EP2771641A1

EP2771641A1 - Coordinate measuring apparatus

Info

Publication number: EP2771641A1
Application number: EP12781025.7A
Authority: EP
Inventors: Georg Mies
Original assignee: Klingelnberg GmbH
Current assignee: Klingelnberg GmbH
Priority date: 2011-10-28
Filing date: 2012-10-11
Publication date: 2014-09-03
Also published as: DE102011054932B4; WO2013060317A1; DE102011054932A1

Abstract

The invention relates to a coordinate measuring apparatus (10), comprising a sensor (30) that is movable relative to a component (12) to be measured. A movable first component (16) carries the sensor (30) and is movably guided on a movable second component (20) along a linear axis (z). The second component (20) is designed as a hinged arm (22), which at a first end (22a) is mounted by a first hinge joint (24) fastened to a supporting structure (14) such as to be rotatable about a first rotational axis (26). At a second opposite end (22b), the hinge arm (22) carries the first component (16). Between the two ends (22a, 22b), the hinge arm (22) has a second hinge joint (34) which has a second rotational axis (36) parallel to the first rotational axis (26) and which divides the hinge arm (22) into a first and a second arm (31, 32), which arms are rotatable independently of each other about the first and the second rotational axis (26, 36), respectively. The hinge arm (22) and the one linearly movable component (16) replace the three linearly guided components required in a customary coordinate measuring apparatus of gantry design having a stationary gantry, which increases the measuring accuracy because said hinge arm (22) and movable component (16) cause substantially fewer errors than extended linear guides.

Description

COORDINATE MEASURING DEVICE

description

The invention relates to a coordinate measuring machine according to the preamble of patent claim 1.

Such a measuring device is known for example from EN ISO 10360-1, November 2000 + Annex AC, December 2002, Section A.5 of the Annex, in which a coordinate measuring machine in portal construction with stationary portal described and shown in Figure A.5. This known coordinate measuring machine has three movable components, which move on three mutually perpendicular guides or linear axes. The known coordinate measuring machine in gantry design with three linear axes has the advantage that also non-round or, more generally, non-rotationally symmetrical components can be measured in a Cartesian coordinate system. A gauge system, or more generally a sensor, is located on the first component, which is perpendicular to the second. The connected assembly of the first and second components moves horizontally to the gantry, which is stationarily located above a frame forming the third component. The component is positioned on the third component, which is a measuring slide that also moves horizontally to the portal.

An advantage of this construction method is the possibility of being able to execute the stationary portal very solid and stiff and therefore correspondingly accurate.

A disadvantage of this design is the need to move the component to be measured in an axial direction. The mass of the component has an influence on the measuring slide and the possible dynamics during the measuring movement. In addition, a sufficiently good attachment of the component on the measuring carriage is required.

In one known from DE 101 1 1 540 A1 measuring instrument instead of the component, the portal itself is movable. This mobile portal coordinate measuring machine also has three linear axes. In contrast to the version with a stationary portal, this design has the advantage that the component does not have to be moved.

Since the entire portal is moved, the construction of the portal must be carried out as easily as possible in order to allow dynamic movements. The lighter design, however, leads to a reduction in the guidance accuracy of the axes located on the portal.

In the gantry design, the edge length of the possible Cartesian measuring volume results directly from the travel of the linear axes. Larger workpieces and thus larger measuring volumes require correspondingly longer linear axes.

The linear axes are designed so that the components are movably guided on tracks, rails or other guide elements. Since the guide rails or tracks in the sense of required accuracy are never quite straight or completely flat, errors in the movement of the components.

These errors are divided into two straightness errors and three rotatory errors. In addition, there is still a length error in the direction of movement. These errors are transmitted to the following axles attached to the moving component. The length and straightness errors are transmitted independently of the lever arm to the following axes and thus also to the touch probe. The rotary errors affect lever arm dependent on the following axes and thus also on the touch probe. With increasing length of the axes, the effort increases significantly in order to achieve a high degree of guidance accuracy. In addition, the effect

Rotatory error on the following axes, due to longer lever arms stronger. It therefore takes a great effort to compensate for such geometric errors. As the measuring volume increases, the expenditure increases disproportionately in order to achieve a high measuring accuracy.

If one considers not only the situation under constant temperature conditions but also when the ambient temperature changes, it must be taken into account that the influence of the temperature changes the geometry of the guides. These changes can sometimes be very complex and can only be detected with complex procedures. In practice, therefore, an air conditioning of gantry-type measuring machines with high-precision requirements is common.

