Method and device for the surface finishing of workpieces

Abstract

A method for the surface finishing of workpieces moves the workpiece, including rotating about at least one axis, relative to a bed of a granular grinding and/or polishing material. The workpiece is accelerated to different speeds of rotation in relation to the bed of the granular grinding/polishing material. The workpiece or a container containing the bed of granular grinding/polishing material to be accelerated in periodic cycles of at most 5 sec between speeds of rotation and a second speed of rotation and/or to be rotated during continual acceleration at continually different speeds of rotation. A device for carrying out the method, such as a drag- or dip-finishing machine, includes a control device to impose speed of rotation profiles of the aforementioned type on a rotary drive workpiece holders, on which the workpieces can be clamped, or on a container containing the bed of granular material during the operation.

Claims

1. A method for the surface finishing of workpieces by the workpiece being moved relative to a bed of a granular grinding and/or polishing material, the method comprising the steps of: detachably fastening the workpiece on a workpiece holder; dipping the workpiece into the bed of granular grinding and/or polishing material being charged into a container; rotating the workpiece holder with the workpiece about at least one axis in relation to the bed of granular grinding and/or polishing material; and accelerating and decelerating the workpiece holder with the workpiece to different speeds of rotation in relation to the bed of granular grinding and/or polishing material via a rotary drive of the workpiece holder, wherein the workpiece holder with the workpiece is rotated with continual acceleration and deceleration with continually different speeds of rotation by a program-based control device configured for controlling the rotary drive of the workpiece holder, wherein the workpiece holder with the workpiece is rotated in periodic cycles of at most 5 seconds between at least one first speed of rotation and at least one second speed of rotation, wherein at least one of the periodic cycles is defined as consecutive durations during the surface finishing, during which the workpiece holder with the workpiece is moved once between the at least one first speed of rotation and the at least one second speed of rotation.

2. A method in accordance with claim 1, wherein the workpiece holder with the workpiece is accelerated and decelerated between at least one first speed of rotation essentially equal to zero and at least one second speed of rotation not equal to zero.

3. A method in accordance with claim 1, wherein the workpiece holder with the workpiece is accelerated and decelerated between at least one first speed of rotation not equal to zero and at least one second speed of rotation with a direction of rotation opposite that of the first speed of rotation.

4. A method in accordance with claim 1, wherein the workpiece holder with the workpiece is accelerated to at least one speed of rotation of at least 200 rpm.

5. A method in accordance with claim 1, wherein the workpiece holder with the workpiece is accelerated and decelerated at a speed of rotation based on an essentially sinusoidal curve over time, wherein the period or the cycle of the essentially sinusoidal curve of the speed of rotation equals at most 5 seconds.

6. A method in accordance with claim 5, wherein the workpiece holder with the workpiece is accelerated and decelerated at a speed of rotation based on an essentially sinusoidal curve over time with an approximately constant amplitude.

7. A method in accordance with claim 5, wherein the workpiece holder with the workpiece is accelerated and decelerated at a speed of rotation based on an essentially sinusoidal curve over time with an amplitude that is variable over time.

8. A method in accordance with claim 7, wherein the amplitude of the essentially sinusoidal curve describing the speed of rotation over time decreases or increases.

9. A method in accordance with claim 1, wherein at least one cavity or at least one depression of the workpiece is filled with the bed of the granular grinding and/or polishing material when the workpiece is dipped into the bed of granular grinding and/or polishing material and the workpiece holder with the workpiece is accelerated and decelerated at least about one axis of the cavity or of the depression of the workpiece with continual acceleration and deceleration at continually different speeds of rotation, in order to grind and/or polish at least a wall of the workpiece enclosing the cavity or the depression.

10. A method in accordance with claim 9, wherein the workpiece is accelerated and decelerated about the at least one axis of the cavity or of the depression of the workpiece in the periodic cycles of at most 5 seconds between at least one first speed of rotation and at least one second speed of rotation.

11. A method in accordance with claim 1, wherein the container containing the bed of granular grinding and/or polishing material is rotated with continual acceleration and deceleration with continually different speeds of rotation.

12. A method in accordance with claim 1, wherein the container is at least one of: held stationary; moved by a translatory motion; moved by a translatory motion along a trajectory, especially along a circular path; and rotated rotatorily about its central axis.

13. A method in accordance with claim 1, wherein the container is rotated at least rotatorily about its central axis.

14. A method in accordance with claim 13, wherein the container is rotated about its central axis at a speed of rotation that is essentially constant or changes over time.

