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

1
A new electrode wear compensation method for
improving performance in 3D micro EDM milling

• 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

2
References

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  electrical discharge machining (EDM) Int. J.
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  2003 A study on the machining of high-aspect
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• 5 Masuzawa T 2000 State of the art of
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• 6 Masuzawa T and Tonshoff H K 1997
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  CIRP Ann. Manuf. Technol. 46 6218
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  wear compensation in milling EDM CIRP Ann. Manuf.
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  micro-EDM with simple shape electrode, part 1
  machining of cavities with sharp corners and
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• 15 Narasimhan J, Yu Z Y and Rajurkar K P 2005
  Tool wear compensation and path generation in
  micro and macro EDM J. Manuf. Process. 7 7582
• 16 Bigot S, Ivanov A and Popov K 2005 A study
  of the micro EDM electrode wear Proc. 1st Int.
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  and Iamikiz A 2001 Development of optimum
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• 18 Rajurkar K P and Yu Z Y 2000 3D micro-EDM
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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
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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.

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Previously Proposed Methods
VS.

• 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

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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

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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

where

• N number of compensation times

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Experimental Equipment

• Machine Setup

• Cut Shape and Tool Path

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Results
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More Results

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

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Results Summary

• UWM
• Lower material removal rate
• Higher surface roughness
• CLU
• Higher material removal rate
• Lower surface roughness

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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.

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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.

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Pop Quiz

• How long did it take to EDM the shape in the
  picture below?

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Answer

• 16 hours and 8 minutes