Method for determining a tool path and method for material removal from a workpiece

Description

[0001] The invention relates to a method for determining a tool path for material-removing machining of a workpiece in a processing machine. Furthermore, the invention relates to a computer program for implementing such a method and a computer program product comprising a storage medium on which the program code of such a computer program is stored. The invention also relates to a method for material-removing machining of the workpiece.

[0002] When complex components are machined, different milling strategies can be used for different areas of the component. For example, in finishing, the choice of machining strategy for a specific component area can be based, among other things, on its local surface inclination. The component is often divided into areas that can be described as "steep" or "flat." A different strategy can then be assigned to the flat and steep areas, taking their different inclinations into account. The division into flat and steep areas can be achieved, for example, by using a suitable limit angle. Surfaces or surface sections that have an inclination angle below the limit angle are then considered flat areas; surfaces or surface sections that have an inclination angle greater than the limit angle are considered steep areas.It may also happen that a transition between a flat and a steep area is located within a single surface, for example in the case of a curved surface that includes steep and flat sections.

[0003] For many machining situations, level-by-level finishing ("Z-level" machining) can be suitable for machining steep areas. Parallel planes are laid through a component model at a constant distance, for example, along the z-axis of the NC coordinate system and intersect with the surfaces characterized as steep. Based on the resulting cutting contours, tool paths can then be calculated along which a tool carves out the contours.

[0004] For flat component areas, however, a different strategy is often chosen, for example a projection method in which a regular two-dimensional path pattern is projected onto the respective surfaces in the direction of the z-axis.

[0005] It should be noted that the machining strategy chosen for flat or steep areas would be less suitable for the other type of area, as the resulting path segments would diverge significantly due to the significantly different inclination. Therefore, different methods are combined to determine the path segments of a tool path. To ensure complete machining of the workpiece in such a combination, the path segments of the different areas, or their envelope contours, are joined together seamlessly.

[0006] The invention is based on the finding that with such an approach, machining in connecting sections, for example in a section in which a steep and a flat area of ​​the workpiece merge into one another or border one another, takes place with a large amount of material intervention, since the tool moves into an area that is not yet completely machined. If, for example, a steep area is first machined using a plane-based strategy before projection-based machining of an adjacent flat area takes place, a lot of material is still present at the bottom of the connecting section when the tool reaches the end of a plane-based machining line there. The invention is also based on the finding that there is often little space available in connecting sections, which is why short and / or strongly curved retraction segments must be used, which can lead to abrupt movements of the tool.Both can lead to vibrations, excessive tool wrap, and the formation of machining marks, which can result in reduced surface quality. The invention is also based on the finding that a similar situation can occur when connecting segments are traversed between machining lines located close to a connecting section. In this case, too, the space may not be sufficient to create sufficiently smoothly curved path segments along which the tool can be lifted in a controlled manner. This can also result in reduced quality. In general, machine accuracy errors can become more apparent in confined spaces.

[0007] DE 10 2016 117 932 A1 discloses a method for the material-removing machining of rounded surfaces of a workpiece using a milling tool with a conical-convex cutting contour. The machining of the rounded surface is carried out by moving the tool along a longitudinal direction of the

[0008] rounding surface and is guided at an angle to it, so that an essentially sickle-shaped material engagement is formed.

[0009] Based on the prior art, the present invention is therefore based on the object of providing an improved method for machining workpieces that have workpiece sections that are to be machined using different machining strategies. In particular, the invention is based on the object of improving surface quality and / or reducing the load on the tool and / or machine.

[0010] This object is achieved according to the invention by a method having the features of claim 1, a computer program having the features of claim 11, a computer program product having the features of claim 12 and a method having the features of claim 13.

[0011] A method is proposed for determining a tool path for material-removing machining of a workpiece in a processing machine by moving a tool along the tool path. The processing machine can be a CNC machine and / or a three-, four-, or five-axis machine. In some embodiments, the tool is a milling tool.

[0012] The workpiece comprises a first workpiece section and a second workpiece section adjacent to the first workpiece section. The first workpiece section and the second workpiece section can be spatially oriented differently. Alternatively or additionally, they can also differ by at least one boundary condition, such as the presence or absence of other adjacent surfaces and / or objects, a material quality, a desired machining strategy, etc. The tool path comprises a first path region for machining the first workpiece section, which comprises path segments that are adapted to a geometry of the first workpiece section using a first adaptation strategy.The tool path comprises a second path region for machining the second workpiece section, which comprises path segments that are adapted to a geometry of the second workpiece section by means of a second adaptation strategy that differs from the first adaptation strategy.

[0013] The method comprises determining the first path region such that the path segments of the first path region cover the first workpiece section except for a first edge region, which is specifically omitted by the path segments of the first path region, even though path segments could be adapted to the first edge region using the first adaptation strategy. In other words, the method comprises determining the first path region such that the path segments of the first path region effect and / or define a machining of the first workpiece section except for the first edge region. The first edge region can, in particular, directly border the second workpiece section.

[0014] Furthermore, the method comprises determining the second path region such that the path segments of the second path region cover the second workpiece section except for a second edge region, which is specifically omitted by the path segments of the second path region, even though path segments could be adapted to the second edge region using the second adaptation strategy. In other words, the method comprises determining the second path region such that the path segments of the second path region effect and / or define a machining of the second workpiece section except for the second edge region. The second edge region can, in particular, directly border the first workpiece section and / or the first edge region.