15. A method in accordance with claim 1, wherein the workpiece holder with the workpiece is moved, furthermore, by a translatory motion, along a trajectory, relative to the bed of the granular grinding and/or polishing material.

16. A method in accordance with claim 1, wherein at least the rotary motion of the workpiece holder is carried out in a controlled programmed-based manner.

17. A method in accordance with claim 16, wherein the rotary motion of the container containing the bed of granular material is carried out in a controlled programmed-based manner.

18. A method in accordance with claim 1, further comprising: providing a carriage comprising a container rotary drive configured to actuate the container, the carriage comprising carriage centering devices; providing a frame comprising frame centering devices; inserting the carriage in the frame such that the frame centering device cooperate with the carriage centering device to center the carriage relative to the frame.

19. A method for the surface finishing of workpieces, the method comprising the steps of: providing a workpiece holder comprising a rotary drive; providing a container comprising a bed of granular grinding and/or polishing material; detachably fastening a workpiece on the workpiece holder; moving the workpiece into the container; continuously changing a rotational speed of the workpiece with the workpiece holder connected thereto via the rotary drive from a start of a grinding and/or polishing process to an end of the grinding and/or polishing process after the workpiece is moved into the container, wherein the workpiece holder with the workpiece is rotated in periodic cycles of at most 5 seconds between at least one first speed of rotation and at least one second speed of rotation, wherein at least one of the periodic cycles is defined as consecutive durations during the surface finishing, during which the workpiece holder with the workpiece is accelerated and decelerated once while rotating the workpiece holder with the workpiece between the at least one first speed of rotation and the at least one second speed of rotation.

20. A method in accordance with claim 19, wherein continuously changing the rotational speed of the workpiece includes accelerating and decelerating the workpiece holder with the workpiece to different speeds of rotation in relation to the bed of granular grinding and/or polishing material via the rotary drive, wherein the workpiece holder with the workpiece is rotated with continual acceleration and deceleration with continually different speeds of rotation via a program-based control device configured for controlling the rotary drive of the workpiece holder.

21. A method in accordance with claim 19, further comprising: providing a carriage comprising a container rotary drive configured to actuate the container, the carriage comprising carriage centering devices; providing a frame comprising frame centering devices; inserting the carriage in the frame such that the frame centering device cooperate with the carriage centering device to center the carriage relative to the frame.

22. A method for the surface finishing of workpieces, the method comprising the steps of: providing a workpiece holder comprising a rotary drive; providing a container comprising a bed of granular grinding and/or polishing material; detachably fastening a workpiece on the workpiece holder; moving the workpiece into the container for carrying out a granular grinding and/or polishing process; rotating the workpiece holder with the workpiece at a rotational speed after the workpiece is moved into the container from a start of the granular grinding and/or polishing process to an end of the granular grinding and/or polishing process, wherein the rotational speed is continually varied from the start of the granular grinding and/or polishing process to the end of the granular grinding and/or polishing process, wherein the workpiece holder with the workpiece is rotated in periodic cycles of at most 5 seconds between at least one first speed of rotation and at least one second speed of rotation, wherein at least one of the periodic cycles is defined as consecutive durations during the surface finishing, during which the workpiece holder with the workpiece is accelerated and decelerated once while rotating the workpiece holder with the workpiece between the at least one first speed of rotation and the at least one second speed of rotation.

23. A method in accordance with claim 22, wherein continually varying the rotational speed of the workpiece includes accelerating and decelerating the workpiece holder with the workpiece to different speeds of rotation in relation to the bed of granular grinding and/or polishing material via the rotary drive, wherein the workpiece holder with the workpiece is rotated with continual acceleration and deceleration with continually different speeds of rotation via a program-based control device configured for controlling the rotary drive of the workpiece holder.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1 is a schematic perspective view of an embodiment of a device according to the present invention for the surface finishing of workpieces in the form of a drag- or dip-finishing machine;

(3) FIG. 2 is a schematic perspective exploded view of another embodiment of a device according to the present invention for the surface finishing of workpieces;

(4) FIG. 3 is a diagram of an exemplary embodiment of an advantageous speed of rotation profile of a workpiece holder with a workpiece clamped thereon over time that can be set by the control during the operation of the devices according to FIGS. 1 and/or 2; and

