WO2006036120A1

WO2006036120A1 - Device and method for measurement in machine tools

Info

Publication number: WO2006036120A1
Application number: PCT/SE2005/001437
Authority: WO
Inventors: Anders Ramström
Original assignee: Dynamate Ab
Priority date: 2004-09-30
Filing date: 2005-09-28
Publication date: 2006-04-06
Also published as: SE527907C2; DE112005002399T5; DE112005002399B4; SE0402369D0; SE0402369L

Abstract

A measuring device (12) and a method for measurement of angles in a machine tool, wherein the measuring device (12) comprises a stone (13) which has at least one plane surface (14) and a fastening device (17) which is arranged for fastening of the measuring device (12) in the machine tool. The stone (13) is possible to angle in relation to the fastening device (17).

Description

56189 PCT Im/et

DEVICE AND METHOD FOR MEASUREMENT IN MACHINE TOOLS

Technical field

The present invention relates to a method and a device for measurements of angles in machine tools.

Prior art

Machine tools is a generic term for machines comprising machines for cutting working with a rotating tool, such as drills, lathes and milling cutters. In machine tools with a rotating tool the tool rotates around a rotational axis. In machine tools having a rotating tool it is often necessary to be able to linearly move the rotating tool in relation to a work piece that is to be worked. It is necessary to be able to secure that the linear movement really is parallel to the rotational axis. There is also a need of being able to measure angles between other angles and directions of movement in machine tools. In milling cutters it is for example common that the rotating tool can be moved in a plane perpendicular to the rotational axis of the tool.

There are many different methods for measuring angles in machine tools. Some methods are based on the use of a right- angled stone against which the motions of the machine tool are compared. The reason why stones have been used is that they are effected less by temperature than metals. There are many different sorts of stones that can be used as measuring stones. An often used sort of stone is diabase which has very good properties to be used as measuring stone. Since a few decades ago optical measuring methods have, however, had an increasing effect. An advantage with methods based on the use of right-angled stones is, however, that the measurements in some cases are simplified as one can use the fact that the stone has plane surfaces.

A problem when using right-angled stones for measurement of angles between axes is that a plane surface is required on which the stone can be placed in order to make it possible to perform the measurement. In some types of machine tools one has however no plane surface on which the stone can be arranged. An example on such machine tools is some machines which comprise a working line, in which a number of line machines are included for performing successive working operations. Each one of the line machines performs one or more working operations on a working piece which is moved along the line machines. The working piece is often fastened to a fixture which is adapted to the working piece. In such machine tools there is no plane surface for a stone. In order to be able to perform a measurement in such machines with a traditional stone it is, thus, necessary to arrange a plane surface for the stone by dismounting the fixture and after the measurement mount the fixture again. This is, however, time consuming measures which one wish to avoid. In order to avoid such time consuming measures another measuring method has had to be used which not requires a plane surface.

Summary of the invention

An object of the present invention is to provide a device and a method to enable measurement of angles in a machine tool using a stone with plane surfaces, even in the case that the machine tool does not have a sufficiently large plane surface to place a stone on in a conventional way.

Another object of the present invention is to provide a method for measurement of angles in a machine tool using a stone having plane surfaces, which machine tool does not have a sufficiently large plane surface to place a stone on in a conventional way.

According to a first aspect of the present invention a measuring device is provided for measurement of angles in a machine tool, wherein the measuring device comprises a stone which has at least to plane surfaces which are arranged in right angle to each other. The measuring device is characterized in what is evident from the characterizing portion of claim 1.

A measuring device according to the invention can be used for measuring angles in a machine tool. After the measurement the machine tool may be adjusted based on the result of the measurement.

