Method for generating metal cutting tool path cycles - Patents.com

Abstract

A computer-implemented method for generating a tool path cycle for removing material (12) from a blank using a turning tool (1), the turning tool (1) having first and second cutting edges (2, 3) connected by a convex nose cutting edge (4) such that a predefined target shape (5) is formed, the method comprising the steps of receiving an input of a blank shape (10), receiving an input of the target shape (5), setting an offset distance (m), receiving an input of the turning tool (1), setting a first cutting direction (25) and a second cutting direction (26), and dividing a first layer (11) into segments (16, 17, 18) separated by boundaries (19, 20). 20. The method of claim 19, further comprising: dividing a first layer into segments, such that one longitudinal set of segments (11, 18, 43) is adjacent to a longitudinal portion (9, 21, 39) and one radial set of segments (17, 42, 44) is adjacent to a radial portion (8, 38, 40); removing the longitudinal set of segments (11, 18, 43) followed by the radial set of segments (17, 42, 44) when a first cutting direction (25) is along a Z-axis; and removing the radial set of segments (17, 42, 44) followed by the longitudinal set of segments (11, 18, 43) when the first cutting direction (25) is along an X-axis.

Description

[Technical field]

[0001] The present invention is in the field of metal cutting, and more particularly in the field of computer-implemented methods for generating tool path cycles. [Background technology]

[0002] The present invention refers to a method according to the preamble of claim 1. In other words, the present invention relates to a computer implemented method for generating toolpath cycles for removing stock from a blank using a turning tool, the turning tool comprising first and second cutting edges connected by a convex nose cutting edge such that a predefined target shape is formed, the blank is rotatable about an axis of rotation represented by the Z axis, the X axis being orthogonal to the Z axis and representing a radial direction, the target shape comprises a plurality of portions, the plurality of portions comprising one or more convex portions and one or more concave portions, at least one radial portion extending further along the X axis than the Z axis and at least one longitudinal portion extending further along the Z axis than the X axis, one or more of said concave portions of the target shape comprising an arcuate portion having a radius of curvature equal to or greater than the radius of curvature of the nose cutting edge, said arcuate portion connecting one radial portion and one longitudinal portion, the method comprising the steps of receiving an input of the blank shape and receiving an input of the target shape.

[0003] In metal cutting, turning is a common operation. CNC lathes are commonly used. Complex shapes are usually machined from a metal workpiece, also known as a blank. It is clamped and material is removed with the turning tool until the target shape is formed. The material removed from the blank is commonly known as the stock. In turning, manual instructions on how the metal cutting operation should be performed are common. The manual instructions include how and in what order different passes are to be performed. A pass is where you enter the cut to where you leave the cut. Manual instructions can range from very efficient to low efficiency in terms of parameters such as machining time, tool life, surface finish, and other factors. If it is a very skilled person giving the instructions to the CNC tool or if a lot of trial and error experiments are performed, the instructions can result in very efficient machining. However, in some cases, the toolpath cycles need to be generated automatically or semi-automatically. For example, ideally, such an automatic or semi-automatic toolpath generation method would be able to achieve good performance, e.g., in terms of machining time and tool life, for a wide range of metal cutting operations, e.g., blank and target shape variations, and would take significantly less time than manual programming.

[0004] EP 3 702 853 A1 discloses a method for generating control command data for a turning operation. Although such a method gives good results, the inventors have found that there is a need for further improvement. Summary of the Invention

[0005] One object of the present invention is to provide an improved computer-implemented method for generating toolpath cycles that increases tool life.

[0006] This object is achieved by a method as defined at the outset, the method comprising the further steps of setting an offset distance, receiving a turning tool input, setting a first cutting direction and a second cutting direction, one of the first and second cutting directions representing a direction of movement of the turning tool along an X-axis and one of the first and second cutting directions representing a direction of movement of the turning tool along a Z-axis, and a further step of generating a first layer completely or partially in the blank, the first layer being formed by a cutting operation performed by the ... a further step of generating a first layer, the first layer being bounded by the target shape and an outer boundary of the first layer, the outer boundary of the first layer being spaced from the target shape by an offset distance, the outer boundary of the first layer comprising one or more convex portions and one or more concave portions; and a further step of placing a boundary line parallel to the Z axis and parallel to the X axis, the boundary line each extending between the target shape and the outer boundary of the first layer and intersecting either a concave portion of the outer boundary of the first layer or a convex portion of the target shape. a further step of dividing the first layer into segments separated by boundary lines, one longitudinal segment adjacent to each longitudinal portion and one radial segment adjacent to each radial portion, and one boundary line arranged to separate the radial and longitudinal segments such that an arcuate portion borders one of said radial and longitudinal segments by said boundary line intersecting a concave portion of the outer boundary of the first layer, and a further step of removing all segments such that after a segment adjacent to said one segment, said one segment bordering an arcuate portion is removed, wherein when removing one or more longitudinal segments, the turning tool (1) is moved in one direction along the Z axis, and when removing one or more radial segments, the turning tool (1) is moved in one direction along the X axis, and said directions along the X and Z axes are both either both towards the concave portion or both away from the concave portion.and the further step of removing all segments.

[0007] The inventors have found that machining a concave portion without prior removal of any material adjacent said portion increases the risk of insert breakage, and this method reduces the risk of insert breakage. The increased risk may be due to an excessive cutting depth and / or an increased risk of chip hammering. In particular, the inventors have found that turning towards an internal shoulder or a concave portion without prior removal of material adjacent said portion increases the risk of insert breakage. It has been found that this problem is reduced by a method in which one or more layers substantially following the shape of the target shape are divided into segments, such that the boundaries separating adjacent segments are spaced apart from the midpoint of the concave portion.

[0008] Such a method allows tool paths to be generated based on a limited number of input data for turned components with a wide variety of geometries, and allows machining to be performed efficiently, e.g., in terms of tool life and / or cycle time and / or surface finish.

[0009] The computer implemented method is for generating a toolpath cycle or cutting cycle, such as generating instructions for controlling a CNC lathe. The toolpath is for controlling the movement of a turning tool relative to a workpiece or blank, such as the feed direction and the sequence of passes. The turning tool is suitable for removing material from the blank. The turning tool 1 comprises first and second cutting edges, connected by a convex surface generating a nose cutting edge. The nose cutting edge is preferably arcuate in top view, for example having a radius of curvature of 0.1-1.6 mm. The first and second cutting edges are at least partially linear in top view, and preferably form an acute angle, in top view, of preferably 15-85°, even more preferably 25-83°.

