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Vibration Analysis in High Speed Rough and Finish Milling Hardened Steel. Presented By: Peter Cannon October 27, 2004. Author: C.K. Toh Published: Journal of Sound and Vibration (accepted 29 September 2003). Agenda. Function.

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Vibration analysis in high speed rough and finish milling hardened steel l.jpg
Vibration Analysis in High Speed Rough and Finish Milling Hardened Steel

Presented By: Peter Cannon

October 27, 2004

Author: C.K. Toh

Published: Journal of Sound and Vibration (accepted 29 September 2003)


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Agenda Hardened Steel


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Function Hardened Steel

  • Characterize chatter vibration effects in high speed milling (HSM)

  • Compare chatter effects for

    • Different cutter path orientations

    • Different cutter conditions

    • Different milling directions (up and down)

    • Different milling processes (rough and finish)


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Importance Hardened Steel

  • Chatter and vibration affect

    • Dimensional accuracy

    • Surface finish

    • Tool Life

    • Spindle Life

  • Chatter creates waste

  • Suggestions needed for optimal cutter orientation in HSM


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References Hardened Steel


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References Hardened Steel


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Class Relevance Hardened Steel

  • The paper investigates relationship between terms introduced in class

    • Chatter

    • Down Milling

    • Up Milling

    • Profiling

  • Paper recommends guidelines for High Speed Milling to improve tool life and operation efficiency


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Design Definition Hardened Steel

  • Cutter experiences dynamic forces in 3 dimensions (x, y, z)

  • Dynamic force signatures for each dimension are collected, and a fast Fourier transform is performed to create a frequency spectrum

  • Frequency patterns can indicate presence of chatter


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Parameters Hardened Steel

  • Down Milling – cutting speed in same direction as part feed (Thick to thin chips)

  • Up Milling – cutting speed in opposite direction of part feed (Thin to thick chips)

  • Rough Milling

    • 10,000 RPM

    • Fpt = .0667 mm/tooth

    • Axial Depth = 20, 25, 10 mm

    • Radial Depth = .5 mm

  • Finish Milling

    • 3,250 RPM

    • Fpt = .1 mm/tooth

    • Axial Depth = .5 mm

    • Radial Depth = .5 mm

  • New Cutter – Flank wear land width < .05 mm

  • Worn Cutter – Flank wear land width ≥ .3 mm


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Design Principle Hardened Steel

  • The design principle here is procedural

  • Results will not affect cutter, spindle, or machine design

  • Results will affect design of milling operation, order and aggressiveness of cut, and orientation of cutter


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Experimental Equipment Hardened Steel

  • Material

    • Hardened AISI H13 hot worked steel (HRC 52)

    • HRC 52

    • Face milled and ground as prep

  • Cutters

    • Tungsten Carbide

    • 6-Flute

    • 10 mm Diameter

    • 45° helix angle

    • -14° radial rake angle

    • (Al,Ti)N monolayer coating 2.5 µm thick

    • Runout < 10 µm

  • Vertical prismatic high speed mill

  • Three-component piezoelectric platform dynamometer

  • Four channel O-scope


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Experimental Procedure Hardened Steel

Rough Milling

  • Fy component analyzed for chatter effects


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Experimental Setup Hardened Steel

Finish Milling


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Results Hardened Steel

Rough Milling (New Cutter)

Known Frequencies

  • Tooth Passing Frequency 1000 Hz

  • Harmonics 2000, 3000 Hz

  • Spindle Frequency 166.67 Hz

    Chatter should show between 2000 and 5000 Hz


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Results Hardened Steel

Rough Milling (Worn Cutter)

Known Frequencies

  • Tooth Passing Frequency 1000 Hz

  • Harmonics 2000, 3000 Hz

  • Spindle Frequency 166.67 Hz

    Observations

  • Virtually all amplitudes are increased

  • Up milling appears to have little or no vibrations compared to down


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Results Hardened Steel

Down Finish Milling (New Cutter)

Known Frequencies

  • Tooth ≈ 325 Hz

  • Harmonics

    Observations

  • Upward has higher amplitudes

  • No significant chatter

  • Harmonics with significant amplitudes (Fig. D) indicate cutter deflections (possibly from runout) create low tool life


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Results Hardened Steel

Down Finish Milling (Worn Cutter)

Known Frequencies

  • Tooth ≈ 325 Hz

  • Harmonics

    Observations

  • Figure A and B show chatter between 2000 and 3000 Hz


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Results Hardened Steel

Up Finish Milling (New Cutter)

Known Frequencies

  • Tooth ≈ 325 Hz

  • Harmonics

    Observations

  • Chatter between 2000 and 3000 Hz in Figure C

  • This beating effect could cause chipping on clearance face of cutter


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Results Hardened Steel

Up Finish Milling (Worn Cutter)

Known Frequencies

  • Tooth ≈ 325 Hz

  • Harmonics

    Observations

  • Figures A and B high amplitudes on harmonics

  • No significant chatter


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Conclusions Hardened Steel

  • For Rough Milling

    • Lower amplitudes and less chatter when up milling

  • Finish Milling

    • Upward cutter path orientation increased tendency for chipping

    • Downward cutter path promoted longer tool life

  • Chatter most predominant when down milling with a vertical downward orientation and a worn cutter

  • Vertical upward (up or down milling) showed no chatter even with worn cutter


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Practical Industrial Use Hardened Steel

  • Knowing orientations and conditions that lead to chatter can help machinists plan around it

  • Reducing the amount of chatter will help extend tool life and create more dimensionally accurate parts with better surface finish


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Technical Advancement Hardened Steel

  • Questionable – The interpretation of the frequency signatures is highly subjective

  • Some statements made in the explanation of the frequency charts do not match the charts

  • Asking an experienced machinist would likely produce at least as much information regarding when chatter occurs and how to avoid it


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Industries Impacted Hardened Steel

  • High Speed Milling industry

  • Mould and die making


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Questions Hardened Steel