WO1990009258A1 - Electronic centre-finder - Google Patents

Electronic centre-finder Download PDF

Info

Publication number
WO1990009258A1
WO1990009258A1 PCT/GB1990/000239 GB9000239W WO9009258A1 WO 1990009258 A1 WO1990009258 A1 WO 1990009258A1 GB 9000239 W GB9000239 W GB 9000239W WO 9009258 A1 WO9009258 A1 WO 9009258A1
Authority
WO
WIPO (PCT)
Prior art keywords
centre
finder
shaft
machine tool
probe
Prior art date
Application number
PCT/GB1990/000239
Other languages
French (fr)
Inventor
Alan Robert Brian Smith
Original Assignee
Alan Robert Brian Smith
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Alan Robert Brian Smith filed Critical Alan Robert Brian Smith
Publication of WO1990009258A1 publication Critical patent/WO1990009258A1/en

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
    • G01B7/004—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring coordinates of points
    • G01B7/008—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring coordinates of points using coordinate measuring machines
    • G01B7/012—Contact-making feeler heads therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23Q—DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING; MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT
    • B23Q17/00—Arrangements for observing, indicating or measuring on machine tools
    • B23Q17/22—Arrangements for observing, indicating or measuring on machine tools for indicating or measuring existing or desired position of tool or work
    • B23Q17/2233—Arrangements for observing, indicating or measuring on machine tools for indicating or measuring existing or desired position of tool or work for adjusting the tool relative to the workpiece
    • B23Q17/225—Arrangements for observing, indicating or measuring on machine tools for indicating or measuring existing or desired position of tool or work for adjusting the tool relative to the workpiece of a workpiece relative to the tool-axis
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
    • G01B7/30—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring angles or tapers; for testing the alignment of axes
    • G01B7/31—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring angles or tapers; for testing the alignment of axes for testing the alignment of axes

