Method for positioning a center point on a geometric axis in a machine tool

In order to improve a method for positioning a centre point of a second machine tool unit of a machine tool on a geometric axis of a first machine tool unit of the machine tool, wherein the second machine tool unit has a circular path concentric with the centre point, and wherein the first machine tool unit has a component that is rotatable about the geometric axis, in such a way that said method can be performed by an operator easily, reliably and within a short timeframe, it is proposed that a measuring unit is arranged in a defined manner relative to the geometric axis and the position of the circular path relative to the geometric axis is established using the measuring unit, that the position of the centre point of the circular path in the geometric plane relative to the geometric axis is calculated, and that adjustment paths in the geometric plane, which are associated with the adjustment directions, for positioning the centre point on the geometric axis are calculated, and that the machine tool units are moved relative to one another in accordance with these adjustment paths.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This patent application claims the benefit of German application No. 10 2017 121 087.3, filed Sep. 12, 2017, the teachings and disclosure of which are hereby incorporated in their entirety by reference thereto.

BACKGROUND OF THE INVENTION

The invention relates to a method for positioning a centre point of a second machine tool unit of a machine tool on a geometric axis of a first machine tool unit of the machine tool, wherein the second machine tool unit has a circular path that is concentric with the centre point, is scannable, and lies on a circular cylindrical surface, and wherein the first machine tool unit comprises a component that is rotatable about an axis of rotation coincident with the geometric axis.

A method of this kind is usually performed iteratively and manually, wherein the duration of this method is dependent on the skill of an operator of the machine tool performing this method.

SUMMARY OF THE INVENTION

The object of the invention is therefore to improve a method of kind described at the outset in such a way that said method can be performed by an operator easily, reliably and within a short timeframe.

In the case of a method of the kind described at the outset, this object is achieved in accordance with the invention in that a measuring unit is arranged on the first machine tool unit in a defined manner relative to the geometric axis and the position of the circular path in a geometric plane, defined by the circular path, relative to the geometric axis is established using the measuring unit in that the position of the circular path is ascertained by means of the measuring unit by establishing the positions of three measurement points arranged at defined angular spacings from one another over the circular path relative to the geometric axis, in that the position of the centre point of the circular path in the geometric plane relative to the geometric axis and a reference direction running through the geometric axis is calculated on the basis of the positions of the measurement points and the known radius of the circular path, and in that, using machine tool-based adjustment directions of the machine tool units relative to one another, adjustment paths in the geometric plane, which are associated with the adjustment directions, for positioning the centre point on the geometric axis are calculated, and in that the machine tool units are moved relative to one another in accordance with the adjustment paths.

The advantage of the invention can be considered to be the fact that, by means of the calculation of the centre point relative to the geometric axis and relative to the reference direction, the adjustment paths necessary in the adjustment directions for displacement of the centre point onto the geometric axis can also be calculated, and by moving the machine tool units relative to one another the centre point of the circular path can thus be moved in a simple manner, such that it lies ultimately on the geometric axis.

With regard to the determining of the positions of the three measurement points, no further details were provided in conjunction with the previous explanation of the solution according to the invention.

In principle, the positions of the measurement points could be established in a wide range of different ways using the measuring unit.

For example, it is conceivable to use three measuring units and to move these in the direction of the geometric axis so as to establish the positions of the three measurement points simultaneously.

An advantageous solution thus provides that the positions of the three measurement points are defined by pivoting the measuring unit about the geometric axis in a measurement direction corresponding to the particular measurement point and running radially relative to the geometric axis, and that the position of the particular measurement point in the corresponding measurement direction is defined by means of the measuring unit.

Here, the position of the particular measurement point could be ascertained by measuring the spacing of the measurement point from the geometric axis in the corresponding measurement direction.

An advantageous solution that is particularly easy to implement provides that the position of the particular measurement point is ascertained by measuring the spacing thereof from a reference circular path, which runs around the geometric axis, in the radial direction relative to the geometric axis.

