The circular economy has long been on everyone’s lips. But what exactly is it? Circular economy means that, for example, when your vacuum cleaner has picked up its last speck of dust after many years of faithful service, parts of it can be used again to manufacture new products. Circular economy, however, aims to go even further: namely, to keep the resources used for production and the resulting waste to a minimum. This is possible thanks to intelligent technologies. And what does this mean for products made of plastic?
Manufacturing sustainable plastics is all about the production process and the equipment involved. The plastic product is manufactured from the plastic raw material, the granulate, in a production plant. Production should of course be efficient, i.e. consume as little energy as possible.
However, efficiency also means being very careful about the plastic being processed. How? For instance, by making parts with particularly thin walls, producing few rejects and feeding production waste directly back into the manufacturing process. Incidentally, this is called in-house recycling.
But that’s not all. It is also important to maintain a consistently high level of product quality and avoid unscheduled machine downtime. This is where digitalisation has a role to play in monitoring the production process with a watchful eye. If necessary, a control system makes adjustments. The major benefit: neither energy nor material is wasted. Digitalisation also allows challenging or new materials such as bioplastics to be processed.
Mechanical engineers again have a role to play in the subsequent recycling of plastics. They supply the technologies for sorting, shredding and washing plastic waste. This is no easy task, since the waste is full of foreign matter such as wood, paper and metal fragments. At the same time, many types of plastic are mixed together and have to be separated again and sorted by colour.
Metal detectors, infrared technologies for colour recognition and compressed air are used to separate light plastic pieces from heavy ones. Digital measuring methods record the degree of purity. Once everything is right, the waste is sent for processing, where it is turned back into granulate – re-granulate – for the manufacture of new products.
The better, cleaner and purer it is, the higher quality products can be recreated from it. The more re-granulate there is in the product, the less virgin plastic is used. This is not easy by any means, but it is the high art of engineering.
During processing and re-granulation, the cleaned, sorted and shredded plastic waste is melted down, just like in the New Year’s Eve tradition of pouring lead or beeswax. The molten mass passes through several cleaning and filtration steps until even the smallest particle of dirt has been removed. The finished re-granulate is then ready for a new life as a plastic product.
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