DE102016221938B4 - Method for reducing unwanted rotation of a machine part - Google Patents

Abstract

Method for reducing an undesired rotation of a machine part (3) that is moved in a translational manner during operation of a coordinate measuring machine (100; 200; 300) about at least one machine part rotation axis (MD _X , MD _Z ), wherein the machine part is a movable portal (3) and wherein the rotation occurs as a result of a force acting to generate a translational movement of the portal (3), wherein a first mass (M1) that can be rotated as a gyroscope is coupled to the portal (3), and the method comprises:
- Applying a force (F) in a translation direction (Y) and translationally moving the portal (3) in the translation direction (Y) and simultaneously
- Rotating the first mass (M1) about a first mass rotation axis (D _Y ) which is transverse, in particular vertical, to the at least one machine part rotation axis (MD _X , MD _Z ) and is aligned in the translation direction (Y).

Description

The invention relates to a method for reducing an undesirable rotation of a machine part and to a machine designed for this method.

If you want to move a mass linearly using a drive, the force vector acting on the mass to be moved should ideally pass through the center of gravity of the mass, or at least close to the center of gravity. If this is not possible, an additional torque is introduced into the mass to be accelerated, which results in a rotation of the mass. When machine parts are moved in a translational manner, a force intended to cause the translational movement often acts outside the center of gravity, i.e. eccentrically. Such an eccentrically acting force often causes an undesirable rotation of the machine part, which is superimposed on the desired translation. The rotation is caused by a lever arm that results from the force acting outside the center of gravity of the rigid machine part. This problem is difficult to avoid with coordinate measuring machines (hereinafter also referred to as CMMs) and machine tools, especially those with a gantry design. Typically, the drive and the point at which the force is introduced for the movement are far away from the center of gravity of the moving part, especially the gantry. This means that in the case of an air-bearing gantry, the torque introduced when the gantry accelerates must be absorbed by the air bearings. This reduces the air gap in the air bearing and parts that are supported against each other can come into contact, which can damage the bearings.

One can try to achieve the stability of the part to be moved in translation by increasing the stability of the structure or reducing the play in a guide. Unfortunately, this cannot be achieved, or is not trivial, without increasing costs and/or weight.

The US 4,638,221 A discloses a structure which supports a body of the structure capable of undergoing acceleration about an axis. Reaction force compensating means are included, comprising a further axis through the structure which extends in the same direction as the axis about which the body can be accelerated, a reactant having a greater moment of inertia than the body and the supporting structure for rotation about said axis, reaction driving means responsible for accelerating the reactant independently and simultaneously with the body in the opposite direction to the body upon acceleration of the body, and a speed reduction coupling means mounted between the reactant and the reaction driving means for slowing the rotation of the reactant at a slower rate of acceleration than that of the body, said reaction driving means being arranged to produce a rate of change of torque in the compensating means such that the torsional reaction force of the body and the compensating means on the structure are identical or opposite.

The DE 103 53 050 A1 discloses a device for compensating a torque caused by the gyrostatic effect on a movable axis in machine tools or production machines, wherein a rotating machine counter system attached to the axis which generates a useful angular momentum is provided, the amount of which at least partially corresponds to the amount of the useful angular momentum, in addition to a rotating machine utilization system attached to the axis which generates a useful angular momentum, wherein the useful torque caused by the temporal change in the useful angular momentum during a movement of the machine utilization system is at least partially compensated by a counter torque caused by the temporal change in the counter angular momentum.

The DE 601 07 619 T2 discloses a non-reactive rotary drive mechanism for a positioning device comprising: a housing; a first motor for positioning an output shaft relative to the housing, the first motor having a first rotor connected to the output shaft and a first stator also mounted on a stator shaft for rotation relative to the housing, whereby rotational acceleration torques applied by the first motor to the output shaft are balanced by equal and opposite accelerations of the stator shaft; a second motor having a second rotor connected to that of the first motor and a second stator connected to the housing; means for supplying power to each motor; and control means for controlling the power supplied to the second motor to counteract external torques applied to the output shaft, the control means being arranged to maintain the desired rotational speed of the stator shaft.

The object of the invention is to reduce undesirable rotational movements of translationally moving machine parts. In particular, a rotation of a machine part at an eccentric The mechanically acting force that serves a translational movement must be minimized.

