DD255300A5 - workpiece positioning - Google Patents

Abstract

The invention relates to an automatically operating device for workpiece positioning, d. H. for centering and aligning workpieces, especially in measuring equipment. A measuring device is provided with a turntable 4, which is horizontally displaceable and pivotable to perform a centering and straightening process. The turntable 4 is supported at three points A, B, P, of which P is fixed and the other two A, B are vertically adjustable by means of motor-driven lifting devices. The centering and straightening is done automatically by means of a computer 72 which calculates the required horizontal and pivoting movements of the turntable 4 from the data obtained by scanning the Werkstueckoberflaeche with a Meßfuehler 12. Fig. 1

Description

For this 7 pages drawings

Field of application of the invention

The invention relates to a workpiece positioning device for centering and aligning a workpiece on a turntable, especially in a measuring device.

Characteristic of the known state of the art

There is known a measuring device in which a workpiece is positioned on a turntable and measurements are made by rotating the turntable while a sensor scans the surface of the workpiece. In general, it is necessary to perform an operation known as centering and straightening, wherein the turntable is horizontally displaced and tilted to bring the workpiece to the desired position, usually to match a required axis of the workpiece with the axis of rotation of the turntable Furthermore, it is extremely desirable that the centering and straightening be done automatically, so that it can be performed effectively and quickly. A measuring device in which the centering and straightening can be performed automatically is already known and commercially available. In the known device, the turntable, which is circular, is mounted on a support structure which includes a spherically curved support surface which allows for universal tilting movement of the turntable about a point which is above the working surface of the turntable and in a known horizontal plane. Two jacks arranged under the turntable at an angle of 90 ° to each other serve to cause the tilting movement about the respective orthogonal axes which are in the above-mentioned horizontal plane. Springs depress the turntable so that it remains in contact with the lifters and the spherically curved bearing surface remains in contact with a counter-bearing surface, which in one embodiment comprises a ring of balls inserted into the support structure. The support structure is mounted for rotation of the turntable on a spindle, wherein the horizontal movement of the support structure is effected by a further bearing, whereby the centering operation can be performed.

In the device of the prior art, after the workpiece to be tested has been placed on the turntable, the centering and straightening is performed by first determining the position of the center of the portion of the workpiece surface which is in the horizontal plane containing the Point by which the turntable can be tilted contains. This determination is made by bringing a stylus associated with the device into contact with the workpiece surface in this horizontal plane and driving the spindle so that the workpiece rotates about the spindle axis. The degree of eccentricity between the axis of rotation of the workpiece (or spindle axis) and the position of the center of the workpiece surface in this plane can then be determined by the signals given by a probe to which the stylus is connected. Thereafter, the support structure for the turntable is shifted horizontally to the spindle to bring the particular center of the workpiece surface into alignment with the axis of the spindle. This completes the centering process for this layer. The straightening is performed by moving the stylus to a different horizontal plane, driving the spindle so that the workpiece rotates, and determining the eccentricity of the center of the workpiece surface in that horizontal plane with respect to the spindle axis, given by the probe Signals are used. After this eccentricity has been determined, the levers are actuated to the extent necessary to align the center of the workpiece surface in the second horizontal plane with the rotational axis of the turntable (the spindle axis). This completes the straightening process as well as centering and straightening. Since the tilting movement of the turntable, which takes place during this straightening process, is centered at a point of the first horizontal plane, which has been brought into agreement with the spindle axis by the centering operation, this match is not canceled by the straightening operation

 This device has a number of disadvantages.

First, each centering operation must be performed by scanning the workpiece surface located in the same stationary horizontal plane including the tilting center of the turntable; in some cases, the workpiece does not have a surface in this plane that can be scanned. This is a significant disadvantage in workpieces of complicated shape, such as crankshafts.

Secondly, the center of gravity of the workpiece must always be within the 90-degree sector of the turntable defined by the position of the two lifters: placing the center of gravity outside this sector would produce a torque on the turntable which would cause the turntable to be out of contact with the turntable advised these lifters. Third, making the bearing surface on which the turntable is located is difficult and costly with the degree of accuracy required.

