DE10126753B4 - Method for increasing the accuracy of coordinate measuring machines and machine tools - Google Patents

Abstract

Method for increasing the accuracy of coordinate measuring machines and machine tools in the,
a) at least one additional measuring system is integrated into the coordinate measuring machine or the machine tool in addition to the measuring systems of the track axes,
b) at least one additional geometric information about the actual position or the actual travel distance of a coordinate measuring machine or a machine tool is obtained from this additional measuring system,
c) evaluating one or more additional geometric information together with the scale signals and / or probe signals of the coordinate measuring machine or the machine tool and formulating them in an overdetermined system of equations,
d) the additional geometric information is weighted according to the assumed or calculated uncertainty of this information in the mathematical solution of the equation system,
e) in solving the overdetermined system of equations, the residuals of all equations are mathematically minimized.

Description

The The invention relates to a method for increasing the measurement accuracy of coordinate measuring machines and the manufacturing accuracy of machine tools.

Coordinate measuring machines and machine tools are in big in the industry Number in use. They usually consist of three displacement axes, which are built on each other so that they are a Cartesian coordinate system span. You can but also have a kinematics that builds on rotary axes: In the Automotive industry are z. B. also industrial robots as machine tools for the Machining or measuring devices for the Measurement of components used. The position of the individual axes is generally determined by a measuring system. These Measuring systems can Standards with reading heads or Angular encoder, in special cases are also interferometric length measuring systems used. The accuracy of these measuring systems determines the basic accuracy the coordinate measuring machines or the machine tools. Further error influences come however, since coordinate Measuring Machines and machine tools inevitably the so-called Abbe'sche Violate principle, according to which the object to be measured or to be manufactured should lie in one axis with the measuring system. This causes geometry errors the carriage, in particular tilting, to other measuring or production deviations. Naturally, these influences are ever greater bigger the Offset between measuring system and measuring object is.

Even though coordinate Measuring Machines already have a considerable accuracy today applications where this is not enough. This is z. B. the case when calibrating reference standards such as step dimensions or Form normals [1]. Here is the state of the art usually a Laser measuring system arranged close to the measuring object so that it is parallel is used to a travel axis of the coordinate measuring machine. It will be only the measured values of the laser measuring system were evaluated, but not the the built-in measuring systems. The coordinate measuring machine functions So only as a displacement instrument, not more as a measuring device. The laser measuring system is therefore the sole and not additional measuring system, an integration The laser measuring system does not take place. This arrangement requires a high expenditure on equipment and lengthy adjustments of the Laser measuring system and the measurement object. Besides, this solution is up the application is limited to only a few, one-dimensional measurement tasks.

In the DE 19752290 A1 Methods are described by means of which position and angle sensors can be used for position and position determination independently of the travel axes. The combinations of the different sensor classes are described, which allow parallel use of an independent of the movement axes determination of position or rotation. The inventive approach to mathematically optimize existing information from the measuring systems in the axes for the purpose of accuracy increase with information from additional measuring means, is in DE 19752290 A1 not described. Rather, the sensor combinations are explicitly worked out, which are necessary for a position or angle determination, which is independent of the measuring systems in the machine axes. The measured values of the machine tool are retained only for those point-to-point relationships that can not be measured with the aid of the additional measuring systems.

In the DE 3941144 A1 a coordinate measuring machine is shown, in which the geometry of a component can be detected with a plurality of pivoting video cameras, without a camera is moved through the measuring volume.

spatial Positions become from the pairwise photogrammetric evaluation measured values from two video cameras. It will not run, like a third or fourth video camera as an additional measuring means for reduction the uncertainty of the position determination can be used. The third and fourth camera are used to fully capture the component geometry, there with a measuring system with only two cameras due to occlusions In general, not all points on the component are measured can.

Since the early 1980s, many research institutes have been working on the development of coordinate measuring systems for use in arbitrary measuring tasks, in which the metrological information is again taken from separate measuring systems. These measuring systems work according to the principle of multilateration [2 JP 07239209 A ]. At least three (usually four) laser interferometric measuring systems are used in this solution. These are all automatically tracked to a reflector that is moved around the measuring object by the "coordinate measuring machine." The positions of the reflector - and Thus, the coordinates of the measurement object - are thus determined exclusively by the signals of the interferometer, so the coordinate measuring machine acts again only as a displacement instrument. In the realization of this solution, however, great structural difficulties occur. In particular, the reflector, which should ideally ensure the reflection of all measuring systems from one point independently of the direction of the measuring beams, can not yet be realized satisfactorily technically.

