METHOD FOR PRODUCING OR MACHINING, BY CUTTING, AN IDENTICAL SET OF TEETH ON EACH OF A PLURALITY OF WORKPIECES, AND MACHINE GROUP AND CONTROL PROGRAM THEREFOR

Abstract

The invention relates to a method for producing or machining, by cutting, an identical set of teeth on each of a plurality of workpieces, in particular at least 4 workpieces, of a workpiece batch on one or more gear-cutting machines (100) having a gear-cutting tool (S), which has a set of teeth having rake faces (5) and having an axis of rotation (B1), in rolling machining engagement, in which method, in the event that a deviation of a set of teeth from the tooth profile sought for said set of teeth is detected or expected, a countermeasure that counteracts said deviation is determined and the production/machining of additional workpieces of said workpiece batch is continued using the countermeasure, the countermeasure being, at least in part, a change in the position of the rake faces relative to the axis of rotation of the tool, which change is brought about by means of grinding performed on the gear-cutting machine or at a grinding machine (140) that belongs to the machine group of the gear-cutting machine.

Claims

1. A method for producing or machining, by cutting, an identical set of teeth on each of a plurality of workpieces of a workpiece batch on one or more gear-cutting machine(s) having a gear-cutting tool (S), which has a set of teeth having rake faces (5) and having an axis of rotation, in rolling machining engagement, in which method, in the event that a deviation of a set of teeth from the tooth profile sought for said set of teeth is detected or expected, a countermeasure that counteracts said deviation is determined and the production/machining of additional workpieces of said workpiece batch is continued using the countermeasure, characterized in that the countermeasure is, at least in part, a change in the position (φ, τ) of the rake faces (5) relative to the axis of rotation of the tool, which change is brought about by means of grinding performed on the gear-cutting machine or at a grinding machine (140) that belongs to the machine group of the gear-cutting machine.

2. The method according to claim 1, in which the gear-cutting tool is not subjected to a coating with a wear-resistant layer between its grinding operation and the continuation of its use.

3. The method according to claim 1 in which the rake faces (5) of the gear-cutting tool (S) are ground to a modified tip rake angle (φ) during the grinding operation.

4. The method according to claim 1 in which the rake faces (5) of the gear-cutting tool (S) are step-ground and during the grinding operation are ground to a modified step-angle (τ).

5. The method according to claim 4, in which the machining engagement takes place using the two-flank method and the modification of the step angle (τ) counteracts an asymmetry portion of the profile error relative to the deviation on the left and right flank.

6. The method according to claim 3 in which the machining engagement takes place using the two-flank method and the modification of the tip rake angle (φ) counteracts a symmetry portion of the profile error relative to the deviation on the left and right flank.

7. The method according to claim 1 in which the countermeasure, in addition to changing the relative position of the rake faces, also includes a dynamic correction in the form of machine axis movements modified in relation to the machine axis movements (A1, Y1) for producing/machining the set of teeth with the detected deviation.

8. The method according to claim 7, in which the dynamic correction is independently calculated by the controller which controls the machine axes for the machining engagement depending on the modification made to the rake faces.

9. The method according to claim 1 in which a machine axis of the machining engagement is used to position the gear-cutting tool during its grinding operation.

10. The method according to claim 1 in which the machining engagement is that of gear skiving or gear shaping.

11. A machine group comprising a gear-cutting machine (100) provided with a controller for producing and/or machining, by cutting, gear teeth on workpieces in rolling machining engagement, and comprising a grinding machine (140) for grinding the rake faces of a gear-cutting tool used on the gear-cutting machine, a controller of the grinding machine being linked to or contained in the controller of the gear-cutting machine, characterized in that the controller(s) is/are designed in at least one operating mode of the machine group for control according to a method according to claim 1.

12. The machine group according to claim 11, in which the gear-cutting machine (100) and the grinding machine (140) form a machine combination (200).

13. The machine group according to claim 11 in which the machine group also has a gearing test machine for measuring profiles and profile errors of gear teeth.

14. A control program which, when executed on a controller of a gear-cutting machine controls said controller to carry out a method according to claim 1.

15. The method according to claim 1 wherein said plurality of workpieces comprises at least four workpieces.

Description

[0025] Further features, details, and advantages of the invention can be found in the following description with reference to the accompanying drawings, in which

[0026] FIG. 1 shows a gear-cutting machine with integrated grinding machine,

[0027] FIG. 2 shows a gear-cutting tool in the form of a step-cut cutting wheel,

[0028] FIG. 3 schematically shows a grinding engagement on a step-ground tool,

[0029] FIG. 4 schematically shows a grinding engagement on a cutting wheel with a tip rake angle,

[0030] FIG. 5 shows an illustration of a step cut,

[0031] FIG. 6 schematically shows the effects of modifying the step angle,

[0032] FIG. 7 shows an illustration of a tip rake angle,

[0033] FIG. 8 schematically shows the effects of modifying the tip rake angle, and

[0034] FIG. 9 shows profile angle deviations before (a) and after (b) application of a corrective rake face modification.