By providing a measuring device in which it is possible to angle the stone in relation to the fastening device it is possible to get one of the plane surfaces in right angle to one of the directions of motion of the machine even if there are no plane surface to place an ordinary measuring stone on. This results in a large saving of time as one then does not have to dismount any fixture or similar. Another advantage in addition to the saving of time is that one can measure with the machine tool loaded in the same way as when it is used in the production. If one removes a fixture from the machine tool there is a risk for the geometry of the machine tool to change.

The stone can be of any type of stone having suitable properties with respect to thermal expansion and strength. An example of a suitable type of stone is diabase.

The stone can be possible to angle around two turning axes in relation to the fastening device, which turning axes form an angle with each other. By the stone being possible to angle in this way a larger freedom is provided with respect to the placement of the fastening means on the machine tool. The measuring device may comprise a stone holding device which is arranged fixed in relation to the stone and which is movably connected to the fastening device. By the measuring device comprising a stone holding device the possibility to angle the stone in relation to the fastening device is provided in a more simple way. The stone holding device is of another material than stone, such as for example metal, plastic or any composite material. The stone holding device may be fastened to the stone in a plurality of different ways, such as for example by glue or with mechanical fastening means.

The stone holding device and the fastening device may define a main surface each, wherein the stone holding device and the fastening device are arranged with the main surfaces turned against each other and essentially parallel to each other. In case the stone holding device and the fastening device are arranged in this way it is possible to make the stone holding device and the fastening device compact in size.

The stone holding device and the fastening device may have one of a plurality of different forms. For example, each one of the stone holding device and the fastening device may, essentially have the form of a plate. With such a form they become compact in size.

The main surface of the stone holding device may be parallel with one of the plane surfaces of the stone. By arranging the plane surfaces of the stone in this way best possibilities are provided to angle the stone in the correct way in relation to the machine tool.

Spring means may be arranged to act with a force on the stone holding device and the fastening device against each other. With the spring means the stone holding device and the fastening device can be pressed against each other. In this way a stable construction is provided which gives large freedom with respect to the placement. For example it is possible to arrange such a measuring device with the stone hanging, without the function of the measuring device being lost.

The stone holding device may be connected with the fastening device through a ball joint. By having the stone holding device connected to the fastening device through a ball joint turning around the two turning axes mentioned above are possible with only one connection. Thus, this is a space efficient way of providing possibility for turning around two turning axes.

The measuring device may comprise two distance adjustment means, arranged at a distance from the ball joint, wherein each one of the distance adjustment means is arranged for adjustment of the distance between the stone holding device and the fastening device, and thus also the angle between the stone holding device and the fastening device. With such distance adjustment means and with a ball joint the angle between the stone holding device and the fastening device may be adjusted in a simple way. The distance adjustment means may be of any one of a plurality of different types. The distance adjustment means may, for example, be adjusting screws being threaded in one of the fastening device and the stone holding device and acting against the other one of the fastening device and the stone holding device. The distance adjustment means may be mechanical or be electrically driven. The distance adjustment means may, for example, be piezoelectric effect means.

The fastening device may comprise means for fastening in the machine tool. Such means may for example be holes in the fastening device, by means of which the fastening device may be screwed on the machine tool. As has been mentioned above it is often necessary to be able to linearly move a component in a machine tool. The linear movement may for example be the linear movement of a holder for a work piece in relation to a rotating tool. According to a second aspect of the present invention a method is provided for measurement of the motion of a component in a machine tool, which component can be moved in a first direction and in a second direction. The method is characterized in what is evident from the characterizing part of claim 13.

Such a method is especially useful for controlling that two unconnected motions are parallel to each other and that the two directions, thus, are parallel with each other. Such parallel motions may be found in a machine tool where one of the motions is used for coarse movement of a component and the second motion is used for fine movement of the component.

There also exist a need of being able to measure angles between other axes and directions of motion in machine tools. In, for example, milling cutters it is common that the rotating tool can be moved in a plane perpendicular to the axis of rotation of the tool. According to a third aspect of the present invention a method is provided for measurement of the motion of a component in a machine tool, which component can be moved in a first direction and in a second direction, which form an angle with each other. The method is characterized of what is evident from the characterizing part of claim 14.

