Category : Automation, process control equipment, industrial communications > Custom automation systems

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Perfectly smooth motion is ensured in a print roller cleaning unit thanks to high performance seals protecting the vital precision drive from the microscopically fine powder used as a cleaning medium.

The units, known as Ultra-Clean and made in Lancashire by Chadwick, represent the state of the art for cleaning and refurbishing of engraved rollers as used in flexographic and gravure printing. They are displacing older wet systems, which had the potential to damage the rollers’ printing surfaces, give rise to health and safety issues, and created an unpleasant sludge, which required careful disposal.

In use the rollers are mounted in a sealed enclosure and slowly rotated while a cleaning head gradually traverse the whole length of the roller and back again, gently applying the cleaning powder. The traversing action is created by a standard OSP electric linear actuator supplied, by Hoerbiger-Origa, as a sealed unit for fit-and-forget installation. Chadwick says that the OSP is the only actuator available that can withstand the working environment within the cleaning chamber because its seal is so effective at keeping the powder at bay.

“Flexograhic ‘Anilox’ rolls working by holding printing ink in tiny cells etched into their surface, there being typically 800 cells per inch,” explains Chadwick director Alan Hall. “The idea behind our machine is to get cleaning powder into every one of those cells and give them a good deep cleaning. To achieve this, the particle size has to be a fraction the size of a cell and the powder has to be applied with care and precision over ever inch of the roller surface.”

The rollers are rotated at 10 rpm by a standard induction motor driving through a wormbox slowly rotates the roller, and the traverse speed is fixed at 20mm/rev to ensure the uniformity of cleaning demanded in the printing industry. A vacuum system mounted in the bottom of the cleaning chamber is designed to remove every single particle from the roller once it has done its duty. A cycle can consist of one, two or three passes (depending on
the need for a light, medium or heavy-duty cleaning) of the cleaning head along the full length of the roller and back again.

During all this time precision motion is essential to ensure a uniform clean, so the servodriven actuator has to perform faultlessly. Chadwick always uses the belt drive option on the OSP, although they could be interchanged for the screw drive or even pneumatic version if a particular customer wished. Theoretically a screw drive is most likely to encounter problems with dust upsetting the precision motion, but such is the performance of the standard seals fitted by Hoerbiger-Origa that they are able to guarantee performance to Chadwick.

“With demanding applications such as ours, no one company can hold all the cards, so we rely heavily on the support of first-class suppliers who provide not only product but also design expertise and lots of customer service,” says Hall. “For some of our trickier designs Hoerbiger-Origa’s motion engineering experience is absolutely essential and their engineers end up knowing almost as much about precision cleaning as we do!”

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