Vibration assisted machining system with stacked actuators

• US 7,687,975 B2
• Filed: 03/27/2007
• Issued: 03/30/2010
• Est. Priority Date: 03/27/2007
• Status: Active Grant

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Ethington, Jon, Lee, Tzehin
• Primary Examiner(s): Benson; Walter
• Assistant Examiner(s): ROSENAU, DEREK JOHN
• Application Number:
  US11/691,844
• Publication Number:
  US 20080238255A1
• Time in Patent Office: 1,099 Days
• Field of Search: 31032301-32321, 310/328
• US Class Current: 310/323.18
• CPC Class Codes: B23B 2260/102 Magnetostrictive elements
• CPC Class Codes: B23B 2260/108 Piezoelectric elements
• CPC Class Codes: B23B 2265/16 Elliptical
• CPC Class Codes: B23B 29/125 Vibratory toolholders
• CPC Class Codes: B23P 25/00 Auxiliary treatment of workpieces, before or during machining operations, to facilitate the action of the tool or the attainment of a desired final condition of the work, e.g. relief of internal stress
• CPC Class Codes: B23Q 1/34 Relative movement obtained by use of deformable elements, e.g. piezoelectric, magnetostrictive, elastic or thermally-dilatable elements sensitive elements capable of producing movement or displacement for purposes not limited to measurement G12B1/00
• CPC Class Codes: B24B 1/04 subjecting the grinding or polishing tools, the abrading or polishing medium or work to vibration, e.g. grinding with ultrasonic frequency polishing or abrading surfaces on work by means of tumbling apparatus B24B31/00, involving oscillating or vibrating containers B24B31/06; superfinishing surfaces on work, e.g. by means of abrading blocks reciprocating with high frequency, B24B35/00
• CPC Class Codes: B24B 13/00 Machines or devices designed for grinding or polishing optical surfaces on lenses or surfaces of similar shape on other work; Accessories therefor edging optical work, e.g. lenses, prisms B24B9/14

Abstract

A vibration assisted machining (VAM) system, including: a frame; a vibration element mechanically coupled to the frame; a cutting tool holder connected to the vibration element; and a workpiece holder coupled to the frame. The vibration element includes a first piezoelectric (PZT) actuator and a second PZT actuator, which are adapted to generate a substantially elliptical tool path in a vibration plane of the VAM system. The VAM system also includes a third PZT actuator coupled between the frame and either the vibration element or the workpiece holder. This third PZT actuator is coupled to the frame such that its polarization axis is substantially in the vibration plane and substantially perpendicular to the feed direction of the VAM system.

Claims

1. A vibration assisted machining (VAM) system, comprising:

a frame;

a vibration element mechanically coupled to the frame, the vibration element including a first piezoelectric (PZT) actuator and a second PZT actuator adapted to generate a substantially elliptical tool path in a vibration plane of the VAM system;

a cutting tool holder connected to the vibration element;

a workpiece holder coupled to the frame;

a motion stage configured to position at least one of the cutting tool holder and the workpiece holder; and

a further vibration element comprising a third PZT actuator coupled between the frame and one of;

the vibration element;

or

the workpiece holder;

wherein the third PZT actuator is independent of the motion stage and is coupled to the frame such that a polarization axis of the third PZT actuator is substantially in the vibration plane and substantially perpendicular to a feed direction of the VAM system.

2. A VAM system according to claim 1, wherein:

the first PZT actuator and the second PZT actuator of the vibration element are mounted in a side-by-side configuration;

the vibration element further includes a T-linkage coupling the first PZT actuator and the second PZT actuator to the cutting tool holder; and

the first PZT actuator and the second PZT actuator are coupled to the frame such that polarization axes of the first PZT actuator and the second PZT actuator are substantially parallel to the polarization axis of the third PZT actuator.

3. A VAM system according to claim 1, wherein:

the vibration element further includes a cross-void flexure coupling the first PZT actuator and the second PZT actuator to the cutting tool holder;

the first PZT actuator and the second PZT actuator of the vibration element are mounted in an orthogonal configuration; and

the first PZT actuator and the second PZT actuator are coupled to the frame such that;

a polarization axis of the first PZT actuator is substantially parallel to the polarization axis of the third PZT actuator; and

a polarization axis of the second PZT actuator is substantially perpendicular to the polarization axis of the third PZT actuator.

