DE102007018865A1 - Length measuring system, particularly for machine tool, has reflection device that is fastened to arm in rotatable manner, where reflection device reflects back assigned ray of light - Google Patents

Abstract

The length measuring system (10) has a reflection device that is fastened to an arm (24) in a rotatable manner. The reflection device reflects back the assigned ray of light (18) during flexible deflection of the arm on a beam splitter (14) in such a manner that optical distance in linear approximation of the deflection is independent. An independent claim is also included for a method for examining or calibrating a machine tool.

Description

The The invention relates to a length measuring system for a machine tool with (a) a beam splitter for generating a reference light beam and a working light beam from a light beam, (b) a reflection device for reflecting the working light beam and (c) a telescopic one Arm, at one end of the reflection device is attached. According to one second aspect, the invention relates to a method for testing or Calibrating a machine tool.

machine tools have to on a regular basis their positioning accuracy will be checked with which they can position an end effector in space. Of the End effector may be, for example, a milling head or a laser cutting head. Appears during testing the machine tool out that a given accuracy requirement not fulfilled is, then the machine tool must be recalibrated.

Known Methods and apparatus for calibrating machine tools For example, use laser trackers. This will be an end effector in the form of a mirror aimed with a laser beam of is delivered to an interferometer. Then the end effector will open a given trajectory moves. At the same time, the laser beam becomes tracked to the end effector and continuously measures a change in distance between the laser tracker and the end effector. From the trajectory of the end effector and the Location of the laser tracker, the distance change can be calculated would have to be measured with a faultless machine tool. differs actually measured distance change from the calculated change in distance by a predetermined amount, so the machine tool must be recalibrated.

adversely At this procedure is that the Endeffektor only with relatively small Speeds can be moved because the laser tracker the laser beam always follow the end effector got to. At high speed, this tracking is no longer possible. Becomes the machine tool when processing at high feed rates used, so dynamic forces limit the accuracy. inaccuracies the machine tool at high tool speeds or accelerations however, can not be detected by known methods.

Of the Invention is based on the object disadvantages of the prior art to overcome. The invention solves the task by a generic length measuring system, in which the Reflection device pivotally mounted on the arm is that they the working light beam even with elastic deflection of the Armes always reflected back to the beam splitter that the optical path length in a linear approximation independent of the deflection is.

• (a) Bereitstellen eines Längenmesssystems nach einem der vorstehenden Ansprüche,
• (b) Verbinden des teleskopierbaren Arms mit einer Spindel der Werkzeugmaschine,
• z. B. über eine Werkzeugaufnahme,
• (c) Bewegen der Spindel auf einer vorgegebenen Bahn,
• (d) Erfassen einer Ist-Abstandsänderung zwischen der Reflexionsvorrichtung (28) und dem Strahlteiler und (e) Vergleichen der erfassten Abstandsänderung mit einer aus der vorgegebenen Bahn errechneten Soll-Abstandsänderung.

According to a second aspect, the invention solves the problem by a method for testing or calibrating a machine tool comprising the steps: Method for testing or calibrating a machine tool, comprising the steps:

• (a) providing a length measuring system according to one of the preceding claims,
• (b) connecting the telescopic arm to a spindle of the machine tool,
• z. B. via a tool holder,
• (c) moving the spindle on a predetermined path,
• (d) detecting an actual distance change between the reflection device ( 28 ) and the beam splitter, and (e) comparing the detected change in distance with a desired distance change calculated from the given path.

Advantageous to the invention is that length measurements even at a high dynamics are possible. Thereby can Inaccuracies of a machine tool are detected when they operated at high tool speeds or accelerations becomes.

One Another advantage is the simple applicability of the invention. So can the length measuring system according to the invention be firmly mounted in the machine tool and automated with be connected to a spindle of the machine tool. This will be routine checks and / or Calibrations of the machine tool possible without human Worker must be expended.

One Another advantage is the simple construction of a length measuring system according to the invention. It is therefore easy and inexpensive and can also be used by untrained personnel.

in the For purposes of the present description, the optical path length will be the understood in physical usage meant optical path length. The optical path length is the integral over the product from the past Path and the refractive index on the way.

The deflection of the arm is understood as a measure of the elastic deformation of the arm. In particular, the deflection can be defined as the maximum deflection of the arm between its two ends from the force-free shape. By the feature that the optical path length is linearly independent of the implementation, it is to be understood that a power difference Development of the function, which indicates the optical path length as a function of the deflection, around the zero point of this function has no linear term. The optical path length thus depends, for example, only in a quadratic approximation on the deflection.

