If a machine vision system is done well, it can resolve orders of magnitude in finer detail than the human eye while improving speed and accuracy. However, a number of issues arise when designing and building vision systems for small irregular objects such as hardware limitations, optical trade-offs, and space constraints.
As a systems integrator specializing in machine vision Cyth has faced these dilemmas before, specifically in regards to wire and tubing applications. So after repeatedly overcoming these problems, Cyth released the Wire & Tubing Inspection System (WTIS). This system has been refined over several years and used in many applications. But it wasn't until the summer of 2013 that a global medical device manufacturer caught wind of what it could do.
One of the many devices this medical company creates is an electrode-stent. This stent was designed to be implanted into people's bodies to cure a group of related ailments. The company needed a system to run the length of their part and make sure the stent met very precise specifications. After talking with Keyence about their needs and specifications, Keyence pointed them to Cyth and the WTIS.
Because the stent was 2mm in diameter, the WTIS needed to be slightly modified to operate under high magnification. When dealing with such high levels of magnification Field of View (FOV) becomes a significant issue. The system's telecentric lens FOV was 1mm wide by 3mm high by 0.5mm depth of field (DOF). Thus this small "window" of being in focus was a big challenge. Yet once in focus, the operator can see the very granular details on the stent. And those were the details that needed to be measured.
Due to the length and diameter of the stent the actuator for the system needed to be substituted for a longer one. To date, this was the longest actuator Cyth has used by SMC. The actuator then needed to be integrated with its drivers and the Keyence hardware. The system had two cameras linked to one controller and each camera had two sets of lights, a ring light, and a backlight. Finally, LabVIEW was integrated into the system to pull data from the Keyence controller send signals to the SMC as well.
Because the WTIS is a solution that Cyth has refined over the years, the documentation on this system was extensive. Giving the engineers a solid foundation to work off of and eliminating significant time from the production of the system. Besides the actuator, the algorithm to focus and align the cameras was the only other component that had been modified. A majority of the project was getting the stent focused and centered on the screen. So improving the algorithm was a significant accomplishment.
From the operator's perspective, this is just one of many inspection systems for the stent. The operator would start by taking and loading a stent into the system's fixture, then the operator would flip a switch and the pneumatic clamps would constrain the stent vertically with a little bit of slack. Once the door was closed a tensioner pulley would be activated. If the door is open the system won't run. Once the start button is pressed the cameras position themselves at the bottom of the part. The system begins inspecting the diameter in search of a bottleneck. Once the bottleneck of the stent is identified, the live feed of the inspection begins calculating different granular details as it moves it's way up. Once the inspection is complete the operator enters a serial number and the system logs the pass/fail data to a local database with exact details on why the part passed or failed.
The customer was very happy with the results and the TWIS solution integrated flawlessly into their production line. Because of the success, repeat systems are currently underway and will be transported to their facilities around the globe. Working with customers like these is a privileged, but to see Cyth's fingerprint in the curing of diseases is what continues to fuel the engineers and management's passion for building high quality, reliable systems.