A Further development in connection with the swiveling length measuring systems with coordinate measuring machines or machine tools used is in a German Patent application [3] described. It is characterized by a single Length measuring system creates a network of points that is used to determine geometry deviations for coordinate measuring machines or machine tools can be used. Unlike that inventive method However, the measuring system is not online during the measurement or production in conjunction with the measuring systems of the coordinate measuring machine or the machine tool used. So it does not increase the accuracy, but to determine the accuracy of the examined coordinate measuring machine or the examined machine tool.

Methods of balance calculation have long been used in coordinate metrology to best fit measured points to standard geometric shape elements such as circle, sphere, plane, cylinder, and so on. They are part of the evaluation software of many coordinate measuring machine manufacturers. In the DE 19600002 A1 a special procedure is carried out. This integral method for on-line geometry testing of multi-form workpieces is merely to provide a more reliable indication as to whether all measured points of a workpiece geometry match a given target geometry, taking tolerance zones into account.

development a general procedure for task-specific increase the measuring accuracy of coordinate measuring machines and the manufacturing accuracy of machine tools, without tedious adjustment of an additional Measuring system and alignment of the measurement object gets along.

solution

• a) dass ergänzend zu den Messsystemen der Verfahrachsen mindestens ein zusätzliches Messsystem (4) in das Koordinatenmessgerät oder die Werkzeugmaschine integriert wird,
• b) dass aus diesem zusätzlichen Messsystem (4) mindestens eine zusätzliche geometrische Information über die Ist-Position oder den Ist-Verfahrweg eines Koordinatenmessgeräts oder einer Werkzeugmaschine (1) gewonnen wird;
• c) dass eine oder mehrere zusätzliche geometrische Informationen zusammen mit den Maßstabssignalen und/oder Tastersignalen des Koordinatenmessgeräts oder der Werkzeugmaschine (1) ausgewertet und in einem überbestimmten Gleichungssystem formuliert werden,
• d) dass die zusätzlichen geometrischen Informationen entsprechend der angenommenen oder errechneten Unsicherheit dieser Informationen in der mathematischen Lösung des Gleichungssystems gewichtet werden,
• e) dass bei der Lösung des überbestimmten Gleichungssystems die Residuen aller Gleichungen mathematisch minimiert werden.

The object is achieved according to the invention

• a) that, in addition to the measuring systems of the track axes, at least one additional measuring system ( 4 ) is integrated into the coordinate measuring machine or the machine tool,
• b) that from this additional measuring system ( 4 ) at least one additional geometric information about the actual position or the actual travel of a coordinate measuring machine or a machine tool ( 1 ) is won;
• c) that one or more additional geometric information is evaluated together with the scale signals and / or probe signals of the coordinate measuring machine or the machine tool (1) and formulated in an overdetermined system of equations,
• d) that the additional geometric information is weighted according to the assumed or calculated uncertainty of this information in the mathematical solution of the equation system,
• e) that in solving the overdetermined system of equations the residuals of all equations are mathematically minimized.

epiphany

According to the invention, in addition to the existing measuring systems of the track axes, at least one additional measuring system ( 4 ) in the coordinate measuring machine or the machine tool ( 1 ) integrated. As additional measuring systems ( 4 ) come z. As length measuring systems such as laser interferometer and angle measuring systems such as incremental encoder in question.

By the integration of at least one additional measuring system becomes the Measuring accuracy of the coordinate measuring machine or the machine tool increased in one or more axes. The increase of Measurement accuracy is achieved by both the readings of existing Measuring systems and the measured values of other measuring systems together be used to process the measurement task; Readings available Measuring systems are thus not easily measured by other measuring systems replaced. It is according to the invention rather, so that all measured values of the existing measuring systems are used to perform the measurement.

The hardware integration of the additional measuring systems ( 4 ) takes place in such a way that these are usually stationary to the measurement object or workpiece ( 5 ) are mounted on the respective machine, so that the measuring systems, the relative movement between the measuring object or the workpiece ( 5 ) and the probe ( 2 ) on the coordinate measuring machine or the tool on the machine tool (Note: The attachment of the additional measuring systems must be carried out so that between additional measuring system and probe or tool ( 2 ) is at least one member of the kinematic chain). Preferably, the at least one additional measuring system is integrated electronically and in terms of information technology in the control and EDP of the coordinate measuring machine or the machine tool.