The object of the invention is to provide a coordinate measuring machine of the type mentioned in such a way that it is well suited for general measurement tasks and provides the required accuracy with less effort for large sizes of workpieces.

The object is achieved by a measuring device with the features specified in claim 1.

The coordinate measuring machine according to the invention operates with an articulated arm with two axes of rotation, which replaces the displaceably guided on the support structure second movable component. In addition, this eliminates the displaceably guided third movable component. In the coordinate measuring machine according to the invention, neither the workpiece nor a portal must be moved, it only needs the arm forming the measuring arm to be moved. Rotary axes, as provided by the invention, offer the advantage that high accuracy can be achieved with significantly less effort than with linear axes. The construction with rotation axes offers the further advantage that an enlargement of the measuring volume by an extension of the articulated arm is possible without the rotation axes themselves have to be changed.

If, in the coordinate measuring machine according to the invention, the length of the articulated arm is doubled, a double-radius measuring arm is achieved, thereby achieving a quadruple of the measuring volume. The effort to increase the essvolumens is thus significantly lower than in the described known coordinate measuring machines in gantry design.

The coordinate measuring machine according to the invention has particular advantages in the measurement of rotationally symmetrical components when they are arranged centrally below the first axis of rotation.

In the coordinate measuring machine according to the invention, the Cartesian coordinate system has been replaced by a polar coordinate system in which a certain radius and a certain angle are set by means of the articulated arm. For the rotations can be done around both axes of rotation simultaneously. Rotary axes are much easier to control in terms of accuracy than linear axes. The rotation about the axes of rotation can be done in a range of 360 °.

In the known coordinate measuring machine with movable portal, the portal must be moved with the entire essaufbau. In the known coordinate measuring machine with stationary portal also the workpiece must be moved with the essschlitten. By contrast, in the coordinate measuring machine according to the invention, only the articulated arm needs to be moved, which carries a touch probe at its free end.

Advantageous embodiments of the invention form the subject of the dependent claims. In one embodiment of the coordinate measuring machine according to the invention, the support structure is stationary. Measurement inaccuracies caused by the method of supporting structure as in a coordinate measuring machine with a movable portal are thereby turned off.

In a further embodiment of the coordinate measuring machine according to the invention, the or each sensor is guided on the second component in a linear axis parallel to the two axes of rotation. This can represent a movement in the Z axis of the Cartesian coordinate system.

In a further embodiment of the coordinate measuring machine according to the invention, the second component is guided on the support structure at right angles to the linear axis of the first component. Thus, the movement can be represented as a movement in the X or Y axis as well as in the Z axis of the Cartesian coordinate system.

In a further embodiment of the coordinate measuring machine according to the invention, the second arm is extended beyond the second rotary joint on the side of the second rotation axis opposite the first component. The extension of the second arm allows for weight compensation in the area of the second pivot joint.

In a further embodiment of the coordinate measuring machine according to the invention, the second arm is provided at its opposite to the first component free end with a counterweight. This allows weight compensation with less extension of the second arm.

In a further embodiment of the coordinate measuring machine according to the invention, the first arm with a closer to the support structure arranged third arm is fixedly connected, which is rotatable about the first axis of rotation together with the first arm and carries the second axis of rotation together with the first arm. By this configuration, the accuracy of storage is significantly improved. In this embodiment, there are two above-mentioned Nete further pivot bearing available that further improve the accuracy of the storage of the two axes of rotation, for example, by less game or by achieving the same game with less effort.

In a further embodiment of the coordinate measuring machine according to the invention, the third arm and the second arm each have a free end projecting beyond the first and second rotational axes. This results in a weight balance, which can be avoided by acting on the axes of rotation moments and errors caused by weight shift.

In a further embodiment of the coordinate measuring machine according to the invention, the third arm and the second arm are each provided at its free end with a counterweight. As a result, with shorter arm lengths it is possible to avoid moments acting on the axes of rotation and errors being caused by shifting the weight. Regardless of the angular position of the articulated arm, thus only forces in the axial direction act on the axes of rotation and tilting of the movable structure is completely avoided.

In a further embodiment of the coordinate measuring machine according to the invention, the support structure is a stationary portal. This embodiment is optimal for the storage of the measurement setup with respect to a component to be measured.

