EuroWire November 2020

Technical Article

Online inspection and sorting of plastic pellets The online inspection and sorting system developed by Sikora AG not only uses optical technologies, but also combines them optionally with an X-ray camera. Therefore, even the smallest metal particles included in raw material can be detected by the system. Furthermore, black specks and colour deviations are detected by the optical cameras. Faulty pellets are separated immediately after detection via compressed air. The integrated software provides the operator with a statistical evaluation, with information about the size, area and number of the detected contaminants during production. In addition, impurities are saved in an image gallery. The image information often gives a conclusion about the reason for contamination and supports the operator in the optimisation of the production processes. The recorded data is permanently retrievable and can be separately evaluated at any time.

▲ ▲ Figure 3 : The online inspection and sorting system detects metallic contamination inside the pellet as well as black specks and burns on the pellet’s surface

▲ ▲ Figure 4 : Gallery view of detected

contamination by the online inspection and sorting system

The relevant size for the detection of pellet defects required by manufacturers and compounders has been approximately 100 μm since the 1990s. Due to further technical developments, resolutions from 35 µm or even lower have been possible for some years. A high resolution, however, is not a guarantee for the elimination of black specks, colour deviations and metal inclusions. A safe subsequent sorting process firstly requires a high detection probability. Sikora AG offers this as a unique feature by using up to four optical cameras and an X-ray unit. Depending on the expected contamination and application, the system is configured before dispatch according to the requirements of the operator. It detects and sorts out contamination down to a size of 50 µm. Benefits of optical separation and demetallisation With the described system, manufacturers and processors of plastic pellets can test the produced or purchased goods to 100 per cent, and can separate optical defects as well as metal inclusions. The arising benefits lead to a reduction of: • Production rejects • Machine downtime • Repairs and post-processing of machines and tools • Electrical breakdowns (for cables) • Hot channel damage and distribution blockage (for injection moulding) • Replacement purchase, additional freight, energy costs and set-up time • New processing of replacement material • Additional personnel costs due to extra working time • Recycling and disposal costs • Reputational damage and customer dissatisfaction Consequently, the delivery capability can not only be obtained, but can also be improved because unpredictable risks due to metallic contamination or no longer melting polymer burns can be eliminated. This is an important aspect, especially for safety-

relevant products in the medical, aerospace and automotive area, in order to prevent product failure. Furthermore, for the E&E sector, it can be pointed out that with the reduction of black specks, a reduction of breakdowns can also be achieved. Therefore, black specks are not only responsible for visual defects, but often also for functional defects. Conclusion Only if flawless raw materials are being processed, can common defects in subsequent processes be reduced or avoided. Consequently, the highest possible cleanliness of plastic pellets is of significant importance for compounders and processors alike. It is a prerequisite to avoid waste and to protect natural and economic resources as well as the environment. Simultaneously, quality can be significantly improved for processors and finally the consumers. In this respect, and due to the continuously increasing quality requirements of plastic processors, the demand for online inspection and sorting systems will grow further. New tooling technologies as well as ever-decreasing cross sections in the hot channel and distribution system set higher criteria regarding the raw material to be processed. These requirements can only be fulfilled by future-oriented technologies such as the system developed by Sikora AG. By means of optical cameras and X-ray technology, the system detects online and automatically sorts out black specks, colour deviations and metallic contamination down to a size of 50 µm, and thus guarantees so far unmatched quality. n

Sikora AG sales@sikora.net www.sikora.net

65

www.read-eurowire.com

November 2020