According to a basic idea of the invention, a machine part in a coordinate measuring machine (CMM), which is a movable portal of the CMM and is to be moved in a translational manner, is provided with a rotating or rotatable mass. The rotating mass acts as a gyroscope and has an angular momentum when rotating. The invention makes use of the stabilizing effect of a rotating mass to protect the portal from an undesirable rotary movement or to counteract this rotary movement. The conservation of angular momentum of the at least one rotating mass counteracts an undesirable rotation about at least one axis that deviates from the axis of rotation of the mass, i.e. the gyroscope axis.

The invention is applied to a coordinate measuring machine (CMM), which is also referred to below as the "machine". The portal of the CMM is also referred to below as the "machine part".

In this context, a gyroscope is understood to be a body that can rotate about an axis of rotation and that has a finite angular momentum when rotating about said axis of rotation due to its moment of inertia.

The machine part can be stabilized against unwanted rotation by setting an appropriate angular momentum. The greater the mass of the machine part, the greater the angular momentum is usually set to achieve stabilization. The angular momentum is the product of the moment of inertia of the rotating mass and the angular velocity.

• - Einwirken einer Kraft in eine Translationsrichtung und translatorisches Bewegen des Portals in die Translationsrichtung und gleichzeitig
• - Rotieren der ersten Masse um eine erste Masse-Drehachse, die quer, insbesondere vertikal, zu der zumindest einen Maschinenteil-Drehachse steht und die in die Translationsrichtung ausgerichtet ist.

The invention specifies a method for reducing an undesirable rotation of a machine part that is moved in translation during operation of a CMM about at least one machine part rotation axis, wherein the machine part is a movable gantry and wherein the rotation occurs as a result of a force acting to generate a translational movement of the gantry, wherein a first mass that can be rotated as a gyroscope is coupled to the gantry, and the method comprises:

• - Applying a force in a translational direction and translational movement of the portal in the translational direction and at the same time
• - Rotating the first mass about a first mass rotation axis which is transverse, in particular vertical, to the at least one machine part rotation axis and which is aligned in the translation direction.

According to the invention, it is particularly provided that the first mass, or further such rotatable masses (such as a second rotatable mass mentioned below), rotate permanently, preferably at a high speed. Permanent rotation means that the mass rotates when the machine is operating or when the machine is ready for operation, regardless of whether the machine part is being moved.

The rotatable first mass is preferably a rotational body. The same preferably applies to a second rotatable mass mentioned below.

The first mass rotation axis preferably runs through the center of gravity of the first mass. The same preferably also applies to a second rotatable mass mentioned below.

If there are several machine part rotation axes, then the mass rotation axis is perpendicular to at least one of the machine part rotation axes. If there are two machine part rotation axes, the mass rotation axis is perpendicular, in particular vertical, to at least one of the two machine part rotation axes. If there are three machine part rotation axes, the mass rotation axis is perpendicular, in particular vertical, to at least two of the three machine part rotation axes. This applies both to a first mass rotation axis mentioned above and to a second mass rotation axis mentioned below.

In one embodiment of the method, the first mass rotation axis is aligned in the translation direction. This provides the advantage that an undesirable rotation of the machine part about two machine part rotation axes can be counteracted by a single rotatable mass, as shown in embodiments.

In a further embodiment, the first mass rotation axis and the vector of the force acting in the translation direction lie on a straight line. In other words, the first mass rotation axis and the force vector are aligned in this embodiment. The first mass rotation axis particularly preferably runs through the center of gravity of the first mass. In this case, the center of gravity of the mass and the force vector lie on a straight line. This ensures that no undesirable torque is introduced onto the rotating first mass by the applied force. In other words, the eccentricity of the center of gravity of the machine part is determined by the coupled first Mass is not changed or even increased and the first mass behaves neutrally in this respect.

• - Rotieren der ersten Gegenmasse um die erste Masse-Drehachse, wobei aus derselben Betrachtungsperspektive die Drehrichtung der ersten Gegenmasse gegenläufig zu der die Drehrichtung der ersten Masse ist.

In a further embodiment, a method is specified, wherein a first counter mass that can rotate as a gyroscope is coupled to the machine part, which counter mass can rotate about the same first mass rotation axis as the first mass and which is coupled on a side of the machine part facing away from the rotatable first mass. The method further comprises:

• - Rotating the first countermass about the first mass rotation axis, whereby from the same viewing perspective the direction of rotation of the first countermass is opposite to the direction of rotation of the first mass.

