DOX Electrostat
Electrostatic Spray System
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The use of fast running web offset printing machines has brought about a number of problems which show up in the printed product such as breaking of the fold and breaking of glue or staple bound products, wavy and uneven sheets. The problems are mainly caused by an insufficient moisture content of the paper during the printing process and also by the increase in the web offset printing capacity, the increased printing speed, and higher thermal stress caused by higher temperatures in the drying process. In addition, the growing demand for LWC-papers and uncoated grades with higher qualities requires remoisturizing after printing. Advanced Electrostatic Spray System DOX Electrostat Description The function of electrostatic remoisturizing is based on the effect of spraying very small water particles (micro drops) in a high-voltage field up to 160 kV. Due to the high electrostatic loading the micro drops are charged and accelerated without loss toward the paper web. The sheet absorbs the spray mist very quickly and the micro drops penetrate through the paper pores into the fibres. |
The DOX Electrostat consists of a high-voltage frame, spray beams, a counter roller and a complete PLC control unit. It uses the method of indirect charging which means that the nozzle bar itself is not electrically charged. The flow rates for each nozzle are controlled from the control cabinet. The water particles are sprayed by the grounded nozzle damper into the high-voltage frame. Only in this frame are the water particles charged and accelerated towards the paper web. The water particles, besides being charged within the high-voltage field, are broken down in size and at the same time accelerated at high speed towards the paper web. The spray density in an electrostatic moisturizing system amounts to 150 - 200 particles per measured unit whereas a density of only 25 - 50 particles p.u. can be obtained in conventional moisturizing systems. Particle size in the electrostatic moisturizing system is approx. 5 microns. The DOX Electrostat can be installed in web offset machines, paperback Printing Presses and special converting machines to solve the problems described. Page 1 of 2 |