[0035] The machine tool shown in FIG. 1 is a machine 100 designed for skiving with a skiving wheel S. On the workpiece side, the machine 100 has a tool table 80, which is mounted in the machine bed 90 in a rotatably driven manner and in which a workpiece to be machined (not shown in FIG. 1), for example with an internal gearing to be machined, is clampable so as to be rotatable about the machine axis of rotation C1 on the tool side.

[0036] On the tool side, the machine 100 has a linear machine axis X1 for a radial positioning movement of the tool relative to the workpiece, an axis Z1 for a movement of the tool along the axial direction of the table axis C1, and an axis Y1 for a tangential relative movement between the tool and the workpiece. These linear axes X1, Z1 are perpendicular to each other and are implemented via a carriage arrangement 70 in which a linear carriage 72 for the X1 movement carries a vertical carriage 74 for the Z1 movement. The tool head 78 carrying the tool S, which in this embodiment also carries a CNC drive as a direct drive for the tool rotation with the axis of rotation B1, can be moved with a linear carriage 76 for the tangential movement Y1. However, the tangential carriage 76 is rotatably arranged on the vertical carriage 74 with pivot axis A1, so that its carriage movement is only horizontal in the position shown in FIG. 1 and is otherwise inclined relative to the Z1 axis by the set pivot angle A1.

[0037] The gear-cutting machine 100 together with a grinding machine 140, also shown in FIG. 1, forms a machine combination 200. The grinding machine 140 could also have its own clamping for the tool to be reground, but the clamping kept on the tool spindle of the gear-cutting machine 100 is preferred.

[0038] The grinding machine 140 has a movement system with which a grinding tool M can be brought into grinding engagement with the skiving wheel S clamped in the tool clamping of the tool head 78, wherein the tool-side linear and rotational axes also are (can be) used for the production of the grinding engagement. In the illustrated embodiment, the grinding tool M, which in this embodiment is configured in the form of a cup wheel, is movable in a tangential direction Y that is orthogonal to the X1-Z1 plane. It can thus be introduced into the machining space laterally relative to the radial direction X1. This movement in the Y-direction is implemented by a double carriage 41, 42, of which the lower carriage 41 is provided for positioning with axis Y3, while the upper carriage 42 is provided for the lifting movement in the grinding operation. In addition, a grinding spindle 44, which carries the grinding tool M and is driven in rotation about axis D1, is arranged to be pivotable in a plane orthogonal to the Y direction (the pivot axis is denoted by A2), so that an angle is formed in a plane running parallel to the X1-Z1 plane between the axial direction of the axis of rotation D1 and the axis Z1 (C1).

[0039] Variants are also conceivable in which the Y1 axis (possibly in combination with Z1) of the tool head 78 is used for the grinding stroke movement and in some cases axes on the grinding head such as Y2 are then saved. Also conceivable is an additional axis X2 of the grinding head parallel to the X1 direction, or else a further pivot axis with pivot axis X2.

[0040] If it is now determined for a workpiece that has already been machined by the skiving wheel S (e.g. by measuring on a gearing test machine, not shown) that its tooth profile deviates from a predetermined desired tooth profile, this is signaled and, in this embodiment, it is decided that further workpieces of the same workpiece batch are to be machined only after modification of the skiving wheel S, which counteracts the detected profile deviation. The controller (not shown) of the machine combination 200 calculates the changes (in step angle and/or tip rake angle) required for the orientation of the rake faces (of their normal vector), and the grinding machine 140 performs a grinding operation on the skiving wheel S in order to modify it in accordance with these specifications.

[0041] This is described below for a skiving wheel S, which is implemented in the step grinding (see also FIG. 2) and has a non-zero tip rake angle. In this case, the grinding tool M is pivoted in to the modified step angle of the skiving wheel S with pivot axis A2. The pivot axis A1 of the skiving wheel S is pivoted in to the modified tip rake angle of the skiving wheel S. In this setting, a center line of a rake face 5 to be reground (in the indexing method) and facing the side of the grinding tool M runs horizontally in the 90° position relative to the radial axis X1. During the grinding stroke movement (axis Y2), the machining region then moves along the rake face 5 during the grinding stroke, wherein the orientation of the grinding region of the cup wheel M matches the orientation of the modified rake face, so that the rake face 5 can be reground accordingly. It goes without saying that the Z1 axis of the skiving wheel S can be used for the height adjustment of the machining engagement and the delivery, while the XY machine axes are used for positioning.

