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Flexo Gravure Global The Leading Technical Magazine for the Paper, Film and Foil Package Printing and Converting Industries www.flexo-gravure.com Requirements for “neat” printing

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Page 1: Gravure Flexo Global

FlexoGravureGlobal

The Leading Technical Magazine for the Paper, Film and Foil Package Printing and Converting Industries

www.flexo-gravure.com

Requirements for “neat” printing

Page 2: Gravure Flexo Global

2 www.flexo-gravure.com Flexo & Gravure Global

Initial situation

The old wash room and its outdat-ed equipment simply could not keep up with modern standards, in terms of cleaning efficiency and compliance with increasingly strict legal requirements. Hence the new wash room project was of vital im-portance to the packaging printer. All the more so because a cleaning process that removes all sol-vent-based residues from gravure cylinders, splash guards, doctor blade holders, ink troughs and con-tainers in line with the relevant

legislation also helps reduce the fire hazard. Today the old wash room is used to store flexo sleeves.

The capacities of the washing machines and the distillation unit had to be designed to allow for continuous 24/7 production of the flexo press and the two gravure presses in a three-shift operation. This means that the Renzmann de-vices and machines needed to be able to withstand the extreme con-ditions of nonstop operation.

Because the components are cleaned using solvent mixtures, the wash room is an explosion-risk

area (hazardous area) which ac-cording to Dutch legislation must comply with special regulations and laws such as the ATEX direc-tive.

Schut Flexible Packaging want-ed to keep using its wash room as long as possible during the re-mod-elling. Renzmann was able to grant this wish and made a significant contribution to the completion of the new wash room. This included installing the washing machines and distillation unit (including pip-ing, electrical components and connections) and training the cus-tomer’s staff.

To begin with, all old equipment in the wash room was dismantled and disposed of, as it did not com-ply anymore with ATEX regula-tions nor with the cleaning quality requirements, MAC limits (maxi-mum allowable concentration of harmful solvents) and the econom-ic and logistic requirements of a state-of-the-art packaging printer. But these were not the only prob-lems that would be solved with the re-modelling – the usual solvent odour and frequently heavy soiling of walls, floors and machines are notably absent in the new wash room.

The new wash room is equipped with three different Renzmann units, all of which use solvent and are hence protected against explo-sion.

Washing machine for gravure cylinders

One focus of the comprehensive re-modelling of the wash room was the solvent washing machine for gravure cylinders. This special ma-chine can clean two impression cylinders at once and meets a cru-cial, but difficult challenge: It re-moves persistent, slightly dry ink and varnish residues from the tiny cells of the gravure cylinder, leav-ing them perfectly clean.

The machine also meets another requirement that is becoming in-

Ansgar Wessendorf

Perfect cleaning of gravure print formes, flexo sleeves, Anilox rollers and accessories such as containers, doctor blade holders or ink troughs not only extends the service life of these components, it also helps ensure a smooth printing process with flawless results. To maintain this high standard in its day-to-day work, Dutch packaging printer Schut Flexible Packaging decided, two years ago, to invest in a new wash room complete with clean-ing and solvent distillation equipment.

Requirements for “neat” printing

Experience

The ROTOmaX solvent distillation unit

Page 3: Gravure Flexo Global

Experience

an external gear motor during the wash cycle. The machine is equipped with replaceable filter sets, a solvent level control system and an internal air extraction sys-tem. The automatic wash program (PLC) includes the steps “Washing – Rinsing – Draining – Air Extrac-tion”, all of which can be selected individually.

creasingly important for Schut Flexible Packaging. Due to steadily decreasing run lengths, the compa-ny must process a greater number of jobs on flexo and gravure press-es per shift, leading to more job changes. This in turn increases the number of cylinders that must be cleaned and made available for the next job as quickly as possible.

That is why the Renzmann washing machine is designed for short cleaning intervals. The entire process cycle – from a dirty to a

clean cylinder that is once again ready for use – takes only up to 10 minutes.

The gravure cylinders are loaded into and removed from the wash-ing machine from above. The crane places the dirty cylinders into the machine so that the cylinder jour-nals rest on the carriage. The roller pairs of the carriage are driven by

Dutch printer rich in traditionSchut Flexible Packaging, a mid-sized business with a staff of 80, is one of the oldest packaging manufacturers in the Netherlands. Founded in Schiedam in 1932 under the name of “Superieur Verpakkin-gen”, the company relocated to Etten-Leur in 1956. In 1998 it became part of Flexible Pack-aging Holding, which also in-cludes Lemapack Flexible Packaging and Hellema Verpa-kkingen. Schut Flex ible Pack-aging owns two gravure press-es, one flexo press and addi-tional equipment for foil lami-nation, wax application and roll finishing. The company’s comprehensive portfolio in-cludes cigarette packs, yeast and butter wrappers, candy wrappers, stand-up pouches and foil bags.

