by Brittany Willes, contributing writer
Plastics Business
Integrated process control, automated quality inspection and reduction of bio-burden – that is what injection molder and contract manufacturer Intertech Medical, Denver, Colorado, set out to accomplish with the development of its latest machine-side, automated work cell. “We incurred three customer complaints within six months,” stated Intertech President Jim Kepler. “We knew something had to change.”
Three defects within six months may not sound like much, but when the defective part is used for retractable needle design for intervascular delivery of critical medications, even such a small number is too big. According to Kepler, the problem was due to undetectable “micro-shorts.”
“The part itself is very intricate, with incredibly tight dimensions, including five living hinges,” said Kepler. “When the molten plastic flowed through the part, it went through a lot of different high- and low-pressure scenarios. This created a very narrow process window.” Intertech operators were visually inspecting 100 percent of the parts as they were packaged while a QA department performed dimensional and visual inspections every two hours. A Coordinate Measuring Machine (CMM) performed tight-tolerance dimensional evaluation of statistically sampled parts. Yet, it wasn’t enough. The micro-short defects were undetectable except during final assembly at the customer’s facility.
Throwing more operators at the machines, doing more visual inspections and using more labor were not effective ways to go about solving the issue. Instead, Intertech reached out to Wittmann Automation, as well as Keyence Vision Systems, to work with Intertech’s team to design a camera system supported by automation capable of detecting micro-shorts. “The system was programmed to look at the number of pixels that represented a good part vs. the number of pixels on a camera image that represented a bad part,” stated Kepler, “then we would inspect the cavities with that criteria.”
In addition to the camera inspection, Intertech chose to implement increased process control. According to Kepler, because the process had such a tight window, Intertech set low and high limits that were exceedingly tight on machine positions, temperatures, pressures and speeds essentially everything that went into making a good part. Next, Intertech utilized a watchdog software system.
“Basically, we programmed the machine software to look at the process and monitor it 100 percent,” said Kepler. “Every single shot was monitored and, if anything exceeded the high or low limits, it tied that logic into the robotics, and the robot would reject the part.”
However, once the part was molded, a risk of micro-shorts remained. It was critical to implement a vision system. “Once molded, we presented the parts to the vision system, which looked for micro-shorts or any type of twist or deformation of the part,” explained Kepler. “We’re talking about looking for a flaw less than one-thousandth of an inch, something incredibly difficult to see with the naked eye, even with the assistance of magnification.”
If the part passed the visual inspection from the cameras, it would then be presented to a surgical steel gate trimming station. Finally, the parts were segregated, sorted, auto-bagged and counted out – exactly 1,000 parts per bag – eliminating any future counting issues. Furthermore, repetitive injury risks to operators were eliminated.
“The gate trimming was being done 100 percent of the time by operators,” explained Kepler. “Going forward, the automated system has eliminated the risk of repetitive injuries and reduced bioburden-associated contaminants that come from having operators handling the parts.” With the work-cell, the robot has control of the part from the time it leaves the mold until it is packaged. “Simply put, biological-burden by humans is never introduced to the parts,” he said.
In designing the work cell, Intertech took an FMEA approach – Failure, Mode, Effect and Analysis. “We had representation from every department, whether it was tooling, engineering or production,” said Kepler. “Everyone worked together to create a risk analysis of all the different ways the work cell could possibly fail.”
For instance, process engineers determined that micro-shorts were most likely to occur at start-up. By conducting temperature studies, it was found that temperatures were stable after 10 shots. “We programmed the robot to reject the first 10 shots at start-up, no matter what,” said Kepler. “It wasn’t worth taking the risk of even presenting to the camera a part that might be sub-quality.
“Everyone gave their perspective of what risk or failure would look like, and we designed the entire cell to make sure that we handled or covered that issue,” Kepler continued. “I think the approach the team took to outline every possible failure or risk and address it was wholly successful, and they did an amazing job.”
As a result, Intertech’s operational and labor efficiencies have increased substantially. “Increasing trust, confidence and overall customer satisfaction through our ability to deliver zero defects has been the real win,” Kepler affirmed. “We haven’t had a single supply interruption or delay with shipping, and we’ve provided our customers with 100 percent quality parts.”
Customers aren’t the only ones who are impressed. Intertech received the 2017 MAPP Innovation Award for its automated work cell utilizing integrated process and quality control. According to Kepler, the award validates Intertech’s customer-focused strategy of providing zero defects through integrated, quality compliance solutions.