Object of the invention

The present invention provides a device with which one or more of these problems can be eliminated.

Explanation of the essence of the invention

One aspect of the invention relates to a workpiece positioning device with a turntable for receiving the workpiece and a computer with which a centering and straightening process can be performed in which any decentering of the workpiece resulting from the tilting of the turntable for straightening purposes is compensated. Thus, with the device constructed in accordance with this aspect of the invention, centering and alignment can be performed with respect to all horizontal planes without being limited to a single horizontal plane containing the tilting center of the turntable, as in the prior art device described above Technique is the case.

Another aspect of the invention relates to a workpiece positioning device having a workpiece turntable which rests on three points located at the tips of a triangle, preferably an equilateral triangle in which the center of the turntable lies, at least two of the points in height are adjustable, and a computer for performing the centering and straightening process, in which the height adjustment of one or more of the points takes place. Another aspect of the invention relates to a method or apparatus for performing the centering, wherein the workpiece is scanned by a scanner and the operation is performed by controlling the electronic controller in accordance with a particular algorithm. Another aspect of the present invention relates to a device having a turntable for supporting a workpiece, which is pivotable about a point or axes below the surface for performing the alignment, and an electronic control device for this pivoting movement. The point or intersection of the axes is preferably offset from the axis of rotation of the turntable

 Other aspects of the invention will become apparent from the following description and claims.

embodiment

The invention will be explained in more detail below with reference to an embodiment. In the accompanying drawings show:

Fig. 1: a perspective view of a device according to the invention;

Fig. 2 is a perspective view of a turntable support structure included in the apparatus of Fig. 1; 3 shows a section through a part of the support structure according to FIG. 2, but likewise the turntable is shown; Fig. 4 is a simplified block diagram of a control system associated with the apparatus of Fig. 1; 5a to 5d: the graphic representation of a centering and straightening process; and FIGS. 6 to 9 are graphs for a better understanding of the calculations performed by the control system for performing the centering and straightening operation shown in FIG.

Referring to Fig. 1, a measuring device comprises a workbench 2 carried by a frame 3 (of which only the feet are visible in Fig. 1). The frame 3 carries a turntable 4 on which a workpiece can be mounted. A vertical post 6 carries a motor driven, vertically displaceable carriage 8. A stylus 10 is attached to one end of a pivoting arm 12, by which the posture of the stylus can be changed and which, in turn, is supported at the end of a trolley 8 carried horizontally (radially) Arms 14 is held. Measurements on a workpiece are made by causing the stylus 10 to rotate across the surface of the workpiece by rotating the turntable or by radial or vertical movement of the stylus.

As shown in Figs. 2 and 3, the support structure for the turntable 4 comprises a support 16 supported by a pulley 18 which is fixed to a motor-driven spindle 20. A bearing 21 schematically represented in FIG. 3 by dashed lines accommodates the spindle 20 for the purpose of rotation about its own, vertical axis 23. The bearing 21 is mounted in frame 3 and is preferably constructed as described in GB-PS 2178805 A. A set of ball bearings 22 in a disc-shaped cage 24 is housed between the support 16 and the disc 18 to allow horizontal movement of the support 16 relative to the disc 18. This movement is carried out along the orthogonal x and y axes with the motors 26x, 26y mounted on the support 167 and driving respectively the alternating drive rods 28x and 28y via the gearboxes 3Ox and 3Oy, which may comprise, for example, worm gears , The drive rods 28χ and 28y are respectively driven along the x and y axes when the respective motors are turned on. A hub piece 32, which is secured to the upper end of the spindle 20, which projects through an opening 34 in the center of the support 16, has the flats 32x and 32y, which are respectively in contact with the ends of the drive rods 28x and 28y and in right angles to the x or y axis. A tension spring 36, one end of which is connected to the hub piece 32 and the other end to the column 38 which is mounted on the support 16, holds the ends of the respective drive rods 28x and 28y in contact with the flats 32x and 32y. With the help of the motors 26x and 26y and the force of the spring 36, the support 16 can therefore move in any direction along the x and y axis at precisely defined intervals. The guide plates 40x and 40y, through which the drive rods 28x and 28y respectively pass, have slots 42 for receiving the guide pins 44 held by the gear boxes 3Ox and 3Oy. A ball 46 mounted in a recess in the upper end of the column 38 supports the turntable 4 to allow universal pivotal movement about the point P.

