Sellers Engineers has developed a patent-protected Fibrebak machine that processes waste and used carpet. It features 17 axes of Lenze drives, ten of which have built-in positioning functionality for achieving precise machine settings.
The Sellers company was founded in 1912 to service the local cloth industry in West Yorkshire. Sellers came to specialise in carpet finishing machinery such as coating, shearing, backing and drying. As well as the Huddersfield factory, new in 2011, Sellers has an operation in Georgia, USA, which services North and South America. In recent years the rising cost of waste management has opened the market for recycling machinery. Carpets make high volumes of waste, which is costly to dispose of, and incineration is not a practical alternative due to toxic chemicals in the backing. The USA market was looking for machines to separate nylon-based fibres from the carpet backing so that the fibres can be reused. The machines had to suit both carpet manufacturers who have to dispose of edge trimmings, and waste recycling companies handling end-of-life carpet.
Sellers Engineers' new Fibrebak pile removal system separates the fibres from the backing and gives separate outputs suiting both carpet factories and post-consumer waste processors. An infeed conveyor is manually fed with carpets or carpet tiles. The carpet is brought to a horizontal saw blade that is finely adjustable to the heights of the pile and backing. Vertical motion is achieved through 10kN screw jacks and positional accuracy is achieved with the aid of motor-mounted 2048-pulse encoders. Separate outfeeds deliver fibres to the side of the machine and backing material to the rear. A touch screen operator panel is positioned to the front and side of the machine to make it easily accessible for operators.
One of the main advantages offered by the Lenze system is the way 10 inverter variable-speed drives have integrated positioning functionality. On the Fibrebak machine, positioning is required to set the height of the blade head, the tracking and the blade grinding wheels. The Lenze L-force 8400 HighLine inverters feature point-to-point positioning with the associated travel profiles and 100kHz evaluation of encoder signals, all without the need for external control. Set-up is made simple with L-force engineer software, and a plug-in memory module enables drives to be exchanged without reprogramming.
The Lenze equipment on the machine ranges from the motors right up to the screw jacks and the inverter drives. CAN is the chosen fieldbus, as it is standard at no extra cost in the 8400 inverter drives. The CAN network covers the 10 HighLine and a further two L-force 8400 StateLine inverters. The remaining five motors are fixed-speed units.
Further system simplification and cost reduction is achieved by the Safe Torque Off (STO) option on the Lenze inverters. This is certified to ISO 13849-1 Performance Level e (PLe), meaning that after a safety stop signal the machine can be worked on without fear of uncontrolled movement. The STO option means that a safety contactor between the drive and the motor is not required. Furthermore, there is no need to disconnect the power to the drives, so a restart can be instantaneous without waiting for the drives to boot up. Safe Torque off is a popular option on all 8400 drives that invariably reduces cost through system simplification.
A mix of motors and geared motors is supplied by Lenze. For intermittent duties such as adjustments, worm gearboxes are suitable because they are low cost and the energy losses through inefficiency are insignificant. The same applies to the screw jacks, which have short running times. Where the duty approaches 100 per cent, for example on the feeds, high-efficiency geared motors are supplied such as the type GKR, a bevel helical design with wear-free efficiency at around 96 per cent. Power ranges from 90W for the blade tracking up too 11kW for the blade drive.
For the Fibrebak machine, Sellers Engineers needed easy operation and simple low-cost positioning, which they get from the 8400 Highline inverter drives. The additional simplification and cost reduction from choosing the STO safety option was a bonus. The Fibrebak design is heavily based on the drive technology. The drive package from Lenze makes sense in terms of a single point of responsibility that led to easier engineering.