Plasma torch cutting system

Abstract

A plasma cutting system includes a plasma cutting power supply configured to provide cutting current to a torch. A controllable gas valve regulates at least one of a flow rate and a pressure supplied to the torch. A controller is operatively connected to the power supply to control a current level, and to the gas valve to adjust a valve position. The controller is configured to receive real-time torch position information from a motion control system that controls positioning of the torch. The position information includes torch positions along a first axis and a second axis that is perpendicular to the first axis. The controller is configured to calculate respective derivatives from the torch positions along the first and second axes, and a real-time velocity magnitude of the torch from the respective derivatives, and adjust the current level and the valve position based on the calculated real-time velocity magnitude.

What is claimed is: 
     
         1 . A plasma cutting system, comprising:
 a plasma cutting power supply configured to provide a cutting current to a torch to create a plasma arc;   a controllable gas valve for regulating at least one of a flow rate and a pressure of a plasma gas supplied to the torch; and   a controller operatively connected to the plasma cutting power supply to control a current level of the cutting current, and operatively connected to the controllable gas valve to adjust a valve position of the controllable gas valve,   wherein the controller is configured to:
 receive real-time torch position information from a motion control system that controls positioning of the torch, wherein the real-time torch position information includes torch positions along a first axis and torch positions along a second axis that is perpendicular to the first axis, 
 calculate respective derivatives from the torch positions along the first axis and the torch positions along the second axis, 
 calculate a real-time velocity magnitude of the torch from the respective derivatives, and 
 adjust the current level of the cutting current and the valve position of the controllable gas valve based on the calculated real-time velocity magnitude of the torch. 
   
     
     
         2 . The plasma cutting system of  claim 1 , wherein the current level of the cutting current is reduced based on a reduction in the calculated real-time velocity magnitude of the torch. 
     
     
         3 . The plasma cutting system of  claim 1 , wherein the current level of the cutting current and the flow rate of the plasma gas supplied to the torch are reduced based on a reduction in the calculated real-time velocity magnitude of the torch, and increased based on an increase in the calculated real-time velocity magnitude of the torch. 
     
     
         4 . The plasma cutting system of  claim 1 , wherein the controller maintains kerf consistency by reducing the current level of the cutting current as the torch approaches a corner portion of a part cut from a workpiece. 
     
     
         5 . The plasma cutting system of  claim 1 , wherein the real-time torch position information includes torch positions along a third axis that is perpendicular to the first axis and the second axis, and the controller is configured to calculate the real-time velocity magnitude of the torch from a derivative of the torch positions along the third axis. 
     
     
         6 . The plasma cutting system of  claim 1 , wherein the controller is further configured to extinguish the plasma arc to end a cutting operation by reducing the current level of the cutting current while an arc length of the plasma arc is simultaneously shortened by movement of the torch toward a workpiece. 
     
     
         7 . The plasma cutting system of  claim 1 , wherein the controller reduces the current level of the cutting current and the flow rate of the plasma gas supplied to the torch as the torch approaches a corner portion of a part cut from a workpiece. 
     
     
         8 . The plasma cutting system of  claim 7 , wherein the controller increases the current level of the cutting current and the flow rate of the plasma gas supplied to the torch as the torch departs from the corner portion of the part cut from the workpiece. 
     
     
         9 . A plasma cutting system, comprising:
 a plasma cutting power supply configured to provide a cutting current to a torch to create a plasma arc;   a controllable gas valve for regulating at least one of a flow rate and a pressure of a plasma gas supplied to the torch; and   a controller operatively connected to the plasma cutting power supply to control a current level of the cutting current, and operatively connected to the controllable gas valve to adjust a valve position of the controllable gas valve,   wherein the controller is configured to:
 receive real-time torch position information from a motion control system that adjusts velocity of the torch when cutting a corner portion of a part cut from a workpiece, 
 calculate first derivatives from the real-time torch position information and determine real-time velocity magnitudes of the torch when the corner portion of the part is cut from the workpiece, and 
 maintain kerf consistency by adjusting, based on the determined real-time velocity magnitudes of the torch, the current level of the cutting current and the valve position of the controllable gas valve as the corner portion of the part is cut from the workpiece. 
   
