WCA May 2019

Thus the ZT system offers both immediate and long-term benefits, by preventing release of defective product to customers and by improving product quality over time. It is also easily integrated into existing production lines, or incorporated into new ones. The lifetime of the lights can be over 50,000 hours of usage and they are the only consumable parts. 2 Current diameter measurement techniques and limitations 2.1 Laser inspection gauge A laser gauge is the most common method of inspecting round products for diameter defects. These machines use laser/shadow technology to measure diameter very accurately and to classify lumps and/or neck-downs. However, after a defect is reported there is no way of verifying the defect short of a rewind line. This can lead to false positives from dust or water droplets (for example), which result in unnecessary scrapping or rework of product. Additionally, the lower scan rate of most laser gauges allows many small and moderately sized defects to go undetected when product is moving at a high line speed. Laser gauges can also have difficulty measuring the diameter of transparent materials. 2.2 Previous vision systems Previous generations of vision-based diameter systems compensated for several shortfalls of laser gauges. They offered the ability to save images of defects – allowing a reduction in uncorrected false defects and preventing scrapping and rework. However they faced similar difficulties measuring diameter accurately at high speeds, due to processing and resolution limitations. 3 Machine vision inspection system 3.1 Optical mechanical design The ZT system utilises intense LED backlighting to create a sharply defined product edge. A high-speed camera orientated orthogonally to the product continually captures images of the entire width of the product at speeds up to 3,000m/min. Specialised optical lenses ensure that the product does not appear to change size while it remains within the camera’s field of view. Potential vibration of the product is handled through the use of image processing software to steady captured images. To ensure image consistency and to prevent ambient lighting from impacting operation, the ZT system includes an enclosure for the lighting and camera. Once the images are captured, an advanced algorithm is used to process the images, measure diameter, and scan for diameter defects such as lumps, neck-downs and diameter changes.

❍ ❍ Figure 2 : Image of diameter defect

If a defect is detected by the ZT system, an alarm will notify the operator and an error report is saved, along with an actual image of the defect. The defect will also appear on-screen for the operator to validate or reject. 3.2 Improving quality assurance 3.2.1 Suitable for any high-speed application As Taymer’s high-speed diameter measurement system uses machine vision, it is suitable for scanning for diameter defects on any type of round product, including bare wire, optical fibre, pipe, tube, jacketed wire and more. It is a thorough method of detecting diameter flaws due to its unique scanning algorithm and specialised optical hardware. This diameter measurement technology is currently designed to precisely measure product with an accuracy of 1 micron. 3.2.2 Reduce frequency of defects The system can provide the operator with a view of current product images as well as both the most recent diameter defect and the current cable diameter. This continuous stream of real-time information – especially failure data – allows the operator to isolate the causes of diameter imperfections. Identifying when and how a defect occurs allows technical staff to learn the root cause of defects and reduce their occurrence. 3.2.3 Quality assurance The ZT system will continuously monitor the diameter of the product. The measurements and defect information can be recorded for later analysis. Images of diameter defects such as lumps and neck-downs are captured and saved to a hard disk for use in quality reports. The ZT system’s display makes it easy for engineering and production supervisors to examine potential defects without having to view the defect on the actual product itself – saving significant amounts of time.

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Wire & Cable ASIA – May/June 2019