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Medical Parts Maker Ups Efficiency, Capacity of EDM Machining

Jim Lorincz
By Jim Lorincz Contributing Editor, SME Media

With each new contract and change order to increase part volume and improve delivery, Johnson Matthey Medical Components expanded capacity and capabilities in the same way—by purchasing more equipment. The San Diego, CA-based company would invest in another EDM to meet growing demand for orthopedic, endoscopic, cardiology and neurological medical devices, which is at an all-time high. The tactic was effective, but costly.

Working with SST and Makino, Johnson Matthey developed a double-stack design for untended fine-hole drilling of 174 parts using a single fixture.

“Because of the workload, or the suddenness of new orders, it was just easier to buy a new machine and get it on the floor,” said Michael Grassie, production manager.

No more. About two years ago, after a change in senior leadership, Johnson Matthey began to rethink its approach.

Johnson Matthey’s 41,000 ft2 (3809 m2) shop is outfitted with Swiss screw machines for primary machining of components used in catheters, surgical instruments and other medical devices. The parts require exceptionally precise, burr-free shapes made from sheet, tube or wire. Some parts are smaller than 1 mm in length. Holes are as small as 0.003″ (0.08 mm) in diameter with intersecting or crosshole features. To ensure repeatability of the smallest parts with complex shapes, fine holes or other features, the company relies on advanced wire, sinker, and fine-hole drilling EDMs.

Johnson Matthey micro-machines parts out of platinum and platinum-iridium alloys for orthopedic, endoscopic, cardiology and neurological applications. Since the company had 23 wire, sinker, and fine-hole drilling machines already in the shop, new operations manager Oss Bozier wanted to know whether the company was fully utilizing the existing equipment.

An internal review and consultation with engineers from Makino Inc. (Mason, OH) and its local supplier, SST, answered his question: No. That realization led Johnson Matthey to relearn how to use its EDMs and revise its manufacturing processes for greater efficiency and unattended operation. For example, automatic tool changers (ATCs) that are standard equipment on the fine-hole drilling machines had never been used. Under Bozier, the company has committed to a multi-year program of automation to become more efficient while also increasing capacity.

Precise auto-threading capability allows the Makino U32j wire EDM to provide reliable cutting of 0.002” (0.05-mm) radii in the interior of parts, and to impart surface finishes down to 0.07 μm Ra.

“We decided to take a step back and look at how we were manufacturing things,” Grassie said. “We’ve operated Makino machines for many years and have had a long relationship with their supplier, SST, but frankly we had not taken full advantage of their support and services until recently by bringing in their technical experts to make sure we are utilizing the full capabilities of our machines.”

Grassie and others at Johnson Matthey initially asked about how Makino’s engineering services could help the company integrate robotic loaders with existing EDMs to create cells that would run unattended overnight and on weekends. The company currently operates two shifts, six days a week.

“Those conversations led to the realization that there were untapped efficiencies and capabilities, such as the
ability to set up multiple electrodes in the ATCs at the same time,” said Grassie.

The first step involved incorporating ATCs into machining routines on eight of the fine-hole EDMs. Fixturing designs were expanded and, in early May 2017, Johnson Matthey began double-stacking or simultaneously running fixtures that each held 174 parts. “Historically, we limited ourselves to the number of parts that could be machined using a single electrode. Now we use the ATCs, which expands what we can set up and allows us to increase machine utilization by increasing the number of parts per setup,” said Grassie.

The sinker EDM machine’s W-axis middle guide system.

Among its first targets were Makino EDAF21 fine-hole drilling machines capable of automatic tool changing of pipe electrodes as small as 0.004″ (0.10 mm) in diameter. Supported by a W-axis middle guide system, the machines can support small-diameter electrodes and prevent vibration or bending during machining.

“That was the most obvious first step toward automation,” said Wes Colony, an SST sales engineer. “Because the ATCs that are standard on the EDAF2 machines had been dormant, they needed to be dialed in. We had a service engineer make the adjustments so the company could get operational with reliable ATC function using small diameter electrodes.”

Working collaboratively, Makino/SST and Johnson Matthey identified ways to extend unattended machining time and helped move Johnson Matthey closer to its efficiency goals. Instead of having operators manually change electrodes on fine-hole drilling machines every four hours, the ATCs automatically change electrodes, enabling the machines to run unattended for 10 hours. As a result, operators can focus on other value-added tasks.

A second significant process revision came after evaluating and changing how Johnson Matthey fixtures the tiny parts it machines. The company historically set up and ran one fixture at a time on its EDMs. One component requires drilling one hole 0.003″ (0.08 mm) in diameter into one side. An operator manually loaded 174 of the parts onto a fixture and then ran the job while manually loading a second fixture. Machinist Jason Ruvivar helped design a new fixture and programming to run two fixtures at the same time. Johnson Matthey began this double-stacking approach in early May 2017. Combined with the use of ATCs, the new processes immediately increased throughput.

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