There are basically two methods. One possibility is the repellet and at first glance seems advantageous such a variant for the handling of the intermediate product (pelletising), but has the disadvantage of a contribution of thermal energy to the raw material, which in turn modify its properties of melt (index of fluidity). In addition, it gives rise to high energy costs.
The other is a very practical solution to the implementation of the system asr ("automatic scrap recovery"). The asr system consists of three basic elements whose mission is to collect, aspire and carry the Strip, shredding the material and replenish the ground.
A soplante injector (according to the principle of Venturi nozzle) generated at the point of suction vacuum necessary and carries a mill of Court of film strips.
On top of the mill is mounted an air separator. Which separates the flow of air transport of the aspirated strips. These lateral strips fall freely in the Chamber of Court of the mill. The mill must meet special requirements, such as the ground materials produced must be realimentable without any problems and have the following properties:
Particle size and a spectrum of size of particle, high apparent density, good compaction and clean of the same court.
Appropriate are the mills to work according to the principle of the scissors.
With this method of breakdown is not transmitted almost no thermal energy to the material and the Court has done is clean...
The advantages are: does not melt the material in the Chamber of Court (no blockage) and no change of the index of fluidity of the material.
Opcionamente can provide a food mill rollers. A blower for the ground transports the material to the nerve center of the system, namely the feedback RMX machine.
The flow of air transport and particle separation takes place in the cyclone, which is mounted on top of the machine of feedback.
A feedback RMX machine consists of two separate chambers.
Through the external camera feeds Virgin material and in the internal Chamber is transported and compact material milled using a spindle in direction to the entrance of the extruder.
At the bottom of the machine of feedback both flows come together but not unmixed, i.e. a "thread" into another "thread" are transported materials Virgin and ground respectively to the extruder.
The mixing of the two takes place in the extruder. Many times feedback machines are confused with the so-called trash compactors, as those in an asr system lead uniformly ground material compacted to the extruder and thereby remain excluded oscillations in downloads (pumps).
The sizing of an asr system is especially made for each line of production under consideration of the following data: total capacity of the installation, ratio of feedback, properties of the material, width and thickness of the material and the characteristics of the extruder.
It should pay close attention to the implementation of the extruder, that finally the feeding of the extruder capacity makes the maximum capacity of the feedback.
The ratio of realistic feedback varies on average between 25 percent and 35 percent in many cases.
An asr system can supplement without any problems with the gravimetric mixing and control system in extrusion of Process Control, represented in Spain by A-5 Açinco Compoundier & Extrusionstechnik, S.L.
Mixing always complies with the specification and the regulation of the production capacity is possible.
The asr Process Control system stands out for its reliable technical principle and high profitability. (globally supplied more than 4,000 times).
The costs of investment as a rule have amortized from 3 months to 1 year for the saving of raw material matería. The only asr system represents yet another part of the energy costs of the Regranuladores or Agglomerators.
The contemplation of the profitability and the change of the index of fluidity compared with both these systems, were corroborated scientifically in a work of the "Bergischen Universität – school Superior of engineers of Wuppertal" and whose result has univocamente the advantages of the asr system.