[0015] The method also includes determining a transition region of the tool path, which comprises path segments that cover at least the first edge region and the second edge region, wherein the path segments of the first path region, the second path region, and the transition region together completely cover the first workpiece section and the second workpiece section. In other words, the method includes determining a transition region of the tool path, which comprises path segments that effect and / or define machining of the first edge region and the second edge region.

[0016] The features according to the invention make it possible to achieve an improved method for machining workpieces that have workpiece sections that are to be machined using different strategies. This can improve surface quality. Furthermore, stress on the tool and / or the machine used can be reduced. By recessing the edge regions according to the invention and specifically defining a transition region, excessive material engagement when reaching the transition region can be avoided. A connecting section of the workpiece covered by the transition region can therefore be machined gently and with high quality. Sufficient space can be created to produce gently curved approach / departure segments or segments optimized with regard to machining quality.This means that the desired component geometry can be produced completely and without errors, particularly in the transition area, without machining errors occurring.

[0017] The process differs from residual material processing methods, particularly in the targeted removal of edge areas. For example, the transition area is not a residual material processing area and / or is not used to process a residual material section.

[0018] It is to be understood that the method steps recited herein are performed in the order in which they are recited, for example in the order in which they are recited in the claims.

[0019] The path segments of the transition region can be adapted to a geometry of the workpiece, such as a geometry of a connecting section of the workpiece, by means of a third adaptation strategy that differs from the first adaptation strategy and / or the second adaptation strategy.

[0020] The tool path can be generated, in particular, using software and / or a computer system that can be used independently of the processing machine. A CAM system, for example, can be used for this purpose. The method can include the creation of NC code as control commands for controlling machine axes of a processing machine, particularly as part of post-processing.

[0021] It is understood that any machining machines and correspondingly any tools are encompassed by the invention. The machining may be a machining operation. The machining may include milling, drilling, grinding, etc., as well as correspondingly suitable tools.

[0022] The tool path is, in particular, a path along which a defined point of the tool and / or a tool contour is moved. This can be, for example, a center point, a contact point, a specific point on a tool cutting edge, and / or a specific point on a tool axis.

[0023] The two workpiece sections are, in particular, directly adjacent to one another. According to some embodiments, the first workpiece section and the second workpiece section are spatially oriented significantly differently. This can mean that a surface normal of the first workpiece section and a surface normal of the second workpiece section enclose an angle of at least 10°, at least 20°, at least 30°, at least 45°, or even at least 60°. These surface normals can be mean surface normals of the respective workpiece section, any surface normal at a point of the respective workpiece section, and / or a surface normal at a characteristic point of the respective workpiece section, such as its center of gravity, saddle point, inflection point, extreme point, center point, etc.This can also include the workpiece sections merging into one another, for example via a fillet surface. Surface normals along a boundary line between the workpiece sections can then correspond to one another. Surface normals in center points and / or at characteristic points, in particular outside the fillet surface, can, however, be oriented significantly differently as described. The first workpiece section can be a complete workpiece surface of the workpiece and can therefore border on all sides on another workpiece surface that is distinguishable from the first workpiece section and geometrically offset. The same can apply alternatively or additionally to the second workpiece section. In other words, the first workpiece section can be a first workpiece surface and / or the second workpiece section can be a second workpiece surface.A workpiece section could also consist of multiple surfaces and / or surface parts. In other embodiments, the first workpiece section and / or the second workpiece section can be a surface section of a larger surface. Furthermore, the two workpiece sections can be part of a common surface and can merge into one another continuously and / or with continuous tangents and / or curvature.

[0024] According to the invention, the first adaptation strategy is a plane-based adaptation strategy. According to the invention, the second adaptation strategy is a projection-based adaptation strategy. The first adaptation strategy and the second adaptation strategy can differ fundamentally from one another, i.e., for example, they cannot be converted into one another by selecting prefactors, boundary conditions, parameter ranges, etc. The first adaptation strategy provides plane-based path segments, so that machining in the first path region occurs plane-by-plane, and the second adaptation strategy provides projection-based path segments, so that the second path region is based on a projection of a path pattern onto the second workpiece section.In some embodiments, the aforementioned adaptation to the geometry of the respective workpiece section includes defining the relevant path segments such that they follow the geometry of the respective workpiece section and effect and / or define its complete machining in the covered area. The adaptation strategies can also differ in that different tool angles are used, especially if the path segments are calculated using the same method.

[0025] According to the invention, the first edge region and the second edge region can be selected such that they cover (partial) sections of the workpiece that could be machined by extending the first path region and / or the second path region. In particular, a deliberate / targeted / intentional omission of the edge regions occurs, which could fundamentally be avoided. The transition region can cover a transition section / connecting section of the workpiece, within which the two workpiece sections adjoin one another and / or merge into one another. The path segments of the transition region define and / or effect, in particular, machining of the workpiece in this transition section / connecting section.