[0010] When the first cutting direction is set parallel to the X-axis, the nose angle is preferably not more than 50°, or when the shape of the first and second cutting edges is not straight in top view, the angle between the active parts of the first or second cutting edges relative to the bisector is not more than 25°, in order to reduce the risk of chip jamming when machining the concave parts.

[0011] The bisector between the first and second cutting edges preferably forms an angle of 40° to 50°, even more preferably 45°, with the Z-axis.

[0012] The toolpath cycle is for forming a predefined target shape through metal cutting. The blank extends longitudinally or axially along the Z axis and radially along the X axis. The Z axis represents the axis of rotation about which the blank can be rotated. The X axis is orthogonal to the Z axis. The blank or blank shape is represented in the XZ plane by a continuous line extending between the first and second blank endpoints.

[0013] The target shape is represented in the XZ plane by a continuous line extending between the first and second target end points, and comprises a set of portions, i.e. sub-portions, that are connected and jointly form the target shape. The portions may be linear or curved. The linear portion extends between two ends. The ends are end points of the target shape or where the target shape deviates from the linearity of the linear portion. The arcuate portion has its own radius of curvature and extends between the end points or where the target shape deviates from said curvature, such as a linear portion or a portion with a different radius of curvature.

[0014] The normal of a point of the arcuate portion forms an angle of 45° with the Z axis. If the arcuate portion connects one longitudinal portion parallel to the Z axis and one radial portion parallel to the X axis, then the point is the midpoint of the arcuate portion.

[0015] The set of portions comprises one or more convex portions, or corners, points, or sections, and one or more concave portions. The target shape may comprise at least two, at least three, at least four, or at least five convex and / or concave portions.

[0016] The set of sections further comprises at least one radial section extending further along the X-axis than the Z-axis. The radial section is inclined at an angle of more than 45° with respect to the Z-axis. The radial section may, for example, be linear and parallel to the X-axis. For all points of the radial section, the normal forms an angle of less than 45° with respect to the Z-axis. The set of sections further comprises at least one longitudinal section extending further along the Z-axis than the X-axis. The longitudinal section may, for example, be linear and parallel to the Z-axis. The longitudinal section is inclined at an angle of less than 45° with respect to the Z-axis. For all points of the longitudinal section, the normal forms an angle of more than 45° with respect to the Z-axis.

[0017] For radial segments, the distance between the end points of the segment is greater along the X-axis than along the Z-axis, and the opposite is true for longitudinal segments. The end points are part of the target shape.

[0018] The target shape does not include any concave portions having a radius of curvature less than the radius of curvature of the nose edge. At least one of the concave portions is in the form of an arc portion having a radius of curvature equal to or greater than the radius of curvature of the nose edge. The arc is preferably a circular arc.

[0019] The target shape is such that each point of the target shape in the XZ plane is within line of sight of at least one point in the XZ plane, in other words, each point of the target shape in the XZ plane faces one point in the XZ plane.

[0020] The method includes receiving an input of a blank or starting shape, receiving an input of a target shape, setting an input of an offset distance, i.e., an offset distance function, and setting a first cut direction and a second cut direction. The stock or material to be removed is defined as the difference between the blank shape and the target shape. The input may be in the form of a user input. Alternatively, the input received regarding the blank shape may be in the form of measurement data from a measuring device. The input received regarding the target shape may be in the form of data from a database of one or more drawings. The offset distance or offset distance function may be set manually, for example, from a user input, from a preset value or function from a computer program, or from a database containing cutting data recommendations. The offset distance may be set from a number of parameters based on which the offset distance is calculated. The first and second cut directions are along the X and Z axes and may be selected through user input or may be selected based on parameters such as turning tool characteristics and / or the target shape.

[0021] The method may include receiving a turning tool input, for example through receiving a user input of a turning tool such that characteristics of a turning tool suitable for turning the blank to form the selected target shape are selected. The turning tool may be selected from a tool database, may be selected by a user, or may be set based on parameters such as the target shape, the first cutting direction, and the second cutting direction.

[0022] The blank shape and the target shape are symmetric about the Z axis, which represents the axis of rotation of the blank. The shapes are in the form of representations in the XZ plane.

[0023] The method includes generating or disposing a first layer or a first layer shape completely or partially within the material. The first layer is bounded by a target shape that defines an inner boundary of the first layer and an outer boundary of the first layer that are vertically spaced apart from the target shape by an offset distance or an offset distance function. The first layer extends continuously between the first and second target endpoints. The offset distance is the vertical distance from the target shape to the outer boundary of the first layer. The offset distance may be a constant, i.e., a specific value, or a range, or a function. The outer boundary of the first layer is a cautious line in the XZ plane. The shape of the outer boundary of the first layer substantially corresponds to the shape of the target shape. This means that all or substantially all parts of the outer boundary of the first layer correspond to parts of the target shape. For example, the number of convex and concave portions is equal in the target shape and the outer boundary of the first layer. The shortest distance from each point of the outer boundary of the first layer to the target shape may be constant or may vary, but is preferably less than or equal to a predefined value.

[0024] The first layer is divided into segments that together form the first layer. The first layer is not machined in a single turning pass, and the segmentation of the first layer is to aid in setting the sequence and direction of machining the first layer, i.e., the material inside the first layer. The segments are separated or divided by a set of imaginary boundaries. Each of said boundaries is arranged either parallel to the Z axis or parallel to the X axis. All of the boundaries may be parallel to the X axis. Alternatively, all of the boundaries are parallel to the Z axis. Alternatively, at least one boundary is parallel to the X axis and at least one boundary is parallel to the Z axis. The boundaries extend between the target shape and an outer boundary of the first layer.

[0025] A longitudinal segment is adjacent to a longitudinal portion. If the target shape comprises more than one longitudinal portion, the target shape may comprise more than one longitudinal segment, at least if the longitudinal length, i.e., extension along the Z-axis, of the longitudinal portion is sufficiently long.

[0026] A radial segment is adjacent to a radial portion. If the target shape comprises more than one radial portion, the target shape may comprise more than one radial segment, at least if the radial length, i.e., extension along the X-axis, of the radial portion is sufficiently long.

[0027] The segmentation is such that the entire arc lies exactly within one segment.

[0028] The method includes the step of directing the turning tool to remove all the segments, more specifically the stock or material inside all the segments, through a number of passes equal to the number of segments, thus removing a segment means removing the part of the stock that is inside said segment.

[0029] The removal is configured to be accomplished with the nose edge and the first and / or second cutting edges.

[0030] The number of passes is equal to the number of radial and longitudinal segments.

