Patent Publication Number: US-2019171185-A1

Title: Tool setting device and tool-setting method for electrochemical machining

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to electrochemical machining, and particularly to a tool setting device and tool-setting method for electrochemical machining. 
     BACKGROUND OF THE INVENTION 
     Electrochemical machining is a process in which electrochemical anode dissolution occurs to a metal workpiece in electrolyte. Before performing electrochemical machining on a workpiece, a tool setting procedure must be performed to the machining electrode. In other words, the machining electrode should be positioned with respect to the workpiece for giving the relation between the coordinates of the machining electrode and of the workpiece. According to the prior art, tool setting is achieved by operators measuring using tools for aligning the machining electrode with the workpiece. This manual tool setting procedure is quite time-consuming. Owing to its complicated steps, large tool-setting errors may occur. 
     Accordingly, the present invention provides an automatic tool setting device and tool-setting method to solve the drawbacks in the manual tool setting method according to the prior art. 
     SUMMARY 
     An objective of the present invention is to provide a tool setting device and tool-setting method for electrochemical machining. In the tool setting procedure performed according to the present invention, the location of the machining electrode can be detected automatically, and the movement of the machining electrode can be controlled as well. 
     The tool setting device disclosed in the present invention comprises a motion module, a detection circuit, and a tool setting circuit. The motion module moves a machining electrode. The detection circuit detects an electrical status of the machining electrode and outputs an electrical signal. The tool setting circuit performs calculations according to the electrical signal and gives a change status of the electrical signal. In addition, the tool setting circuit controls the motion module according to the change status of the electrical signal. 
     The tool-setting method disclosed in the present invention comprises moving a machining electrode; detecting an electrical status of the machining electrode and outputting an electrical signal; performing calculations according to the electrical signal and giving a change status of the electrical signal; and controlling the moving speed of the machining electrode according to the change status of the electrical signal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a schematic diagram of the tool setting device for electrochemical machining according to an embodiment of the present invention; 
         FIG. 2A  shows a schematic diagram of a first motion for tool setting as the tool setting device for electrochemical machining according to the present invention moves the machining electrode; 
         FIG. 2B  shows a schematic diagram of a second motion for tool setting as the tool setting device for electrochemical machining according to the present invention moves the machining electrode; 
         FIG. 2C  shows a schematic diagram of a third motion for tool setting as the tool setting device for electrochemical machining according to the present invention moves the machining electrode; 
         FIG. 3A  shows a schematic diagram of the levels of the electrical signal as the tool setting device according to a first embodiment of the present invention moves the machining electrode for performing tool setting procedure; 
         FIG. 3B  shows a schematic diagram of the changing rate of the electrical signal as the tool setting device according to a first embodiment of the present invention moves the machining electrode for performing tool setting procedure; 
         FIG. 4A  shows a schematic diagram of the levels of the electrical signal as the tool setting device according to a second embodiment of the present invention moves the machining electrode for performing tool setting procedure; and 
         FIG. 4B  shows a schematic diagram of the changing rate of the electrical signal as the tool setting device according to a second embodiment of the present invention moves the machining electrode for performing tool setting procedure. 
     
    
    
     DETAILED DESCRIPTION 
     In order to make the structure and characteristics as well as the effectiveness of the present invention to be further understood and recognized, the detailed description of the present invention is provided as follows along with embodiments and accompanying figures. 
     Please refer to  FIG. 1 , which shows a schematic diagram of the tool setting device for electrochemical machining according to an embodiment of the present invention. As shown in the figure, the tool setting device can control the machining electrode  12  to move to a workpiece  14  and thus performing tool setting procedure. An electrolyte supplies module  16  can supply electrolyte to an electrolyte output device  160  for injecting electrolyte to the surface of the workpiece  14 . A power supply circuit  18  is coupled to the machining electrode  12  and the workpiece  14  for supplying a tool-setting power source to the machining electrode  12  and the workpiece  14 . 
