Automating implant manufacturing: Inspection Efficiency

A polyethylene insert goes between the femoral and tibial components in knee replacements that MicroPort Orthopedics Inc. produces, said Michael Hipp, project engineer/engineering operations at the Arlington, Tennessee, manufacturer. The insert is in high demand and that demand is forecast to continue.

“This part is a double-sided product,” he explained. “It has a lock detail that locks into the tibia and then there’s an articulating surface that mates with the femoral component.”

The insert product line varies by size and thickness to suit the requirements of a diverse range of implant patients, with more than 150 part numbers that require an equal number of part programs, he added.

To satisfy demand, Hipp said the company previously produced them in work cells that consisted of a CNC milling machine for the initial mill lock detail operation, and two other mills on the articulating side due to long cycle times of the articulating surface. MicroPort Orthopedics produces them during its three-shift operation and required scheduling multiple days of overtime throughout the year to keep pace. Hipp said his boss instructed him to contact Phillips Automation, who initially encouraged VersaBuilt Robotics in Boise, Idaho, to move forward with a project to automate insert production. The first iteration of the CNC Mill Automation System from VersaBuilt involved a Universal Robots collaborative robot feeding one Robodrill milling machine and VersaBuilt’s Multigrip base and top jaws to enable a one-operation cycle stop. “Within the application, the trunnion table would rotate on axes, change tools and machine parts to print, and then as the parts were completed, the robot would swap out part blanks, mill lock detail/mill articulating surface for the finished components,” Hipp said. Seeing room for improvement, Hipp said MicroPort Orthopedics “challenged” VersaBuilt to enhance the system to enable one robot feed for two CNC mills. “We paid for engineering time, but it was very well worth it.” He added, “We now have the Versabuilt VersaCart stationing two orders and the Automation System feeding two separate Robodrills. Once the operation is started, all loading, swapping parts from operation one and operation two, and unloading were with one automation system. This in turn freed up time for machinists and machine availability.” VersaBuilt reports that its Mill Automation System allows a machinist to configure a new part in a few minutes and does not require robot programming. Image courtesy of VersaBuilt

The medical implant manufacturer now has three automation systems to produce the implants, with three UR cobots feeding six Fanuc Robodrill compact machining centers, Hipp noted. “The operators are responsible for inspecting the parts as they’re being run on a statistical inspection plan, but then the parts go through a separate inspection area, or final inspection, after the machining process.”

Depending on the part program, cycle time improved from 20 to 30 minutes collectively from start to finish to less than 20 minutes, he explained. “Pretty much the machines do not have to stop, so throughput has improved.”

One aspect of the automation system that Hipp said is beneficial is that end users are not required to do any robot programming.