Method for machining a toothing and toothing machine designed for same, as well as computer program product for same

Abstract

The invention relates to a method for machining a toothing (2) having an axis of rotation (C), in which a machining tool (4), which is rotationally driven about its axis of rotation (B), removes material from the toothing while executing a relative motion between the machining tool and toothing to generate a flank geometry of the toothing, which has been predefined over the full width of the toothing, in a machining operation, wherein the predefined flank geometry matches a motion control that defines a motion path of the tool center with respect to the toothing axis of rotation, said motion control having a defined, non-vanishing axial advancement with a defined advancing motion between machining tool and toothing, wherein in a first machining process, the relative motion is only executed for generating a part, more particularly a significant part (5), of the flank geometry according to this motion control, while a further part, more particularly the remaining part (6), of the flank geometry is generated in a second machining process, in which the distance between the tool center and the toothing axis of rotation with respect to the fixed motion path changes in a manner wherein the tool center moves away from the toothing, and in which the change to the machining operation caused thereby is counteracted by an additionally executed change in motion of the relative motion with respect to the motion control of the first machining process.

Claims

1. A method for machining a toothing (2) having a right tooth flank and a left tooth flank and an axis of rotation (C), in which a machining tool (4) having an axis of rotation (B) and a tool center (N) is driven in rotation about said axis of rotation (B) to remove material from the toothing, in a machining engagement, while performing relative movement between the machining tool and the toothing in order to produce a flank geometry on the right and left tooth flanks of the toothing that is predefined over a full width of the toothing, said method comprising: a first machining process, said first machining process comprising carrying out a first relative movement between the machining tool and the toothing in a first machining engagement for producing said predefined flank geometry completely along said full width on one of said right flank and said left flank and along a portion (5) of said full width on the other of said right flank and said left flank of said toothing according to a first controlled movement of the machining tool and the toothing on a machine tool having a controller, said first controlled movement defining a first movement path of the tool center with respect to the axis of rotation of the toothing, said first movement path having a defined axial feeding in the direction of the toothing axis of rotation and a defined axial advancement between the machining tool and the toothing in the direction of the toothing axis of rotation, and a second machining process wherein said predefined flank geometry is produced along a further portion of said full width on said other of said right flank and said left flank, said second machining process comprising carrying out a second relative movement between the machining tool and the toothing in a second machining engagement according to a second controlled movement of the machining tool and the toothing on said machine tool having said controller, the second controlled movement defining a second movement path of the machining tool with respect to the axis of rotation of the toothing by (1) changing the distance of the tool center from the axis of rotation of the toothing relative to said first movement path so as to move the tool center away from the toothing and (2) carrying out a counteracting compensating correction movement to bring said machining tool into machining engagement with said further portion of said full width on said toothing thereby resulting in changing the first machining engagement to the second machining engagement, to produce said predefined flank geometry along said further portion of said full width, wherein said first machining process and said second machining process are part of the same machining pass.

2. Method according to claim 1 wherein the toothing and the machining tool are in rolling engagement with one another during the first and second relative movements between the machining tool and the toothing.

3. Method according to claim 1 wherein the axes of rotation of the toothing and the machining tool are arranged at an axis intersection angle (Σ) that is not zero.

4. Method according to claim 3 wherein the axis intersection angle in the first and/or second machining process is at least 8°.

5. Method according to claim 1 wherein the machining tool is a tool having a geometrically determined cutting edge.

6. The method of claim 5 wherein said machining tool comprises a skiving wheel.

7. Method according to claim 1 wherein the second machining process further includes axial feeding in the direction of the toothing axis of rotation and wherein an extent of said axial feeding is reduced to less than 70% compared to an extent of the axial feeding of the first machining process.

8. Method according to claim 1 wherein the toothing part is part of a workpiece (3) having a further structure which, with respect to the toothing axis of rotation, has a radial extension at an axial distance from one of the axial toothing ends.

9. The method of claim 1 wherein the second machining process does not include movement of the machining tool in the direction of the toothing axis of rotation.

