Case Studies

And Now for Something Completely Different: Laser-Sintering
DMLS equipment from EOS helps Linear Mold & Engineering save 15 to 30 percent on manufacturing mold inserts and tooling

View of DMLS in action. Laser-sintering is an additive manufacturing method that builds up parts one thin layer at a time.

Tooling and moldmaking is a fiercely competitive business. The goal of a good shop is to be, not just a supplier, but the supplier in customers' minds—the one they value for expertise, outstanding delivery times, and range of manufacturing options.

"We're always keeping our eye out for new equipment or a process that's a differentiator—something that makes us stand out from other shops," says John Tenbusch, president of Linear Mold & Engineering (Livonia, Mich.). As a result, since it first opened in 2003, Linear has acquired a wide variety of prototyping, tooling, and manufacturing capabilities—including six CNC machines (two of them high-speed) and five injection molding machines from 110 tons up to 1,000 tons. The company produces molds that can turn out anything from a few samples to a production run of 100,000 or more. Linear has used their equipment to build a moldmaking and prototyping business that spans a broad range of industries, including automotive, aerospace, military, home goods products and medical.

In November of 2005, Linear added a capability that set it apart from nearly every machine or mold shop in the country. The company became one of the first North American purchasers of direct metal laser-sintering (DMLS) equipment from EOS of North America (Novi, MI). How Linear evaluated the cost-effectiveness of the DMLS machine, how its use evolved and grew, and how it paid for itself and reduced production costs and times, is a story well worth reading for expense-conscious suppliers of tooling, molding, and prototyping services.

Searching for savings
"Shops like Linear require two types of precision: accurate molded parts and accurate costing," Tenbusch says. "We're always working to increase quality and lower costs." In prototyping, all the customer wants is the plastic parts. One of the inevitable costs of making those parts is the moldmaking itself—an expense that falls directly on Linear, which needs to be as cost- and delivery- competitive as possible.

For many smaller prototype runs, Linear creates molds for parts with undercut features using hand-loaded mold inserts, which are removed from parts after each shot at the molding press. Manufacturing these mold inserts is time- and labor-intensive, but for Linear at least, there didn't seem to be a more cost-effective alternative. "We weighed a number of processes, including cast composite inserts and SLA parts with ceramic materials in the resin," Tenbusch says, "but we couldn't find the savings or the quality we were looking for. Basically, we were out of luck."

At this point, Linear's luck turned.

Tenbusch's next-door-neighbor, a self-employed contract mold designer, took a full-time job at EOS of North America, who sent him to their parent company's headquarters in Germany for training. "The moment he returned home," Tenbusch remembers, "he came over and said, 'John, you really need to take a look at what these guys do. It could be perfect for your applications."

Shown is an EOSINT M 270 that Linear Mold and Engineering uses for direct metal laser-sintering (DMLS) of tools and of mold inserts.

When John Tenbusch took a look at an EOSINT M 270 DMLS machine, it seemed his neighbor was right. "We were already thinking of adding electrical discharge machining to our offerings," he says, "and maybe a small five-axis CNC machine. Having DMLS equipment would be like having the CNC and the EDM all in one." Best of all, hardly anyone in North America had laser-sintering capabilities for metals. "It would be an instant differentiator," he says, adding, "The curiosity factor with our customers would be huge."

And so Linear Mold immediately purchased the laser-sintering equipment—

Testing and timing
"—Well, not exactly," Tenbusch remembers. "You don't buy new shop equipment—especially something this unusual—without testing and benchmarking."

Tenbusch requested that EOS run some samples of mold inserts that he would usually cut and then have burned with EDM—the sort of work that would normally require multiple set-ups.

DMLS, however, could create such samples in a single set-up, because it is an additive manufacturing process. It starts with a CAD file that defines each layer of a cross-sectioned model. Twenty to 40 µm thin layers of metal powder are deposited onto a build platform and laser-sintered by a focused laser beam. The platform is then lowered and the process repeated layer-by-layer until a three-dimensional metal part is produced. DMLS can "grow" parts—even those with extremely complex geometries—in just a few hours, in a single set-up. "You don't need to burn a rib or a hole when you can grow it while you're manufacturing the part," Tenbusch says.

The test inserts worked perfectly and—in part because they didn't need to be sent to an outside shop for EDM—they were less expensive than inserts created by traditional processes. They also reduced production times for the mold.

Linear bought the laser-sintering machine.

