Methods and systems for monitoring and controlling electroerosion

Abstract

A method for monitoring machining in an electroerosion assembly having a power supply and an electrode arranged across a gap from a workpiece, includes measuring a voltage at a point in a voltage waveform after a time delay t d of one half of a pulse width of the voltage waveform. The measurements are repeated for multiple pulses of the voltage waveform to obtain multiple voltages, each of the voltages corresponding to a point in respective pulses. The voltages are averaged to obtain an average voltage, which is compared with at least one threshold voltage, to determine whether the machining is in control. A control signal is generated if the comparison indicates that the process is not in control, the control signal being configured to regulate an operating parameter of the power supply, and the control signal is supplied to the power supply, if generated.

1 . A method for monitoring machining in an electroerosion assembly having a power supply and at least one electrode arranged across a gap from a workpiece, the electrode being energized by the power supply that applies a potential difference ΔV between the electrode and the workpiece during a plurality of pulse-on periods, said method comprising:
 measuring a voltage at a point in a voltage waveform for the electroerosion assembly after a specified time delay t d  of at least about one half of a pulse width Δτ of the voltage waveform; 
 repeating the measurement for a plurality of pulses of the voltage waveform to obtain a plurality of voltages, each of the voltages corresponding to a point in respective ones of the pulses, wherein the pulses correspond to a window; 
 comparing each of the voltages with at least one threshold voltage V th  to classify each of the pulses as a normal or an abnormal discharge pulse; 
 generating at least one control signal if the comparison indicates that at least a predetermined number of abnormal discharge pulses are present in the window, the at least one control signal being configured to regulate at least one operating parameter of the power supply; and 
 supplying the at least one control signal to the power supply, if the control signal has been generated. 
 
     
     
         2 . The method of  claim 1 , wherein the window is a flying window, said method further comprising selecting a window size. 
     
     
         3 . The method of  claim 2 , wherein the electroerosion assembly is a pulsed electroerosion assembly, wherein said measuring begins at the time delay interval t d  after a pulse-on state and ends at a pulse-off state, and wherein the at least one control signal is an instruction to the power supply selected from the group consisting of an instruction to increase a duration of at least one of a plurality of pulse-off periods, an instruction to decrease a duration of at least one of the pulse-on periods, an instruction to modify a peak current density provided to the electroerosion assembly, an instruction to turn off the power supply and combinations thereof. 
     
     
         4 . An electroerosion assembly comprising:
 at least one electrode configured to machine a workpiece across a gap upon application of a potential difference ΔV across said electrode and the workpiece;   a power supply configured to energize said electrode; and   a controller configured to:
 measure a voltage at a point in a voltage waveform for the electroerosion assembly after a specified time delay t d  of at least about one half of a pulse width Δτ of the voltage waveform, 
 repeat the measurement for a plurality of pulses of the voltage waveform to obtain a plurality of voltages, each of the voltages corresponding to a point in respective ones of the pulses, 
 compare the voltages with at least one threshold voltage V th , to determine whether a machining process is in control, 
 generate at least one control signal if the comparison indicates that the machining process is not in control, the at least one control signal being configured to regulate at least one operating parameter of said power supply, and 
 supply the at least one control signal to said power supply, if the control signal has been generated. 
   
     
     
         5 . The electroerosion assembly of  claim 4 , wherein the plurality of pulses corresponds to a flying window, and wherein the averaging comprises a point-by-point averaging. 
     
     
         6 . The electroerosion assembly of  claim 4 , wherein said controller is further configured to determine that the machining process is not in control if the average voltage is less than the at least one threshold voltage V th . 
     
     
         7 . The electroerosion assembly of  claim 4 , wherein said controller is configured to compare the voltages by:
 averaging the voltages to obtain an average voltage; and   comparing the average voltage with at least one threshold voltage V threshold , to determine whether the machining process is in control.   
     
     
         8 . The electroerosion assembly of claim  15 , wherein said controller is configured to compare each of the voltages with at least one threshold voltage V th  to classify each of the pulses as a normal or an abnormal discharge pulse, and wherein said controller is configured to generate at least one control signal if the comparison indicates that a predetermined number of abnormal pulses are present in the window. 
     
     
         9 . A method for monitoring a machining process in an electroerosion assembly having a power supply and at least one electrode arranged across a gap from a workpiece, the electrode being energized by the power supply that applies a potential difference ΔV between the electrode and the workpiece during a plurality of pulse-on periods, said method comprising:
 measuring a voltage at a point in a pulse of a voltage waveform for the electroerosion assembly after a specified time delay t d  from a pulse-on state of the pulse, the time delay t d  being at least about one half of a pulse width Δτ of the voltage waveform; 
 comparing the measured voltage with at least one threshold voltage V threshold , to determine whether the machining process is in control; 
 generating at least one control signal if the comparison indicates that the process is not in control, the at least one control signal being configured to regulate at least one operating parameter of the power supply; and 
 supplying the at least one control signal to the power supply, if the control signal has been generated.