The hardware integration of the measuring system requires no special orientation. It is thus without big ones Effort feasible. Furthermore limited only the size of the additional Measuring system, the freedom of movement of the coordinate measuring machine or the machine tool.

Together with the following mathematical integration into the Computerized this method is suitable for increasing the accuracy in any measurement or manufacturing tasks and is therefore not only applicable for special tasks. Furthermore the construction effort is so low that in addition to the re-equipment of devices also the retrofitting existing facilities economically and technically sensible is.

Due to the information technology integration of the at least one additional measuring system ( 4 ) is in the coordinate measuring machine or the machine tool ( 1 ) the position of the probe / tool ( 2 ) p not only by the measuring systems in the axes ( 3 ), but also by another measured value of an additional measuring system ( 4 ) derived. Is this measuring system z. B. a length measuring system that measures the distance e between two reference points, of which a reference point r = (x _r , y _r , z _r ) fixed to the measurement object ( 5 ) and the other stationary to the probe / tool ( 2 ) p, results in an absolutely measuring length measuring system as additional determination equation | p - r | = e. If the measuring system is a relatively measuring system, an additional, constant offset Δe can be taken into account for all measured lengths. This then yields | p - r | = e + Δe as additional equation of determination.

• A) Die Position r wird durch Antastung von Referenzpositionen an dem zusätzlichen Messsystem (4) bestimmt. Die Antastung erfolgt durch das Koordinatenmessgerät bzw. die Werkzeugmaschine (1), wodurch sowohl zufällige als auch systematische Messfehler bzw. Positionsfehler des Koordinatenmessgeräts bzw. der Werkzeugmaschine (1) in die Bestimmung von r eingehen (Anmerkung: Bei der Werkzeugmaschine wird zur Bestimmung dieser Referenzposition das Werkzeug (2) gegen einen Messtaster ausgewechselt).
• B) Die Position r wird aus den Messwerten des Koordinatenmessgeräts bzw. der Werkzeugmaschine (1) und aus den Messwerten des zusätzlichen Messsystems (4) durch mathematische Verfahren bestimmt. Der Einfluss zufälliger und systematischer Messfehler bzw. Positionierfehler des Koordinatenmessgeräts bzw. der Werkzeugmaschine (1) auf die Bestimmung von r lässt sich dadurch erheblich reduzieren.

Prerequisite for the intended use of the at least one additional measuring system ( 4 ) is that its geometric position in the coordinate system of the coordinate measuring machine or the machine tool ( 1 ) is known with sufficient accuracy. This is realized by the position and orientation of the additional measuring system ( 4 ) before the solution of the actual measurement task / production task is determined. There are two possibilities:

• A) The position r is determined by probing reference positions on the additional measuring system ( 4 ) certainly. The probing is done by the coordinate measuring machine or the machine tool ( 1 ), whereby both random and systematic measurement errors or position errors of the coordinate measuring machine or of the machine tool ( 1 ) are included in the determination of r (Note: For the machine tool, to determine this reference position, the tool ( 2 ) replaced by a probe).
• B) The position r is calculated from the measured values of the coordinate measuring machine or of the machine tool ( 1 ) and from the measured values of the additional measuring system ( 4 ) determined by mathematical methods. The influence of random and systematic measurement errors or positioning errors of the coordinate measuring machine or of the machine tool ( 1 ) to the determination of r can thereby be considerably reduced.

In case A), the position r of the additional measuring system ( 4 ) can be determined by reference elements on the measuring system (eg rotary axes or reference points) by the coordinate measuring machine or the machine tool ( 1 ) and thereby the position of the reference elements in the coordinate system of the coordinate measuring machine or the machine tool ( 1 ) is determined. If the position of the reference elements with respect to r is known, this in turn can change the position r of the additional measuring system ( 4 ) in the coordinate system of the coordinate measuring machine or the machine tool ( 1 ) are determined by conventional methods of coordinate metrology.