In a preferred embodiment has the length measuring system at least two telescopic poles on. This will be advantageous achieved a particularly simple mechanical structure. Especially Preferably, the arm of the length measuring system at one end a closing body, wherein the reflection device by means of a receptacle on the end body relative to the closing body is movably mounted and wherein the receptacle is so coupled to the closure body, that with elastic deflection of the arm, the recording relative to the closing body swings. This pivoting movement is thus designed so that they Bending of the arm compensated. That is, one of the beam splitter the reflection device extending light beam despite the deflection back again is reflected on the beam splitter. This will be advantageous achieved that when the arm with an end effector of the machine tool is coupled and this end effector at a high speed or acceleration is moved, any deflections of the arm be compensated due to inertial forces.

Especially Preferably, the receptacle has at least four connecting elements on, which connect the recording with the closing body. In this way The deflection of the arm can be compensated particularly effectively. Particularly preferably, the closing body is so with the telescopic rods connected, that the elastic deflection of the arm to an elastic Deformation of the end body leads and that the connecting elements so connected to the launching body are that the elastic deformation of the closing body to do so leads, that the receptacle pivots relative to the end body. This pivoting movement works again a deflection of the working light beam due to the deflection the arm and compensates for this. The overall system of reflection device, Recording, fasteners and end body is for a high natural frequency designed. This avoids that resonances occur.

Especially preferred is the closing body so connected to the telescopic rods that the deflection becomes one Offset of parts of the end body along the longitudinal extension the telescopic strut leads and that the Verbindungsele elements so connected to the closing body are that the displacement of the closing body causes the Recording pivots relative to the end body. It is possible this To combine the effect with the effect mentioned in the previous paragraph.

In a preferred embodiment has the arm of the length measuring system according to the invention an at least three-stage telescope arrangement with a basic telescope stage, at least one telescope center stage and one telescope completion stage on. This results in a particularly large extendability of the length measuring system reached.

Especially Preferably, the telescopic base comprises at least three on the closing component fixed basic telescopic poles. The at least one telescope middle stage includes a middle stage slider sliding on the base stage telescopic rods is fixed, and at least three rigidly attached to the middle stage slider fixed middle-stage telescopic rods and the telescope termination stage includes a final stage slider sliding on the mid-stage telescopic rods is fixed, at least three rigidly attached to the final stage slider fasten finishing level telescopic rods and a base body, the is rigidly connected to the graduated telescopic rods.

there is it cheap if the basic telescope level at least one telescopic center stage and the telescope termination stage each comprise four or five telescopic poles. This will be the length measuring system at the same time light and sufficiently stiff, even at high speeds or accelerations to show only a small deflection.

The Telescopic rods of a stage are preferably at equal angular intervals arranged in a circle. This results in a uniform rigidity of the length measuring system. At the same time, the rigidity is increased overall and the production of the length measuring system facilitated.

In a preferred embodiment includes the closing body a first annular disc and a second spaced from the first annular disc second Ring disc, the two annular discs elastic with each other are connected. It is advantageous if the at least one Mid-level slider and the final stage slider respectively comprise two spaced annular discs.

Around a high length variability the arm while maintaining sufficient rigidity, The annular discs have a distance of between 0.025 times and 0.2 times a length the telescopic pole that is on the slider are attached.

Around Rucks, so changes the acceleration of the movement, during the use of the length measuring system according to the invention To avoid the telescopic rods are preferred to the respective sliding bodies stored free of play.

In a preferred embodiment the telescopic arrangement is designed so that, when a pull-out length between the base body and the closing body by a change factor changes Also, a distance from the end body to the middle stage sliding body to the same change factor changes. This can As a reflection device, a mirror can be used, whereby a particularly simple construction of the length measuring system results.

Around To achieve a particularly high rigidity, the telescopic arrangement preferably several times, in particular three times, four times, five times or sixfold mechanically overdetermined.

machine tools have a rule, for example by coolant mist, chips or other particles contaminated working space. If such impurities in the beam path of the working light beam or on the reflection device this can affect the functionality of the length measuring system affect. Therefore, an envelope is preferred for shielding from the telescopic rods, the base body and the closing body surrounding space provided. Such a wrapper may, for example, a Be bellows.

