Tension control system cuts downtime and waste at sheet maker

A UK-based manufacturer of rubberised printing sheet is benefited from reduced downtime and waste after fitting a new tension control system to its high precision pressing machine.

More than 12 months ago, Willie Allan, chief engineer at Day International's production plant based in Dundee, calculated that it was time to replace the existing DC-drive based tension control system on the first of three main processing machines. The press operates around the clock to produce 40,000 square metres of sheeting each month, so it is important that downtime is kept to a minimum. This first processing stage involves attaching the rubber to a fabric backing via an accurate rolling process. This complex web application requires keeping a consistent tension on the fabric backing as it is fed into the press. "We contacted our local drives supplier JR Power, who recommended that we fit ZF EKU hysteresis clutches to each of the unwind systems and an EBU brake to the onwind assembly, " explained Willie Allan. "We had considered a manual clutch system, but rejected the idea due to risk of contamination from dust, a problem avoided by the magnetic, non-contact operation of the hysteresis units." Allan also said the ZF units were easy to fit and that set up and programming was quick and simple. After 12 months of faultless operation at the Dundee plant, Allan said a similar ZF assembly was fitted to a machine that controls the adhesive curing process of the rubber sheeting. This three-way web application includes two inputs of rubber sheet, which are spliced together either side of a paper layer, enabling the materials to be separated once they have been pressed and fed through a curing oven. Grinding the surfaces of the cured rubber sheeting is one of the final operations in the process and yet requires the highest levels of tension control. The three grinding machines at the plant flatten the sheets to tolerances of 10 microns and each requires a very slow feed system to achieve the desired result. "Due to the excellent performance of the two other systems, we also recently upgraded the crucial final grinding machines with ZF clutches and brakes," explained Allan. "The results were very favourable, with increased output, reduced wastage and downtime. Other benefits became apparent as we could also standardise on spares and the ZF ERM control interface allows us to troubleshoot more quickly and easily than any other system we have used."