[0031] The nose edge creates the machined surface, in other words, the nose edge moves along the target shape.

[0032] The depth of cut may vary when removing material in the first layer, and for at least one pass, i.e., when removing material in one segment, the first cutting edge is active and for at least one other pass, the second cutting edge is active, i.e., in cutting.

[0033] In this manner, all segments of the first layer are removed, i.e., all material within the first layer is removed, forming the target shape.

[0034] The concave or convex portion of the target shape or outer boundary of the first layer can be in the form of, for example, an arc of a circle or a sharp corner.

[0035] One radial set of segments is adjacent to a radial portion, in other words, each radial segment is adjacent to a radial portion, and only one radial segment may be adjacent to a single radial portion.

[0036] A boundary line is positioned such that the boundary line intersects a concave portion of the outer boundary of the first layer. Preferably, each concave portion of the outer boundary of the first layer is intersected by a boundary line and the boundary lines are parallel.

[0037] The radial and longitudinal segments, each of which comprises a portion adjacent to the concave portion, are separated by the one boundary line such that an arcuate portion borders one of the radial and longitudinal segments. If the one boundary line is parallel to the X-axis, the radial segment comprises the arcuate portion. If the one boundary line is parallel to the Z-axis, the longitudinal segment comprises the arcuate portion. The order of removing all the segments with the turning tool is such that the one segment bordering the arcuate portion is removed after the segment adjacent to the one segment. In other words, if the one boundary line is parallel to the Z-axis, the radial segments are removed before the longitudinal segments. If the one boundary line is parallel to the X-axis, the longitudinal segments are removed before the radial segments.

[0038] The removal of the segments is such that when removing a longitudinal segment or one or more longitudinal segments, i.e. when one of the first and second cutting edges is active, the turning tool is moved in one direction along the Z axis, and when removing one or more radial segments, i.e. when one of the first and second cutting edges is active, the turning tool is moved in one direction along the X axis.

[0039] The directions along the X-axis and Z-axis are both either both toward the concave portion or both away from the concave portion, such that if a first cutting edge is active when removing the longitudinal segment, a second cutting edge is active when removing the radial segment, or vice versa, such that the wear of the insert is more evenly distributed along the cutting edges.

[0040] According to one embodiment, the method includes the further steps of arranging one boundary line that intersects with a convex portion of the target shape parallel to the Z axis and one boundary line that intersects with a concave portion of the outer boundary of the first layer parallel to the X axis when the first cutting direction is along the X axis, arranging one boundary line that intersects with a convex portion of the target shape parallel to the X axis and one boundary line that intersects with a concave portion of the outer boundary of the first layer parallel to the Z axis when the first cutting direction is along the X axis, removing one or more longitudinal segments followed by one or more radial segments when the first cutting direction is along the Z axis, and removing one or more radial segments followed by one or more longitudinal segments when the first cutting direction is along the X axis.

[0041] With such a method, the user can select the cutting direction in both the longitudinal and radial directions. This is an advantage since the method can be used with a variety of turning tools. Some turning tools are suitable for machining only one radial and one longitudinal direction, while other turning tools can be used in the opposite longitudinal and radial directions. Depending on the turning tool, the cutting direction can be different in order to maximize the tool life.

[0042] Such a method allows the target shape to be produced in fewer passes, thus reducing the number of cusps, while still maintaining an acceptable surface finish.

[0043] The arrangement of the boundary lines depends on the selected first cutting direction. If the set first cutting direction is along the Z axis, the boundary lines parallel to the Z axis are arranged so that the boundary lines intersect with the convex parts of the target shape. If the target shape has two or more convex parts, each convex part intersects with one boundary line parallel to the Z axis. Thus, the number of boundary lines is equal to the number of convex parts. Furthermore, if the set first cutting direction is along the Z axis, one boundary line parallel to the X axis is arranged so that it intersects with the concave parts of the outer boundary of the first layer and with one longitudinal part of the target shape. If the outer boundary of the first layer has two or more concave parts, all of the concave parts intersect with one boundary line parallel to the X axis.

[0044] If the first cutting direction is along the X-axis, then one boundary line is positioned such that the boundary line intersects with a convex portion of the target shape, the boundary line being parallel to the X-axis. Additionally, one boundary line is positioned such that the boundary line intersects with a concave portion and a radial portion of the outer boundary of the first layer, the boundary line being parallel to the Z-axis. If the outer boundary of the first layer includes two or more concave portions, then each of the portions intersects with a boundary line parallel to the Z-axis.

[0045] If the first cutting direction is along the Z axis, then the longitudinal segment or one or segments are first removed by moving the turning tool along the Z axis. Movement along the Z axis should be understood as a direction along the Z axis as set by the first cutting direction, with one component of the movement direction being along the Z axis. After all longitudinal segments have been removed, all radial segments are removed by moving the turning tool along the X axis, with one component of the movement direction being in the second cutting direction.

[0046] If the first cutting direction is along the X-axis, then all radial segments are removed before the longitudinal segments. The direction of movement of the turning tool is as described above, i.e. along the X-axis for the radial segments and along the Z-axis for the longitudinal segments.

[0047] Regardless of whether the first cutting direction is along the X-axis or the Z-axis, the first segment to be removed is preferably the segment adjacent to the first target endpoint or the second target endpoint.

[0048] The first cutting direction and the second cutting direction are both either both toward the concave portion or both away from the concave portion.

[0049] According to one embodiment, if the first cutting direction is along the Z axis, one or more longitudinal segments are removed by moving the turning tool in one direction along the Z axis, followed by one or more radial segments being removed by moving the turning tool in one direction along the X axis; if the first cutting direction is along the X axis, one or more radial segments are removed by moving the turning tool in one direction along the X axis, followed by one or more longitudinal segments being removed by moving the turning tool in one direction along the Z axis.

[0050] By such method, machining time can be kept relatively low since for each set of segments, the turning tool is moved in only one direction along the X-axis and Z-axis, respectively. Each set of segments refers here to a radial set of segments, i.e., one or more radial segments, and a longitudinal set of segments, i.e., one or more longitudinal segments. In this way, the air movements or rapid traverse time of the cutting tool, i.e., the time of the movement of the turning tool between passes, can be kept relatively low.

[0051] According to one embodiment, both the first cutting direction and the second cutting direction are either both towards the concave portion or both away from the concave portion.

[0052] In this way, the wear is spread over a longer portion of the cutting edge - more precisely, both the first and second cutting edges are worn - thus increasing the tool life.

