Probe type shape measuring sensor, and NC processing equipment and shape measuring method using the sensor

• US 6,539,642 B1
• Filed: 02/27/2001
• Issued: 04/01/2003
• Est. Priority Date: 03/03/1999
• Status: Expired due to Fees

• Current Assignee: Riken
• Original Assignee: Riken
• Inventors: Morita, Shinya, Ohmori, Hitoshi, Yamagata, Yutaka, Moriyasu, Sei
• Primary Examiner(s): Bennett, G. Bradley
• Application Number:
  US09/763,747
• Time in Patent Office: 763 Days
• Field of Search: 335/56, 335/59, 335/60, 335/61, 335/51, 335/53
• US Class Current: 33/551
• CPC Class Codes: G01B 11/007 feeler heads therefor
• CPC Class Codes: G01B 11/2441 using interferometry
• CPC Class Codes: G01B 21/20 for measuring contours or curvatures, e.g. determining profile

Abstract

A probe head 10 and a laser interferometric displacement meter 20 are provided. The probe head supports a probe 2 that is capable of contacting a workpiece 1, that is free to move in the direction of the workpiece, and drives the probe towards the workpiece. The displacement meter measures the displacement of the probe with a high accuracy without contact. The probe head 10 is also provided with a probe shaft 12 with steps 11a, 11b at intermediate portions thereof and air bearings 14a, 14b that support the probe shaft on each side of the steps. The air bearings have a high stiffness in the radial direction, and the probe shaft is made to float by using compressed air, thus the resistance of the shaft to sliding is reduced. In addition, another compressed air is supplied to the location of the step and produces a driving force in the direction of the workpiece due to the difference of cross sectional areas on each side of the step, that provides a very small load within a predetermined range. Thereby, the measuring pressure can be adjusted to a constant very small load without reducing the stiffness of the bearings of the probe, and the measuring pressures can be varied freely. Therefore, a sub-micron accuracy of about 0.1 μm can be obtained, and the equipment can be made compact and is easily applied to on-machine measurements.

Claims

1. A probe shape measuring sensor comprising:

a probe head that supports, in a movable manner, a probe capable of contacting a workpiece with a low resistance to sliding in the direction of the workpiece, wherein the probe head drives the probe with a small load in the direction of the workpiece; and

a displacement measuring device that measures the displacement of the probe in a manner without contact, wherein the probe head comprises;

a long thin probe shaft having one end attached to the probe, and having a step at an intermediate positions thereof;

air bearings provided at each side of the step to support the probe shaft;

a first gas feeding means connected to provide a first pressurizing gas to the air bearings; and

a second gas feeding means connected to feed a second pressurizing gas, and, optionally, a third pressurizing gas, to the location of the step,

wherein the air bearings have a high stiffness in the radial direction and are disposed on the probe shaft to make the probe shaft float using the first pressurizing gas, whereby a resistance to sliding of the air bearings and the probe shaft is reduced, wherein the second gas feeding means maintains constant pressure of the second pressurizing gas and the optional third gas supplied to the location of the step thereby producing a driving force produced by a difference in probe shaft cross sectional area at the step in the direction of the workpiece so that the driving force is kept at a small value within a predetermined range.

2. The probe shape measuring sensor specified in claim 1, wherein the driving force of the probe shaft is not less than about 10 mgf and not more than about 500 mgf.

3. A shape measuring method comprising the steps of:

providing the probe shape measuring sensor specified in claim 2 incorporated in an NC processing device;

moving the probe shape measuring sensor relative to a workpiece; and

measuring the shape of the workpiece without removing the processed workpiece using the probe shape measuring sensor.

4. The shape measuring method specified in claim 3, further comprising:

processing, in real time, output from each numerical control axis of the NC processing device that are coordinates along each axis and signal output from the probe shape measuring sensor using a computer so the shape of the workpiece is measured without stopping the NC processing device.

5. An NC processing device comprising:

the probe shape measuring sensor specified in claim 1; and

a numerical control system connected to move the sensor, wherein the sensor is moved relative to the workpiece by the numerical control system so that the shape of the workpiece can be measured without dismounting the processed workpiece.