(5) FIG. 4 is a diagram of an exemplary embodiment of another advantageous speed of rotation profile, which diagram corresponds to FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(6) The exemplary embodiment of a device for the surface finishing of workpieces in the form of a drag- or dip-finishing machine, which is shown in FIG. 1, has a frame 1, at the upper end of which a part 3 rotatable to and fro about a vertical axis 2 in the direction of arrow P.sub.1 in the form of a rotatable carrying plate in the manner of a plate, is mounted. The rotatable part 3 is equipped for this with a controllable motor drive 4, which is likewise fixed to the frame 1. Lifting device 5 are arranged on the underside of the rotatable part 3 eccentrically to the axis of rotation 2 of said part and in the circumferential direction of said part one after another at equal distances from one another as well as at equal radial distance from the axis of rotation 2 of the rotatable part 3, with three such lifting devices 5 being provided in the present exemplary embodiment, but it is also possible, of course, to provide only two or more than three lifting devices 5. The lifting devices 5 carry a workpiece holder 6 each, which may be provided, for example, with one clamping device 7 or with a plurality of clamping devices 7 each in order to be able to detachably clamp the workpieces to be finished (not shown) on the occasion of their surface finishing. The drive 4 of the rotatable part 3 can be used in this manner as a translatory motion drive of the workpiece holders 6, which are arranged eccentrically at the rotatable part 3 and which are moved along a circular path during a rotation of the part 3.

(7) Each lifting device 5 comprises in the present exemplary embodiment, e.g., a carrying unit 9, which can be displaced to and fro along a vertical guide 8 and which can be moved upward and downward, for example, by means of a chain or belt drive. Furthermore, the lifting devices 5 can be moved in the present exemplary embodiment upward and downward independently from one another individually and independently from the other lifting devices 5 by means of a motor (not recognizable in the drawings) likewise fastened on the underside of the rotatable part 3. Each of the workpiece holders 6 is fixed on the vertically displaceable carrying unit 9, and the workpiece holders 6 can be set into rotation by means of a controllable rotary drive 10 each in order to set a workpiece, which is clamped on the workpiece holder 6, e.g., by means of the clamping device 7, into rotation on the occasion of the surface finishing thereof (arrow P.sub.4).

(8) A container for receiving a granular grinding and/or polishing material (not shown), which can be rotated by means of a rotary motion drive about a vertical axis, is arranged under the lifting device 5 equipped with the workpiece holders 6, the axis of rotation of the container 11 being aligned here, e.g., with the axis of rotation 2 of the rotatable part 3, so that the relative motion caused by this between the workpiece fixed at the workpiece holders 6 and the bed of granular material contained in the container 11 is the same. Each lifting device 5 is capable of displacing the workpiece holder 6 fastened to its carrying unit 9 vertically to and fro along the arrow P.sub.2 between an upper position, which is arranged above the container 11 and in which finished workpieces can be removed from the clamping device 7 of the respective workpiece holder 6 and this clamping device can be fitted with raw workpieces, and a lower position, in which the workpieces 17 clamped on the clamping device 7 of the workpiece holders 7 dip into the container 11 in order to enable these workpiece to be finished.

(9) In addition, the rotatable part 3 can be moved in the direction of arrow P.sub.1 about its axis 3 such that it is capable of moving each workpiece holder 6 with a particular workpiece fastened thereto one after another into a fitting/removal position, wherein such a fitting/removal position is assumed, for example, by the workpiece holder 6 shown on the right side in FIG. 1, in which position the workpiece holder 6 is freely accessible from the side after it has been moved by the lifting device 5 into its upper position.

(10) As is also shown in FIG. 1, the workpiece holders 6 with their clamping devices 7 may be sloped at a finite angle in relation to the vertical direction, and this angle equals, e.g., approximately 30 in this case. This has proved in many cases to be advantageous concerning a uniform and effective surface finishing. The slope angle of the workpiece holders 6 may be individually adjustable by, e.g., the carrying unit 9 of each lifting device 5, which said carrying unit carries the particular workpiece holder 6, being pivotable about an axis, which is approximately horizontal here. It is usually advantageous in this connection if the workpiece holders 6 have a slope direction component arranged opposite the direction of rotation of the container 11 (arrow P.sub.3), i.e., the workpieces fixed on the workpiece holders 6 dip into the bed of granular material present here with a slope opposite the direction of rotation of the container 11, so that a surface finishing of the lower end face of the workpieces can take place as well.

