Device and method for grinding workpieces using a control unit

Abstract

A system for grinding solid workpieces includes a grinding wheel, a bearing for rotatable mounting of the grinding wheel about an axis of rotation, and a grinding wheel drive for rotating the grinding wheel. The system allows the production of freely-definable surfaces on the face of the rigid workpiece that comes into contact with the grinding wheel. The bearing is fastened to a pivotable and displaceable bearing carrier. The bearing plane is pivotable in any desired direction with respect to an initial plane and is displaceable in a direction perpendicular to the initial plane. Actuators are coupled to the bearing carrier to pivot and displace the bearing carrier. A digital control unit controls and synchronizes the actuators such that the surface of the grinding wheel creates a freely-definable face about a positionally fixed reference point which is at a radial distance from the center point of the grinding wheel.

Claims

1. A device for grinding solid workpieces, comprising: a grinding wheel; a bearing for the rotatable mounting of the grinding wheel about an axis of rotation; a grinding wheel drive, which is coupled to the grinding wheel, for rotating the grinding wheel, wherein the bearing is fastened to a pivotable and displaceable bearing carrier, wherein the bearing plane of the bearing is pivotable in any desired directions with respect to an initial plane and is displaceable in an initial direction perpendicular to the initial plane; actuators coupled to the bearing carrier in order to pivot and displace the bearing carrier; and a digital control unit that controls and synchronizes the actuators such that the surface of the grinding wheel creates a freely-definable face about a positionally fixed reference point which is at a radial distance from the center point of the grinding wheel.

2. The device according to claim 1, wherein the freely-definable face is rotationally symmetrical.

3. The device according to claim 1, further comprising: a pivot joint which carries the bearing carrier in a freely-pivotable manner.

4. The device according to claim 3, wherein the pivot joint is a ball joint.

5. The device according to claim 3, wherein the pivot joint is a universal joint having two intersecting pivot axes.

6. The device according to claim 3, wherein the actuators include the following: a first inclination adjustment drive for pivoting the bearing about a first pivot axis of the pivot joint; a second inclination adjustment drive for pivoting the bearing about a second pivot axis, which intersects the first pivot axis, of the pivot joint; and a linearly-acting drive for displacing the bearing carrier.

7. The device according to claim 1, wherein the bearing carrier includes three fastening elements which are arranged at a distance from one another and to each of which an actuating rod, which is moved by at least one of the actuators, is fastened.

8. The device according to claim 7, wherein, in the case of a bearing plane extending parallel to the initial plane, each of the actuating elements is displaceable parallel to the initial direction using at least one of the actuators, by the actuating rod fastened thereto.

9. The device according to claim 1, wherein the grinding wheel drive is a hub motor, the rotor of which is connected to the grinding wheel in a torque-proof manner.

10. A method for grinding solid workpieces, in which a grinding wheel is mounted by a bearing so as to be rotatable about an axis of rotation and is driven by a grinding wheel drive, the method comprising: fastening the bearing to a pivotable and displaceable bearing carrier, wherein the bearing plane of the bearing is pivotable in any desired directions with respect to an initial plane and is displaceable in an initial direction perpendicular to the initial plane, pivoting or displacing the bearing carrier using actuators; and controlling and synchronizing the actuators using a digital control unit such that the surface of the grinding wheel creates a freely-definable face about a positionally fixed reference point which is at a radial distance from the center point of the grinding wheel.

11. The method according to claim 10, wherein the freely-definable face is rotationally symmetrical.

12. The method according to claim 10, wherein the bearing carrier is held in a pivotable manner using a pivot joint.

13. The method according to claim 10, wherein the actuators include two inclination adjustment drives and a linearly acting drive, wherein the first inclination adjustment drive pivots the bearing about a first pivot axis of the pivot joint, wherein the second inclination adjustment drive pivots the bearing about a second pivot axis, which intersects the first pivot axis, of the pivot joint, and wherein the linearly acting drive displaces the bearing carrier.

14. The method according to claim 10, wherein the bearing carrier has three fastening elements which are arranged at a distance from one another and to each of which an actuating rod, which is actuated by at least one of the actuators, is fastened.

