METHOD FOR MANUFACTURING OF GEARS

Abstract

A method for producing gears, includes the following: machining of gears with a gear tool in a single-indexing method, wherein the gear tool produces tooth gaps on each of the gears by machining. A pitch compensation with compensation parameters is predefined for the gears; wherein the compensation parameters are predefined by a machine control as a function of a wear condition of the gear tool.

Claims

1. A method for manufacturing gears, the method including the following steps: machining of a plurality of gears with a gear tool in a single-indexing method, wherein the gear tool produces a plurality of tooth gaps on each gear of the plurality of gears by chip removing machining, and wherein a pitch compensation with compensation parameters is predefined for the plurality of gears; wherein the compensation parameters are preset by a machine control system depending on a wear condition of the gear tool.

2. The method according to claim 1, wherein first compensation parameters for the pitch compensation are predefined for a first wear condition of the gear tool, second compensation parameters for the pitch compensation are predefined for a second wear condition of the gear tool, the gear tool has a lower gear tool wear in the first wear condition than in the second wear condition, and the first compensation parameters are different from the second compensation parameters.

3. The method according to claim 2, wherein the pitch compensation for a first subset of the plurality of gears is performed using the first compensation parameters, and the pitch compensation is performed for a second subset of the plurality of gears with the second compensation parameters.

4. The method according to claim 2, wherein the second compensation parameters are calculated automatically by the machine control system from the first compensation parameters, wherein a conversion formula is stored in the machine control system to convert first compensation parameters into second compensation parameters.

5. The method according to claim 1, wherein the number of gears machined with the gear tool is determined, wherein the number of gears machined with the gear tool represents the wear condition of the gear tool.

6. The method according to claim 1, wherein a current consumption and/or a power consumption of a tool spindle drive with which the gear tool is rotationally driven is measured, wherein a change in current consumption and/or power consumption represents the wear condition of the gear tool.

7. The method according to claim 1, wherein a pitch deviation of at least one gear of the plurality of gears is determined, the at least one gear on which the pitch deviation is measured is in particular one of the last five manufactured gears of a subset of the plurality of gears, and the subset of the plurality of gears comprises in particular twenty gears or more, wherein the pitch deviation represents the wear condition of the gear tool.

8. The method according to claim 7, wherein the pitch measurement is carried out within a machine tool with which the machining of the plurality of gears with the gear tool is also carried out.

9. The method according to claim 7, wherein the pitch measurement takes place in one chucking, in which both the machining of the gear to be measured with the gear tool and the measuring of the gear to be measured take place while the gear to be measured is chucked on a workpiece spindle of the machine tool, and the gear to be measured is not disengaged from the workpiece spindle after gear cutting and before measuring.

10. The method according to claim 1, wherein the wear condition of the gear tool is determined by a wear measurement on cutting edges of the gear tool.

11. The method according to claim 1, wherein the presetting of the compensation parameters includes the following method step: reading out stored compensation parameters from a data memory of the machine control.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0067] The disclosure is explained in more detail below by means of a drawing illustrating an exemplary embodiment, wherein the drawings each show schematically:

[0068] FIG. 1 shows a gear in transverse section with measuring devices for pitch measurement;

[0069] FIG. 2 shows a measurement result of a pitch deviation with and without pitch compensation;

[0070] FIG. 3A shows a ring gear in perspective view from above;

[0071] FIG. 3B shows a detail enlargement of the ring gear from FIG. 3B;

[0072] FIG. 4 shows a machine tool for gear machining;

[0073] FIG. 5 shows a gear tool and a ring gear;

[0074] FIG. 6 shows a bar blade and a tooth gap;

[0075] FIG. 7A shows a bar blade in new condition;

[0076] FIG. 7B shows the bar blade from FIG. 7A in a wear condition; and

[0077] FIG. 8 shows a flow diagram of a method according to the disclosure.

DETAILED DESCRIPTION OF THE DRAWINGS

[0078] FIG. 1 shows a gear 100 whose teeth are numbered 1-12. The geometry of the gear 100 is measured using an optical measuring system 200 and a tactile measuring system 300. The measurement of individual pitch deviations f.sub.pt for the right flanks 110 of the gear 100 is shown as an example.

