A new electrode wear compensation method for improving performance in 3D micro EDM milling

1. Authors: Hui-Lan Yu, Ji-Jie Luan, Jian-Zhong Li, Yu-Sheng Zhang, Zu-Yuan Yu and Dong-Ming Guo Published Date: April 7th, 2010 Presented by: Mark Sydenham A new electrode wear compensation method for improving performance in 3D micro EDM milling

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3. Function of Paper • In the context of EDM micromachining: • Present electrode wear compensation methods described in previous research papers • Present new method of electrode wear compensation • Compare new method to other methods

4. Background information on the Electric Discharge Machining Process

5. Why is electrode wear compensation important? • As discussed in class, tool wear directly effects the tolerances of the part being machined. • Smaller parts with tight tolerances need to be machined with special emphasis placed on tool wear.

6. Previously Proposed Methods Linear Compensation Method (LCM) • Electrode is moved down a unit distance every unit length according to the wear rate of the electrode • Is flawed because it assumes the tool only wears on the bottom when it actually wears the sides as well Uniform Wear Method (UWM) • Tool path is designed with certain UWM rules that create a condition in which only the bottom of the tool wears • Tool plunges at the beginning of a pass to compensate for tool wear • Is flawed because plunging the tool causes unstable machining and poor surface finish VS.

7. The Design Principle of CLU Combination Linear Uniform (CLU) • Tool path follows UWM rules to ensure tool wear occurs only on the bottom of the tool • The tool is incremented down during the pass as described in the LCM • Tool wear is compensated for in the tool path using CAD/CAM software (as shown to the left) • By combining both methods and with the new assistance of a CAM program, the authors hope to more accurately account for the tool wear

8. Design Parameters • ∆Z = Tool Feed (∆Z = Lw+ Le) • Lw= The average machined depth of one layer • Le = Electrode wear length • R = volumetric relative wear ratio • Sw= cross sectional area of the cavity • Se = cross sectional area of the electrode • N = number of compensation times • where:

9. Experimental Equipment Machine Setup Cut Shape and Tool Path

10. Results

11. More Results • Notice the difference in the measurement range. • Left side range (UWM): 2.80 µm • Right side range (CLU): 2.58 µm

12. Results Summary • UWM • Lower material removal rate • Higher surface roughness • CLU • Higher material removal rate • Lower surface roughness

13. Technical advancement? • Based on the results, there is a benefit in using CLU over UWM or LCM to compensate for electrode wear in micro EDM.

14. Is this advancement practical for industrial use? • There is the potential for this study to benefit industry but this is not discussed in the research paper.

15. Which industries would benefit from this study? • Specific industries are not described in the research paper • However, the paper does mention that micro EDM is used to machine micro parts, dies and molds.

16. Pop Quiz How long did it take to EDM the shape in the picture below?

17. Answer 16 hours and 8 minutes