The inking system， or inker， of mostlarge sheetfed presses in Figure.3-7 usual-ly has at least ten rollers and Consists ofthe following parts：<br> Ink fountain- a pan that contains the ink supply<br> Ductor or ductor roller - a transferroller that alternately contacts .the ink foun-tain roller and the first roller of the inkingsystem， often an. oscillator<br> Oscillators or..vibrators- gear-orchain-driven rollers that not only， rotate butoscillate from side to side， distributing and smoothing out the ink film and erasing imagepatterns from the form roller<br> Intermediate rollers， friction-or gravity-driven （ Le. ， surface-driven） rollers be-tween the ductor and form roller that transfer and condition the ink; often called distributorsif they contact two rollers and riders if they conact a single roller， sush asan oscillator<br> Form roUers-a series of three to.four rollers， usually of differing diameters， thatcontact the printing plateand transfer：ink to it.<br> The series of rollers excluding the ink fountain and fountain roller is often referred toas the roller train. The roller train is comprised of a series of alternating hard and soft roll-ers..The hard rollers are usually-steel covered with copper， ebonite，， or nylon. The resili-ent rollers （ ductor，intermediate， and form rollers） are often made of a synthetic rubbersuch as PVC （polyvinyl chloride）， Buna-N （ a copolymer of butadiene and acryioni-trile）， or polyurethane.These substances are applied toa steel shaft.
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