True 5-axis is a healthy start in medical manufacturing

When Tim Schneider came on board at One Source Manufacturing Technology (OSM) in 2009, he had one mission – lead the Leander, Texas shop into the medical manufacturing sector. At the time, OSM worked almost exclusively in the semiconductor industry, but wanted to diversify for a steady, less-erratic flow of incoming work.

OSM had almost no experience in medical part manufacturing, so Schneider, as the new vice president, and his team had their work cut out for them. On the plus side, the core infrastructure of the shop was solid. It had already earned ISO 9001 certification, which proved a good start for eventually achieving its ISO 13485 certification as an established medical device supplier.

Throughout the years, medical work at OSM surged and quickly grew to more than 30% of overall manufacturing operations. However, Schneider realized that the shop’s existing machining capabilities limited its ability to produce the more complex medical components cost-effectively.

While OSM offered a solid base of fundamental machining technologies – such as turning and 3- and 4-axis milling – the medical parts it pursued involved a lot of complex 3D geometries and very tight tolerances. Simply put, the shop urgently needed 5-axis milling capabilities.

“As we got further into medical, we started seeing new designs from customers that really challenged how we had initially prepared for 5-axis machining,” Schneider explains. “Initially, we accomplished 5-axis machining using our 3-axis VMCs outfitted with 4th- and 5th-axis trunnion units. However, we quickly found out that such an approach hindered our part processing speed and cost-effectiveness.”
 

Eyeing 5-axis VMCs

The communication between the trunnion units and the VMCs on which they were mounted caused lags in positioning. Plus, the units’ additional mounted weight restricted how fast the machine tables could rapid traverse. The extra inertia involved with moving the added weight accelerated machine wear-and-tear and generated vibration, hurting part surface finishes. However, what really hindered operations was the amount of time and effort it took to achieve required levels of machining accuracy, especially for small parts.

“We needed speed, accuracy, and rigidity,” Schneider says, “and knew we could get it from a true, integrated 5-axis machine. So, we evaluated several machine tool builders – looking closely at how they designed their 5-axis machines – and the Mazak Vertical Center Universal (VCU) 400A 5X caught our eye. What really attracted us to the machine was the amount of capability it provided along with its exceptional construction. We were also quite surprised it had such a large table size within its small, space-saving footprint.”

OSM’s VCU 400A 5X VMC features an integrated tilt/rotary trunnion table with roller gear cam technology. The machine has as 40-taper 12,000rpm spindle and an automatic tool changer with 30-tool storage capacity. With an X-axis stroke of 19.880", the VCU 400A 5X handles parts up to 15.740" in diameter and 12.000" in height.

Along with its VCU 400A 5X, OSM has a Mazak Vertical Center Smart (VCS) 510C 3-axis vertical machining center with 40-taper 12,000rpm spindle, 30-tool storage capacity, and 41.340" X-axis travel. The shop plans to add another 5-axis Mazak, a VCU 500A 5X that accommodates workpieces as large as 19.680" in diameter and 12.000" high.

According to Schneider, for every job the shop has moved to the VCU 400A 5X, it has immediately reduced cost per part by at least 15% through shorter cycle times. In some instances, cycle time reductions were more than 25%. Data also indicate improved setup repeatability, further increasing processing accuracy.
 

Medical precision tolerances

OSM primarily manufacturers medical implants – knees, hips, and a variety of spinal components – along with some associated supportive instrumentation. The shop collaborates with customers to work through any manufacturability issues and will run prototype and test parts during developmental stages.

Parts range in size from 0.125" square up to 18.000" square. Typical tolerances are ±0.0050" and as tight as ±0.0005", and materials include stainless steels, titanium, cobalt chrome, and PEEK.

Significantly shorter cycle times and better machining accuracy from the VCU 400A 5X 5-axis technology proved especially beneficial for two medical parts at OSM. While in the process of getting its first Mazak, the shop was developing a new cervical plate design with a medical customer. The titanium part required lots of contour milling and specific surface finish requirements along with extremely tight 3D feature positioning tolerances. Screw holes – each at various complex angles – had to be maintained in relation to the part’s overall curved shape. Therefore, positioning accuracy of the machine was critical. The part also presented some tool clearance challenges.

“Right from the start, we struggled with the hole positioning and had issues with tool clearance when running preliminary parts on our existing bolt-on 5-axis equipment,” Schneider explains. “When we looked at the VCU, we thought there would still be clearance issues. However, Mazak conducted feasibility tests for us at its Southwest Technology Center in Houston, and basically proved out the process even before we made up our minds to actually purchase the machine. The results are what really convinced us.”

While the cervical plate parts are still in the prototype/test stage, OSM has converted titanium spinal cages for another customer to the VCU 400A 5X.

Similar to the cervical plates, the spinal cages involve very tight feature positioning tolerances. The parts also have some very small steps and pockets as well as other tiny details. The shop processes the parts in two operations. In the first, they machine between 80% and 90% of the part, which was basically all the critical features.

With average cycle times of about an hour, the VCU 400A 5X machines all the various sizes that make up the families of spinal cages 25% faster than did OSM’s bolt-on 5-axis equipment. The shop runs lot sizes in the hundreds.
 

Smooth and streamlined

Alex Virag, programmer and machinist at OSM, runs the VCU 400A 5X. He mentioned that what is “truly amazing” about the 5-axis Mazak is the machine’s kinematics.

“The machine knows where it is exactly in relation to the part position. So if part and/or setup needs to be off center, the machine knows where the part center is as well as its actual table center and will automatically adjust to the part’s center,” Virag says. “All we do is probe the part, and the machine automatically adjusts on the fly. This means less potential for error and faster setups.”

On its VCS 510C, OSM engineers process non-medical parts in stages using multiple vises on the machine’s table. Parts move from one vise/operation to the next and come off the machine complete. As with its Mazak 5-axis, OSM engineers also improve accuracy and shorten machining cycle times when using the 3-axis VCS 510C. For non-medical industries, typical materials include stainless, Hiperco, PEEK, PPS, Inconel, and aluminum.

“On the VCS 510C, we just touch off the tool and run the program. So, no dry runs. The Mazaks are that precise,” comments Scott Wood, a programmer and machinist at OSM. “We’ll use different tools on the same part surface, and each tool blends within a 0.0001". With our other machines, each tool would leave a noticeable step – not with the Mazaks. And tool life, especially with our finish cutters, has really improved because we get zero chatter and better harmonics.”

Medical manufacturing is one of three designated machining areas at OSM. The other two are semiconductor and general industry machining. The medical area is unique in that it has a wider variety of customers and product lines. It’s more of a high-mix, low-volume production environment that requires the ability to maintain quick setup changeovers.

The medical area is a wholly owned subsidiary of OSM called Skeletal FX Manufacturing. All the machines in the area bear the caduceus medical symbol. According to Schneider, the medical symbol allows visiting customers to identify with the shop’s dedicated medical machining capabilities, and the designations serve the purpose for segregating medical workflow.

“Our medical operations are just the start. The upgrade to true integrated 5-axis machining will eventually lead to more Mazak machines at OSM,” Schneider adds. “We continue to re-evaluate our existing cells and systems to determine where we can streamline operations, improve accuracy, and boost output. And we will look to Mazak for the advanced technology to do so.”

Mazak Corp.
www.mazakusa.com

One Source Manufacturing Technology (OSM)
www.osmtech.com