Abstract: There is disclosed a device for electrical discharge machining of a work in the form of a roll for providing a satinized indented surface by satinizing operation to a predetermined surface roughness, wherein two rows of heads each mounting one or more electrodes are mounted on either sides of the rotary axis of the roll for increasing the number of heads and thereby reducing the working time. One of the rows of heads is movably mounted on a shaft on the side of roll handling operation of the roll for transiently displacing the heads in their entirety to an out-of-the-way position for solving the problem caused by roll handling and by the increase in the number of heads.

Abstract: There is disclosed a method for electrical discharge machining of a workpiece in the form of a roll by application of an electrical voltage across said workpiece and an electrode or electrodes mounted opposite to each other with a predetermined gap therebetween, and more particularly such method wherein each such electrode is formed by plural electrode segments separated from one another by insulators, and the electrical discharge operation is performed with said electrode segments in each electrode short-circuited to one another in the rough machining step and with said electrode segments insulated from one another in the finish machining step for reducing the working time.

Abstract: Disclosed is a process for subjecting the outer surface of a satinizing roll to electrical discharge machining to produce, on the roll surface, a satin-like roughened surface with a uniform roughness. With the electrical discharge machining process, a plurality of electrodes of the same shape are mounted at equal pitches on each of a plurality of head columns, and the head columns are repeatedly reciprocally fed traversely along the axis of rotation of a roll over a predetermined distance which does not cause any stepped portions on the roll surface to effect the electrical discharge machining. The feeding of the electrodes toward the surface of the roll is separately controlled for each head column. To obtain the optimum working results, the head columns are repeatedly reciprocally fed traversely over a distance equal to the electrode mounting pitch.

Abstract: Disclosed are a process and apparatus for electrical discharge machining of the outer surface of a satinizing roll to produce a satin-like roughened surface of a uniform roughness. This electrical discharge machining process produces a uniform satin-like roughened surface on the outer surface at each end of the roll, and for this purpose the process involves a step of decreasing the discharge current in proportion to decrease in the area which is to be worked by an electrode located at the roll end and thereby maintaining the flow of current per unit area at a constant value. The apparatus for performing the process comprises position detecting-means for detecting that the electrode has been moved to the roll end, and means responsive to the output signal of the position detecting means to control the off-time of current pulse which causes a discharge between the electrode and the roll.

Abstract: There is disclosed an electric discharge machining method in which the discharge working gap between an electrode and a work piece is automatically adjusted to prevent the occurrence of a streaky pattern in the surface of the work piece due to variation in the amount of machining. After a plurality of high voltage pulses have been applied for a predetermined time across the working gap, a low voltage pulse is applied across the working gap. In response to the application of the low voltage pulse, the feeding of the electrode is controlled by a pulse motor in a direction to reduce the working gap, and as soon as the discharge is started the feed control is stopped and the discharge machining is then effected in response to the application of high voltage pulses.

Abstract: Disclosed are a process and apparatus for subjecting the outer surface of a satinizing roll to electrical discharge machining to produce a satin-like roughened surface of a uniform roughness. With this electrical discharge machining process, the electrical discharge machining speed of a plurality of electrodes mounted on a plurality of head columns is held lower than a steady state working speed until the electrodes on all the head columns start discharging, and in response to the detection of the discharge of every electrode on the head columns the working speed is changed to the steady state working speed and the head columns are simultaneously moved traversely along the axis of rotation of a cylindrical work, thus preventing the occurrence of a difference in the depth of erosion or stepped portions on the surface of the work during the initial working period.