The washing basket with dirty splash guards and doctor blade holders is waiting for the next wash cycle in front of the parts washing machine

Loading a dirty gravure cylinder into the washing machine

Page 4: Gravure Flexo Global

Experience

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Cleaning flexo sleeves

On its central cylinder flexo press, Schut Flexible Packaging uses only elastomer flexo sleeves with direct laser engraving that are cleaned automatically with solvent outside the press using equipment by SMB Schröder Maschinenbau, a partner of D.W. Renzmann. The sleeves can be loaded manually into the wash-ing machine in just a few minutes and the machine can hold up to five sleeves.

Parts washing machine

The parts washing machine is de-signed to clean ink troughs, hoses, containers, doctor blade holders and a number of smaller items and comes with a powerful washing pump/ex-proof motor unit. This is a front-loading washing machine with a closed washing chamber and separate washing agent tank that is integrated into the machine. The parts are placed into a remov-able washing basket, then the bas-ket is pushed into the chamber and the door is closed.

Cleaning can only be started once the machine door is closed. Spray rotors and a stationary rins-ing system ensure thorough clean-ing of the components, and remov-able strainers protect the spray sys-

tem, pump and pipes from clog-ging or damage caused by screws or other foreign bodies. The solvent level in the integrated solvent tank is controlled automatically (operat-ing level; maximum level). Solvent vapours are extracted quickly and completely from the machine via a powerful fan and pneumatic air in-take and air mixing flaps. The ma-chine is also equipped with a meas-uring and regulation system that monitors the solvent concentra-tion. The automatic program for parts cleaning includes the steps “Washing – Draining – Rinsing – Draining – Air Extraction”, which can be selected individually.

Solvent recovery

The contaminated solvent pro-duced by the washing machine-sand the flexo and gravure presses is transferred into the first contain-er (capacity: 2000 litres) of the au-tomatic ROTOmaX distillation unit by Renzmann. Once the solvent in the container reaches a volume of 1000 litres, automatic distillation begins: The contaminated solvent in the cylindrical boiler, which consists of an isolated dome and flange-mounted heating floor, is heated (10 bars and 185 °C max.) until it begins to boil and evapo-rate. The unit can distil 1000 litres of used solvent in approximately 11 hours.

The solvent vapours liquefy in the water-cooled condenser and the clean solvent flows back into

More than washing machines and distillation unitsFounded in Monzingen in 1969, Renzmann manufactures and sells washing machines and distil-lation units for the graphic arts and the paint producing indus-tries. Today the mid-sized compa-ny with roughly 150 employees is one of the world’s leading suppli-ers in both of these segments. In-ternational support teams and service engineers, and a network of more than 75  international agents and partners provide cus-tomers with expert and compre-hensive advice and ensure a high availability of the products.

The portfolio ranges from sim-ple and robust manual washing machines to technically sophisti-cated distillation units and wash-ing machines for gravure cylin-ders, anilox rollers and miscella-

neous parts; in addition, Renz-mann offers project planning and implementation. This integrated approach also includes compre-hensive advice and services be-yond the completion of installa-tions and projects. In the Renz-mann lab, customers can test var-ious cleaning methods on washing machines using their own components (cylinders, roll-ers, containers, ink pumps etc.) or watch a demonstration of wash-ing solvent recovery in the distil-lation unit.

The newest addition to the Renzmann portfolio is the Flex-plateCleaner for cleaning photo- polymer flexo plates, which Renz-mann offers in two sizes – 480 x 180 mm (18.9” x 7.1”) and 560 x 180 mm (22.1” x 7.1”).

Two gravure cylinders in the washing machine after cleaning

Gravure cylinder storage room

Page 5: Gravure Flexo Global

Experience

Flexo & Gravure Global www.flexo-gravure.com 5

the second container. A rotating scraper keeps the heating surfaces of the boiler clean and ensures a good heat transfer and high distil-lation output. It also agitates the solvent and keeps the discharge valve free. Once distillation is com-plete, the rotor carries the paste-like residue through the open dis-charge valve and into a disposal container. Additional manual cleaning of the distillation boiler is not necessary.

The distillation residue at Schut Flexible Packaging is approximate-ly 6% of the original solvent quan-tity, i.e. 60 litres for 1000 litres of used solvent. This relatively liquid residue is quicker to discharge into the disposal container; on the other hand, it still contains quite a lot of valuable solvent. With the ROTO-maX, the viscosity of the residue can be adjusted to each customer’s requirements.

Whether the distilled solvent is used for washing, adjusting ink viscosity or inline cleaning in the

printing presses depends on its composition. Schut Flexible Pack-aging uses different solvent mix-tures for gravure printing and flexo printing. These mixtures are not separated after use, but pumped to-gether into the first container of the ROTOmaX unit. That is why the

clean solvent produced by distilla-tion is analysed to determine its composition, which may vary de-pending on how frequently the dif-ferent printing methods are used. The decision on where to reuse the solvent is based on the results of this analysis.

Flexo sleeve storage room

Page 6: Gravure Flexo Global

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ISSN 2194-279X

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