Fast intelligent drives

Intelligent drives, servo-drives and servo-motors are at the heart of Rotary Logic Systems’ bespoke highly specialized printing, converting and finishing machines.


Every system made by Rotary Logic Systems is bespoke, whether it is precision security foiling for anti-counterfeit applications, specialised in-line, high speed flexographic / gravure printing processes or sophisticated machinery for the medical industry. The company, based near Southampton, supplies both stand-alone machines and modules to integrate into all applications in the converting and finishing industries.

“We need drives that are flexible in operation, straightforward to program and with very fast response – that’s why we use mainly Digitax ST Plus servo-drives from Control Techniques,” says Alan Chandler – Director of Rotary Logic Systems. “The speed of response we need on many modules just cannot be achieved with external PLCs. The response times, because the drives’ processors are within the drives themselves, are much faster!”

A typical project is a series of six lines for a manufacturer in India. Each is a multi-stage anti-counterfeit line for packaging incorporating high precision application of a hot-foil hologram. The lines have web widths of 1320mm, and each comprises unwind and in-feed, foiling, flying head die-cutting, flexographic printing, out-feed and rewind. A total of 30 drives from Control Techniques are on each line – 9kW Unidrive SP drives control the unwind and wind operations, whilst Digitax ST Plus servo-drives twinned with Unimotor FM motors control the feeds and all other processes. A variety of SM-Application modules are employed on many of the drives – including SM-Register, SM-Ethernet, SM-I/O – and the whole line is co-ordinated using Control Techniques’ own high speed network, CT-Net, with the web material drive acting as the ‘Master’. There are two points of registration – one to the pre-printed material and one to the applied product. A repeatable accuracy of ±0.1mm is required for the foiling process – and this is achieved with a line speed of 80m/minute!

“With changes in the needs of our client, we had to devise a system that maintains accuracy of application on an inconsistent substrate,” explains Alan Chandler.  “This has been achieved within the software – Control Techniques has worked alongside us for two years to help develop this – and we believe it is unique in the finishing market.” The software compensates for errors for every image, keeping each within tolerance.

Rotary Logic Systems has been a major user of Control Techniques’ drives, servo-drives and motors for some six years, buying many hundreds each year. “We particularly like the Digitax ST series of servos,” says Alan Chandler, “not just because of their flexibility and performance, but because of their compact size. Equally the compact size of the Unimotors is critical on many lines, including the lines supplied recently to India. But, above all, it is our relationship with Control Techniques’ engineering and software departments that has been so important over the last few years. As a company they are prepared to be flexible and provide excellent support.

Rotary Logic Systems is headed up by Alan Chandler, the electronics specialist, and Paul Taylor, who provides the expertise in mechanical design and printing processes.