In a machine tool and a control apparatus thereof, a repetitive movement unit is configured so that the cutting tool performs one repetitive movement with respect to multiple relative rotations between the workpiece and the cutting tool and so that a rotation angle of the relative rotation between the workpiece and the cutting tool during relative movement at a second speed is smaller than a rotation angle of the relative rotation during relative movement at a first speed in one repetitive movement. This configuration limits degradation of machining efficiency when the cutting tool machines the workpiece by performing one repetitive movement with respect to multiple relative rotations between the workpiece and the cutting tool.

A machine control system for a multi-spindle machine includes a controller (42, 86). The controller is operative to reduce the risk of potentially damaging machining chip formation by controlled disengagement of a low speed clutch (18) of a transmission (14) which drives spindles (36) which rotate work pieces. Automatically selectively varying timing and duration of periods of disengagement of the low speed clutch breaks the continuity of chips to reduce the risk of developing damaging conditions as a result thereof.

A machine control system for a multi-spindle machine includes a controller (42, 86). The controller is operative to reduce the risk of potentially damaging machining chip formation by controlled disengagement of a low speed clutch (18) of a transmission (14) which drives spindles (36) which rotate work pieces. Automatically selectively varying timing and duration of periods of disengagement of the low speed clutch breaks the continuity of chips to reduce the risk of developing damaging conditions as a result thereof.

In a machine tool, under user set conditions, a cutting tool is fed in a feeding direction while the cutting tool is moved repetitively to cut a workpiece smoothly while separating chips easily. In the machine tool and a control apparatus thereof, control means is configured to set the number of rotations of relative rotation for executing machining of a workpiece, and the number of repetitions of repetitive movement during one rotation of the relative rotation in accordance with a repetitive movement frequency attributable to a cycle during which an operation instruction can be issued.

A swarf handling apparatus installed in a machining tool that performs machining operation accompanied with production of stringy swarf includes a swarf catching device. The swarf catching device includes a holder unit that holds the stringy swarf when the stringy swarf makes contact with the holder unit. The swarf catching device causes the holder unit to be floated in a region around a machining point in such a manner that the position of the holder unit is varied relative to the machining point, for catching the stringy swarf in the holder unit.

A control device includes a control part which generates a torque command based on a resultant command, which is obtained by adding a position deviation, which is the difference between a position command and the actual position of a feed shaft, to an oscillation command to control the feed shaft, and an elastic deformation amount calculation part which calculates the elastic deformation amount of a structure composed of a tool or workpiece and the feeding mechanism therefor based on the torque command. An oscillation command generation part generates the above oscillation command based on the rotation speed of the workpiece, the position command of the feed shaft, and the above elastic deformation amount.

A control device includes a position command generation part, an oscillation command generation part, and a storage part for storing machining operation conditions and servo control conditions. The oscillation command generation part includes an estimation part which estimates an oscillation amplitude and an oscillation frequency of an oscillation command based on a rotation speed of a workpiece and a position command generated by the position command generation part, and a determination part which determines whether or not the estimated oscillation frequency is an optimum value based on the machining operation conditions and the servo control conditions.

A control part of a control device includes a learning controller and a learning determination part. The learning controller performs learning control in which a correction amount of a resultant command is obtained, based on an oscillation phase obtained from an oscillation command and the resultant command, and the correction amount is added to the resultant command. The learning determination part determines whether or not the oscillation amplitude of the oscillation command is smaller than a predetermined threshold, and when the oscillation amplitude is smaller than the predetermined threshold value, the learning determination part both sets the oscillation command generated by an oscillation command generation part to zero and turns off the learning control or only turns off the learning control.

A numerical control apparatus includes: a drive unit controlling a main shaft rotating a workpiece, a first drive shaft feeding a cutting tool relatively to the workpiece along a perpendicular direction to a lead direction of a thread, and a second drive shaft feeding the cutting tool relatively to the workpiece along the lead direction; and a vibration unit superimposing, on movement of the first drive shaft, vibration having a period having a predetermined ratio with a rotation period of the main shaft, and forms a thread on the workpiece by moving the cutting tool and the workpiece relative to each other and performing cut processes on the workpiece. The numerical control apparatus includes a thread-cutting vibration adjustment unit controlling the drive unit to shift phase of the vibration with respect to phase of the main shaft by a predetermined vibration phase shift amount every time in the cut processes.

A control device for a machine tool comprises a control section controlling the relative rotation and feeding of a cutting tool and a material, performing cutting with vibration of the cutting tool relative to the material by combining a forward feed movement in the machining direction, and a return movement in the counter-machining direction. A return movement setting section sets a pulse-like signal including a command for moving a cutting tool in the machining direction and a command for the return movement. A forward feed setting section makes the cutting tool reach a change point by combining the movement in the machining direction on the basis of the return movement setting section and the forward feed movement. A pulse-like signal is formed in sine waveform with an inflection point, and a phase of the inflection point is set to a value different from a phase of the change point.