Feed control method for wire cutting electrochemical discharge machining and apparatus thereof

Abstract

A feed control method for wire cutting electrochemical discharge machining is disclosed. The method determines whether a contact event has occurred using a wire electrode, based on variations in wire tension when being cut. A wire is cut with an ideal feed speed when the wire electrode is not in contact with a workpiece.

1 . A feed control method for wire cutting electrochemical discharge machining, comprising:
 performing a machining operation that makes a first speed of a servo feed of a workpiece identical to a predetermined initial velocity;   making and activating a timer to calculate the amount of time the workpiece is in contact with a wire electrode;   reading an input value;   determining whether the wire electrode is in contact with the workpiece;   performing a separation operation to separate the wire electrode from the workpiece by a predetermined distance if the wire electrode is in contact with the workpiece;   making the first speed of a servo feed identical to a second speed of a servo feed;   determining whether the amount of time of the timer has reached a predetermined non-contact time amount if the wire electrode is not in contact with the workpiece;   instructing the workpiece to proceed with the machining operation with the first speed of a servo feed if the time has not reached the predetermined non-contact time amount; and   making the first speed of a servo feed identical to a third speed of a servo feed to proceed with the machining operation if the time amount reaches the predetermined non-contact time amount.   
   
   
       2 . The feed control method for wire cutting electrochemical discharge machining as claimed in  claim 1 , wherein the second speed of a servo feed and the third speed of a servo feed are generated using a control method. 
   
   
       3 . The feed control method for wire cutting electrochemical discharge machining as claimed in  claim 2 , wherein the control method comprises a preset increment value, a preset decrement value, a lookup table, Proportional-Integral-Derivative (PID), adaptive control, neural control, or fuzzy control. 
   
   
       4 . The feed control method for wire cutting electrochemical discharge machining as claimed in  claim 2 , wherein the control method generating the second speed of a servo feed further comprises:
 recording plural time intervals whenever a contact event occurs between the workpiece, in any position, and the wire electrode;   calculating a attenuation magnification according to the time intervals;   making the second speed of a servo feed to be identical to a first value calculated by subtracting a predetermined least correction speed from the first speed of a servo feed when a second value calculated by subtracting a third value, calculated by dividing the first speed of a servo feed by the attenuation magnification, from the first speed of a servo feed is less than the predetermined least correction speed; and   making the second speed of a servo feed to be identical to the third value calculated by dividing the first speed of a servo feed by the attenuation magnification when the second value calculated by subtracting the third value, calculated by dividing the first speed of a servo feed by the attenuation magnification, from the first speed of a servo feed is not less than the predetermined least correction speed.   
   
   
       5 . The feed control method for wire cutting electrochemical discharge machining as claimed in  claim 1 , wherein the input value is a wire tension value of a determination signal. 
   
   
       6 . The feed control method for wire cutting electrochemical discharge machining as claimed in  claim 5 , wherein noise of the wire tension value is removed using a low pass filter implemented by hardware or a digital low pass filter implemented by software. 
   
   
       7 . The feed control method for wire cutting electrochemical discharge machining as claimed in  claim 5 , wherein the wire tension value is processed by filtering using an external hardware circuit and the determination signal is generated using a comparator. 
   
   
       8 . A feed control method for wire cutting electrochemical discharge machining, comprising:
 performing a machining operation, wherein an initial input value of a workpiece is set and a first speed of a servo feed of the workpiece is made to be identical to a predetermined initial velocity;   making and activating a timer to calculate the amount of time the workpiece is in contact with a wire electrode;   reading a first input value;   removing noise from the first input value to generate a second input value;   determining whether the second input value is greater than the sum of the initial input value and a boundary value;   performing a separation operation to separate the wire electrode from the workpiece by a predetermined distance if the second input value is greater than the sum of the initial input value and the boundary value;   making the first speed of a servo feed identical to a second speed of a servo feed to proceed with the machining operation;   determining whether the amount of time of the timer has reached a predetermined non-contact time amount if the second input value is not greater than the sum of the initial input value and the boundary value;   instructing the workpiece to proceed with the machining operation with the first speed of a servo feed if the time has not reached the predetermined non-contact time amount; and   making the first speed of a servo feed identical to a third speed of a servo feed to proceed with the machining operation if the time amount reaches the predetermined non-contact time amount.   
   
   
       9 . The feed control method for wire cutting electrochemical discharge machining as claimed in  claim 8 , wherein the noise is removed from the first input value to generate the second input value using a digital low pass filter. 
   
   
       10 . The feed control method for wire cutting electrochemical discharge machining as claimed in  claim 8 , wherein the noise is removed from the first input value to generate the second input value using a statistical method. 
   
   
       11 . An apparatus of feed control for wire cutting electrochemical discharge machining, comprising:
 a wire speed control mechanism;   a wire tension control mechanism;   a wire electrode, installed along the wire speed control mechanism and the wire tension control mechanism;   a wire tensiometer, installed between the wire speed control mechanism and the wire tension control mechanism for retrieving an input value from the wire electrode;   a workpiece; and   a controller, making a first speed of a servo feed of a workpiece identical to a predetermined initial velocity and reading the input value, determining whether the wire electrode is in contact with the workpiece, performing a separation operation to separate the wire electrode from the workpiece by a predetermined distance if the wire electrode is in contact with the workpiece, making the first speed of a servo feed identical to a second speed of a servo feed, determining whether the amount of time of a timer has reached a predetermined non-contact time amount if the wire electrode is not in contact with the workpiece, instructing the workpiece to proceed with the machining operation with the first speed of a servo feed if the time has not reached the predetermined non-contact time amount, and making the first speed of a servo feed identical to the third speed of a servo feed to proceed with the machining operation if the time amount reaches the predetermined non-contact time amount.   
   