The above-mentioned embodiment achieves the following advantage: If an undesired rotation of the machine part occurs, a rotation that cannot be prevented despite the conservation of angular momentum of the rotating first mass, then a precessional force occurs on the first mass, which is moved in a gyroscopic manner. This precessional force, which is transverse to both the first mass rotation axis and the force tilting the gyro, causes an incorrect movement in the form of a rotation of the machine part. In other words: An undesired rotation of the machine part deflects the gyro axis and the gyro, formed from the rotating first mass, reacts in a precessional movement, which in turn leads to an incorrect movement of the machine part. This effect is neutralized by the first counter mass mentioned and the described rotation of the first counter mass. The first counter mass also reacts in the manner described above as the first mass, except that the precessional movement is opposite and precessional forces are opposite and neutralize each other. The first counter mass preferably has the same angular momentum as the first mass during rotation. The first mass and the first counter mass are preferably coupled symmetrically to the machine part, on opposite sides.

• - Rotieren der zweiten Masse um eine zweite Masse-Drehachse, die quer, insbesondere vertikal, zu der ersten Masse-Drehachse steht und die quer, insbesondere vertikal, zu der zumindest einen Maschinenteil-Drehachse, steht.

In a further embodiment, a second mass rotatable as a gyroscope is coupled to the machine part and the method further comprises:

• - Rotating the second mass about a second mass rotation axis which is transverse, in particular vertical, to the first mass rotation axis and which is transverse, in particular vertical, to the at least one machine part rotation axis.

In the above-mentioned embodiment, three undesirable rotational degrees of freedom of the machine part are suppressed, as explained below in examples.

• - Rotieren der zweiten Gegenmasse um die zweite Masse-Drehachse, wobei aus derselben Betrachtungsperspektive die Drehrichtung der zweiten Gegenmasse gegenläufig ist zu der die Drehrichtung der zweiten Masse.

In a further development of the above-mentioned embodiment, a second counter mass that can be rotated as a gyroscope is coupled to the machine part, which counter mass can be rotated about the same second mass rotation axis as the second mass and which is coupled to a side of the machine part facing away from the rotatable first mass. The method further comprises:

• - Rotating the second countermass about the second mass rotation axis, whereby from the same viewing perspective the direction of rotation of the second countermass is opposite to the direction of rotation of the second mass.

The mentioned second countermass has the same functions and advantages as a first countermass explained above.

• - ein in eine Translationsrichtung verfahrbares Portal,
• - einen an dem Portal starr befestigten ersten Motor,
• - eine erste Masse, die von dem ersten Motor um eine erste Masse-Drehachse kreiselförmig rotierbar ist, d.h. in eine Kreisel-Rotation versetzbar ist, wobei die erste Masse-Drehachse in die Translationsrichtung ausgerichtet ist.

In a further aspect, the invention relates to a coordinate measuring machine comprising:

• - a portal that can be moved in a translation direction,
• - a first motor rigidly attached to the portal,
• - a first mass which can be rotated in a gyroscopic manner about a first mass rotation axis by the first motor, ie can be set into a gyroscopic rotation, wherein the first mass rotation axis is aligned in the translation direction.

• - einen Antrieb, durch welchen eine Antriebskraft in das Maschinenteil in Translationsrichtung eingeleitet werden kann,
• - eine Steuerung/Regelung zur Steuerung/Regelung der Winkelgeschwindigkeit der ersten Masse und gegebenenfalls einer weiterhin vorhanden, unten genannten zweiten Masse. Durch genannte Steuerung kann der Drehimpuls der Masse eingestellt werden.

The machine may have additional components:

• - a drive through which a driving force can be introduced into the machine part in the translational direction,
• - a control/regulation for controlling/regulating the angular velocity of the first mass and, if applicable, of a second mass mentioned below. The angular momentum of the mass can be adjusted by means of said control.

Said machine can have all structural components that have already been explained above with reference to a method according to the invention. Likewise, the machine can be set up to carry out any of the methods mentioned above, in a general or specific embodiment.

The fact that the first mass rotation axis is aligned in the translation direction has the advantage that two undesirable rotations of the machine part, the are considered particularly undesirable, can be reduced or suppressed.

In a further embodiment, the motor and the first mass are positioned such that the center of gravity of a combination of the motor and the first mass lies on a vector of a force by means of which the machine part can be moved in the translation direction. This provides the advantage that a combination of motor and first mass does not contribute to the eccentricity of the center of gravity of the machine part relative to the acting force or even increases it.

