Improved production of cardiac monitoring component

With more than 15,000 products, Boston Scientific is a market leader in pacemakers, defibrillators, monitoring equipment, spinal & brain stimulation, stents, catheters, and ablation devices. Larry Hennig, manufacturing engineering specialist at the company’s Arden Hills, Minnesota facility, reports that on one cardiac monitoring battery component, “We had an application running year-round on multiple mills, rectangular in shape, consisting of multiple milling operations per part, requiring an operator per mill at all times. Both mill operations consist of multi-part fixtures as the process involved running mill OP-1, light hand deburring, and prepping the parts for mill OP-2 fixture and process, following the manual deburring step. The overall process was running around seven minutes per part.”

Hennig and his team members determined the Swiss process was more beneficial, as they could eliminate manual deburring, reduce process time to around three minutes, and one operator could run multiple Swiss machines. This enabled the process to run unattended while CNC auto-segregating particular parts for in-process dimensional inspections. The process proved to be more stable by eliminating manual deburring, while resulting in a better surface finish with nearly triple the tool life.

This new process had a combined six-person headcount reduction, as the Swiss manufacturing process is capable of running for more than 12 hours unattended while holding the targeted 0.0002" profile tolerance. Additionally, there was a significant improvement in material savings, according to Hennig. “We were using 0.300" of stock per part for the milling process, while the new process only requires 0.100" of stock material per part.”

The machines were provided by the local Minneapolis Citizen distributor, Productivity Inc. through a partnership with Andy Walser and their tooling representative Terri Farrell. Farrell sought input from Preben Hansen, president of Platinum Tooling Technologies, who introduced a Heimatec speed increaser specially designed for the Citizen machines. This enabled the team to quadruple the tool’s rotations per minute.

As Hennig explains, “While this component isn’t a round part, it’s small in size, and requires small tooling. We weren’t getting enough rpm to match the tool diameter and necessary sfm, causing long process times and reduced tool life due to the tool not meeting the necessary rpm requirements. I have worked with many types of electric spindles and many brands of speeders. With the electric spindles, we had some success on light drilling and small-diameter high-speed milling, but the obstacles we faced involved load on the tool that would cause the electric spindle rpm to fluctuate, leaving tool marks across the material or even alarming-out the electric spindle when load was applied.” As a result, Hennig reports the company needed to rebuild the bearings and seals on their high-speed electric spindles annually, additionally rebuilding the previous manufacturers’ gear-driven speeder heads multiple times during the year while running high-production volumes of parts.

Hansen proposed this new idea to Hennig. As a result, several 1:4 speeder heads and tooling attachments were introduced to provide additional live tool positions and rpm. According to Hennig, “We achieved a superior surface finish when drilling, reaming, profile, and face milling, which improved our tool life and reduced cycle time by using these speeders, compared to the 1:3, 1:2, and especially the 1:1 standard tool provided by the OEM.” Hennig reports the Heimatec speeders provided by Hansen have been in operation for more than two years and haven’t required a rebuild. He says, “They still feel like the day I brought them into the process.”

Hansen notes, “We helped Larry (Hennig) convert the process for production of these components by enabling a single operator, a more stable machining operation, improved cycle times with the higher rpm and proper feed, plus the big advantage, an optimum surface finish, which is so critical on these parts. The deburring issue is simply no longer an issue,” he concludes.

Hennig expands on his experience, adding, “We developed some amazing new macro features with this latest project, such as rotation macro-offsets for alignment from main to sub, developing safety crash macros to help prevent accidents into tool holders due to limited clearance between sub collet and face of part, as we are only chucking on 0.006" of the part during part pickoff/transfer and have limited clearance on the sub side. This prevents crashes into the cutoff or sub-spindle tooling if set up or offset incorrectly. Together with our team’s tribal knowledge, we designed custom tools that spot, drill, ream, and chamfer all with a single tool, keeping the chamfers concentric, while custom deburring tools provide a burr-free product. These were all conditions we struggled with on most of the mills with their need for manual deburring and several tools intersecting the same feature.”

Hennig continues, “We’ve learned over the years that tooling specs rarely work in Swiss applications due to the lack of workholding compared to mills or even conventional lathes. For example, when programming a high-volume product, I usually start at 50% of the tooling manufacturer’s recommendations and then run 15-to-25 test cuts at various speeds and feeds to find the optimal conditions.” He further notes, when milling on Swiss applications, “I’ve learned that performing climb milling for rough cuts and using a conventional mill spring or finish pass aids tremendously with knocking off any burrs, providing an amazing finish on all surfaces with an extended tool life.”

Hennig says with any medical or implantable device, Boston Scientific is tasked with much higher standards compared to most manufacturing facilities, in terms of surface finish, dimensional requirements, and creating no burrs. Reiterating this, Hennig states, “At Boston Scientific, we hold every single part to the highest standards cosmetically, dimensionally, and functionally. Our number one priority is quality and providing the best patient-impacting components, regardless of expense. That’s one thing I really value about this company.”

Terri Farrell from Productivity adds, “It was a no-brainer to get Platinum Tooling involved in this project. Preben (Hansen), his team, and the products they offer to the manufacturing world are all top notch. Having the opportunity to work with Boston Scientific and the caliber of machinists and engineers such as Larry (Hennig) has been one of the most rewarding experiences in my career. This team isn’t afraid to approach a project from a completely different angle and try new things. That’s how you stay on the leading edge.”

Hennig concludes, “I highly recommend Platinum Tooling products. They offer a great product, Preben (Hansen) offers fantastic support and communication, and they are open to new ideas and challenges to help support customers’ needs while maintaining great price points. I’d also offer thanks for the support from Andy (Walser) and Terri (Farrell) from Productivity and all of their team members who helped support this project.”

Boston Scientific
www.bostonscientific.com

Platinum Tooling,
www.platinumtooling.com
IMTS 2024 booth #433245

Productivity Inc.
www.productivity.com