WCA January 2020

Technology news

Automated inspection and analysis of plastic pellets

EVEN metallic contamination in plastic pellets can cause problems during the production and processing of plastics. Fault prevention usually requires major effort, but fault correction is time-consuming and expensive. High voltage cables have to be coated with a 100 per cent metal-free plastic insulator. Metal contamination of a submarine cable can cause breakdown (short circuit), leading to very high recovery and repair costs. There are many causes of metal contamination in raw material, such as abrasion both of the metal screws in the extruder and of the barrel. Abrasion can also occur at conveyer pipes and pipe bends. Metal contamination can get into the pellets due to damaged melt filters or a defective granulator. Full protection against metal contamination cannot be ensured, even with the use of melt filters, inductive metal separators or permanent magnets. Sikora AG has developed an offline inspection system that detects and analyses contamination from 50µm in plastic pellets. With the support of X-ray technology, a non-destructive look into and through plastic pellets is possible. Materials such as pellets and metal particles can be differentiated as they vary in their absorption or attenuation of X-rays, and even the smallest metal inclusions in the raw material can be detected. The X-ray unit is hermetically sealed, so no radiation can escape and the standards of the Radiation Protection Act and Radiation Protection Ordinance are fulfilled, and the system can be used by the operator without any concern. The operator places the material onto a 210 x 300mm sample tray; this is moved through the inspection area, which features an X-ray camera, and the inspection and analysis are carried out within 30 seconds. A projector highlights contaminated material in colour directly on the sample tray. The contamination is simultaneously visualised and highlighted on the monitor, including information about its size and area. the smallest

❍ The X-ray based inspection and analysis system detects metallic contamination in plastic pellets

network via LAN interface, and collected data can be exported for processing. The creation of a central and up-to-date data bank allows for conclusions on sources and causes of contamination. The system can inspect pellets, flakes, films/tapes, sheets and injection- moulded parts made from various plastics, such as XLPE used for the insulation of high-voltage cables, TPU or TPE. The height of the test material can be up to 50mm. 100g of plastic pellets can be inspected and analysed per run. With a pellet size of 4 x 4 x 4mm, this corresponds to up to 3,500 pellets. Sikora AG www.sikora.net

In addition to an image gallery of detected contamination, the software provides statistics about size, area and number. Previously recorded image material can be re-imported and evaluated, for example with divergent analysis parameters. In addition to single inspections, serial tests can be performed – any number of samples from a batch can be taken at different times and scanned for analysis. The measuring values are included in the overall evaluation. The collected data provides informat- ion about the process and the material quality of the plastic pellets. The inspection and analysis system can be connected to a company

Ajex & Turner has introduced VNT Nano PCD dies for stranding, compacting and bunching of copper and aluminium, and for low-carbon/welding wire drawing. The dies are designed to reduce consumption of power and metal, to give a bright surface, and to avoid heat generation in the die/conductor. The company has developed VNT Nano PCD dies for the 0.7 to 100mm range for electrodes, CO 2 , welding, stainless steel wire, etc. The dies are made with multi-layer coatings of nanocrystalline diamond through vapour deposition on hard base metal, which provides a smooth surface with low friction. Nanocrystalline diamond has been used extensively to improve the properties of surfaces for manufacturing processes, due to its favourable material properties such as high hardness, improved wear resistance, thermal conductivity, chemical inertness and low coefficient of friction. With VNT Nano PCD dies there is no need for re-polishing or resizing, and there Lower power consumption on continuous use of VNT Nano PCD dies

is no dust accumulation in the die. Ajex & Turner Wire Technologies

www.ajexturner.com

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Wire & Cable ASIA – January/February 2020

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