At the points A and B, the turntable 4 is mounted on the balls 50 a and 50 b via the spacers 52 (only Fig. 3) which are mounted on the underside of the turntable 4 and rest on the balls 50 a and 50 b. The lever plates 54a, 54b, which are attached to the angles 56 for pivotal movement about the horizontal axes 58 (at right angles to the plane of the paper sheet of Figure 3), have the recesses 60a, 60b in which the balls 50 a, 50 b are recorded accordingly.

The motors 62a, 62b drive the elevators 64a, 64b (only Fig. 3) via the gear boxes 66a, 66b to pivot the lever plates 54a, 54b up and down about their pivot axis 58. The operation of the motor 62a thus causes the turntable to be tilted about an axis connecting the points P and B, and actuation of the motor 62b causes the turntable 4 to be tilted about an axis connecting the points P and A , These axes pass through the centers of the balls 46,50a and 50b.

The points ABP are at the vertices of an equilateral triangle whose center C coincides with the mean of the turntable 4, i. the points ABP are arranged symmetrically with respect to point C. This results in the maximum area of the turntable in which a workpiece can be positioned without causing instability of the turntable. Consequently, the axes PA and PB about which the turntable is tiltable are at an angle of 60 degrees to each other.

The tension springs 68 hold the turntable down so that the spacers 52 remain in contact with the balls 50a and 50b, and the tension springs 70 hold the lever plates 54a and 54b down so that they remain in contact with the lifters 64a, 64b.

A mounted on the disc 18 cylindrical wall 69 encloses the support structure described above. As can be seen in the simplified block diagram of Fig. 4, the motors 26x, 26y for centering and the motors 62a, 62b for directing are controlled by a computer 72 which is triggered by a sensor 73 which is responsive to the stylus 10, Receive input data. An operator-controlled keyboard 75 is provided to provide instructions to the computer 72. The computer 72 also controls a motor 74 which drives the spindle 20 for rotation of the turntable (O-axis), a motor 76 for raising and lowering the carriage 8 on the stand 6 (z-axis), and a motor 78, the the arm 14 in the radial direction (r-axis) drives to bring the stylus 10 with the workpiece surface in and out of contact. Furthermore, the sensors 80,82 and 84 supply the computer 72 with data on the angular position of the turntable 4, the vertical position of the carriage 8 and the radial position of the arm 14. A display device 86 and a memory 88 are also connected to the computer system 72, wherein the Memory 88 stores the data and programs received, after which the computer 72 operates. The computing system 72 may include one or more computers. The movements performed by the turntable 4 to achieve centering and alignment of a workpiece will be understood by FIGS. 5a to 5d. For clarity, Fig. 5 illustrates a cylindrical workpiece 100 positioned within the triangle ABP on the turntable 4. The workpiece 100 rests on an end 102 that is straight but is likely to be at a slight angle (greatly exaggerated in FIG. 5) to the radial plane such that the axis 104 of the workpiece 100 is at an angle to the vertical axis of rotation 23 of the spindle 20 is located. The sequence of steps performed in the centering and straightening process, shown in FIG. 5, involves first the rotation of the turntable 4, the stylus 10 being arranged to scan the surface of the workpiece 100 in a horizontal plane 108. The calculator 72 receives the output data from the probes (80, 73, 84) and calculates the magnitude and direction of the displacement between the center 110 of the workpiece in the plane 108 and the axis 23 using a corresponding algorithm. The polar signals output by the probes Parameters are transferred to a conceptual Cartesian coordinate system (u, v), and assuming that N points on the surface are scanned with the coordinates (uj, V ₁ ), the centers (u ₀ , v ₀ ) and the radius R of the Surface using a modified least squares criterion by minimizing the sum:

N .J ₁ [(Ui - u _o ) ² + (v, - V ₀ ) ² - R ² ] ²

calculated.

