Automated quality control

In healthcare, many single-use devices made from plastics must be manufactured in high volumes while meeting strict hygienic standards. Among them are syringes, vials, and catheters.

One major European manufacturer partnered with custom manufacturer MGS Manufacturing Group to mold catheters. MGS has several cleanroom production sites worldwide for healthcare customers, including a cleanroom molding factory in Ireland where the company molds medical catheters.

Quality control

For quality control, all catheters had to be visually inspected before shipping. The traditional, manual inspection and sorting process required more than 30 workers to complete, posing several problems.

“Respective of the location of the production site, it is very difficult to find such a number of qualified and committed employees,” explains Shawn Krenke, vice president of MGS’ Equipment Division. “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.”

With an evident need for automation, MGS’ in-house experts developed two automated inspection and sorting cells in Ireland.

Inspection, processing, sorting

First, molded catheters are deposited into a hopper at the input side of the cell and dispensed into a vibratory feeder system that orients the catheters correctly and delivers them 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 four inspection cameras which scan for defects such as embedded particulates, unsightly material spotting, and pinholes in the tip. The system also inspects catheters for material shorts or other non-compliance issues that may have occurred during the two-material/two-shot molding process.

Handling catheters

After inspection, a Stäubli TX2 6-axis robot picks the eight catheters off the transfer arm and separates those that failed inspection. As systems deliver inspection reports on each part, the robot knows which ones have passed or failed. 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 8-position gripper assembly that can individually select and release the catheter as required. A pneumatic manifold mounted directly on the robot’s arm controls the grippers. Each cell can inspect, sort, and package more than 50 catheters per minute.

When designing the cell, the MGS engineers rated flexibility highly.

Electrical engineer Craig Nisleit says, “No tooling change is required when switching between variants. Furthermore, we designed the system to minimize the changeover time. All process changes are handled electronically when the user selects a new recipe from the machine human-machine interface (HMI).”

One common programming platform

Each robot uses a Rockwell Automation control platform and EtherNet/IP network and features an Allen-Bradley CompactLogix 5380 controller. The integrated system allows for one programming platform, saving time by streamlining design.

Stäubli’s uniVAL programmable logic control (PLC) robot control solution 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.

In addition, the TX2 series includes 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.

The TX2 series’s compact size in relation to its maximum payload (3.7kg and 920mm max.) also make it suitable for the application. Another strong point is its ±0.03mm repeatability.

Stäubli