   
       12 . The apparatus of feed control for wire cutting electrochemical discharge machining as claimed in  claim 11 , wherein the second speed of a servo feed and the third speed of a servo feed are generated using a control method. 
   
   
       13 . The apparatus of feed control for wire cutting electrochemical discharge machining as claimed in  claim 12 , wherein the control method comprises a preset increment value, a preset decrement value, a lookup table, Proportional-Integral-Derivative (PID), adaptive control, neural control, or fuzzy control. 
   
   
       14 . The apparatus of feed control of feed control for wire cutting electrochemical discharge machining as claimed in  claim 12 , wherein the control method further generating the second speed of a servo feed comprises:
 recording plural time intervals whenever a contact event occurs between the workpiece, in any position, and the wire electrode; calculating a attenuation magnification according to the time intervals;   making the second speed of a servo feed to be identical to a first value calculated by subtracting a predetermined least correction speed from the first speed of a servo feed when a second value calculated by subtracting a third value, calculated by dividing the first speed of a servo feed by the attenuation magnification, from the first speed of a servo feed is less than the predetermined least correction speed; and   making the second speed of a servo feed to be identical to the third value calculated by dividing the first speed of a servo feed by the attenuation magnification when the second value calculated by subtracting the third value, calculated by dividing the first speed of a servo feed by the attenuation magnification, from the first speed of a servo feed is not less than the predetermined least correction speed.   
   
   
       15 . The apparatus of feed control for wire cutting electrochemical discharge machining as claimed in  claim 11 , wherein the input value is a wire tension value of a determination signal. 
   
   
       16 . The apparatus of feed control for wire cutting electrochemical discharge machining as claimed in  claim 15 , wherein noise of the wire tension value is removed using a low pass filter implemented by hardware or a digital low pass filter implemented by software. 
   
   
       17 . The apparatus of feed control for wire cutting electrochemical discharge machining as claimed in  claim 15 , wherein the wire tension value is processed by filtering using an external hardware circuit and the determination signal is generated using a comparator. 
   
   
       18 . The of feed control for wire cutting electrochemical discharge machining as claimed in  claim 14 , further comprising a wire contact and determination circuit electrically connected and installed between the controller and the wire tensiometer, wherein the wire contact and determination circuit determines whether the electrode is in contact with the workpiece. 
   
   
       19 . A computer-readable medium encoded with computer executable instructions for performing (enabling) a feed control method for wire cutting electrochemical discharge machining, wherein the computer executable instructions comprise:
 performing a machining operation, wherein a first speed of a servo feed of a workpiece is made to be identical to a predetermined initial velocity;   making and activating a timer to calculate the amount of time the workpiece is in contact with a wire electrode; reading an input value;   determining whether the wire electrode is in contact with the workpiece;   performing a separation operation to separate the wire electrode from the workpiece by a predetermined distance if the wire electrode is in contact with the workpiece;   making the first speed of a servo feed identical to a second speed of a servo feed;   determining whether the amount of time of the timer has reached a predetermined non-contact time amount if the wire electrode is not in contact with the workpiece;   instructing the workpiece to proceed with the machining operation with the first speed of a servo feed if the time has not reached the predetermined non-contact time amount; and   making the first speed of a servo feed identical to a third speed of a servo feed to proceed with the machining operation if the time amount reaches the predetermined non-contact time amount.   
   
   
       20 . The computer-readable medium as claimed in  claim 19 , wherein the second speed of a servo feed and the third speed of a servo feed are generated using a control method. 
   
   
       21 . The computer-readable medium as claimed in  claim 20 , wherein the control method comprises a preset increment value, a preset decrement value, a lookup table, Proportional-Integral-Derivative (PID), adaptive control, neural control, or fuzzy control. 
   
   
       22 . The computer-readable medium as claimed in  claim 20 , wherein the control method generating the second speed of a servo feed further comprises:
 recording plural time intervals whenever a contact event occurs between the workpiece, in any position, and the wire electrode;   calculating a attenuation magnification according to the time intervals;   making the second speed of a servo feed to be identical to a first value calculated by subtracting a predetermined least correction speed from the first speed of a servo feed when a second value calculated by subtracting a third value, calculated by dividing the first speed of a servo feed by the attenuation magnification, from the first speed of a servo feed is less than the predetermined least correction speed; and   making the second speed of a servo feed to be identical to a third value calculated by dividing the first speed of a servo feed by the attenuation magnification when the second value calculated by subtracting a third value, calculated by dividing the first speed of a servo feed by the attenuation magnification, from the first speed of a servo feed is not less than the predetermined least correction speed.   
   
   
       23 . The computer-readable medium as claimed in  claim 19 , wherein the input value is a wire tension value of a determination signal. 
   
   
       24 . The computer-readable medium as claimed in  claim 23 , wherein noise of the wire tension value is removed using a low pass filter implemented by hardware or a digital low pass filter implemented by software. 
   
   
       25 . The computer-readable medium as claimed in  claim 23 , wherein the wire tension value is processed by filtering using an external hardware circuit and the determination signal is generated using a comparator.