[0079] A nominal pitch P.sub.SOLL is the theoretically predefined distance between two adjacent right flanks 110 or two adjacent left flanks 120 at the level of a diameter D. The individual pitch deviation f.sub.pt is calculated for each tooth as the difference between the actually measured pitch P9.sub.IST minus the nominal pitch P.sub.SOLL.

[0080] The individual pitch deviations f.sub.pt are positive for tooth 6, since the measured pitch P.sub.IST is larger than the nominal pitch P.sub.SOLL. The individual pitch deviations f.sub.pt are negative for tooth 8 because the measured pitch P.sub.IST is smaller than the nominal pitch P.sub.SOLL. The theoretical flank to be generated is indicated by a dashed line in each case. It is understood that these are highly schematic representations to illustrate the deviations occurring in the micrometer range.

[0081] FIG. 2 shows an example of a result of such a pitch measurement for the right flanks. The total pitch error F illustrates a total pitch deviation F.sub.P and also shows the individual pitch deviations f.sub.pt from tooth to tooth. In the diagram, the individual pitch deviations f.sub.pt are added up one after the other according to the numbering of the teeth. The total deviation F for tooth 7 therefore represents the sum of all individual pitch deviations f.sub.pt up to tooth 7 in the diagram.

[0082] The shaded bars in FIG. 2 show exemplary pitch deviations after pitch compensation has been performed for the gear 100. The pitch deviations could therefore be significantly reduced by the pitch compensation.

[0083] In the following, the method according to the disclosure is described with reference to the manufacture of ring gears 400 for a toothed gearing of a bevel gear. If reference is made here to a toothed gearing of a bevel gear, it is a pairing of a pinion and an associated ring gear, which are set up to convert speeds and torques between crossing or skew axes by rolling the teeth in mutual mesh.

[0084] FIG. 3A shows an exemplary perspective view of a ring gear 400 from above. FIG. 3B shows a detail enlargement of the ring gear 400, with the enlarged detail in FIG. 3A labeled III-B.

[0085] The ring gear 400 has teeth 410, wherein each tooth 410 has a concave flank 411 and a convex flank 412, and tooth gaps 413 are formed between the teeth 410. In the enlarged view shown in FIG. 2B, an actual pitch P.sub.IST is shown as an example for two adjacent convex flanks 412.

[0086] FIG. 4 shows a machine tool 500 for manufacturing bevel gears, such as a ring gear 400 shown in FIG. 3A. The machine tool 500 has a tool spindle 510 for accommodating a bar cutter head 520. The bar cutter head 520 is a gear cutting tool 520 and is arranged for individually cutting the teeth 410 of a respective ring gear 400. The machine tool 500 has a machine control system 540. A tool spindle drive 550 is used to rotate the gear tool 520 about its own axis.

[0087] The ring gear 400 to be machined is held on a workpiece spindle 530 of the machine tool 500.

[0088] Relative motion or infeed motion of the cutter head 520 relative to the ring gear 400 is effected by three linear axes X, Y, and Z, a pivot axis C, and a workpiece rotation axis B. The pivot axis C essentially causes the workpiece spindle 530 to rotate or pivot about the Z axis. The

[0089] B axis causes the ring gear 400 to rotate about its own axis L. The tool spindle drive 550 for generating the gear tool rotation or cutting speed causes rotation about the X axis, wherein this rotation is denoted A.

[0090] FIG. 5 shows an example of the ring gear 400 with the cutter head 520. The cutter head 520 has a plurality of bar blades 521 that are arranged to produce the concave and convex flanks 411, 412.

[0091] According to the disclosure, a method for producing gears 400 is specified, comprising the method steps: gear cutting of a plurality of gears 400 with the gear cutting tool 520 in the single-indexing method, wherein the gear cutting tool 520 produces a plurality of tooth gaps 413 on each gear 400 of the plurality of gears 400 by machining, and wherein a pitch compensation with compensation parameters is predefined for the plurality of gears 400. The compensation parameters are predetermined by the machine control system 540 of the machine tool 500 depending on a wear condition of the gear cutting tool 520.

