A lathe capable of shortening a cycle time of workpiece machining. A lathe includes a first spindle, a second spindle opposite the first spindle, a tool post on which a cut-off tool is provided, and a control unit which controls rotation of the first and the second spindles and further controls relative movement of the first and the second spindles and the tool post to cut-off the workpiece. The control unit adds a rotation speed fluctuation to a rotation speed of the first spindle after rotating the first spindle and the second spindle synchronously and detects a rotation speed of the second spindle. The control unit determines that the workpiece is normally cut-off upon determining that a detected fluctuation in the rotation speed of the second spindle is within a predetermined range.

A servomotor controller includes a connection mechanism configured to transfer power of a servomotor to a driven body; a motor control unit configured to control the servomotor using a position command value; a first force estimation unit configured to estimate a first force estimated value which is a drive force acting on the driven body at a connecting unit with the connection mechanism; a second force estimation unit configured to estimate a second force estimated value serving as a fixed value; a selection unit configured to compare an absolute value of the first force estimated value and an absolute value of the second force estimated value to output the first or second force estimated value having the larger absolute value; and a compensation amount generation unit configured to generate a compensation amount for compensating the position command value on the basis of the first or second force estimated value.

A servomotor controller includes a connection mechanism configured to transfer power of a servomotor to a driven body; a motor control unit configured to control the servomotor using a position command value; a first force estimation unit configured to estimate a first force estimated value which is a drive force acting on the driven body at a connecting unit with the connection mechanism; a second force estimation unit configured to estimate a second force estimated value serving as a fixed value; a selection unit configured to compare an absolute value of the first force estimated value and an absolute value of the second force estimated value to output the first or second force estimated value having the larger absolute value; and a compensation amount generation unit configured to generate a compensation amount for compensating the position command value on the basis of the first or second force estimated value.