After the computer has calculated the center, it triggers the motors 26x and 26y to match, if necessary, point 110 with the axis 23, as shown in Fig. 5b.

The next step for the turntable 4 is to be rotated, with the stylus 10 arranged so that the surface of the workpiece is scanned in another horizontal plane 112 which is a certain distance from the plane 108 in the Again, using the appropriate algorithm, the computing device 72 determines the location of the center of the workpiece in the plane 112. Thereafter, the computing device 72 calculates the angular movement of the turntable 4 and the workpiece 100 that is necessary to bring the workpiece from the position shown in Fig. 5 b in the position shown in Fig. 5c, in which the axis 104 of the workpiece is parallel to the axis 23 of the spindle. This calculation will be described later. As can be seen in Fig. 5c, it follows from this angular or tilting movement that point 110 is again shifted from the axis 23. The last step is to perform a second centering operation, in which the position of the axis 104 of the workpiece relative to the axis 23 is again determined using the appropriate algorithm mentioned above and the motors 26x and 26y are again triggered to rotate the axis 104 in accordance with FIG the axis 23, as shown in Fig. 5 d to bring. Although the foregoing description of Fig. 5 has been given for the sake of simplicity on the basis that the various steps are performed in a particular order, this is not essential, and in practice centering and straightening can be accomplished by first in the planes 100 and 112 measurements are taken, with the workpiece 100 and the turntable 4 are in the position shown in Figure 5a, and then the motors 26x and 26y and 62a and 62b are triggered simultaneously or in any order, but preferably in the Order to first center the workpiece and then direct it to meet the conditions shown in Fig. 5d.

The following describes the calculations of the horizontal and tilting movements that must be performed by the turntable 4 to achieve centering and straightening. In the following description, the motors 26x and 26y will be referred to as the motors χ and y, and the motors 62a and 62b as the motors a and b. Although the part may have any shape, provided that the areas to be evaluated have a regular profile, it is again convenient for simplicity to consider the case of centering and aligning a cylindrical workpiece, such as that shown in FIG Workpiece 100, since the axis of a cylinder is easy to determine.

For the following discussions it is convenient to refer all motions to a Cartesian legal system X, Y and Z with the unit vectors i, j and k. The origin of the coordinate system is chosen to coincide with the fixed point P, and the x-axis is chosen to bisect the line connecting the two points A and B. The coordinate system is shown in Figure 6, where the Z-axis is at right angles to the plane of the paper sheet, and also in Figure 2.

A centering of the table is achieved by breaking the required movement with respect to the X- and Y-axis in parallel to the line of action of the motors χ and y running movements.

Let the required centering vector be Cii + C ₂ J, and let the unit vectors parallel to the lines of action of the motors χ and y be e _x and e _y , respectively. From the geometry one can see then that

C ₁ I + C ₂ J = -k [(Ci-c ₂ ) e _x + (c, + c ₂ ) e _y ], (1)

where k = 2~ ^{1 / 2} .

To consider the straightening process of a table placed on the table, it is convenient to introduce two more variables Θ-ΐ and Θ ₂ , where Q _{1 is} the tilt angle of the table surface about the X axis and Θ ₂ the corresponding angle around the Y axis. The height of each point (X ₁ , Y ₁ ) on the surface of the table with respect to its height in a horizontal surface is thus given by

Z ₁ = XitanQ-f + Y ^ nQ ₂ (2)

Now, with the introduction of the parameters Ti and T ₂ , as shown in FIG. 6, and with the designation of the incremental heights of the points A and B as Z _A , Z _8, the equations result

Z _A = T ^ nQ ₁ + T ₂ tan9 ₂ · (3a)

Z ₈ = T ^ nQ ₁ - T ₂ tan0 ₂ (3b)

From these equations one can calculate the incremental heights of A and B, above the horizontal plane by P in the form of the tilt angles O ₁ and Θ ₂ .