     Please refer again to Figure. The tool setting device comprises a motion module  10 , a tool setting circuit  20 , and a detection circuit  30 . The electrolyte supply module  16  and the power supply  18  are not limited to be disposed at the tool setting device. The machining electrode  12  is connected to the motion module  10 , which can move the machining electrode  12 . The tool setting circuit  20  is coupled to the motion module  10 . The detection circuit  30  is coupled to the machining electrode  12  and the workpiece  14  for detecting the electrical status, for example, current or voltage, of the machining electrode  12  and the workpiece  14  and generating an electrical signal correspondingly for representing the detected electrical status. In addition, the detection circuit  30  is further coupled to the tool setting circuit  20  for outputting the electrical signal to the tool setting circuit  20 . Thereby, the tool setting circuit  20  can perform calculations according to the electrical signal and thus giving the change status of the electrical signal. Then the tool setting circuit  20  can give the location of the machining electrode  12  with respect to the workpiece  14  according to the change status, and thus controlling the motion module  10  according to the change status for controlling the movement of the machining electrode  12  to perform tool setting procedure. Besides, the tool setting circuit  20  can adjust the moving speed of the machining electrode  12  automatically in the tool setting procedure and hence enhancing tool setting efficiency. Furthermore, it is not required to build a complicated database for tool setting. Consequently, the tool setting hardware can be simplified, and the setup cost can be reduced. 
     As shown in  FIG. 1 , the motion module  10  includes a moving shaft  100  and a motion control circuit  102 . The machining electrode  12  is fixed to the moving shaft  100 , which can drive to the machining electrode  12  to move. The motion control circuit  102  is coupled to the moving shaft  100  for controlling the moving shaft  100  to move. The tool setting circuit  20  controls the motion control circuit  102  of the motion module  10  for controlling the machining electrode  12  to move. The tool setting circuit  20  includes a signal control circuit  22  a signal processing circuit  24 . The signal processing circuit  24  is coupled to the detection circuit  30 . The signal control circuit  22  is coupled to the signal processing circuit  24  and the power supply circuit  18 . In the tool setting procedure, the signal control circuit  22  generates a power control signal and transmits it to the power supply circuit  18 . The power supply circuit  18  supplies the tool-setting power source to the machining electrode  12  and the workpiece  14  according to the power control signal as well as a power source to the detection circuit  30 . Given the condition of not influencing the accuracy of tool setting procedure, the level of the tool-setting power source output by the power supply circuit  18  is lower than the level of a machining power source supplied for performing electrochemical machining. Thereby, the tool setting device does not use the tool-setting power source for performing the tool setting procedure. The power consumption for the tool setting procedure can be hence reduced. 
     The detection circuit  30  detects the electrical status of the machining electrode  12  when the machining electrode  12  moves to the workpiece  14  and outputs the electrical signal to the signal processing circuit  24 . The signal processing circuit  24  receives the electrical signal, performs calculations according to the electrical signal, gives a change status of the electrical signal, and outputs a signal to the signal control circuit  22  correspondingly. The signal control circuit  22  receives the signal transmitted by the signal processing circuit  24  and acquires the change status of the electrical signal. According to the change status, the signal control circuit  22  can deduce the location of the machining electrode  12  with respect to the workpiece  14 . Then it can control the motion module  10  according to the change status and thus controlling the movement of the machining electrode  12 . Besides, it can also adjust the moving speed of the machining electrode  12 . Consequently, as the machining electrode  12  approaches the workpiece  14 , the moving speed of the machining electrode  12  can be reduced. 
     While adjusting the moving speed of the machining electrode  12 , it is not limited to adjust from a high speed to a low speed. If the initial speed of the machining electrode  12  is too low and the machining electrode  12  is not detected to approach the workpiece  14  after a specific time, such as 3 seconds, the signal control circuit  22  can control the motion module  10  to increase the moving speed of the machining electrode  12 . Accordingly, the signal control circuit  22  can control the motion module  10  automatically according to the change status of the electrical signal and the moving time of the machining electrode  12  for adjusting the moving speed of the machining electrode  12  automatically. 