4. A VAM system according to claim 1, wherein:

the vibration element further includes a two-dimensional transverse vibration beam that has two nodes and an end section that is not between the two nodes, the two-dimensional transverse vibration beam is coupled to;

the frame at the two nodes; and

the cutting tool holder at the end section; and

the first PZT actuator and the second PZT actuator of the vibration element are coupled to the two-dimensional transverse vibration beam in an orthogonal configuration at a center point between the two nodes such that;

a polarization axis of the first PZT actuator is substantially parallel to the polarization axis of the third PZT actuator; and

a polarization axis of the second PZT actuator is substantially perpendicular to the polarization axis of the third PZT actuator.

5. A VAM system according to claim 1, further comprising:

drive circuitry electrically coupled to the vibration element and the third PZT actuator, the drive circuitry adapted to provide a first drive signal for driving the first PZT actuator, a second drive signal for driving the second PZT actuator, and a third drive signal for driving the third PZT actuator;

wherein;

the first drive signal has a fundamental frequency and a first stroke amplitude;

the second drive signal has the fundamental frequency and a second stroke amplitude;

the first stroke amplitude, the second stroke amplitude, and a relative phase of the first drive signal and the second drive signal are selected such that a tip of a cutting tool mounted in the cutting tool holder follows the substantially elliptical tool path in the vibration plane relative to the vibration element; and

the third drive signal has a perturbation frequency approximately equal to N times the fundamental frequency, where N is an integer greater than 1, and a perturbation amplitude less than a lesser of the first stroke amplitude and the second stroke amplitude.

6. A VAM system according to claim 1, further comprising bias circuitry electrically coupled to the third PZT actuator, the bias circuitry adapted to provide a bias signal to dynamically control a distance between the vibration element and the workpiece holder.

7. A VAM system according to claim 1, wherein the motion stage comprises:

a feed stage coupled between the frame and the vibration element to translate the vibration element in the feed direction of the VAM system; and

a step stage to step the cutting tool holder relative to the workpiece holder in a direction substantially perpendicular to the feed direction and substantially normal to the vibration plane of the VAM system at an end of a feed line, the step stage being coupled between the frame and one of;

the vibration element;

or

the workpiece holder.

8. A VAM system according to claim 1, wherein the motion stage comprises:

a feed stage coupled between the frame and the workpiece holder to translate the workpiece holder in a direction opposite to the feed direction of the VAM system; and

a step stage to step the cutting tool holder relative to the workpiece holder in a direction substantially perpendicular to the feed direction and substantially normal to the vibration plane of the VAM system at an end of a feed line, the step stage being coupled between the frame and one of;

the vibration element;

or

the workpiece holder.

9. A VAM system according to claim 1, further comprising a fourth PZT actuator coupled between the frame and one of:

the vibration element;

or

the workpiece holder.

10. A VAM system according to claim 9, further comprising:

drive circuitry electrically coupled to the vibration element, the third PZT actuator, and the fourth PZT actuator, the drive circuitry adapted to provide a first drive signal for driving the first PZT actuator, a second drive signal for driving the second PZT actuator, a third drive signal for driving the third PZT actuator, and a fourth drive signal for driving the fourth PZT actuator;

wherein;

the first drive signal has a fundamental frequency and a first stroke amplitude;

the second drive signal has the fundamental frequency and a second stroke amplitude;

the first stroke amplitude, the second stroke amplitude, and a relative phase of the first drive signal and the second drive signal are selected such that a tip of a cutting tool mounted in the cutting tool holder follows the substantially elliptical tool path in the vibration plane relative to the vibration element;

the third drive signal has a first perturbation frequency approximately equal to N times the fundamental frequency, where N is an integer greater than 1, and a first perturbation amplitude less than a lesser of the first stroke amplitude and the second stroke amplitude; and

the fourth drive signal has a second perturbation frequency approximately equal to N times the fundamental frequency, where N is an integer greater than N, and a second perturbation amplitude less than or equal to the first perturbation amplitude.

11. A VAM system according to claim 1, further comprising sensor circuitry electrically coupled to the third PZT actuator, the sensor circuitry adapted to receive a signal from the third PZT actuator indicative of a force between a tip of a cutting tool mounted in the cutting tool holder and a workpiece mounted in the workpiece holder.