• - einen an dem Maschinenteil starr befestigten zweiten Motor,
• - eine zweite Masse, die von dem zweiten Motor um eine zweite Masse-Drehachse kreiselförmig rotierbar ist.

In one embodiment, the machine comprises:

• - a second motor rigidly attached to the machine part,
• - a second mass which can be rotated in a gyroscopic manner by the second motor about a second mass rotation axis.

In a further embodiment, the first mass and/or the second mass, if the second mass is also present, are vacuum-encapsulated. This reduces friction with the ambient air. When the machine is in operation, the masses are usually rotated at high angular speeds. The above-mentioned embodiment allows this to be done with less friction and in a more energy-efficient manner. In a special variant, both the motor and the mass are vacuum-encapsulated.

• - einen an dem Maschinenteil starr befestigten ersten Gegenmasse-Motor,
• - eine erste Gegenmasse, die von dem ersten Gegenmasse-Motor um die erste Masse-Drehachse kreiselförmig rotierbar ist.

The realization of further objective features mentioned in the method in a machine according to the invention also relates in particular to a previously mentioned first counterweight and/or a previously mentioned second counterweight. In particular, the machine can have:

• - a first counterweight motor rigidly attached to the machine part,
• - a first countermass which can be rotated in a gyroscopic manner about the first mass rotation axis by the first countermass motor.

• - einen an dem Maschinenteil starr befestigten zweiten Gegenmasse-Motor,
• - eine zweite Gegenmasse, die von dem zweiten Gegenmasse-Motor um die zweite Masse-Drehachse kreisförmig rotier ist.

In particular, the machine may have:

• - a second counterweight motor rigidly attached to the machine part,
• - a second countermass which is circularly rotated by the second countermass motor about the second mass rotation axis.

The first counter mass can be rotated in the opposite direction to the first mass, in particular from the same viewing perspective. The second counter mass can be rotated in the opposite direction to the second mass, in particular from the same viewing perspective, as previously described in the method.

• 1 ein Koordinatenmessgerät in Portalbauweise mit möglichen rotatorischen Bewegungsfehlern des Portals,
• 2 ein erfindungsgemäßes Koordinatenmessgerät, ausschnittweise, mit einer rotierbaren Masse,
• 3 eine weitere Ausführungsform eines erfindungsgemäßen Koordinatenmessgeräts, ausschnittweise, mit einer rotierenden Masse,
• 4 ein erfindungsgemäßes Koordinatenmessgerät mit zwei rotierenden Massen und
• 5 einen Ausschnitt aus einem erfindungsgemäßen Koordinatenmessgerät mit einer ersten Masse und einer ersten Gegenmasse.

The invention is described below using exemplary embodiments. They show:

• 1 a coordinate measuring machine in gantry design with possible rotational movement errors of the gantry,
• 2 a coordinate measuring machine according to the invention, in sections, with a rotatable mass,
• 3 another embodiment of a coordinate measuring machine according to the invention, in detail, with a rotating mass,
• 4 a coordinate measuring machine according to the invention with two rotating masses and
• 5 a section of a coordinate measuring machine according to the invention with a first mass and a first counter mass.

This in 1 The coordinate measuring machine 1 shown is of gantry design. It has the base 2 and the gantry 3, which can be moved along the base and in the Y direction (see coordinate system top right). The gantry 3 has the columns 4, 5 and the traverse 6. The drive for the gantry, not shown in detail, is located within the guide 7. The quill 8 is attached to the traverse 6 and can be moved in the X direction along the traverse 6. The touch system 9 attached to the quill can be moved in the Z direction.

To move the gantry 3 in the Y direction, a force F, shown in the form of an arrow, is introduced into the base of column 4 by the drive (not shown in more detail). The center of gravity S of the gantry 3 is higher than the point of application of the force F, viewed in the Z direction. This results in at least two movement errors in the gantry. Firstly, the gantry is tilted about the machine part rotation axis MD _X. Tilting about the machine part rotation axis MD _X is also referred to as pitching. Furthermore, the gantry is rotated about the machine part rotation axis MD _Z , with the direction of rotation being shown by an arrow, as is the case with rotation about MD _X. Rotation about MD _Z is also referred to as yaw. Both undesirable rotations result from the force F acting on the gantry eccentrically to the center of gravity S. The displacement of the gantry in the Y direction is desired. It is the intended movement of the gantry. In this case, the portal does not rotate around the machine part rotation axis MD _Y , as it is not supported by the force F applied here. is generated. In principle, however, a rotation around MD _Y is possible due to other influences. The rotation around MD _Y is also referred to as rolling motion.

