METHOD FOR MACHINING TOOTHING SYSTEMS

Abstract

The invention relates to a method for machining toothing systems, in which, for a series of workpieces with an identical target geometry, a toothing system is produced or machined on a respective workpiece in a first machining operation and, in a second machining operation, with a machining tool, additional tooth shaping of the toothing system resulting from the first machining - in particular, chamfering of a tooth end edge of this toothing system - is carried out in a relative positioning with respect thereto, wherein a controller of the second machining operation automatically detects, at least in part, a change in a workpiece property, which is in particular independent of the first machining operation, and/or in a setting of the first machining operation - in particular, with respect to a respectively predetermined reference - and carries out the relative positioning as a function of the detected change.

Claims

1. Method for machining toothing systems, in which, for a series of workpieces with an identical target geometry, a toothing system is produced or machined on a respective workpiece having an axis of rotation in a first machining operation by a first machining tool having an axis of rotation and, in a second machining operation, with a second machining tool having an axis of rotation, additional tooth shaping of the toothing system resulting from the first machining is carried out in a relative positioning with respect thereto, characterized in that a controller of the second machining operation automatically detects, at least in part, a change in a workpiece property, which is independent of the first machining operation, and/or in a setting of the first machining operation and carries out the relative positioning as a function of the detected change.

2. Method according to claim 1, in which the first machining operation is a soft machining operation shaping.

3. Method according to claim 1 in which the second machining operation is a cutting chamfering, and the target geometry has in this respect a predetermined chamfer shape and chamfer size.

4. Method according to claim 1 in which the second machining is carried out in a rolling method .

5. Method according to claim 1 in which the change includes a modification of the flank line of the toothing system.

6. Method according claim 1 in which the change includes a modification of the tooth thickness of the toothing system.

7. Method according to claim 1 in which the change includes a modification of the workpiece axis-related axial position of the tooth end edge of the toothing system.

8. Method according to claim 1 in which the change includes a radial adjustment of the tool of the first machining operation and/or an adjustment of the axial distance of the workpiece and tool axes of rotation of the first machining operation.

9. Method according to claim 1 in which the change includes a pivot angle of the tool of the first toothing system and/or a superposition of machine axes of the first machining operation including tangential axis (Y) or axial axis (Z), and/or additional rotations (ΔC, ΔB), resulting in a flank modification.

10. Method according to claim 1 in which, prior to the second machining operation, a measurement is carried out on the workpiece, the result of which the controller accesses.

11. Method according to claim 1 in which, prior to the second machining operation of a workpiece, no check of the machining result of the second machining operation takes place on the previous workpiece or on one of the last n previous workpieces, where n is preferably at least 5 .

12. Method according to claim 8 in which, during the detection, at least one change is determined from changed machine axis settings of the first machining operating, without resorting to a specific measurement on the workpiece.

13. Method according to claim 1 in which the controller of the second machining operation is designed for a basic setting for performing the second machining operation in accordance with an input of parameters of the target geometry and of the machining tool if including any applicable clamping parameters.

14. Method according to claim 13, in which, when a change is detected, the control parameters of the basic setting, and not the input parameters, are changed.

15. Control program which, when executed on a controller of a toothing machine, controls the machine to carry out a method according to claim 1.

16. Toothing machine for carrying out a first machining operation for producing a toothing system on a workpiece and for carrying out an additional tooth shaping by a second machining operation on the workpiece, characterized in that the toothing machine has a controller designed to carry out a method according to claim 1.

17. Method according to claim 1 wherein the second machining operation comprises chamfering of a tooth end edge of the toothing system.

18. Method according to claim 1 wherein the setting of the first machining operation comprises a predetermined reference with respect to the first machining operation.

19. Method according to claim 2 wherein the soft machining operation comprises hobbing, skiving, or generating shaping.

20. Method according to claim 4 wherein the rolling method comprises the kinematics of hobbing.

Description

[0032] In the following, the invention is further described with reference to embodiments which are explained with reference to the attached figures, of which

[0033] FIG. 1 is a view for illustrating parameters of the process design,

[0034] FIGS. 2a, 2b shows representations of a workpiece blank,

[0035] FIG. 3 shows a schematic illustration of an additional rotation in the case of an axial displacement of a toothing system,

[0036] FIG. 4 is a schematic representation of the tooth edge position at different end edge heights,

[0037] FIG. 5 shows a representation of the tooth edge position at different tooth thicknesses,

[0038] FIG. 6 is a schematic representation of the tooth edge position in the case of a flank line modification,

[0039] FIG. 7 is a schematic representation of the position of the tooth edges when several influences are superposed.

[0040] First, with reference to FIG. 1, some parameters underlying the process design are described using the example of a cylindrical helical toothing system. The process design is basically based upon a gear wheel or a toothing system in which all dimensions are to be exactly the nominal dimension. Considered parameters usually include the number of teeth z.sub.2, the normal module m.sub.n, the normal intervention angle α.sub.n, the inclination angle β at the pitch circle, the profile displacement xm, the tip circle diameter da.sub.2, the root circle diameter df.sub.2, and the tooth width b. In FIG. 1, the diameter at the pitch circle is denoted by d, the inclination angle β relates to the tooth flank, which is further displaced on the pitch circle cylinder as a result of the helical toothing relative to a parallel to the axis of rotation, and the latter is denoted by u in FIG. 1.

