DE102016203137B4 - Process for measuring a workpiece in a coordinate measuring machine - Google Patents

Abstract

Method for measuring a workpiece (1) with a tactile measuring system (4) in a coordinate measuring machine, the workpiece having a maximum point (M) in the direction of a spatial direction or coordinate (X, Y, Z) in the measuring position in the coordinate measuring machine, the method having- scanning and determining measured values of a workpiece surface (7) along a first path (A1-E1) with the tactile measuring system in a first direction of movement (B1) from a first starting point (A1) to a first end point (E1), wherein the Maximum point (M) on the first path (A1-E1) before the first end point (E1), with a probe shaft (5) of the tactile measuring system (4) with the workpiece surface (7), or with a workpiece surface (7) adjacent tangent, which touches the workpiece surface (7) at the instantaneous contact point (T) of the tactile measuring system, until reaching the maximum point (M) in the first direction of movement, an angle (α1) within a range s from -10° to 90°, which can vary in the course of scanning,- scanning and determining measured values of the workpiece surface along a second path (A2-E2) with the tactile measuring system in a second direction of movement (B2) from a second starting point (A2) to a second end point (E2), with the maximum point (M) on the second path before the second end point (E2), with the probe shaft (5) of the tactile measuring system with the workpiece surface (7), or with a on the workpiece surface (7) tangent, which touches the workpiece surface (7) at the momentary contact point (T) of the tactile measuring system, until reaching the maximum point (M) in the second direction of movement, an angle (β2) within a range of -10 ° to 90°, which can vary in the course of the scanning, with measured values on the first path (A1-E1) in a range from the maximum point (M) to the first end point (E1), or a partial range thereof , are eliminated, and measurement values on the second path (A2-E2) are eliminated in a range from the maximum point (M) to the second end point (E2), or a partial range thereof.

Description

The present invention relates to a method for measuring a workpiece using a tactile measuring system in a coordinate measuring machine. With the method, negative influences due to friction effects on the measurement result can be suppressed or eliminated.

Workpieces that are measured with a probe of a tactile measuring system of a coordinate measuring machine (CMM) often suffer from the so-called stick-slip effect. This effect occurs in particular when a stylus of the tactile measuring system, which has a rod-shaped probe shaft and a probe element attached thereto, is guided in a kind of pushing movement along a workpiece surface during scanning measurement. In this case, a feeler element, for example a feeler ball, is pushed by the feeler shaft in front of it, causing increased friction effects to occur. In this case, the mentioned stick-slip effect occurs more frequently, which is a stick-slip effect or also a frictional vibration and is used to describe the stick-slip of solid bodies moving against one another. The stick-slip effect can occur with solid bodies moving against one another if the static friction is noticeably greater than the sliding friction. The stick-slip effect occurs mainly during the transition from the pulling to the pushing movement of the stylus. In measuring situations, the stick-slip effect often occurs when measuring with a probe that is perpendicular to the longitudinal axis of an element of the workpiece to be measured.

The stick-slip effect can be minimized by lubrication, but can rarely be eliminated. However, this is usually not possible in measurement technology.

The stick-slip effect is mainly reflected in outliers in the form measurement and is very dependent on the scanning speed. In order to avoid the effect, lower scanning speeds are selected in practice, which, however, increases the measurement time considerably.

Measurement distortion caused by the stick-slip effect often leads to discussions between quality control and production, resulting in unnecessary and costly service calls or the inadvertent classification of a workpiece as a scrap part.

