1. Field of the Invention
The present invention relates to a laser processing system having a function of preparing to restart a processing.
2. Description of the Related Art
In a laser processing system configured to process a workpiece by laser beam, there can be a situation in which, during a time when a controller executes a laser processing program, the execution of the laser processing program is suspended, due to an abnormality in supply of electric power or medium (especially, gas), used for laser oscillation, or an abnormality in supply of assist gas to a point to be processed, or alternatively, according to an intentional stop instruction provided by an operator or an emergency stop signal for ensuring safety. If the execution of the laser processing program is suspended during a time when the operating state of a laser processing unit (including a laser oscillator and a processing head) operating in accordance with the laser processing program is a state where a processing such as cutting or welding is actually performed on a workpiece (the state being referred to as “in course of laser processing”, in the present application), processing quality of a portion to be processed on the workpiece may be affected, depending on a restart condition of the laser processing unit (such as the presence or absence of laser oscillation, the position of the processing head, etc.) at an instant when the controller resumes the execution of the laser processing program. For example, if the laser processing unit is restarted at a position identical to a position where the program is suspended in course of laser processing, the processing head starts to move before laser power reaches a target value, which may cause defects in processing. In order to avoid such defects, if the laser processing unit is restarted at a position slightly went back along a processing path from the position where the program is suspended in course of laser processing, the already-processed portion of the workpiece is processed in a duplicative manner, which may degrade the processing quality.
A laser processing system capable of resuming, after suspending the execution of a laser processing program, the execution at a position different from a position where the execution is suspended, has been known. For example, Japanese Unexamined Patent Publication No. H05-158520 (JPH05-158520A) discloses a laser processing apparatus equipped with a function of stopping a processing by detecting abnormality when the abnormality occurs, which can automatically restart and proceed with the processing, at a position different from a position where the occurrence of abnormality is detected, or alternatively, depending on the type of abnormality, at a position identical to a position where the occurrence of abnormality is detected. JPH05-158520A describes that a restart position is specified in a processing program and, as an example, the restart position is set at a start point or endpoint of a block being executed. JPH05-158520A also describes “in a case where a block in the processing program executed at the time of stopping the processing represents an operation of moving for a positioning, the processing using laser beam 2 is not being performed, and therefore, by moving the apparatus to the endpoint (i.e., the target point of positioning) of the block and restarting the processing at that point, it is possible to prevent a processed product from being defective” and “in a case where a block in the processing program executed at the time of stopping the processing represents an operation of moving during processing subsequent to a piercing, by moving the apparatus to the start point of the block and restarting the processing at that point, it is probably possible to prevent a processed product from being defective”. Thus, the technique described in JPH05-158520A is configured to judge whether or not the operating state of the laser processing apparatus is in course of laser processing, at an instant when the program is suspended, based on statements described in the processing program.