In 2 On the machine, the CMM 100, the portal 3 and the guide 7 of the CMM are made of 1 shown in detail. Other parts have been omitted for the sake of simplicity. The mass M1 in the form of a disk is coupled via the axis 10 to the motor 11, which drives the axis 10. The motor 11 is rigidly attached to the column 4. The mass M1 can rotate about the mass axis of rotation D _Y. If the mass M1 is rotated clockwise, as shown here, or counterclockwise, this stabilizes the gantry 3 against rotation about the machine part axes of rotation MD _X and MD _Z. If the gantry rotates about MD _X , the axis of rotation D _Y of the rotating gyroscope M1 would tilt. The gyroscope resists this due to the conservation of angular momentum. This is also the case if the gantry rotates about MD _Z.

In 3 In the machine, the CMM 200, the mass M1 is attached to the column 5 in the same way and in this case rotates about the mass rotation axis D _X . As a result, rotations of the gantry about MD _Y , which is less relevant in this example, and MD _Z are inhibited or suppressed, or at least reduced. A rotation of the gantry 3 about the machine part rotation axis MD _X is not suppressed.

In 4 The machine, the KMG 300, is therefore designed to have a second mass M2 attached to the traverse 6, which is rotated about the second mass rotation axis D _Z.

The gyro of the rotating mass M2 prevents the portal from rotating around MD _X and MD _Y. The mass M2 is connected via the axis 12 to the motor 13, which is rigidly attached to the traverse 6. When setting up the 4 Thus, the rotation of the portal 3 around MD _Y and MD _Z is prevented by the mass M1, while the rotation of the portal 3 around MD _X and MD _Y is prevented by the mass M2. The rotational degree of freedom of the portal around MD _Y is thus inhibited by both circles, with the mass M1 and with the mass M2. In the present structure, however, the rotation of the portal 3 around MD _Y is less relevant. Therefore, the embodiment of the 2 particularly advantageous. In this case, the axis of rotation D _Y of the mass M1 is aligned in the direction of translation Y and the rotations about MD _X and MD _Z caused by the translations Y are prevented with just one gyroscope. A structural embodiment not shown here is particularly advantageous in which the axis of rotation D _Y of the mass M1 and the vector of the force F are aligned.

In 5 an embodiment is shown in which, in relation to the mass M1, which is arranged in the same way as in 2 is attached, a counter mass GM1 is rotatably coupled to the portal 3, here the column 4 of the portal. The counter mass GM1 is rotatable about the same mass rotation axis D _Y as the mass M1. The counter mass GM1 is also coupled to the column 4 via a motor 14, which is a counter mass motor, and the axis 15. The counter mass motor 14 is rigidly connected to the column 4. Assume that the portal 3 consists of 2 is tilted around the axis MD _X despite the conservation of angular momentum of the gyroscope formed by the mass M1, the following happens: The rotation of the portal 3 around the axis MD _X , also shown in 1 , also causes a tilting of the gyro rotation axis D _Y of the gyro formed from M1. This is represented by the downward pointing velocity vector v ₁ , which acts on the selected mass point P ₁ and represents the deflection of the gyro. On the other hand, the mass point P ₁ of the mass M1 moves with the orbital velocity v ₂ . The result of both speeds is the velocity v ₃ , which describes the precessional movement. This results in a precession in an anti-clockwise direction around the axis D _Y . This precession movement of the gyro formed from the mass M1 would lead to a rotational movement error of the portal 3, even if this should only be small. In order to compensate for a force exerted on the portal by the precession of the gyro formed from the mass M1, the circle formed from the countermass GM1 is rotated in the opposite direction to the gyro formed from the mass M1, here clockwise. Due to the design, the selected mass point P ₂ of the counter mass GM1 is moved upwards when the mass point P ₁ is moved downwards. The movement (deflection) imposed on the mass point P ₂ by the tilting is represented by the velocity vector v ₁ '. On the other hand, the mass point P ₂ has the orbital velocity v ₂ ' and the resulting velocity is v ₃ '. The precessional movement of the gyroscope formed from the counter mass GM1 is exactly the opposite of the precessional movement of the gyroscope formed from the mass M1. The effects of the precessional movements on the portal 3 and the column 4 therefore cancel each other out.