[0026] According to the invention, the first workpiece section is a steep section with respect to a spatial axis, the surface normal(s) of which is / are inclined by more than a first critical angle with respect to the spatial axis. According to the invention, the second workpiece section is a flat section, the surface normal(s) of which is / are inclined by less than a second critical angle with respect to the spatial axis. The surface normal(s) is / are a surface normal at contact points and / or touch points of the tool. The first critical angle and the second critical angle can be identical, so that only a single critical angle is used. However, different critical angles can also be used. As a rule, one of the workpiece sections is a steep section and the other workpiece section is also a flat section.The method can therefore be applied in particular to the machining situations outlined at the beginning, in which a workpiece is to be machined that has significantly differently oriented workpiece sections that can be described as flat or steep.

[0027] In a further development, the method further comprises comparing at least one geometric parameter, in particular a radius, of the tool with a geometric parameter, in particular a radius of curvature, which describes a connecting section of the first workpiece section and the second workpiece section. The geometric parameter of the tool can also be a radius of curvature of a cutting edge of the tool. This can refer to any curved section of the cutting edge, for example a corner radius in a radius milling cutter, a short and / or long semi-axis of an elliptical cutting section, a radius of curvature of a bulged region of a conically convex tool, etc. The connecting section can be formed by the first workpiece section and / or the second workpiece section. In particular, the two workpiece sections can adjoin one another without any gaps.The connecting section is then a section in which the two workpiece sections merge into one another and / or a close region of a boundary line between the workpiece sections. In other words, in this way, based on a suitable limit value and / or a suitable user specification, it can be automatically determined whether the workpiece sections should be machined according to a tool path determined according to the invention. The comparison can be based on a threshold value. The threshold value can be specified by a user. A high degree of efficiency can be achieved in particular if the comparison serves to determine whether or not the edge regions should be left out and / or the transition region should be determined.If, for example, the tool radius and / or a radius of curvature of a cutting edge of the tool or another geometric parameter of the tool is, in particular considerably smaller, perhaps many times smaller, than the radius of curvature of the connecting section, it may be expedient to perform machining without deliberately recessing the edge areas. Traversing the connecting section with the tool may then not result in any loss of quality. For this purpose, a factor of at least 1.5, at least 2, at least 3 or at least 5 can be provided, as can an additional or alternative factor that can be specified by a user. If, on the other hand, the radius of curvature of the connecting section is similar to or even smaller than the geometric parameter of the tool, machining across the connecting section cannot be carried out without further ado.The strategy described above of deliberately cutting out edge areas for different track areas and determining a transition area can then be useful.

[0028] The space gained by omitting the edge regions can be particularly expediently utilized in the generation of tool paths that result in high surface quality and / or gentle machining if the method further comprises determining connecting segments and / or approach segments and / or departure segments, which are at least partially included in the transition region, for the first path region and / or for the second path region. The connecting segments and / or approach segments and / or departure segments are in particular part of the respective path region. In other words, required tool movements into the transition region can be permitted if machining of the workpiece takes place in sections that are covered by the first path region and / or the second path region.The connecting segments and / or approach segments and / or departure segments can at least partially cover the connecting section and / or extend into it and / or overlie it.

[0029] The transition zone is reached when the tool moves along the tool path, particularly after the first and second path zones. In other words, machining occurs first in the first and second path zones before machining in the transition zone. This allows the transition zone to also be used for reworking or smoothing the boundary areas between the two path zones.

[0030] According to a further development, the method can further comprise determining the transition region such that its path segments overlap the first path region and / or the second path region at least in sections. This allows a high machining quality to be achieved in the area of ​​approach and retraction movements or connecting segments between machining lines of the first and second path regions by creating a smooth transition. Thus, in addition to machining a connecting section that has not yet been machined, the transition region can also effect remachining of workpiece sections that have already been machined according to the first path region and / or the second path region.Smooth transitions can be achieved in particular if the path segments of the transition region are defined such that they are gradually lifted from the workpiece where they overlap the first path region and / or the second path region. The transition region can cause the boundary areas of those workpiece sections covered by the first path region and / or the second path region to be smoothed.

[0031] A particularly efficient determination of the transition region can be achieved, for example, if the method further comprises determining the first path region by determining preliminary path segments, which are based in particular on complete coverage of the first workpiece section using the first adaptation strategy, and subsequently shortening the preliminary path segments in the first edge region. Alternatively or additionally, the method comprises determining the second path region by determining preliminary path segments, which are based in particular on complete coverage of the second workpiece section using the second adaptation strategy, and subsequently shortening the preliminary path segments in the second edge region. The shortening of the preliminary path segment orThe preliminary path segments can be based on at least one boundary curve that is superimposed on the first workpiece section and / or the second workpiece section. The method can therefore initially comprise adapting path segments to the geometry of the workpiece section in question, whereby this adaptation does not yet have to take into account that a transition region is to be determined and edge regions are to be left out. The adaptation can therefore be carried out in a straightforward and reliable manner. The method can then comprise specifically leaving out the edge regions by changing the path segments that have already been determined and completely cover the workpiece sections by shortening and / or trimming them where the workpiece sections adjoin one another. In this way, after the adaptation has been carried out, a section is defined for which the path segments of the transition region can then be defined.As mentioned, the transition area can be selected to overlap, so that the boundaries of the recessed section do not necessarily have to coincide with the boundaries of the transition area. The boundary curve can be determined taking into account the geometry of a connecting section and / or a boundary line that runs between the workpiece sections. For example, the boundary curve can define a predetermined distance from the first workpiece section and / or the second workpiece section.