(11) As can, furthermore, be determined from FIG. 1, the container 11 containing the granular grinding and/or polishing material may be arranged on a carriage 13 displaceable by means of rollers 12 in this exemplary embodiment in order to ensure a simple and rapid replacement of the granular material by replacing a container 11 with another container. The carriage 13 comprises the rotary drive of the container 11 arranged, e.g., on its underside (not visible in FIG. 1). To ensure accurate alignment of the container 11 in relation to the device being carried by the frame 1, both the carriage 13 and the frame 1 may be equipped with mutually complementary centering devices 16, which are arranged, for example, on three of four sides of the carriage 13 and of the frame 1 and ensure self-centering of the carriage 13 in relation to the frame 1 when the carriage 13 is pushed laterally into the frame 1. so that the axis of rotation of the container 11 coincides with the axis of rotation 2 of the rotatable part 3.

(12) The device comprises, furthermore, a program-based control device (not shown in the drawing), which may be, for example, an electronic data processing unit with a processor and which is capable of controlling the rotary drives 10 of the workpiece holders 6 such that it accelerates the latter during the operation in periodic cycles Z of at most 5 sec to and fro between at least one first speed of rotation R.sub.1 and at least one second speed of rotation R.sub.2 and/or rotates them with continual acceleration at continually different speeds of rotation, wherein the corresponding, desired rotary motion profiles can be advantageously programmed and entered into an input unit (likewise not shown in the drawing) of the control device. Moreover, provisions may, e.g., also be made for the control device to be capable of controlling the control device of the rotary drive of the container 11 in such a manner that it accelerates the latter to and fro during the operation in periodic cycles Z of at most 5 sec between at least one first speed of rotation R.sub.1 and at least one second speed of rotation R.sub.2 and/or rotates same with continual acceleration at continually different speeds of rotation, wherein the desired rotation profiles can thus also be advantageously programmed and entered into the input unit of the control device. Exemplary rotary motion profiles will be explained below as examples with reference to FIGS. 3 and 4. The control device is capable, furthermore, of controlling the rotary motion drive of the container 11 such as to impose on it a more or less desired, more or less constant speed (or speeds) of rotation and/or direction (or directions) of rotation.

(13) Moreover, the control device is functionally connected to both the drive 4 of the rotatable part 3 and the drives of the lifting device 5, and, for example, the desired finishing times of the workpieces as well as the fitting/removal position including the residence time of each workpiece holder 6 in the fitting/removal position can be entered in the input unit of the control device. The control device may be designed such that it displaces the rotatable part 3 in periodic time intervals in order to transfer each workpiece holder 6 after the particular preset finishing time into the fitting/removal position and to hold it there over a likewise preset time period sufficient for the removal/fitting of workpieces. A semi-continuous workpiece fitting and removal is achieved in this way. The control device ensures in this connection, furthermore, that each lifting device 5 of the respective workpiece holder 6, at the clamping device 7 of which the particular workpiece(s) shall just be replaced now, is displaced vertically upwardly from the lower working position into the upper fitting/removal position by means of the rotatable part 3 after, before or during the displacement of the workpiece holders 6 by means of the rotatable part, is held there over a likewise preset time period sufficient for the removal/fitting of workpieces, and then transferred again vertically downwardly into the working position, after, before or during the displacement of the workpiece holders 6 by means of the rotatable part 3.

(14) FIG. 2 shows another embodiment of a device for the surface finishing of workpieces, wherein identical or functionally identical components are designated by the same reference numbers as in FIG. 1. The device according to FIG. 2 comprises again a container 11 containing a granular grinding and/or polishing material (not shown), which is rotatable about a vertical axis 2 by means of a rotary motion drive. The container 8 is arranged in this exemplary embodiment on a carriage 13, which corresponds to the carriage 13 according to FIG. 1 and on which, e.g., on the underside of which, the rotary drive (not fully recognizable in FIG. 2) of the container 11 is again arranged, and which carriage 13 comprises a carrying plate 18, which is equipped with a carrier shaft 17 and on which the container 11 can be placed in a nonrotatable and self-centering manner.