When carrying out the method according to the invention, the following procedure is followed: The force F is applied to the portal 3 and the portal is thereby moved in the translation direction Y. At the same time, the masses M1, M2, GM1 shown in the various embodiments and the mass rotation axis shown in each case are rotated.

According to the method, it is particularly provided that the masses M1, M2, GM1 are permanently rotated at preferably high speed.

List of reference symbols

1

Machine, coordinate measuring machine

2

Base

3

portal

4, 5

columns

6

traverse

7

guide

8th

Quill

9

Touch system

10

axis

11

engine

12

axis

13

engine

14

engine

15

axis

100, 200, 300

Machine, coordinate measuring machine

DX, DY, DZ

Mass rotation axis

F

Power

GM1

Counterweight

M1, M2, M3

Dimensions

MDX, MDY, MDZ

Machine part rotation axis

P1, P2

Ground point

S

main emphasis

v1, v1'

Velocity vector of deflection

v2, v2'

Orbital velocity vector of a mass point

v3, v3'

Velocity vector of precession

Y

Translation direction

Claims (9)

Method for reducing an undesired rotation of a translationally moved machine part (3) during operation of a coordinate measuring machine (100; 200; 300) about at least one machine part axis of rotation (MD _X , MD _Z ), wherein the machine part is a movable gantry (3) and wherein the rotation occurs as a result of a force applied to generate a translational movement of the gantry (3), wherein a first mass (M1) rotatable as a gyroscope is coupled to the gantry (3), and the method comprises: - applying a force (F) in a translation direction (Y) and translationally moving the gantry (3) in the translation direction (Y) and simultaneously - rotating the first mass (M1) about a first mass axis of rotation (D _Y ) which is transverse, in particular vertical, to the at least one machine part axis of rotation (MD _X , MD _Z ) and is aligned in the translation direction (Y). Procedure according to Claim 1 , where the first mass rotation axis (D _Y ) and the force vector (F) lie on a straight line. Method according to one of the preceding claims, wherein a first countermass (GM1) which can be rotated as a gyroscope is coupled to the portal (3), which is rotatable about the same first mass rotation axis (D _Y ) as the first mass (M1) and which is coupled on a side of the portal (3) facing away from the rotatable first mass (M1), and the method further comprises: - rotating the first countermass (GM1) about the first mass rotation axis (D _Y ), wherein from the same viewing perspective the direction of rotation of the first countermass (GM1) is opposite to the direction of rotation of the first mass (M1). Method according to one of the preceding claims, wherein a second mass (M2) rotatable as a gyroscope is coupled to the portal (3), and the method further comprises: - rotating the second mass (M2) about a second mass rotation axis (D _Z ) which is transverse, in particular vertical, to the first mass rotation axis (D _y ) and which is transverse, in particular vertical, to the at least one machine part rotation axis (MD _X ). Procedure according to Claim 4 , wherein a second countermass (GM2) which can be rotated as a gyroscope is coupled to the portal (3), which can be rotated about the same second mass axis of rotation (D _Z ) as the second mass (M2) and which is coupled on a side of the portal (3) facing away from the rotatable first mass (M2), and the method further comprises: - rotating the second countermass (GM2) about the second mass axis of rotation (D _Z ), wherein from the same viewing perspective the direction of rotation of the second countermass (GM2) is opposite to the direction of rotation of the second mass (M2). Coordinate measuring machine (100; 200; 300), comprising - a portal (3) movable in a translation direction (Y), - a first motor (11) rigidly attached to the portal, - a first mass (M1) which is gyroscopically rotatable by the first motor (11) about a first mass rotation axis (D _Y ), wherein the first mass rotation axis (D _Y ) is aligned in the translation direction (Y). Coordinate measuring machine (100) according to Claim 6 , wherein the first motor (11) and the first mass (M1) are positioned such that the center of gravity of a combination of the first motor (11) and the first mass lies on a vector of a force (F) by means of which the portal (3) can be moved in the translation direction (Y). Coordinate measuring machine (300) according to one of the Claims 6 - 7 , comprising - a second motor (13) rigidly attached to the portal, - a second mass (M2) which can be rotated in a gyroscopic manner by the second motor (13) about a second mass rotation axis (D _Z ). Coordinate measuring machine (100; 200; 300) according to one of the Claims 6 - 8th , wherein the first mass (M1) and/or, if present, the second mass (M2) are vacuum-encapsulated.

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