Lunar Tool & Mold Embraces MakinoS56 Graphite Milling Capability

Walk into any die/mold shop and you’ll likely find dedicated machines for wet and dry hardmilling and graphite milling, three common operations. Die/mold shops often run dedicated hardmilling and EDM machines for these operations because each has special requirements. For example mold working components, machining aluminum, pockets, bored holes, and waterholes requires a coolant delivery and recovery system; otherwise, operators can expect gummy cutting and drastically shortened tool life.

Similarly, dry hardmilling core and cavities requires certain types of coatings and specialized tooling, and machining graphite—cutting electrodes for Ram EDM core and cavity details that can’t be hardmilled because of their size or reach—requires a vacuum system to extract the graphite dust.

Mounting pressure to minimize costs while improving machine and spindle utilization has forced many shops to consider replacing their dedicated machines with multi-purpose, or all-in-one, machines. All-in-one machines such as Makino’s S56 vertical machining center with graphite milling capability have wet and dry hardmilling capabilities but can also be configured for milling graphite. Using these machines, die/mold shops can lower costs by reducing downtime, training and maintenance spend. In addition, shops can decrease lead-times and improve machine and spindle usage.

Fritz Hoffmann, president of North Royalton, Ohio-based Lunar Tool & Mold, has firsthand experience with an all-in-one machine with graphite milling capabilities. He installed a Makino S56 vertical machining center in April 2007 to produce aerospace tooling from D2 hardened steel.

Lunar Tool & Mold has been in business since 1965. The company specializes in investment casting tooling to manufacture engine blades. Lunar manufactures two types of investment casting tooling. One type requires hardened D-2 the other steel or aluminum.

“Our components require a wide variety of machining operations, and we were forced with a decision to purchase multiple commodity machines or one high-end Makino that could handle wet, dry and graphite applications,” says Hoffmann.

Investment Casting Requires Specialized Machining Centers

Lunar Tool & Die uses aluminum P20 and D2 to manufacture tooling. The process involves injecting wax into a tool, coating it with ceramic and then casting it with the appropriate metal, usually one that resists high wear and heat. The excess ceramic is then chipped away once the product cools, leaving the engine blade.

Hollow blades require several additional steps. To create a hollow blade for flight applications, Lunar builds a tool from hardened D2, which is injected with ceramic and fired to harden it for machining. After cleaning, the core is injected into a secondary wax tool. This secondary tool is coated with ceramic and chaplets are inserted to prevent the ceramic core from moving when the wax is melted out. With the interior ceramic part suspended in the outer ceramic coat, hot metal is injected. Once the metal is hardened, the ceramic is chipped away from the outside by either an acid bath or by blasting the ceramic out of the center.

“In order to complete this type of machining, you need equipment that is capable of cutting and milling graphite, because the hardened D2 tool that needs to be produced has intricate geometries,” says Hoffmann. “It will require burning about 80 percent of the time and can only be hardmilled about 20 percent of the time. So we need a graphite milling machine that can hardmill for that 20 percent, cut graphite for the Ram EDM and cut aluminum.”

Graphite Milling Machine Capability

Hoffmann approached Makino because he liked the hardmilling capabilities of the S56. He was concerned, however, that the S56 wouldn’t support Lunar’s graphite milling needs and assumed he’d have to purchase an additional machine to handle the graphite work.

The S56 utilizes a 40-taper, 20,000-rpm spindle with the stiffness and rigidity required for hard-cutting applications and the speed necessary to provide high surface quality for demanding die and mold applications.

Makino configured an S56 with a graphite package, enabling the S56 to be a graphite milling machine. It can circulate coolant for aluminum applications and rough-out cavity blocks of D2. The graphite milling machine package included a dust collector that has a 5-horsepower motor, rated at 1,800 CFM, a 10-gallon hopper and a differential pressure gauge to monitor filter replacement. The graphite milling package also included a Chipblaster coolant filtration unit, which is capable of 10-micron filtration.