15. The method according to claim 14, wherein each of the fastening elements is displaced parallel to the initial direction by the actuating rod fastened thereto, using at least one of the actuators, when the bearing plane extends parallel to the initial plane.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the system described herein are explained in the following text with reference to the appended drawings.

(2) FIGS. 1 to 4 show a perspective illustration and three sectional illustrations of the grinding wheel and of a workpiece of the grinding device described here.

(3) FIG. 5 shows a side view of a first embodiment of the grinding device described here.

(4) FIG. 6 shows a sectional view of the grinding device from FIG. 5 along the section line VI-VI.

(5) FIG. 7 shows a plan view and FIG. 8 shows an illustration in section along section line VIII-VIII of the grinding device from FIG. 5.

(6) FIG. 9 shows a side view of a second embodiment of the grinding device described here.

(7) FIG. 10 shows an illustration in section along section line X-X of the grinding device from FIG. 9.

(8) FIG. 11 shows a plan view and FIG. 12 shows an illustration in section along section line XII-XII of the grinding device from FIG. 9.

(9) FIG. 13 shows a further embodiment of the grinding device described here.

(10) FIG. 14 shows an illustration in section along section line XIV-XIV of the grinding device from FIG. 13.

(11) FIG. 15 shows a plan view and FIG. 16 an illustration in section along section line XVI-XVI of the grinding device from FIG. 13.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

(12) FIGS. 1 to 4 illustrate the grinding that is desired with the grinding device described here. The grinding wheel 1 and the workpiece 2 are depicted here. The grinding wheel 1 is configured in a flat manner, i.e. it has two mutually parallel grinding surfaces. In the illustration shown, the workpiece 2 is a copper welding electrode. The welding electrode 2 is drawn in an exposed manner. In practice, it is moved to the grinding wheel 1 by welding tongs fastened to a robot arm. The grinding wheel 1 may include an elastic, optionally foamed plastics material, to the disk-like top side and underside of which abrasives have been applied. However, rigid grinding wheels 1 are also used. The grinding wheel 1 is fixedly screwed to a hub 3 which is pivotable and displaceable in the present grinding device.

(13) The axis of rotation of the bearing of the grinding wheel is provided with the reference number 4 in FIGS. 2 to 4. The bearing itself is not illustrated.

(14) The vertical direction in which the grinding wheel 1 is displaceable is provided with the reference number 5 in FIGS. 2 to 4. The vertical direction 5 in FIGS. 2 to 4 corresponds to the initial direction. It should be noted that the initial direction can be selected to be in any desired position. The workpiece 2 is then intended to be moved in a corresponding position onto the grinding face of the grinding wheel 1. The relative position of the components of the grinding device is pivoted in a corresponding manner when the initial direction 5 is pivoted.

(15) It can be gathered in particular from FIGS. 2 and 3 that, in order to create a rotationally symmetrical, spherical surface on the workpiece 2, the axis of rotation of the mounting of the grinding wheel 1 is pivotable with respect to the vertical initial direction 5. In this case, the axis of rotation 4 is pivotable not only in the plane drawn in FIGS. 2, 3 and 4, but also perpendicularly thereto and in any desired other directions. The grinding wheel 1 is held such that the axis of rotation 4 is freely pivotable within a conical adjustment region about the initial direction 5. At the same time, the grinding wheel 1 is displaceable in the vertical initial direction 5. The pivoting movements and displacement movements are synchronized such that the grinding wheel 1 is in contact with the surface of the workpiece 2 in the vicinity of a reference point 6. On account of the pivotability of the grinding wheel 1, the grinding wheel 1 can produce a spherical or conical surface on the end side of the workpiece 2. During the machining operation, the workpiece 2 remains in a fixed position with respect to the machine frame of the grinding device, and so the reference point 6 is in a fixed position.

(16) The reference point 6 is at a radial distance from the center point of the grinding wheel 1. On account of this radial distance, a shift of the reference point 6 in the initial direction 5, which is compensated by a shift in the mounting of the grinding wheel 1, results from the pivoting of the grinding wheel 1. The displacement movement and pivoting movement of the grinding wheel 1 are synchronized with one another such that the surface of the grinding wheel 1 is always in contact with the workpiece 2 in the vicinity of the reference point 6. This permits generating a wobbling movement of the grinding wheel 1, which produces a conical surface or a surface in the form of a spherical cap on the end side of the workpiece 2 in the region of the reference point 6.