(15) The device shown in FIG. 2 comprises, furthermore, a manipulator designated by the reference number 110 as a whole in the form of a robot, which carries the workpiece holder 6 or workpiece holders 6 for detachably fixing a workpiece (not shown) to be finished. The robot 110 is, for example, a multiaxial industrial robot, which has a frame 112, on which a carrousel 113 is mounted pivotably about a vertical axis. On the carrousel 113 is seated a bracket 114 with a horizontal mount for a rocker 115, at the (upper) end of which facing away from the bracket 114 an extension arm with a horizontal axis arranged in parallel to the pivot axis of the bracket 114 is mounted. The extension arm, 116 is equipped at its end with a three-axis robot hand 117, which carries the workpiece holder 6. While the carrousel 113 is driven via a pilot motor 118 in relation to the stationary frame 112, a pilot motor 119 is used to drive the rocker 115 and a pilot motor 120 is used to drive the extension arm 116. The three-axis robot hand 117 is driven by three additional pilot motors 121, 122, 123, which are mounted, e.g., at the end of the extension arm 116 facing away from the robot hand 117.

(16) The three-axis robot hand 117 with the workpiece holder 6 is consequently capable both of pivoting the latter in the three-dimensional space in any desired orientation in order to align a workpiece detachably fixed to the workpiece holder 6 in the desired position in relation to the bed of granular material present in the container 11, and of moving the workpiece holder 6 by a translatory motion in any desired direction in space. Moreover, the three-axis robot hand 117 is capable of rotating the workpiece holder 6 especially in the direction of arrow P.sub.4 about its longitudinal axis, the rotary motion control being again designed such that it is capable of accelerating the workpiece holder 6 with a workpiece fixed thereto to and fro during the operation in periodic cycles Z of at most 5 sec between at least one first speed of rotation R.sub.1 and at least one second speed of rotation R.sub.2 and/or of rotating it with continual acceleration at continually different speeds of rotation (see below in this connection with reference to FIGS. 3 and 4), and the corresponding, desired rotary motion profiles can be programmed and entered in an input unit (likewise not shown in the drawing). This can, in turn, also apply to the rotary motion control of the container 11.

(17) FIGS. 3 and 4 show examples of advantageous speed of rotation profiles of the workpiece holder 6 (and/or of the container 11), as they can be carried out by means of the devices according to FIGS. 1 and 2. The speed of rotation n representative of the speed of rotation (e.g., in revolutions per minute (min)) against the finishing time t (e.g., in seconds (s)) on the x axis is plotted on the y axis in the diagrams in FIGS. 3 and 4. As is apparent from FIG. 3, the speed of rotation profile of the workpiece holder 6 and of the workpiece clamped thereon (or also of the container 11) is described there essentially by a sinusoidal curve or in the form of a non-attenuated oscillation, and the workpiece is accelerated to and fro in periodic cycles Z continually with continuous (positive or negative) acceleration between a first speed of rotation R.sub.1 of approximately zero and a second speed of rotation R.sub.2, which may equal, for example, about 2,000 rpm. The second speed of rotation does not, however, have to be necessarily constant, but it may also vary over the finishing time t, i.e., the amplitude A of the approximately sinusoidal curve may change with increasing finishing time (not shown). Likewise, the first speed of rotation R.sub.1 does not necessarily have to equal zero, but it may especially also be a markedly lower speed of rotation compared to the second speed of rotation R.sub.2, e.g., between approximately 0 and about 100 rpm. The duration of the periodic cycles Z may be, for example, between about 1 sec and about 10 sec. The speed of rotation profile of the workpiece holder 6 and of the workpiece clamped thereon (or also of the container 11), which is shown as an example in FIG. 4, differs from that according to FIG. 3 mainly in that the workpiece is accelerated to and fro in periodic cycles Z continually between a first speed of rotation R.sub.1 not equal to zero and a second speed of rotation R.sub.2, which is likewise not equal to zero, but with opposite direction of rotation. The shape of the curve is likewise essentially sinusoidal with a flattening due to inertia in the range of stop (n=0), when the direction of rotation is reversed. The rotary motion, in turn, takes place with continual (positive or negative) acceleration. The values of the first R.sub.1 and/or second speed of rotation R.sub.2 may again equal, for example, approximately 2,000 rpm, but they also may differ from one another as desired, and they may do so not only in their sign. Again, the two speeds of rotation R.sub.1, R.sub.2 do not necessarily have to be constant, but one speed of rotation or both speeds of rotation R.sub.1, R.sub.2 may also change over the finishing time t, i.e., the amplitude component A.sub.1 of the first speed of rotation R.sub.1 up to the zero point (stopping of the workpiece at one point during the reversal of the direction of rotation) and/or the amplitude component A.sub.2 of the second speed of rotation R.sub.2 up to the zero point of the approximately sinusoidal curve may change with increasing finishing time (not shown). The duration of the periodic cycles Z may be, for example, between about 0.25 sec and about 5 sec.

(18) While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.