The first direction can for example be in the horizontal direction and the second direction can be in the vertical direction.

By component is meant the part which is fixed in relation to a movable part in the machine tool and can be a part of the machine tool or be a component which is used to perform the measurement. With a method according to the third aspect of the present invention it is possible to measure that two directions have a desired angle to each other. Preferably the stone is arranged so that its two plane surfaces have the desired angle to each other.

It is often desirable to be able to move a component in a machine tool in two directions being perpendicular to each other. In such cases the stone is suitably arranged so that the plane surfaces of the stone are perpendicular to each other.

The distance between the stone and the component can be measured mechanically. By measuring the distance mechanically it is not necessary to add any electrical energy to the measuring device. It is of course within the scope of the invention to measure the distance between the stone and the component in another way than mechanically.

In the following preferred embodiments of the invention will be described with reference to the drawings.

Short description of the drawings

Fig. 1 shows schematically a machine tool with a plurality of line machines.

Fig. 2 shows schematically the fixture and one of the line machines in Fig. 1 , wherein a measuring device according to the invention is arranged on the fixture.

Fig. 3 shows schematically the fixture and another one of the line machines in Fig. 1 , wherein a measuring device according to the invention is arranged on the fixture.

Fig. 4 shows in larger detail a part of the measuring device shown in Fig. 2. Fig. 5 shows schematically the fixture and another one of the line machines in Fig. 1 , wherein a measuring device according to the invention is arranged on the fixture.

Fig. 6 shows schematically the fixture and another one of the line machines in Fig. 1 , wherein a measuring device according to the invention is arranged on the fixture.

Description of preferred embodiments

In the following description of preferred embodiments of the invention similar features will be denoted by the same reference numeral in the different figures.

Fig. 1 shows schematically a machine tool 1 comprising a transport rail 2 on which a fixture 3 is arranged. The fixture is arranged for reception of a work piece 4 so that it is held in place in a correct way during working of the work piece 4. The machine tool 1 also comprises a plurality of line machines 5 which each are arranged on a separate machine rail 6 leading to the transport rail 2.

The machine tool 1 is arranged so that the fixture in turn is moved to each one of the line machines 5. When the fixture 3 with the work piece 4 has been moved to a line machine 5, the line machine 5 is moved to the work piece 4 on its machine rail 6 and performs one or more working operations on the working piece 4. The machine tool 1 comprises a working line.

Below the case is described when the machine tool has been provided with a measuring device in order to measure angles in the machine tool. After measuring with the measuring device the machine can be adjusted based on the measurement so that angles in the machine tool become the desired. In Fig. 2 a side view of one of the line machines 5 in Fig. 1 is shown together with the fixture 3 and a measuring device 12 according to an embodiment of the invention. The fixture 3 is arranged on the transport rail 2. The line machine 5 is arranged on a machine rail 6 on which the line machine 5 can be moved in the horizontal direction 39 to or from the fixture 3 which is arranged on the transport rail 2. The line machine 5 comprises a rotary spindle 7 which is arranged for fastening of a working tool such as a milling cutter. The spindle 7 is movable in the vertical direction 40 on a vertical rail 8. During the measurement there is arranged on the spindle 7 a component 9, on which there is arranged a measuring clock 10 being provided with a measuring arm 1 1. A measuring device 12 is arranged on the fixture 3. The measuring device 12 comprises a stone 13 which has a first plane surface 14 and a second plane surface 15, which surfaces are arranged perpendicular to each other. The stone 13 is fastened in a stone holding device 16 which in turn is movably connected with a fastening device 17. The fastening device 17 is, during the measurement, mounted fixed in the fixture 3. The measuring clock 10 is in Fig. 2 arranged with the measuring arm 1 1 against the second plane surface 15. When the line machine 5 is moved along the machine rail 6 the reading on the measuring clock 10 will change if the machine rail 6 is not parallel to the second plane surface 15.

