Inline-Recycling

Digicolor implements solutions for inline-recycling, i.e. within the plastics processing operations. These solutions are based on a comprehensive product range of slow speed granulators for recyclate production. Further precise dosing devices or dosing systems play an important role for inline-recycling solutions. Sprues of engineering plastics such as polyamide (PA), polycarbonate (PC), polyoxymethylene (POM) or polybutylene terephthalate (PBT) are particularly suitable for this form of post-industrial recycling. Recycling of glass-fibre reinforced polymers, such as those used in the automotive industry, can also be realised with Digicolor granulators and metering units.

Inline-recycling with high-quality regrinds

In the first step, it is important to produce high-quality regrind that is characterised by the following quality properties: On the one hand, the recyclate must be available in the most uniform, low-dust granulation possible. Secondly, it must be ensured that recycled material is not thermally damaged by the comminution process. In addition, foreign components such as metal particles must be avoided. Slow-running Goliath toothed roller granulators from Digicolor have proved their worth in meeting these quality requirements.

Such recycling mills can be integrated into the production process as central or as auxiliary granulators. In both cases, the regrind is fed directly back into the production process via special granulate conveying and dosing systems. Central granulators are useful when large quantities of one and the same plastic material are processed on several machines or when rejects are collected centrally.

Adding the recyclate in defined proportions

With volumetric or gravimetric metering units installed on the infeed area of the processing machine, optimum metering of the recyclate into the material column of the virgin material is ensured. The user sets the dosing process with defined dosing parameters via a convenient touch panel control. The main parameters are the shot weight of the plastic article and the percentage of regrind added.

For inline recycling applications where it is important to maintain mixing ratios of regrind and virgin material extremely precisely or to document the weight proportions of the mixtures of more than one component, gravimetric batch feeders should be used. Depending on the application, these gravimetric batching systems can be installed either on the processing machine or next to the machine. Gravimetric batch feeders work in the gain-in-weight method. In this dosing process, each individual component is first weighed before mixing with other components and further processing of the regrind-new mixture takes place. In this way, it is possible to record and document the exact weight of each batch.

Gravimetric regrind dosing for inline-recycling

To save conveying distances and prevent segregation, gravimetric batch feeders are installed directly on the infeed zone of the processing machines where they work reliably despite vibrations. Even with this installation variant, the units can be conveniently operated via manual controls. Once the metering system has been set, the metering process runs in automatic mode independently of the processing machine.

The illustration opposite shows a machine-related recycling application in which the granulator, sprue ejector on the injection moulding machine, granulate conveying system, granulate container and granulate dryer for virgin material are arranged around the processing machine. The gravimetric batch dosing unit for mixing virgin material, recyclate and masterbatch is mounted directly on the screw infeed. A Mini-Goliath toothed roller mill is used here, which reliably processes even the smallest sprues into low-dust, high-quality regrind.

With such a recycling system, even the production of technical plastic products using the recyclates is possible without compromising quality.