und

, sowie den dazugehörigen Messwerten des zusätzlichen Messsystems kann dann die Position r des Messsystems durch Verfahren der analytischen Geometrie bestimmt werden (s. unten). Bei relativ messenden Systemen kann zusätzlich auch ein konstanter Offset Δe der Messwerte des zusätzlichen Messsystems (4) ermittelt werden. Um den Einfluss zufälliger und systematischer Fehler des Koordinatenmessgeräts bzw. der Werkzeugmaschine (1) bei der Ermittlung von r und Δe zu reduzieren, werden im Allgemeinen mehr als die notwendige Minimalanzahl von Positionen angefahren.In case B) the position r of the additional measuring system ( 4 ) by the coordinate measuring machine or the machine tool ( 1 ) alone can not be determined with sufficient accuracy, neither by reference elements nor by direct probing. Instead, by means of the coordinate measuring machine or the machine tool ( 1 ) a number of spatially distributed positions p _i approached and with the additional measuring system ( 4 ) registers the corresponding measured values. Is the additional measuring system ( 4 ) an absolutely measuring system, at least 3 positions p _{i are to be} approached. Is the additional measuring system ( 4 ) a relatively measuring system, at least 4 positions p _{i are to be} approached. From the measured values of the coordinate measuring machine or of the machine tool ( 4 ), ie the coordinates measured in the positions p _i

and

, as well as that The measured values of the additional measuring system can then be used to determine the position r of the measuring system by analytical geometry (see below). In the case of relatively measuring systems, a constant offset Δe of the measured values of the additional measuring system ( 4 ) be determined. In order to avoid the influence of random and systematic errors of the coordinate measuring machine or of the machine tool ( 1 ) in determining r and Δe, more than the necessary minimum number of positions are generally approached.

Mathematical determination the location of the extra Measuring system (s) for Case B):

a) Relatively measuring measuring system

To determine the position r of the additional, relatively measuring measuring system ( 4 ) is based on the general geometric model equation 1: e i + Δe + w i = f (p i , r) Equation 1

For the special case that the additional measuring system ( 4 ) is a relatively measuring length measuring system, in equation 1 the function f (p _i , r) can be specified directly. The general model equation 1 then goes into Equation 2 for this particular case:

und

Messwerte des Koordinatenmessgeräts bzw. der Werkzeugmaschine für die angefahrenen Positionen p_i, die e_i relative Abstandsmessungen mit einem a priori unbekannten Offset Δe und r = (x_r, y_r, z_r) die zu bestimmende Position des zusätzlichen Messsystems (4). Aufgrund von unvermeidlichen, kleinen Messabweichung in e_i,

und

und weil für r zunächst nur grobe Näherungswerte vorliegen, gibt es zwischen der linken und rechten Seite der Gleichung 1 bzw. Gleichung 2 Widersprüche w_i. Die Quadratsumme dieser Widersprüche lässt sich nach Gauß durch Variation der Parameter (x_r, y_r, z_r) und Δe minimieren. Einen entsprechenden numerischen Algorithmus beschreiben Nelder und Mead in [4]. Damit können dann die Position des zusätzlichen Messsystems r = (x_r, y_r, z_r) sowie der Offset Δe bestimmt werden.In this model equation are the

and

Measured values of the coordinate measuring machine or of the machine tool for the approached positions p _i , the e _i relative distance measurements with an a priori unknown offset Δe and r = (x _r , y _r , z _r ) the position of the additional measuring system ( 4 ). Due to unavoidable, small measurement deviation in e _i ,

and

and because there are only approximate values for r, there are contradictions w _i between the left and right side of Equation 1 and Equation 2, respectively. The sum of squares of these contradictions can be minimized according to Gauss by varying the parameters (x _r , y _r , z _r ) and Δe. A corresponding numerical algorithm is described by Nelder and Mead in [4]. Thus, it is the position of the additional measurement system r = (x _r, y _r, z _r), and the offset can be determined .DELTA.e.

b) Absolutely measuring system

If an absolutely measuring measuring system is used as an additional measuring system (e), then Δe = 0 in Equation 1 or Equation 2. In minimizing the sum of squares of the contradictions w _i , only the parameter r = (x _r , y _r , z _r ) and one then obtains the position r of the additional measuring system ( 4 ).

