FEED CONTROL METHOD FOR WIRE CUTTING ELECTROCHEMICAL DISCHARGE MACHINING AND APPARATUS THEREOF

• US 20120292292A1
• Filed: 07/26/2012
• Published: 11/22/2012
• Est. Priority Date: 08/14/2008
• Status: Active Grant

• Current Assignee: Industrial Technology Research Institute
• Original Assignee: Industrial Technology Research Institute
• Inventors: Lin, Jui-Kuan, Lee, Hsiang-Kuo, Lin, Yang-Xin, Su, Hsin-Chuan
• Granted Patent: US 8,663,449 B2
• Time in Patent Office: Days
• US Class Current: 219/69.12
• CPC Class Codes: B23H 5/02 Electrical discharge machining combined with electrochemical machining
• CPC Class Codes: B23H 7/02 Wire-cutting
• CPC Class Codes: B23H 7/18 for maintaining or controlling the desired spacing between electrode and workpiece
• CPC Class Codes: B23H 7/20 for programme-control, e.g. adaptive programme-control systems in general G05B19/00

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.

Claims

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 during the workpiece is not in contact with a wire electrode;

defining an initial input value;

reading a wire tension value of the wire electrode;

generating a new wire tension value by filtering the wire tension value;

determining whether the wire electrode is in contact with the workpiece by determining whether the new wire tension value is greater than a sum of the initial input value and a boundary value, wherein the new wire tension value is greater than the sum of the initial input value and the boundary value when 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 the servo feed identical to a second speed of the servo feed after the separation operation is finished, wherein the second speed of the servo feed is lower than the predetermined initial velocity;

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 the servo feed if the time has not reached the predetermined non-contact time amount; and

making the first speed of the servo feed identical to a third speed of the 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 the servo feed and the third speed of the 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 the 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 the servo feed to be identical to a first value calculated by subtracting a predetermined least correction speed from the first speed of the servo feed when a second value calculated by subtracting a third value, calculated by dividing the first speed of the servo feed by the attenuation magnification, from the first speed of the servo feed is less than the predetermined least correction speed; and

making the second speed of the servo feed to be identical to the third value calculated by dividing the first speed of the servo feed by the attenuation magnification when the second value calculated by subtracting the third value, calculated by dividing the first speed of the servo feed by the attenuation magnification, from the first speed of the 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 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.

6. The feed control method for wire cutting electrochemical discharge machining as claimed in claim 1, wherein the wire tension value is processed by filtering using an external hardware circuit and the determination signal is generated using a comparator.

7. The feed control method for wire cutting electrochemical discharge machining as claimed in claim 1, wherein the third speed of the servo feed is higher than the predetermined initial velocity.

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 the servo feed identical to a second speed of the 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 the servo feed if the time has not reached the predetermined non-contact time amount; and

making the first speed of the servo feed identical to a third speed of the 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. 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 during the workpiece is not in contact with a wire electrode;

reading an input value, wherein the input value has two states indicating the wire electrode is in contact with the workpiece and the wire electrode is not in contact with the workpiece respectively;

determining whether the wire electrode is in contact with the workpiece according to the state of the input value;

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 after the separation operation is finished, wherein the second speed of a servo feed is lower than the first 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.