[0032] According to some embodiments, the tool can have an actual tool radius that is taken into account when determining the tool path. In some cases, the determination of the transition region can additionally be based on at least one tool radius that is larger than the actual tool radius. The determination of the edge regions can also be based on at least one tool radius that is larger than the actual tool radius. This allows the edge regions and the transition region to be determined easily and reliably. For example, in the case of multiply curved and / or geometrically complex surfaces and / or surface complexes, the method can thus be carried out with a high degree of automation because the determination of recessed regions based on the larger tool radius is robustly possible for almost any workpiece geometries.The enlargement can be by a factor of at least 1.1, at least 1.2, at least 1.5, at least 2, at least 3, at least 5 or an even greater value. The determination of the transition region can be based on the enlarged tool radius in that this is used as the basis for a calculation that defines and / or limits the extent of the first path region and the second path region. By using the enlarged tool radius, those sections can be defined that can be machined by the first path region and the second path region, in particular without the aforementioned problems of excessive wrap, strong vibrations, etc. occurring. This can result in the first edge region and / or the second edge region, for example as a remaining region. In addition, the transition region can result from this, although it should be noted that this can nevertheless be designed to overlap.

[0033] According to a further development, the starting point and / or end points of path segments of the first path region, which define the first edge region, are determined by taking into account the at least one enlarged tool radius to determine how far the tool can be moved towards the second workpiece section when machining the first workpiece section. Alternatively or additionally, the starting point and / or end points of path segments of the second path region, which define the second edge region, can be determined by taking into account the at least one enlarged tool radius to determine how far the tool can be moved towards the first workpiece section when machining the second workpiece section. The determination of the first path region and / or the second path region based on the enlarged tool radius can comprise a collision-avoiding approach to the corresponding other workpiece section.In particular, the increased tool radius is not used to determine the distance between path segments of the respective path area. Since the tool radius used here is larger than the actual tool radius, but is preferably used only to approximate the corresponding other workpiece section, not the relative spacing of path segments, a recessed edge area results, but complete coverage or machining in the first path area when the tool with the actual radius is used.

[0034] It should be noted that reference to a "surface" in this disclosure is not intended to be limited to mathematical surfaces. A "surface" may also be, for example, a set of triangles or other polygons in a triangular mesh or a polygon mesh.

[0035] The invention further relates to a computer program for carrying out a method according to the invention. The computer program comprises, in particular, program code that, when executed on a computer, effects the execution of the aforementioned method steps.

[0036] The invention also relates to a computer program product comprising at least one storage medium on which program code of a computer program according to the invention is stored. The storage medium can comprise a volatile and / or a non-volatile data memory.

[0037] Furthermore, the invention relates to a method for material-removing machining of a workpiece by means of a tool, in particular a milling tool, which is guided for machining, in particular in a five-axis CNC machine, for example, along a tool path which was determined in a method according to the invention and / or by means of a computer program according to the invention and / or by means of a computer program product according to the invention.

[0038] The present invention is described below by way of example with reference to the accompanying figures. They show: Fig. 1 shows a schematic representation of a processing machine; Fig. 2 shows a schematic perspective representation of a workpiece; Fig. 3 shows a further schematic perspective representation of the workpiece; Fig. 4 shows a schematic perspective representation of the workpiece with path segments adapted to a first workpiece section; Fig. 5 shows a schematic perspective representation of the workpiece with path segments adapted to a second workpiece section; Fig. 6 shows a schematic perspective representation of the workpiece with path segments adapted to the first and second workpiece sections; Fig. 7 shows a schematic perspective representation of the workpiece with first and second path regions adapted to the first and second workpiece sections; Fig. 8 shows a schematic perspective representation of the workpiece with first and second path regions adapted to the first and second workpiece sections and with a transition region; Fig.9 shows a schematic plan view of a section of the workpiece to illustrate a first method for determining recessed edge regions; Fig. 10 shows a schematic plan view of a section of the workpiece to illustrate a second method for determining recessed edge regions; Fig. 11 shows a schematic perspective view of a section of the workpiece with an adapted tool path that includes first travel segments; Fig. 12 shows a schematic perspective view of a section of the workpiece with an adapted tool path that includes second travel segments; Fig. 13 shows a schematic view of a section of a workpiece with a tool path that has a transition region that is selected to overlap path regions; Fig. 14 shows a schematic perspective view of another workpiece with first and second path regions adapted to a first and a second workpiece section; Fig.Fig. 15 shows a schematic perspective view of the further workpiece with a transition region adapted to a connecting section; Fig. 16 shows a schematic perspective view of the further workpiece with first and second path regions adapted to the first and second workpiece sections and with the transition region; Fig. 17 shows a schematic view of a first connecting section of a workpiece; Fig. 18 shows a schematic view of a second connecting section of a workpiece; Fig. 19 shows a schematic flow diagram of a method for determining a machining path; and Fig. 20 shows a schematic flow diagram of a method for material-removing machining of a workpiece.

[0039] For the following description, reference is made to Fig. 1Reference is made to the schematically illustrated processing machine 10. This is to be understood purely as an example, particularly with regard to its movable axes. Other machine axes and / or a different number of machine axes may be provided in other embodiments.

