Plasma detector and laser beam machine with plasma detector

A laser beam machine comprising:

• a torch for radiating laser beam on a workpiece;
• trace control means for holding a gap length between said torch and said workpiece;
• spatter detecting means for detecting whether or not spatter generates from said workpiece
• a plasma detector for detecting whether or not plasma generates between said torch and said workpiece;
• said trace control means having:
• a nozzle at a top end of said torch for introducing said laser beam to said workpiece, said nozzle being an electrode;
• a trace voltage detecting means for detecting voltage of said nozzle as trace voltage;
• and
• a gap length control means for controlling said gap length between said torch and said workpiece based on said trace voltage of said nozzle which has been detected by said trace voltage detecting means;
• said spatter detecting means having:
• a voltage slope computing means for computing voltage slope of said trace voltage of said nozzle detected by said trace voltage detecting means with respect to time;
• and
• a spatter detection determining means for determining whether or not said spatter generating from said workpiece due to said laser beam was detected based on said voltage slope computed by said voltage slope computing means, and for outputting a spatter determination result;
• said plasma detector having:
• a voltage fluctuating section computing means for computing a section where said voltage slope computed by said voltage slope computing means of said spatter detecting means exceeds a predetermined value as a voltage fluctuating section where said trace voltage fluctuates;
• a voltage fluctuating time integrating means for integrating voltage fluctuating time corresponding to said voltage fluctuating section computed by said voltage fluctuating section computing means as voltage fluctuating integrated time;
• a voltage fluctuation occurrence rate computing means for computing a voltage fluctuation occurrence rate for time based on said voltage fluctuation integrated time integrated by said voltage fluctuating time integrating means;
• and
• a plasma detection determining means for determining whether or not said plasma was detected based on said voltage fluctuation occurrence rate computed, and for outputting a plasma determination result;
• a movement driving means for moving and driving said torch at a predetermined feeding speed;
• a machining execution means for executing machining on said workpiece with said predetermined feeding speed and an output of laser beam radiation which are instructed by a machining program;
• and
• a machining condition changing means for changing said feeding speed and/or said output of laser beam radiation which is instructed by said machining program when said plasma detection determining means outputs said plasma determination result that said plasma was detected;
• whereby said machining execution means executes machining on said workpiece with said changed feeding speed and/or with said changed output of laser beam radiation which was changed by said machining condition changing means.

A plasma detector of a laser beam machine, said laser beam machine having a torch for radiating laser beam on a workpiece, a trace control unit for holding a gap length between said torch and a workpiece, said plasma detector for detecting whether or not plasma generates between said torch and said workpiece, said trace control unit having:

• a nozzle at a top end of said torch for introducing said laser beam to said and an electrode;
• and a trace voltage detecting unit for detecting voltage of said nozzle as trace voltage, said plasma detector comprising:
• a gap length control unit for controlling said gap length between said torch and said workpiece based on said trace voltage of said nozzle which has been detected by said trace voltage detecting means;
• a voltage fluctuating section detecting unit for detecting a voltage fluctuating section where said trace voltage fluctuates as detected by said trace voltage detecting unit;
• a voltage fluctuating time integrating unit for integrating voltage fluctuating time corresponding to said voltage fluctuating section detected by said voltage fluctuating section detecting unit as voltage fluctuating integrated time;
• a voltage fluctuation occurrence rate computing unit for computing a voltage fluctuation occurrence rate for time based on said voltage fluctuation integrated time integrated by said voltage fluctuating time integrating unit;
• and
• a plasma detection determining unit for determining whether or not said plasma was detected based on said voltage fluctuation occurrence rate computed by said voltage fluctuation occurrence rate computing unit, and for outputting a determination result;
• whereby said plasma detector determines whether or not plasma generates between said torch and said workpiece based on said trace voltage detected by said trace control unit.

A laser beam machine comprising:

• a torch for radiating a laser beam on a workpiece;
• a trace control unit for holding a gap length between said torch and a workpiece;
• a spatter detecting unit for detecting whether or not spatter generates from said workpiece;
• a plasma detector for detecting whether or not plasma generates between said torch and said workpiece;
• said trace control unit having:
• a nozzle at a top end of said torch for introducing said laser beam to said workpiece, said nozzle being an electrode;
• a trace voltage detecting unit for detecting voltage of said nozzle as trace voltage;
• and
• a gap length control unit for controlling said gap length between said torch and said workpiece based on said trace voltage of said nozzle which has been detected by said trace voltage detecting means;
• said spatter detecting unit having:
• a voltage slope computing unit for computing voltage slope of said trace voltage of said nozzle detected by said trace voltage detecting unit with respect to time;
• and
• a spatter detection determining unit for determining whether or not said spatter generating from said workpiece due to said laser beam was detected based on said voltage slope computed by said voltage slope computing unit, and for outputting a spatter determination result;
• said plasma detector having:
• a voltage fluctuating section computing unit for computing a section where said voltage slope computed by said voltage slope computing unit of said spatter detecting unit exceeds a predetermined value as a voltage fluctuating section where said trace voltage fluctuates;
• a voltage fluctuating time integrating unit for integrating voltage fluctuating time corresponding to said voltage fluctuating section computed by said voltage fluctuating section computing unit as voltage fluctuating integrated time;
• a voltage fluctuation occurrence rate computing unit for computing a voltage fluctuation occurrence rate for time based on said voltage fluctuation integrated time integrated by said voltage fluctuating time integrating unit;
• and
• a plasma detection determining unit for determining whether or not said plasma was detected based on said voltage fluctuation occurrence rate computed, and for outputting a plasma determination result;
• a movement driving unit for moving and driving said torch at a predetermined feeding speed;
• a machining execution unit for executing machining on said workpiece with said predetermined feeding speed and an output of laser beam radiation which are instructed by a machining program;
• and
• a machining condition changing unit for decreasing said feeding speed and/or said output of laser beam radiation which is instructed by said machining program when said plasma detection determining unit of said plasma detector outputs said plasma determination result that said plasma was detected;
• whereby said machining execution unit executes machining on said workpiece with said decreased feeding speed and/or with said decreased output of laser beam radiation which was changed by said machining condition changing unit.