Definitions

  • the invention relates to an electronic centre finder for a machine tool. It is often difficult to align accurately the tool-holder of a machine tool with respect to a required machining position on a work-piece. Often the machining position is the centre of a hole to be drilled, and for this reason the term "centre-finder" will be used herein. However, it is to be understood that the principles of the invention may be used to establish other machine- tool references, such as edges, for example.
  • a centre-finder for a machine tool which comprises a body having at one end a collet head for insertion into a machine-tool tool-holder; an elongate shaft fixed at one end at the collet head and free to flex in the body; a probe mounted on the other end of the shaft; and a transducer arrangement arranged to detect flexure of the shaft in two dimensions and give an output which allows adjustment of the position of a work-piece to align a work position with the tool- holder.
  • the transducer arrangement may comprise proximity detectors arranged intermediate the ends of the shaft and effective to detect shaft movement as a result of flexure.
  • proximity detectors may be capacitive, for example.
  • the transducer arrangement comprises strain gauges mounted on the shaft to detect flexure directly.
  • the shaft is square and eight strain gauges are provided, two on each side.
  • Another arrangement envisaged has four strain gauges, one on each side.
  • Another arrangement in accordance with the invention is a triangular-section shaft with at least one strain gauge on each side. Electronic analysis of the three outputs can give two-dimensional (X and Y) output components.
  • the transducer outputs are applied to electronic amplifiers and preferably the signals are digitised to give X and Y co-ordinate outputs on a digital display device.
  • the device may comprise one display which is switched between X and Y inputs in turn or a double display for showing the X and Y co ⁇ ordinates simultaneously.
  • an adjustment mechanism is provided near the fixed end of the shaft for setting the axial position of the shaft in the body.
  • the mounting for the probe preferably allows the probe to move axially against resilience with respect to the shaft. This protects the shaft against damage should the probe be forced against the work-piece.
  • the resilience may be provided by a metal spring, rubber springs or air spring arrangement, for example.
  • Figure 1 is a schematic cross-sectional elevation of a centre-finder in accordance with the invention
  • Figure 2 is a schematic circuit diagram of the output circuit for the centre-finder of Figure 1;
  • Figure 3 shows two alternative probes for the centre-finder.
  • a centre- finder having a body 1 with, at one end, a circular- sectioned collet head 2 which fits a collet chuck (not shown) of a machine tool.
  • the chuck has an axis 4 and the purpose of the centre-finder is to allow the axis 4 to be aligned precisely with (in this example) a hole centre 5 of a work-piece 6.
  • the centre-finder has a central shaft 7 of 4mm square hardened section silver steel.
  • the shaft is fixed at end 8 and at the other end has a circular steel sleeve 9 fitted.
  • the sleeve is an adaptor to allow the fitting of a probe 10.
  • Probe 10 has an internal bore which is a sliding fit on the shaft 9 and an external rib 11 which passes through a bronze annular ring 12 in the body.
  • a helical compression spring is located between the rib 11 and a bronze stop 13 on the shaft. The spring encircles the stem 14 of the probe and provides cushioning against axial shocks which may be experienced by the probe. At full compression of the spring a step 15 on the probe abuts the ring 12.
  • the nature of the fit of the probe 10 on the sleeve 9 and the presence of an air-filter cavity 18 within the, bore of the probe 10 serve to retain the probe in position. The arrangement allows radial movement of the probe and flexure of the shaft 7.
  • the centre-finder there are four adjustment screws, two of which are shown at 16.
  • the screws are set in the body and co-operate with the shaft 7 to move it laterally. This is to allow adjustment of the shaft position.
  • strain gauges At about half-way down the length of the shaft 7 there are eight strain gauges, arranged in pairs on each side of the shaft. The members of each pair are connected in series.
  • Figure 1 shows four of the strain gauges SI, S2, S3 and S4. Wires from the strain gauges lead to terminals on an insulating terminal block 17.
  • Figure 2 is a circuit diagram of an output circuit connected to the terminals of the centre- finder.
  • the eight strain gauges of the system are designated SI to S8, pairs SI and S2 and S3 and S4 being on opposite sides, in an 'X' dimension, and pairs S5 and S6 and S7 and S8 being on opposite sides in the orthogonal 'Y' dimension.
  • bridge circuits There are two bridge circuits: an 'X' bridge 21 and at * Y' bridge 22 which include respective strain gauges together with pairs of equal standard resistors R.
  • the outputs from the bridge circuits are applied to respective differential amplifiers DAI, DA2.
  • the outputs from the differential amplifiers are digitised in analogue-to-digital convertors ADl, AD2 and applied to respective X and Y co-ordinate digital displays Dl, D2.
  • the collet head of the centre-finder is mounted in the chuck and the probe is lowered to the hole at centre 5 in the work-piece.
  • This may, for example, be a pilot hole.
  • the probe centres in the hole and may therefore bend the shaft 7 slightly if there is any misalignment.
  • the degree of bending and thus misalignment in the X and Y directions is read off from the display and positioning correction i s made accordingly. It is possible to arrange feed ⁇ back of the X and Y co-ordinate signals to a numerically controlled machine tool so that correction is automatic. In general, however, correction will be made manually.
  • Figure 3 shows at (a) a probe for locating the centre of a shaft rather than a hole. Instead of a 'V * cut as shown, the probe may have a conical depression for locating the centre of a ball or shaft end-on.
  • Figure 3(b) shows in elevation and plan a probe for locating the edge of a work-piece.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Gripping On Spindles (AREA)

Abstract

An electronic centre-finder for a machine tool comprises of body (1) with a collet head (2) at end and an elongate shaft (7) fixed near the collet head (2) and free to flex in the body (1). A probe (10) is mounted on the other end of the shaft (7) and a transducer arrangement is arranged to detect flexure of the shaft (7) in two dimensions and give an output, preferably in X and Y co-ordinate form, which allows adjustment of the position of the work-piece (6) to align a work position (a centre) with the tool-holder.