[0053] One or more radial segments are removed with the nose edge and the first cutting edge and one or more longitudinal segments are removed with the nose edge and the second cutting edge, or one or more longitudinal segments are removed with the nose edge and the first cutting edge and one or more radial segments are removed with the nose edge and the second cutting edge.

[0054] Preferably, both the first cutting direction and the second cutting direction are both in a direction away from the concave portion. In such a manner, wear on the nose cutting edge can be further reduced, thereby increasing tool life.

[0055] According to one embodiment, the radial portion is parallel to the X-axis and the longitudinal portion is parallel to the Z-axis, and one of the radial portion and the longitudinal portion is formed in a single pass.

[0056] The radial portion of the target shape is parallel to the X-axis and the longitudinal portion of the target shape is parallel to the Z-axis, thus forming a 90° included angle.

[0057] One of the first portion and the longitudinal portion adjacent the concave portion in the form of an arcuate portion is formed in a single pass. If the first cutting direction is parallel to the X-axis, the longitudinal portion is formed in a single pass. If the first cutting direction is parallel to the Z-axis, the radial portion is formed in a single pass.

[0058] Such a method results in an improved surface finish. Either the first portion or the longitudinal portion of the target shape is entirely formed in a single pass. The first portion and the longitudinal portion each extend parallel to either the X-axis or Z-axis until the target shape deviates from parallelism to one of the axes or until the target shape is terminated.

[0059] According to one embodiment, the target shape comprises a further longitudinal portion, the further longitudinal portion and the radial portion being connected by a convex portion in the form of an arcuate portion, and a third segment being bounded by the further longitudinal portion.

[0060] The third segment is bounded by or adjacent to a further longitudinal portion. The turning tool moves in the same direction along the Z axis when removing the longitudinal segments, said longitudinal segments being removed one after the other in succession. A radial segment is removed after or before both of said longitudinal segments.

[0061] The further longitudinal portion may, for example, be parallel to the longitudinal portion and at a different distance, for example a greater distance, from the Z axis.

[0062] Such a method reduces cycle time by minimizing movement of the turning tool along the Z axis during removal of the first and second segments.

[0063] According to one embodiment, the method includes the further step of receiving an input of one parameter or two parameters representing an offset distance in the X direction and an offset distance in the Z direction.

[0064] The input may be in the form of, for example, a user input or may be input from a digital tool database in which the one or more parameters for turning tools are stored. The offset distance may be set as a function of both the turning tool and the cutting direction. For example, the offset distance may have different values ​​depending on which direction along the Z axis the first cutting direction is oriented for a particular turning tool.

[0065] The parameters for setting the offset distance include an offset x value, ie, the offset distance along the X-axis, and an offset z value, ie, the offset distance along the Z-axis.

[0066] One parameter, i.e. one value, may represent the offset distance in both X and Z directions. In other words, said offset distances are equal. Alternatively, said offset distances are not equal and thus two different values ​​are set. Said values ​​are preferably in the range of 0.2-8.0 mm, even more preferably 0.5-5.0 mm.

[0067] By such a method, the cutting depth can be selected to suit turning tools that are not symmetrical, for example inserts that do not have a bisector between the first and second cutting edges that form a 45° angle with respect to the Z axis, or that are not equally suitable for radial and longitudinal turning.

[0068] According to one embodiment, the convex portion connects a radial portion parallel to the X-axis and a further longitudinal portion parallel to the Z-axis, the radial portion of the outer boundary of the first layer being parallel to the radial portion and spaced apart by an offset distance in the Z-direction, the longitudinal portion of the outer boundary of the first layer being parallel to the further longitudinal portion and spaced apart by an offset distance in the X-direction, the first portion and the longitudinal portion of the outer boundary of the first layer intersecting at a convex portion of the outer boundary of the first layer, said convex portion being in the form of a 90° angle.

[0069] The method preferably includes the above mentioned steps only if or when the radius of curvature of the convex portion of the target shape is less than a predefined value, said predefined value preferably being within the range of 0.4-3.0 mm.

[0070] The method may preferably include the step of setting a predefined maximum cutting depth value, said value may be set manually, i.e., entered by a user, or may be set automatically from a database containing maximum cutting depth values ​​for the cutting tool. A boundary line. A perpendicular distance from a boundary line that intersects with a convex portion of the target shape to an outer boundary of the first layer is set to be less than or equal to said maximum cutting depth value.

[0071] The outer boundary of the first layer comprises a radial portion that is parallel to the X-axis. The radial portion of the outer boundary of the first layer is parallel to a portion of the radial portion of the target shape and is spaced apart in the Z direction by an offset distance.

[0072] The convex portion of the outer boundary of the first layer is in the form of an exact 90° corner, i.e. a corner with no curvature, said corner connecting portions of the outer boundary of the first layer, said portions being parallel to the X-axis and the Z-axis, respectively.

[0073] According to one embodiment, the method comprises the step of setting a split angle and the further step of positioning a boundary line intersecting the convex portion from a point of said convex portion, the boundary line having a normal that forms an angle with the Z axis equal to the split angle.

[0074] Thus, the method includes a step of setting the split angle, for example by receiving an input from a user, which is the split angle. Alternatively, said angle can be set to a default value, preferably 45°. Alternatively, said angle may be calculated from parameters.

[0075] Such a method allows for a controlled selection of segmentation around or near the concave portion.

[0076] The division angle is preferably set to 45°. In such a case, if the first cutting direction 25 is along the Z axis, the longitudinal portions form at each point an angle with the Z axis that is less than or equal to 45°. In such a case, if the first cutting direction 25 is along the X axis, the radial portions form at each point an angle with the Z axis that is more than or equal to 45°.

[0077] According to one embodiment, the method includes the further step of setting the division angle equal to arctan(Ox / Oz).

[0078] Thus, the split angle is set equal to the arctan of the X-direction offset distance divided by the Z-direction offset distance.

[0079] In this way, each segment adjacent the concave portion has a more uniform thickness, reducing the risk that the cut depth will exceed the offset distance.

[0080] According to one embodiment, the method comprises the further step of calculating an offset distance from said parameters Ox, Oz representing the offset distance in the X and Z directions, and positioning an outer boundary of the first layer vertically spaced apart from the target shape by an offset distance; The offset distance m is calculated according to the following formula: m = ((90-β)·Ox+β·Oz) / 90 where angle β is the angle that the target shape makes with the Z axis.

[0081] The angles are expressed in degrees and are the angles that each point of the target shape makes with the Z axis.

[0082] Such a method allows the distance to the outer boundary of the first layer to be calculated for turning tools having different characteristics for radial and longitudinal turning, even for target shapes with more complex shapes, such as target shapes with tapered portions.

