Patent ID: 9459610
Filing Date: 2016-10-04
CPC Classification: B23H,G05B

Claim Text:
1. An electric discharge machine comprising: a contact detector to detect contact between a first contact body and a second contact body based on current flowing between the first contact body and the second contact body, the first contact body corresponding to a tool electrode attached to a main spindle or a gauge head attached in place of the tool electrode, the second contact body corresponding to a workpiece or a gauge head attached to the workpiece; a numerical control device that includes a main-spindle-drive controller to control driving of the main spindle, and that recognizes a positional relation between the tool electrode and the workpiece based on a detection result of the contact detector; a noncontact-position detector to output a detection signal when a distance between the first contact body and the second contact body is equal to a preset residual distance prior to the contact between the first contact body and the second contact body, and at least one stop determiner to start monitoring a moving amount of the main spindle when the distance between the first contact body and the second contact body becomes equal to the preset residual distance, wherein the main-spindle-drive controller stops the main spindle from moving in response to the contact not being detected based on the current flowing between the first contact body and the second contact body, in combination with the monitored moving amount exceeding the preset residual distance.