One particularly light length measuring system results through the use of hollow bars. A use of round bars leads to a particularly easy and therefore inexpensive to manufacture length measuring system.

in the The invention will be explained in more detail with reference to the accompanying drawings. It shows

1 a perspective view of a length measuring system according to the invention,

2 a detailed view of the length measuring system at its end with the reflection device,

3 a perspective view of the arm of the length measuring system according to 1 and

4 a schematic sectional view of the end of the length measuring system with a receptacle for the reflection device in the unbent case.

5 shows the schematic view 4 , wherein a force leads to a bending of the arm and

6 shows a schematic drawing of an arm of an alternative embodiment of a length measuring system according to the invention.

1 shows a length measuring system 10 , which is a schematically drawn basic body 12 with a beam splitter 14 for generating a reference light beam 16 and a working light beam 18 , a light source 20 and a detector 22 for detecting an interference between the reference light beam 16 and the working light beam 18 includes.

The working light beam 18 enters an arm 24 , which is formed by a telescopic strut, and is at one of the main body 12 opposite end 26 of the arm 24 from one in 1 partially hidden reflection device 28 on the beam splitter 14 reflected back. The length of the arm changes 24 , so there is an interference between the reference light beam 16 and the working light beam 18 that from the detector 22 is recorded and the resulting change in length of the arm 24 calculated.

The arm 24 points to its end 26 a conclusion body 30 on, the first ring disk 32.1 and a second annular disc 32.2 includes. The first ring disk 32.1 and the second annular disc 32.2 have the same shape and are arranged concentrically with their annular surfaces one behind the other. At the closing body 30 are four equally long basic telescopic rods 34.1 . 34.2 . 34.3 . 34.4 each mounted in a 90 ° angle steps on a circle concentric with the first annular disc 32 , and the second annular disc 32.2 runs. The distance between the first annular disc 31.1 and the second annular disc 32.2 this is one twentieth of the length of the basic telescopic poles 34.1 to 34.4 ,

The basic level telescopic poles 34.1 . 34.2 . 34.3 . 34.4 are free of play in a middle-level slider 36 stored. The middle stage slider 36 is like the closing body 30 from a first annular disc 38.1 and a second annular disc 38.2 that have the same shape as the ring discs 32.1 . 32.2 of the final body 30 ,

At the middle stage slider 36 are four mid-range telescopic poles 40.1 . 40.2 . 40.3 . 40.4 on a final stage slider 42 attached. The middle stage telescopic poles 40.1 . 40.2 . 40.3 . 40.4 are arranged at equal angular intervals on a circle with the same diameter and the same center as the basic stage telescopic rods 34.1 to 34.4 , The basic level teles kopstangen 34.1 - 34.4 reach through four recesses 44.1 to 44.4 in the final stage slider and can be stored without play in this recess, but it is not in the present embodiment.

At the final stage slider 42 are four graduated telescopic rods 46.1 . 46.2 . 46.3 . 46.4 rigidly attached and also fixed to a base body 48 connected. The graduation stage slider 42 and the base body 48 each comprise first and second annular discs 50.1 and 50.2 respectively. 52.1 and 52.2 ,

The closing body 30 , the mid-level slider 36 , the graduation stage slider 42 and the base body 48 form with the respective associated telescopic rods a three-stage telescopic arrangement, due to which the end body 30 relative to the base body 48 guided is movable.

On in this way, the base, middle, and final stage telescopic poles are each attached flying to the respective adjacent step.

2 shows the arm 24 in the vicinity of the closing body 30 , At the closing body 30 are four rod-like fasteners 54.1 . 54.2 . 54.3 . 54.4 attached with one of its ends. The other end is with a recording 56 via respective joints 58.1 . 58.2 . 58.3 and 58.4 connected. At the joints 58.1 , to 58.4 For example, they may be solid-state joints that have material weakening or zones of more elastic material compared to the environment.

3 shows a further perspective view of the in the 1 and 2 illustrated arm.

4 shows a schematic sectional view of the arm 24 , wherein in each case two basic stage telescopic rods are superimposed and wherein the section through the two connecting elements 54.1 and 54.3 runs. The basic level telescopic poles 34.1 and 34.3 each have neutral fibers 60.1 and 60.3 on, which are drawn as dashed lines. In the in 4 In the situation shown, no forces act on the arm 24 ,

In 5 the situation is shown in which an external force F on the basic stage telescopic rods 34.1 - to 34.4 acts, which then show a deflection w. The deflection w is the maximum deflection between the neutral phase 60.1 in the free state and the neutral phase 60.1 in the 5 shown case that an external force F on the arm 24 acts. The force F usually does not attack locally, but is an acceleration or inertial force, which acts at each point of the length measuring system. However, this inertial force can be approximated by the in 5 drawn force F are described.