“For us, the graphite milling machine package was the way to go,” explains Hoffmann. “The vacuum system exceeded our expectations with incredibly thorough carbon removal. In fact, during the graphite package testing, the initial vacuum settings were so strong, we could see the pull on the operator doors.”

Reduced Lead-Times by 50 Percent

The Makino S56 enables Lunar to run wet, dry and graphite operations back to back. Its hardmilling capabilities provide accurate cutting of 60 HRc materials with up to a half-thousandth accuracy, as checked by a 10x comparator. Without the need for EDM machining in their hardened materials, Lunar is able to compete with shorter lead-times and reduced costs.

“The S56 was more cost-effective, since we didn’t have to buy two machines,” says Hoffmann. “The all-in-one machine also allows us to avoid a great deal of machine downtime, resulting from step-by- step processing in multi-machine operations. We have the S56 cranking out parts as much as possible and from a business perspective, a machine running frequently makes more money.

“Our processing capabilities have never been faster. The switch from wet to dry or graphite milling can be completed in 30 minutes, while transitioning from graphite to wet or dry can be done in as little as 10 minutes. Even when it’s down for transitioning, the S56 is still quicker for processing than having to re-fixture parts for another machine.”

Hoffmann typically runs graphite electrodes in the morning and rough cavity work unattended in the evening. Running the machine unattended at night has reduced Lunar’s lead-time by 50 percent compared to EDM.

“Our lead-times used to be between 10 and 31 days,” explains Hoffmann. “Now, we’ve cut some of those times down to five to 15 days.”

In addition to reducing costs and lead-times, Hoffmann also credits the machine with increasing part quality. The S56’s Blum laser measurement system has helped minimize cutter wear, which can impact the overall quality.

“The laser detects cutter wear when machining multiple electrodes, helping to prevent errors. You want to ensure the cutter is sharp to avoid mistakes down the road,” says Hofffman. “By measuring tool lengths in between electrodes, the laser is able to determine when the machine needs a new cutter loaded. We load a few extra cutters in the machines and can run four to five electrodes, a 30- to 40-hour process, over the weekend unattended, without worrying that a cutter might snap off during an intricate geometry. In another instance, we cut electrodes unattended over a weekend.”

Hoffmann also explains the Makino is more reliable than other machines he’s used, and as a result, he saves in maintenance costs.

“The operating environment of the S56 is easy to learn and use, so we’ve also saved on training time and costs,” he says. “It also has superior coolant filtering. Some of our other machines need frequent coolant changes to remove carbon particles. We haven’t changed the coolant on the S56 since it was installed.”

Looking to the Future

While the S56 cut back on the demand for EDM-ing of many parts, EDM was still a necessity for a number of Lunar’s applications. The company came back to Makino in early 2008, looking for a wire EDM to replace one of its older, less-efficient machines.

“Our experience with the S56 and the excellent customer service we received from Makino made purchasing a wire EDM an easy choice,” explains Hoffman. “As the number of orders and component complexity grew, we knew that we could trust Makino to provide a machine that could meet higher demands. We bought an SP43 wire EDM without hesitation, and since then, we’ve gained even more work. We’ve increased our EDM utilization from 20 percent to 60 percent.”

Lunar continues to seek new ways to increase the shop’s efficiency and currently forecasts a potential expansion in its milling operations. The S56 has proven that modern high-performance milling machines are able to perform above previous expectations and will continue to improve as customer demands increase and parts become more complex.

Shops that use multiple machines for wet, dry and graphite milling often have idle or overloaded machines, since they have to pick and choose what machines will perform which functions. This situation leads to increased costs and longer lead-times. Shops that use an all-in-one machine for these operations have lower overall expenditures related to capital investment, more flexibility to cut lead-times, improve equipment utilization and can machine more components unattended.

“Technology has provided us with a means to exceed our customers’ expectations,” says Hoffmann. “I feel you have to always be on the lookout for the latest and greatest technology to provide clients with products as quickly, accurately and effectively as possible. If you can do this, you will be head and shoulders above your competition.”