[0041] With reference to FIGS. 2a 2b, a typical blank 40 is first shown in FIG. 2a in a perspectival view. In various applications, this blank can have an annular cylindrical outer region 43, from which the subsequent toothing system is produced, as well as a disk-shaped body 41 which is penetrated by a through-bore 42 and is located in a plane orthogonal to the axis of rotation of the toothing system. The outer ends (as viewed in the axial direction) in the form of an upper end face 433 and a lower end face 434 of the outer annular body 43 extending axially over the gear width b can be spaced apart from the end faces of the inner annular body 41. In FIG. 2b, this distance is denoted by b.sub.o (width of turned recess at the top) and b.sub.u (width of turned recess at the bottom). When hobbing a toothing system from the workpiece blank 40, the blank rests on the outer annular body 43, and more precisely on the lower end face 434, for example. During chamfering carried out, for example, with a separate clamping, the workpiece is, on the other hand, mounted via the lower end face 412 of the inner disk body 41 if the tooth end edges are to be chamfered on both end faces of the workpiece toothing system without intermediate clamping change.

[0042] It can also be seen from FIG. 2b that manufacturing-related deviations via changes in b.sub.o and/or b.sub.u when the blank is turned out can result in a fluctuation of the position of the faces 434 and 433 compared to the face 412.

[0043] While such a manufacturing tolerance in the case of hobbing of the toothing system is usually irrelevant even with support on the end face 434, since the axial machining path during hobbing is set to the maximum tooth width in any case, the situation is different when clamping with support on the end face 412. This is because the planes of the upper and lower end faces 433 and 434 are located at a relative position that is different depending upon the manufacturing tolerances during the turning-out, compared to the direct support on which the support face 412 rests. Usually, the reference position is not the direct support for the support face 412, but, rather, a machine reference, e.g., the height of the machine table, which includes clamping means. Compared to the “clamping height” h defined on the machine side, there is thus possibly a deviation in the axial position of the planes of the upper and lower end faces 433, 434 relative to the target position. It goes without saying that the word selection, “height,” refers to extensions in the direction of rotation of the workpiece, and not only vertical machines, but also horizontal machines or machines in oblique axis positions can be used.

[0044] When the tooth edges of a toothing system are chamfered, the position of the teeth relative to the table axis is first determined with a sensor, and the tooth edges to be machined in the upper and lower end faces 433, 434 are thus also determined. With knowledge of the axial distance of the upper end face of the toothing system, e.g., to the plane of the sensor, the toothing system can be positioned, e.g., via the machine table axis, in such a way that, when viewed axially, the tooth edges on the upper end face 433 can be rotated into the desired position, and likewise for chamfering on the lower end face 434.

[0045] While it would be sufficient in the case of straight toothing systems to set the for setting the planes of the upper or lower end faces 433, 434 to the desired machining position via a mere axial movement, the workpiece must additionally be rotated in the case of a helical toothing system, in order to hold the tooth space at the desired chamfer height in the machine center.

[0046] In the case of an axial correction ΔZ, this results in a required additional rotation of ΔC = ΔZ x 360°/pz, where pz is the pitch height of the helical toothing system (the tooth space follows a helical line with pitch height), and is given by z x m.sub.n x Π/sin | β |. When the table is rotated in the clockwise direction, ΔC has the same sign as that of the axial displacement in the case of a right-inclined β and has the reverse sign in the case of a left-inclined β. The reverse sign rule applies when the table is rotated counter-clockwise (rotation about workpiece axis C).

[0047] This additional rotation with axial displacement is shown again schematically in FIG. 3, with position sensor 8, and machining planes 5, 6, in which the tooth edges are located.

[0048] With regard to the relative position of the chamfering tool to the planes of the end faces 433 and 434, it is possible to use, for example, a quadruple of pivot angle η, axial distance ΔX, distance to machine center ΔY, distance to the chamfering plane ΔZ, i.e., for the plane of upper end face 433 (η.sub.3, ΔX.sub.3, ΔY.sub.3, ΔZ.sub.3′), and accordingly at the lower plane of the end face 434 (η.sub.4, ΔX.sub.4, ΔY.sub.4, ΔZ.sub.4).

[0049] With regard to the absolute machine position of the chamfering tool, the values of the relative position can be used for the pivot angle, the axial distance, and the distance to the machine center, whereas, with regard to the distance to the chamfering plane, axial values of Z.sub.3 = h - b.sub.u + b + ΔZ.sub.3 for the upper plane and Z.sub.4 = h - b.sub.u - ΔZ.sub.4 must be taken into account in addition to the rotations C.sub.3 or ΔC.sub.4.

