| 摘要 |
The present invention provides a simple method of reducing an incomplete thread portion comprising the steps of: (a) transferring a tool in the direction of the X-axis to position the tool at the point where thread cutting is to be started; (b) transferring the tool in the direction of the Z-axis in synchronization with the rotation of the main spindle to cut threads in work; (c) performing a pullout operation by deceleration in the direction of the Z-axis and acceleration in the direction of the X-axis during a predetermined acceleration/deceleration time Ta so as to retract the tool in the direction of the X-axis; and (d) withdrawing the tool in the direction of the Z-axis to return the tool to the reference point of the thread cutting cycle. In the step (c) of the pullout operation, a command is issued concurrently with the start of the acceleration/deceleration time so as to realize a pullout speed Ve in the direction of the X-axis that exceeds an allowable maximum speed Vmax to increase the acceleration in the direction of the X-axis. The speed command directing the tool to move in the direction of the X-axis is maintained at the value of zero from the elapse of command time Te until the acceleration/deceleration time Ta expires so as to maintain the actual speed of the tool in the direction of the X-axis at or below the allowable maximum speed Vmax.
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