(17) The surface of the workpiece 2 does not have to be ground in a rotationally symmetrical manner. As a result of the free pivoting and displacement of the grinding wheel 1, any desired shapes of the end side of the workpiece 2 can be realized in the pivoting range and displacement range of the grinding wheel 1.

(18) FIGS. 5 to 8 show a first embodiment of the pivoting and displacement drives for the grinding wheel 1.

(19) A first stepper motor 7 is connected to a threaded spindle 9 via a metal bellows coupling 8. On the threaded spindle 9 there runs a spindle nut 10 which is moved up and down when the threaded spindle 9 rotates. The stepper motor 7 and threaded spindle 9 are fastened to a positionally fixed machine frame (not illustrated). The first stepper motor 7 effects displacement in the vertical initial direction 5. Fastened to the spindle nut 10 is a support plate 11 which carries the pivot drives. If the friction of the threaded spindle 9 is intended to be minimized, the latter can be configured as a ball screw having a ball nut as spindle nut 10. Alternatively, it is possible to use a self-locking trapezoidal spindle such that the weight forces of the device cannot cause any malpositioning of the threaded spindle 9. The same goes for the threaded spindles described below. The metal bellows coupling 8 compensates an axial offset or angular offset between the motor shaft and the threaded spindle 9.

(20) Two further stepper motors 12, 13 are flanged on the underside of the support plate 11. Each of these stepper motors 12, 13 is connected via a respective metal bellows coupling 14, 15 to in each case one further threaded spindle 16, 17. The stepper motor 12 drives the rotary movement of the threaded spindle 16 via the metal bellows coupling 14, such that the spindle nut 18 is moved up or down in the vertical direction. The stepper motor 13 drives the threaded spindle 17 via the metal bellows coupling 15 in order to displace the spindle nut 19. Each of the two spindle nuts 18, 19 is connected to a bearing carrier via an actuating rod 20, 21. An external joint ring 32 of a universal joint 28 forms the bearing carrier in the embodiment in FIGS. 5 to 8. The bearing carrier 32 carries a bearing 22 for the rotor 23 of a hub motor which drives the grinding wheel 1. Further components of the hub motor are not illustrated for reasons of clarity. The rotor 23 is connected to the hub 3 of the grinding wheel 1 in a torque-proof manner. The bearing 22 is illustrated here as a simple ball bearing. However, any suitable bearing, in particular a roller bearing, can be used.

(21) The bearing carrier 32 can be pivoted in any desired directions with respect to a horizontally extending initial plane via the universal joint 28 described in more detail in the following text.

(22) All of the stepper motors 7, 12, 13 are connected to a control unit 27 via control lines 24, 25, 26. The control unit 27 is illustrated only in FIG. 5 and not in FIGS. 6 to 8. It can be formed by any suitable data processing device. In practice, a programmable logic controller (PLC) or a microcontroller is usually used in order to control the stepper motors 7, 12, 13. The stepper motors 7, 12, 13 can be controlled such that, via the control unit 27, in each case a precise predetermined position of the spindle nut 10, 18 and 19 can be set. The same result can also be achieved with servomotors.

(23) It can be seen in particular in FIG. 8 that the bearing carrier 32 in this embodiment is pivotable in any desired directions out of the horizontal plane by the universal joint 28. The universal joint 28 is arranged at the upper end of a holding rod 29, the lower end of which is fastened to the support plate 1. The universal joint 28 has an internal joint ring 30 which is fastened to the holding rod 29 so as to be pivotable about an internal axle pin 31. A second external joint ring 32 is pivotable about two external axle pins 33, 34. The two external axle pins 33, 34 extend at right angles to the internal axle pin 31. The actuating rod 20 pivots the external joint ring 32. The actuating rod 21 pivots the internal joint ring 30.