Here, the reference circular path is preferably selected such that the radius thereof is greater than the radius of the circular path of which the position is to be ascertained.

The advantage of determining the positions of the measurement points by determining the spacing thereof from a reference circular path can be considered to be the fact that the reference circular path does not have to be fixed in respect of its absolute value, but must remain constant when determining the measurement points and merely defines a reference value for the measurement unit, and therefore the measurement unit establishes the spacing of the measurement points from the reference circular path about the geometric axis in each case proceeding from the reference value of said measuring unit.

With regard to the position of the measurement points, no further details were provided in conjunction with the determination of the positions.

An advantageous solution thus provides that the three measurement points are selected such that they lie within an angular range of 180° about the geometric axis.

The centre point of the circular path can be calculated particularly advantageously if the three measurement points are selected such that an angular range of 90° is provided between a first measurement point and a second measurement point and between the second measurement point and a third measurement point.

With regard to the determination of the machine tool-based adjustment directions relative to the positions of the measurement points or the measurement directions of the measurement points, no further details have yet been provided.

An advantageous solution provides that the machine tool-based adjustment directions are determined by arranging the position of one of the three measurement points in a geometric measurement direction running radially relative to the geometric axis and parallel to one of the adjustment directions.

An arrangement of this kind of the geometric measurement direction can be achieved for example in that an edge of the second machine tool unit defined in one of the adjustment directions has a projection in the direction of the measuring unit and therefore the measurement direction can be oriented parallel to this edge with the aid of the projection of the edge or a shadow of this edge on the measuring unit.

It is particularly simple if a first of the three measurement points is arranged in the measurement direction running through the geometric axis and parallel to one of the adjustment directions.

Another solution for determining the machine tool-based adjustment directions relative to the positions of the measurement points provides that the machine tool-based adjustment directions are determined by a first establishment of the position of the centre point of the second machine tool unit in a first determination position, a subsequent relative movement of the two machine tool units along a selected one of the adjustment directions into a second determination position, and in said second determination position a second establishment of the position of the centre point of the second machine tool unit, and that the position and the course of the selected adjustment direction is ascertained by establishing the orientation of a connecting line between the centre points in the first and second determination position, wherein in particular the course of the selected adjustment direction relative to the geometric axis is established.

In this solution it is particularly advantageous if the measurement directions in which the positions of the measurement points are established are identical in the first determination position and in the second determination position.

In order to assist the operator in moving the machine tool units relative to one another for positioning the centre point on the geometric axis in accordance with the adjustment paths, it is preferably provided that, as the machine tool units move in at least one of the adjustment directions, the at least one continuous adjustment path is determined by means of the measuring unit.

It is even better if, as the machine tool units move in the adjustment directions, the adjustment paths travelled over are determined by means of the measuring unit, such that it can be ensured in a simple manner that the calculated adjustment path is also actually travelled over.

It is preferably provided here that, in order to determine the movement of the machine tool units relative to one another in the adjustment directions, the measuring unit is positioned by pivoting about the geometric axis in measurement directions running parallel to the respective adjustment directions, such that the adjustment paths to be travelled over can thus be monitored in a simple manner using the measuring unit.

The method according to the invention can be carried out in particular if a cylinder axis of the circular cylindrical surface runs parallel to the geometric axis.

It is also preferably provided that the adjustment directions on the one hand run perpendicularly to one another and on the other hand run perpendicularly to the geometric axis.

The previously described method steps can all be carried out manually in principle.

In order to calculate the centre point of the circular path, it has proven to be particularly advantageous if positions of the measurement points established by the measuring unit are transmitted to a computer unit, which establishes the centre point of the circular path relative to the geometric axis and a reference direction running through the geometric axis, in particular since a numerical establishment of the centre point lends itself in view of the complex mathematics.

It is also preferably provided that the computer unit, using information regarding the tool machine-based adjustment directions, establishes adjustment paths in the adjustment directions for positioning the centre point on the geometric axis.