[0042] By feeding the grinding tool M laterally relative to the radial axis X1, competing space requirements on the machine side are avoided. In addition, due to the parallelism of the grinding stroke and feed direction, vibrations during regrinding are largely avoided. When all rake faces 5 have been successively reground in indexing machining in this way, the grinding tool M is retracted and the gear machining by the skiving wheel S can be resumed and continued.

[0043] The changes resulting from the changed shape of the skiving wheel due to the regrinding are automatically adopted in the machine controller. The machine controller has all the necessary information from the tool design originally stored therein and knowledge of the cutting performed during the regrinding via the axial positions of the machine axes used in this process. If a corrective measure was decided solely by regrinding, the continued machining is performed with the same machine axis controller as before. However, provision can also be made for correcting only a (particularly predominant) portion of the required countermeasure by regrinding. In this case, the machine controller automatically calculates the correction component that has not yet been taken into account depending on the data of the reground tool and, with regard to this correction component, carries out a dynamic correction, as has been customary in the prior art, by changing the machine axis settings for the machining engagement, for example by a modified pivot setting (axis A1) or eccentricity (axis Y1).

[0044] However, in alternative embodiments, the grinding stroke could also be performed in the X1 machine direction, if, for example, the side of the tool is reground that is closest to (0° position, e.g. for internal gearings) or furthest away from (180° position, e.g. for external gearings) the main machine stand (70). In this case, one would preferably leave the pivot axis setting of the tool head 78 set to the machining axis cross angle. For example, if the workpiece machining is that of internal gearings, where work is carried out in the zero° position, one could set the 180° position to twice the opposite axis crossing angle in order to set the rake face 5 horizontal. However, it is also conceivable not to change the axis crossing angle in this way or to leave it in the machining position. Provision could then be made for the grinding head (44) to receive an additional pivot axis; it is also conceivable to use highly conical outer surfaces on a grinding wheel that is not designed as a cup wheel. In the case without a tip rake angle, radially horizontally running rake faces would then have to be reground; in the case of an existing tip rake angle, the regrinding contact could be maintained, for example, by an additional movement of the machine axis Z1. For this purpose, when using a cup wheel, axis A2 (FIG. 1) could be pivoted onto the tip rake angle; the pivot axis A2 of the regrinding head sets the same orientation of the surface to be ground in the machining operation.

[0045] In this variant, one would preferably carry out the regrinding on the side of the tool S which is closest to the main machine stand (carriage arrangement 70) in order to avoid competing for space with the workpiece table 80. This is particularly important when machining internal gearings, because the tool head 78 does not have to be pivoted in via the pivot axis A1. In the case of an external gearing, regrinding would have to be done in the 180° position if one does not intend to pivot in via the pivot axis A1. In the 180° position, conditions for the available installation space are then present which are often more favorable. Particularly in the event that the skiving wheel S does not have a tip rake angle, it is also possible to consider using the rotational movement of the grinding tool M via the spindle carrying the workpieces during machining (in a configuration similar to FIG. 1, the machine table 80) and to carry out the grinding stroke via the radial axis X1. This variant is also conceivable with a tip rake angle not equal to zero, by the radial axis X1 being used for the grinding stroke and a coordinated offset of the engagement region (with respect to the 0° position) with superimposed movements Y1 and Z1 being used.

[0046] Superimposition variants in which the grinding stroke is made in a diagonal direction (i.e., having X and Y directional components) can also be implemented about the existing machine axes of the machine configuration shown in FIG. 1 on the one hand for the skiving wheel S and for the grinding tool M. Then the pivot angle (A1 axis) of the skiving wheel S is preferably set depending on the grinding stroke direction and the angle ξ set for the grinding tool M suitable for the modified head rake angle.

[0047] Depending on the dimensions of the grinding tool M used, it is also conceivable to completely dispense with the realization of a grinding stroke, namely if a rake face 5 is already completely covered. The regrinding would then be plunge grinding.

[0048] In order to precisely determine the relative position between the skiving wheel S and the grinding tool M, it is possible to probe the skiving wheel S with the grinding tool M in the axial direction and in the circumferential direction in order to determine the exact relative height position and relative angular position of the teeth of the tool S with respect to the grinding tool M. This is indicated in particular after a change of machining tool S and/or grinding tool M. This is because pivoting in the grinding head 78 makes it possible to leave the tool S in the machining axis crossing angle. However, the angular position of the tool teeth 4 may already be known due to the previous machining and monitoring of the machine axis B1. Noise detection can be used for contact detection, as can monitoring of the machine axes, for example via a change in torque on the tool or workpiece spindle (B1/C1). Visual detection methods such as sparking could also be used.