In a further embodiment of the coordinate measuring machine according to the invention, the or each sensor is optionally rotatably mounted about a third axis of rotation. This extends the application possibilities of the sensor.

In a further embodiment of the coordinate measuring machine according to the invention, the second component is constructed of material with low thermal expansion. This minimizes the influence of temperature on the accuracy of the coordinate measuring machine. Embodiments of the invention will be described in more detail below with reference to the drawings. It shows:

1 shows a perspective view of a first embodiment of the coordinate measuring device according to the invention with a first embodiment of a sensor and in a first measuring phase,

2 the coordinate measuring machine according to FIG. 1 in a second measuring phase, FIG.

3 shows the coordinate measuring machine according to FIG. 1 in a third measuring phase, FIG.

4 shows the coordinate measuring machine according to FIG. 1 in a fourth measuring phase, FIG.

5 shows the coordinate measuring machine according to FIG. 1 in a fifth measuring phase, FIG.

6 shows the first embodiment of the coordinate measuring machine according to FIG. 1, but with a second embodiment of the sensor and in a first measuring phase, FIG.

7 shows the coordinate measuring machine according to FIG. 6 in a second measuring phase, FIG.

8 shows the coordinate measuring machine according to FIG. 7 in a third measuring phase, FIG.

9 is a perspective view of a second embodiment of the

Coordinate measuring machine according to the invention with a third embodiment of the sensor,

10 is a perspective view of a third embodiment of the coordinate measuring machine according to the invention with the third embodiment of the sensor and in a first measuring phase and

FIG. 11 shows the coordinate measuring machine according to FIG. 10 in a second measuring phase. Fig. 1 shows in perspective a first embodiment of a coordinate measuring machine according to the invention, which is generally designated 10 and has a first embodiment of a sensor, which is generally designated 30. A component to be measured is designated by 12. The component 12 rests on a substructure or frame (not shown). The coordinate measuring machine 10 further comprises a support structure 14, which is designed here as a portal and is arranged stationary on the substructure or frame. Furthermore, the coordinate measuring machine 10 comprises a first component 16, which can be moved up and down in a linear axis z and carries the sensor 30 at its free lower end. The first component 16 is formed in the embodiment shown and described here as a square in cross-section column, which is movable in a guide 18 in the linear axis z.

Coordinate measuring machine 10 further comprises a movable second component designated as a whole by 20, which is designed as an articulated arm designated overall by 22. The articulated arm 22 carries at its free end, ie at the right end in FIG. 1, the guide 18 of the first component 16. At its opposite end, the articulated arm 22 is rotatable with a first pivot 24 about a first axis of rotation 26 on a columnar base 28 mounted, which is fixed at its opposite to the first pivot 24 end to the support structure 14. The articulated arm 22 is secured to the support structure 14 at a first end 22a by the first pivot 24 via the base 28. The articulated arm 22 carries at a second, opposite end 22b the guide 18 with the first component 16. Between the two ends 22a, 22b, the articulated arm 22 has a second pivot 34 with a second axis of rotation 36 parallel to the first axis of rotation 26, the Articulated arm 22 is divided into a first arm 31 and a second arm 32. The second pivot 34 comprises two hinge eyes 34a, 34b which are rotatably connected to each other by a hinge pin 35. The first arm 31 and the second arm 32 are therefore independently rotatable about the first axis of rotation 26 and about the second axis of rotation 36. By mutual relative rotation of the first arm 31 and the second arm 32 of the Radi- us variable, by which the linear axis z, in which the sensor 30 is mounted, is spaced from the first axis of rotation 26.

1 shows the coordinate measuring machine 10 in a first measuring phase, in which the articulated arm 22 is stretched, that is to say the radius has its greatest value. The rotary joints 24 and 34 are each associated with a rotary drive and a rotary encoder, by means of which the articulated arm 22 about the first axis of rotation 26 and the arms 31, 32 about the second axis of rotation 36 rotate in selectable direction by selectable angle. The rotary encoders and rotary drives are conventional components that have not been shown for clarity. Similarly, the first component 16 by means of a guide 18 arranged in the drive device, which is also not shown, in the linear axis z movable. The position and travel distance of the first component 16 may be determined by a highly accurate scale, e.g. a glass scale, are determined, which is also not shown.