This establishment of the adjustment paths, which is preferably performed on the basis of the geometric calculations, can also be carried out particularly favourably by means of a computer unit.

In the method according to the invention, functions of the machine tool which are provided therein can be utilised even more advantageously.

It is thus preferably provided that the measuring unit is connected to the component rotatable about the axis of rotation, and that by means of a centring controller the measuring unit is pivoted about the geometric axis by means of the first machine tool unit by control thereof in order to determine the three measurement points.

This means that the function of the machine tool provided anyway can be utilised by the first machine tool unit by means of a centring controller in order to perform the pivoting of the measuring unit about the geometric axis.

It is also preferably provided that for each measurement point the position of the measurement point is established by means of the measuring unit by actuation and reading thereof by means of the centring controller and in particular is stored in the computer unit.

Furthermore, the method according to the invention can be carried out advantageously if, for determining at least one of the adjustment paths of the measuring device, as the machine tool units move relative to one another in the at least one adjustment direction the measuring unit is pivoted in a measurement direction parallel to the adjustment direction by means of the centring controller by control of the first machine tool unit.

A further advantageous embodiment of the method according to the invention provides that, by means of the centring controller, the machine tool units are moved relative to one another, by control of at least one movement unit of the machine tool units, in one of the adjustment directions from a first determination position into a second determination position, and that the position of the circular path is ascertained in the second determination position in the same way as in the first determination position, and the position of the centre point of the circular path is calculated.

No further details have yet been provided in respect of the ascertainment of the adjustment direction.

A preferred solution provides that the adjustment direction is calculated by means of the computer unit establishing the orientation of a connecting line traversing the centre point in the first determination position and the centre point in the second determination position.

In order to be able to position the centre point on the geometric axis in a simple way, it is preferably provided that the machine tool units, proceeding from the first or second determination position, are moved over an adjustment path in the calculated adjustment direction to such an extent that once the adjustment path has been travelled over in the further adjustment direction the centre point lies on the geometric axis.

In particular, the adjustment path in the further adjustment direction and the computer unit is established here on the proviso that the further adjustment direction runs perpendicularly to the adjustment direction first calculated.

So as to be able to determine in this case the movement in the further adjustment direction, it is preferably provided that a measurement direction of the measuring unit is oriented parallel to the second adjustment direction by control of the rotation of the component of the first machine tool unit by the centring controller, and the adjustment path to be travelled over in this adjustment direction is measured, and in particular is displayed to an operator.

The invention additionally relates to a machine tool comprising a first machine tool unit with a component that is rotatable about an axis of rotation coincident with a geometric axis, and comprising a second machine tool unit with a circular path concentric with a centre point and arranged on a circular cylindrical surface.

In a machine tool of this kind, so as to be able to orient the two machine tool units relative to one another in a simple way such that the centre point lies on the geometric axis, it is preferably provided that the machine tool is associated with a measuring unit which determines positions of measurement points arranged on the circular path relative to the geometric axis.

In particular, the measurement values determined by the measuring unit can be further processed in a favourable manner if the machine tool is associated with a computer unit and if the computer unit determines and stores measurement values of the measuring unit.

Here, it is preferably provided that the measurement values are transmitted to the measuring unit within the scope of a data transfer, whether wired or wireless.

It is also preferably provided that the computer unit establishes the position of the centre point relative to the geometric axis and a reference direction on the basis of the positions of measurement points arranged at defined angular spacings on the circular path and on the basis of the known radius of the circular path, such that in particular, since the centre point generally must be established numerically, there is a simple possibility for easily establishing the particular position of the centre point of the circular path.

It is additionally also provided that the computer unit establishes adjustment paths for positioning the centre point on the geometric axis using information regarding the machine tool-based adjustment directions.

This means that the computer unit, on the basis of geometric considerations, is usually able to establish the adjustment paths that are necessary in the respective adjustment directions in order to move the machine tool units relative to one another such that the centre point lies on the geometric axis.