[0040] The processing machine 10 comprises a workpiece table 12 on which a workpiece 14 can be arranged or secured. The workpiece 14 can be machined by the processing machine 10. In the example shown, this is a milling machine.

[0041] The processing machine 10 also comprises a processing unit 16 with a tool 18 for processing the workpiece 14. In the illustrated case, the processing unit 16 comprises, for example, a tool spindle. In the exemplary case illustrated, the tool 18 is a milling tool, in particular a ball-end mill. Machining is performed by guiding the tool 18 along a tool path. This is described in more detail below. Along the tool path, the tool 18 is at least temporarily in engagement with the material to be removed from the workpiece 14, thereby creating a target geometry for the workpiece 14.

[0042] The processing machine 10 is multi-axis or N-axis, for example, 5-axis. For illustration purposes, the workpiece table 12 defines two rotary axes A, C, and the processing unit 16 defines three linear axes X, Y, Z. However, other configurations are also possible.

[0043] The processing machine 10 further comprises a control unit 20 that can output control commands to the N different machine axes. The processing machine 10 is, in particular, a CNC machine, and the control commands can accordingly be NC commands.

[0044] Furthermore, a CAM system 22 is provided. In many embodiments, this is not part of the processing machine 10, but can operate independently of the machine. Using the CAM system 22, a machining path can be generated based on CAD data of the workpiece 14 or its target geometry. From this path, control commands for the processing machine 10 or its control unit 20 can be generated in a generally known manner during post-processing.

[0045] An exemplary computer program product may include a storage medium 58, which may be part of and / or usable with a computer of the CAM system 22. The storage medium may store program code of a computer program containing instructions that, when executed on a computer, effect the implementation of the method described below for determining a tool path for a material-removing machining operation of the workpiece 14.

[0046] The Figures 2 and 3show schematic perspective views of a workpiece 14. The workpiece 14 has a plurality of surfaces and / or workpiece sections that are spatially differently oriented. Of particular note below are a first workpiece section 26 and a second workpiece section 28, which are directly adjacent to one another. For ease of understanding, the workpiece sections 26, 28 are shown as flat surfaces. However, it is understood that the workpiece sections 26, 28 can be curved and / or can comprise a plurality of partial surfaces. By way of example, the first workpiece section 26 comprises two flat surfaces that are connected to one another via an inner edge and / or an inner connecting section. For the following description, however, only one of these surfaces could alternatively be regarded as the first workpiece section 20.

[0047] The first workpiece section 26 is a steep section with respect to a spatial axis z. A surface normal n of the first workpiece section 26 forms a large angle with the spatial axis z. Alternatively or additionally, a surface normal on the other partial surface of the workpiece section 26 could also be taken into account in this example. The second workpiece section 28 is a flat section with respect to the spatial axis z. Its surface normal n' forms a small angle with the spatial axis z. To categorize surfaces as steep or flat, a critical angle can be used, for example an angle of 30°. In the case shown, the surface normal n of the first workpiece section 26 is inclined by more than the critical angle, whereas the surface normal n' of the second workpiece section 28 is inclined by less than the critical angle.As explained above, two different critical angles can also be used.

[0048] If workpiece sections other than flat surfaces are considered, a surface normal can be considered for categorization purposes for each contact point / point of contact of the tool 18 with the workpiece 14. In the illustrated case with the flat workpiece sections 26, 28, these surface normals are constant across the respective workpiece section 26, 28.

[0049] The Figures 4 to 6 illustrate a conventional adaptation of a tool path to a geometry of the workpiece 14 in an area of ​​the two workpiece sections 26, 28. As in Fig. 4 As can be seen, a level-by-level adjustment to steep workpiece sections is carried out. The resulting path segments, shown as solid lines, extend as far as possible to the edges of the steep workpiece sections. As further shown in Fig. 5 As shown, a projection-based adjustment is used for flat workpiece sections. The resulting path segments also extend as far as possible to the edge of the respective workpiece sections. This results in the overall Fig. 6The tool path shown covers the first workpiece section 26 and the second workpiece section 28. The resulting path segments extend directly to an inner edge and / or a concave area between the workpiece sections 26, 28, where "directly" in this context describes an approximation within the scope of what is possible according to the cutter radius. There, a tool movement along connecting segments and / or when approaching and / or retracting path segments, in particular also along the actual path segments, can result in a large wrap around the tool 18 or a large material engagement, which can be accompanied by the quality problems explained above.

[0050] In contrast, in the Figures 7 and 8the result of a method described herein is shown. A tool path 24 determined by this method comprises a first path region 30 for machining the first workpiece section 26. Path segments 32 of the first path region 30, only some of which are provided with reference symbols, are adapted to the first workpiece section 26 using a plane-based method. Furthermore, the tool path 24 comprises a second path region 34 for machining the second workpiece section 28, which path segments 36 comprise, only some of which are also provided with reference symbols. These are adapted to the second workpiece section 28 using a projection-based method.

[0051] As mentioned above, the adaptation strategies in other embodiments may also differ by using different tool angles, especially although the path segments are calculated using the same method.

