The advantages possessed by roller printing over all other processes are mainly three:
The process of roller printing textile fabrics was patented by Thomas Bell in 1785, fifteen years after his use of an engraved plate to print textiles. Bell's patent was for a machine to print six colors at once, but, probably owing to its incomplete development, it was not immediately successful. One color could be printed well but it was difficulty to keep the six rollers in register with each other. This obstacle was better overcome by Adam Parkinson of Manchester in 1785. That year, Bells machine with Parkinson's improvement was successfully employed for the printing of calico in two to six colors at a single operation.
Roller printing is highly productive for larger print runs. Printing 10,000 to 12,000 yards being commonly printed in one day of ten hours by a single color machine. It is capable of reproducing every style of design, ranging from the fine delicate lines of copperplate engraving to the small repeats and limited colors of the perrotine to the broadest effects of block printing with repeats from 1 in to 80 inches. It is precise, so each portion of an elaborate multi-color pattern can be fitted into its proper place without faulty joints at the points of repetition.
Roller printing is also referenced as cylinder printing or machine printing.
In its simplest form the roller-printing machine consists of a strong cast iron cylinder mounted in adjustable bearings capable of sliding up and down slots in the sides of the rigid iron framework. Beneath this cylinder the engraved copper roller rests in stationary bearings and is supplied with color from a wooden roller that revolves in a color-box below it. The copper roller is mounted on a stout steel axle, at one end of which a cogwheel is fixed to gear with the driving wheel of the machine, and at the other end a smaller cogwheel to drive the color-furnishing roller. The cast iron pressure cylinder is wrapped with several thicknesses of a special material made of wool and cotton lapping, the object of which is to provide the elasticity necessary to enable it to properly force the cloth to be printed into the lines of engraving.
Not all doctors get a medical degree? But even doctors without a degree are very important. One of the most important components of the roller printing machine is the "doctor". In regard to this textile printing machine, the doctor is a thin sharp blade of steel that rests on the engraved roller and serves to scrape off every vestige of superfluous color from its surface, leaving only that which rests in the engraving. The quality of the printing and odds of success rely heavily on the doctor. Its sharpness and angle of inclination to the copper roller varies with the styles of work at hand and is critical. It requires an expert to get the doctor sharpened & set up properly. It takes considerable practical experience to know exactly what qualities it should possess in any given case. In order to prevent it from wearing irregularly it is given a to-and-fro motion so that it is constantly changing its position and is never in contact with one part of the engraving for more than of brass or a similar alloy is frequently added on the opposite side of the roller to that occupied by the steel or cleaning doctor; it is known technically as the lint doctor from its purpose of cleaning off loose filaments or lint, which the roller picks off the cloth during the printing operation. The steel or cleaning doctor is pressed against the roller by means of weighted levers, but the lint doctor is usually just allowed to rest upon it by its own weight as its function is merely to intercept the nap which becomes detached from the cloth and would, if not cleaned from the roller, mix with the color and give rise to defective work.
Larger machines printing from two to sixteen colors are precisely similar in principle to the above, but differ somewhat in detail and are naturally more complex and difficult to operate. In a twelve-color machine, for example, twelve copper rollers, each carrying one portion of the design, are arranged round a central pressure cylinder, or bowl, common to all, and each roller is driven by a common driving wheel, called the crown wheel, actuated, in most cases, by its own steam-engine or motor. Another difference is that the adjustment of pressure is transferred from the cylinder to the rollers which works in specially constructed bearings capable of various movements.