Touch-panel computer and vision sensors automate valve inspection

Friday June 24, 2005
Written by John Lewis
In the medical supply manufacturing business, product reliability and precision is crucial. For a medical IV assemblies manufacturer in the United States, quality control involved manually inspecting sample valves as they came off the assembly line and measuring for uniformity under a microscope. The process was not only arduous for workers, but it also ate up a significant amount of manpower and time.
Automation changed that. "We offered [the manufacturer] a way to make sure their items were perfect every time, while improving [its] manufacturing process automatically," says Pawel Biegunski, president, Vision Controls, Inc., a machine vision integrator from Naperville, Ill. Combining vision hardware from Cognex Coporation with a touch-panel computer from Advantech Automation Corp., Vision Controls created a vision inspection system tailored to the specific needs of the medical supply manufacturer.

With the new setup, vision sensors scrutinizeand a touch-panel from Advantech examine every valve, and confirming their uniformity and communicating the results to a touch-panel computer. The vision sensors use provide process feedback as well.

The automated inspection system combines vision sensors with illumination, optics and machine control hardware. In a compact, self-contained unit, the vision sensors combine a high-speed digital camera with vision processor, a full library of vision software tools, built-in network communications, and a vision spreadsheet interface for application set up.

In order to meet throughput requirements, the automated inspection system uses six vision sensors to perform three individual inspections. The vision sensors are paired so each inspection is performed on two parts simultaneously. To set up the inspections, Vision Controls used the vision sensor's spreadsheet interface, which Cognex designed. The process involves selecting vision tools and parameters from simple drop-down menus. The spreadsheet then automatically generates tool results into worksheet cells, which are then linked together to set up the inspections.

During operation, a rotary table indexes the parts so that each of the six cameras is presented a single part for inspection. Once the parts are in position, each camera independently captures an image and transfers it to its on-board vision processor for analysis. Simultaneously, the inspection system makes three different checks on six valves, with each pair of cameras running a common inspection on two valve assemblies.

The first pair of cameras checks to make sure that the right components are present and properly assembled. Another pair of cameras performs a gauging operation measuring the area of an important valve feature. The last pair of cameras scrutinizes lubricant application, providing feedback to maintain process consistency, and ensuring the right amount is applied to each valve.

Vision Controls designed a software package to collect and analyze the raw data from the assembly line. A touch-panel computer acts as the operator interface for the system.

The vision system is connected to the Advantech operator interface through an Ethernet switch. This allows images of the inspected parts to be easily viewed on the screen alongside vision tool graphics and inspection results. Measurement results and tolerances are displayed in engineering units. Operators may adjust tolerances via the touch-screen display.

In addition to the visual information provided to the operator, each vision system sends pass/fail information to the machine controller (PLC) through the input/out (I/O) lines instructing defective parts to be discarded. Operators can save images of failed parts to the hard drive for later review.

According to Biegunski, Advantech's TPC-1260 touch panel computer was a good fit for this customer. Featuring a 12.1" high luminance display and a low-power Crusoe 5400 processor, the TPC-1260T provided fanless operation in a slim compact design. Weighing less than five pounds, and only two-inches thick, the TPC-1260 was easily mounted from the swing arm on the inspection machine.

"The vision system can, in most cases, yield the result in less than a second," says Biegunski. "In some applications the vision system deals with more than 10 parts per second. Humans can't work that fast."

John Lewis is from Cognex Machine Vision Systems.

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