DE 10 2008 049 751 A1 discloses that stick-slip effects are observed, particularly when using probes in scanning mode, i.e. the probe element that acts on the surface of the workpiece to be scanned with the probing force repeatedly briefly sticks or “sticks” to the surface of the workpiece, followed by a time interval in which the scanning element follows the planned scanning path with a correspondingly higher speed. These stick-slip time intervals often alternate at high frequency. Stick-slip effects are intensified by rough surfaces and by the stimulation of vibrations by the coordinate measuring machine and/or parts of the probe. The probe element of the probe is often attached to an elongate element, the stylus shaft. Mostly is after DE 10 2008 049 751 A1 at least the part of the shank to which the probe element is directly attached is straight, ie has a longitudinal axis which runs in a straight direction towards the probe element. If the probe element is pulled over the workpiece surface during scanning in such a way that the force component responsible for maintaining the scanning movement runs at least partially away from the probe element in the longitudinal direction of the shaft, “stick” phases are less likely to be of shorter duration and/or deviates less from the mean scanning speed. This state is referred to as "pulling" the button. The reverse state can be referred to as "pushing". When pushing, the force component runs in the longitudinal direction of the shaft towards the probe element. As the stylus is pulled, the stiffness of the stylus increases in the direction tangential to the surface of the workpiece up to the point where the force vector leaves the friction cone. Ideally, the force vector then remains permanently outside the friction cone, ie there are no "stick" phases in which the probe element gets stuck on the surface. On the other hand, when the probe is pushed, the rigidity of the sensor decreases in the tangential direction. In the immediately following phase, the contact element covers a relatively large distance on the surface in a short time, so that the contact force vector falls back into the friction cone and it gets stuck. To solve this problem, in DE 10 2008 049 751 A1 proposed to rotate the workpiece, taking into account the directional dependence of the flexibility, and to use a rotary table for this purpose, on which the workpiece to be measured is arranged. By turning the turntable with the workpiece, the surface normal can be oriented differently by a measuring point on the surface of the workpiece and generally also be positioned differently.

The object of the invention is to provide a solution to the above-mentioned problem of the stick-slip effect.

• - Scannen und Ermitteln von Messwerten einer Werkstückoberfläche entlang einer ersten Wegstrecke mit dem taktilen Messsystem in einer ersten Bewegungsrichtung von einem ersten Anfangspunkt bis zu einem ersten Endpunkt, wobei der Maximumpunkt auf der ersten Wegstrecke vor dem ersten Endpunkt liegt, wobei ein Tasterschaft des taktilen Messsystems mit der Werkstückoberfläche, oder mit einer an der Werkstückoberfläche anliegenden Tangente, welche die Werkstückoberfläche an dem momentanen Antastpunkt des taktilen Messsystems berührt, bis zum Erreichen des Maximumpunkts in der ersten Bewegungsrichtung einen Winkel innerhalb eines Bereiches von -10° bis 90° einschließt, der im Verlauf des Scannens variieren kann,
• - Scannen und Ermitteln von Messwerten der Werkstückoberfläche entlang einer zweiten Wegstrecke mit dem taktilen Messsystem in einer zweiten Bewegungsrichtung von einem zweiten Anfangspunkt bis zu einem zweiten Endpunkt, wobei der Maximumpunkt auf der zweiten Wegstrecke vor dem zweiten Endpunkt liegt, wobei der Tasterschaft des taktilen Messsystems mit der Werkstückoberfläche, oder mit einer an der Werkstückoberfläche anliegenden Tangente, welche die Werkstückoberfläche an dem momentanen Antastpunkt des taktilen Messsystems berührt, bis zum Erreichen des Maximumpunkts in der zweiten Bewegungsrichtung einen Winkel innerhalb eines Bereiches von -10° bis 90° einschließt, der im Verlauf des Scannens variieren kann,

wobei Messwerte auf der ersten Wegstrecke in einem Bereich vom Maximumpunkt bis zum ersten Endpunkt, oder einem Teilbereich davon, eliminiert werden, und Messwerte auf der zweiten Wegstrecke in einem Bereich vom Maximumpunkt bis zum zweiten Endpunkt, oder einem Teilbereich davon, eliminiert werden.From the invention, a method for measuring a workpiece with a tactile measuring system in a coordinate measuring machine according to claim 1 is presented, wherein the workpiece in Measuring position in the coordinate measuring machine has a maximum point in a spatial direction or a coordinate, the method having

• - Scanning and determining measured values of a workpiece surface along a first path with the tactile measuring system in a first direction of movement from a first starting point to a first end point, the maximum point on the first path lying before the first end point, with a stylus of the tactile measuring system of the workpiece surface, or with a tangent on the workpiece surface, which touches the workpiece surface at the instantaneous contact point of the tactile measuring system, encloses an angle within a range of -10° to 90° in the first direction of movement until the maximum point is reached, which in the course of scanning may vary,
• - Scanning and determining measured values of the workpiece surface along a second path with the tactile measuring system in a second direction of movement from a second starting point to a second end point, with the maximum point on the second path lying before the second end point, with the stylus of the tactile measuring system of the workpiece surface, or with a tangent on the workpiece surface, which touches the workpiece surface at the instantaneous contact point of the tactile measuring system, encloses an angle within a range of -10° to 90° in the second direction of movement until the maximum point is reached, which in the course of scanning may vary,

wherein measured values on the first path are eliminated in a range from the maximum point to the first end point, or a sub-range thereof, and measured values on the second path are eliminated in a range from the maximum point to the second end point, or a sub-range thereof.

