Medical Device Link.

Originally Published PMPN September 2002

Case History

An Eye on Quality

Vision sensors help ensure the quality of glass pipettes for dropper assemblies.

The In-Sight 2000 vision sensor produces precise measurements of pipettes.

When Comar decided to automate the inspection of its glass pipettes, the company wanted a system that would do the job quickly and accurately. The pipettes are commonly used as droppers that are attached to dispensing closures for liquid medicines and nutritional supplements.

"We wanted to be able to maintain very tight tolerances of various dimensions on each pipette," says Mike Ruggieri, manufacturing manager for Comar (Buena, NJ). "There was no feasible way of doing this manually, and we had already had a lot of experience with machine vision from our glass vial operation. So, we decided that putting vision on the pipette lines made sense."

In addition to speed and accuracy, Comar needed the vision sensors to be simple to use so operators with basically no vision experience could easily modify the inspection on-the-fly during product changeover.

After evaluating several systems, Ruggieri chose an In-Sight 2000 vision sensor from Cognex. The sensor consists of a compact, DSP-based vision processing unit, a 640 x 480 x 8-bit progressive-scan digital vision camera, a video game–like handheld control pad, and a library of vision software tools.

"Comar needed to measure its critical operating parameters and requested that the system could measure a factor of 10 below their mechanical detail drawing tolerances," explains Shawn Campion, a Cognex applications engineer. "We wanted to ensure that the sensor was able to yield measurement accuracy to a factor of at least 10 below the desired result. The factor of 10 ensures accurate measurements, while allowing the machine vision system to operate over a wider range of lighting conditions."

To set up the application, a Comar engineering technician used the In-Sight sensor’s vision spreadsheet interface. The process involved selecting vision tools and parameters from drop-down menus using the handheld control pad. The vision spreadsheet then automatically generated tool results into worksheet cells, which were then linked together to set up the inspection.

In production mode, pipettes are fixtured and indexed on a custom-built pipette delivery and handling system at a high rate of speed. As individual pipettes are indexed into the inspection station, two vision sensors are used to inspect each one. The first sensor, positioned approximately eight inches above the inspection point, performs a series of measurements on the pipette tip; the second sensor, mounted eight inches above, checks the diameter of the pipette’s flair. The handling system rotates each pipette 360° during the inspection process to allow for 100% coverage of the pipette circumference. "In addition to checking lengths and diameters, the vision sensors can find cracks that may occasionally form on the pipette tips," says Ruggieri.

According to Campion, proper illumination of the parts was essential for accurate inspection. "We chose to backlight the pipettes in order to minimize reflection."

The entire inspection cycle time for each pipette, between the initial camera trigger and inspection results, is about 210 milliseconds. Operators can see live, zoomed-in images of the pipettes being inspected and inspection results on an overhead monitor that links directly to a built-in SVGA port on the In-Sight vision processor. If any problems are detected, the vision sensor passes a signal to the PLC, which rejects the part.

Since the first sensor was installed last year, Comar has added inspection to additional lines and currently has a total of 16 In-Sight vision sensors deployed across four separate lines.

Ruggieri is now looking to the sensors to help improve manufacturing. "Now that we’re measuring each part, we are integrating In-Sight with an SPC system so it can be used as a data collection tool," he explains. "This way, we can do automatic sampling, establish trends, and continue to further optimize our process."

Beginning in August 2002, Cognex will host a series of free half-day seminars on machine vision technology in major U.S. cities. To register on-line, go to www.cognex.com/seminar, or call 800/677-2646.

Copyright ©2002 Pharmaceutical & Medical Packaging News