Mathematical determination the improved measuring points:

und

der Positionen p_i eine Verbesserung (im Sinne einer Genauigkeitssteigerung) zu ermitteln, indem die Messwerte des zusätzlichen Messsystems (4) in geeigneter Weise mit den Messwerten der vorhandenen Messsysteme verknüpft werden. Auf der Grundlage der Modellgleichung 2 erhält man dann die optimierten Messpunkte p_i' mit den Koordinaten

und

(siehe Gleichung 4).The aim of the mathematical evaluation of the measured data is to use for the coordinate measuring machine or the machine tool ( 1 ) determined coordinates

and

the positions p _i to determine an improvement (in the sense of an increase in accuracy) by the measured values of the additional measuring system ( 4 ) are suitably linked to the measured values of the existing measuring systems. Based on the model equation 2 one then obtains the optimized measuring points p _i 'with the coordinates

and

(see Equation 4).

If optimal values have been found for the position r = (x _r , y _r , z _r ) or for Δe, then the coordinates for the position p of the probe / tool ( 2 ) with the help of the additional measuring system ( 4 ) Getting corrected.

For the calculation of corrected positions, the general geometric model equations 3a and 3b are assumed: e i + v ej = f (p i , r) - Δe equation 3a

The function f (p _i , r) depends on the type of additional measuring system ( 4 ) certainly. Is this measuring system z. B. a length measuring system is

Substituted in equation 3a, this results in equation 4a. For the special case of a relatively measuring length measuring system, equations 3a and 3b thus go into the special model equations 4a and 4b:

und

die Werte des Koordinatenmessgeräts bzw. der Werkzeugmaschine (1) für die angefahrenen Positionen p_i, die e_i-Messwerte des zusätzlichen Messsystems (4) nach p_i, die bei relativ messenden Systemen gegebenenfalls mit dem bekannten Offset Δe korrigiert werden, und r = (x_r, y_r, z_r) die Position des zusätzlichen Messsystems (4). Messabweichungen des zusätzlichen Messsystems (4) sind mit

Abweichungen des Messtasters/Werkzeugs (2) von der korrigierten Position p'_i mit den Koordinaten

und

mit

für jede der drei Koordinaten bezeichnet.In these model equations are the coordinates

and

the values of the coordinate measuring machine or of the machine tool ( 1 ) for the approached positions p _i , the e _i values of the additional measuring system ( 4 ) to p _i , which are corrected in relatively measuring systems optionally with the known offset Δe, and r = (x _r , y _r , z _r ) the position of the additional measuring system ( 4 ). Measuring deviations of the additional measuring system ( 4 ) are with

Deviations of the measuring probe / tool ( 2 ) from the corrected position p ' _i with the coordinates

and

With

for each of the three coordinates.

minimiert. Zur Lösung des Minimierungsproblems ist die Gleichung 3a bzw. Gleichung 4a zu linearisieren, wobei die verbesserten Koordinaten

näherungsweise gleich den gemessenen Koordinaten gesetzt werden können, da der Unterschied hinreichend klein ist. In linearisierter Form kann dann die Gleichung 2 wie folgt in Matrizenschreibweise angegeben werden

wobei E die Einheitsmatrix und a = (a₁, a₂, a₃) ein Zeilenvektor ist, der die partielle Ableitung

nach den gesuchten Koordinaten

beinhaltet. Unter Beachtung der Minimierungsfunktion ergibt sich dann die Lösung [5].

mit v'ej = f(pi, r) – Δe – e. Gleichung 6b Corrected positions p ' _i can be calculated by calculating the deviations v _i taking into account the different accuracy of coordinate measuring machine or machine tool ( 1 ) and additional measuring system ( 4 ) are minimized. The model equations 3a and 3b or 4a and 4b are assigned thereto according to the accuracy of the devices uncertainties; for the coordinates of the coordinate measuring machine or of the machine tool ( 1 ) the uncertainty u _KGM and for the measured values of the additional measuring system ( 4 ) the uncertainty u _M. In order to be able to calculate the coordinates for p ' _i , finally, according to Gauss, the weighted sum of the squares of the deviations becomes

minimized. To solve the minimization problem, the equation 3a or equation 4a is to be linearized, wherein the improved coordinates

can be set approximately equal to the measured coordinates, since the difference is sufficiently small. In linearized form, equation 2 can then be given in matrix notation as follows

where E is the unit matrix and a = (a ₁ , a ₂ , a ₃ ) is a row vector representing the partial derivative

according to the coordinates you are looking for

includes. Considering the minimization function then results in the solution [5].