Description

(1) Further details, particularities and advantages of the invention can be found in the following description with reference to the accompanying drawings, in which

(2) FIG. 1 schematically shows a contact line in a toothing machining process,

(3) FIG. 2 shows a skiving wheel that machines a toothing,

(4) FIG. 3 shows profiling cut sequences during skiving,

(5) FIG. 4 shows a sequence of tooth flank views which matches that of FIG. 3,

(6) FIG. 5 shows path deviations in various embodiments, and

(7) FIG. 6 shows a skiving machine.

(8) FIG. 1 schematically shows a tooth gap of a toothing, in which LF designates the left and RF designates a right tooth flank, between which the gap base is depicted. The circle contained therein with the two black-filled quadrant sectors symbolizes a zero point N in the tool system, for example the (tool center axis at the level of an) axial position of the tooth tip of a tooth of a skiving wheel toothing. The line designated by K in FIG. 1 is the contact line, as it results in the profile formation of the toothing during power-skiving, and which extends in the radial as well as in the axial length. The contact line corresponds to the contact between the machining tool and the toothing at a fixed moment of the machining engagement and can thus be assigned to a defined axial position of the tool zero point. It can be seen in the indicated position of the tool zero point that (in the case of axial feeding in FIG. 1 from top to bottom) the production of the flank geometry of the left flank LF is more advanced than that of the right flank RF. If the horizontal line passing through the tool zero point is considered to be the axial end E of the toothing, the left flank would already be finished in the illustrated position, but the machining of the right flank would not yet be finished in the region between the contact line and the axial toothing end E. The double arrow shown on the right in FIG. 1 indicates which additional axial relative movement would have to be performed by the tool and the toothing so that machining of the right flank is also finished. This axial distance is the overtravel path which is covered by further axial feeding in conventional machining to the end of a particular machining pass until the toothing machining has also been completed on the right flank.

(9) FIG. 2 schematically shows a skiving wheel 4 and an internal toothing 2 produced by means of the skiving wheel 4. The viewing direction in FIG. 2 is that of a radial (advancement) axis. It can be seen that the axis of rotation B of the skiving wheel is inclined with respect to the axis of rotation C of the toothing by an axis intersection angle Σ. The position shown in FIG. 2 corresponds to that in which the machining of toothing is completed using conventional skiving, and the tool zero point is below the axial end of the toothing, and is spaced apart axially therefrom by the overtravel S.

(10) The workpiece 3 shown which supports the toothing 2 has yet another contour axially below the toothing end, which contour is referred to in the following as an interfering contour. The double-sided arrow drawn in FIG. 2 indicates the distance ZS from the tool center in the axial direction, which must be maintained so that there can be machining without interference, despite the interfering contour.

(11) FIG. 3a-d show, in a section orthogonal to the toothing axis, a tooth gap contour and also profiling cuts of the cutting movement of the skiving wheel, which are used in one embodiment of the invention in the second machining process, in which the axial feeding in the position of the tool zero point shown in FIG. 1 is stopped, and the machining tool plunges radially out of the tooth gap of the toothing such that single-flank cuts are made.

(12) FIG. 4a-d show, synchronously to the view in FIG. 3a-d, how the profile of the toothing changes in the second machining process. The region above the diagonal contact line K.sub.a, K.sub.b, K.sub.c which can be seen in FIG. 4a-c indicates the flank region which has already been finished according to the desired flank geometry, and the region below is the region which still has an oversize relative to the desired flank geometry. Illustration a) in FIG. 4 for example shows the oversize situation below the contact line, which matches the situation from FIG. 1. In this view, which corresponds to the transition from the first to the second machining process, there is still a full radial advancement depth of the first machining process, as can be seen from illustration a) of FIG. 3.

(13) In the machining example shown, there is now a radial plunging movement, as can be seen from the relative displacement of the envelopes in the radial axial direction X from illustration a) to the left to illustration d) to the right in FIG. 3. Furthermore, however, it can also be seen that the position of the envelopes changes with respect to the position of the tooth gap in the tangential direction Y due to a correspondingly configured additional movement. The superposition of the radial plunging movement and the additional movement is coordinated such that the envelope is moved along the flank geometry to be produced, and the tooth flank is thus finished, without the need for further axial feeding. The feeding in the second machining process is thus radial/tangential feeding in this embodiment. Without the tangential additional movement, an oversize and thus a considerable deviation from the desired flank geometry would remain.