The computer unit could in principle be a computer unit provided specifically for the positioning of the centre point on the geometric axis.

It has proven to be particularly advantageous, however, if the machine tool comprises a machine controller which is associated with the computer unit.

A particularly advantageous machine tool is one in which the measuring unit is connected to the component rotatable about the axis of rotation and in which by means of the centring controller the measuring unit for determining the three measurement points unit is pivoted about the geometric axis by means of the first machine tool by control thereof, wherein this is usually performed in the form of a position-controlled pivoting, such that the measuring unit can be oriented exactly in the respective angular positions for determining the three measurement points.

In this case it is preferably provided that in each measurement point the position of the measurement point is established by means of the measuring unit by actuation and reading by means of the centring controller and is stored in the computer unit.

In a machine tool according to the invention it is also preferably provided that the centring controller, for determining at least one of the adjustment paths as the machine tool units move relative to one another in the at least one adjustment direction, pivots the measuring unit in a measurement direction parallel to the adjustment direction by control of the first machine tool.

It is thus possible, with an orientation of the adjustment direction known to the centring controller, to orient the measuring unit such that, by means of said measuring unit, the adjustment path to be travelled over can be checked and therefore it can be checked whether the established adjustment path is also actually travelled over in this adjustment direction.

A further advantageous embodiment of the machine tool provides that the centring controller, once the position of the centre point of the circular path has been established by the computer unit in a first determination position, moves the machine tool units relative to one another by control of a movement unit of the machine tools in one of the adjustment directions from the first determination position into the second determination position, and that the computer unit in the second determination position ascertains the position of the circular path and calculates the position of the centre point of the circular path in the same way as in the first determination position.

This type of establishment of the centre points of the circular path in two different determination positions makes it possible for the computer unit to likewise determine the orientation of the adjustment direction.

In this regard it is preferably provided that the computer unit calculates the adjustment direction by establishing the orientation of a connecting line traversing the first centre point in the first determination position and traversing the centre point in the second determination position, wherein the position and orientation of the connecting line then indicate the position and orientation of the adjustment direction to be established.

In this case the centring controller can be used such that it moves the machine tool units, proceeding from the first or second determination position, in the specific adjustment direction over an adjustment path to such an extent that once the adjustment path has been travelled over in the further adjustment direction the centre point lies on the geometric axis.

In particular, it is provided in one of the above-described embodiments of the machine tool according to the invention that said machine tool operates in accordance with an embodiment of the method described in the introduction.

Further features and advantages are the subject of the following description and the presentation of some exemplary embodiments in the form of a drawing.

DETAILED DESCRIPTION OF THE INVENTION

An exemplary embodiment of a machine tool10according to the invention shown inFIG. 1comprises a machine frame denoted on the whole by12, on which a workpiece spindle unit14is arranged, wherein the workpiece spindle unit14for example comprises a motor spindle18arranged in a spindle housing16, by means of which motor spindle a spindle tube22is rotatable about a spindle axis24, wherein the spindle tube22comprises a workpiece mount26, for example a chuck, for fixing a workpiece W, which is thus likewise rotatable about the spindle axis24.

In order to machine the workpiece W, a machine bed32is arranged on the machine frame12, on which machine bed there is a first slide body34mounted movably in a Z direction parallel to the spindle axis24, wherein a second slide body36is guided on the first slide body34in an X direction running perpendicularly to the Z direction and thus also running perpendicularly to the spindle axis24. The slide bodies34and36together form a compound slide40.

A tool carrier38is arranged on the second slide body36, on which tool carrier there is arranged, for example, a tool holder denoted as a whole by42, which comprises a tool holder base44mounted on the tool carrier38and for example comprises a sleeve46, in which there is arranged a tool WZ, for example a drill.