[0052] As in Fig. 7 As shown by way of example, the method provides that the path regions 30, 34 are determined in such a way that the respective workpiece section 26, 28 is not covered by path segments 32, 30 in a first edge region 38 or a second edge region 40, although path segments could in principle be adapted to the edge regions 38, 40 using the respective adaptation strategy. In a connecting section 46 of the two workpiece sections 26, 28, there are therefore no path segments of the first path region 30 or the second path region 34. In particular, the area in which a large material intervention would otherwise occur is thus left out, as described above with reference to the Figures 4 to 6 was explained.

[0053] The method further provides that a transition region 42 of the tool path 24 is determined, which covers the edge regions 38, 40, so that the transition region 42 and the two path regions 30, 34 or their respective path segments 32, 36, 44 completely cover the first workpiece section 26 and the second workpiece section 28.

[0054] In the exemplary case, a spiral strategy is selected in the transition area 42. Due to the spiral filling path of the transition area 42, no approach / departure movements are necessary within the transition area. In the case shown, the path segments 44 of the transition area 42 run from the outside to the inside, whereby machining in the opposite direction is also possible. The transition area 42 can, however, also be determined using other adaptation strategies, whereby in particular a different adaptation strategy is used than for the first path area 30 and the second path area 34. The path segments 44 of the transition area 42 are referred to in connection with the Figures 11 and 12 discussed again below.

[0055] Different strategies can be used to determine the edge regions 38, 40. A first possible strategy is described in Fig. 9It is understood that the described procedure can be used both for the first edge region 38 and for the second edge region 40, or for the first workpiece section 26 and / or for the second workpiece section 28. This is also indicated by the double use of reference numerals in Fig. 9 clarified.

[0056] According to this approach, the determination of the path segments 32 / 36 of the corresponding path area 30 / 34 is generally based on an actual radius rw of the tool 18. To determine the edge area 38 / 40, however, a starting point and / or an end point of a specific path segment 32 / 36 is determined by using an enlarged tool radius rv as a basis. This can, for example, be larger than the actual radius rw by a factor of 1.5, a factor of 2, a factor of 3, or any other factor. By using the enlarged radius rv, the starting point and / or the end point of a path segment 32 / 36 is further away from an edge of the respective workpiece section 26 / 28 than would be required based on the actual tool radius rw and / or than would result from the actual tool radius rw.This results from a simple collision check of the enlarged tool used in the calculation with the adjacent workpiece section 28 / 26. By determining all path segments 32 / 36 of the relevant path area 30 / 34 according to the enlarged tool radius rv, a completely recessed edge area 38 / 40 is obtained, as required by the method.

[0057] An alternative approach is Fig. 10shown. Here, path segments 32 / 36 are initially determined for the entire workpiece section 26 / 28 based on the actual tool radius rw, i.e. up to its edges. In this way, preliminary path segments 54 are obtained. Starting from these preliminary path segments 54, a boundary curve 56 is used, which is superimposed on the relevant workpiece section 26 / 28. The preliminary path segments 54 are shortened in accordance with this boundary curve 56 in order to obtain the final path segments 32 / 36. The boundary curve 56 can, for example, run parallel to a surface of the adjacent workpiece section 28 / 26 and / or parallel to an edge of the workpiece section 26 / 28 in question and / or at a predetermined distance therefrom and, if necessary, also follow a non-linear course. A recessed edge region 38 / 40 can also be obtained in this way.

[0058] According to yet another alternative, the path segments 32 / 36 are determined from the beginning only up to a certain distance with respect to an edge of the relevant workpiece section 26 / 28, ie without using a boundary curve, but by checking calculated distance values ​​of path segment points.

[0059] The Figures 11 and 12show enlarged sections of the workpiece 14. The transition area 42 is selected by way of example such that its path segments 44 border on the path segments 32, 36 of the first path area 30 and the second path area 34, thereby overlapping the approach and departure segments. The tool path 24 provides that the transition area 42 is the last to be approached by the tool 18. Due to the space gained by the targeted recess of the edge areas 38, 40, comparatively extensive movements can be carried out, for example, to approach or depart from the path area 30. For example, approach / departure segments with only a slight curvature can be used, as is the case in Fig. 11 illustrated, or long, circular arc-shaped path segments, as shown in Fig. 12This results in smooth tool movements, which reduces machine inaccuracies, prevents milling marks, and avoids undesirably large material penetration. In the illustrated cases, straight connecting segments are used between the path segments 36. In other embodiments, curved connecting segments can be used, which define smooth movements and / or along which an intermediate lift-off can occur.

[0060] Fig. 13illustrates a further modification in which the path segments 44 (shown in dashed lines) of the transition region 42 (illustrated by dash-dotted lines) overlap the path segments 32, 36 of the first path region 30 and the second path region 34. As can be seen, the transition region 42 thus projects beyond the edge regions 38, 40. In addition, the path segments 44 of the transition region 42 can be selected such that they are gradually lifted off the workpiece 14 towards the edge of the transition region 42. In the case shown, the lifting occurs outside the edge regions 38, 40. The transition region 42 thus enables grinding in the edge region of the transition region 42, whereby marks in the material created during machining according to the first path region 30 and / or the second path region 34 can be removed / ground.

[0061] The tool path 24 can provide that the transition region 42 is the last region approached by the tool 18. The transition region 42 thus enables grinding in the edge region of the transition region 42, whereby marks in the material created during machining according to the first path region 30 and / or the second path region 34 can be removed / ground.