During measurement with the measuring device 12 according to the invention the measuring clock 10 is arranged on the first plane surface 14 of the stone 13 as is shown in Fig. 2. After the measuring clock 10 has been read the line machine 5 is moved along the machine rail 6 and thereafter the measuring clock 10 is read again. The stone holding device 16, and thus the stone 13, is adjusted accordingly so that the stone 13 is re-angled in relation to the fastening device 17 so that the first plane surface 14 becomes parallel with the machine rail 6. This adjustment can be made iteratively wherein the reading of the measuring clock 10 is read after each adjustment of the stone holding device 16 during movement of the line machine 5 along the machine rail 6. After the stone 13 has been adjusted so that its first plane surface 14 is parallel with the machine rail 6 the measuring clock 10 is arranged with its measuring arm 1 1 against the second plane surface 15. Thereafter the change in the reading of the measuring clock 10 is read when the spindle 7 is moved vertically along the vertical rail 8. With knowledge about the change in the reading of the measuring clock 10 and the size of the movement of the spindle 7 along the vertical rail 8 it is possible to calculate the angle between the machine rail 6 and the vertical rail 8.

Fig. 3 shows schematically the fixture 3 and another one of the line machines 5 in Fig. 1 , wherein a measuring device according to the invention is arranged on the fixture 3. I Fig. 3 it is illustrated how the angle of the spindle 7 in relation to the machine rail 6 can be measured in case the spindle 7 is not possible to move vertically. Only the parts which are different in Fig. 3 compared with Fig. 2 will be described. The stone 13 is adjusted so that its first plane surface 14 is parallel with the machine rail 6, in the same way as has been described above in relation to Fig. 2. Thereafter the measuring clock 10 is mounted eccentric on the spindle 7 with the measuring clock arranged against the second plane surface 15 at a known distance from the centre 18 of the spindle 7. The measuring clock 10 is read in a first position for the spindle 7. Thereafter the spindle 7 is turned half a turn to a second position as is indicated with the dotted lines before the measuring clock 10 is read a second time. With knowledge about the change in reading on the measuring clock 10 and the distance between the fastening point of the measuring clock 10 and the centre 18 of the spindle 7 the angle of the spindle 7 in relation to the machine rail 6 may be calculated.

Fig. 4 shows in larger detail a part of the measuring device 12 shown in Fig. 2 and in Fig. 3. In Fig. 4 the measuring device is shown from another angle and in another scale than in Fig. 2 and Fig. 3. In Fig. 4 the stone 13 has another size in relation to the fastening device 17 than in Fig. 2 and Fig. 3. Fig. 4 shows how the measuring device 12 is arranged so that the stone 13 shall be possible to angle in relation to the fastening device 17. The stone 13 is arranged fixed on a stone holding device 16 which has the form of a plate 16 which in turn is movably arranged around a ball joint 20 in relation to the fastening device 17 which also has the form of a plate. The main surface 33 of the fastening device 17 is turned against the main surface 34 of the stone holding device 16. A screw 21 is arranged fixed in the stone holding device 16 and runs through a ball 22 and the fastening device 17. Springs in the form of washers 23 are arranged between the screw 21 and the fastening device 17 so that the fastening device 17 is pressed against the ball 22. A first adjustment means in the form of a first adjusting screw 24 and a second adjusting means in the form of a second adjusting screw 25 are arranged threaded in the fastening device and presses against the stone holding device 16 so that the distance between the stone holding device 16 and the fastening device 17 is changed when one screws on the first adjusting screw 24 or the secoiid adjusting screw 25. Adjacent to the first adjusting screw 24 and the second adjusting screw 25 there is arranged a first spring means 26 and a second spring means 27, respectively. Each one of the spring means 26, 27 comprises a holding up means 28, 29 which is arranged fixed in the stone holding device 16 and which runs through the fastening device 17, and spring washers 30, 31 which are arranged between each one of the holding up means 28, 29 and the fastening device 17. The spring means 25, 26 provides for the stone holding device 16 being pressed against the fastening device 17. When the first adjusting screw 24 is adjusted the fastening device 17 will be turned around a first turning axis 37 which runs through the ball 22 and when the second adjusting screw 25 is adjusted the fastening device will be turned around a second turning axis 38 which runs through the ball 22. During adjustment of the first adjusting screw 24 and the second adjusting screw 25 the distance 41 and thereby also the angle 42 between the stone holding device 16 and the fastening device 17 will change. In the fastening device 17 there is also arranged means for fastening in the machine tool 1. In the shown embodiment these means are designed as threaded holes 32. Even other fastening means are possible, such as for example different types of squeeze means.