(24) The actuating rods 20, 21 have at both of their ends ball joints by way of which they are coupled on one side to the spindle nuts 18, 19 and on the other side to the joint rings 30, 32 of the universal joint 28. As a result, the pivoting movements are compensated when the joint rings 30, 32 are actuated.

(25) As mentioned, the external joint ring 32 serves as a bearing carrier for the bearing 22 (FIG. 6) of the grinding wheel 1. It can be seen that by using the universal joint 28 any desired pivoting of the bearing plane for the grinding wheel 1 and thus the main plane of the grinding wheel 1 itself out of the horizontal initial plane can be realized. The displacement of the grinding wheel 1 takes place by raising and lowering the support plate 1 using the threaded spindle 9 driven by the stepper motor 7. The actuating movements of the three actuators effect predictable shifts of the grinding wheel 1 such that, by using the digital control unit 27, the pivoting and displacement of the grinding wheel 1 can be controlled in such a way that, during the machining of a workpiece 2 which bears against the grinding wheel 1 in the region of the reference point 6, the desired contact between the surface of the workpiece 2 and the surface of the grinding wheel 1 can be achieved at any time. In this case, it is of course also possible for the workpiece 2 to be pressed against the grinding wheel 1 from below, unlike in the drawings.

(26) With respect to the drawings described here, the terms up and down result from the selected position of the initial direction 5, which extends vertically in the drawings. This results in a horizontally extending initial plane, about which the grinding wheel 1 is freely pivotable. The initial direction can extend in any desired direction in space, wherein the initial plane and the components of the described device shift in a corresponding manner.

(27) FIGS. 9 to 12 show an alternative embodiment of the grinding device. Identical components are provided with the same reference numbers in these figures as in FIGS. 5 to 8.

(28) The essential difference here is that a ball joint 33 is fastened to the upper end of the holding rod 29. To be more precise, a ball 34 which carries a support ring 35 is fastened to the holding rod 29. The support ring 35 has an internal spherical bearing shell which is carried by the ball 34 so as to be pivotable about the horizontal plane. The support ring 35 forms the bearing carrier in this embodiment, wherein, here too, the bearing 22 for the grinding wheel 1 is a ball bearing.

(29) In order to pivot the bearing carrier 35, the latter is connected to the actuating rods 20, 21 via connecting pins 36, 37. Unlike the universal joint 28 in FIG. 8, the ball joint 33 in FIGS. 9 to 12 cannot introduce any torques into the holding rod 29. For this reason, a cylindrical pin 38 is fitted on the bearing carrier 35 as a torque support 38. The pin 38 is held so as to be displaceable in a slot in a guide bracket 39. The guide bracket 39 is fastened to the holding rod 29, which is connected to the support plate 11 in a torque-proof manner. The pin 38 and the guide bracket 39 prevent the bearing carrier 35 from twisting on the ball 34 on account of torques that act on the grinding wheel 1.

(30) Otherwise, this embodiment, too, allows the grinding wheel 1 to be displaced using the stepper motor 7, which raises and lowers the support plate in the vertical initial direction 5, and allows the grinding wheel 1 to be pivoted using the stepper motors 12, 13, which pivot the bearing carrier 35 in the form of a support ring.

(31) The bearing carriers, i.e. both the external joint ring 32 of the universal joint 28 of the first embodiment (see in particular FIGS. 6 and 8) and the support ring 35 which is articulated in a pivotable manner on the ball 34 (FIGS. 10 and 12) are moved in the manner of a swash plate. They pivot about the horizontal plane and can be shifted in the vertical direction.

(32) FIGS. 13 to 16 show an alternative embodiment in which the drive of the bearing carrier 40 is configured in a similar manner to the drive for a swash plate known from helicopter construction. In the embodiment in FIGS. 13 to 16, too, identical components are provided with the same reference numbers as in FIGS. 5 to 8.

