WCA July 2016

Optical Wrap Defect Inspection for Cable By Craig Girdwood and Andrew McCloskey, Taymer International

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.

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Wire & Cable ASIA – July/August 2016