As can be seen from Fig. 6, the values of T ₁ and T ₂ are dependent on the angle APB between the axes AP and BP, by which the turntable can be tilted. The calculations performed by the computer 72 during the execution of the straightening process thus depend on the angle APB.

Before proceeding, it is necessary to take a closer look at the actual mechanism by which points A and B in the vertical plane are moved by means of the motors a and b in the preferred embodiment.

As shown by way of example in Figure 7, the distance between the axis 58 and the center 51 of the ball bearing 50a or 50b is 12 millimeters and between the axis 58 and the point of contact 55 of the jack 64a or 64b with the lever 54a or 54b 36 millimeters.

Referring to Fig. 8, it can be seen that when the lifting device 64a or 64b is screwed up by a height ζ, the center of the ball 50a or 50b moves through a height Sz. You can see that

z = 36tane * (4)

δζ = 12sina,

whence

z = 366z / 12 ² -8z ² ) V2 (5 a)

ζ = 3δζ - 3δζ ³ / (2 χ 12 ² ) + 3 ² δζ ⁵ / (2 ³ χ 12 ⁴ ) + ... (5b)

follows.

Assuming that the table 4 is initially horizontal and a cylinder is measured in two heights (Z ₁₁ Z ₂ ), the centers of the two planes being Ia b ₁ , Z ₁ ) and (a ₂ , b ₂ , z ₂ ) result, as shown in Fig. 9. It can be seen that every point at height Z and on the axis of the cylinder has coordinates in the chosen system given by

X = [(a ₂ - _ai) / (z ₂ - z _1)] + Z ^ _ai Y = Kb ₂ -D ₁₎ Z (Z ₂ -Z _1)] Z + ₁ Ij

Writing h = (z ₂ - Z ₁ ) and comparing these equations with equations (2) yields

9i = (a ₂ tan8 = (b ₂ - b ^ / h

The incremental heights δΖ _Α , 6Z ₈ , through which the points A and B must be moved in order to compensate for these angles, are given by Equations (3), namely

6Z _A = T ₁ tan Q ₁ + T ₂ tan0 ₂ δΖ _Β = T ₁ tan Θ, - T ₂ tan Θ ₂

and from equation (5), the heights by which the winch jacks must be raised are found:

Z = _A 36Z _A / (12 ² -6Z _A ²⁾ V2 Z = _{8 3δΖ} Β / (12 ² - _δΖ Β ^{2) from _1/2}

Using the binominal series expansion of these equations and breaking the series at the second term results

Z _A = 3δΖ _Α + ρδΖ _Α ³ Z _B = 3δΖ _Β + ρδΖ _Β ³ ₍

where ρ = 1.1331161 χ 10 ~ ² and includes a correction for the tears of the rows.

The number of revolutions of the motors a and b required for alignment can thus be easily determined using the calculations given above. In addition, the number of revolutions of the motors χ and y required for centering is also easy to calculate. Both calculations are performed by the calculator 72, and the results are used to drive the motors a, b, χ and y.

Thus, the illustrated embodiment has the significant advantages that the planes 108 and 112 shown in FIG. 5, in which the surface of the workpiece is measured for centering and straightening purposes, can be arbitrarily arranged within the working range of the probes 73 and 84. The workpiece can be positioned so that its center of gravity is anywhere within the triangle ABP, which is significantly larger than the corresponding area in the prior art device, and is symmetrical about the center of the turntable much cheaper. Since the turntable is supported at three points, two of which are height-adjustable to allow for tilting for directional purposes, the need for expensive large spherically curved bearing surfaces is eliminated as in the prior art.

