JPH02504427A - Test bar for positioning device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Test bar for positioning device Technical field The present invention relates to a position determining device for a coordinate measuring device, an inspection robot, a machine tool, etc. The invention relates to a bar for testing the precision or repeatability of the device.

Background technology Allows for three-dimensional movement within the working volume of the device. measuring the workpiece using a positioning device with a probe attached to the It has been known. The probe is moved to contact the desired surface of the workpiece. When the probe and workpiece come into contact, this is caused by the probe. is detected, and the Xl, Y, and Z coordinate values of the contact point are read.

The volumetric accuracy and positioning repeatability of such devices, especially coordinate measuring devices, It is known to use a test bar for verification. An example of a test bar is D E-A-2603376 (Bendix), L12-A-4,435,906 (Bryan).

US-A-4,437,151 (Hurt) and “Tooling and P. No. 4 of ``Reduction'' magazine (May 1983 vol. 1.49. No. 2) "MeasuringUp" by B. Nagler published on pages 0-47 : Coordinate Measuring Machine 5urv ey” (see page 43).

Such test bars generally have a fixed length. one or both ends of the test bar. Touch the probe and calculate the length of the bar from the reading obtained. The device is verified. This allows the test bar to be placed at different locations within the working volume of the equipment. It is set at a few points and repeated, the results are compared and any differences are recorded. . In this way, the entire working volume of the device can be tested. The test bar It is rotatably mounted, which facilitates repositioning within the working volume.

The conventional test bar mentioned here has a precise spherical test pole at one or both ends. and after obtaining a reading of 4 or more of the coordinates of a point on the pole surface, the center of the pole is calculated. The length measured is the distance between the pole center and the pivot point, or the bar – is the distance between the centers of the two poles at each end.

Alternatively, International Publication WO 35105176 describes a series of measurements over the volume of the device. A test bar is shown to facilitate automation. A unit provided at the end of the test bar. Instead of a pure ball, the specification discloses a rotatable test bar, whose free end extends longitudinally to form a fork for engaging the stylus of the probe. It has prongs. For reading purposes, there is a A relatively small pole is provided for contacting the stylus tip. chiasmoid The movement position setting section (a kinematiclo) at the tip of the stylus cation), you can accurately determine the point of contact with the end of the bar. , which eliminates the need to perform more than four readings on the pole. chiasmoid process and engagement causes the probe to move the working volume (sometimes the stylus moves along with itself) dragging the end of the bar, thus eliminating the need for manual repositioning of the bar.

In all the conventional devices mentioned above, the contact between the probe and the test bar is determined by Bu himself. Such probes give highly repeatable results. However, pre-travel is likely to occur. vinegar That is, there is a small distance between the moment of contact and the moment when the trigger signal is generated by the probe. You will have to move a distance. In addition, many such probes have no direction of contact. have different buri label values. As a result of these results, the use of the test bar Therefore, the measured error is the error caused by the device itself and the error caused by the probe. are combined. Different accuracy values may be obtained if different probes are used. It will be. The device should be separated from any errors introduced by the probe. It is desired to be able to measure any errors caused by the device itself.

Disclosure of invention The present invention provides an extension member and a probe contact element provided at least one end of the extension member. contact element forming part of the test bar, said probe contact element and the contact between the probe; A test bar for a position determining device is provided, comprising means for detecting a position determination device.

Preferably, the sensing means comprises one or more piezo-electric elements or strain gauges, The probe contact element is suitably disposed between the probe contact element and the extension member. Preferably, said extension The member includes a bearing hand for rotatably positioning the extension member itself with respect to the device. It has steps. In one form, the extension member includes one at each end of the extension member. Two probe contact elements are provided, each with its own sensing means.

Brief description of the drawing Preferred embodiments of the invention will now be described with reference to the accompanying drawings. Here, FIG. 1 is a schematic diagram showing a coordinate measuring machine together with a first embodiment of a test bar; Fig. 2 is a view of the test bar shown in Fig. 1 in the n direction, and Fig. 3 is a view of the test bar shown in Fig. 1. Block circuit diagrams of the interface circuit portion for the Fig. 6 is a partial view showing a modified configuration example of the test bar shown in Fig. 1, and Fig. 7 is Fig. 6. Figure 8 is a sectional view taken along the line ■-■ in Figure 8, except that it shows another embodiment of the test bar. Schematic diagram corresponding to Figure 1, Figure 9 is a diagram showing details of Figure 8; FIG. 1O is a view taken in the X direction in FIGS. 8 and 9.

