Improve Quality: Metallic Impurities In Plastic Granulates

Even the smallest metallic impurities in plastic pellets can cause considerable problems in plastics production and processing. In contrast, the industry has high-quality requirements (and associated strict standards) for materials and the resulting products, making it clear that the detection of metallic impurities and continuous monitoring during the production process is extremely important. A new quality control system combines X-ray technology with automatic offline inspection and analysis.

Almost always a high level of effort is required to avoid errors and an even greater effort to eliminate them. The dismantling of injection moulds alone, the replacement of hot runner systems or the reworking/repair of cavities are both time and cost intensive. Rebecca Zachau from Sikora presents in an article for the trade journal ‘Plastverarbeiter’ a new system which should significantly improve this situation.

With the help of X-ray technology, a non-destructive view into or through the plastic granulate is possible. In addition, there is an equally advantageous differentiation between different materials such as the granulate and the metal particles in question. Thus, chippings trapped in the raw material can be detected - and as the X-ray unit is hermetically sealed from the environment, no radiation escapes to the outside, so that the requirements of the Radiation Protection Act and the Radiation Protection Ordinance are fulfilled.

How Are The Impurities In The Plastic Analysed?

The substrate is guided through the inspection area equipped with an X-ray camera on a sample carrier. Within 30 seconds the inspection and evaluation takes place, whereby a projector directly marks contaminated material in colour. At the same time, the monitor displays the size and area of the contamination. The X-ray images automatically detect, visualise and evaluate metallic contamination from 50 μm upwards on the surface as well as within non-transparent, coloured and transparent plastic granulate.

 In addition to individual tests, the system's software also permits series tests and thus valuable comparisons throughout the whole manufacturing process. Moreover, the system does not work in isolation in the operating process - it can be connected to the company network via a LAN interface and the collected data can be exported for further processing. The whole unit is a mobile offline testing device on wheels, which can be used for spot checks outside the production process in the laboratory or directly next to the production line.

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