Costing, and Costing, and Costing
At first, Linear used the DMLS equipment exclusively for hand-mold inserts. "Gradually, we realized that it had other potential uses," Tenbusch says. Slowly and steadily, the company explored creating core pins, slide assemblies, and tunnel, cashew, and sub- gates for epoxy composite tools, hybrid molds, aluminum tools, and even low-volume production molds. "We became our own best customer for laser-sintering," he notes.

Above is an aluminum mold with 17-4 stainless steel slides and slide heel. The slide heel block assembly (bronze color) is made from Direct Metal 20, a bronze-nickel alloy. The slides, slide heel, and block assemblies were all manufactured with direct metal laser-sintering in an EOS M 270. The mold is used to make a water fitting connector out of 15 percent glass-filled nylon.

There was some question about how to generate customer quotes for parts created with the new technology. Fortunately, because Linear had longstanding experience with traditional machining, it had compiled a library of benchmark figures for how long different projects would take and what they would cost using those methods. The library included production hours, hourly rates, and exact costs for any benching or third-party finishing. Linear used that data to provide customers with accurate quotes, including for DMLS projects. "We take extra time with quotes, so that they're as precise as possible," Tenbusch says.

Generating those quotes had an important side-effect: Linear had a basis for comparing the estimated times and costs of producing molds with traditional processes versus actual production data for laser-sintering.

Over the next two and a half years, Linear manufactured molds and inserts in Cobalt Chrome, GP1 (17-4) stainless steel, and DirectMetal-20 using DMLS—amassing production data for more than fifty commercial tool and mold projects across a wide variety of industries. Table 1 below gives examples of some typical moldmaking projects, comparing estimated production times for machining versus the actual time for DMLS:

The results demonstrate that, for many applications, DMLS significantly reduces production times and therefore costs. "Cost savings using DMLS range between 15 and 30 percent, depending on the complexity of the part," Tenbusch says. In other words, the more complex the part, the greater the cost reduction.

Above is an aluminum Master Unit Die (MUD) insert with 17-4 stainless steel slides. The cavity and core (bronze color) inserts are DirectMetal 20. Both the stainless and bronze inserts were made with EOS direct metal laser-sintering. The MUD is used for making visor clips (bottom, front)

It doesn't take long for savings this size to generate return on investment. "We achieved our ROI in thirty-six months," Tenbusch points out. "The savings in time and outside expenditure alone paid for it. The return on this equipment is much greater than we would have achieved buying a high-end 5-axis CNC and EDM equipment."

Ongoing innovation
Today, Linear will consider creating inserts with DMLS for practically any project. "Our biggest criterion for turning to laser-sintering is part complexity. If a molding project involves ribs or deep EDM burns, we'll try to grow the parts ourselves," Tenbusch says. "Essentially, we build molds and prototypes totally differently now, because we know we'll be able to make components that we would have had to buy or have custom made before DMLS.

"For instance, Linear recently created a metal prototype for a medical screw that had a coarse thread at the point (to bite into bone) and a fine thread at the head (to lock into a threaded metal plate). In addition, the plate threading was at a compound angle (to pull bone ends together). By growing the screw with threads in place, Linear was able to eliminate a secondary step involving custom work with a boring bar.

With these and other projects coming in-house, the company has been able to utilize the DMLS machine at 85 percent of capacity—including running unattended on weekends. It has a successful yield rate of more than ninety-five percent, and it has had virtually no downtime or difficult repairs—just regularly scheduled maintenance.

The costing work is evolving as well. Linear recently built a mold for a Chevy "Bow Tie" (the famous Chevy emblem). Linear proposed to grow both the cavity and the core inserts for a master unit die base, along with hand-loaded inserts for pulling two out-of-line-of-draw features. If it had not been laser-sintered, the cavity surface would have required an electrical discharge machining (EDM) finish to create a square geometric grain pattern that could not be CNC cut. Linear was awarded the job based on very competitive cost and delivery. Tenbusch says, "According to our customer, Linear was 32% less expensive than the nearest competitor, with a 1.5 week timing edge."

In addition to being cost-effective, the laser-sintering equipment has remained a strong business differentiator. Linear is building a base of customers who—having seen the equipment or run a previous job on it—request it as their first option. And it hasn't lost its ability to sway new customers, either. "There's still a 'wow' factor to this technology that was bigger than we thought it would be," Tenbusch says. "Sometimes, when potential customers are skeptical, we say, 'send us a part model and we'll make you one free,' just to convince them." He adds, "Typically, once they get the part, they go ahead and place orders."