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In rotogravure printing the doctor blade (from ''ductor blade'') removes the excess ink from the smooth non-engraved portions of the image carrier and the land areas of the cell walls. Doctor blades are also used in other printing and coating processes, such as flexo and pad printing for the same function. It is believed that the name derives from the blades used in flatbed letterpress equipment for blades used to wipe ductor rolls, and "ductor" became doctor.〔 Given that a blade is necessary to remove the excess ink from a cylinder which is continuously running, the blade/cylinder combination is designed such that it is (chiefly) the blade which wears away, not the cylinder. The doctor blade is cheap and disposable and the gravure cylinder or flexo anilox is relatively expensive. Typical materials for the blade are steel or plastic:〔The Complete Book on Printing Technology By Niir Board〕 gravure cylinders are normally hard-chrome plated〔Handbook of Pulping and Papermaking By Christopher J. Biermann〕 and aniloxes may be chromed or ceramic.〔Leach, R.H.; Pierce, R.J., eds. (2007), The Printing Ink Manual (5th ed.), Dordrecht, The Netherlands: Springer, ISBN 978-0-948905-81-0〕 Important process variables in gravure coating & printing are the rotational position at which the blade wipes the cylinder; the angle that the blade makes with the tangent to the cylinder at the contact point; and the pressure applied to the blade.〔Printed Organic and Molecular Electronics edited by Daniel Gamota p288〕 Fine adjustment of in-and-out position, independently on left and right, must also be possible, in order to compensate for any misalignment between blade geometry and cylinder axis. These requirements are fulfilled by a doctor blade assembly which includes a doctor blade holder. Of necessity, the doctor blade must be easy and quick to replace. On many machines, the doctor blade holder is easily removable from the machine and the replacement of a doctor blade is done by removing the blade holder from the machine; discarding the old blade; inserting the new blade; and then replacing the blade holder + new blade in the machine. In order to keep the wear pattern as even as possible, and to help prevent any particles in the angle between blade and cylinder, all except the smallest machines use oscillating doctor blades. The entire doctor blade assembly oscillates from side to side.〔Printed Organic and Molecular Electronics edited by Daniel Gamota p286〕 The oscillation; flexibility of the blade; and the various possible misalignments and problems due of lack of stiffness may result in the failure to achieve the desired angle of contact between the blade and the cylinder, or at least a failure to consistently achieve this desired angle. ==References== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Doctor blade」の詳細全文を読む スポンサード リンク
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