With the method described above, the stick-slip effect can be effectively avoided or minimized or eliminated.

Furthermore, relatively high scanning speeds are possible with the method, with good measurement quality at the same time.

The first direction of movement is preferably opposite to the second direction of movement.

According to the above procedure, the scanning direction and the angle between the stylus shaft and the workpiece surface are selected in such a way that the stick-slip effect does not occur or only occurs to a minimum. In a method in which two distances and two directions are used, different scanning directions can be combined within one measurement task. A total scan can thus be composed of two partial scans.

If the workpiece has a flat surface, which can form part of a path or the entire path, the angle mentioned between the probe shaft and the workpiece surface can be determined. If the workpiece has a curved surface, the tangent mentioned can be used to determine the angle.

An instantaneous touch point is continuously changing over the course of the measurement, which is why it is a touch point at a specific point in time and is referred to as a "instantaneous" touch point.

The angle mentioned means the angle in the direction of movement, in other words the angle that is formed in the direction of movement in front of the stylus shaft, i.e. in front of the stylus shaft between the workpiece surface (or tangent) and the stylus shaft.

Methods according to the invention can be applied to all types of measurement tasks, such as when measuring curved or inclined flat surfaces, with the application being particularly advantageous for curved surfaces and, in particular, surfaces that run in the shape of a circular arc.

With the method according to the invention, a high scanning speed and a minimized or eliminated stick-slip effect can be achieved simultaneously.

Said first and second starting point preferably lie in front of an assigned (first or second) end point in a considered spatial direction or coordinate direction. In a special case, the considered coordinate direction or spatial direction points upwards and can be defined as the Z-direction. In this case, the starting point mentioned is lower in this coordinate direction or in the Z-direction than an assigned end point. It can therefore be scanned on a first path and on a second path from bottom to top, along a workpiece surface. In another special case, the coordinate direction or spatial direction under consideration is horizontal. In this case, a starting point is in horizontal direction in front of an associated end point.

The fact that the stylus shank forms an angle of -10° to 90° with the workpiece surface in the first direction means, in other words, that the stylus shank is pulled along the workpiece surface in an inclined position (i.e. not perpendicular) to the workpiece surface. The touching element is the feeler element that is in contact with the surface of the workpiece. The same applies to guiding the probe shaft in the second direction.

The specified angle range is to be understood in such a way that the entire angle range does not have to be set or covered during a measurement, but any sub-range or even just a single angle can be covered or set, for example +20° to 90°. The stated end points of the range thus represent end points of a possible maximum range and not necessary end points or values in any process configuration. In the case of curved surfaces, the angle range depends, among other things, on where the start and end points are set and how the curvature progresses.

The sign of the angle is defined as follows: A positive sign means that the tangent mentioned is closer to the workpiece surface than the stylus shaft. A negative sign means that the stylus is closer to the workpiece surface than the tangent. This is explained further below using an exemplary embodiment. The negative sign is possible if a tangent is used as a basis for determining the angle on curved surfaces. If a (straight running) workpiece surface itself is used as a basis for determining the angle, the angle is 0 to 90°. As an alternative to the angle range specification with sign explained above, the amount of the angle can be specified as 0° to 90° in the method according to the invention. Consequently, in the process, the stylus shaft closes an angle of 0° with the workpiece surface, or with a tangent on the workpiece surface, which touches the workpiece surface at the current contact point of the tactile measuring system, until the maximum point is reached in the first direction of movement up to 90°, which can vary in the course of scanning,

A mentioned maximum point can be a local or a global maximum point. A workpiece can have several maximum points, with one of these maximum points being selected in the method. Of course, the process can be repeated as desired at other maximum points, in other areas of the workpiece surface. A global maximum point is a maximum point on a workpiece surface viewed over the entire workpiece surface in a spatial or coordinate direction. A local maximum point is a maximum point on a workpiece surface in a region of the workpiece surface in a spatial or coordinate direction. It goes without saying that other global or local maximum points can be present depending on the measuring position of the workpiece or depending on the spatial or coordinate direction.