[0049] Such probing is also preferred when the grinding tool M itself has been subjected to a dressing operation. It can run fully automatically, i.e., the machine combination 200 performs the probing independently, or semi-automatically with rough pre-positioning by an operator, or alternatively software-guided if the operator controls the probing via the machine user interface. A purely manual variant by probing through axis movements using manual control is also conceivable.

[0050] If, for example, skiving wheels are used that do not have a step grind, a continuous process for regrinding can be used in addition to the intermittent process, for example with a cup wheel.

[0051] If modified tip rake angles of non-zero degrees are to be produced, the rake faces could also be ground in the form of calottes having a surface that is slightly curved in the radial direction. An additional pivot axis (not shown in FIG. 1) of the tool head 78 could also be used to produce head rake angles other than zero degrees.

[0052] In principle, a comparatively flat cup could be used as the cup wheel, or else a dish wheel. Compared to a solid cylindrical wheel, only a narrow region is used in the case of a cup wheel, which can then also be dressed more easily and more accurately, which is advantageous for dressing the grinding tool.

[0053] FIG. 2 shows the shape of a skiving wheel S which can be used on the machine 100 shown in FIG. 1. The step-cut design of the tool teeth 4 having the step-cut rake faces 5 can be clearly seen. In the tool S shown in FIG. 2, there is a non-zero tip rake angle Φ (FIG. 7), and the rake faces are also inclined relative to the radial direction.

[0054] FIG. 3 shows an intervention situation during the regrinding of a cutting wheel S3 with a grinding tool M3 in the form of a cup-shaped grinding wheel. It can be seen that the axes of rotation of the cutting wheel S3 and the grinding tool M3 are pivoted toward one another to match the modified stepped grinding angle τ, once for a right-handed and once for a left-handed cutting design.

[0055] FIG. 4 schematically shows a variant in which a cutting wheel S4 not provided with a step grind is reground by a rotating cylindrical grinding wheel M4. Here you can see how the relative angular position of the respective axes of rotation is set to match the modified tip rake angle of the cutting wheel S4. A grinding stroke movement is indicated by the arrow on both sides. However, it would also be conceivable, for example, to carry out a compensating movement in the direction of the axis of the cutting wheel and to couple it to the grinding stroke. Cylindrical grinding tools of this type, such as M4, could also be used in the case of a step grind, but not in the regrinding position shown in FIG. 4, rather, in a position turned 90° (which is an intermediate position between the 0° close to the skiving head and the 180° remote from the skiving head), in some cases with offset.

[0056] FIG. 5 again shows an illustration of a detail of a step-cut cutting wheel in which the step angle is drawn in. FIG. 6 shows for the purpose of explanation which modifications of the profile of the workpiece gearing are caused by a change in the step angle. Thus, decreasing the step angle in the illustration of FIG. 5 increases the profile angle on the left and decreases the profile angle on the right (FIG. 6A), and increasing the step angle reverses the effect (FIG. 6B). The influence of the modified tool is shown in dashed lines. If you change the tool from rising to the right to rising to the left and vice versa, the influences are mirrored.

[0057] FIG. 7 again shows the tip rake angle φ for a detail of the step-cut cutting wheel shown. Similar to FIG. 6, FIG. 8 corresponds to an illustration of the influence of the modification by regrinding the rake faces 5 to a different tip rake angle. Here, decreasing the tip rake angle causes an increase in the profile angle on both sides of the workpiece (FIG. 8A), whereas increasing the tip rake angle causes a decrease in the profile angle on both sides (FIG. 8B).

[0058] By superimposing both corrections, a symmetrical portion of a profile deviation can thus be corrected by correcting the tip rake angle, and an asymmetrical portion of the profile deviation can be corrected by the influence of the step angle.

[0059] For example, a set of teeth of a workpiece batch has the following gear data: Module 1.7 pressure angle 20° number of teeth 90, helix angle 0 (straight) tooth width 25 mm; root circle diameter 155 mm; tip circle diameter 148 mm, and the cutting wheel used to produce this set of teeth has the following parameters: number of teeth 54; helix angle 10°, as well as a step angle of 10° and a tip rake angle of 5°, and if a profile deviation of 3.9 μm on the left and 9.3 μm on the right is determined for this cutting wheel, as shown in the measurement profile of FIG. 9A, a compensating regrinding of the rake faces of the cutting wheel to a tip rake angle of 3° and a step angle of 12° is carried out in this concrete embodiment. From the measurement profile of FIG. 9B, which was generated by one with the modified (corrected) cutting wheel, it is possible to recognize the effect of the regrinding counteracting the deviation from FIG. 9A.

[0060] As can be seen from the above, the invention is not limited to the implementation concretely illustrated in the preceding examples. Rather, the individual features of the above description and the following claims may be essential, individually and in combination, for implementing the invention in its different embodiments.