Claims
- 1. A method for providing a high gain servo axis drive system for machine tools with improved torsional stiffness and stability, wherein said method comprises the following steps:
- providing a servo axis drive assembly comprising a base, a spindle rotatably supported with respect to said base and comprising first and second ends, means on said spindle for securing a workpiece adjacent said first end of said spindle, a spindle drive means affixed adjacent the second end of said spindle for rotatably driving said spindle, a servo motor mounted on said base and having a rotary output shaft, and means for connecting said servo output shaft with said spindle drive means, with said connecting means comprising a driving member affixed to said shaft;
- providing a first damping means attached to said spindle drive means;
- tuning said first damping means to the natural frequency of the servo axis drive assembly when not loaded with a workpiece to damp torsional oscillations of the system in unloaded condition;
- providing a second damping means attached to said driving member; and
- tuning said second damping means to the natural frequency of the servo axis drive assembly when loaded with a workpiece to damp torsional oscillation of the system in loaded condition.
- 2. The method of claim 1, wherein said second damping means is tuned to accommodate a predetermined range of loaded condition natural frequencies.
- 3. The method of claim 1, wherein said first and second damping means are each provided with one or more viscoelastic damping elements of predetermined stiffness.
- 4. The method of claim 3, wherein said first and second damping means are tuned at least in part by choosing viscoelastic damping elements having stiffness characteristics corresponding to the respective loaded and unloaded natural frequencies of the system.
- 5. The method of claim 4, wherein said second damping means is tuned to accommodate a predetermined range of loaded natural frequencies based upon workpieces to be machined.
- 6. The method of claim 1, wherein said first damping means is provided and tuned prior to tuning of the second damping means.
- 7. The method of claim 6, wherein said damping means is tuned to the natural frequency of the servo axis drive assembly when loaded with a workpiece and including the previously tuned first damping means.
- 8. A method for providing a high gain and high torsional stiffness servo axis drive system for machine tools with improved stability, said method comprising the following steps:
- providing a servo axis drive assembly with a base, a spindle rotatably supported with respect to said base along a servo axis, said spindle comprising first and second ends, means on said spindle for securing a workpiece adjacent said first end of said spindle, a spindle drive means affixed adjacent the second end of said spindle for rotatably driving said spindle, a servo motor mounted on said base and having a rotary output shaft, and a driving member for connecting said servo output shaft with said spindle drive means;
- providing a first damping means attached to said spindle drive means;
- tuning said first damping means to the natural frequency of the servo axis drive assembly when not loaded with a workpiece to damp torsional oscillations of the system in unloaded condition;
- providing a second damping means attached to said driving member and including at least one viscoelastic damping element; and
- tuning said second damping means to the natural frequency of the servo axis drive assembly including said first tuned damping means and loaded with a workpiece to damp torsional oscillation of the system in loaded condition.
- 9. The method of claim 8, wherein said second damping means is tuned to accommodate a predetermined range of loaded condition natural frequencies.
- 10. The method of claim 9, wherein said second damping means is tuned to accommodate a predetermined range of loaded natural frequencies based upon workpieces to be machined.
- 11. The method of claim 8, further comprising the step of selectively adjusting the tuning of said second damping means from time to time by substituting viscoelastic damping elements of different stiffness to accommodate different loaded conditions.
Parent Case Info
This is a divisional, of application Ser. No. 07/924,223, filed Aug. 3, 1992 now U.S. Pat. No. 5,205,190 issued on Apr. 27, 1993.
US Referenced Citations (26)
Foreign Referenced Citations (2)
Number |
Date |
Country |
177333 |
Aug 1987 |
JPX |
2169035 |
Jul 1986 |
GBX |
Non-Patent Literature Citations (3)
Entry |
Shock and Vibration Handbook, Edited by Harris and Crede, Second Edition, McGraw-Hill Book Company, 1976, various pages. |
"Eliminating Istabilities in Motion Control Systems Caused by Torsional Resonance", by Gregory J. Schneider, Motion Fourth Quarter, 1985, pp. 4-8. |
"Taming Resonance in Servos", by Gregory J. Schneider., Machine Design, Feb. 7, 1985, pp. 73-76. |
Divisions (1)
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Number |
Date |
Country |
Parent |
924223 |
Aug 1992 |
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