PROCESS OF GRINDING AND POLISHING GEAR WHEELS

Abstract

Process of grinding and polishing flank surfaces (40) of teeth (50) of toothed wheels (60), comprising the steps of a) providing a grinding device (6), a polishing device (7), a dynamic positioning device (8) and a toothed wheel (60); b) having the grinding device (6) grind the toothed wheel (60); c) removing the toothed wheel (60) from the grinding device (6); d) having the dynamic positioning device (8) bring the flank surface (40) in contact with a polishing body (80) of the polishing device (7) to polish the flank surface; e) having the dynamic positioning device (8) dynamically adjust position and attitude of the toothed wheel (60) relative to the polishing body (80), or having the dynamic positioning device (8) dynamically adjust position and attitude of the polishing body (80) relative to the toothed wheel (60), such that the flank surface is polished by the polishing body. The dynamic positioning device (8) may be a robot.

Claims

1. Process of grinding and polishing a flank surface (40) of a tooth (50) of a first toothed wheel (60), the process comprising the steps, in this sequence, of a) providing a rotational grinding device (6) for grinding a first portion and a second portion of a flank surface (40) of a tooth (50) of the first toothed wheel (60); providing a polishing device (7) comprising a stationary axis (31) and a polishing body (80) rotatable about the stationary axis, the polishing body being adapted for polishing flank surfaces of teeth of a toothed wheel; and providing a dynamic positioning device (8) for holding a toothed wheel (60) and for dynamically adjusting position and attitude of the toothed wheel, relative to the stationary axis (31), during polishing; and providing a first toothed wheel (60); b) having the grinding device (6) grind a first portion and a second portion of a flank surface (40) of a tooth (50) of the first toothed wheel (60); c) removing the first toothed wheel (60) from the grinding device (6); d) having the dynamic positioning device (8) bring the first portion of the flank surface in contact with the rotating polishing body (80) such that the first portion of the flank surface is polished by the polishing body; e) having the dynamic positioning device (8) dynamically adjust position and attitude of the first toothed wheel (60) relative to the stationary axis (31), such that the second portion of the flank surface is polished by the polishing body.

2. Process according to claim 1, wherein the polishing device (7) is a bench grinder.

3. Process according to claim 1, wherein the second portion of the flank surface (40) is polished by the rotating polishing body (80, 81), while the grinding device (6) grinds a portion of a second toothed wheel (61).

4. Process according to claim 1, wherein the second portion of the flank surface (40) is polished by the rotating polishing body (80, 81), while the rotating polishing body (80, 81) remains in contact with the first toothed wheel (60).

5. Process according to claim 1, wherein the dynamic positioning device (8) is a software-controlled robot (8) comprising a plurality of segments (90) and four, five or six axes (100) about which the segments can be independently rotated, whereby the position and attitude of the first toothed wheel (60) are dynamically adjusted by rotating one or more of the axes (100).

6. Process according to claim 5, wherein the robot (8) comprises a sensor for sensing a force, or a contact pressure, exerted by the polishing body (80, 81) on the first toothed wheel (60), and/or a sensor for sensing a sound, and wherein the robot (8) dynamically adjusts position and attitude in response to an output of the sensor(s).

7. Process according to claim 1, wherein the dynamic positioning device (8) dynamically adjusts position and attitude such that the second portion is polished at a second contact pressure different from a first contact pressure at which the first portion is polished.

8. Process according to claim 1, wherein the dynamic positioning device (8) performs step c) of removing the first toothed wheel (60) from the grinding device (6).

9. Process according to claim 1, wherein the polishing body (80, 81) comprises a nonwoven material.

10. Process according to claim 1, wherein the grinding device (6) is adapted to grind the flank surface (40) of the tooth (50) of the first toothed wheel (60) to a surface roughness Rz of 3.5 micrometers or more, as measured using a stylus method and an inductive skidded probe, using a stylus radius of 5 micrometers and a tip angle of 60° per DIN EN ISO 3274 as in force on 29 Jun. 2020.

11. Process according to claim 1, wherein the polishing device (7, 17) is adapted to polish the flank surface (40) of the tooth (50) of the first toothed wheel (60) to a surface roughness Rz of 1.2 micrometers or less, as measured using a stylus method and an inductive skidded probe, using a stylus radius of 5 micrometers and a tip angle of 60° per DIN EN ISO 3274 as in force on 29 Jun. 2020.

