Brother Kogyo Kabushiki-Kaisha

Masayuki Iwai

Katsunori Tsutsui

Yuji Ishibashi

A machine tool includes a spindle having a cutting tool for cutting a workpiece. For fault detection, a control unit of the machine tool detects a value representing a torque applied on the spindle while the spindle is stopped in a state the cutting tool is engaged with the workpiece. The control unit further compares the detected value (representing a torque) with a predetermined threshold thereby to determine that a fault has occurs. Since the detection of the value representing a torque is performed while the spindle is stopped, the detection is free from the effects of acceleration or deceleration of the spindle.

Machine tool with fault detection

Axial loads encountered during thread cutting are reduced by controlling interactions between rotation speed, axial feeding speed, feeding (threading) pitch, and feeding position. A counterload is generated by changing a feeding pitch to a corrected feeding pitch, which changes the rotation speed, while keeping the feeding speed constant; by changing the feeding speed, while compensating the rotation speed (which is derived from the feeding speed) to remain constant; by changing the rotation speed, while compensating the rotation speed deviation feedback (to allow the deviation correction to follow the rotation speed change), while keeping the feeding speed constant; by generating a function according to empirical results that controls the feeding pitch, and therefore the rotation speed, while keeping the feeding speed constant; and by combinations of these methods.

Thread cutting machine and thread cutting method

A traveling wire electric discharge machining apparatus machines a workpiece by applying periodic voltage pulses to a wire electrode while moving the wire electrode relative to the workpiece. A location on the workpiece is determined, according to a predetermined parameter. The location is before a change in machining direction of the workpiece. When the wire electrode is positioned at the determined location, a characteristic of the periodic voltage pulse is changed.

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Nagoya, Japan

Masayuki Iwai