Keeping trim: how to recover extrusion waste
German granulator specialist Getecha has been helping one customer – a manufacturer of drive belts – to create high-quality plastic granulate from the edge trims coming off its extrusion lines.
“Whether it is during extrusion or assembly of foils, foams and panels – the continuous extraction of plastic granulate from edge trims provides plastics processors with an excellent opportunity to reduce their raw material, logistics and disposal costs. Reusing the recycled material had a positive effect on the production volume and yields, and the associated reduction of material loss contributes to the sustainability of the whole company”, said Eva Rosenberger, sales manager at Getecha explained.
Working across the granulation, handling and extraction systems designed by the company, which is based in Aschaffenburg, Germany, Rosenberger is involved in the implementation of numerous projects for recovery and recycling systems in the plastics industry.
Recently she’s been working with a manufacturer of drive belts and conveyor belts, with the installation of new granulators. In parallel to the cycling of the extrusion or assembly systems, the new system needed to continuously (and simultaneously) pull in and granulate two edge trims made of TPE or TPU 50-95 Shore A – occasionally with integrated steel inlays.
The group chose RS 2402 E infeed granulators from the RotoSchneider series, which Getecha customised to the specific requirements of the application. The machines were equipped with 4 kW drives, which mean the infeed granulators can handle a granulation rate of up to 80 kg of ground material per hour during operation.
At the client’s request, the machines were also fitted with sound-insulated, compact and stable machine frames with integrated switching cabinet, with guide rollers for mobility. Due to the slim dimensions (750x 1970x1810 mm), they can be positioned next to the assembly or extrusion lines.
As it was necessary to feed the edge trims to be shredded from ground level, Getecha equipped the granulators with additional arms and pulleys (see images above).
Other features of the installation include roller deflection using a ‘dancer arm’ floating roller, which compensates for any traction and vibrations impacting the edge trims.
Two knurled infeed rollers inside the granulator also counteract the transmission of vibrations onto the edge trims, and integrated sensors detect excessive traction and limit the infeed if there is a risk of tearing.
A two-part hopper in front of the infeed opening enables simultaneous feeding in of two edge trims into the roller infeed, without them crossing each other and becoming tangled.
“The correct design of the granulation system and synchronisation of the infeed speed are key factors for its successful integration into the product environment. However, just as important are the requirements of the customer with regard to the quality of the ground material”, said Rosenberger.
The RS 2402 E has an intelligent control for regulating the infeed speeds, which also includes an automatic switch to buffer operation.
When the minimum infeed speed is undercut, this function prevents obstructive fine material and dust particles during granulation, keeping the ground material clean even at low infeed speeds in the range of 0 – 6.0 m/min. Rosenberger explained: “This is achieved by automatically switching into buffer mode, while simultaneously undercutting the optimum outfeed speed. The dancer arm is used as material storage here, and the infeed is activated and deactivated depending on the position of the dancer arm, which thus determines the storage volume.”
Ventilation of the ground material during the granulation process prevents potential material heating, and helps with material flow when processing elastic materials, even at larger quantities. The use of an open-design three-knife-rotor, with a diameter of 240 mm, provides a cutting length of 226 mm, and is equipped with blades of highly quenched and tempered carbide. In case the infeed of third-party material such as steel inlays can’t be avoided, blades of normal quality or high-speed steel (HSS) can also be used.
This RotoSchneider rotary cutters from Getecha can also be equipped with the group’s ‘EnergySave’ system, which reportedly reduces its electrical energy consumption under partial load by up to 40 percent.
In the UK, Getecha's technology partner is Labotek GB.