12. Process according to claim 1, wherein the first toothed wheel (60) is a gear wheel for use in a gear box of a heavy vehicle, such as a truck, a tractor, a bus, a coach, a railway locomotive or a construction work vehicle or of a wind power generator.

13. Process according to claim 1, wherein the first toothed wheel (60) is a gear wheel made of steel or iron.

14. Process according to claim 1, wherein the first toothed wheel (60) has a diameter of 100 millimeters or more and/or the first toothed wheel (60) has a weight of 1000 grams or more and/or wherein the first toothed wheel (60) has a gear width of 20 millimeters or more and/or wherein the first toothed wheel (60) is a helical gear wheel.

15. Process of grinding and polishing a flank surface (40) of a tooth (50) of a first toothed wheel (60), the process comprising the steps, in this sequence, of a) providing a rotational grinding device (6) for grinding a first portion and a second portion of a flank surface (40) of a tooth (50) of the first toothed wheel (60); providing a polishing device (17) comprising a rotatable polishing body (81) and a dynamic positioning device (8) for dynamically positioning the rotating polishing body (81), adapted for polishing flank surfaces (40) of teeth (50) of a toothed wheel (60), and for dynamically adjusting position and attitude of the rotating polishing body (81) relative to the toothed wheel (60) during polishing; and providing a first toothed wheel (60); b) having the grinding device (6) grind a first portion and a second portion of a flank surface (40) of a tooth (50) of the first toothed wheel (60); c) removing the first toothed wheel (60) from the grinding device (6); d) having the dynamic positioning device (8) bring the rotating polishing body (81) in contact with the first portion of the flank surface such that the first portion of the flank surface is polished by the polishing body; e) having the dynamic positioning device (8) dynamically adjust position and attitude of the rotating polishing body (81) relative to the first toothed wheel (60), such that the second portion of the flank surface is polished by the rotating polishing body.

Description

[0073] Processes according to the present disclosure will now be described in more detail with reference to the following Figures exemplifying a process of the prior art and particular embodiments of the inventive processes:

[0074] FIG. 1 Side view of a grinding and polishing station of a grinding machine performing a process of the prior art;

[0075] FIG. 2 Side view of a grinding device, of a polishing device and of a positioning device performing a first process according to the present disclosure; and

[0076] FIG. 3 Side view of a grinding device, of a polishing device and of a positioning device performing a second process according to the present disclosure.

[0077] FIG. 1 illustrates, in a side view, a grinding and polishing station of a grinding machine 5 performing a process known from the prior art. In this traditional process, a worm-shaped grinding wheel 10 and a worm-shaped polishing wheel 20 are arranged on a rotating axis 30 of a traditional grinding machine 5. The grinding wheel 10 is shown grinding flank surfaces 40 of teeth 50 of a toothed gear wheel 60.

[0078] Once grinding of the flank surfaces 40 is accomplished, the traditional machine 5 moves the gear wheel 60 from a grinding position A, in which the gear wheel 60 is ground by the grinding wheel 10, in a direction indicated by arrow 70, parallel to the axis 30, into a polishing position B, in which the gear wheel 60 is polished by the polishing wheel 20 to achieve a smoother surface of the tooth flanks 40 previously ground by the grinding wheel 10. The same gear wheel 60, drawn in solid lines in its grinding position A opposite to the grinding wheel 10, is drawn in polishing position B in dashed lines to indicate its location some time after grinding.

[0079] Traditional grinding machines like the machine 5 illustrated in FIG. 1 are not designed to process two gear wheels 60 simultaneously. A hypothetical set-up in which a first gear wheel would be polished in the polishing position B by the polishing wheel 20 while a second gear wheel would be ground in the grinding position A by the grinding wheel 10 does not work today, at least for the reason that the axis 30 is common to both the grinding wheel 10 and the polishing wheel 20. For grinding tooth flanks 40 using the grinding wheel 10, the axis 30 moves linearly back and forth in a direction orthogonal to the plane of the drawing at a certain linear speed, which speed is generally higher than the linear speed required for polishing the tooth flanks 40 using the polishing wheel 20.

[0080] Hence when the gear wheel 60 is moved from the grinding position A into the polishing position B, and before the polishing process starts, the linear speed of linear movement of the axis in a direction orthogonal to the plane of the drawing is reduced.