Description

Figure imgf000003_0001
ELECTRONIC CENTRE FINDER
The invention relates to an electronic centre finder for a machine tool. It is often difficult to align accurately the tool-holder of a machine tool with respect to a required machining position on a work-piece. Often the machining position is the centre of a hole to be drilled, and for this reason the term "centre-finder" will be used herein. However, it is to be understood that the principles of the invention may be used to establish other machine- tool references, such as edges, for example.
According to the invention there is provided a centre-finder for a machine tool which comprises a body having at one end a collet head for insertion into a machine-tool tool-holder; an elongate shaft fixed at one end at the collet head and free to flex in the body; a probe mounted on the other end of the shaft; and a transducer arrangement arranged to detect flexure of the shaft in two dimensions and give an output which allows adjustment of the position of a work-piece to align a work position with the tool- holder.
The transducer arrangement, may comprise proximity detectors arranged intermediate the ends of the shaft and effective to detect shaft movement as a result of flexure. Such proximity detectors may be capacitive, for example.
Preferably, however, the transducer arrangement comprises strain gauges mounted on the shaft to detect flexure directly. In a preferred arrangement the shaft is square and eight strain gauges are provided, two on each side. Another arrangement envisaged has four strain gauges, one on each side. Another arrangement in accordance with the invention is a triangular-section shaft with at least one strain gauge on each side. Electronic analysis of the three outputs can give two-dimensional (X and Y) output components.
The transducer outputs are applied to electronic amplifiers and preferably the signals are digitised to give X and Y co-ordinate outputs on a digital display device. The device may comprise one display which is switched between X and Y inputs in turn or a double display for showing the X and Y co¬ ordinates simultaneously. Preferably an adjustment mechanism is provided near the fixed end of the shaft for setting the axial position of the shaft in the body. At the other end of the shaft the mounting for the probe preferably allows the probe to move axially against resilience with respect to the shaft. This protects the shaft against damage should the probe be forced against the work-piece. The resilience may be provided by a metal spring, rubber springs or air spring arrangement, for example. The invention will further be described with reference to the accompanying drawings, of which:-
Figure 1 is a schematic cross-sectional elevation of a centre-finder in accordance with the invention; Figure 2 is a schematic circuit diagram of the output circuit for the centre-finder of Figure 1; and
Figure 3 shows two alternative probes for the centre-finder.
Referring to Figure 1 there is shown a centre- finder having a body 1 with, at one end, a circular- sectioned collet head 2 which fits a collet chuck (not shown) of a machine tool. The chuck has an axis 4 and the purpose of the centre-finder is to allow the axis 4 to be aligned precisely with (in this example) a hole centre 5 of a work-piece 6. The centre-finder has a central shaft 7 of 4mm square hardened section silver steel. The shaft is fixed at end 8 and at the other end has a circular steel sleeve 9 fitted. The sleeve is an adaptor to allow the fitting of a probe 10. Probe 10 has an internal bore which is a sliding fit on the shaft 9 and an external rib 11 which passes through a bronze annular ring 12 in the body. A helical compression spring is located between the rib 11 and a bronze stop 13 on the shaft. The spring encircles the stem 14 of the probe and provides cushioning against axial shocks which may be experienced by the probe. At full compression of the spring a step 15 on the probe abuts the ring 12.' The nature of the fit of the probe 10 on the sleeve 9 and the presence of an air-filter cavity 18 within the, bore of the probe 10 serve to retain the probe in position. The arrangement allows radial movement of the probe and flexure of the shaft 7.
At the upper part of the centre-finder there are four adjustment screws, two of which are shown at 16. The screws are set in the body and co-operate with the shaft 7 to move it laterally. This is to allow adjustment of the shaft position.
At about half-way down the length of the shaft 7 there are eight strain gauges, arranged in pairs on each side of the shaft. The members of each pair are connected in series. Figure 1 shows four of the strain gauges SI, S2, S3 and S4. Wires from the strain gauges lead to terminals on an insulating terminal block 17.
Figure 2 is a circuit diagram of an output circuit connected to the terminals of the centre- finder. The eight strain gauges of the system are designated SI to S8, pairs SI and S2 and S3 and S4 being on opposite sides, in an 'X' dimension, and pairs S5 and S6 and S7 and S8 being on opposite sides in the orthogonal 'Y' dimension.
There are two bridge circuits: an 'X' bridge 21 and at *Y' bridge 22 which include respective strain gauges together with pairs of equal standard resistors R. The outputs from the bridge circuits are applied to respective differential amplifiers DAI, DA2. The outputs from the differential amplifiers are digitised in analogue-to-digital convertors ADl, AD2 and applied to respective X and Y co-ordinate digital displays Dl, D2.
In use, the collet head of the centre-finder is mounted in the chuck and the probe is lowered to the hole at centre 5 in the work-piece. This may, for example, be a pilot hole. The probe centres in the hole and may therefore bend the shaft 7 slightly if there is any misalignment. The degree of bending and thus misalignment in the X and Y directions is read off from the display and positioning correction is made accordingly. It is possible to arrange feed¬ back of the X and Y co-ordinate signals to a numerically controlled machine tool so that correction is automatic. In general, however, correction will be made manually. Figure 3 shows at (a) a probe for locating the centre of a shaft rather than a hole. Instead of a 'V* cut as shown, the probe may have a conical depression for locating the centre of a ball or shaft end-on. Figure 3(b) shows in elevation and plan a probe for locating the edge of a work-piece.

