High precision, automated medical manufacturing

Features - Cover Story: Machining

Micropulse’s investment in the right equipment delivers orthopedic implants that demand tight part tolerances.

Micropulse acquired its first linear-motor Mikron mill for machining titanium and has since added six more. Among them are Mikron HSM 400U LPs with 42,000rpm spindles and precise geometric positioning capabilities.

By incorporating manufacturing technology from GF Machining Solutions, medical instruments and implant manufacturer Micropulse Inc. positions itself with competitive pricing, delivery, and efficiency – effectively cutting part processing costs by 30%.

Operating out of a 160,000ft² facility, Micropulse manufactures orthopedic surgical instruments, implants, and case-and-tray, and provides sterile packaging and product logistic services. Throughout the years, medical industry requirements and regulations have continued to dictate tighter part tolerances, demands Micropulse can meet with high-precision machine tools. According to founder, owner, and CEO Brian Emerick, automation, earned trust, and integrity have allowed the shop to provide quality parts, delivered quickly, at competitive prices.

Any delivered product must be traceable to the raw material provider with each manufacturing process tracked by who did what, with which tools and software.

Job lot sizes typically run between 20 and 100 pieces.

However, the real part tolerance challenge involves the exact geometric positioning of one part feature in relation to the next. Since parts for the human body are never perfectly straight or square in shape, the shop relies on modular workholding systems to clamp a part once and completely machine it. Once such parts are removed, re-clamping them in the exact same positions is nearly impossible.

Die-sinker-type EDMs at the shop encompass an AgieCharmilles FORM 200 and a RoboForm 350 in a cell with a Mikron HSM 300 high-precision, high-speed milling machine.

Micropulse equipment

Micropulse’s high-precision electrical discharge machines (EDMs) and milling machines, as well as its automation, have come from GF Machining Solutions.

Die-sinker-type EDMs at the shop encompass an AgieCharmilles FORM 200 and a RoboForm 350 in a cell with a Mikron HSM 300 high-precision, high-speed milling machine and System 3R WorkMaster robot – the shop’s first foray into automation. Other EDMs at Micropulse include Robofil 240 CC and CUT 200 Sp wire-type EDMs.

The shop continues to delve further into high-precision, high-speed milling with additional Mikron machines, mostly for its EDM graphite electrode production. A few years ago, Micropulse acquired its first linear-motor Mikron mill for machining titanium and has since added six more. Among them are Mikron HSM 400U LPs with 42,000rpm spindles and precise geometric positioning capabilities as well as a pair of Mikron MILL S 400 U machines teamed with a 120-position tool capacity System 3R WorkPartner 1+ robot.

The 5-axis HSM 400U LPs deliver speeds up to 250rpm on their table rotational axes and up to 150rpm on their swivel axes, with B-axis swivel ranges of 220°. The machines use liquid-cooled, linear direct-drive motors with central oil lubrication to reduce friction-induced wear for long-term accuracy and a 1.7g acceleration rate.

The machines’ monobloc bridge designs ensure precision with high levels of rigidity. Polymer granite construction dampens vibration and boosts thermal stability.

Micropulse’s 42,000rpm 5-axis MILL S 400 U machines’ linear axes feature rapid traverse rates as high as 3,937ipm. The machines achieve speeds up to 160rpm in B-axis and 250rpm in C-axis. For unattended operations, the machines include pallet changers with 18 pallets.

“Early on, we realized that we needed high-speed milling capabilities,” says Larry Sutton, general manager at Micropulse Inc. “And we knew that marrying that capability with automation would benefit us greatly.”

Micropulse produces implantable components using titanium, stainless steels, cobalt chrome, PEEK, and other materials for a wide variety of orthopedic products.

Managing automation

In addition to complete process stability, using five automation systems to serve seven machines allows the shop to boost its output. For instance, six employees keep seven machines running across three shifts and throughout weekends in the Implant Division. That division averages about 150 hours of spindle time per week for each machine.

“We aren’t making thousands and thousands of the same parts,” Sutton explains. “Most of our jobs are small batches that entail a lot of changeovers, which can really make cost reduction a challenge.”

Part families typically run in the automated cells in batches of 50 or so, with each operation running about a day-and-a-half before moving on to the next job. For setups, the shop makes some of its own fixtures and uses System 3R modular pallets.

According to Ryan Sims, implant manager at Micropulse, fixtures are the shop’s biggest expense. For greater efficiency, a single-fixture system and automation can provide the necessary speed and flexibility to accommodate part families with minor differences from one group to the next.

“Automation has basically removed setup time from our part-processing equation,” Sims says. “With a conventional machining center, our setups would take four to six hours. Plus, with Mikron machines, we can automatically laser touch off all the tools for a job in less than five minutes.”

Each high-speed Mikron holds up to 66 tools, and because the shop’s jobs typically require 20 or fewer tools, operators will load redundant tooling to keep the machines running when tools wear. The Mikrons also have thermal compensation, so if temperatures vary a few degrees, the machines will automatically adjust to maintain accuracy.

Micropulse continues to delve further into high-precision, implementing technology such as the CUT 300 Sp wire-type EDM.

Longer tool life

According to Sims, the Mikron Machines’ high spindle speeds and lack of machine vibration help increase tool life, typically 2x to 3x longer.

“For those parts moved over to the Mikrons, we’ve experienced not only longer tool life, but also cycle time reductions, often greater than 25% depending on the part, and reductions in the need for secondary manual finishing operations by 50% in most instances,” Sims says. “Those parts with very small features that require extremely tiny tooling – as small as 0.011" in diameter – have yielded the greatest cycle time reductions. In one instance that amount was more than 60%. Our slower, conventional 12,000rpm machines are unable to feed or move accurately enough for these cutting tools that require precise movement along with high speeds and feeds.”

Such tools are also so small that any type of physical/conventional tool detection system would break them. The shop checks such tools with laser-based systems on its Mikrons that measure diameter and length, and do so within three seconds, according to Sims.

“We are confident that we can continue to compete diligently with offshore competition because of how we can optimize our output,” Emerick adds. “GF Machining Solutions is a big part of that capability because it is a true technology partner and a supplier that wants to keep us successful – not just sell us a machine tool.”

GF Machining Solutions

Micropulse Inc.