a numerical controller is capable of foreseeing the occurrence of interference during operation of a machine and securely preventing the interference . an advanced position calculating section determines advanced time for the next interference check , based on an end time point of an interference check by an interference checking device and the sum of a time required for the interference check , a time required for communication , a time required for decelerating and stopping a movable part , and a predetermined float . if an interference checking device detects interference , the interference checking device delivers an axis stop signal the movable part .