Claims

1 A centre-finder for a machine tool which comprises a body having at one end a collet head for insertion into a machine-tool tool-holder; an elongate shaft fixed at one end at the collet head and free to flex in the body; a probe mounted on the other end of the shaft; and an transducer arrangement arranged to detect flexure of the shaft in two dimensions and give an output which allows adjustment of the position of the work-piece to align a work position with the tool-holder.
2 A centre-finder for a machine tool as claimed in Claim 1 wherein the transducer arrangement comprises strain gauges mounted on the shaft to detect flexure directly.
3 A centre-finder for a machine tool as claimed in Claim 2 wherein the shaft is square and eight strain gauges are provided, two on each side. 4 A centre-finder for a machine tool as claimed in Claim 2 wherein the shaft is square and four strain gauges are provided, one on each side.
5 A centre-finder for a machine tool as claimed in Claim 2 wherein the shaft is triangular in section and there is at least one strain gauge on each side.
6 A centre-finder for a machine tool as claimed in any of preceding Claims wherein the transducer outputs are applied to electronic amplifiers to give X and Y co-ordinate outputs on a display device.
7 A centre-finder for a machine tool as claimed in Claim 6 wherein the signals are digitised and the display device is digital. 8 A centre-finder for a machine tool as claimed in Claim 6 or Claim 7 wherein there is • a single display which is switched between X and Y inputs in turn.
9 A centre-finder for a machine tool as claimed in Claim 7 wherein the display is a double display showing both the X and Y co-ordinates simultaneously.
10 A centre-finder for a machine tool as claimed in any of the preceding claims wherein an adjustment mechanism is provided near the fixed end of the shaft for setting the radial position of the shaft in the body.
11 A centre-finder for a machine tool as claimed in any of the preceding claims wherein there is provided a mounting for the probe which allows the probe to move axially against resilience with respect to the shaft.
PCT/GB1990/000239 1989-02-14 1990-02-14 Electronic centre-finder WO1990009258A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB898903256A GB8903256D0 (en) 1989-02-14 1989-02-14 Electronic centre finder
GB8903256.9 1989-02-14

Publications (1)

Publication Number Publication Date
WO1990009258A1 true WO1990009258A1 (en) 1990-08-23

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0523905A2 (en) * 1991-07-09 1993-01-20 Stryker Corporation Axial alignment of a drill guide
WO1993010943A2 (en) * 1991-11-29 1993-06-10 John Entwistle Orientation apparatus and a method
WO2004089570A1 (en) * 2003-04-07 2004-10-21 Fronius International Gmbh Seam tracking sensor for welding robots
DE102014208050A1 (en) * 2014-04-29 2015-10-29 Siemens Aktiengesellschaft Screwdriver blade, screwdriver and method for independently threading a screwdriver blade
WO2019101439A1 (en) * 2017-11-22 2019-05-31 Siemens Aktiengesellschaft Measuring system for sensing the spatial position of a securing pin and method for removing a securing pin by drilling