[0092] For example, for each tooth 410 or for each tooth gap 413, a theoretical depth position of the gear cutting tool 520 in the X direction is corrected by a value Kx and a theoretical rotational position of the ring gear 400 is corrected by a value Kb, as exemplified in FIG. 6. Here, the dashed line in FIG. 6 shows the uncompensated position of the gap while the solid line shows the compensated position of the gap.

[0093] The machine control system 540 takes into account the wear condition of the gear cutting tool 520.

[0094] It may be provided that first compensation parameters for pitch compensation are predetermined for a first wear condition of the gear tool 520, that second compensation parameters for pitch compensation are predetermined for a second wear condition of the gear tool 520, that the gear tool 520 has a lower tool wear in the first wear condition than in the second wear condition, and that the first compensation parameters are different from the second compensation parameters.

[0095] FIG. 7A shows a bar blade 521 of the gear cutting tool 520 in a new condition. The new condition according to FIG. 7A corresponds to the aforementioned first wear condition. FIG. 7B shows a bar blade 521 of the gear cutting tool 520 in a partially worn condition after manufacturing some ring gears 400. The partially worn condition according to FIG. 7B corresponds to the aforementioned second wear condition.

[0096] In FIG. 7B, it is shown by way of example that breakouts 525 are formed in the region of a top cutting edge 522, a main cutting edge 523 and a rake face 524 of the bar blade. These breakouts 525 increase the friction and the forming work during chip removal.

[0097] Therefore, insofar as the bar blades 521 of the gear tool 520 are in the partially worn condition, the heat input increases during manufacturing of a ring gear 400 compared to manufacturing with the gear cutting tool 520 in the new condition. Accordingly, the expansion of the material of the ring gear 400 also increases during manufacturing, so that pitch compensation with the first compensation parameters, which enables reliable adherence to predefined tolerances for the new condition of the gear tool 520, is no longer effective for the worn condition of the gear tool 520. Therefore, for the worn condition of the gear cutting tool 520, a pitch compensation with second compensation parameters that differs from the new state is predefined by the machine control system 540.

[0098] According to the present embodiment of the disclosure, it is accordingly provided that the pitch compensation for a first subset of the plurality of gears 400 is performed with the first compensation parameters and that the pitch compensation for a second subset of the plurality of gears 400 is performed with the second compensation parameters.

[0099] In this case, the plurality of gears 400 may have a predetermined number of pieces that are intended to be manufactured with the gear cutting tool 520 before the gear cutting tool is reconditioned. For example, it may be provided that a quantity of three hundred gears 400 is manufactured with the gear cutting tool 520 before the gear cutting tool 520 is reconditioned. In this regard, the first subset for which pitch compensation is performed with first compensation parameters may be two hundred pieces, for example, such that the second subset for which pitch compensation is performed with second compensation parameters is one hundred pieces.

[0100] In order to select the suitable compensation parameters, the wear condition of the gear tool 520 is determined. In particular, influencing variables or parameters are taken into account that allow indirect conclusions to be drawn about the wear condition of the gear tool.

[0101] According to a first variant of the method according to the disclosure, it is provided that the wear condition of the gear tool 520 is inferred on the basis of the number of gears 400 toothed with the gear tool 520. For example, insofar as it is known for the gears 400 that the pitch compensation no longer permits the required tolerances from a number of pieces of approximately two hundred gears 400 manufactured, the machine control system 540 can automatically use second compensation parameters instead of the first compensation parameters from the two hundredth or one hundred and eightieth component manufactured, which take into account the expected gear tool wear. Accordingly, compensation parameters for the various wear conditions of the gear tool 520 may be stored in a database of the machine control system.

[0102] Accordingly, the sequence of the first method variant is as follows according to FIG. 8: In step a, a gear 400 with first compensation parameters is manufactured. In step b, it is checked whether the number of manufactured gears is less than or equal to, for example, 180. If the check in step b shows that the number of gears manufactured is less than or equal to 180, a gear 400 with first compensation parameters is manufactured again. If the check in step b shows that the number of gears manufactured is greater than 180, a subsequent gear 400 and the further subsequent gears 400 are manufactured with second compensation parameters according to step c.

[0103] According to a second variant of the method according to the disclosure, it is provided that the wear condition of the gear tool 520 is inferred on the basis of a current and/or power consumption of the tool spindle drive 550 of the tool spindle 510, with which the gear tool 520 is rotationally driven.