With v ' ej = f (p i , r) - Δe - e. Equation 6b

und aus den allgemeinen Gleichungen 6a und 6b ergeben sich die speziellen Gleichungen 7:

mit

(Anmerkung: Im Fall des absolut messenden Messsystems gilt Δe = 0.)Is the additional measuring system ( 4 ) z. As a length measuring system is as above

and from the general equations 6a and 6b, the specific equations 7 result:

With

(Note: In the case of the absolute measuring system, Δe = 0.)

The weighting factors g _i are dependent on the measurement uncertainty of the coordinate measuring machine or on the machining accuracy of the machine tool and the measurement uncertainty of the additional measuring system (equations 6a and 6b or 7a and 7b). With _{μ CMM} as measurement uncertainty of the coordinate measuring machine or machining accuracy of the machine tool and with μ _M as measurement uncertainty of the additional measuring system follows generally for g _i

Is z. B. the measurement uncertainty of the additional measuring system ( 4 ) is much smaller than the measurement uncertainty of the coordinate measuring machine or the machining accuracy of the machine tool, g _i ≈ 1. Is the measurement uncertainty of the additional measuring system ( 4 ) equal to the measurement uncertainty of the coordinate measuring machine or the machining accuracy of the machine tool is g _i = 0.5, ie the contradictions are in equal parts the coordinate measuring machine or the machine tool ( 1 ) and the additional measuring system ( 4 ).

According to the method described, more than one additional measuring system ( 4 ). The number of equations then increases accordingly. In addition, more than just three displacement axes and also rotary axes (turntables) can be treated with the described method.

Another variant results when using measuring probes. (Note: Measuring probes have their own measuring systems that measure the position of the probe relative to a reference point on the probe, whereas switching probes emit only one trigger pulse.) In this case, the probing probes take the displacement of the probe t = (x _t , y _t , z _t ). For the position of the probe then p * = p + t. If a reference element of the additional measuring system ( 4 ) fixed to the probe element, in this variant the additional equation of determination | p + t - r | = e or | p + t - r | = e + Δe used to determine the improved measuring point coordinates. This has the advantage that in this case the measurement uncertainty of the probe system is not fully reflected in the measurement result. The improved measurement point coordinates can be calculated as described above if formally p is replaced by p *.

preferred embodiment

Preferred embodiment is a on the machine bed of the coordinate measuring machine or the machine tool ( 1 ) fixed pivoting laser interferometer with a mechanically or optically defined pivot point. This interferometer automatically follows a triple mirror or a so-called "cat's eye", which is located near the touch probe / tool of coordinate measuring machine or machine tool ( 1 ) is attached. The interferometric measuring system is thus incorporated into the software of the coordinate measuring machine or of the machine tool ( 1 ), that the distance from the interferometric measuring system to the touch probe / tool ( 2 ) in addition to the length measuring systems in the axles ( 3 ) is evaluated. While this generally has to be done in real-time in the case of machine tools with path control, in the case of a coordinate measuring machine the additional measuring system ( 4 ) are synchronized by a trigger pulse at the time of probing with the reading of the other measuring systems. The weighting of the measurement conditions (see Equation 4) in the overdetermined system of equations can be carried out clearly in favor of the interferometric length measuring system in such a system construction, since this has a very low measurement uncertainty, on the other hand the measuring line with a suitable orientation only a small offset to the measurement object Has. Thus, the Abbeprinzip can be approximately maintained.

• – Messung der Form von Flächen auf Koordinatenmessgeräten. Hierbei sollte das Längenmesssystem ungefähr senkrecht zu der gemessenen Fläche orientiert sein. Anwendungen sind die Formmessung von Lehrringen auf Drehtischen oder die Profil- bzw. Flankenlinienmessung bei Zahnrädern.
• – Kalibrierung von langen Endmaßen, Stufenendmaßen oder Maßstäben mit Koordinatenmessgeräten. Entgegen den bekannten Lösungen kann hier die genaue und sehr zeitraubende Ausrichtung zwischen Maschinenachse, Werkstück und Interferometer entfallen.
• – Fertigung großer Werkstücke auf Werkzeugmaschinen. Dabei kann das Interferometer in einer Achse eingesetzt werden, in der eine besonders enge Positionstoleranz eingehalten werden muss, die die Möglichkeiten der Werkzeugmaschine im normalen Betrieb überschreitet.