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3362076A (en) * 1966-03-14 1968-01-09 Computing Devices Canada Differential air gauge
DE2042506A1 (en) * 1970-08-27 1972-03-02 Werkzeugmasch Heckert Veb Measuring device for determining position and dimensional deviations on workpieces
GB1374416A (en) * 1971-12-23 1974-11-20 Staveley Ind Ltd Control link for machine tool
JPS5217276A (en) * 1975-07-31 1977-02-09 Futaba Corp Reference surface setting device for processing machine
GB2000700A (en) * 1977-07-11 1979-01-17 Fischer Ag Georg Method and apparatus for trimming workpieces
JPS5733301A (en) * 1980-08-08 1982-02-23 Mitsutoyo Mfg Co Ltd Copying probe for coordinate measuring machine
US4477978A (en) * 1982-10-01 1984-10-23 Toyota Jidosha Kabushiki Kaisha Dimension measuring apparatus
DE3427413C1 (en) * 1984-07-25 1986-01-02 Dr. Johannes Heidenhain Gmbh, 8225 Traunreut Probe device
EP0297031A1 (en) * 1987-06-16 1988-12-28 C.A. Weidmüller GmbH & Co. Machining tool provided with a feeler apparatus

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3362076A (en) * 1966-03-14 1968-01-09 Computing Devices Canada Differential air gauge
DE2042506A1 (en) * 1970-08-27 1972-03-02 Werkzeugmasch Heckert Veb Measuring device for determining position and dimensional deviations on workpieces
GB1374416A (en) * 1971-12-23 1974-11-20 Staveley Ind Ltd Control link for machine tool
JPS5217276A (en) * 1975-07-31 1977-02-09 Futaba Corp Reference surface setting device for processing machine
GB2000700A (en) * 1977-07-11 1979-01-17 Fischer Ag Georg Method and apparatus for trimming workpieces
JPS5733301A (en) * 1980-08-08 1982-02-23 Mitsutoyo Mfg Co Ltd Copying probe for coordinate measuring machine
US4477978A (en) * 1982-10-01 1984-10-23 Toyota Jidosha Kabushiki Kaisha Dimension measuring apparatus
DE3427413C1 (en) * 1984-07-25 1986-01-02 Dr. Johannes Heidenhain Gmbh, 8225 Traunreut Probe device
EP0297031A1 (en) * 1987-06-16 1988-12-28 C.A. Weidmüller GmbH & Co. Machining tool provided with a feeler apparatus

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0523905A2 (en) * 1991-07-09 1993-01-20 Stryker Corporation Axial alignment of a drill guide
EP0523905A3 (en) * 1991-07-09 1993-05-12 Stryker Corporation Axial alignment of a drill guide
WO1993010943A2 (en) * 1991-11-29 1993-06-10 John Entwistle Orientation apparatus and a method
GB2262249A (en) * 1991-11-29 1993-06-16 John Entwistle Orientation apparatus and method for a machine part relative to a workpiece.
WO1993010943A3 (en) * 1991-11-29 1993-09-30 John Entwistle Orientation apparatus and a method
GB2262249B (en) * 1991-11-29 1995-01-18 John Entwistle Orientation apparatus and a method
WO2004089570A1 (en) * 2003-04-07 2004-10-21 Fronius International Gmbh Seam tracking sensor for welding robots
DE102014208050A1 (en) * 2014-04-29 2015-10-29 Siemens Aktiengesellschaft Screwdriver blade, screwdriver and method for independently threading a screwdriver blade
WO2019101439A1 (en) * 2017-11-22 2019-05-31 Siemens Aktiengesellschaft Measuring system for sensing the spatial position of a securing pin and method for removing a securing pin by drilling

Also Published As

Publication number Publication date
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