gravure flexo global · ing units with all the ink-carrying parts (gravure cylinders, doctor blade...
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FlexoGravureGlobal
The Leading Technical Magazine for the Paper, Film and Foil Package Printing and Converting Industries
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“Deep cleaning” for printing press parts
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Experience
Offset and gravure printing for a wide range of products
With a total of 150 employees, Rahning produces flexible packag-ing, aluminium sealing lids, ther-moformed products and in-mold labels. To manufacture this diverse product portfolio, the company op-erates a number of gravure and offset printing presses and finish-ing equipment on a total floor space of 8,000 sqm (86,112 sqft). Rahning usually operates round the clock: three shifts a day, five days a week.
“Our eight-, nine- and ten-col-our gravure presses print on both sides of the sheet and have long drying sections”, explains Torsten Wadewitz, business unit manager at the company’s Schnellweg site.
“This allows us to process a wide range of stock and finish the prod-ucts with a number of different varnishes, which we can apply in fairly large quantities. Unlike many competitors, we can also process thick foils of up to 1,4 mm (0,06”).” In view of these positive experienc-es, the company plans to invest in another gravure press.
The UV web offset press is an ideal complement to the gravure presses. It is used for high-quality print jobs with smaller volumes and lower pre-press costs.
Complex washing process
Every month, Rahning utilises about 1,300 gravure cylinders and the associated sets of printing unit parts. About 1,200 of these sets
must be cleaned after use. While the cylinders are cleaned manually, other press parts, until now, have normally been washed in two steps. Previously, they were first pre-washed in a washing machine with a high-boiling solvent. Then washed again in a second machine with ethyl acetate.
This process was not only cum-bersome but also required a lot of personnel, particularly because the two washing machines were in-stalled in different rooms. Moreo-ver, the transport of the pre-washed press parts frequently left oily resi-dues on the floor, leading to a higher risk of accidents.
Often the parts were not perfect-ly clean. Over time, they developed a persistent, dark gray patina that could no longer be removed com-pletely. “Cleaning our press parts has also become more difficult in the wake of improvements in the quality of printing inks and var-nishes, especially in terms of adhe-sion and barrier-forming proper-ties,” says Wadewitz.
Requirements and tests in the demo centre
At first, Rahning favoured a solu-tion in which the washing machine would accept and clean the com-
Ansgar Wessendorf
In 2016, the German packaging printer Rahning installed a new D.W. Renzmann washing machine that uses a special cleaning agent. In practice, the combined action of these two elements resulted in “deep cleaning” of the print shop’s ink-carrying gravure press parts.
“Deep cleaning” for printing press partsOptimizing the washing process in a gravure print shop
Impressive results: parts before (left) and after the washing process (right)
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TLS Anilox GmbH
Am Schlinge 20 · D-33154 Salzkotten
T +49 (0) 52 58 / 97 57-00 T · F -028
www.tlsanilox.com
Quality is our passion ANILOX ROLLS & LASER ENGRAVING
Experience
– a Renzmann partner and manu-facturer of special-purpose clean-ing agents.
Prior to the installation, Renz-mann performed comprehensive washing tests with original press parts in the 3400W washing ma-chine manufacturer’s demo centre in Monzingen, Germany. “We were very surprised by the excellent
plete slide-in modules of the print-ing units with all the ink-carrying parts (gravure cylinders, doctor blade assemblies, ink hoses, ink pans etc.) in place. However, due to differences in the design of the var-ious slide-in units and different ink and varnish systems, this solution did not prove to be feasible. 2K varnishes, metallic inks with gold
and aluminium pigments and inks for thermoformed products, which must be highly flexible and hence contain additives and adhesion agents, proved particularly difficult to remove.