The described device has the combined advantage that the centering and straightening process can be carried out automatically, that the mechanical structure of the turntable and its drive can be relatively simple, that the turntable has a high degree of stability and that a greater variety of workpiece types can be assessed ,

In addition, the aspect of the invention, which relates to the implementation of measurements in planes which are located at a certain distance from the tilting center or the axes, find application in a measuring device, in which the workpiece does not rest on a work table, but in a Clamping device or the like is held, which can be rotated about an axis, but not about a vertical, but for example about a horizontal axis.

The invention is not limited to the scanning of the outer surfaces of the workpiece (such as the bearing surfaces of a crankshaft), but may also be used when scanning inner surfaces (such as the input and output side bearing receivers of a transmission housing).

Sometimes, the centers of two sections of the workpiece (such as two bearing surfaces of a crankshaft) should not be aligned, but a point of the workpiece centered on the axis of the turntable and a flat surface of the workpiece to be adjusted by adjusting it perpendicular to the axis. For example, it may happen that an engine piston should be centered and directed by centering the piston crown and bringing the lower edge of the piston skirt at a right angle to the axis. In this case, not the center of a second portion of the workpiece but the inclination of a second portion of the workpiece or a reference surface fixed thereto (such as the surface of the turntable on which the piston rests) is determined. Then the specific center can be centered and then the slope adjusted; and then the center can be re-centered to compensate for decentrations caused by the tilt adjustment.

The invention is not limited to use with workpieces having circular parts to be scanned, but may be applied to workpieces having cross sections of other shapes to be scanned, such as rectangular, triangular, elliptical and hexagonal.

For example, if the workpiece is cylindrical, it is not necessary to scan the circular profile of the workpiece in two planes spaced apart from each other, but instead the probe may be guided along a helical line relative to the workpiece surface and the extent of the transverse - and tilt adjustment can be determined afterwards.

The arrangement of probe 10, support structure 12, 14, and the control system shown in Figure 4 are preferably as described in our co-pending application filed concurrently herewith, with priority to British Patent Application No. 8605324 filed Mar. 4, 1986 and Hugh Rogers Lane and Peter Dean Onyon is invented as an inventor. With this arrangement, a probe having a high resolving power and a small operating range is mounted on a radially movable arm which is driven under computer control by responding to the output of the probe by means of a motor, so that the probe can automatically follow a workpiece surface having a large variety of shapes. In particular, the probe may have a resolving power of up to about 12 nanometers over a range of about 0.4 mm, and the radially movable arm may have a range of motion of about 200 mm and be equipped with a position sensing system having a resolving power of about 200 nanometers. By this arrangement, the centering and straightening process is simplified to the effect that a precise pre-positioning of the workpiece on the turntable is not necessary, since the sensor system of our aforementioned co-pending patent application each centering and misalignment within the range of possible centering and Can accommodate the directional settings of the turntable.

Claims (17)