[0050] FIG. 4 shows the situation of the position of the tooth edges at different heights of the end edges again. The nominal dimension of the gear width b is between a minimum gear width b.sub.min and a maximum gear width bmax. The position of the sharp edge of the left flank at the nominal tooth width is denoted by B, and that of the blunt edge of the right flank is denoted by E. For deviations from higher toothing width (bmax), these positions are denoted by C or F, and, for smaller toothing widths, by A and D. It can thus be seen how manufacturing-related deviations when the blank is turned out can lead to different positions of the tooth edges at the resulting different heights of the end edges, i.e., position changes can be taken into account during a subsequent machining (second machining), e.g., chamfering, which changes are independent of the preceding toothing system production itself, and can thus occur even if the machining of the toothing system were to take place ideally at 100% on nominal dimension production.

[0051] However, a change in position of the tooth edges can also result in the case of changes, e.g., of the tooth thickness, resulting from the toothing production. This is illustrated in FIG. 5, in which B and E denote the position of the sharp edge of the left flank and blunt edge of the right flank, respectively, at nominal tooth thickness, which are displaced in the case of thinner teeth in the plane orthogonal to the workpiece axis of rotation to G, K in thinner teeth, or H, J in thicker teeth.

[0052] As another example, FIG. 6 shows a change in the position of the tooth edges in the case of a flank line modification f.sub.Hβ arisen during the toothing production. As can be seen in this regard from FIG. 6, the position of the nominal positions B, E changes to L, N in the case of a modification β-, and to a position M, P in the case of a modification β+. If only the crowning (symmetrical edge line modification c.sub.β) changes, the position of the nominal positions B, E does not change.

[0053] The case of a superposition of several influences of the variants illustrated using FIGS. 4, 5, and 6 is shown in FIG. 7.

[0054] Again, b denotes the sharp edge of the left flank in the nominal position, and E denotes the blunt edge of the right flank in the nominal position, with associated profile W of the tooth space center at inclination angle β in the nominal dimension. In contrast, the profile V of the resulting tooth space center with inclination angle β correlates with the position of the resulting position U of the acute position of the left flank and the resulting position Z of the blunt edge of the right flank, wherein the axial distance between the upper end face 433 according to the nominal dimension and the upper end face 3″ at the height of U, Z is denoted by ΔZ.sub.o.

[0055] Compared to the nominal values, the axial distance and the inclination angle change for the example of the hobbing when toothing corrections are produced; thus, a tooth thickness correction leads to a constant axial distance change ΔX.sub.1, whereas a flank line angle correction likewise has a contribution ΔX.sub.2 (Z) to the axial distance change, which is dependent upon the axial position Z, and additionally an inclination angle change Δβ.

[0056] In contrast, the following changing values must be taken into account during chamfering: The inclination angle change leads to a pitch height change Δpz, the pitch height change, as explained above, leads to an additional rotation ΔC.sub.pz, the height difference of the upper end faces 433 and 3″ of FIG. 7, Δz.sub.o and the additional rotation ΔC.sub.0 associated with the transition from end face 433 to end face 3″.

[0057] The relative positioning as a function of the detected change thus takes place to an end position of an absolute machine position of the chamfering tool from plane 433 to 3″, to the effect that the same pivot angle is assumed (η3” = η.sub.3). For the axial distance, X.sub.3” = ΔX.sub.3 + ΔX.sub.1 + ΔX.sub.2 (Z) is set, the distance to the machine center can be left as is, the distance to the chamfering plane is set to Z.sub.3 = h - b.sub.u + b + ΔZ.sub.3 + ΔZ.sub.0, and ΔC.sub.3 + ΔC.sub.pz + ΔC.sub.0 results for the rotation. The index “3” here stands for the face 433.

[0058] As already explained above, the last-mentioned contributions ΔC serve the goal of rotating the workpiece tooth space at the height of the chamfering plane by workpiece rotation into the machine center, and are composed of the rotation from the sensor plane to the original plane 3, ΔC.sub.3, an additional rotation ΔC.sub.pz in the case of any inclination angle change, and the additional rotation ΔC.sub.0, which accounts for the transition from plane 433 to plane 3″.

[0059] The above explanations relate predominantly to the upper face 433; a corresponding procedure is used for the lower face 434.

[0060] It goes without saying that deviations from exact calculations are possible, and that approximations, estimates, and/or rougher corrections, e.g., according to correction tables, can also be used, and that the above representation represents only one possible type of implementation.

[0061] For the implementation of the relative position, it is possible with respect to individual axes to reposition – instead of the machine axis of the chamfering tool – the workpiece-side machine axes, which lead to the same relative positioning as the determined absolute positioning of the chamfering tool.

[0062] Similar to the toothing production of the first machining operation by means of hobbing, skiving, or generating shaping could also be used, and the changes of the first machining operation leading to the axial distance change and/or inclination angle change could be used as the basis.

[0063] In this respect, the invention is not limited to the method described in the exemplary embodiments. Rather, the features of the following claims as well as of the above description, or in combination, can be essential for the realization of the invention in its various embodiments.