A maximum point is in particular a maximum on the surface of a measuring element of the workpiece. A measuring element is understood here to mean a substructure or region of a workpiece to be measured, for example an individual cam in the case of a camshaft.

A route can have curved and/or linear sections. According to the language used in this invention, a line has the property, compared to a curve, that it extends straight, ie has no curvature. One or more curves can be combined with one or more lines. A particularly advantageous application of the method relates to curved structures or surfaces, in particular arc-shaped.

In one embodiment of the invention, a method is specified, wherein the maximum point on the first path is before the first end point and from the maximum point to the first end point of the probe shaft with the workpiece surface, or with a tangent to the workpiece surface, which the workpiece surface at the instantaneous Touch point of the tactile measuring system touches, in the first direction of movement includes an angle of greater than 90 °, which can vary.

Furthermore, in one embodiment, a method is specified that is analogous to the previous embodiment, with the maximum point on the second path before the second end point and from the maximum point to the second end point of the stylus with the workpiece surface in the second direction of movement at an angle of greater than 90 ° Includes, which may vary.

In the embodiments described above, a stick-slip effect can occur or be increased between the maximum point and the first or second end point. Measured values in the section between the maximum point and the first/second end point can be eliminated.

In one embodiment, a method is specified, wherein the first route and the second route and the second route connect to one another or overlap in such a way that a total route is formed from both routes. To put it another way, in this embodiment the first distance and the second distance are put together and form an overall measurement profile or an overall distance. The method thus obtains measured values along the entire route. In particular, in this embodiment, the first and second routes are selected to meet at the first endpoint or the second endpoint, or to partially overlap such that the first endpoint is on the second route and the second endpoint is on the first route .

In particular, a method is specified, wherein the first route and the second route between the first end point and the second end point, which lie on the total route, are congruent for the total route.

Said total distance is preferably continuous. The total route can be composed of one or more line segments and/or one or more curve segments, which also applies to the first route and the second route. A steady progression means that there are no jumps or abrupt changes of direction within the total distance. In the event of an overlap or in an overlapping section, the first route and the second route are congruent, i.e. congruent over a course section.

In a special embodiment, the total route forms a geodesic between the first starting point and the second starting point. The geodesic is the shortest connection between the first and second starting point along the workpiece surface.

In the method, measured values are eliminated on the first stretch in a range from the maximum point to the first end point, or a sub-range thereof. Another term for this is "delete". Not all measured values have to be eliminated here. For example, only obviously erroneous measured values that exceed a defined error limit, for example, or measured value outliers, can be eliminated. This variant makes sense when the maximum point of the first path is before the first end point and in particular when the stylus encloses an angle of greater than 90° with the workpiece surface in the first direction of movement from the maximum point to the first end point. In this case, as already mentioned above, a stick-slip effect can arise or be intensified in the section from the maximum point to the first end point. By eliminating the measured values in the manner described above, measured values that are influenced by a stick-slip effect and are therefore distorted or falsified can be eliminated. This procedure can also be advantageously used in particular when a first route mentioned and a second route overlap, as mentioned above. A section from the first maximum point to the first end point is preferably a section that overlaps with a section of the second route, in particular with a section of the second route that lies before the maximum point. Thus, measured values on the second path can be used for the measurement result, which are in the direction of movement along the second path before the maximum point and are not influenced by a stick-slip effect, and measured values on the first path that are in the direction of movement on the first path behind the maximum point are not taken into account for the acquisition of measured values along the entire distance, since they are faulty due to the stick-slip effect. A total distance, or a measurement result along it, can thus be freed from erroneous measurement values.

Analogously, measured values on the second path are eliminated in a range from a maximum point to a first end point, or a sub-range thereof. The above applies in an analogous way, only viewed from a different perspective. The maximum point is on the second path before the second end point and from the maximum point to the second end point the stylus encloses an angle of greater than 90° with the workpiece surface in the second direction of movement. Accordingly, a stick-slip effect occurs or is intensified in this section of the second path.