As shown inFIG. 2, the tool holder base44of the tool holder42is adjustable relative to the tool carrier38by an adjustment unit52in an adjustment direction parallel to the X axis and is displaceable transversely to the X axis, that is to say in the direction of the Y axis, by means of adjustment units54and56arranged on either side of the tool holder base44, which adjustment units guide the tool holder base44in the X direction in the region of their longitudinal sides55and57during the adjustment of said tool holder base in the X direction by means of the adjustment unit52, wherein the tool holder base44can be fixed by screws58to the tool carrier38in a particular position, such that, once the screws58have been loosened by means of the adjustment units52and54and56, a displacement of the tool holder base44relative to the tool carrier38in the particular adjustment direction is possible.

In the case of tool holders42of this kind, the tool WZ is for example mounted concentrically with the sleeve46, and the sleeve46comprises a circular cylindrical surface48, in particular a circular cylindrical circumferential surface, the radius r of which starting from its cylinder axis Z is known.

When a tool holder42of this kind is mounted on the tool carrier38, there is the problem for exact centric machining of the workpiece W of arranging the sleeve46, with the tool WZ mounted for example concentrically therein, such that the cylinder axis Z of the sleeve46in a defined position of the tool carrier38is coincident with the spindle axis24.

As shown inFIG. 3, with mounting of the tool holder42, the situation illustrated for example inFIG. 3is usually present, i.e. that the cylinder axis Z of the circular cylindrical surface48of the sleeve46is arranged at an undefined spacing from the spindle axis24, spaced therefrom in an undefined direction, but in particular is arranged parallel thereto.

For this reason there is the need to displace the sleeve46such that the cylinder axis Z, which defines a centre point of the circular cylindrical surface48, coincides with the spindle axis24.

In this regard, in a first exemplary embodiment of the method according to the invention, a holder62is mounted in the workpiece receptacle26of the spindle tube22, as shown inFIG. 4, which holder is rotatable about the spindle axis24by means of the spindle tube22rotatable about the spindle axis26and carries a measuring unit64which has a probe tip66with which positions can be determined in a radial direction relative to the spindle axis24, which at the same time constitutes a geometric axis for the orientation of the sleeve46.

Here, the probe tip66, for example proceeding from a reference circular path RK about the spindle axis24with a reference radius R, measures the position of a circular path K arranged on the circular cylindrical surface48and defined by an intersection of this circular cylindrical surface48with a plane KE running perpendicularly to the geometric axis24, by ascertaining a radial spacing from the reference circular path RK in relation to the spindle axis24.

In order to ascertain the position of the sleeve46relative to the spindle axis24, the circular cylindrical surface48is scanned by moving the probe tip66along the circular path K, so as to determine the position thereof relative to the spindle axis24and so as to establish, on the basis of the position of the circular path K on the circular cylindrical surface48, the position of a centre point M of the circular path K determined on the cylindrical surface48by the probe tip66of the measuring unit64, said centre point being arranged on the cylinder axis Z of said circular cylindrical surface in the plane KE.

In order to simplify the ascertainment of the circular path K travelled over by means of the probe tip66at the position of the circular cylindrical surface48, a manual rotation for example of the orientation of the measuring unit64about the spindle axis24is performed, as shown inFIG. 4, until the probe tip66is movable in a first measurement plane E1for measuring the spacing of the circular path K from the reference circular path RK in a radial direction relative to the geometric axis24, which for example is oriented parallel to the X axis and runs through the geometric axis24.

In the case of manual ascertainment, the orientation parallel to the X axis is established in that for example one of the side edges55or57of the tool holder base44acted on by the adjustment units54,56is used as a reference direction and is projected in the direction of the probe tip66by shadow projection for orientation of the measuring unit64.

In the measurement plane E1thus oriented parallel to the X axis, the spacing m1from the reference circular path RK is then ascertained in a measurement direction MR1running through the measurement point P1and radially relative to the geometric axis24by means of the probe tip66scanning the circular cylindrical surface48at the measurement point P1.