     Please refer again to  FIG. 1 . The signal processing circuit  24  includes a signal conversion circuit  242 , a filter circuit  244 , and an operational circuit  246 . The signal conversion circuit  242  is coupled to the detection circuit  30 . The filter circuit  244  is coupled to the signal conversion circuit  242 . The operational circuit  246  is coupled to the filter circuit  244  and the signal control circuit  22 . The signal conversion circuit  242  receives the electrical signal output by the detection circuit  30 , converts the electrical signal from an analog format to a digital format, and outputs the digital electrical signal to the filter circuit  244 . The filter circuit  244  receives the digital electrical signal, filters the noise in the digital electrical signal, and outputs the filtered electrical signal to the operational circuit  246 . The operational circuit  246  receives the filtered electrical signal, performs calculation according to the filtered electrical signal to give the changes status of the electrical signal, and outputs the corresponding signal to the signal control circuit  22 . According to the embodiment of  FIG. 1 , if the format of the electrical signal output by the detection circuit  30  is digital, the signal processing circuit  24  may exclude the signal conversion circuit  242 . 
     Please refer again to  FIG. 1 . The tool setting circuit  20  further includes a first output circuit  26  and a second output circuit  28 . The first output circuit  26  is coupled between the motion module  10  and the signal control circuit  22 . The second output circuit  28  is coupled between the electrolyte supply module  16  and the signal control circuit  22 . When the signal control circuit  22  generates a motion control signal according to the change status of the electrical signal, the signal control circuit  22  transmits the motion control signal to the first output circuit  26 . The first output circuit  26  transmits the motion control signal to the motion control circuit  102  of the motion module  10  for controlling the motion of the moving shaft  100 . For example, the motion control signal generated by the signal control circuit  22  is a speed adjusting signal, for adjusting the moving speed of the machining electrode  12 . Alternatively, the motion control signal is a stop signal, for controlling the machining electrode  12  to stop moving. 
     In addition, the signal control circuit  22  generates an electrolyte control signal and transmits the electrolyte control signal to the second output circuit  28 . The second output circuit  28  transmits the electrolyte control signal to the electrolyte supply module  16 . According to the electrolyte control signal, the electrolyte supply module  16  supplies electrolyte to the electrolyte output device  160  for start injecting electrolyte  40  to the surface of the workpiece  14 , as shown in  FIG. 2A . 
     Please refer to  FIGS. 2A, 2B, and 2C , which show schematic diagrams of tool setting as the tool setting device for electrochemical machining according to the present invention moves the machining electrode. As shown in the figures, the machining electrode  12  can move to a first location a, a second location b, or a third location c. The machining electrode  12  starts from the first location a and moves to the workpiece  14  for performing the tool setting procedure. When the machining electrode  12  is at the first location a, the machining electrode  12  is away from the workpiece  14 . When the machining electrode  12  moves to the second location b, the machining electrode  12  contacts the electrolyte  40  on the surface of the workpiece  14 . When the machining electrode  12  moves to the third location c, the machining electrode  12  contacts the workpiece  14 . Before the tool setting device moves the machining electrode  12  to perform the tool setting procedure, the signal control circuit  22  controls the power supply circuit  18  to supply the tool-setting power source to the machining electrode  12  and the workpiece  14  and to supply the power source to the detection circuit  30 . In addition, the signal control circuit  22  controls the electrolyte supply module  16  to supply electrolyte to the electrolyte output device  160  and inject the electrolyte  40  to the surface of the workpiece  14 . 
     Before the machining electrode  12  moves from the first location a to the second location b, because the machining electrode  12  does not contact the electrolyte  40 , the machining electrode  12  and the workpiece  14  does not form a circuit loop. In other words, the tool-setting power source supplied by the power supply circuit  18  cannot flow between the machining electrode  12  and the workpiece  14 , given the environmental factors are not considered. As shown in  FIG. 3A , in the first period al, the machining electrode  12  moves from the first location a to (but not reaches) the second location b. The detection circuit  30  continues to detect the electrical status of the machining electrode  12 . Since the machining electrode  12  has not contacted the electrolyte  40 , no current flow between the machining electrode  12  and the workpiece  14 . Hence, in  FIG. 3A , the first period al is labeled with zero current. In addition, after the machining electrode  12  continues to move for 5 seconds, as shown in  FIG. 2B , the machining electrode  12  moves to the second location b and contacts the electrolyte  40  on the surface of the workpiece  14 . Thereby, the machining electrode  12 , the electrolyte  40  and the workpiece  14  form a circuit loop, boosting the current passing through the machining electrode  12 . As shown in  FIG. 3A , the detection circuit  30  detects the current passing through the machining electrode  12  at the instant a 2  of the fifth second. The current value is, for example, Amp 1 . 