As already mentioned, high scanning speeds are possible with the method according to the invention, with good measurement quality at the same time, ie correct imaging of the structure to be measured, even without using a filtering of measurement values. In one variant of the invention, the scanning speed of the tactile measuring system is at least 5 mm/s, preferably at least 10 mm/s, even more preferably at least 15 mm/s, most preferably at least 20 mm/s. A preferred upper limit of the scanning speed is 40 mm/s, more preferably 30 mm/s. These upper limits may be combined with any of the lower limits mentioned. The scanning speed is the movement speed of the measuring system, or the probe shaft or a probe element along the workpiece surface.

• 1 ein Werkstück in Messlage in einem Koordinatenmessgerät,
• 2 das Werkstück aus 1 in einer Ansicht von schräg oben,
• 3a, b Messergebnisse, die mit einem herkömmlichen Messverfahren erhalten werden,
• 4 einen Messablauf nach dem erfindungsgemäßen Verfahren,
• 5 Messwerte in einem Überlappungsbereich gemäß einem erfindungsgemäßen Verfahren und
• 6a, b, c Messergebnisse aus dem erfindungsgemäßen Verfahren (6a, 6b) und aus einem Verfahren nach dem Stand der Technik (6c) im Vergleich.

The invention is described below using exemplary embodiments. Show it:

• 1 a workpiece in measuring position in a coordinate measuring machine,
• 2 the workpiece 1 in a view from above,
• 3a, b Measurement results obtained with a conventional measurement method,
• 4 a measurement sequence according to the method according to the invention,
• 5 Measured values in an overlapping area according to a method according to the invention and
• 6a, b , c Measurement results from the method according to the invention (6a, 6b) and from a method according to the prior art (6c) in comparison.

1 shows a typical measuring task on a workpiece 1, which is placed in a measuring position in a coordinate measuring machine. The workpiece 1 lies on the base 2, which in turn is placed on the measuring table 3 and is fixed to the base 2 by devices not shown in detail. The workpiece 1 has a round cross-section and is disc-shaped or cylindrical.

A tactile measuring system 4 can be seen to the left of the workpiece, which has the stylus 5 and the probe element (probe) 6 in the form of a probe ball.

In 2 the measuring task on the workpiece 1 is shown. The workpiece surface 7, here a cylindrical surface, is to be measured in scan mode, specifically from point A1 to point A2 (or vice versa).

In a conventional method, the feeler ball 6 is placed at the point A1 and moved to the point A2 while constantly touching the lateral surface 7. Points A1 and A2 can lie on the equator of workpiece 1, i.e. somewhat lower than in 2 drawn for the sake of clarity. When moving in one direction, a stick-slip effect occurs increasingly from the highest point M, which is a maximum point, which is noticeable in the measurement result, as in 3a and 3b shown. The workpiece 1 and the outer surface 7 are shown there. In 3a and 3b a scanning speed of 20 mm/s (speed of movement of the scanning element 6) was selected in each case. In contrast to 3a were in 3b the measurement results are filtered and outliers are eliminated. In the ideal case, the measured values form the contour of the lateral surface 7, that is to say in this case an arc of a circle. It is clear to see that the results are out 3a and 3b are far from this ideal. Better results could be obtained at lower scan speeds, such as 5 mm/s or 2 mm/s, preferably with filtering and outlier elimination. The lower the scan speed, the better the results obtained, but the longer the measurement time.

The method according to the invention is 4 with reference to 2 presented. In the method according to the invention, the measurement task is divided into two partial scans. A first partial scan takes place on the curved path between points A1 and E1, where A1 is a first starting point and E1 is a first ending point. The first route is designated A1-E1 according to its start and end point. The feeler ball 6 is moved in the direction of movement B1 along the distance A1-E1, touching the lateral surface 7 . The maximum point M, which is the highest point of the workpiece 1 in the measuring position in the Z direction, is on the path A1-B1 before the point E1.

In the second partial scan, scanning takes place from the starting point A2 to the end point E2, in the direction of movement B2. The scan takes place along the route A2-E2. It can be seen that the direction of movement B2 is opposite to the direction of movement B1. The maximum point M also lies on the route A2-E2.

