Servo drives and compact controllers for folio-size cross-cutters

Speciality papers are easy to process with the RQS-V rotary cross-cutter by BW Papersystems. Its outstanding feature: high paper speeds and fast format changes. The machine manufacturer relies on servo drives and control technology by AMKmotion to ensure that the cutting process runs smoothly.

From pharmaceutical package inserts to baking paper and ID documents – speciality papers are everywhere. But they are challenging to work with: coatings and low grammages of 30 to 40 grams per square metre mean that the handling requirements are complex. There are a lot of manufacturers that produce speciality papers, usually in numerous different small batches.

The Questec RQS-V rotary cross-cutter in particular is ideal for these applications that involve frequent format changes. The flexible-format high-speed cross-cutter offers innovative sheet transport by air, efficiently processing lightweight paper types for package inserts, wet-glue labels, in-mould labels or scratch-sensitive plastic films. With a production speed of 400 metres per minute and extremely short start-up ramps, the machine is ideally suited to small batches and repetitive job changes.

The RQS-V was originally developed by Questec, a brand that has been part of BW Papersystems since 2018. The global company supplies the corrugated board, paper processing and packaging industries, as well as the stationery, bookbinding and security document industries. BW Papersystems has customers in more than 120 countries around the world and currently employs some 1,800 people.

Questec's special rotary cross-cutting technology perfectly complements BW Papersystems’ portfolio, enabling light papers and foils to be cut to the correct size without damage. The distinctive feature here is that the sheets are transported by air. A non-contact air-stream conveyor without belts or rollers eliminates marks and prevents raised corners, so-called dog-ears, or slipped sheets. “The paper is carried, if you like, rather than being pushed,” explains Dirk Puttkammer. The development engineer at BW Papersystems’ Hamburg site is currently working on two new systems that will be delivered to customers in the next few months. The company produces around one to three RQS-V cross-cutters in different sizes per year. “In addition, air slows down the paper at the tray and pushes the sheet downwards to make room for the next one. This creates a kind of shingle stream that prevents damage to the sheets,” explains Puttkammer.

At speeds of up to 400 metres per minute, the machine cuts the sheets reliably and places them gently on the pile. The cross-cutting technology with dynamic drive enables a clean, precise cut with a cutting tolerance of ± 0.15 millimetres per 1,000 millimetres. The high speed and precision make control challenging. “Our experience of the components made by AMKmotion has been excellent,” says Puttkammer. “This applies to both the servo drives and the control units.”

The cross-cutter owes its high reliability to eight AMKmotion synchronous servo motors of the DT and DTK series which rotate the rollers and are driven by AMKmotion inverters. These standard drives are reliable, robust and durable. The motion specialist demonstrates its particular expertise in the area of power electronics, however: the KE/KW servo drive system consists of a compact power supply (KE) and compact inverter (KW) and is extremely space-saving. The digitally operating KW compact inverter modules control the drives precisely and are highly dynamic in four-quadrant mode. They can be networked multifunctionally via various fieldbuses to the master controller.

The RSQ-V uses the KW8, KW10, KW20, KW40, KW150 and KW70 models. The latter is not a standard product but an optimized version of the KW60 that can supply more power. “BW Papersystems uses our established system, which has been available for a very long time but is subject to ongoing further development. We constantly adapt the modular controller cards to current requirements. This allows our customers to keep the machine set-up for a very long time,” says Stefan Hildebrandt, key account manager at AMKmotion.

Here, machine manufacturers such as BW Papersystems also benefit from the components’ small space requirements. The KW150 model has slim dimensions, for example, measuring 425 millimetres in width, 320 millimetres in height and 228 millimetres jn depth. The KE/KW series comprises by far the most compact appliances in this performance class on the market.

The RQS-V also uses two KWD5 double inverter modules with a power range of 2 × 5 kilovolt amperes from AMKmotion’s KWD series. These each contain two independent KW inverters in one housing, making them a cost-effective and very compact solution for low-power servo drives. The KWD series is available for the power ranges 2 × 1 kilovolt ampere, 2 × 2 kilovolt ampere and 2 × 5 kilovolt ampere; the integrated safety function “STO” is available up to PL e in accordance with EN ISO 13849-1.

In addition to the eight servo motors on the cross-cutter, the system also controls the blowers that transport the paper sheets safely to their destination with positive and negative pressure.

A liquid-cooled cooling plate protects the inverters in the switch cabinet from overheating, efficiently dissipating the heat. This liquid cooling system can be constructed much more compactly than a ventilation cooling system.

“The fact that AMKmotion is an important supplier of control technology to us is also demonstrated by the fact that only AMKmotion products are installed in our switch cabinets,” says Puttkammer.

AMKmotion has long been a valued supplier for Questec machines. “AMKmotion was one of the first companies to offer digital controllers,” says Dirk Puttkammer, looking back. “The devices are compact, and several drives can be operated in combination as a multi-axis system – that’s impressive and always has been.”

BW Papersystems also receives various controller cards from AMKmotion that are precisely tailored to the application. This saves costs and optimizes the functions for the individual application. AMKmotion has a large selection of these controller cards in its portfolio, enabling customers such as BW Papersystems to choose a customized solution – for example, there are variants for safety applications or for single-cable solutions. The EtherCAT bus system serves as an interface to the AMKmotion controller.

“Collaboration with AMKmotion works smoothly. I know all the various people in person and if problems arise, I get quick and competent help – even on public holidays if necessary,” says Puttkammer, summarizing the positive experience his company has had with the joint projects. “The service and advice are simply great.” And the good price-performance ratio is another aspect that makes the award-winning products even more attractive of course.

What is more, long-term availability is another great benefit of AMKmotion products. As an OEM, the company guarantees the supply of spare parts to its customers. “Our machines run for 30 or 40 years – something can always break down over such a long period of time.

That’s why it’s so important for us to be able to offer our users repairs even decades down the line. And AMKmotion supports us here, too,” says Puttkammer.