Fig. 5 shows schematically the fixture 3 and another one of the line machines 5 in Fig. 1 , wherein a measuring device according to the invention is arranged on the fixture. In Fig. 5 it is illustrated how the angle of the spindle 7 in relation to the machine rail 6 can be measured in the case that the spindle 7 only may be moved horizontally which is the case with the line machine 5 in Fig. 5. Only the parts which are different in Fig. 5 compared with Fig. 2 will be described. The stone 13 has only a first plane surface 14. The line machine 5 is arranged on a sub¬ line machine 36 with a top rail 35. The component 9 may be coarsely moved in the horizontal direction 39 with the machine rail 6 and be moved finely in the horizontal direction 39 with the top rail 35. The stone 13 is adjusted so that its first plane surface 14 is parallel with the machine rail 6 on the same way as has been described above in connection with Fig. 2. After the adjustment the measuring clock 10 is read in a first position for the top rail 35. Thereafter the component 9 is moved using the top rail 35 before the measuring clock 10 is read a second time. With knowledge about the change in reading on the measuring clock 10 and the size of the movement using the top rail 35, the angle between the top rail 35 and the machine rail 6 may be calculated. The above described measurement is often used to assure whether the top rail 35 is parallel with the machine rail 6.

Fig. 6 shows schematically the fixture three and another one of the line machines 5 in Fig. 1 , wherein a measuring device according to the invention is arranged on the fixture. The line machine 5 comprises a vertical rail 8. In Fig. 6 it is illustrated how the angle of the spindle 7 in relation to the vertical rail 8 can be measured. Only the parts which are different in Fig. 6 compared with Fig. 2 and Fig. 3 will be described. The stone 13 has only one plane surface 14 and has an elongated form. The stone 13 is adjusted so that its first plane surface 14 is parallel with the vertical rail 8 in the following way. The measuring clock 10 is arranged on the first plane surface 14 on the stone 13. After the measuring clock 10 has been read the spindle 7 is moved along the vertical rail 8 and thereafter the measuring clock 10 is read again. The stone holding device 16, and thereby the stone 13, is adjusted accordingly so that the stone 13 is re- angled in relation to the fastening device 17 so that the first plane surface 14 becomes parallel with the vertical rail 8. Thereafter the measuring clock 10 is arranged eccentric on the spindle 7 with the measuring clock arranged against the second plane surface 15 at a known distance from the centre 18 of the spindle 7. The measuring clock 10 is read in a first position for the spindle 7. Thereafter the spindle 7 is turned half a turn to a second position, which is indicated with the dotted lines, before the measuring clock 10 is read a second time. With knowledge about the change in reading on the measuring clock 10 and the distance between the fastening position of the measuring clock 10 and the centre 18 of the spindle 7, the angle of the spindle 7 in relation to the vertical rail 8 may be calculated.

The invention is not limited to the above described embodiments which may be varied in many ways without departing from the spirit and scope of the invention which is limited only by the appended claims.