The measuring device64is then pivoted manually for example about the spindle axis24through 90°, such that the probe tip66lies in a second measurement plane E2, which runs through the geometric axis24, and for measuring is movable in a measurement direction MR2running through the measurement point P2and radially relative to the geometric axis24, and in this case the spacing m2of the measurement point P2from the reference circular path RK is ascertained at the measurement point P2using the probe tip66.

Lastly, there follows for example a manual pivoting of the measuring device64through 180° relative to the reference point P1and relative to the measurement plane E1, such that the probe tip66lies in a third measurement plane E3, which runs through the geometric axis24, and for measuring is movable in this plane in a measurement direction MR3running through the measurement point P3and radially relative to the geometric axis24, such that the spacing m3from the reference circular path RK is determined by means of the probe tip66at the measurement point P3, which is exactly opposite the measurement point P1with respect to the spindle axis24(FIG. 5).

The spacings m1, m2, m3determined by the measuring unit64are transmitted for example to a computer unit68associated with the machine tool10and are stored thereby, correlated with the measurement directions MR1, MR2and MR3.

Using the spacings m1, m2and m3of the measurement points P1, P2and P3from the reference circular path RK, measured in the radial direction relative to the spindle axis24, and also using the known radius r of the circular path K, on the basis of the following three equations
(xM)2+(r+xM+A−m1)2−2xM(r+xM+A−m1)cos α=r2
(xM)2+(r+xM+A−m2)2−2xM(r+xM+A−m2)sin α=r2
(xM)2+(r+xM+A−m3)2−2xM(r+xM+A−m3)cos α=r2,
the variables of which are noted again inFIG. 6in conjunction with the circular cylindrical surface48of the sleeve46of the scanned circular path K and the reference circular path RK and the radius r of the circular cylindrical surface48, the variables xM, α and A can be ascertained, wherein for example the variable A in the approach described hereinafter is not directly relevant, and instead only the variables xM and α are used further.

The three equations are solved for example by means of the computer unit68by a numerical method in which the position of the centre point M of the scanned circular path K in relation to the spindle axis24representing the geometric axis is calculated, wherein the position of the centre point M is indicated on the one hand by the spacing xM of the centre point M from the geometric axis24and on the other hand by the angle α between the measurement plane E1or connecting line of the measurement points P1and P3and the connecting line between the geometric axis and the centre point M, as shown inFIG. 7.

On the basis of this information relating to the position of the centre point M of the circular path K scanned by the probe tip66at the circular cylindrical surface48relative to the geometric axis24, the adjustment path dx by which a displacement of the centre point M in the X direction is necessary so that said centre point subsequently is coincident with the geometric axis24can now be calculated, for example by means of the computer unit64using simple geometric calculations of the relationships shown inFIG. 8.

Furthermore, based on the premise that the Y direction runs perpendicularly to the X direction and intersects the geometric axis24, it is also possible to calculate an adjustment path dy by which a displacement of the centre point M of the scanned circular path K at the circular cylindrical surface48must be performed in order for the centre point M to lie on the geometric axis24(FIG. 8).

For the relative movement of the machine tool units14,46in accordance with the adjustment paths dx and dy, the measuring unit64is again pivoted about the spindle axis24and thus about the geometric axis until it is again in the measurement plane E1, which—as described above—was oriented such that it runs parallel to the X axis.

In this position of the measuring unit64the adjustment path dx by which the tool holder base44is to be moved in the X direction relative to the starting position can now be determined using the probe tip66, wherein this movement of the tool holder base44in the X direction once the screws58are loosened continues until the value dx is reached.

The measuring unit64is then pivoted through 90°, such that the probe tip66lies in the measurement plane E2, which is pivoted through 90° about the geometric axis24relative to the measurement plane E1.

With this measuring unit64in the measurement plane E2, the displacement of the centre point by the adjustment path dy in the Y direction can then be monitored, this displacement being implemented by actuation of the adjustment devices54and56once the screws58have been loosened.