Due to the elastic deflection of the basic stage telescopic rods 34 the closing body deforms 30 and thus also the second annular disc 32.2 , This results in an offset V between a connection point 62.1 of the connecting element 54.1 with the second annular disc 32.2 and a connection point 62.3 between the connecting element 54.3 and the second annular disc 32.2 , Due to this offset V, the joint becomes 58.1 from the second annular disc 32.2 away and that joint 58.3 on the second ring disk 32.2 too moved. Because of this movement of the joints 58.1 and 58.3 pans the shot 56.2 relative to the second annular disc 32.2 at an angle 2a that accurately compensates the angle α, which is the neutral fiber 60.1 'opposite the neutral fiber 60.1 having. The in 5 from the left incident working light beam 18 is thus reflected back in spite of the deflection w. In 5 only one telescope stage is shown, in which 5 On the left you can connect one more, two more or more telescopic stages. Several telescopic stages are attached to each other so that the effect described above is maintained.

6 shows an alternative way of recording 56 with the fasteners 54 , In this embodiment, the connecting elements connect 54.1 to 54.4 in each case to the associated connection point 62.1 . 62.2 . 62.3 . 62.4 neighboring joints 58.3 . 58.1 and 58.2 , It is exploited that the second annular disc 32.2 in turn performs a small pivoting movement in their respective edge region, which then passes over the joints 58 on the recording 56 is transmitted.

10

Length measuring system

12

body

14

beamsplitter

16

Reference light beam

18

Operating light beam

20

light source

22

detector

24

poor

26

The End

28

reflecting device

30

closing component

32.1, 32.2

first second washer

34.1, 34.2, 34.3, 34.4

Basic tier telescopic rod

36

Mid-level slider

38.1, 38.2

first second washer

40.1, 40.2, 40.3, 40.4

Intermediate level telescopic rod

42

Final stage sliding

44.1, 44.2, 44.3, 44.4

recess

46.1, 46.2, 46.3, 46.4

Final stage telescopic rod

48

base body

50.1, 50.2

first second washer

52.1, 52.2

first second washer

54.1, 54.2, 54.3, 54.4

fasteners

56

admission

58.1, 58.2, 58.3, 58.4

joints

60.1, 60.2, 60.3. 60.4

neutral fiber

62.1, 62.2, 62.3, 62.4

junction

w

deflection

F

force

Claims (24)

