Here is a brief introduction to the use of blades in printing presses. During rotogravure printing a doctor blade will be removing excess ink from smooth and non-engraved parts of the image carrier as well as the land areas of its cell walls. Doctor blades, as well as plastic blades in certain instances, will be used in a number of printing and coating processes, including flexo and pad printing. The term doctor blade has nothing to do with doctoring. It was taken from the name given to the original blades used in flatbed letterpress equipment; namely ‘ductor’.
Blades are necessary to remove all excess ink from cylinders that will be running continuously. As a result, the blades in use will wear away, but not the actual cylinders. Removing and replacing doctor blades are not cumbersome nor are they expensive. But having to replace gravure cylinders on the other hand is going to be potentially financially damaging to the printing business concern. Typical materials used in the construction of blades are, of course, plastic, as well as steel.
Gravure cylinders will be hard-chrome plated while aniloxes could be chromed or even ceramic. Importantly, the rotating position of the blades need to be precise. To help create the precise location of the doctor blade, a doctor blade holder will be used. And to help keep wear patterns as even as possible, as well as preventing particles entering the angles between the blades and cylinders, oscillating doctor blades will be used.
Not utilizing such blades could lead to misalignments and the failure to achieve the desired angles of contact between blades and cylinders. Removing a doctor blade holder is easy, just as long as a removal tool, known as a doctor blade puller is being used.