[0083] According to one embodiment, the method comprises the further step of generating vertical auxiliary lines from a point of each concave portion of the target shape forming a normal at an angle equal to the splitting angle with respect to the Z axis, the further step of positioning one or more boundary lines intersecting with the convex portion of the target shape such that said boundary lines intersect with said points, and the further step of positioning one or more boundary lines intersecting with the concave portion of the outer boundary of the first layer such that said boundary lines each intersect with an intersection point of one of the auxiliary lines with the outer boundary of the first layer.

[0084] The split angle is preferably equal to arctan(Ox / Oz).

[0085] According to one embodiment, the method includes the further step of immediately or substantially immediately after all material has been removed in each segment at the feed rate, moving the turning tool to a subsequent segment at a speed faster than said feed rate.

[0086] Removal of a segment is accomplished by moving the nose cutting edge of the turning tool along the inner boundary of the segment, i.e., along the target shape for the first layer. The movement is by what is called the feed, which is usually set to a specified distance per revolution of the workpiece, usually in the range of 0.05 to 8.0 mm per revolution. Immediately or substantially immediately after removing each segment, the turning tool is moved away from the inner boundary of the segment at a rate faster than the feed rate toward the start of the succeeding segment. Such rapid movements are also known as air moves or rapid traverses.

[0087] Such removal of the turning tool is preferably, for the second or higher layers, immediately or substantially immediately after all material within said segment has been removed, where immediately should be understood as less than 3 seconds, preferably less than 2 seconds, after all material within said segment has been removed.

[0088] Such a method reduces cycle times.

[0089] According to one embodiment, the method includes a further step of positioning the turning tool such that the first cutting edge forms a constant angle with respect to the Z-axis when all the segments are removed, the turning tool comprising a tool body and a turning insert, the tool body extending along its longitudinal axis extending between a front end and a rear end, the rear end being connected to a machine interface of a CNC lathe, the turning insert being connected to the front end of the tool body, the longitudinal axis being arranged parallel to the X-axis.

[0090] The turning tool is preferably selected such that a bisector extending halfway between the first and second cutting edges forms an angle of 45° with respect to the Z axis.

[0091] According to one embodiment, the method includes the further step of setting the turning tool before setting the first and second cutting directions, and the further step of setting the first and second cutting directions towards the one or more concave portions if the nose angle of the turning tool is greater than 60° and the first and second cutting edges each have a length in a top view that exceeds the offset distance.

[0092] In this manner, the risk of insert breakage is further reduced. The inventors have found that turning into a concave portion, particularly into a 90° re-entrant angle, increases the risk of insert breakage for turning inserts with relatively large nose angles, such as inserts of type CNMG having an 80° nose angle.

[0093] In top view, the first and second cutting edges each have a length that is greater than the offset distance, alternatively greater than 5 mm, and even more preferably greater than 7 mm.

[0094] The nose angle is defined as the angle between the first and second cutting edges in a top view.The turning tool preferably comprises a turning insert.

[0095] According to one embodiment, the method includes the further step of setting the first and second cutting directions before setting the turning tool, and when one or both of the first and second cutting directions are set away from the one or more concave portions, the further step of setting the turning tool such that a nose angle of the turning tool forms an angle of more than 60° or the turning tool has third and fourth cutting edges that form an angle therebetween of 60° or less, wherein the third and fourth cutting edges are spaced from the nose edge by a distance less than the offset distance.

[0096] The inventors have found that for turning inserts having relatively large nose angles, such as Type CNMG inserts having an 80° nose angle, when cutting away from the concave portion, there is an increased risk of insert breakage, and that this risk is reduced by any of the turning tools described above.

[0097] The nose angle is defined as the angle between the first and second cutting edges in a top view. The turning tool preferably comprises a turning insert. The second mentioned turning tool may preferably comprise a turning insert with a nose cutting edge connecting the first and second cutting edges, the first and second cutting edges forming a nose angle of 70-85°, the first cutting edge being between the nose cutting edge and the third cutting edge, the second cutting edge being between the nose cutting edge and the fourth cutting edge, the third and fourth cutting edges forming an angle of less than 50°. A portion of the third cutting edge and a portion of the fourth cutting edge are spaced apart from the nose cutting edge by a distance less than the offset distance or by a distance less than 6 mm, preferably less than 5 mm.

[0098] According to one embodiment, the method comprises the further step of generating one or more further layers further away from the target shape if the blank shape is at least partially outside the outer boundary of the first layer until all generated layers are completely spaced from the material, each further layer being defined by an inner boundary and an outer boundary, and for each further layer, the respective outer boundary being spaced from the respective inner boundary by an offset distance; the further step of dividing each further layer into a set of segments separated by boundary lines, each said set of segments corresponding to a set of segments of the first layer and each said boundary line corresponding to a boundary line of the first layer; and the further step of instructing the turning tool to remove all segments containing material from the top layer, followed by removing all segments containing material from each subsequent layer, until only the first layer remains.

[0099] The shape of the outer boundary of the one or more further layers corresponds or substantially corresponds to the shape of the outer boundary of the first layer, and the outer boundary of the one or more further layers comprises an equal number of convex and concave portions as the outer boundary of the first layer.

[0100] Each of the further layers is at least partially within the material.

[0101] The outer boundary of a lower layer is the same as, i.e. corresponds to, or coincides with, the inner boundary of the next higher layer. The outer boundary of the higher layer is spaced apart from the outer boundary of the lower layer.

[0102] The boundary lines of the one or more further layers are drawn or generated in a manner corresponding to the boundary lines of the first layer. Thus, if the first cutting direction is along the Z axis, the boundary line or lines intersecting the one or more convex portions of the inner boundary of the respective layer are arranged parallel to the Z axis, and the boundary line or lines intersecting the one or more concave portions of the outer boundary of the respective layer are arranged parallel to the X axis. Alternatively, if the first cutting direction is along the X axis, the boundary line or lines intersecting the one or more convex portions of the inner boundary of the respective layer are arranged parallel to the X axis, and the boundary line or lines intersecting the one or more concave portions of the outer boundary of the respective layer are arranged parallel to the Z axis.

[0103] For each further layer, the order in which the segments containing material are removed corresponds to or substantially corresponds to the order in which the corresponding segments of the first layer are removed.

[0104] The removal of said segments of each further layer corresponds with that for the corresponding segments of the first layer relative to the direction of movement of the turning tool.

[0105] The segments containing material are removed in layer order, ie, all the segments of an outer layer are machined first, then all the segments of the second outer layer, and so on.

