Rolling machine is a a printing machine in which the printing substrate is fed to the machine from a successively developed roll (s) of paper, or a narrower variant of the roll, i. e. a slitter. This type of substrate feed means that the speed of web-fed printing is one order of magnitude higher than the speed of sheet-fed printing, as there is no slowdown due to the difficulty in picking up the sheets.
Packaging boxes – pros and cons of printing it
The advantage of web-fed machines is also the possibility of using more delicate and thinner printing substrates than sheet-fed machines, as there is no problem with wrinkling the substrate on suction cups, which in sheet-fed machines take further sheets from the stack.
However, the disadvantage of a web-fed machine is the difficulty resulting from the time-consuming acceleration of the roll, which is usually very heavy, and the equally time-consuming stabilisation of the paper sheet on the machine. Generally speaking, once a machine is speeded up, it does not turn off anymore, therefore setting its parameters (colour matching and paint output) is done during operation and wear of the substrate. So winding machines are only worthwhile for large investments, where the losses resulting from the setting up of the machine account for an acceptable small part of the total surface wear. Typically, several thousand copies of the print parameters go off for the print parameter setting.
Web-fed machines – exclusively rotating machines
The use of coil paper also forces the printing to be carried out simultaneously on both sides of the substrate and in all the desired colours during a single passage of substrate through the machine, as it would be difficult to pick up the printed substrate back into the coil. Thus, the printed substrate is usually fed directly to bookbinding machines after passing through a web-fed machine, where it is cut into sheets and folded if necessary.
Due to the high speed of coil machines, usually immediately after the substrate is printed, it is heated in the oven to fix the ink and then cooled on water-cooled cylinders, because after drying the substrate (paper) is brittle. Often, it is also immediately after cooling, coated with a thin film of the print surface protection agent. Only then does it reach the bookbinding machines.
The ground is fed from the coil to the machine by a system of symmetrically positioned pairs of transport rollers, where the distance between these pairs of rollers can change, and in particular shorten. This system allows a relatively large temporary shortening of the web on these rollers without stopping the machine, which in turn enables the beginning of the next coil to be glued to the end of the previous one and the coil itself to be accelerated to the working speed without stopping the machine.