The continuous progress in the development of gravure and flexographic products, e.g. during the manufacture of flexible packaging, labels, wallpaper, serviettes, etc., causes changes to the manufacturing and production process and thus frequently increased demands on existing printing presses. A recurring criterion is the capacity of the existing drying systems and also their production velocity limiting or quality-reducing capacity, due to the increased quantity of residual solvent in print, reduced production speed, etc.
For the user, interesting and economic solutions always arise when already available, but adequate convective drying capacities can no longer be extended or modified through additional units so that they comply with the increased drying demands.
In many cases, the use of the MICOR *KIR DRYING TECHNOLOGY based on short-wave infrared radiation to assist drying or for additional drying is suitable here.
MICOR *KIR DRYING SYSTEMS are BG-/ GS [federal & industrial safety associations] tested. Integrated MICOR *KIR EMITTER COMPONENTS comply with the essential safety and health requirements of Directive 94/9/EC (ATEX) for utilisation in an atmosphere capable of exploding, e.g. in the circulation operation of convection dryers up to 50 % LEL. They are proof tested with regard to construction design by an accredited certification agency. Dryer models are possible for the utilisation of up to and including T3 solvents.
Process testing facilities on site
A major module that must not be disregarded in all theoretical drying optimisation designs is that of process control, which must be provided to the user for a conversion.
To carry out drying tests on existing printing and coating machines, where possible in accordance with the intended optimisation, is an essential precondition for the user as well as for the drying supplier, and should be provided as specific operational trials under production conditions with appropriate drying facilities.
Fig.: MICOR *KIR SIMULATION DRYING EQUIPMENT for carrying out specific operational trials on site on an existing rotogravure printing machine
Applied examples from flexographic printing:
8- colour central cylinder flexographic printing press, PP foil transparent 30 mue, printing ink solvent based, max. printing speed 130 m/min., after that the ink double prints in case of half tone printing at throughout ink application to the respective printing applicators because the existing drying performance of the conventional hot air curing dryer is insufficient. The printing plates used here must be cleaned elaborately in relatively short periods of time.
Fig.: MICOR *KIR INTER UNIT DRYER, fitted on a W&H
central cylinder flexographic printing machine
This problem was solved by MICOR through the development of a MICOR *KIR INTER UNIT DRYER, a combination of air and infrared radiation (in line with the external dimensions of the hot air blower to be replaced). With the installation of a MICOR-*KIR INTER UNIT DRYER instead of the respective hot-air blower a printing speed of more than 180 m/min can be achieved, whereas the cleaning of the printing plates can be omitted and the machine idle time caused by the cleaning can be reduced.
In case of an application of printing ink dilutable in water to coated paper instead of solvent ink the maximally possible printing speed is limited to 60 m/min. This is due to the insufficiently dried ink which will be double printed and peeled off and/or partially solved over the last applied coating varnish. By using a MICOR-*KIR INTER UNIT DRYER of identical construction instead of the respective hot air blower the production speed could be increased to more than 200 m/min.
The same application possibilities showed up for a central cylinder flexographic printing machine with a throughout ink application of 2K white solvent ink to PP foil. Due to the application of the MICOR-*KIR INTER UNIT DRYER the production speed could be increased and the amount of the residual solvent in print could be reduced at the same time.
The reduction of the residual solvent during printing with 2-K printing inks on PP foil (snack wrapping) from approximately 35 mg/m² to under 10 mg/m² due to the application of a MICOR-*KIR CASSETTE as final dryer after the tunnel drying of a central cylinder flexographic printing machine.
Similar good working results can be achieved with the after-treatment of an already printed and confected automatic machine foil by using a MICOR-*KIR CASSETTE as final dryer.
*MICOR GmbH, D- 65510 Idstein
