QMT Features: May 2011
Glowing reports
FMI in Chicago masters silicone molding of critical medical components using an automatic vision system with superior digital imaging to provide accurate measurements

At its stand-alone manufacturing facility in Elk Grove Village, Illinois, FMI produces diverse implant grade and disposable molded silicone parts. Long-term implantable silicone parts are used in medical devices (pacemakers, defibrillators, heart valves, etc.) designed for prolonged or extended service. Other silicone items are used in sealing surgical instruments, neuromodulation devices, ophthalmic systems, and other medical devices. As a majority of FMI silicone products are implanted in the body, the FMI facility houses ISO class 5, 6 and 7 clean rooms, fully equipped for silicone mixing, molding, inspection and packaging operations.

As a medical silicone company, FMI complies with qualification processes that ensure silicone material cleanliness, part shape integrity and the lowest failure rates. Important in this regard is FMI’s choice for the table-top iNexiv system from Nikon Metrology, a high-performance CNC precision video measuring system. FMI demands  an optical system because silicone parts are too soft to be measured using a touch probe. Fairly large specimens can be measured with the Nexiv system because it features a 250 x 200 millimetre stage and a 200 millimetre z stroke.

“It is night and day compared to our other vision system,” said Harold Sant, engineering manager for FMI in Elk Grove Village, when looking at the first images taken by the iNexiv vision system. “The new Nikon inspection system generates overwhelmingly clear and pinpoint sharp images of difficult-to-measure silicon samples. Silica-based elastomeric rubber material attracts light and has a characteristic mystifying glow, but the iNexiv sees right through it. We have quickly come to trust the system, because it generates a superior digital image to measure from.”

Inspection is key in FMI’s Part Development & Prototyping (RPD) programs. Recently, FMI was contracted for a silicone header part of a pacemaker system to shorten the time between prototype and production. The header part goes on top of a pacemaker assembly and bundles all leads and connections. “Based on elaborate iNexiv measurements performed on different cuts, our engineers fine-tuned the header part concept to ensure optimum moldability. Low-distortion optics and high-intensity white LED illumination provide superb imaging that leaves no room for any operator misunderstandings. Even the header’s intricate features could be investigated easily without requiring any re-checks. We used image magnification up to 20x, which is way below iNexiv’s maximum magnification of 120x.”

Economics of automatic inspection
Measurement throughput used to be the bottleneck when dealing with prototype qualification batches. Harold Sand says that instead of inspecting header parts manually, FMI engineers teach the iNexiv system to perform a number of dimensional measurements fully automatically. “Defining an inspection job following our own measurement techniques is easy and very similar to setting up a macro. Automatic inspection takes a jump start with intelligent search capabilities and pattern recognition, which automatically spots the header part position and orientation. In the automatic inspection job we also included wall thickness measurements, a capability offered as part of the Nikon AutoMeasure software. Thanks to automatic iNexiv inspection using fast stage controls, we were able to reduce the start-to-shelf time for the pacemaker header part from 4 days to 1 day and a half!”

Sant says that pre-production and production operations at FMI probably benefit even more from automatic inspection. “iNexiv proves to be a major timesaver, considering the millions of silicone parts we produce every year. The shift from manual to automatic inspection led to a 3 month payback time for our system, just in labour alone.”

The complexity of the parts has increased tremendously. FMI invests in state-of-the-art processes and equipment to deliver the sophisticated ultra-clean silicone product required for surgical implantation. Based on expertise built up over the years, FMI is recognized as a leader in insert molding and bonding of silicone to various substrates. “High precision and process validation is key in the medical device business, to make sure critical silicone parts can be confidently incorporated into lifesaving medical devices and state-of-the art laboratory equipment,” remarks Sant. “The Nikon Metrology iNexiv system is ideal to measure any of our silicone molded parts, including micro-precision parts manufactured to the tightest tolerances. It outperforms our previous manual video measuring system in terms of measuring accuracy and speed as well as repeatability and reproducibility. We notice that leading medical device manufacturing firms trust our inspection qualification and validation reports better, because the majority of them are Nikon users themselves who know the system we are using.”l

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