In the healthcare industry, many plastic single-use devices such as catheters must be manufactured in high volumes in accordance with strict hygienic standards. MGS Manufacturing Group recently automated the inspection process for a major European manufacturer of two-material, two-shot molded products. It turned to two Stäubli TX2-60L six-axis robots to handle the catheters after inspection with high precision, and the robot controller is integrated into one programming platform.
Stäubli is a mechatronics solutions provider focusing on connectors, robotics, and textile equipment. Originally founded in 1892, the Pfäffikon, Switzerland-based company today operates 14 industrial production sites and has more than 5,500 employees across 60 locations in 29 countries. It said its network of agents in 50 countries provides innovative solutions to all industrial sectors.
Catheter maker faces inspection challenge
To maintain quality control, all catheters must be visually inspected before they are shipped. Previously, the manufacturer inspected and sorted the devices manually. This task alone required more than 30 dedicated workers.
This posed several problems, explained Shawn Krenke, vice president of MGS’s Equipment Division. “Irrespective of the location of the production site, it is very difficult to find such a number of qualified and committed employees,” he said. “Furthermore, the workers can become fatigued during the shift, and the inspection decision-making process can vary depending on the operator performing the task. This may have an impact on the results of quality control“.
The medical device maker understood that this task could benefit automation and partnered with MGS. Germantown, Wis.-based MGS is a custom manufacturer that delivers tooling as well as molding and comprehensive equipment services, taking on the role of a single-source supplier on a worldwide basis. The company has several cleanroom production sites worldwide for healthcare customers, including a cleanroom molding factory in Ireland, where it molds the medical catheters.
Case study at a glance
|Company:||MGS Manufacturing Group|
|Location:||Site in Ireland|
|Industry:||Contract manufacturing of medical devices|
|Challenge:||Visual inspection and sorting of catheters|
|Solution:||TX2-60L six-axis robots, plus eight-position grippers and control software|
|Task:||Hygienic inspection and handling of products|
|Value driver:||Maintaining quality control|
|Results:||Two workcells can inspect, sort, and package 50 catheters per minute.|
MGS develops cells with cameras, robot arms
MGS used its in-house expertise to develop two automated inspection and sorting cells for its Irish plant. It used four cameras for inspection and sorting, as well as robot arms and grippers for handling the catheters.
In the workcells, molded catheters are deposited into a hopper at the input side of the cell and then dispensed into a vibratory feeder system, where they are oriented correctly and delivered into a servo escapement. The escapement separates eight catheters at a time for pickup by a servo transfer robotic arm.
The transfer arm passes the catheters through each of the four inspection cameras, which scan for defects such as embedded particulates, unsightly material spotting, and pinholes in the tips. The catheters are also inspected for “material shorts” or other non-compliance issues that may have occurred during the two-material/two-shot molding process.
After the inspection is complete, a Stäubli TX2 six-axis robot picks the eight catheters off the transfer arm and separates those that failed inspection. As the systems delivers inspection reports on each part, the robot knows which ones have passed or failed. The non-conforming products are discarded into a secured access non-compliance bin. All accepted catheters are layer-packed into the final reusable packaging tote.
The end-of-arm tooling on the robot features an eight-position gripper assembly that can individually select and release the catheter as required. Control of the eight grippers is accomplished using a pneumatic manifold mounted directly on the arm of the robot. Each cell can inspect, sort, and package over 50 catheters a minute.
The MGS engineers make flexibility a high priority when designing the cells. “No tooling change is required when switching between variants,” said Craig Nisleit, an electrical engineer at MGS. “Furthermore, we designed the system to minimize the change over time. All process changes are handled electronically when the user selects a new recipe from the machine HMI [human-machine interface].”
Common robotic control helps yield results
The robot of each of the two cells is integrated with a Rockwell Automation control platform and EtherNet/IP network and features an Allen-Bradley CompactLogix 5380 controller. This integrated system provides one programming platform for both the robot and the cell, which saves time and money and streamlines the design process, said Stäubli.
Stäubli said its uniVAL plc (programmable logic controller) is the tool that integrates the robot into the control platform of the complete cell. The uniVAL plc allows the CompactLogix controller to drive the robot through a fieldbus using simplified function blocks. MGS said that uniVAL was one important reason, though not the only one, why it chose to use Stäubli robots.
Another advantage of the TX2 series in this application is the closed housing, which facilitates a cell design complying with hygienic standards. Even in the series version, the robots fulfill the specifications of ISO cleanroom Class 5. For higher requirements, the Stäubli TX2 robots are available in special cleanroom versions.
Furthermore, the TX2 series is the appropriate robot for this application because of its compact size in relation to its maximum payload of 3.7 kg and maximum reach of 920 mm, said Stäubli. Another strong point is its repeatability of +/- 0,03 mm, said the company.
In addition, the MGS engineers cited “soft factors.” They said they recently had success with a different automation project involving Stäubli robots, and they appreciated the follow-up and front-line support of the company’s staff.
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