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electrostatic innovations
ESA
Electrostatic Printing Assist ESA GNH61, ESA GNH62ESA GNN75, ESA GNN75S
Answers to central issues in packaging and decorative gravure printing
ESA
1 NEED
Why does gravure printing actually need electrostatic printing assist systems?
In most packaging and decorative gravure printing presses, electrostatic printing assist systems are now a matter of course, because they provide substantial improve-ment in ink transfer, even at high printing speeds. The final product is a higher-quality printed image having high ink and color density.
2
electrostatic innovations
What good is an electrostatic printing assist system in packaging and decorative gravure printing?
BENEFITS
The use of electrostatic printing assist sys-tems is a virtual necessity in packaging and decorative printing. The competitiveness of products often relies on the visual impression created by the packaging or decorative design.
High quality design needs high print quality. This can best be achieved with electrostatic support, because it is the only technology that effectively prevents “missing dots“.
A packaging or decorative gravure press optimized with an electrostatic printing assist system (ESA) provides an immediate competitive advantage – ensuring that your customers will get the best in printing quality.
ESA
3 PRIMARY ISSUE
At first glance, the paper surface appears to be smooth. But, if you look at it through a microscope, you will see that it has a rough surface. In the nip, this irregular
“fiber jungle“ (in a 70 l/cm screen, for example) is faced with 4,900 cells per square centimeter. All of those cells are expected to transfer their ink content to the paper within a split second.
This task, already difficult, is made even harder by the fact that some papers have poor surface compressibility and are not exactly elastic or pliant.
Thus, mechanical contact alone does not always result in a missing dots-free ink transfer. The printability criteria of cardboard, film, coated substrates or pre-impregnated materials also exhibit this problem.
How do missing dots actually occur?
electrostatic innovations
4 SOLUTION
What can electrostatic printing assist actually do to improve printing?
The electric field generated by the ESA in the printing nip causes the ink to be pulled out of the cells and transferred onto the substrate.
Ink transfer to the paper or the film surface with point accuracy – without excessive impression roller pressure. Missing dots are now a thing of the past.
Optimal printing results and regular ink density in all gradation ranges, especially in light and middle tones.
Improved print results also on critical to be printed paper substrates, cardboards, films and pre-impregnated materials.
Higher production speeds
Longer service life of the impression roller coatings through reduced impression roller line pressure.
The results
ESA
5 PRINCIPLE
The Eltex electrostatic printing assist, ESA for short, is based on the principle of the plate-type capacitor. This means that a homogeneous electric field is generated between two plates, in which a dielectric is pulled to one side.
The electrostatic printing assist applies this principle in the nip – at precisely the point where the ink is to be transferred onto the substrate surface.
This principle of ink transfer with electro-static support works evenly over the entire width of the web and operates reliably from the slowest to the highest production speed.
What is the principle applied in the electrostatic printing assist?
electrostatic innovations
6
Top-Loading ESA GNH61 / NEW: ESA GNH62
ESA GNH61 and GNH62 printing assist systems guarantee an optimum ink transfer to flexible materials. The result: a perfect quality in packaging and decorative gravure printing.
With the new HSG62 generator the ESA GNH62 printing assist system achieves performance level d. This is an important metric for the reliability of safety-related functions in accordance with the EN ISO 13849 safety standard.
Direct-Charging ESA GNN75 / ESA GNN75S
ESA GNN75 Core-Charging System The fully automatic, optimum output value setting on the intrinsically safe ESA GNN75 core charging system ensures an optimal print free of missing dots. The charge in the printing nip necessary for emptying the cells is generated directly via the core of the impression roller. This reduces maintenance to a minimum.
The intrinsically safe printing assist system ESA GNN75S EASYCHARGE Exi guarantees perfect results in gravure printing. It works without charging bars or insulated bearings and is suitable for both, sleeves and standard impression rollers. The system is ideal for DC system conversions.
EFFECT
How is the necessary voltage generated in the nip?
The Eltex electrostatic printing assist systems (ESA) are based on the Top-Loading and Direct-Charging principles.
The Top-Loading, the Core-Charging and the GNN75S EASYCHARGE Exi systems are used in packaging and in decorative printing.
ESA
7
Isn’t high voltage dangerous?
SAFETY
The Eltex high voltage generator supplies targeted and controlled high voltage. This guarantees the highest level of safety.
Two safety considerations must be noted. First is the safety of the system when used in potentially explosive atmospheres. Also, wiring of the ESA must be routed as specified in the safety circuit diagrams. Proper installation of these circuits will guarantee optimum safety.
The safety of the Top-Loading system is further improved with performance level d.
electrostatic innovations
8 ESA GNH61 / GNH62 TOP-LOADING
How does the ESA printing assist system reach Performance Level d?
Risk reduction through increased functional security With the new Top-Loading generator HSG62 the ESA GNH62 printing assist system achieves performance level d. This is an important metric for the reliability of safety-related functions in accordance with the EN 13849 safety standard.
The automatic diagnosis of critical situations ensures fewer operating errors and reduced machine failures. Existing ESA GNH61 systems can also reach performance level d by upgrading to the GNH62 system (generator and electrode plug connector).
ESA Top-Loading System GNH61 The ESA electrostatic printing assist ensures the complete and accurate ink transfer onto paper, cardboard or film surfaces in gravure printing, safely avoiding missing dots especially in the light and middle tone ranges.