Examples of application areas of such a measuring arrangement are:

• - Measurement of the shape of surfaces on coordinate measuring machines. Here, the length measuring system should be oriented approximately perpendicular to the measured surface. Applications include the form measurement of teaching rings on turntables or the profile or flank line measurement for gears.
• - Calibration of long gauges, step gauges or scales with CMMs. Contrary to the known solutions can account for the exact and very time-consuming alignment between the machine axis, workpiece and interferometer here.
• - Production of large workpieces on machine tools. In this case, the interferometer can be used in an axis in which a particularly tight position tolerance must be maintained, which exceeds the capabilities of the machine tool during normal operation.

Advantages of solution according to the invention

Even though coordinate Measuring Machines or machine tools today already a considerable accuracy there are applications where this is not enough. This is z. As is the case in the production of high-precision surfaces (z. B. spheres and aspheres) or when calibrating reference standards such as step dimensions or also multi-dimensional specimens. By the solution according to the invention is the increase of measuring accuracy in one or more axes possible.

at Industrial robots, the z. B. in a production line for manufacturing or measurement can be used, the application of the method according to the invention the manufacturing or Measurement accuracy considerably increase the use of robotic kinematics for certain applications only possible do.

To is not an exact alignment between the measuring direction of the additional Measuring system, the machine axis and the workpiece necessary. The degree of Measuring or Steuergenauigkeitssteigerung can thereby by a the respective measurement or production task optimized arrangement of the additional measuring system to be influenced. An optimal arrangement of this measuring system is then achieved if the Abbeprinzip is met, d. H. the Measuring line of the additional Measuring system is in one axis with the measurement object.

In general, this method is characterized by the fact that virtually any measurement and manufacturing tasks can be processed with the so-equipped facilities. However, that also means that By integrating additional measuring systems according to this method, coordinate measuring machines and machine tools can in some areas replace highly accurate special equipment (eg Abbe comparators, precision manufacturing machines).

Especially at big (and therefore usually less accurate) coordinate measuring machines / machine tools the accuracy in critical tasks can be increased extremely, without the operator having special have metrological knowledge got to. This is z. B. also achieved by those measuring systems a higher one Weight is assigned, which have a better measurement accuracy.

If Laser interferometer as additional Measuring systems used in coordinate measuring machines, is Furthermore direct traceability of length measurements guaranteed.

One Another advantage is that these additional measuring systems at, existing Equipment retrofitted can be.

Literature:

• [1] Schüssler, H.,: Special Applications of Industrial Laser Measurement, Automotive Industry 4/84, page 467-472,
• [2] Nakamura e.a: Development of a co-ordinate measuring system with tracking laser interferometers, Annals of the CIRP, Vol. 40/1/1991, P. 523-526
• [3] German Patent Application 19947374.9-52 "Method of Detection of geometric deviations of coordinate measuring machines and Machine Tools "
• [4] Nelder, J.A .; Mead, R .: A simplex method for function minimization, Computer Journal, p. 308-313, 1965
• [5] Wolf; H .: Balance calculation I + II, Dümmler, 1994
• [6] JP 07239 209 A Method and device for activity measurement of automatic machine tools
• [7] DE 19752290 A1 "Method and device for measuring position and / or orientation of cooperating machine units"
• [8th] DE 3941144 A1 "Coordinate measuring machine for the non-contact measurement of objects"
• [9] DE 196 00 002 A1 . DE 195001877 "Integral process for on-line geometry testing of workpieces from multiple forming surfaces"

Claims (3)

Method for increasing the accuracy of CMMs and machine tools in the, a) in addition to the measuring systems of At least one additional axle Measuring system in the coordinate measuring machine or the machine tool is integrated, b) from this additional measuring system at least an additional geometric information about the actual position or the actual travel of a coordinate measuring machine or a machine tool is obtained, c) one or more additional geometric information together with the scale signals and / or probe signals of the coordinate measuring machine or the machine tool evaluated and in an overdetermined Equation system be formulated d) the additional geometric information corresponding to the assumed or calculated Uncertainty of this information in the mathematical solution of Be weighted equation system, e) in the solution of the overdetermined Equation system minimizes the residuals of all equations mathematically become. Method according to claim 1, characterized that extra geometric information from an interferometric length measurement is generated between two reference elements. Method according to claim 1, characterized that a non-contact swiveling length measuring system automatically tracked becomes.