[0062] In the Figures 14 to 16 another machining situation for another workpiece 14' is shown. For ease of understanding, the same reference numerals as above are used, whereby these are Figures 14 to 16 are each preceded by an apostrophe. Generally, reference can be made to the above description of the corresponding objects / elements.

[0063] The further workpiece 14' comprises a first workpiece section 26', which comprises a conical section of the workpiece 14' and a steep portion of a saddle-shaped section of the further workpiece 14' arranged below the conical section. Furthermore, the further workpiece 14' comprises a second workpiece section 28', which comprises a flat portion of the saddle-shaped section. The workpiece sections 26', 28' can be obtained as described above by comparison with a critical angle. Fig. 16 It is clearly visible how such a categorization results in a boundary between the workpiece sections 26', 28', which is located within a contiguous area of ​​the workpiece 14'.

[0064] Analogous to the example described above, a first path area 30' and a second path area 34' are determined by deliberately removing edge areas 38', 40' and using different adaptation strategies. A transition area 42' is determined such that the path segments 32', 36', 44' of the path areas 30', 34' and the transition area 42' together completely cover the two workpiece sections 28', 30' or define / effect their complete processing. As in Fig. 16 As can be seen, the spiral filling paths of the transition region 42' on a rear side of the workpiece 14' are not completely circumferential, since the steep first workpiece section 26' runs continuously from top to bottom.

[0065] Depending on the application, it may be appropriate to use the described procedure only if the workpiece geometry defines surfaces and transitions that would otherwise be difficult to machine with sufficient quality. Figures 17 and 18 For the sake of simplicity, the reference symbols used above for corresponding objects are used again, distinguished by two or three apostrophes. The solid line illustrates the workpiece contour, the dotted line represents the material still to be removed, and the dashed line represents the milling path along which the tool moves. In the example of a ball-end milling cutter, the sphere center of the tool moves along this milling path.

[0066] The workpiece 14" according to Fig. 17comprises a connecting section 46" between sections 27", 29" of a workpiece surface. The connecting section 46" is concavely curved and has a radius of curvature rk" that is considerably larger than a radius rw" of the tool 18". It is therefore readily possible to machine the workpiece without using a transition area, without machining marks forming in an area of ​​the connecting section 46". As can be seen, the wrap of the tool 18" is acceptable.

[0067] In contrast, the workpiece 14‴ according to Fig. 18a connecting section 46‴ with a significantly stronger curvature, which can be described by a curvature radius rk‴ that roughly corresponds to a tool radius rw‴. Wrapping of the tool 18‴ in an area of ​​the connecting section 46‴ would be very large, as evidenced by the large amount of material engagement (see dotted line). The resulting large amount of material engagement could lead to reduced machining quality.

[0068] The method can therefore comprise comparing a geometric parameter of the tool 18" / 18‴ with a geometric parameter of the workpiece 14" / 14"', in this case the connecting section 46" / 46"'. In the case illustrated by way of example, a radius of curvature of the connecting section 46" / 46‴ is compared with the tool radius rw" / rw‴. A threshold value specified by a user is also expediently taken into account, which, for example, represents a pre-factor for the comparison. If the radius of curvature is less than or equal to the threshold value multiplied by the tool radius rw" / rw‴, it is concluded that one of the Fig. 18A corresponding situation exists and the definition of a transition area is required. This is where the targeted release of edge areas and the overlay of a transition area described above come into play. For example, the user can specify that the process is used if the curvature radius rw" of the connecting section 46" is smaller than twice or one and a half times the tool radius rw".

[0069] Otherwise, the definition of a transition area can be omitted (compare, for example, the case according to Fig. 17 ). The geometric parameters considered then differ so significantly that no quality problems are to be expected during processing.

[0070] If a ball nose cutter or any other tool with a curved cutting edge is used instead of a ball nose cutter, the comparison described can be made on the basis of a geometric parameter describing the cutting edge of the tool instead of or in addition to the tool radius.

[0071] A schematic flow diagram of a method for determining a tool path for material-removing machining of a workpiece is shown in Fig. 19 As an optional step S0, the method may comprise comparing a geometric parameter of the workpiece with a geometric parameter of the tool, as exemplified above with reference to Figures 16 and 17described. If the comparison shows that defining a transition area is not necessary, the workpiece is machined across an existing connecting section in step S10. If, however, the comparison shows that subdividing the workpiece is appropriate, the process is carried out with the targeted recessing of the edge areas.

[0072] In step S1, different workpiece sections can be determined. This can be done, for example, using the described comparison of surface normals with a.

[0073] In a step S2, a first path region of a tool path is determined such that path segments of the first path region cover a first workpiece section except for a first edge region.

[0074] In a step S3, a second path region of the tool path is determined such that path segments of the second path region cover a second workpiece section except for a second edge region.

[0075] In a step S4, a transition region of the tool path is determined which covers the first edge region and the second edge region, wherein path segments of the transition region together with the path segments of the first and second path regions completely cover the workpiece section.

[0076] As described above, steps S2 and / or S3 may comprise shortening preliminary path segments and / or determining path segments based on taking into account a tool radius that is increased compared to an actual tool radius.

[0077] The tool path determined in such a process can be used in a process described by the schematic flow diagram of the Fig. 20In a step S21, a machining path is determined. This is done in a method according to Fig. 19 . In a step S22, a workpiece is machined by means of a tool which is guided along the specific tool path for machining.