(14) In this way, the overtravel path which can be seen in FIG. 2 can in particular be completely omitted, as a result of which axial clearance with respect to a required axial distance ZS is achieved in order to avoid a collision with an interfering contour. Preferably, this axial clearance is created to a maximum, and a correspondingly reduced clearance is maintained if an axial feed movement is still carried out, but at a lower rate, and the radial plunging movement thus begins at an earlier axial position than is conventional. In other words, machining as outlined in FIGS. 3 and 4 can also be achieved if, during the second machining process, there is still (a smaller degree of) axial feeding. The toothing depth is maintained up to the axial toothing end E.

(15) The portions of the overtravel movement, relating to the tangential axis Y, which are used to achieve the profiling cut progressions shown in FIG. 3b-c with respect to the toothing, can be achieved in many ways. On the one hand, this could be achieved by an additional rotation ΔC of the axis of rotation of the toothing, but also by an additional rotation ΔB about the axis of rotation of the tool, or a superposition of these. However, a tangential machine axis Y could also be changed compared with the first machining process. Optionally, this may also involve a change in the axis intersection angle Σ.

(16) The preferred variant, however, lies in a superimposition of radial feeding, which ensures a continuously changed radial feeding compared with the first machining process, with an additional rotation in particular of the axis of rotation C of the toothing.

(17) In particular when machining external toothings, it is also conceivable for a tangential plunging movement via machine axis Y to be realized, and in turn to use an additional rotation of the axis of rotation (B) of the toothing and/or the axis of rotation (C) of the toothing as an additional counteracting movement axis for producing the flank geometry.

(18) FIG. 5 shows further examples of the change in the movement path of the tool center with respect to the movement path of the first machining process when it is assumed that the machining according to the movement control of the first machining process is continued. FIG. 5a corresponds to the preferred embodiment of a plunging movement without further axial feeding. On the other hand, the embodiment of FIG. 5b shows a variant in which axial feeding is maintained, but this is superimposed by a radial plunging movement. This variant can be used, for example, if the interfering contour only has a radial extent insofar as the danger of collision is substantially present only if the tool is still advanced with its full radial depth after passing through the overtravel. FIG. 5c shows another variation which does have an overtravel, but this is reduced.

(19) The clearance obtained by saving on the overtravel can be used in several ways. On the one hand, a larger axis intersection angle Σ can be used to machine a workpiece having an interfering contour, and the tool can be designed for the larger axis intersection angle. A conventional machining process using a tool designed in this way would then, when machining the workpiece over the full axial width with the movement axis control of the first machining process, mean either that a safety distance from the interfering edge is no longer maintained, or that this would already lead to a collision with the interfering contour, but this is actually avoided by the transition to the second machining process according to the invention. Due to the larger axis intersection angle, the cutting speed increases and reduced machining times can be achieved.

(20) Another possibility is to use the clearance not to change the tool design or for larger axis intersection angles and cutting speeds, but rather to use it to machine workpieces which have a small axial distance between the axial toothing end and the interfering contour in the skiving process, and which otherwise could not be machined by skiving, but only by generating-shaping.

(21) FIG. 6 shows a skiving machine 100 with a schematically indicated controller 99. The machine axes X (radial), Y (tangential), Z (axial), A (pivot axis for setting axis intersection angle Σ), C2 (axis of rotation of the tool) and C (axis of rotation of the workpiece) allow the required relative movements, so that the control device 99 can control the skiving machine 100 in order to carry out the above-described method. The tool head arranged on the tangential slide (for Y) is pivotally mounted on a cross-slide assembly (for X and Z) by means of tangential slides. FIG. 6 is simply an example of a suitable machine; other configurations are possible, e.g. suspended spindles, pick-up systems, etc.

(22) The invention is not limited to the specifications given in the examples provided above. Rather, for the invention, the features of the following claims as well as the above description may be essential for implementing the invention in its different embodiments.