[0081] FIG. 2 illustrates, in a side view, a first process according to the present disclosure. A grinding device 6, e.g. a grinding machine like the machine 5 illustrated in FIG. 1, comprises a worm-shaped grinding wheel 10, arranged on a rotating axis 30 of the grinding device 6. The grinding wheel 10 is shown grinding flank surfaces 40 of teeth 50 of a second toothed gear wheel 61, similar to what was explained for the grinding position A in FIG. 1.

[0082] Different from the prior art process shown in FIG. 1, the grinding device 6 does not perform polishing of the tooth flanks 40 of the second gear wheel 61. Instead, the second gear wheel 61 is unmounted from the grinding device 6, removed from the grinding device 6 and moved to a separate polishing device 7, outside the grinding device 6.

[0083] The polishing device 7 is a bench grinder 7 in which a polishing body 80 rotates about a fixed (i.e. stationary) axis 31. The polishing body 80 is a 3M™ Scotch-Brite™ DB-WL 7S Fine deburring wheel, available from 3M Company, St. Paul, Minn., USA. With this polishing body 80, on certain gear wheels, a surface smoothness exhibiting an Rz of less than 1.0 micrometer and an Ra of less than 0.2 micrometer can be achieved.

[0084] For polishing a gear wheel 60, the gear wheel 60 is held by a positioning device 8 which brings certain flank surfaces 40 of the teeth 50 of the gear wheel 60 in contact with the rotating polishing body 80.

[0085] The positioning device 8 is a software-controlled multi-axis robot 8, such as a Kuka KR 60 HA robot from Kuka AG, Augsburg, Germany. It comprises three segments 90 and six axes 100 of which only two are visible in FIG. 2, about which axes 100 the segments 90 can be independently rotated. This allow for a great flexibility in positioning and adjusting the attitude of the first gear wheel 60 relative to the polishing body 80, and thereby for high-quality polishing.

[0086] In order to polish the flank surfaces 40 adequately, the robot 8 positions the gear wheel 60 suitably for the polishing body 80 to polish a first portion of a specific flank surface 40, and then continuously and dynamically adjusts the position and attitude of the gear wheel 60 relative to the stationary axis 31, such that a second portion of that flank surface 40, adjacent to the first portion, is polished by the polishing body 80. This is performed for all portions of flank surfaces 40 which are supposed to be polished, and for all teeth 50 of the gear wheel 60.

[0087] As FIG. 2 illustrates, a second gear wheel 61 can be ground on the grinding device 6 while a first gear wheel 60 is being polished on the polishing device 7, the first gear wheel 60 having been ground previously on the grinding device 6. The grinding device 6 performs grinding only, so that a “grind-only” process for one single gear wheel 60, 61 can be performed in less time than the traditional “grind and polish” process on the grinding machine 5 of FIG. 1.

[0088] While the grinding device 6 is a high-cost high-precision machine, the polishing device 7 in conjunction with the positioning device 8 are typically less expensive. Separating the lower-value polishing operation on the polishing device 7 from the high-value grinding operation on the grinding device 6 optimizes the return on investment of the grinding device 6 and brings economic benefits.

[0089] In an alternative process according to the present disclosure, the polishing body is mounted on the dynamic positioning device which polishes the stationary gear wheel by dynamically adjusting position and attitude of the polishing body relative to the gear wheel. Such an embodiment is illustrated in FIG. 3, which is a side view of a grinding device 6 and a polishing device 17 comprising a dynamic positioning device 8. The grinding device 6 is identical to the grinding device 6 of FIG. 2. The polishing device 17, however, is different in that the positioning device 8 holds a rotating polishing body 81 which it dynamically positions and orients to polish flank surfaces 40 of teeth 50 of a first gear wheel 60. The positioning device 8 again is a multi-axis robot 8, identical to the robot 8 described in the context of FIG. 2. It is equipped with a mechanism to securely engage the polishing body 81 and rotate it at adequate speeds. The positioning device 8 brings the rotating polishing body 81 in contact with the first portion of the flank surface 40 for polishing the first portion, and thereafter dynamically adjusts the position and attitude of the polishing body 81 relative to the first gear wheel 60 such that the second portion of the flank surface is polished by the polishing body 81.

[0090] The first gear wheel 60 is mounted on a stationary axis 32 so that it can rotate slowly about this axis 32 to facilitate polishing of all its teeth 50. While the polishing device 17 polishes the teeth 50 of the first gear wheel 60, which had been ground on the grinding device 6 previously, the grinding device 6 simultaneously grinds a second gear wheel 61.