The principles and advantages of Electrostatic Printing Assist
The use of an Electrostatic Assist System (ESA) enables the cells in the cylinder of the gravure printing machine to be fully evacuated of ink and prevents the occurrence of missing dots, which are as a result of ink not being transferred to the printing substrate, and is essential as a prerequisite for an optimum quality of print. ESA systems have become standard fixtures throughout the world, particularly when printing on paper, card and plastic film substrates, enabling a high quality of print to be maintained irrespective of factors such as impression roller characteristics, viscosity and machine speed.
To this end, the impression roller is charged with a controlled d.c. voltage creating an electric field in the gap between the impression roller and the earthed cylinder, the strength of which can be varied between 300 and 1600 V dependent on the needs of the job in hand. Using Coulomb’s Law, a force is brought to bear on the ink by this electric field and this results in the complete evacuation of the ink from the gravure cylinder cells, preventing the build-up of dried ink residue in the cells and ensuring optimum transmission of the ink to the substrate.
Innovative Charge Bar
The main feature of the ENULEC patent protected Special Top Loading System is a virtually maintenance free air assisted charge bar, previously unknown in the gravure packaging printing industry. Compared to the charge bars with open arrays of charging pins used in the past, this new and innovative technology offers the benefit that frequent cleaning is no longer necessary. This is achieved due to a special charge bar construction whereby the charging pins are bedded completely into a small tube where they can not be contaminated by particles of ink or dust. Purged by slightly pressurized air at a pressure of about 0.5 to 1.5 bar in the area of the pin points, a build up of dirt due to ink or substrate dust is prevented.
In introducing this innovation, particular attention was paid to overcoming the various weaknesses associated with conventional ESA top loading systems with exposed charging needles, particularly as these relate to safety. Included among such weaknesses is the need for unwanted machine stoppages which are necessary due to the need for frequent and regular charge bar cleaning. Additionally, there is a significant drop in the efficiency of conventional ESA top loading systems as ink and dirt builds up on the exposed charge bar pins. Not only is there a drop in performance but there is also an increased safety risk if the maintenance and cleaning of exposed needles is poor, as there is a possibility of sparking between the open pins which, when printing with solvent based inks, can lead to fires in the printing unit. A special alloy used by ENULEC in the manufacture of the pins provides a life expectancy of up to 20 years.
Special Features : Technical Innovation
1. Direct Charging
Gravure printing is characterized particularly by its outstanding quality of print which has been further improved by the Enulec ESA Direct Charging (Core Charging) system leading to the establishment of new standards. This technical module has been employed with great success particularly by world leading gravure printing machine manufacturers from Italy and their customers. The Direct Charging System is based on a current transmission unit which charges the core of the impression roller (sleeve mandrel) via a specially developed fluid transmission system so as to ensure the evacuation of ink from the gravure cylinder and its transfer to the printed substrate. A pre-requisite for direct charging is that the impression roller cores / sleeve mandrels must be isolated from the machine earth. The transmission of the voltage required to produce the ESA effect is achieved in the Enulec system via a specially developed, maintenance-free fluid transmission system. The impression roller core /sleeve mandrel distributes the voltage uniformly over the full width of the impression roller without any significant loss of power. As a result, the system is suitable for use with low cost single layer or sleeve type impression rollers. In conjunction with a specially developed capacitance-free generator, the current transmission unit can be used to achieve the best print results on all substrate materials, even under critical conditions. Even in extremely dirty printing conditions, the system remains maintenance-free and does not require time intensive cleaning programs. The uniform distribution of the direct charge ensures optimum printing results and there is virtually no wear caused in either the impression roller or the printing machine.
No more disruptive electrostatic charges
Enulec’s highly effective EST-DC Static Discharge System which has been successfully established in the market for fifteen years removes unwelcome electrostatic charge not only in gravure printing machines but also from roll slitting machines and laminating machines. Free ions ( both positively and negatively charged ) are fired at the travelling web of film at high speed during the winding process. During this process the positively charged ions on the web recombine with the strongly accelerated negatively charged ions coming from the DC- discharge electrode.
The EST-DC-LDS discharge system operates over a range of approximately 20-800 mm and does not need to be adjusted for webs having differing static charge. By virtue of its special direct current technology the system can successfully eliminate all combinations of electrostatic charge and there is no need to use additional alternating current discharge systems on the winder.
ENULEC a Germany manufacturer located near Hamburg has made significant in-roads in the field of Electrostatic Assist and static elimination in safety, performance and reliability. Enulec specializes in optimum charge and discharge systems for the printing, converting and packaging industries utilized in the printing of FILM, PAPER and Carton Board. ENULEC is best known for their ENULEC ESA1000 Dot Skip Eliminator system utilized by the leading OEM rotogravure press manufactures and high quality gravure printers worldwide. Owned and managed by the Dettke family for over three decades. Managing Director, Christoph Dettke along with Vice President, Joseph Steingraeber closely manage their strategically positioned sales and service forces that include multiple ENULEC trading companies and 38 partner companies worldwide in order to assure every international customer receives first class response to their electrostatic requirements.” Founded in 1981 by Hubertus and Christa Dettke the company now maintains a leading market position in the electrostatics field. Since the 1980s, ENULEC has concentrated on the design and supply of first class electrostatic printing assist systems and discharging systems, developing expertise applicable in this area. This expertise, including the skills necessary to install and service the equipment, is shared by the international team working for the company, all of whom have been with ENULEC for many years. ENULEC has supplied over 6000 ESA systems to customers including member companies of the largest groups involved in the flexible packaging, cigarette package and décor printing industry.
Strategically Positioned for the Global Gravure Industry
A world wide sales and service network secures Enulec’s leading market position ensuring proactive customer support relationships. In addition, there are three primary Enulec trading & service hubs supporting thirty-eight partner companies that personally care for Enulec’s international customers. The majority of worldwide companies producing print for packaging, décor print and gravure publication are installing Enulec ESA and Static Discharge Systems of varying types with great success, often for many years.
Enulec Electrostatic Sagl im Lugano, Switzerland provides significant contribution to the company’s international success. Since its establishment in 2005, Arnold Dalla Bona has headed this Swiss subsidiary company. Its main function relates to the sales and marketing of ESA and Static Discharge systems to the Italian gravure printing market. Of particular importance is the maintenance of the excellent relations which exist with the German and Italian gravure printing machinery manufacturers who dominate the industry worldwide and to whom Enulec are original equipment suppliers.
The gravure printing machines currently on show in the technology centres and showrooms of these German / Italian machinery manufacturers are equipped exclusively with Enulec ESA systems. New solutions geared to market requirements are developed jointly with OEMs resulting in soundly based and seamless developments.
All leading European manufacturers equip nearly all of their modern gravure printing machines with Enulec ESA and Static Discharge systems which are offered to gravure printers worldwide as a complete ready made turnkey package. This machine configuration offers the customer simplicity of operation and ensures an optimum printing process for FILM, PAPER & Carton Board.
Enulec America Sales and Service Center looks after customers on the American continent. Joseph K. Steingraeber, Vice President Global Markets, backed up by his Enulec partners provides customer focused Service and Support.
Enulec offers a complete range of tailor made ESA customer solutions (Standard Top Loading, Maintenance-free Top Loading, Core Charging, Side Loading). These solutions contribute significantly to a stable, standardized and highly productive printing process while meeting the highest of safety standards. Additionally, EST range static discharge systems enable plastic film processing companies to remove problematical electrical charges from the unwinders/rewinders in roll slitting, laminating and printing machinery. This facilitates not only a safe but a smooth and continuous production process.