Liquid Lens Technology Helps ID Code Reader Increase Read Rate from 75% to 100%
A roll rotator machine in an Owens Corning fiberglass manufacturing plant is responsible for orienting rolls of fiberglass so that a barcode is visible when the rolls are stacked on skids. In the past, two different ID code readers operating in parallel had a combined read rate of only 75% due to difficulty focusing on different sized rolls and the need to read through shrink wrapping. Read failures required the operator to manually intervene in the automatic sequence to ensure the label was on the top of the roll. Occasionally the system would have a false hit and transfer the rather large roll with the label near the bottom, requiring significant physical effort to adjust the roll on the skid.
“We invited an engineer from Cognex to take a look at our application,” said Frank Peel, Electrical Support Specialist for Owens Corning. “He mentioned that Cognex had recently added liquid lens technology to its DataMan® 200 series readers specifically to address applications where variable focal length causes problems. We agreed to work together with Cognex to see if we could find a solution to this problem.” The liquid lens module is an electronically controllable variable focus system offered on Cognex DataMan 200 ID code readers. Cognex is the first company to release an industrial fixed-mount ID reader based on this new technology.
Cognex and Corning engineers jointly developed the idea of mounting the reader near the bottom of the rolls vs. at the top looking down. This had the advantage of reducing the variation in the focal length of the 9 to 22 inch diameter rolls. Mounting the reader near the bottom however introduced a complicating factor. It was no longer possible to simply stop the rotator when the ID code is detected because the code is supposed to be on the top of the roll instead of one the bottom of the roll. The answer was to read the code twice and calculate the time gap between the two readings to determine how fast the roll is rotating. Then, after the code is read the second time, the roll is allowed to rotate for one-half revolution to advance the code to the top of the roll before the roll is stopped.
“Cognex guaranteed this approach would work, so we tested their guarantee and the DataMan 200 ID reader did what they said it would do,” Peel concluded. “The adjustable focus lens and ability to finely tune the setup using a computer screen has helped us achieve nearly a 100% read rate. It’s difficult to quantify the exact savings but it’s obvious that our ability to read and position every roll has freed up considerable time on the part of our operators. Our production rates have continued to increase since we installed the new ID code reader so it’s likely that we would have had to add manpower if we had not made this and other improvements.”