[0104] In the present case, the current and/or power consumption of the tool spindle drive 550 of the tool spindle 510, which is used to rotationally drive the gear tool 520, is continuously recorded during the production of the gears 400 and evaluated by means of the machine control system 540. To the extent that it is determined within the machine control system 540 that an average power consumption during the cutting of a gear 400 has increased by more than more than 20% compared to previously manufactured gears or a predetermined target value, an adjustment of the compensation parameters for subsequent components may be made by the machine control system 540. This is because the increased power consumption indicates dulling or wear of the gear tool 520.

[0105] According to FIG. 8, the sequence of the second method variant is, for example, as follows: In a step a, a gear 400 is manufactured with first compensation parameters. Subsequently, in a step b, it is checked whether the average current and/or power consumption of the tool spindle drive 550 of the tool spindle 510 has increased by more than 20% compared to a predetermined set value. If the average current and/or power consumption of the tool spindle drive 550 of the tool spindle 510 has not increased or has increased by less than 20% compared to the predetermined setpoint, another gear 400 is manufactured using the first compensation parameters. If the average current and/or power consumption of the tool spindle drive 550 of the tool spindle 510 has increased by more than 20% compared to the predetermined setpoint, a subsequent gear 400 and further subsequent gears 400 are manufactured with the second compensation parameters according to step c.

[0106] According to a third variant of the method according to the disclosure, it is provided that the wear condition of the gear tool 520 is concluded on the basis of a measurement of a pitch deviation of at least one gear 400 of the plurality of gears 400, that the at least one gear 400 at which the pitch deviation is measured is in particular one of the five most recently manufactured gears of a subset of the plurality of gears 400, and that the subset of the plurality of gears comprises in particular 20 gears or more. In this way, it is possible to check at predetermined intervals to what extent the currently used compensation parameters allow effective compensation of the pitch deviations, or whether the gear tool wear has already progressed to such an extent that the machine control system 540 must make an adjustment to the compensation parameters in order to reliably maintain the predetermined tolerances.

[0107] Here, the pitch measurement is performed within the machine tool or gear cutting machine 500. The pitch measurement is therefore performed in one setup, in which both the gear cutting of the gear 400 of the plurality of gears 400 with the gear tool 520 and the measurement of the gear 400 are performed while the gear 400 is clamped to the workpiece spindle 530 of the machine tool 500 and the gear 400 is not released from the workpiece spindle 530 after the gear cutting and before the measurement. The measurement of the pitch deviation is performed mainly in a tactile manner.

[0108] According to FIG. 8, the sequence of the third method variant is, for example, as follows: In a step a, a gear 400 is manufactured with first compensation parameters. Then, in a step b, it is checked whether the pitch deviation of the gear 400 to be measured is within the predefined tolerances. If the pitch deviation is within the tolerance, further gears 400 are manufactured with first compensation parameters until a new measurement of a further gear is performed in step b. If the pitch deviation then lies outside the tolerance, the subsequent further gears 400 are manufactured with the second compensation parameters according to step c.

[0109] According to a fourth variant of the method according to the disclosure, the wear condition of the gear cutting tool 520 is determined by a wear measurement on cutting edges 521, 522, 523 of the gear cutting gear tool 520. The wear measurement can be carried out optically.

[0110] According to FIG. 8, the sequence of the fourth method variant is, for example, as follows:

[0111] In a step a, a gear 400 is manufactured with first compensation parameters. Subsequently, in a step b, it is checked whether the gear tool wear of the gear tool 520 is within the predefined tolerances. If the gear tool wear is within the tolerance, further gears 400 are manufactured with first compensation parameters until a new measurement of the gear tool wear in step b is performed. If the gear tool wear is then outside the tolerance, the subsequent further gears 400 are manufactured with the second compensation parameters in accordance with step c.

[0112] In this case, the compensation parameters are predefined by reading out stored compensation parameters from a data memory of the machine control system.

[0113] The method variants described above can be combined with each other.

[0114] From step c, gear tool wear can continue to be monitored analogously to FIG. 8 in order to use third or fourth compensation parameters if necessary.