Replacing the cooling rollers
Cooling rollers replacement on presses built before 1997 / 1999 is due to the fact that these rollers (picture A) consist of an external sleeve with an inner steel tank filled with polystyrene; the hydrodynamic force of the water onto the tank had the tank’s pin on operator side undergo alternate fatigue, and these forces, depending on the models, either had the tendency to break the ertalyte bushings used as bearings inside the cooling roller, or the pin itself if, instead of ertalyte, a stainless steel bearing had been used.
In the 90s, a new solution has been designed (picture B): the new cooling roller has no inner tank but just a perforated 1/2″ gas pipe spraying water onto the outer sleeve. This solution is more complex as far as water seals in the discharge / return areas are concerned, but solves the hydrostatic reaction problem. In the meantime, it’s been possible to obtain a low-friction, low-inertia cooling roller with an uniform temperature distribution on the outer sleeve between gear and operator side (which means, a better register), and more reliable, since it’s devoid of inner breakable parts.
The replacement of these cooling rollers on the press’ upper area does not depend on the press model but only on the available room (the new solution, on gear side, is more cumbersome).
- Job n. 3945 – Modification on job n. 2196, Model R940
- Intervention: december 2010
- Job n. 4029 – Modification on job n. 2760, Model R940
- Intervention: december 2011
- Job n. 5211 – Modification on job n. 2775, Model R940
- Intervention: september 2016
The intervention consists of the removal of the old cooling rollers, the drilling of the holes for the new supports, the assemblage and alignment of the new cooling rollers and the connection to the existing plant.
As far as scheduling is concerned, it is a medium-effort intervention per roller (for marking off, holes drilling, pipelines disassemblage) plus another medium-effort intervention for alignment per 8 rollers.
Performance improvements are remarkable:
1) the lower inertia and the increased sensitivity allow to print more sensitive and thinner materials without elongation problems with, consequentely, a better control of the printing pitch
2) the increased sensitivity of the rollers improves also the lengthwise register during speed-up and slow-down
3) since the inner cooling is distributed evenly on the whole surface of the roller’s sleeve, the temperature distribution is uniform on the printed web’s width as well, thus preventing troubles in the crosswise register
4) maintenance intervals increase and there are no more breakages of the inner tank’s pin