting, the cheaper it is.” He offers the example of a casting with 20 or more cores that have to be assembled, whereas with 3D sand printing, they can be produced all at once without concern about whether the pieces are then put together correctly.

Additive manufacturing options involving 3D metal printing are lacking in scope for metalcasting patterns, coreboxes and tooling, according to Prucha. “Efforts are underway to create smaller pieces, but print size, part density and the types of metal that can be deposited currently limit its use,” he said.

Rapid methods for lost foam casting can be additive or subtractive, by printing a foam block or CNC machining pieces to be assembled into a pattern. Prucha offered the example of an assembly consisting of eight fabricated parts, which is now produced as one lost foam casting produced by CNC machining the foam patterns.

Subtractively CNC machining sand molds offers advantages when producing a very large part.

“Many of the RP systems can’t handle a very large envelope. And if they can handle it, it takes a long time to additively build up layers,” said Gustafson. “If you have a part that’s 10 or 15 inches tall, it takes a lot of time and there’s a cost there.”

Sand mold and core material composition is more flexible with subtractive methods. “We can tweak the binder levels and the type of sand we use to the production process,” Gustafson said. “So if we can get the process sheets from a production foundry, we can mimic that exactly. For instance, a magnesium foundry might make a sand mold with all the inhibitors or other things that might be metered into the sand as the molds are made, give us the block and we can machine it.”

A single company probably won’t have all of the available technology, choosing instead to specialize in one or two areas.  But, there is a tendency toward collaboration among casting suppliers providing rapid solutions, as well as jobbing out to one another.

The Benefit for Buyers

For original equipment manufacturers (OEMs) buying castings, rapid manufacturing offers a variety of benefits. Design and engineering ideas that were not always possible can be realized. The precision of additive methods in particular enables feats of draft and wall thickness that have not been possible in the past.

“We see the importance of these design issues in aeronautics and space components,” Murray said. “People wonder why those parts cost so much. Well, it’s because of the engineering requirements. But now things that make jet engines more efficient don’t have to be machined. We can make raw castings that are usable without all the machining, and we can make shapes and contours that cannot be machined into a casting.”

For metalcasters running automated lines that are cost-prohibitive for prototyping, rapid methods can be used to make molds that fit into the equipment.

“I can have it simulate any molding process,” Murray said. “If they want to run 10 samples, I can print something off that fits into a standard blank on that line. It’s how the foundry is going to be able to compete and add to the bottom line.”

Rapid methods also are being used to make production pattern equipment for longer runs. While prototyping doesn’t always have stringent demands in early design stages, often the parts are made as close as possible to the versions that will be cast in full production.

“If they want to test a part that’s going to be design intense, then we want to add the draft and the fillets, the gating, to make sure everything matches production intent,” Gustafson said. “Many of my customers, large OEMs, will scan the casting and then overlay it to the model. If we’ve made a suggestion that will make the part less expensive or easier to make, they’ll change the model to match, or we need to change the part to match the drawing. Because that’s what they’re running simulations from.”

Prucha recommends an integrated approach to rapid manufacturing using computer-based technology. “[It] not only reduces lead time but improves the design,” he said. “This should be managed via a disciplined program management system. Technologies that assist in creating samples quickly will help maximize the evaluation time and decisions made during this critical phase.”

Rapid manufacturing enables metalcasters to produce components for physical testing that match the castings to be created in full production using other methods. It’s a game changer in the automotive market’s ever increasing competition to produce lightweight, high performance components.

“Ford has three sand printing machines, and a lot of their newer technology was proved out using this technology,” said Murray. Other auto manufacturers, such as Chrysler, also are making the most of additive manufacturing. According to Harold Sears, technical expert, Rapid Manufacturing Technologies, Ford Motor Co., Dearborn, Mich., 3D sand printing has enabled his team to take a 16-week part development lead time down to a couple days.