(33) In this embodiment, too, the bearing carrier 40 is mounted in a pivotable manner on a ball 41. The ball 41 is arranged at the upper end of a guide rod 42 which is mounted so as to be displaceable in the vertical direction with respect to a mounting plate 43. Three stepper motors 44, 45, 46 are fastened to the mounting plate 43 and are connected to three threaded spindles 50, 51, 52 via three metal bellows couplings 47, 48, 49. The metal bellows couplings 47-49 and the threaded spindles 50-51 are also fixedly arranged on the mounting plate 43. The threaded spindles 50-53 are each connected to the bearing carrier 40 via an actuating rod 53-55. The bearing carrier 40 has three fastening elements 56, 57, 58 which consist of spherical heads firmly screwed to the bearing carrier 40. The fastening elements 56, 57, 58 are connected to the actuating rods 53, 54, 55.

(34) The bearing carrier 40 has the form of a support ring which is fastened to the ball 41 in a pivotable manner and to which a ring of the bearing 22 for the grinding wheel 1 is fastened. The fastening elements 56-58 fastened to the bearing carrier 40 are each arranged at an angular spacing of 120 around the circumference of the annular bearing carrier 40. If all the fastening elements 56, 57, 58 are raised or lowered synchronously, the bearing carrier 40 is shifted in the vertical direction without pivoting. If only one of the fastening elements 56, 57, 58 is actuated by the associated stepper motor 44, 45, 46, then the bearing carrier 40 pivots. The pivoted position and position of the bearing carrier 40 are unambiguously assigned to the positions of the three spindle nuts 59, 60, 61 on the threaded spindles 50, 51, 52. In the embodiment in FIGS. 13 to 16, too, the digital control unit 27 can effect any desired pivoted positions and displacements of the bearing carrier 40 by actuating the stepper motors 44, 45, 46, such that the grinding wheel 1 can be positioned by synchronous activation of the stepper motors such that a predetermined face, in particular a rotationally symmetrical surface, e.g. a conical surface or a surface in the form of a spherical cap, is produced around the reference point 6 on the end face of the workpiece 2.

(35) In the case of the bearing carrier 40 in the form of a swash plate, it may likewise be necessary to pick up torque because this cannot be received via the ball 41. For this purpose, too, a pin 38 is fastened to the bearing carrier 40 which is guided in the slot of a guide bracket 39. The guide bracket 39 is fastened to the guide rod 42. In order that the guide rod 42 is held in a torque-proof manner with respect to the mounting plate 43, a linear bearing 62, which holds the guide rod 42 in a displaceable manner, is fastened to the mounting plate 43. The guide rod is tubular and has in its lower region a slot 64 in which a fixing pin 63 engages. Consequently, the torques of the bearing carrier 40 can be introduced into the guide bracket 39 via the pin 38 and are supported from here via the guide rod 42 and the fixing pin of the linear bearing with respect to the mounting plate 43.

(36) The drive variants described here for the bearing carrier 40 by using stepper motors, metal bellows coupling and threaded spindle are illustrated schematically and described only by way of example. A multiplicity of other drive and coupling devices for transmitting the movement to the bearing carrier 40 are conceivable. What is essential is the displaceability of the bearing carrier 40 in an initial direction and the free pivotability of the bearing carrier 40 with respect to the initial plane, which extends perpendicularly to the initial direction.

(37) Various embodiments discussed herein may be combined with each other in appropriate combinations in connection with the system described herein. Additionally, in some instances, the order of steps in the flow diagrams, flowcharts and/or described flow processing may be modified, where appropriate. Further, various aspects of the system described herein may be implemented using hardware, software, a combination of hardware and software and/or other computer-implemented modules or devices having the described features and performing the described functions. The system may further include a display and/or other computer components for providing a suitable interface with a user and/or with other computers.

(38) Software implementations of aspects of the system described herein may include executable code that is stored in a computer-readable medium and executed by one or more processors. The computer-readable medium may include volatile memory and/or non-volatile memory, and may include, for example, a computer hard drive, ROM, RAM, flash memory, portable computer storage media such as a CD-ROM, a DVD-ROM, an SD card, a flash drive or other drive with, for example, a universal serial bus (USB) interface, and/or any other appropriate tangible or non-transitory computer-readable medium or computer memory on which executable code may be stored and executed by a processor. The system described herein may be used in connection with any appropriate operating system.

(39) Other embodiments of the invention will be apparent to those skilled in the art from a consideration of the specification or practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims.