Tissue parent rolls can often contain defects that
pass through the converting process and end up in shipped product.
In many cases this can result in higher production costs, lost
revenue, and customer dissatisfaction.
A WebVision camera system
from Canadian company
Papertech can identify tissue defects down to 5 pixels (1 mm2).
Such detail assists in the correction and elimination of defects,
ensuring shipped product meets and exceeds all quality standards,
and that production time and dollars are spent efficiently.
Papertech's
WebVision solution
is an event-capturing system that allows converting operations
to monitor their processes for breaks and defects. Papertech's
digital cameras, combined with fullfeatured software, provide
very high image speed and resolution images which are used to
monitor and generate alarms when process changes occur. Captured
video breaks and defects can then be tracked to upstream footage
to determine their exact root cause.
Tissue sheet defects can
occur in many areas
throughout the converting process; in the winder, during transport
and storage, or in the unwind, printing, embossing and rewinding
operations on the
converting machine. By monitoring the product throughout the process,
the converting line operator has the opportunity to identify defects,
correct them and ultimately eliminate them.
PUTTING WEB VISION TO THE TEST
The following information was gathered from a converting
facility where the management team was confident that defects
were occurring extremely infrequently in their line. Due to the
confidential nature of the tissue converting industry all identifying
content within the examples shown has been altered to protect
the source.
The Papertech WebVision system was set up to identify
and count the quality defects and reject logs based on the size
of the defect. In one specific location, the criterion was 0.25
square-inch holes (approx 6 mm2). The converting plant was sure
defects of this size were not occurring. When WebVision cameras
were placed on this process, not only were defects this size being
identified, but their frequency was very high - all of these defects
were in fact being shipped as finished product to the customer.
Holes, rips and tears were all found frequently.
Defect rates and sizes per parent roll varied greatly from fewer
than 10 defects (larger than 25 mm2) per roll to lines of hundreds
of repeating defects per roll. The Papertech WebVision system
through automatic tracking was able to reject defect logs, with
greater than 98% accuracy based on a sample size of approximately
50 rejects. This included the ability to accurately identify defects
with greater than 95% accuracy based on a random sample size of
approximately 100 defects that were manually tracked from WebVision's
video records.
REAL-WORLD RESULTS
The WebVision system was set up to run for a one
month period, tracking defects 5 pixels in size and above.
The mill reported: "The system worked very
well. The operators and mill management were extremely impressed.
The system even worked when we ran a printed pattern on the parent
rolls."
Over 100,000 logs were rejected with defects four
times the size of the mill's most lenient defect criterion. The
mill operator was not only able to reject the individual logs,
but also able to reject those parent rolls identified with high
defect rates.
The mill was able to see - for the first time -
exactly what quality of product was being shipped to customers.
They were also able to identify a deeply rooted fault in their
tissue making process that had gone undetected for months.
Over $3 million of warehoused parent rolls were
salvaged through rejecting and recycling the portions that contained
defects. For further information, please contact us at sales@papertech.ca. TW