6. The NC processing device specified in claim 5, further comprising:

an interface that outputs the coordinates of each numerical control axis and signals from the probe shape measuring sensor, in real time, to equipment outside the device.

7. The probe shape measuring sensor specified in claim 1, wherein the displacement measuring device comprises:

a reflecting mirror installed at the other end of the probe shaft;

an optical fiber with an emitting end surface that faces the reflecting mirror with a distance L between the optical fiber and the reflecting mirror; and

a laser interferometric displacement meter that emits laser light through the optical fiber towards the reflecting mirror and measures the position of the reflecting mirror by light reflected from the reflecting mirror to the emitting end surface.

8. An NC processing device comprising:

the probe shape measuring sensor specified in claim 7; and

a numerical control system connected to move the sensor, wherein the sensor is moved relative to the workpiece by the numerical control system so that the shape of the workpiece can be measured without dismounting the processed workpiece.

9. The NC processing device specified in claim 8, further comprising:

an interface that outputs the coordinates of each numerical control axis and signals from the probe shape measuring sensor, in real time, to equipment outside the device.

10. A shape measuring method comprising the steps of:

providing the probe shape measuring sensor specified in claim 7 incorporated in an NC processing device;

moving the probe shape measuring sensor relative to a workpiece;

measuring the shape of the workpiece without removing the processed workpiece using the probe shape measuring sensor.

11. The shape measuring method specified in claim 10, further comprising:

processing, in real time, output from each numerical control axis of the NC processing device that are coordinates along each axis and signal output from the probe shape measuring sensor using a computer so the shape of the workpiece is measured without stopping the NC processing device.

12. An NC processing device comprising the probe shape measuring sensor specified in claim 1, further comprising a numerical control system programmed to move the sensor relative to the workpiece so that the shape of the workpiece is measured without dismounting the processed workpiece.

13. The NC processing device specified in claim 12, further comprising an interface connected to output the coordinates of each numerical control axis and signals from the probe shape measuring sensor, in real time, to equipment outside the device.

14. An NC processing device comprising:

the probe shape measuring sensor specified in claim 2; and

a numerical control system connected to move the sensor, wherein the sensor is moved relative to the workpiece by the numerical control system so that the shape of the workpiece can be measured without dismounting the processed workpiece.

15. The NC processing device specified in claim 14, further comprising:

an interface that outputs the coordinates of each numerical control axis and signals from the probe shape measuring sensor, in real time, to equipment outside the device.

16. A shape measuring method comprising the steps of:

providing the probe shape measuring sensor specified in claim 1 incorporated in an NC processing device;

moving the probe shape measuring sensor relative to a workpiece; and

measuring the shape of the workpiece without removing the processed workpiece using the probe shape measuring sensor.

17. The shape measuring method specified in claim 16, further comprising the steps of:

processing, in real time, output from each numerical control axis of the NC processing device and signal output from the probe shape measuring sensor using a computer so the shape of the workpiece is measured without stopping the NC processing device.

19. A shape measuring method comprising the steps of:

providing the probe shape measuring sensor specified in claim 1 incorporated in an NC processing device;

moving the probe shape measuring sensor relative to a workpiece; and

measuring the shape of the workpiece without removing the processed workpiece using the probe shape measuring sensor.

20. The shape measuring method specified in claim 19, further comprising the steps of:

processing, in real time, output from each numerical control axis of the NC processing device and signal output from the probe shape measuring sensor using a computer so that the shape of the workpiece is measured without stopping the NC processing device.

18. A shape measuring method comprising the steps of:

providing a probe installed at one end of a long thin probe shaft having a step at a location on the probe shaft;

supporting the probe shaft using a first pressurizing gas so that the probe shaft moves longitudinally with a low resistance to sliding;

supporting the probe shaft in an axial direction;

supplying a second gas, and optionally a third gas, to the location of the step to produce a driving force driving the probe shaft in the direction of the workpiece, wherein the driving force is kept at a small load by the pressure of the second gas, and optionally the third gas; and

measuring a displacement of the probe in the direction of the workpiece in a manner without contact using a laser interferometric displacement meter.