     Next, the machining electrode  12  continues to move from the second location b to the third location c. Before the machining electrode  12  reaches the third location c, it continues to move to but not touch the workpiece  14 . Thereby, given the gap between the machining electrode  12  and the workpiece  14  becomes smaller, the current passing through the machining electrode  12  will increase gradually. As shown in  FIG. 3A , in the second period b 2  when the machining electrode  12  moves from the second location b to (but not reaches) the third location c, the current increase continuously from the value Amp  1  gradually. After the machining electrode  12  continues to move for three seconds, as shown in  FIG. 2C , it moves to the third location c and contacts the surface of the workpiece  14 . Hence, the machining electrode  12  contacts the workpiece  14  directly, boosting the current passing through the machining electrode  12 . As shown in  FIG. 3A , the detection circuit  30  detects the current value of Amp 2  approximately passing through the machining electrode  12  at the instant b 2  of the eighth second. Besides, the current value Amp 2  is greater than the current value Amp  1 , and the current value Amp 1  is greater than zero. 
     Then, the machining electrode  12  stops moving. Because the machining electrode  12  keeps contacting the workpiece  14 , the current passing thorough it does not change. As shown in  FIG. 3A , in the third period c 1  when the machining electrode  12  maintains contacting the workpiece  14 , the current values is held at approximately Amp 2 . 
     According to the above description, as the machining electrode  12  changes the state from not contacting the electrolyte  40  on the surface of the workpiece  14  to contacting, for example, at the instant a 2 , it will experience drastic changes in its electrical status. For example, the current value flowing through the machining electrode  12  will be increased significantly and instantaneously. Furthermore, when the machining electrode  12  contacts the electrolyte  40  and changes the state from not contacting the workpiece  14  to contacting, for example, at the instant b 2 , the electrical status of the machining electrode  12  will change apparently as well. Namely, the current passing through the machining electrode  12  will be boosted apparently at the instant. Accordingly, when the tool setting circuit  20  is notified of the apparent change in the electrical signal generated by the detection circuit  30 , it is known that the machining electrode  12  contacts the electrolyte  40  on the surface of the workpiece  14  or the machining electrode  12  has touched the workpiece  14 . 
     Based on the above description, the operational circuit  246  of the signal processing circuit  24  performs calculations according to the electrical signal to give the change status of the electrical signal. According to an embodiment of the present invention, the operational circuit  246  differentiates the electrical signal with respect to time to give the changing rate of the electrical signal. As shown in  FIG. 3B , in the first period a 1 , because the current value is maintained at zero, the changing rate of the electrical signal is zero. On the other hand, at time a 2 , the machining electrode  12  contacts the electrolyte  40 . The current value is increased instantaneously from zero to approximately Amp 1 . The changing rate is approximately, for example, CR 1 . In the second period b 2 , because the current value detected by the detection circuit  30  is increased gradually from the current value Amp 1 , the changing rate of the electrical signal is increased continuously and gradually from zero as well. Then, at time b 2 , the machining electrode  12  contacts the workpiece  14 . The current value is increased instantaneously and significantly from approximately Amp 1  (but greater than Amp 1 ) to Amp 2 . The changing rate is approximately CR 2 , which is smaller than the changing rate CR 1 . In the third period c 1 , because the current value is held at Amp 2  approximately, the changing rate of the electrical signal is zero. 
     In the tool setting procedure in which the tool setting device moves the machining electrode  12 , when the signal control circuit  22  detects the first change of the electrical signal according to the signal output by the operational circuit  246 , it is known that the machining electrode  12  has already approached the workpiece  14  and contacted the electrolyte  40  on the surface of the workpiece  14 . At this moment, the signal control circuit  22  can generate a speed adjustment signal for controlling the motion module  10  reduce the moving speed of the machining electrode  12 . Next, when the signal control circuit  22  detects the second change of the electrical signal, it is known that the machining electrode  12  has already contacted the workpiece  14 . The signal control circuit  22  generates a stop signal for controlling the motion module  20  to stop moving the machining electrode  12  and record the coordinates of the location of the machining electrode  12  for completing the tool setting procedure. According to the above description, the tool setting device can acquire the location of the machining electrode  12  with respect to the workpiece  14  according to the electrical signal generated by the detection circuit  30  and control the motion of the machining electrode  12  automatically. The motions according to the present embodiment include increasing the motion speed, reducing the motion speed, moving to the workpiece  14 , stop moving, or moving away from the workpiece  14 . 