It is, for example, not necessary for the spring means to have the shown design. The spring means 26, 27 may for example be comprised of pulling springs which are fastened in the stone holding device 16 and the fastening device 17.

Claims

1. Measuring device (12) for measurement of angles in a machine tool (1 ), wherein the measuring device (12) comprises a stone (13) which has at least a first plane surface (14), characterized in that it comprises a fastening device (17) which is arranged for fastening of the measuring device (12) in the machine tool (1 ), and by the stone (13) being possible to angle in relation to the fastening device (17).

2. Measuring device (12) according to claim 1 , wherein the stone (13) is possible to angle around two turning axes (37, 38) in relation to the fastening device (17), which turning axes (37, 38) form an angle with each other.

3. Measuring device (12) according to claim 1 or 2, comprising a stone holding device (16) which is arranged fixed in relation to the stone (13) and which is movably connected with the fastening device (17).

4. Measuring device (12) according to claim 3, wherein the stone holding device (16) and the fastening device (17) each defines a main surface (33, 34), and wherein the stone holding device (16) and the fastening device (17) are arranged with the main surfaces (33, 34) turned against each other and essentially in parallel to each other.

5. Measuring device (12) according to claim 4, wherein the main surface (33, 34) of the stone holding device (16) is parallel to one of the at least one plane surface (14) of the stone (13).

6. Measuring device (12) according to claim 4 or 5, wherein the spring means (26, 27) are arranged to act with a force which pulls or pushes the stone holding device (16) and the fastening device (17) against each other.

7. Measuring device (12) according to claim 4 or 5, wherein the stone holding device (16) is connected to the fastening device (17) with a ball joint (20).

8. Measuring device (12) according to claim 7, comprising two adjustment means (24, 25) arranged at a distance from the ball joint (20), wherein each adjustment means (24, 25) is arranged for adjustment of the distance (41 ) between the stone holding device (16) and the fastening device (17), and thereby also the angle (42) between the stone holding device (16) and the fastening device (17).

9. Measuring device (12) according to claim 8, wherein the adjustment means (24, 25) are adjusting screws which are threaded in one of the fastening device (17) and the stone holding device (16), and which act against the other one of the fastening device (17) and the stone holding device (16).

10. Measuring device (12) according to any one of the preceding claims, wherein the fastening device (17) comprises means for mountable fastening in the machine tool (1 ).

1 1 . Measuring device (12) according to any one of the preceding claims, wherein the stone has a second plane surface (15).

12. Measuring device (12) according to claim 1 1 , wherein the second plane surface (15) is arranged perpendicularly to the first plane surface (14).

13. Method for measurement of the motion of a component in a machine tool (1 ), which component (9) may be moved in a first direction and in a second direction, characterized in that it comprises the steps of: arranging a stone (13) on the machine tool (1 ), which stone at least has a first plane surface (14), moving the component (9) in the first direction and measuring the change in distance between the first plane surface (14) on the stone (13) and the component (9), angle the stone (13) so that the first surface (14) is parallel with the first direction, and moving the component (9) in the second direction and measuring the change in distance between the component (9) and the first surface (15) of the stone (13).

14. Method for measurement of the motion of a component in a machine tool (1 ), which component (9) can be moved in a first direction and in a second direction which form an angle against each other, characterized in that it comprises the steps of: arranging a stone (13) on the machine tool (1 ), which stone has a first plane surface (14) and a second plane surface (15), wherein the surfaces (14, 15) forms an angle against each other, moving the component in the first direction and measuring the change in distance between the first surface (14) of the stone (13) and the component (9), angle the stone (13) so that the first surface (14) is parallel with the first direction, and measuring the distance between the component (9) and the second surface (15) of the stone (13) when the component (9) is moved in a second direction.

15. Method according to claim 14, wherein the distance between the stone (13) and the component (9) is measured mechanically.

16. Method according to claim 14 or 15, wherein the first plane surface (14) is perpendicular to the second plane surface (15).