[0106] Each segment containing stock is removed by the turning tool in one pass, with the number of passes equal to the number of segments containing stock.

[0107] For at least some points on the target shape, the perpendicular distance from the target shape to the outer boundary of the second, third, etc. layer is a multiple of the perpendicular distance from the target shape to the outer boundary of the first layer. In other words, the layers have at least partially uniform thicknesses, the thicknesses of the layers being defined by the perpendicular distance between the inner and outer boundaries of the respective layers.

[0108] The offset distance or offset distance function is the same for all layers, ie calculated or set correspondingly.

[0109] According to one embodiment, there is provided a computer program product having instructions which, when executed by a computing device or system, cause the computing device or system to perform a method according to any one of the methods described above.

[0110] The present invention will now be described in more detail by way of a description of embodiments of the invention and with reference to the accompanying drawings. [Brief description of the drawings]

[0111] [Figure 1] FIG. 13 is a schematic diagram showing how a first layer is disposed partially within the material adjacent to the target shape. [Diagram 2] 2 is a schematic diagram illustrating an alternative first layer positioned adjacent to the target shape of FIG. 1. [Diagram 3] FIG. 2 is a schematic diagram showing how the first layer of FIG. 1 is divided into segments. [Figure 4] FIG. 2 is a schematic diagram illustrating an alternative segmentation in the first layer of FIG. 1. [Diagram 5] FIG. 3 is a schematic diagram showing how the first layer of FIG. 2 is divided into segments. [Figure 6] FIG. 3 is a schematic diagram illustrating an alternative segmentation in the first layer of FIG. 2. [Figure 7] 6 is a schematic diagram showing the steps in which the segment of FIG. 5 is removed using a turning tool. [Figure 8] 6 is a schematic diagram showing the steps in which the segment of FIG. 5 is removed using a turning tool. [Figure 9] 6 is a schematic diagram showing the steps in which the segment of FIG. 5 is removed using a turning tool. [Figure 10] 6 is a schematic diagram showing the steps in which the segment of FIG. 5 is removed using a turning tool. [Figure 11]6 is a schematic diagram showing the steps in which the segment of FIG. 5 is removed using a turning tool. [Figure 12] 6 is a schematic diagram showing the steps in which the segment of FIG. 5 is removed using a turning tool. [Figure 13] 6 is a schematic diagram illustrating an alternative sequence of steps for removing the segments of FIG. 5. [Figure 14] 6 is a schematic diagram illustrating an alternative sequence of steps for removing the segments of FIG. 5. [Figure 15] 6 is a schematic diagram illustrating an alternative sequence of steps for removing the segments of FIG. 5. [Figure 16] 6 is a schematic diagram illustrating an alternative sequence of steps for removing the segments of FIG. 5. [Figure 17] 6 is a schematic diagram illustrating an alternative sequence of steps for removing the segments of FIG. 5. [Figure 18] 6 is a schematic diagram illustrating an alternative sequence of steps for removing the segments of FIG. 5. [Figure 19] 7A-7C are schematic diagrams showing steps in which the segment of FIG. 6 is removed using a turning tool. [Figure 20] 7A-7C are schematic diagrams showing steps in which the segment of FIG. 6 is removed using a turning tool. [Figure 21] 7A-7C are schematic diagrams showing steps in which the segment of FIG. 6 is removed using a turning tool. [Figure 22] 7A-7C are schematic diagrams showing steps in which the segment of FIG. 6 is removed using a turning tool. [Figure 23] 7A-7C are schematic diagrams showing steps in which the segment of FIG. 6 is removed using a turning tool. [Figure 24] 7A-7C are schematic diagrams showing steps in which the segment of FIG. 6 is removed using a turning tool. [Diagram 25] 7 is a schematic diagram illustrating an alternative sequence of steps for removing the segments of FIG. 6; [Figure 26] 7 is a schematic diagram illustrating an alternative sequence of steps for removing the segments of FIG. 6; [Figure 27] 7 is a schematic diagram illustrating an alternative sequence of steps for removing the segments of FIG. 6; [Figure 28] 7 is a schematic diagram illustrating an alternative sequence of steps for removing the segments of FIG. 6; [Figure 29] 7 is a schematic diagram illustrating an alternative sequence of steps for removing the segments of FIG. 6; [Diagram 30] 7 is a schematic diagram illustrating an alternative sequence of steps for removing the segments of FIG. 6; [Diagram 31] 13A-13C are schematic diagrams illustrating how a first layer is disposed within a material adjacent to an alternative target shape. [Diagram 32] FIG. 32 is a schematic diagram showing the target shape of FIG. 31 with a second layer added. [Diagram 33] FIG. 32 is a schematic diagram showing the target shape of FIG. 31 with the first, second, and third layers segmented. [Diagram 34] FIG. 34 is a schematic diagram illustrating an alternative segmentation of the layers of FIG. 33. [Diagram 35] FIG. 32 is a schematic diagram illustrating how an alternative first layer is positioned adjacent to the target shape of FIG. 31. [Diagram 36] FIG. 36 is a schematic diagram showing how a second layer is added to FIG. 35. [Figure 37] FIG. 37 is a schematic diagram showing a third layer added to FIG. 36, in which the first, second, and third layers are segmented. [Figure 38] FIG. 38 is a schematic diagram illustrating an alternative segmentation of the layers of FIG. 37. [Figure 39] 13A-13C are schematic diagrams illustrating how a segmented first layer is disposed partially within the material adjacent further alternative target shapes; [Diagram 40] FIG. 40 is a schematic diagram illustrating an alternative segmentation of the first layer of FIG. 39. [Diagram 41] 2 is a schematic diagram showing the target shape of FIG. 1 and an alternative blank shape, in which the first and second layers are segmented. [Diagram 42] FIG. 42 is a schematic diagram illustrating an alternative segmentation of the layers of FIG. 41. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0112] Please refer to FIG. 1, which shows a turning tool 1 and a portion of a blank having a blank shape 10. The turning tool 1 is connected to a machine interface 51, which is part of a CNC lathe (not shown). A numerical control device (not shown) directs the movement of the turning tool 1 and the rotation of the blank about the rotation axis, thereby forming a target shape 5 by removing material 12. The blank shape 10, i.e. the outer boundary of the blank, and the target shape 5 are shown in the XZ plane, where the rotation axis of the blank is represented by the Z axis and the X axis represents the blank's radial direction, which is perpendicular to the Z axis. The target shape 5 extends continuously between first and second target endpoints 22, 23 and is formed by a number of portions 6, 7, 8, 9, 21. The target shape 5 comprises two longitudinal portions 9, 21 parallel to the Z axis, one radial portion 8 parallel to the X axis, one arcuate convex portion 6 and one arcuate concave portion 7. The arcuate portions 6, 7 are circular arcuate portions 6, 7. The turning tool 1 comprises a tool body and a turning insert 50. The turning insert is mounted in an insert seat formed in the tool body by a clamping means (not shown). The tool body extends along its longitudinal axis A1 extending between a front end and a rear end. The insert seat is formed at the front end and the rear end is connected to a machine interface 51. The longitudinal axis A1 is parallel to the X-axis. The turning insert 50 is shown in a top view and comprises first and second cutting edges 2, 3 connected by a convex nose cutting edge 4 having an arcuate portion, which is the surface that generates the cutting edge. The nose angle is defined as the angle between the first and second cutting edges 2, 3, said nose angle being an acute angle. The arcuate nose cutting edge 4 has a smaller radius of curvature than the arcuate concave portion 7. FIG. 1 shows an example of how a virtual first layer 11 is generated, extending between the target shape 5 and the outer boundary 13 of the first layer. The first layer 11 is partially within the blank 12. The area of ​​the blank 12 in the XZ plane is smaller than the corresponding area of ​​the first layer. The blank 12 does not extend outside the first layer 11. The outer boundary 13 of the first layer is spaced apart from the target shape 5 by an offset distance m. The offset distance m is less than or equal to the maximum cutting depth of the turning insert 50.The offset distance m is a constant value, i.e. the perpendicular distance from the target shape 5 to the outer boundary 13 of the first layer is a constant value. This means that the offset distance Ox in the X direction is equal to the offset distance Oz in the Z direction, which is equal to the offset distance m. Thus, the thickness of the first layer 11, measured perpendicularly from the target shape 5, is uniform. The outer boundary 13 of the first layer comprises one convex portion 14 corresponding to the convex portion 6 of the target shape 5 and one concave portion 15 in the form of a well-defined interior angle corresponding to the concave portion 7 of the target shape 5. The outer boundary 13 of the first layer further comprises a longitudinal portion parallel to and corresponding to the two longitudinal portions 9, 21 of the target shape 5 and one radial portion parallel thereto corresponding to the radial portion 8 of the target shape.