BEST MODE FOR CARRYING OUT THE INVENTION The coordinate measuring machine shown in Figure 1 is generally of the conventional type and is That is, it is equipped with a table 1o, on which the workpiece to be measured (during normal operation) is placed. is placed. The gantry 12 has a vertical column 14 (within it) for movement in the Y direction. (only one is shown). Carriage 16 is gantry 1 2 can be slid in the X direction, and the tile (quill) 18 can be slid vertically on the 2 direction within the carriage 16.

The bottom edge of the tile 18 holds a touch probe 20, which is connected to the workpiece. It has a contact stylus 22. As is known, the stylus 22 is connected to the probe 20 in such a way as to prevent damage when contacting the work piece. ing. In particular, the contact probe 2° is a touch-trigger probe, in which The stylus 22 has a precisely fixed kinematically defined static position relative to the quill 18. It is urged toward the stop position. However, in the present invention, the pole bar It should be noted that any form of touch probe may be used as It is possible.

In normal operation of inspecting a workpiece, the probe 2° moves through the X, Y and Z movements mentioned above. for the operation of the X, Y and two motor drives 24 (not shown in detail) of the machine that controls the This allows the coordinate measuring machine to perform three-dimensional operations in order to contact the desired surface of the workpiece. Can be positioned anywhere within the business volume. This is done by numerical control of computer 26. will be held. at any given time in the space of the stylus 22. The position is determined by each scale 28.30.32. Each scale is The X, Y and and 2 counters 34, 36, and 38.

The probe 20 contacts the workpiece surface when it contacts the interface (Fig. (not shown) to the computer 26, and then the computer 26 The computer 26 freezes the 8 forces of the counters 34, 36, 38 L/, Read the counter 8 force to determine the X, Y and 2 coordinates of the point of contact.

FIG. 1 also shows a test bar 40 according to one embodiment of the invention. This Tess The top bar 40 includes an extension bar 42, and the extension bar 42 is arranged on the table 10. It is mounted at a central pivot point 44 on top of a pillar 46. In the axis area 44 The pillar 46 has a corresponding pole 48 on the underside of the bar 42. contained within the socket. Therefore, the bar 42 can be oriented either horizontally or vertically. It can also be rotated. The pivot region 44 has clamping means (not shown). Once rotated to the desired orientation, the bar 42 can be clamped in that position. Wear.

At each end of the extension bar 42 there is provided a ball 50 having a precisely spherical surface. ing. As particularly seen in FIG. It is housed in a shaped recess 52. The pole has spaces within the conical recess. Three pressure sensing elements are attached. In particular, the element 54 is a piezoelectric element. It is a child.

In FIG. 2, the ball 50 is omitted for clarity, but its position is indicated by a dashed line. It is shown.

The piezoelectric element 54 receives an impact when the squillous 22 contacts the pole 50. the shock wave generated within the associated ball 5o, and also the subsequent reaction caused by the contact. Sensitive to force. A shock wave is the earliest indication of blow-boo test bar contact, and Piezoelectric elements can detect shock waves by preferable. However, as an equivalent, strain gauges are used to detect stress. You can also use lei. Element 54 is connected to the computer via interface 56. It is connected to the controller 26. A portion of the circuit is shown in FIG. No noise rather than in a separate remote interface unit to improve sensitivity. It is advantageous to include at least a portion of the circuitry of FIG. 3 within the bar 42 itself.

Referring to FIG. 3, the outputs of the three piezoelectric elements 54 are first charge elements 58, and then each It is sent to the absolute value circuit 60. These rectify signals and convert them into The signal is supplied to each comparator 62. Here, the signal is a threshold voltage from the reference power supply 54. compared to the field voltage. Therefore, when the piezoelectric element output exceeds a certain value, the comparator outputs a signal. The outputs of comparator 62 are wired-ORed and combined. A trigger output is provided on line 70 and this output is further processed by interface 56. and is sent to the trigger input of the computer 26. The field around the comparator 62 Resistors 66 and 68 in the feedback circuit add some hysteresis to the trigger output. Equipped with Lysis. The trigger output on line 70 is connected to either piezo element 54. It will be understood that this is caused by first exceeding a predetermined threshold. Probably. With such a circuit, three piezoelectric elements are used for different directions. What happens is that no matter in which direction the contact between the stylus 22 and the pole 50 occurs, It also guarantees that a trigger signal will be generated regardless of the direction in which the generated shock wave propagates. I testify. The absolute value circuit 60 is configured such that the initial acceleration applied to a given piezo element is positive. guarantees that the trigger signal occurs immediately, whether positive or negative.