     Moreover, the electrical signal will change due to some factors as well. Nonetheless, this change is less than the changes caused by the machining electrode  12  contacting the electrolyte  40  and the workpiece  14 . Thereby, to avoid false judgment by the tool setting device, a first threshold and a second threshold can be set to the tool setting device. The first threshold can be used for judging if the machining electrode  12  contacts the electrolyte  40 ; the second threshold can be used for judging if the machining electrode  12  contacts the workpiece  14 . The first and second thresholds can be determined according to the changing rates at time a 2  and time b 2  in  FIG. 3B . According to the present embodiment, the first threshold is higher than the second threshold. 
     Initially, when the signal control circuit  22  judges that the changing rate of the electrical signal is greater than the first threshold, it is known that the machining electrode  12  has contacted the electrolyte  40  on the surface of the workpiece  14 . If the signal control circuit  22  judges that the changing rate of the electrical signal is smaller than the first threshold, it is judged that the machining electrode  12  has contacted the electrolyte  40 , and the signal control circuit  22  continues to judge if the machining electrode  12  has contacted the electrolyte  40  according to the changing rate. As the signal control circuit  22  judges that the machining electrode  12  has contacted the electrolyte  40 , it continues to judge if the machining electrode  12  has contacted the workpiece  14  according to the changing rate. If the changing rate of the electrical signal is greater than the second threshold, the signal control circuit  22  judges that the machining electrode  12  has contacted the workpiece  14  and then controls the motion module  10  to stop moving the machining electrode  12 . According to the above description, it is appropriate for the tool setting device to perform tool setting in a humid ambient. 
     According to another embodiment of the present invention, the detection circuit  30  detects the electrical status of the machining electrode  12  and the generated corresponding electrical signal can be a resistance signal, representing the resistance status of the machining electrode  12 . As shown in  FIG. 4A , when the machining electrode  12  has not contacted the electrolyte  40  in the first period al, the machining electrode  12  and the workpiece  14  does not form a circuit loop via the electrolyte  40 , leading to infinite resistance (R∞) between the machining electrode  12  and the workpiece  14 . Next, the machining electrode  12  continues to move and contacts the electrolyte  40  at the instant a 2 . Since the machining electrode  12 , the electrolyte  40 , and the workpiece  14  form a circuit loop, the current flowing through the machining electrode  12  will be increased instantaneously, representing decrease in the resistance between the machining electrode  12  and the workpiece  14 . As shown in  FIG. 4A , the resistance becomes R 1  approximately. Then, in the second period b 2 , when the machining electrode  12  continues to move and before contacting the workpiece  14 , the resistance is maintained at R 1  approximately. At time b 2  when the machining electrode  12  contacts the workpiece  14 , because the machining electrode  12  contacts the workpiece  14  directly, the current passing through the machining electrode  12  will be increased again, meaning that the resistance between the machining electrode  12  and the workpiece  14  becomes even smaller. As shown in  FIG. 4A , the resistance becomes R 2  approximately and the resistance R 2  is smaller than the resistance R 1 . 
     Afterwards, the operational circuit  246  differentiates the electrical signal with respect to time and calculates the changing rates in resistance RR 1 , RR 2 . The differentiated electrical signal is shown in  FIG. 4B . The changing rates in resistance RR 1 , RR 2  shown in  FIG. 4B  are like the changing rates in current CR 1 , CR 2 . The difference is that the changing rates in resistance RR 1 , RR 2  shown in  FIG. 4B  are negative while the changing rates in current shown in  FIG. 3B  are positive. As described above, the signal control circuit  22  can acquire the location of the machining electrode  12  with respect to the workpiece  14  according the changing rates in resistance RR 1 , RR 2  for controlling the movement of the machining electrode  12 . 
     Accordingly, the present invention conforms to the legal requirements owing to its novelty, nonobviousness, and utility. However, the foregoing description is only embodiments of the present invention, not used to limit the scope and range of the present invention. Those equivalent changes or modifications made according to the shape, structure, feature, or spirit described in the claims of the present invention are included in the appended claims of the present invention.