[0113] The turning tool 1 is shaped and oriented such that it can remove stock 12 to form a target feature 5. The target feature 5 is such that each point of the target feature 5 is within a line of sight from at least one point in the XZ plane, e.g., a point in an area representing the machine interface 51. In other words, each point of the target feature in the XZ plane faces one point in the XZ plane.

[0114] FIG. 2 differs from FIG. 1 in that the shape of the outer boundary 13 of the first layer is different and that the offset distance m is not constant. More specifically, the convex portion 14 of the outer boundary 13 of the first layer is in the form of an angle 14 of exactly 90°. Said angle 14 of 90° is formed by extending longitudinal and radial portions of the outer boundary 13 of the first layer, which correspond respectively to the longitudinal portion 21 and the radial portion 8 of the target shape 5. Said longitudinal portion 21 and radial portion 8 of the target shape 5 are separated by the convex portion 6 of the target shape 5. Said extension of the portion is linear. The offset distance m has a constant value except for the convex portion 6 of the target shape 5, where the offset distance m is longer, i.e. the offset distance is increased in the convex portion 6 of the target shape 5.

[0115] FIG. 3 shows an alternative example of segmentation of the first layer 11 in FIG. 1. More specifically, FIG. 3 shows the segmentation when the first cutting direction 25 is set along the Z-axis. The first layer 11 is divided into longitudinal 16, 18 and radial 17 segments. The first cutting direction 25 is set parallel to the Z-axis toward the right in FIG. 3, and the second cutting direction 26 is set parallel to the X-axis in an upward direction. The first cutting direction 25 determines whether the longitudinal segments 16, 18 should be removed before or after the radial segment 17. In FIG. 3, the first cutting direction 25 is set along the Z-axis, and the longitudinal segments 16, 18 are removed first.

[0116] Since the offset distance Ox in the X direction is equal to the offset distance Oz in the Z direction, the division angle α is set to 45°.

[0117] One auxiliary line 31 forms an angle with the Z axis equal to the split angle α. Said auxiliary line 31 extends perpendicularly from a point of the concave portion 7 of the target shape 5 to form a normal at 45°, i.e. equal to the split angle α, with respect to the Z axis.

[0118] The other second auxiliary line 32 is parallel to the first above-mentioned auxiliary line 31 and extends perpendicularly from a point of the convex portion 8 of the target shape 5 forming a normal at 45° to the Z-axis.

[0119] The segmentation is such that one boundary line 19 parallel to the X-axis is positioned such that said boundary line 19 intersects with the concave portion 15 of the outer boundary 13 of the first layer and intersects with one longitudinal portion 9 of the target shape 5. Said boundary line 19 is spaced from the midpoint of the concave portion 7. Said boundary line 19 intersects with the point where the auxiliary line 31 intersects with the outer boundary 13 of the first layer. Since the first cutting direction is along the Z-axis, the boundary line 19 that intersects with the concave portion 15 of the outer boundary 13 of the first layer is set to be parallel to the X-axis.

[0120] A second boundary line 20 extends between the target shape 5 and the outer boundary 13 of the first layer and extends parallel to the Z-axis. The boundary line 20 extends from the target shape 5 starting at the same point as the second auxiliary line 32. Since the first cutting direction is along the Z-axis, the second boundary line 20 extends parallel to the Z-axis.

[0121] Thus, the first layer 11 is divided into three segments 16, 17, 18 by boundary lines 19, 20, two segments 16, 18 are longitudinal segments and one segment 17 is a radial segment. Every other segment from the first target endpoint 22 to the second target endpoint 23 is a longitudinal segment 16, 18. The segmentation would be the same whether the first cutting direction 25 is towards the left or the second cutting direction 26 is downwards in the drawing.

[0122] Figure 4 shows the segmentation of the first layer 11 when the first cutting direction 25 is set to be along the X-axis. Thus, Figure 4 differs from Figure 3 in that the first cutting direction is along the X-axis, resulting in a different segmentation. The auxiliary lines 31, 32 are drawn similarly to Figure 3. The boundaries 19, 20 are drawn from the same points as in Figure 3. The boundary line 19, drawn from where the first auxiliary line 31 intersects with the outer boundary 13 of the first layer, is set to be parallel to the Z-axis. The boundary line 20, drawn from where the second auxiliary line 32 intersects with the target shape 5, is set to be parallel to the X-axis.