By turning the articulated arm 22 about the first axis of rotation 26 and by pivoting the first arm 31 and the second arm 32 about the second axis of rotation 36, a measuring range can be covered, which extends over 360 °. This allows each component contour to be scanned without having to use three movable components, which can be moved on three mutually perpendicular guides or linear axes, as in the case of the portal-type coordinate measuring machine with stationary portal described above. Only the first component 16 of the coordinate measuring machine 10 is linearly movable, so that the component 12 can be scanned at different heights.

In a first embodiment, shown in FIGS. 1-5, the sensor 30 comprises a probe system comprising a stylus 50 and a probe 52. As shown, the stylus 50 may simply be a stylus, which in addition to the linear movability of the sensor 30 in the z-direction in the probe 52 or together with the probe 52 about a third axis of rotation 46 is rotatable. The rotatability of the probe 50 is of more importance in further below. described embodiments of the sensor, in which the button is not simply a single stylus with a ball at the end. In addition, the button 50 can be deflected in the three coordinate directions x, y, z. These deflections of the probe 50 can also be measured. In order to determine a measuring point, the measured values determined or set using the above-mentioned rotary encoders with sensor deflections determined by encoders in the first component 16 can be computed with the correct component to generate a measuring point therefrom, as described, for example, in document DE 101 11 540 A1 is known.

In FIGS. 1 to 5, the coordinate measuring machine 10 is shown in different measuring phases. In a first measurement phase, which is shown in FIG. 1, the radius between the first rotation axis 26 and the third rotation axis 46 has the largest value.

In Fig. 2, which shows a second measuring phase, the articulated arm 22 is bent by 90 ° and the first component 16 shown further Ben ben procedure, so that the button 50 is now with its probe ball on the upper side of the component 12.

For scanning the same can now be the bent articulated arm 22 further pivoted about the first axis of rotation 26. A corresponding third measurement phase is shown in FIG.

In a fourth measuring phase, which is shown in FIG. 4, a right outer surface of the component 12 is scanned with the pushbutton 50, for which purpose the angle by which the articulated arm 22 is bent is again slightly increased and the first component 16 in FIG z-direction has been moved downwards.

Finally, FIG. 5 shows a fifth measuring phase in which an outer front side of the component 12 is measured. Fig. 6 shows the coordinate measuring machine 10 in its first embodiment, but with a second embodiment of a generally designated 30 'sensor having a about the third axis of rotation 46 in a probe 52' rotatable button 50 'with two against each other by 90 ° angled styli. Shown is a first measurement phase in which a right lower outer side of the component 12 is scanned with one of the styli, which is arranged horizontally.

Fig. 7 shows a second measuring phase of the coordinate measuring machine 10 of Fig. 6, in which a front lower side of the component 12, which is located at an upper right projection thereof, is scanned with the same stylus.

8 shows a third measuring phase in which an upper right outer side is to be scanned on the projection of the component 12.

Fig. 9 shows a second embodiment of a coordinate measuring machine, which is generally designated 10 '. The moveable first component 16 carries a third embodiment of a sensor having a stylus 50 "with three styli disposed in a cruciform manner and indicated generally at 30". The button 50 "is rotatable in a probe 52" about the third axis of rotation 46.

In the coordinate measuring machine 10 ', the second arm, here designated 32', on the side opposite the first component 16 side of the second axis of rotation 36 via the second pivot, which is here designated by 34 ', extended out. This extension serves to balance the weight in order to prevent the pivot 34 'from tilting by the second arm 32'. It would be sufficient to dimension the extension of the second arm 32 'so that the weight compensation is effected. It is more convenient, however, to limit the additional length of the second arm 32 'by attaching a counterweight 38 to the free end thereof, as shown in FIG. 10 shows a third embodiment of the coordinate measuring machine, denoted by 10.sup.-## EQU00002 ## Through the embodiment of the coordinate measuring machine 10 "shown, complete weight compensation is achieved, ie not only a weight compensation on the second arm 32 ', but also on the first arm 31 For this purpose, the first arm 31 is fixedly connected to a third arm 31 ', which is arranged closer to the support structure 14 and which is rotatable together with the first arm 31 about the first axis of rotation 26 and, together with the first arm 31, carries the second axis of rotation. which is here designated 36 '. The third arm 31 'is formed like the first arm 31 and accordingly provided with an additional first pivot 24' and an additional second pivot 34 '. The first arm 31 and the third arm 31 'are each connected between the pivot joints 24 and 34 or 24' and 34 'by a rigid connecting part 40 with each other. The articulated arm 22 and the third arm 31 'each carry a counterweight 38' or a counterweight 39 at their free end, that is to say at their left-hand end in FIG. 10. The size of the counterweights is dimensioned such that a perfect balance of weight is achieved. It should be noted that the third arm 31 'in the illustration in Fig. 10 at the top is a continuation or extension of the first arm 31, so no additional separate arm, but together with the first arm 31 forms a rigid arm assembly. This arm assembly could also be designed differently than shown.