When using a strain gauge array, the strain gauge is a resistive device, as opposed to Since the piezoelectric element is a capacitive device, the interface needs to be changed. There is.

As described with respect to FIGS. 1 and 2, the installation of balls 50 within bar 42 is It can be changed as desired. One modification example is shown in FIG. here , the end of the bar 42 and the ball 50 have opposing flat surfaces 72° 74 and are spaced apart. Three piezoelectric elements 54 are sandwiched between the flat surfaces. There is. Contact between the stylus 22 and the pole 50 in any direction If the three elements 54 are made to respond to the resulting shock wave, the three elements 54 can be combined into a single It may be replaced with a piezoelectric element.

FIG. 5 shows the free end of rod 76 located within a pore 78 in the end of bar 42. A configuration in which a pole 50 is arranged is shown. In this example, four piezoelectric elements are set up. I'm being kicked. One of these elements 54' is connected to the end of the rod 76 and the pore 78. while the other three elements 54'' are located between the rod and the bottom of the pore 7. 80 and spaced apart radially around the rod 76 between the cylindrical surface and the cylindrical surface. It is placed. A circuit similar to that in Figure 3 can be used, but with three sets. Instead, it has four sets of components 58, 60, and 62.

6 and 7 show a modification of FIG. 5.

In this figure, identical reference numbers indicate similar parts. Piezoelectric element 54' , 54'' instead of a single annular pin surrounding the rod 76 within the pore 78. There is an ezoelectric element 90. Element 90 is shear sensitive and Be able to respond to stylus touch as well.

The test bar of FIG. 1 has a fixed length between the centers of the two balls 50. use Manual movement control of the quill 18 or computer By the action of numerical control of the data 26, each of four or more points on the surface of one ball 50 is The stylus 22 is brought into contact with each other. When contact occurs, this contact is piezoelectric element 54 and the trigger output on line 70 is sent to computer 2. Sent to 6. This computer, in the usual way, registers counters 34, 36, 38. From there, the x, y, z coordinates of the quill 18 at the point of contact are read. Contacted 4 The computer calculates the center coordinates of the ball 50 from the above x, y, and z coordinates.

The whole procedure is repeated until the center coordinates of the other ball 50 at the opposite end of the bar 42 are obtained. returned. The distance between two center points is therefore easily calculated. over the entire working volume To determine machine accuracy, the procedure just described involves testing within the three-dimensional working volume of the machine. It is repeated with many different positions and orientations of the bar 42 and the results are compared.

The piezoelectric element 54 is activated as soon as contact occurs between the stylus 22 and the pole 50. immediately generates a signal. In response to this contact, probe 20 generates a trigger signal. With conventional technology, measurement accuracy not only depends on the accuracy of the coordinate measuring machine itself; , the precision of the probe 20, including the pre-travel of the probe. Depends on the degree.

Therefore, the volume that can be measured by such prior art devices is ic) Accuracy is effective while a given probe is installed on the machine but is not valid if the probe is replaced. However, in an uninvented embodiment , the measurement accuracy has no relation to the accuracy of the probe 20. Of course, in any case If you want to know the accuracy of the combination of machine and probe, the test bar of the present invention can also be used. Can be used in the following methods.

If desired, use one point on only one free end, such as the double end test bar of Figure 1. A single end test bar with a bar 50 can also be substituted. axis area 4 4, the other end of such a test bar is placed on the table 10. It has a pole rotatably housed within the cage. That pole is well known This test bar can be magnetically clamped in the socket in the desired direction. The standard length of the bar is between the center of the pole 60 at the free end and the socket in which the bar is housed. between the center of the ket. A single pole 50 corresponds to the test par 40 in FIG. Similarly, it is supported by a piezoelectric element 54.

Figures 8, 9, and 10 show 1 and 1 installed on the same coordinate measuring machine as in Figure 1. Other test bars according to other embodiments of the present invention are shown, and corresponding parts have the same references as in FIG. A reference number is given. The test par 80 shown in FIG. This is an improvement of the test bar shown in No. 105176. In addition, this international exhibition is the This reference number is incorporated by reference into this specification. Machine volumetric accuracy (volumetric accuracy) to enable automation of testing. This is what was intended, but since it was stated in the bulletin, it will not be described in detail here. does not explain.

