WCA July 2016

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54 Wire & Cable ASIA – July/August 2016
Abstract
The optical wrap defect inspection system significantly
improves the quality control of wrapped cable. The surface
and wrapping structure of the cable is continuously
monitored by a machine vision system at production line
speed.
The wrap surface can be viewed live and/or recorded for
100 per cent of the cable length. Surface and wrapping
defects are identified, and images of the defects are
recorded together with position information.
Wrapping information including wrapping angle and
overlap percentage can be monitored for changes. This
technology improves the quality of the cable produced and
prevents defective products from reaching the customer.
1 Introduction
A critical quality issue created during the production of
wrapped cable is surface defects and wrapping defects.
Potential surface defects include scratches or holes, and
potential wrapping defects include uneven wrapping,
incorrect wrapping angle, tape peeling and tape tears.
These defects are not only a cosmetic problem, but they
can lead to the core being exposed to the surroundings,
resulting in short circuits and failure of equipment.
By identifying and detecting these defects during the
production process, immediate corrective action can
be performed and defective sections of product can
be repaired or discarded. Utilising the constant and
immediate feedback from the machine, operators and
process engineers are able to pinpoint the root cause of
the defects.
The wrap defect inspection system utilises one or more
high-speed cameras capturing real-time images of
wrapped cable surfaces. The wrap inspector software is
able to accurately measure wrapping distance and angle,
as well as determine both the type and size of a wide range
of surface defects and wrapping defects.
Surface and wrapping defects as small as 0.1mm can
be detected and an alarm triggered. When a defect is
detected a digital image is enhanced, magnified and
displayed on a remote monitor, enabling the operator to
verify the defects.
This allows operators to determine the type of defect, to
identify false positives (eg, a water droplet), or even detect
surface blemishes (eg, surface discolouring, scratches).
The wrapping angle and distance measurements for the
entire cable are saved to a database along with a record of
any surface or wrapping defect information.
The defect information includes defect type, size and
location on the cable in metres or feet. This allows defects
to be isolated quickly by operators after production
is completed.
The wrap inspector system is able to be easily integrated
into existing production lines and performs well for various
types of wrapped cables and convoluted armouring. The
wrap inspector system makes sure that any problems
are discovered prior to any defective products being sent
to customers.
The lifetime of the lights can be over 50,000 hours of usage
and they are the only consumable part.
2 Current Defect Detection
Technique Limitations
2.1 Laser Diameter Gauges
A laser diameter gauge is used to detect bulges and
neck-downs. The machine uses a laser and shadow
technology to measure the diameter of the cable. The
diameter measurement is extremely accurate and can be
used to classify bulges or neck-downs.
However, there is no way to truly know if the defect
detected is an actual defect. For example, a dust particle
or water droplet on the cable would increase the diameter
measurement, resulting in a false positive.
Optical Wrap Defect
Inspection for Cable
By Craig Girdwood and Andrew McCloskey, Taymer International