WCA July 2016

2.2 Spark Tester A spark tester is equipment that can be used to detect pinhole-type defects. The machine creates a spark when there is a pinhole that exposes the core of the cable – conductive metal. However, if a pinhole does not expose the core, the spark is not created. But the pinhole that is not a through hole is still a defect since over time the pinhole could expand and expose the core of the cable. Also, for products without a core (pipe, hose, tubing) or products without a conducting core (fibre optic cable), spark testers are not applicable. 2.3 Vision Systems Prior configurations of surface defect detection systems were unable to identify and measure convolutions of the product. These systems were limited to ignoring the convolutions to identify significant defects such as pinholes or significant bulges or shape changes. The wrap inspection system has been improved with additional image processing software and alternative camera configurations that identifies the wrapped cable profile and can measure parameters and detect variations in the wrapping that are considered defects. 3 Machine Vision Inspection System 3.1 Optical Mechanical Design The wrap defect inspection system consists of one or more high resolution cameras and adequate lighting to capture images of cable moving at speeds more than 1,200 feet (400 metres) per minute. Using multiple cameras, 360-degree coverage of the cable surface can be achieved. The system produces high quality images at these speeds with a very high frame rate. The frame rate is synchronised with an encoder and speed algorithm. The lighting varies depending on the application. The factors in consideration are the reflectivity of the material, surface profile, colour, line speed and camera type. To ensure consistency in the images, the setup features an enclosure to prevent ambient lighting, outside particles, etc from affecting the results. Vibration of the cable is minimised by cable guides, preventing images from being out of focus. An advanced algorithm is used to process the images for cable wrap inspection. A typical algorithm is capable of detecting surface and wrapping defects such as scratches, holes, uneven wrapping, incorrect wrapping angle, tape peeling and tape tears. The algorithm requires analysis of the pixels of the image and grouping them for further interpretation. If a defect is detected, an alarm will notify the operator and an error report is saved to the on-going data log. The defect will also show up on the display for operators to clarify. 3.2 Improving Quality Assurance Suitable for any type of products : Since the surface defect detection system with accurate diameter measurement uses machine vision, it can be used to inspect the surface for many types of wrapped products or convoluted profiles. It is the most thorough method of detecting wrapping and surface flaws available and the advanced algorithm can help classify the type of defects accordingly.

❍ ❍ Figure 1 : Uneven wrapping

❍ ❍ Figure 2 : Surface blemishes

❍ ❍ Figure 3 : Tape peeling

❍ ❍ Figure 4 : Tape wrinkle

❍ ❍ Figure 5 : Armour puckering

❍ ❍ Figure 6 : Discolouration

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Wire & Cable ASIA – July/August 2016