If the displacement of the centre point M of the sleeve46is performed correctly, the centre point M, as shown inFIG. 9, ultimately thus lies on the geometric axis24, which can still be checked for example by the measuring unit64, because in this case the probe tip66of the measuring unit64must measure the same value m in all rotational positions about the geometric axis24as spacing from the reference circular path RK.

In a second exemplary embodiment of the method according to the invention a controller80associated with the machine tool10is also used in addition thereto, which controller controls the tool spindle unit14in the usual way, wherein the motor spindle18is controlled both in respect of its rotational speed and as a C axis, that is to say is controlled in respect of its rotational position (FIG. 10).

Furthermore, the machine controller80controls the compound slide40for positioning the tool carrier38relative to the workpiece W, for example both in the Z direction and in the X direction.

The centring controller82is connected to the measuring unit64either wirelessly or in a wired manner, so as to read therefrom the measurement values m1, m2and m3to be ascertained and to transfer these to a computer unit84, as will explained in detail further below, and on the other hand is coupled to the machine controller80, so as to operate the workpiece spindle unit14as C axis by means of the machine controller80and thus pivot the measuring unit64about the spindle axis24representing the geometric axis, such that it is thus possible, controlled by the centring controller82, to ascertain the spacings m1, m2and m3of the measurement points P1, P2and P3by the probe tip66of the measuring unit64from the reference circular path RK without manual intervention at said measurement points as was explained in detail in conjunction with the first exemplary embodiment.

In order to carry out the second exemplary embodiment of the method according to the invention, the methods steps explained hereinafter are performed by means of the centring controller82.

As is shown inFIG. 11, the spacing of the cylinder axis Z of the sleeve46from the spindle axis24representing the geometric axis is similarly unknown, as shown inFIG. 3, and so this spacing has to be established.

In this regard, similarly to in the first exemplary embodiment of the method according to the invention, the circular cylindrical surface48of the sleeve46along the circular path K is scanned by means of the measuring unit64held likewise by the holder62in the workpiece receptacle26, for example the chuck, wherein in the second exemplary embodiment the pivoting of the measuring unit64about the spindle axis24representing the geometric axis is now controlled by the centring controller82by control of the workpiece spindle unit14as C axis by means of the machine controller80(FIG. 12).

In addition, in contrast to the first exemplary embodiment, as shown inFIG. 12, the position of the measurement plane E1is not correlated with the X axis, and instead the position of the first measurement plane E1is selected arbitrarily by the machine controller80.

The selection of the position of the first measurement point P1is thus also arbitrary.

In the first measurement plane E1the spacing m1of the measurement point P1in the measurement direction MR1starting from the reference circular path RK is ascertained by means of the measuring unit64in the same way as described in conjunction with the first exemplary embodiment, controlled now by the centring controller82, and said spacing is transferred to the computer unit84.

Then, effected by the workpiece spindle unit14operated as C axis and controlled by the centring controller82by means of the machine controller80, the measuring unit64is pivoted starting from the measurement plane M1into the measurement plane E2, which runs at an angle of 90° to the measurement plane E1, and at the measurement point P2in the measurement direction MR2the spacing P2from the reference circular path RK in the radial direction relative to the spindle axis24representing the geometric axis is established, wherein the spacing m2is ascertained and transferred to the computer unit84.

Lastly, the measuring unit64is pivoted by the centring controller82into the measurement plane E3for ascertaining the spacing m3of the measurement point P3from the reference circular path RK in the measurement direction MR3.

With these values for the spacings m1, m2and m3and the formulas already cited in conjunction with the first exemplary embodiment, the position of the centre point M of the circular path K relative to the first measurement plane E1can be ascertained by means of the computer unit84by establishing the spacing xM of the centre point M from the geometric axis24and the angle α between the measurement plane E1and the connecting line between the centre point M and the geometric axis24, as shown inFIG. 13.

Since, in the second exemplary embodiment of the method according to the invention, the position of the X axis relative to the measurement planes E1, E2and E3is not known, it is necessary to ascertain the X axis predefined by the machine tool, in particular the compound slide40.