In the end, Rahning chose a parts washing machine supplied by D.W. Renzmann that uses an alka-line washing agent by KS Chemie
The D.W. Renzmann parts washing machine 3500W installed at the German package print shop
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TLS Anilox GmbH
Am Schlinge 20 · D-33154 Salzkotten
T +49 (0) 52 58 / 97 57-00 T · F -028
www.tlsanilox.com
Quality is our passion ANILOX ROLLS & LASER ENGRAVING
4 www.flexo-gravure.com Flexo & Gravure Global
Experience
cleaning results, which far exceed-ed our expectations”, says Wade-witz. “Even the stubborn dark gray patina that was so difficult to re-move disappeared completely. The parts are spotless and look as good as new.”
While in Monzingen, the Rah-ning representatives toured Renz-mann’s production facilities, and were impressed by the robust and durable design of the firm’s wash-ing machines and of the excellent results delivered by the various systems.
Designed for hot lye
After an intensive evaluation pro-cess, Rahning decided on the heat-insulated 3500W washing machine with a working length of 3000 mm (118”) which includes a washing basket for the dirty parts, an adjustable basket support, a hose rinsing device and an internal air extraction system. The wa-ter-based washing agent is heated
with thermal oil. For easier mainte-nance, the machine is equipped with an inspection and mainte-nance hatch that provides easy ac-cess to the rear side of the machine.
The adjustable basket support with the stainless steel drip pan can be easily fastened to the basket which means that when the basket
is loaded with dirty parts and pushed into the machine, the drip pan catches excess ink and varnish and helps keep the floor clean. While Rahning chose the machine version with a single loading side, it is worth noting that D.W. Renz-mann also offers a version of the 3500W that can be loaded from two sides.
Efficient cleaning
The automatic wash program consists of the following steps: washing, draining, rinsing, drain-ing, and finally ventilation. During the wash cycle, spray pipes rotating around their longitudinal axis spray the parts (e.g. ink pans, buck-ets etc.) with a water-based alka-line cleaner produced by KS Che-mie and heated to 80 °C (176 °F).
Previously, parts that were not thoroughly cleaned developed a dark grey patina over time which could not be completely removed
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Clean print unit parts after the washing procedure
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Experience
Torsten Wadewitz, head of the gravure printing depart-ment beside the washing machine
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The combination of short spraying distances and high pump capacity delivers excellent cleaning results.
Minimal VOC cleaning system
The water-based alkaline cleaner by KS Chemie is largely free of vol-atile organic compounds, meaning that special explosion protection measures are not necessary. “We still don’t recommend direct skin contact with the washing agent,” explains Wadewitz. “To ensure the operators’ safety, they are required to wear gloves, a helmet with visor and an apron. We have also trained our employees in the correct han-dling of the washing agent.”
The broad chemical-physical ef-fect of the water-based cleaner
makes it suitable for all gravure inks and varnishes used by Rah-ning. Compared to organic sol-vents, the water-based system de-livers more powerful cleaning, re-ducing not only the dwell time in the system, but also the mechanical action needed to clean the parts. Additionally, the washing agent can absorb higher quantities of dis-solved and undissolved substances than classic organic solvents, which considerably reduces con-sumption.
Conclusion
Removing all traces of varnishes and printing inks from press parts in everyday printing operations is a considerable challenge that should
not be underestimated. Frequently, parts cannot be cleaned complete-ly, with all the ensuing negative ef-fects of loose dirt particles during the print run (e.g. damage to doctor blades or gravure cylinders).
The desired cleaning result can only be achieved after several wash cycles, if it can be achieved at all. This makes cleaning an extremely time-consuming process that in-volves several operators.
However, with the combined ac-tion of the D.W. Renzmann wash-ing machine and the alkaline cleaning agent provided by KS Chemie, Rahning has been able to more than meet the challenge. Wadewitz confirmed that after “deep cleaning”, the press parts looked “as good as new”.
Read more articles in our shop:eDossier “Common clean-ing procedures for anilox rolls--an overview”
Comparison of different clean-ing challenges and solutions for anilox rollers that will help improve print quality--evalua-tions of the “aggressiveness” of each suggested procedure.
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