Additive Manufacturing

Gaining clients with the fine print

By Nick Wright

Above: Linear uses an array of EOS metal 3-D printers, including the M 270s and M 280s, at its three facilities in Michigan.

By adopting additive manufacturing early, Linear grows business around the service of production metal printing

February 2015 - As additive manufacturing (AM) with plastic has established itself as a viable production process, metal 3-D printing has also proven ideal for high-mix, low-volume customized manufacturing or prototyping. It’s safe to say, however, that AM with metal has come of age for any manufacturing scale, from prototype to mass production. Regardless of your capacity, if you’ve invested in a metal 3-D printer, you might find there’s no shortage of work to go around.

It’s a similar situation at Linear Mold & Engineering Inc., Livonia, Michigan. John Tenbusch founded the company in 2003 to address rapid tooling needs of automotive manufacturers, despite the gradually declining economic conditions of the auto industry at the time, and has managed successfully since.

Linear’s services go beyond injection, compression and vacuum form molds, which, as its name suggests, is the primary business. The company has full fabrication, engineering, machining and finishing departments to take designs from art to part. The workhorses behind Linear’s operations are its 3-D printing systems. Currently, Linear operates 11 AM systems, including one it runs at a customer’s facility, with three more on order for this year. Among these machines are four EOSINT M 270s and four EOSINT M 280s manufactured by EOS, which has U.S. offices in Novi, Michigan. The EOS machines are direct metal laser-sintering (DMLS) systems, which use the fiber laser sintering method of melting powdered metal into a 3-D component directly from a CAD design.

In addition to running the M 280s for prototype and production metal parts for the automotive, aerospace, and oil and gas markets, Linear will train operators unfamiliar with the technology at would-be competing companies that are making parts like conformal-cooled inserts.

“The competition doesn’t really scare us,” Tenbusch says. Linear tracks machine usage weekly, and lately the M 280s have been running between about 55 and 60 percent of the time. But, as Linear moves into production part runs, the company expects machine utilization to improve. By mid-2015, Tenbusch expects metal 3-D printing to account for 50 percent of Linear’s total business, whereas two years ago, it was around 10 percent. As an early adopter of EOS’ DMLS technology, Linear is a testament to how a metalworking operation can not only leverage 3-D printing as another tool in the shop, but market it as a primary process.


Blueprint for growth

During the earlier days of Linear, Tenbusch says they experimented with other 3-D printing methods like stereolithography (SLA) and selective laser sintering (SLS). But it was an acquaintance of Tenbusch, who coincidentally worked for EOS, who suggested Linear try out its technology. He produced a few sample parts, and Tenbusch was sold. As a start-up company in the 2003, Linear figured it could market the service to potential customers in the auto industry such as tier 1 suppliers.

“The first machine we bought was just to support Linear’s upstart operation and to make hand-loaded tool inserts,” he says. “Those components would have been machined and EDM burned, but we instead printed them from a CAD file, put them in the injection mold, and we were off making parts.”

Linear 3-D prints a range of hard materials, including Inconels for aviation and oil and gas, as well as cobalt chrome for aviation customers. It also prints aluminum, titanium, and Hastelloy X. For injection mold tool inserts, it can print maraging steel (MS1) tool steel. The inserts are usually for tooling in an injection mold, die cast application or hot stamping. The conformal-cooling applications are currently about 5 percent of our usage of this technology, but we see it going 10 times that in 2015 easily,” Tenbusch says. 

Linear declined to specify what parts it’s making for automotive, aviation and energy industries, but as of the beginning of the year, half of its capacity is devoted to printing production parts. It claims several Fortune 500 companies as repeat clients for mold inserts and finished parts. The four M 280s, the newer of its EOS machines, use a 200 W fiber laser and can make parts with a volume of 9.85 in. by 9.85 in. by 12.8 in., about the size of a toaster oven.

“A number of our big customers, after six months of test-running our parts, are coming back to us saying, ‘This stuff works.’ We are going to use this on a number of tooling applications, both existing tools in process now and new projects coming up. We feel the demand will skyrocket on the coolant lines.”

When it comes to finishing a mold insert, a mold shop typically works to tolerances within 0.001 in. For prototype applications, parts don’t need much post-processing out of the machine. For finishing production parts, Linear will use wire EDM, sinker EDM and CNC machining.

Combined with fab

EOS, which was founded in 1989 in Germany, has contributed to the development of 3-D printing technology from day one. Its DMLS technology didn’t come on the market until the mid-1990s.

Andy Snow, senior vice president for EOS North America, says Linear established its position as a firm that can address multiple mold building applications with 3-D printing, long before many others. 

“Tenbusch had this vision this was going to be big time one day. As an early adopter, he’s benefited dramatically by being a way paver into this industry,” says Snow.


Now, Linear has 57,000 sq. ft. of manufacturing space and 110 employees—29 of whom are dedicated to the metal printing operations. While the AM side is important, the fabrication operations can’t be overlooked. For example, fabricators at Linear recently built a fixture for an automotive customer. It’s made from 11 separate pieces, all printed from MS1 material. The customer intended to mimic the same material used in a production application for which Linear CNC cut a fixture and welded the entire assembly.

“We have some aerospace applications where we’ll actually print the parts and fixture, weld and post process machine away all those weld surfaces,” Tenbusch says. “It’s a combination of printed parts and conventional welding methods.”

Growing parts, pains

With any new technology, there are growing pains. In terms of AM with metal, one issue for Linear was figuring out how to best configure support structures—the small braces integrated in designs to keep primary parts upright during printing. Another issue is cost effectiveness, redesigning customer parts to optimize the geometry and “grow” or print patterns on the build plate, the platform upon which parts are printed.

“We have a catalog of parts that we’ve tracked how they are grown,” says Tenbusch, so operators don’t have to work from scratch on new part orders.

In terms of post processing, removing the support structures is essentially the opposite of the high-tech process that produced them. “It’s like removing them with a hammer and chisel sometimes,” he says. “We always need to figure out how much support is enough to build good parts, but not too much so we can do it efficiently.”

Determining variables, like support structures, sets Linear apart as a service provider. Its operators are metalworking people—many of them former automotive industry employees—who know how parts warp and twist. “Having our in-house experience working with metals already, and then getting into 3-D printing, was a natural fit,” he says.

The traditional way of thinking when it comes to part design entails subtractive manufacturing with a multi-axis machine. Tenbusch says AM allows the industry to step outside that traditional manufacturing box. Linear can be more creative in the design process and combine components that might be made individually by stamping or welding and engineering them into one printed part. It seems like a major conceptual change for any manufacturer, but as Linear has discovered, dialing in production with AM has proven worthwhile. By teaching operators from other companies how to use EOS systems, Linear ensures there’s a resource for overflow work, too.

“There’s more than enough work in the marketplace to go around,” says Snow at EOS. “The supply that’s currently in the industry can’t meet the demand industry needs now.” FFJ



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