10 shows the coordinate measuring machine 10 "in a measuring phase in which the radius between the first rotation axis 26 and the third rotation axis 46 has the largest value.

11 shows the coordinate measuring machine 10 "in a second measuring phase, in which the aforementioned radius has the smallest value.

In the description and in the claims is spoken by parallel or vertical axes. In reality, these axes, being flawed, are mathematically not exactly parallel or perpendicular. The terms parallel or perpendicular are to be understood only in relation to the reasonable and achievable accuracy for the present field of technology.

LIST OF REFERENCE NUMBERS

Coordinate Measuring Machine (1st Embodiment) 'Coordinate Measuring Machine (2nd Embodiment)' Coordinate Measuring Machine (3rd Embodiment)

component

supporting structure

1st component

guide

2nd component

articulated arm

a 1st end

b 2nd end

1st swivel

'further 1st swivel

1st rotation axis

Base

Sensor (1st embodiment)

'Sensor (2nd embodiment)

"Sensor (3rd embodiment)

1st arm

'3rd arm

2nd arm

'2nd arm

2. Swivel

a joint eye

b joint eye

hinge pins

2nd rotation axis

'2nd rotation axis

counterweight

connecting part 3. Rotation axis button

'Button

"Button

probe

'Probe

"Probe

linear axis

Claims

claims

1. coordinate measuring machine with at least one relative to a component to be measured (12) movable sensor (30, 30 ', 30 "),

with at least one movable first component (16) which carries the or each sensor (30, 30 ', 30 ") and is guided on at least one movable second component (20), and

with a support structure (14) on which the second component (20) is guided,

characterized,

in that the second component (20) is designed as an articulated arm (22) which

- Is mounted rotatably about a first axis of rotation (26) at a first end (22a) with a first pivot (24) attached to the support structure (14),

- At a second, opposite end (22 b) carries the first component (16), and

- between the two ends (22a, 22b) has a second pivot (34) with a second axis of rotation (36) parallel to the first axis of rotation (26), the articulated arm (22) in a first and a second arm (31, 32nd ), which are independently rotatable about the first and second rotational axis (26, 36).

2. Coordinate measuring machine according to claim 1, characterized in that the support structure (14) is stationary.

3. Coordinate measuring machine according to claim 1 or 2, characterized in that the or each sensor (30, 30 ', 30 ") on the second component (20) in a direction parallel to the two axes of rotation (26, 36) linear axis (z) out is.

4. Coordinate measuring machine according to one of the preceding claims, characterized in that the second component (20) on the support structure (14) at right angles to the linear axis (z) of the first component (16) is guided.

5. Coordinate measuring machine according to one of the preceding claims, characterized in that the second arm (32) on the one to the first component (16) opposite side of the second rotation axis (36) on the second pivot (34) is extended out.

6. Coordinate measuring machine according to claim 5, characterized in that the second arm (32 ') at its to the first component (16) opposite free end with a counterweight (38) is provided.

7. Coordinate measuring machine according to one of the preceding claims, characterized in that the first arm (31) with a closer to the support structure (14) arranged third arm (31 ') is fixedly connected to the first arm (31) around the first rotation axis (26) is rotatable and together with the first arm (31) carries the second rotation axis (36 ').

8. Coordinate measuring machine according to claim 7, characterized in that the third arm (31 ') and the second arm (32) each have one on the first and second rotational axis (26, 36) projecting free end.

9. coordinate measuring machine according to claim 8, characterized in that the third arm (31 ') and the second arm (32) at its free end in each case with a counterweight (38, 39) are provided.

10. Coordinate measuring machine according to one of the preceding claims, characterized in that the support structure (14) is a stationary portal.

11. Coordinate measuring machine according to one of the preceding claims, characterized in that the or each sensor (30, 30 ', 30 ") is rotatably mounted about a third axis of rotation (46).

12. Coordinate measuring machine according to one of the preceding claims, characterized in that the second component (20) is constructed of material with low thermal expansion.