A workpiece positioning device for centering and aligning a workpiece on a turntable comprising a support rotatable about a predetermined axis, a workpiece holder mounted thereon for rotation on the rotatable support, a first, the receiver for tilting in each direction relative to the support supporting the rotatable support; a second support supporting the support for transverse movement relative to the rotatable support, first and second actuators for respectively triggering the tilting and traversing movement, a third drive means for rotating the rotatable supports, a surface sensor thus mounted in that it moves substantially parallel to and on the axis to and from the axis, fourth drive means for triggering the movement of the probe, the surface probe arranged to clamp the workpiece surface during a movement of the probe traverses and scans relative motion between the probe and the workpiece, and includes a computer responsive to the probe and including program means for detecting centering and aiming errors and for triggering the first and second drive means to perform centering and straightening correction CHARACTERIZED IN THAT the first supporting device comprises three supporting elements (46, 50 a, 50 b) which fix the receiving device (4) at only three points (A, B, P) at the tips of a triangle (A, P, B) within which the center (C) of the Werkstückaufnamevorrichtung (4) is arranged, wherein the first drive member (62 a, 62 b) can be operated so that at least two of the support elements (50 a, 50 b) are adjusted, so that the adjustment one of the support elements (50a, 50b) tilts the receiving device (4) about a corresponding tilting axis (PS or PA), which substantially between the other two elements (46 and 50 b or 50a), and characterized in that the program means is adapted to control the first drive member (62, 62b) in response to the angle (PAB) between the tilting axes (PB, PA) and the second drive means (26x, 26y) is controlled in response to the directional errors. 2. Device according to claim 1, characterized in that the angle (PAB) between the tilting axes (PA, PB) is not a right angle. 3. Device according to claim 2, characterized in that the points (P, A, B) are arranged at the tips of an equilateral triangle, wherein the angle (PAB) is thereby 60 degrees. 4. Device according to claim 3, characterized in that the points (P, A, B) in relation to the center (C) of the workpiece receiving device (4) are arranged symmetrically. 5. Device according to claim 4, characterized in that only two of the three support elements (50 a, 50 b) are adjustable and the third of the three support element (46) is fixed. 6. Device according to claim 5, characterized in that the first drive member comprises the first and the second motor (62 a, 62 b) for triggering the tilting movement about the first and the second tilting axis (PB, PA). 7. Device according to one of the preceding claims, characterized in that the second drive member comprises the first and the second motor (26 x, 26 y) for triggering the transverse movement in the corresponding orthogonal directions (x, y). 8. Device according to claim 7, characterized in that the orthogonal directions (x, y) are divided by a line which extends at the same distance from at least two support elements (50 a, 50 b) and by the third support element (46). 9. Device according to one of the preceding claims, characterized in that the predetermined axis (23) extends vertically. 10. Device according to claim 9, characterized in that the workpiece receiving device (4) is a turntable. 11. Device according to one of the preceding claims, characterized in that the program means is designed so that a centering and alignment correction operation is performed, wherein the centers of the workpiece (100) in the first and second planes (108,112) perpendicular to the predetermined Axis (23) and at certain distances from each other along this axis are determined and the first and second drive member (62 a, 62 b, 26x, 26y) are triggered depending on the calculation. 12. The device according to claim 11, characterized in that the program means for controlling the first and second drive member (62 a, 62 b, 26x, 26y) in response to a first calculation in which the transverse movement of the workpiece receiving device (4), the necessary is determined to bring the first of the workpiece centers with the axis (23) in accordance; a second calculation in which the tilting of the device (4) necessary to align a line connecting the workpiece centers parallel to the predetermined axis (23) is determined; and a third calculation, wherein the transverse movement of the device (4), which is necessary to compensate for shifts of the first workpiece center point as a result of the tilting, is designed. 13. The device according to claim 12, characterized in that the program means is designed for performing a centering and directional sequence, wherein the first calculation is performed and the second drive member (26 x, 26 y) is triggered accordingly to the first workpiece center with the predetermined Axis (23) to match, and then the position of the second center is determined, the second and the third calculation are performed and the first and the second drive means (62 a, 62 b; 26x, 26y) corresponding to the second and third Calculation be triggered. 14. The device according to claim 13, characterized in that the program device is designed so that the second drive member (26 x, 26 y) is triggered according to the second calculation after completion of the triggering of the first drive member (62 a, 62 b). 15. A device according to claim 13, characterized in that the program means is designed so that the second drive member (26x, 26y) is triggered according to the third calculation simultaneously with the triggering of the first drive member (62 a, 62 b) according to the second calculation , 16. The device according to claim 13, characterized in that the program device is designed so that the first, second and third calculation and the triggering of the first and second Antriebsö'rgans are performed such that the first and second drive member (62 a, 62 b; 26x, 26y) are triggered simultaneously so that both workpiece centers are aligned with the predetermined axis (23). 17. Device according to one of the preceding claims, characterized in that the Progrämmeinrichtung is also designed so that a measuring operation can be performed on the workpiece by the third and fourth drive member (74,76,78) are triggered to the sensor to causing an area of the workpiece to be traversed, the output signals being stored by the probe to provide data related to the area.