Improving energy effi ciency | processing feature


effi cient speed for heating and for production effi ciency. The screw speed should be controlled to give an extrusion rate as close to the maximum as possible and still produce good product.


Choosing the right motor


Most older extruders use DC motors to provide speed control of the extruder screw, but many modern extruders use AC motors with conventional Variable Speed Drives (VSDs, also known as VFDs or inverters) to provide speed control. A summary of these two meth- ods of speed control is given in Table 1.


The widespread availability of VSD controlled AC


motors now makes this the current preferred option for new machines and many extruder manufacturers are removing DC motors from their product range to offer only AC motors + VSDs. VSDs can be used to adjust motors to run at the lowest possible speed (within the allowable torque values) and to reduce energy use to a minimum. The reported achieved savings using VSD controlled


AC motors vary widely. In our tests, the savings were approximately 7-10%, but energy savings of up to 20%


Figure 4: Production costs versus production rate


are widely reported. The exact savings depend on the machine type and speed and, as a general rule, the savings decrease with increasing screw speed. Some tests report even greater savings of more than 30% but this depends on the load and speed. Tip - Sites should always ask for the AC motor +


The Cutting Edge of Strand Pelletizing


• Small lab to large productions


• Custom built, in-house design, engineering & manufacturing


• Spare parts custom built - any make or model


• FREE sharpening for the life of any rotor made by BPM


989.671.9630 Made in the USA bayplasticsmachinery.com


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