For this reason, the compound slide40is controlled by means of the machine controller80such that it is moved, starting from the tool holder42, from the first determination position, in which the centre point M of the circular path K has already been ascertained, for example in the direction of the X axis into a second determination position, as is shown inFIG. 14.

InFIG. 14the centre point M ascertained in the first determination position is shown, and also the centre point M′ in the second determination position, the position of which however has not yet been ascertained.

In this second determination position of the sleeve46and thus the circular path K′ over the circular cylindrical surface48, the position of the circular path K′ relative to the reference circular path RK is likewise determined, as shown inFIG. 15, by ascertaining the position of three measurement points P1′, P2′ and P3′, determined in the determination planes E1, E2and E3respectively, which for example are identical to those in the first determination position (FIG. 15).

Here, for each of the measurement points P1′, P2′, P3′ in the measurement directions MR1, MR2, MR3, the spacing m1′, m2′ and m3′ of the first measurement point P1′, of the second measurement point P2′ and of the third measurement point P3′ from the reference circular path RK in the radial direction relative to the geometric axis24is established, controlled by the centring controller82in the same way as described beforehand by pivoting the measuring unit64by means of the workpiece spindle unit14operated as C axis (FIG. 15).

With these values for the spacings m1′, m2′ and m3, the position of the centre point M′ of the circular path K′ can be established in turn by means of the computer unit84by defining the spacing of the centre point M′ from the geometric axis24, given by the value xM′, and by defining the angle α′ between the connecting line between the geometric axis24and the centre point M′ and the measurement plane E1by the centring controller82, as shown inFIG. 16.

As is shown inFIGS. 17 and 18on an enlarged scale, the computer unit84thus knows both the position of the measurement point M and the position of the measurement point M′ relative to the measurement planes E1, E2and E3.

Here, a connecting line V predefined by the movement in the X direction runs between the centre points M and M′ in any orientation relative to the measurement planes E1, E2and E3, since the position thereof was selected uncorrelated relative to the X axis.

By ascertaining the position and orientation of the connecting line V however, the computer unit84has the possibility of ascertaining the orientation and position of the X axis relative to the geometric axis24and thus also ascertaining the adjustment path dx by which the centre point M must be moved starting from the first determination position, or the adjustment path dx′ by which, the centre point M′ must be moved starting from the centre point M′ so as to position the centre points M and M′ by movement in the X direction at a point MX0, starting from which merely a displacement in the Y direction by the adjustment path dy is necessary to achieve a centring of the sleeve46relative to the geometric axis24.

Since the compound slide40is constructed such that no controlled movement in the Y direction is possible therewith by means of the machine controller80, the measuring unit64is pivoted about the spindle axis24by the centring controller82by means of the machine controller80, such that said measuring unit is in a measurement plane E4running perpendicularly to the connecting line V defining the X direction and thus parallel to the Y direction and intersects the geometric axis24.

In this position of the measuring unit64in the measurement plane E4, the centring controller82is able to measure the displacement of the sleeve46in the Y direction that is possible manually in the same way as in the first exemplary embodiment by manual adjustment of the adjustment units54,56associated with the tool holder base44.

Here, the centring controller82can then indicate the adjustment path dy as a spacing of the centre point MX0from the geometric axis24, such that the manual adjustment is possible under consideration of the adjustment path dy, until the centre point MX0is coincident with the geometric axis24.

Alternatively, however, it is also conceivable that the slide system40has a Y axis such that the centring controller82can control the Y axis by means of the machine controller80until the centre point MX0is coincident with the geometric axis24, wherein this can be implemented either by internal determination of the position in the Y direction by the machine controller or additionally with the aid of the measuring unit64and monitoring of the displacement in the Y direction by means of the measuring unit64.

Thus, the sleeve46likewise can be positioned relative to the spindle axis24with the aid of the centring controller82.