However, briefly stated, the test par 80 has a pole at its free end. The stylus 22 can be freely rotated around the stylus and the bar. It has means for allowing relative translational movement of. In particular, engaging the stylus 22 a pair of parallel, horizontally longitudinally extending prongs forming forks that A prong 82 is provided at the free end of the bar 80. What kind of desire is this? This allows movement of the quill 18 causing rotation of the test par 80 to the position shown in FIG.

The end of the bar 80 also includes a spherical ball surface located below and between the prongs. It has a surface 84. When it is desired to perform a coordinate reading, the tiles 18 are moved inwards (preferably is moved radially inward), and the stylus 22 is moved kinematically on the ball surface. contact the pole surface 84 at a location defined by . This means that the stylus 22 is also This is because the two protrusions 82 are in contact with each other.

The above-mentioned variations regarding international publication can be seen more clearly in Figure 9. Directly to the end of the bar 80 Instead of being attached, the pole 84 is attached to the end of the bar via a piezoelectric crystal 86. It is supported by the department. This element 86 is set to a trigger ratio in the same manner as described in Section 3. , which is connected to an amplifier 58 , an absolute value circuit 60 and a comparator 62 , for generating a power signal. ing. However, the stylus 22 always touches the pole 84 in the same (radial) direction. Therefore, in order to reliably pick up the signal, only one piezoelectric element is required. child 86 and a set of components 58.60.62.

FIG. 9 also shows that the piezoelectric crystal 86 and pole 84 are bar through a layer of rigid soundproofing material 88, such as a foam ceramic material. It is shown attached to the end of 80. This may be due to mechanical noise or prongs. Any noise such as that caused by the sliding of the stylus 22 against the As a result, the piezoelectric crystal 86 is transmitted through the bar 80 to the Viez electric crystal 86. This reduces any risk that the listal 86 will be accidentally triggered.

The above embodiments of the invention use one or more piezoelectric elements to detect contact. I was doing it. This is because the piezoelectric element has a systematic error (systematic error). This is preferable because it can give the most accurate results without the need to correct It is θ. However, to detect contact, strain gauges and electromagnetic detectors are required. , photoelectric detectors, or also other means such as equivalent electrical switching elements. , may be provided within or on the test bar.

(Margin below) international search report Compliance investigation report

Claims (16)

[Claims] 1. an extension member, a contact element contacted by a touch probe, and a position determining device a detection means for detecting contact between the contact element and the probe; and used for calibrating the positioning device. 2. 2. The device according to claim 1, wherein the means for detecting characterized by having a sensing element suitable for generating a signal in response to the stress occurring in the element; A device used as a sign. 3. In the device according to claim 2, the detection element for detecting pressure is a piezoelectric element. A device characterized in that it is a zoelectric element. 4. In the device according to claim 2, the detection element for detecting pressure is a strain gauge. A device characterized by being a medium. 5. The apparatus according to any one of claims 1 to 4, wherein the The member is attached to the support part so as to be rotatable about a pivot point. Device. 6. The apparatus according to any one of claims 1 to 5, wherein the The contact element is connected to the member via the pressure sensing element. equipment. 7. The apparatus according to any one of claims 1 to 6, wherein the A device characterized in that the contact element has a spherical contact surface at one end of the member. 8. The apparatus according to any one of claims 1 to 7, wherein the A device characterized in that it has a contact element at the end of the member. 9. The apparatus according to any one of claims 1 to 8, wherein the The contact element is connected to the member via the three pressure sensing elements arranged at equal intervals. A device characterized by: 10. In the device according to any one of claims 1 to 5, Device characterized in that the contact element has a kinematic support relative to a spherical surface. 11. The device according to any one of claims 1 to 5 or 10 in order to make a connection between the member and the stylus of the touch probe. further comprising means for the stylus to have a spherical element at its free end; enabling free rotation of the stylus with respect to the free end of the stylus; Also, the stylus and the member are characterized in that they enable relative translational movement between the stylus and the member. A device used as a sign. 12. 12. The apparatus of claim 11, wherein said means is connected to said member. a pair of rods, the axes of which are spaced apart and extend parallel to each other; A device used as a sign. 13. 13. The device of claim 12, wherein the abutment for the spherical element is characterized in that it is provided adjacent to a connecting portion of the rod to the member. Device. 14. In the device according to claim 12 or 13, mutually converging a pair of surfaces, the direction of convergence being perpendicular to the direction of extension of the member; device to do. 15. 15. The apparatus of claim 14, wherein the abutment and the converging surface A device characterized in that it serves as a motion support. 16. In the device according to any one of claims 13 to 15, , wherein the abutment is connected to the member via the pressure detection element. device to do.