Length measuring system, in particular for a machine tool, having (a) a beam splitter ( 14 ) for generating a reference light beam ( 16 ) and a working light beam ( 18 ) from a light beam, (b) a reflection device ( 28 ) for reflecting the working light beam ( 18 ) and (c) a telescopic arm ( 24 ), at one end ( 26 ) the reflection device ( 28 ), characterized in that the reflection device ( 28 ) pivotally so on the arm ( 24 ) is attached, that it the working light beam ( 18 ) even with elastic deflection of the arm ( 24 ) always on the beam splitter ( 14 ) reflects that the optical path length in a linear approximation is independent of the deflection (w). Length measuring system according to claim 1, characterized in that the arm ( 24 ) has at least two telescopic rods. Length measuring system according to claim 2, characterized in that - the arm ( 24 ) at one end ( 26 ) a closing body ( 30 ), - the reflection device ( 28 ) by means of a recording ( 56 ) on the closing body ( 30 ) relative to the end body ( 30 ) is movably mounted, and - the receptacle ( 56 ) so with the closing body ( 30 ) is coupled, that with elastic deflection of the arm ( 24 ) the recording ( 56 ) relative to the end body ( 30 ) pans. Length measuring system according to claim 3, characterized in that the receptacle ( 56 ) at least four connecting elements ( 54.1 . 54.2 . 54.3 . 54.4 ) containing the receptacle ( 56 ) with the closing body ( 30 ) connect. Length measuring system according to claim 4, characterized in that - the closing body so with telescopic rods ( 34.1 . 34.2 . 34.3 . 34.4 ), that the elastic deflection of the arm ( 24 ) to an elastic deformation of the end body ( 30 ) leads to locally different angles and that - the connecting elements ( 54.1 . 54.2 . 54.3 . 54.4 ) so with the closing body ( 30 ), that the elastic deformation of the end body ( 30 ) causes the recording ( 56 ) relative to the end body ( 30 ) pans. Length measuring system according to one of claims 2 to 5, characterized in that - the end body ( 30 ) so with the telescopic poles ( 34.1 . 34.2 . 34.3 . 34.4 ), that the deflection (w) to an offset (V) of two connecting elements ( 54.1 . 54.2 . 54.3 . 54.4 ) along the longitudinal extent of the telescopic struts ( 34.1 . 34.2 . 34.3 . 34.4 ) and that the - connecting elements ( 54.1 . 54.2 . 54.3 . 54.4 ) so with the closing body ( 30 ), that the offset (V) of the end body ( 30 ) causes the recording ( 56 ) relative to the end body ( 30 ) pans. Length measuring system according to one of claims 2 to 6, characterized in that the arm ( 24 ) has an at least three-stage telescope arrangement with a basic telescope stage, at least one telescopic center stage and a telescope termination stage. Length measuring system according to claim 7, characterized in that (a) the telescopic base stage has at least three base stage telescopic rods ( 34.1 . 34.2 . 34.3 . 34.4 ) comprises (b) the at least one telescope center stage - a middle stage slider ( 36 ) attached to the basic telescopic rods ( 34.1 . 34.2 . 34.3 . 34.4 ) is slidably mounted, and - at least three on the middle stage slider ( 36 ) rigidly fixed intermediate stage telescopic rods ( 40.1 . 40.2 . 40.3 . 40.4 ) and (c) the telescope termination stage - a completion stage slider ( 42 ) attached to the middle-stage telescopic poles ( 40.1 . 40.2 . 40.3 . 40.4 ) is attached in a sliding manner, - at least three on the final stage slider ( 42 ) rigidly fixed graduated telescopic rods ( 40.1 . 40.2 . 40.3 . 40.4 ) and - a base body ( 48 ) with the graduated telescopic rods ( 40.1 . 40.2 . 40.3 . 40.4 ) is rigidly connected. Length measuring system according to spoke 8, characterized in that the telescopic base stage, the at least one telescopic center stage and the Te four or five telescopic poles. Length measuring system according to one of the claims 8 or 9, characterized in that the telescopic rods a Stage at equal angular intervals are arranged on a circle. Length measuring system according to one of the claims 8 to 10, characterized in that the telescopic rods parallel to each other. Length measuring system according to one of claims 8 to 11, characterized in that the closing body ( 30 ) a first annular disc ( 32.1 ) and one of the first annular disc ( 32.1 ) spaced second annular disc comprises, which are elastically connected to each other. Length measuring system according to one of claims 8 to 12, characterized in that the at least one middle-level sliding body ( 36 ) and the graduated stage slider ( 42 ) each two spaced annular discs ( 38.1 . 38.2 ; 50.1 . 50.2 ). Length measuring system according to one of the claims 12 or 13, characterized in that the annular discs of the corresponding sliding distance that is between 0.1 times and 0.4 times times a length which is telescopic rods, the on the slider are attached. Length measuring system according to one of the claims 8 to 14, characterized in that the telescopic rods to the respective sliding bodies are stored without play. Length measuring system according to one of claims 8 to 15, characterized in that the telescopic arrangement is formed so that, when a Ausziehlänge between the base body ( 48 ) and the closing body ( 30 ) changes by a change factor, a distance from the closing body ( 30 ) to the middle stage slider ( 36 ) changes by the same change factor. Length measuring system according to one of the claims 8 to 16, characterized in that the telescope arrangement several times, especially triple, quadruple or fivefold, mechanically overdetermined is. Length measuring system according to one of the preceding claims, characterized in that the reflection device ( 28 ) is a mirror, in particular a plane mirror. Length measuring system according to one of the claims 2 to 18, characterized by a sheath for shielding from the telescopic rods, the base body and the closing body surrounded space against pollution. Length measuring system according to one of the claims 2 to 19, characterized in that telescopic rods hollow rods are. Length measuring system according to one of the claims 2 to 20, characterized in that telescopic rods round rods are. Machine tool that uses a length measuring system according to one of preceding claims includes Method for testing or calibrating a machine tool, comprising the steps of: (a) providing a length measuring system ( 10 ) according to one of the preceding claims, (b) connecting the telescopic arm ( 24 ) with a spindle of the machine tool, z. B. via a tool holder, (c) moving the spindle on a predetermined path, (d) detecting an actual distance change between the reflection device ( 28 ) and the beam splitter ( 14 ) and (e) comparing the detected change in distance with a desired distance change calculated from the given path. Method according to claim 23, characterized in that step (b) comprises inserting a magnetic coupling piece with a tool holder of the spindle and a magnetic coupling of the Arms with the coupling piece includes.