It can be seen that the routes A1-E1 and A2-E2 overlap, specifically in an overlapping area that extends from the end point E1 of the first route to the end point E2 of the second route. The overlapping area is indicated by a dash-dot line. The total distance A1-A2, which has the mentioned overlapping area E1-E2, is formed from the two partial scans or the two distances A1-E1 and A2-E2. Alternatively, the first partial scan could be from A1 to M and the second partial scan from A2 to M, so that both paths A1-M and A2-M would meet at point M. In a further variant, the meeting point of the two partial scans can also be at a point next to M. I.e. the meeting point does not necessarily have to be the highest point M on the workpiece surface 7.

In 2 It can also be seen that the total distance A1-A2 is the shortest connection between the points A1 and A2 along the workpiece surface 7 and is therefore a geodesic. It is alternatively possible to bulge the total distance, for example forwards or backwards in the viewer's line of sight, so that no shortest total distance is formed between points A1 and A2. Nevertheless, the total distance would go through a maximum that would only be shifted forwards or backwards accordingly. Any deviations from a geodesic are therefore possible.

In 4 shows an essential aspect of the method according to the invention, namely the angle of the probe shaft 5 to the workpiece surface 7. Since the workpiece surface 7 is curved in this example, tangents are used as a basis for defining the angle in this special case, which are drawn in as dashed lines and each go through the current touch point of the probe element 6. In the case of a workpiece surface that extends in a straight line, for example an inclined plane, a tangent does not have to be taken as a basis, but the workpiece surface itself can be used to determine the angle between the workpiece surface and the stylus 5 . In 4 an instantaneous touch point T is shown on the right in an enlarged representation, at which the touch ball 6 touches or touches the surface 7 . It goes without saying that the instantaneous touch point T changes continuously in the course of the scanning movement and, in this example, moves along the defined paths A1-E2 or A2-E2, which is why it is referred to as the “instantaneous” touch point.

Shown are four points of contact of the probe element 6, namely at the starting point A1, the end point E1, the starting point A2 and the end point E2, which was previously based on 2 were explained.

As mentioned, the first partial scan takes place in the direction of movement B1 from point A1 to point E1. The stylus and the feeler element 6 are shown in the corresponding situations. When the starting point A1 is touched by the feeler element 6, the angle α1 is formed between the tangent and the feeler pin 5. The angle α1 is considered in the direction of movement B1. The angle α1 is less than 90°. If the probe element 6 reaches the maximum point M, the angle α1 is exactly 90°. If the feeler element is moved beyond the maximum point M in the direction of movement B1, an angle a2 of greater than 90° is formed in the direction of movement B1 between the feeler pin 5 and the corresponding tangent at the point of contact. The angle a2 at the end point E1 is in 4 shown. Both the angle α1 and the angle a2 are angles in the direction of movement B1, ie the angle in front of the stylus 5, viewed in the direction of movement. It is obvious that the angles α1 and α2 change continuously as the feeler element and the feeler pin 5 move along the surface 7 .

In the second partial scan, which runs from point A2 to point E2, the angles β1 and β2 are formed. In an analogous manner, the angle β1 from point A2 to point M is a maximum of 90° and is greater than 90° between point M and E2.

left in 4 the setting of a negative angle a3 is shown in a detail. In this measurement situation, the probe ball is set deeper than in 4 , Center, namely below what is referred to here as the equator of the workpiece 1, which is indicated by a dashed-dotted line. This pose of the feeler shaft 5 and the feeler ball 6 is possible due to the relatively large diameter of the feeler ball 6 relative to the diameter of the feeler shaft 5 . Of course, the possibility of this position also depends on the radius of curvature of the workpiece surface. In the shown pose of the stylus shaft 5 and the stylus ball 6, the tangent where the angle is determined is further away from the surface of the workpiece 1 than the stylus shaft 5 and the angle is given a negative sign by definition. The angles α1 and a3 in 4 are the same or about the same in magnitude, but α1 has a positive sign, a3 has a negative sign.