Claims

1. A method for determining a tool path (24) for material-removing machining of a workpiece (14) in a machine tool (10), in particular in, for example, a five-axis CNC machine, by moving a tool (18), in particular a milling tool, along the tool path (24), wherein the workpiece (14) comprises a first workpiece portion (26) and a second workpiece portion (28) adjacent to the first workpiece portion (26), wherein the tool path (24) comprises a first path section (30) for machining the first workpiece portion (26), comprising path segments (32) adapted to a geometry of the first workpiece portion (26) by means of a first adaptation strategy, and wherein the tool path (24) comprises a second path section (34) for machining the second workpiece portion (28), comprising path segments (36) adapted to a geometry of the second workpiece portion (28) by means of a second adaptation strategy that is different from the first adaptation strategy, comprising: determining the first path section (30) in such a way that the path segments (32) of the first path section (30) cover the first workpiece portion (26) except for a first edge section (38) that is specifically omitted by the path segments (32) of the first path section (30) although path segments would be adaptable to the first edge section (38) by means of the first adaptation strategy; determining the second path section (34) in such a way that the path segments (36) of the second path section (34) cover the second workpiece portion (26) except for a second edge section (40) that is specifically omitted by the path segments (36) of the second path section (34) although path segments would be adaptable to the second edge section (40) by means of the second adaptation strategy; and determining a transition section (42) of the tool path (24), comprising path segments (44) covering the first edge section (38) and the second edge section (40), wherein the path segments (32, 36, 44) of the first path section (30), the second path section (34) and the transition section (42) collectively cover the entire first workpiece portion (26) and the entire second workpiece portion (28), wherein the first workpiece portion (24) is a steep portion relative to a spatial axis (z), the surface normals (n) of which are inclined by more than a first critical angle relative to the spatial axis (z) at contact points and / or touch points of the tool (18), and the second workpiece portion (28) is a flat portion, the surface normals (n') of which are inclined by less than a second critical angle relative to the spatial axis (z) at contact points and / or touch points of the tool (18), characterized in that the first adaptation strategy provides path segments that are plane-based such that machining in the first path section (30) is performed plane by plane, and the second adaptation strategy provides path segments that are projection-based such that the second path section (34) is based on a projection of a path pattern onto the second workpiece portion (28).

2. The method of claim 1, further comprising comparing at least one geometrical parameter, in particular a radius (rw), of the tool with a geometrical parameter, in particular a curvature radius (rk), describing a connecting portion (46) of the first workpiece portion (26) and of the second workpiece portion (28), wherein the comparison is based in particular on at least one threshold value that can be set by a user.

3. The method of any one of the preceding claims, further comprising: determining connecting segments (48) and / or approach segments (50) and / or move-along segments (52) that are at least partially included in the transition section (42) for the first path section (30) and / or for the second path section (34).

4. The method of any one of the preceding claims, wherein the transition section (42) is reached after the first path section (30) and the second path section (34) when the tool (18) is moved along the tool path (24).

5. The method of any one of the preceding claims, further comprising: determining the transition section (42) in such a way that its path segments (44) at least partially overlap the first path section (30) and / or the second path section (34), wherein the path segments (44) of the transition section (42) are determined in particular in such a way that they are gradually lifted from the workpiece (14) where they overlap the first path section (30) and / or the second path section (32).

6. The method of any one of the preceding claims, further comprising: determining the path segments (44) of the transition section (42) in such a way that they describe a spiral filling path for the transition section (42).

7. The method of any one of the preceding claims, further comprising: determining the first path section (30) by determining preliminary path segments (54) based on coverage of the entire first workpiece portion (26) using the first adaptation strategy and subsequent shortening the preliminary path segments (54) in the first edge section (38); and / or determining the second path section (34) by determining preliminary path segments (54) based on coverage of the entire second workpiece portion (28) using the second adaptation strategy and subsequent shortening the preliminary path segments (54) in the second edge section (40).

8. The method of claim 7, wherein the shortening of the preliminary path segments (54) is based on at least one boundary curve (56) that is superimposed on the first workpiece portion (26) and / or the second workpiece portion (28).

9. The method of any one of the preceding claims, wherein the tool (18) has an actual tool radius (rw) that is taken into account when determining the tool path (24), and wherein the determination of the transition section (42) is based on at least one tool radius (rv) that is larger than the actual tool radius (rw).

10. The method of claim 9, wherein starting points and / or end points of path segments (32) of the first path section (30) defining the first edge section (38) are determined by determining how far the tool (18) can be moved towards the second workpiece portion (28) during machining of the first workpiece portion (26), taking into account the at least one increased tool radius (rv); and / or wherein starting points and / or end points of path segments (36) of the second path section (34) defining the second edge section (40) are determined by determining how far the tool (18) can be moved towards the first workpiece portion (26) during machining of the second workpiece portion (28), taking into account the at least one increased tool radius (rv).

11. A computer program configured to implement a method of any one of the preceding claims.

12. A computer program product comprising at least one storage medium (58) on which program code of a computer program of claim 11 is stored.

13. A method for material-removing machining of a workpiece (14) using a tool (18) that is guided for machining along a tool path (24) determined using a method of any one of claims 1 to 10.