     
     
         10 . The plasma cutting system of  claim 9 , wherein the real-time torch position information includes torch positions along a first axis and torch positions along a second axis that is perpendicular to the first axis, and the controller is configured to calculate respective first derivatives from the torch positions along the first axis and the torch positions along the second axis. 
     
     
         11 . The plasma cutting system of  claim 9 , wherein the real-time torch position information includes torch positions along a first axis, torch positions along a second axis that is perpendicular to the first axis, and torch positions along a third axis that is perpendicular to the first axis and the second axis, and the controller is configured to calculate respective first derivatives from the torch positions along the first axis, the torch positions along the second axis, and the torch positions along the third axis. 
     
     
         12 . The plasma cutting system of  claim 9 , wherein the current level of the cutting current and the flow rate of the plasma gas supplied to the torch are reduced based on a reduction in the real-time velocity magnitudes of the torch, and increased based on an increase in the real-time velocity magnitudes of the torch. 
     
     
         13 . The plasma cutting system of  claim 12 , wherein the controller reduces the current level of the cutting current and the flow rate of the plasma gas supplied to the torch as the torch approaches the corner portion of the part cut from the workpiece. 
     
     
         14 . The plasma cutting system of  claim 13 , wherein the controller increases the current level of the cutting current and the flow rate of the plasma gas supplied to the torch as the torch departs from the corner portion of the part cut from the workpiece. 
     
     
         15 . A plasma cutting method, comprising the steps of:
 providing a plasma cutting system comprising:
 a plasma cutting power supply configured to provide a cutting current to a torch to create a plasma arc; 
 a controllable gas valve for regulating at least one of a flow rate and a pressure of a plasma gas supplied to the torch; and 
 a controller operatively connected to the plasma cutting power supply to control a current level of the cutting current, and operatively connected to the controllable gas valve to adjust a valve position of the controllable gas valve; 
   receiving real-time torch position information from a motion control system that controls positioning of the torch, wherein the real-time torch position information includes torch positions along a first axis and torch positions along a second axis that is perpendicular to the first axis;   calculating, by the controller, respective derivatives from the torch positions along the first axis and the torch positions along the second axis;   calculating, by the controller, a real-time velocity magnitude of the torch from the respective derivatives; and   adjusting the current level of the cutting current and the valve position of the controllable gas valve based on the calculated real-time velocity magnitude of the torch.   
     
     
         16 . The plasma cutting method of  claim 15 , wherein the step of adjusting includes reducing the current level of the cutting current and the flow rate of the plasma gas supplied to the torch based on a reduction in the calculated real-time velocity magnitude of the torch, and increasing the current level of the cutting current and the flow rate of the plasma gas supplied to the torch based on an increase in the calculated real-time velocity magnitude of the torch. 
     
     
         17 . The plasma cutting method of  claim 15 , wherein the controller maintains kerf consistency by reducing the current level of the cutting current as the torch approaches a corner portion of a part cut from a workpiece. 
     
     
         18 . The plasma cutting method of  claim 15 , wherein the real-time torch position information includes torch positions along a third axis that is perpendicular to the first axis and the second axis, and the controller calculates the real-time velocity magnitude of the torch from a derivative of the torch positions along the third axis. 
     
     
         19 . The plasma cutting method of  claim 18 , further comprising the step of extinguishing the plasma arc to end a cutting operation by reducing the current level of the cutting current while an arc length of the plasma arc is simultaneously shortened by movement of the torch toward a workpiece. 
     
     
         20 . The plasma cutting system of  claim 15 , wherein the step of adjusting includes reducing the current level of the cutting current and the flow rate of the plasma gas supplied to the torch as the torch approaches a corner portion of a part cut from a workpiece. 
     
     
         21 . The plasma cutting system of  claim 20 , wherein the step of adjusting includes increasing the current level of the cutting current and the flow rate of the plasma gas supplied to the torch as the torch departs from the corner portion of the part cut from the workpiece.