The Eltex systems are suitable for use in the EX zone in the gas categories IIA or IIB and in water based gravure printing.
ESA
9 ESA GNN75 DIRECT-CHARGE
How do I achieve uniform density in all gradation ranges?
The use of the Electrostatic Printing Assist ESA GNN75 from Eltex makes missing dots a thing of the past. The printing result is a self-enclosed print image with optimal density and intensity.
The infeed paper or film web is discharged through the discharging bar to eliminate any existing residual static charges. The charge is transferred from a ball spring contact through the impression roller bearings and to the impression roller axle and then into the conductive layer of the impression roller covering. This builds up the nip voltage (300 to 900 V DC, 1450 V DC, respectively) required in the printing nip and pulls the ink out of the ink cell and to the substrate without high impression pressure.
Benefits of the system:
Optimal printing results and uniform density in all gradation ranges, particularly in light tones and half-tones.
Improved printing results even on lower quality paper and on highly resistive films.
Higher production speeds
Longer service life of the impression roller coverings by reducing the impression roller line pressure.
Shorter maintenance times because power is transferred directly via the impression roller feed.
No streaking on the impression roller.
The Electrostatic Printing Assist ESA GNN75 is suitable for:
the Ex- and Non-Ex zone
water and solvent-based gravure printing
packaging, decorative and illustration gravure printing
electrostatic innovations
10 ESA GNN75S EASYCHARGE ExI
The printing assist system ESA GNN75S EASYCHARGE Exi works without charging bars or insulated bearings and is suitable for both, sleeves and standard impression rollers.
With its extremely low power demand of less than one watt per meter of web width, the system also ensures the lowest possible charge when printing flexible materials such as films. The intrinsically safe ESA GNN75S EASYCHARGE Exi system is approved for explosion group II A and II B in packaging gravure printing. It guarantees optimal ink transfer with voltages up to 1450 V DC and excellent printing results with unlimited impression roller widths.
The system is ideal for installation or retrofitting existing gravure printing presses. This does not require any conversions or cost-intensive modifica-tions to the impression roller cores or the side frame.
Advantages – dot by dot
perfect printing results
100% intrinsically safe
operating voltage up to 1450 volts DC at unlimited impression roller widths
lowest maintenance
measurement of total volume resistance
no streaking on the impression roller
easy installation or retrofitting for new and existing printing presses
3-layer impression roller can also be used for Top-Loading systems and Direct-Charge systems with insulated bearings
ATEX-approved
Design of the 3-layer impression roller with highly conductive inner layer
Why is ESA GNN75S EASYCHARGE Exi the safest printing assist system worldwide?
Contact ringHighly conductive layer
Potted electronicsSliding ring
ESA
11 COMPONENTS
Dryer
Which are the components of an ESA system?
The high voltage generatorVoltage is supplied via the Eltex HSG61/HSG61EX high voltage generator for GNH61, the safety generator HSG62 (performance level d) for GNH62 and the GNN75 system is powered by the DAG75/DAG75EX high voltage generator.Thanks to the CAN bus concept, up to 20 gene-rators can be monitored.
The remote controlElectrostatic Printing Assist systems can be operated using Eltex Static Control (ESC).This is designed as a touchscreen version and simultaneously monitors all functions of the generators and the entire ESA, including the condition of the bars. Error messages are specified in a number of different languages.
electrostatic innovations
The discharging bars Any printing substrate has a naturally occurring electric charge. Before running into the nip, the web must first be discharged. This is accomplished by the discharging bar R50/EXR50. The web is then charged up at the outfeed area; another discharge bar neutralizes the charges at this point. This means that two discharge bars are needed for each printing unit.
The charging componentIn the GNH61 / GNH62 system, the necessary nip voltage is built up via the R130A/EXR130A impression roller bar – a safe and service-friendly bar.
ESA GNN75S EASYCHARGE Exi The generator is connected to the impression roller via a carbon contact and sliding ring.
The GNN75 system operates without impression roller bars. Voltage is supplied to the impression roller running on electrically isolated bearings via the ball spring contact and the impression roller bearing. Bar cleaning is not required, maintenance work is reduced to a minimum. This means cost savings and a high degree of intrinsic safety.
ball spring contact
ESA
12 CONTROL
Is the remote control actually required or can I operate the ESA without it?
GNH61-System
GNN75-System
Without remote controlWith ESC remote Control The remote control allows the operator to keep control of all parameters and functions at a glance. Each ESA, however, can be operated fully without remote control. Though it has no impact on the performance and capability of the system, the user without remote control foregoes valuable monitoring and operability functions. The safety of the ESA system is guaranteed, even without a remote control. The functions can also be centrally visualized via an interface to the press.
electrostatic innovations
13 EASY OPERATION
Do I have to train my operating personnel or is ESA more or less self-explanatory?
The touchscreen menu assistance of the Eltex Static Control (ESC) with its integ-rated help functions allows the operating personnel to quickly familiarize them-selves with the system.
electrostatic innovations www.eltex.com
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What can we do for you?Eltex is in permanent and close contact with users. The open exchange of information results in custom-made and specific solutions. Joint problem analyses, outline and detail planning, state-of-the-art manufacturing and integration into existing equipment, start-up, maintenance and service accompany each of our projects.
Are you interested in Eltex printing assist systems or in any other Eltex electrostatic innovation? We will be happy to inform you about using Eltex technology in your application and about our range of services. Please contact us.