In 5 measured values obtained by the method according to the invention are shown in the overlapping area E1-E2. In the middle of 5 is the maximum M. The view is the same as in 2 or 4 . It can be seen that measured value distortions occur in the overlapping area E1-E2 due to stick-slip effects. The measured value distortions on the right-hand side occur as a result of the movement of the scanning element 6 from the maximum point M to the end point E1 in the direction of movement B1. The distortions shown on the left, which are approximately symmetrical to the distortions shown on the right, occur because the probe element 6 is guided in the direction of movement B from point M to point E2. In other words, the distortions appear where the angle α2 and the angle β2 are set, each larger than 90°.

It is therefore preferable in the method to eliminate measurement values obtained in movement direction B1 between point M and point E1, as well as measurement values obtained in movement direction B2 between point M and point E2. The measurement result in the overlapping area is based on the measurement values in the direction of movement B1 between E2 and M and in the direction of movement B2 between E1 and M. In other words, only measurement values are taken into account for which an angle α1 and an angle β1 are set.

In 6a and 6b results obtained with the method according to the invention are shown. The results off 6b are out on the results 6a filtered again. However, both results show an almost perfect mapping of the arcuate contour of the surface 7 of the workpiece 1. In comparison, FIG 6c a result according to conventional methods that has already been 3b was mapped. A significantly poorer imaging result is obtained with the method according to the prior art.

Claims (8)

Method for measuring a workpiece (1) with a tactile measuring system (4) in a coordinate measuring machine, the workpiece having a maximum point (M) in the direction of a spatial direction or coordinate (X, Y, Z) in the measuring position in the coordinate measuring machine, the method having - Scanning and determining measured values of a workpiece surface (7) along a first path (A1-E1) with the tactile measuring system in a first direction of movement (B1) from a first starting point (A1) to a first end point (E1), where the maximum point (M) is on the first route (A1-E1) before the first end point (E1), wherein a probe shaft (5) of the tactile measuring system (4) touches the workpiece surface (7) or a tangent that rests on the workpiece surface (7) and touches the workpiece surface (7) at the instantaneous touch point (T) of the tactile measuring system until to reach the maximum point (M) in the first direction of movement encloses an angle (α1) within a range of -10° to 90°, which can vary in the course of the scanning, - Scanning and determining measured values of the workpiece surface along a second path (A2-E2) with the tactile measuring system in a second direction of movement (B2) from a second starting point (A2) to a second end point (E2), where the maximum point (M) is on the second stretch before the second end point (E2), whereby the stylus shaft (5) of the tactile measuring system touches the workpiece surface (7) or a tangent that rests on the workpiece surface (7) and touches the workpiece surface (7) at the current contact point (T) of the tactile measuring system until the maximum point (M) in the second direction of movement encloses an angle (β2) within a range of -10° to 90°, which can vary in the course of the scanning, wherein measured values on the first route (A1-E1) are eliminated in a range from the maximum point (M) to the first end point (E1), or a partial range thereof, and Measured values on the second route (A2-E2) in a range from the maximum point (M) to the second end point (E2), or a portion thereof, are eliminated. procedure after claim 1 , whereby from the maximum point (M) to the first end point (E1) of the probe shaft (5) with the workpiece surface (7), or with a tangent to the workpiece surface (7) which touches the workpiece surface at the instantaneous touch point (T) of the tactile Measuring system touches, in the first direction of movement (B1) includes an angle (a2) of greater than 90 °, which can vary. procedure after claim 1 or 2 , whereby from the maximum point (M) to the second end point (E2) the stylus shaft (5) touches the workpiece surface (7), or a tangent lying on the workpiece surface (7) which touches the workpiece surface (7) at the instantaneous touch point (T ) of the tactile measuring system touches an angle (β2) of greater than 90° in the second direction of movement (B2), which can vary. Method according to one of the preceding claims, wherein the first route (A1-E1) and the second route (A2-E2) connect to one another or overlap in such a way that a total route (A1-A2) is formed from both routes. procedure after claim 4 , where the total distance (A1 -A2) has a continuous course. Procedure according to one of Claims 4 or 5 , wherein in the total distance (A1-A2) the first distance (A1-E1) and the second distance (A2-E2) between the first end point and the second end point, which are on the total distance (A1-A2), are congruent. Procedure according to one of Claims 4 - 6 , where the total distance (A1-A2) is a geodesic between the first starting point (A1) and the second starting point (A2). Method according to one of the preceding claims, wherein the scanning speed of the tactile measuring system is at least 5 mm/s.

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