[0123] Figure 5 differs from Figure 3 only in that the thickness of the first layer 11 is not constant. Rather, an offset distance is set as in Figure 2. As in Figure 2, the outer boundary 13 of the first layer includes a convex angle 14 of exactly 90° formed by extending portions of the outer boundary 13 of the first layer that extend parallel to the X-axis and Z-axis, respectively. Boundary lines 19, 20 are drawn as in Figure 3, dividing the first layer 11 into three segments 16, 17, 18.

[0124] FIG. 6 differs from FIG. 5 in that the first cutting direction 25 is along the X-axis, with the result that the boundaries 19, 20 are drawn in a way that corresponds to the boundaries of FIG.

[0125] Figures 7 to 12 show a first machining sequence, in which material in the first layer 11 of Figure 5 is removed with the turning tool 1 of Figure 1. A first cutting direction 25 is set along the Z axis and a second cutting direction 26 is set along the X axis. Thus, the longitudinal segments 16, 18 (more precisely, the material in each of the longitudinal segments 16, 18) are removed before the radial segment 17. The first cutting direction 25 is set towards the left side. Thus, the longitudinal segments 16, 18 are removed by moving the turning tool 1 towards the left side. Figure 7 shows the starting position of the turning tool when removing the first segment 16, and Figure 8 shows the end position. Thus, a first pass is illustrated by Figures 7 and 8, during which the turning tool 1 moves towards the left side.

[0126] Figures 9 and 10 respectively show the starting and ending positions of the turning tool 1 on the second pass. Again, the turning tool 1 moves towards the left side.

[0127] 11 and 12 show the reactive start and end positions of the turning tool 1 in the third and final pass. Since the second cutting direction 26 is downwards, i.e. towards the blank's rotation axis (not shown), the turning tool 1 moves downwards.

[0128] The first cutting edge 2 is active when the longitudinal segments 16, 18 are removed, and the second cutting edge 3 is active when removing the radial segment 17. Thus, the wear is distributed over a longer portion of the cutting edge. When moving the turning tool 1 towards the end position of FIG. 12, the cutting depth is relatively deep. In other words, the portion of the second cutting edge 3 that is active, i.e. in cutting state, is relatively shallow. This is due to the fact that the segment 16 has been removed before the third pass. Thus, the risk of insert breakage can be reduced.

[0129] Figures 13-18 show a second machining sequence, in which the first layer is removed through three passes. The segmentation of the first layer is the same as for the first machining sequence, since the first cutting direction 25 is along the Z-axis and the second cutting direction 26 is along the X-axis. For the first machining sequence, the longitudinal segments 16, 18 are removed before the radial segment 17. Since the first cutting direction 25 is towards the right side, the longitudinal segments 16, 18 are each removed by moving the turning tool 1 towards the right side. In the first pass, one longitudinal segment 18 is removed, as can be seen in Figures 13 and 14, in which the starting and ending positions of the turning tool 1 are shown. The second pass, in which the other longitudinal segment 16 is removed, is shown in Figures 15 and 16. In the third and final pass, shown in Figures 17 and 18, the radial segment 17 is removed. The second cutting direction 26 is upward, i.e. away from the blank's axis of rotation (not shown), so the turning tool 1 moves upward. When the turning tool 1 moves towards the start of the third pass shown in FIG. 17, the long active second cutting edge 3 is avoided, thereby reducing the risk of insert breakage. The second cutting edge 3 is active during the first and second passes (see FIGS. 13-16) and the first cutting edge 2 is active during the third pass (see FIGS. 17 and 18). Furthermore, the active portions of the nose cutting edge 4 overlap less during the third pass compared to the first and second passes, thereby increasing tool life. During at least most of the first, second and third passes, the entry angle is acute, which the inventors have found further reduces insert wear.

[0130] 19-24 show a third machining sequence in which material in the first layer 11 of FIG. 6 is removed using the turning tool 1 of FIG. 1. A first cutting direction 25 is set along the X-axis and a second cutting direction 26 is set along the Z-axis. As the first cutting direction 25 is set along the X-axis, the radial segment 17 is removed first. As the first cutting direction 25 is downwards, i.e. towards the axis of rotation (not shown), the turning tool 1 moves downwards during the first pass, as can be seen in FIGS. 19 and 20. Then, through the second and third passes shown in FIGS. 21-24, the longitudinal segments 16, 18 are removed. Towards the end of the second pass, near the end position shown in FIG. 22, the cutting depth can be kept relatively deep compared to the case where the radial segment 17 is not removed before the second pass. The second cutting edge is active, i.e. in cutting, during the first pass and the first cutting edge is active during the second and third passes, whereby the wear is distributed over a longer portion of the cutting edge, which is beneficial in terms of tool life.

[0131] Figures 25-30 show a fourth machining sequence in which material in the first layer 11 of Figure 6 is removed using the turning tool 1 of Figure 1. A first cutting direction 25 is set along the X-axis and a second cutting direction 26 is set along the Z-axis. Since the first cutting direction 25 is set along the X-axis, the radial segment 17 is removed first. Since the first cutting direction 25 is upwards, i.e. away from the axis of rotation (not shown), the turning tool 1 moves upwards during a first pass, as can be seen in Figures 25 and 26. Then, through a second and third pass shown in Figures 27-30, the longitudinal segments 16, 18 are removed. The first cutting edge is active, i.e. in a cutting state, during the first pass and the second cutting edge is active during the second and third passes. The wear is thereby distributed over a longer portion of the cutting edge and there is less overlap with respect to the nose edge, which is beneficial in terms of tool life. During at least most of the first, second and third passes, the lead angle is acute, which the inventors have found further reduces insert wear.

[0132] Reference is now made to Figure 31, which shows a turning tool 1 having the same characteristics as the turning tool of Figure 1, and a blank having a blank shape 10 different from that of Figure 1. The target shape 5 also differs from that of Figure 1. The target shape 5 extends continuously between first and second target endpoints 22, 23 and is formed by a plurality of portions 6, 7, 8, 9, 21. The target shape 5 comprises three longitudinal portions 9, 21, 39 parallel to the Z axis, three radial portions 8, 38, 40 parallel to the X axis, three arcuate convex portions 6, 27, 28 and two arcuate concave portions 7, 24.

[0133] A first layer 11 is generated, which extends between the target shape 5 and the outer boundary 13 of the first layer. The outer boundary 13 of the first layer is spaced apart from the target shape 5. The first layer 11 is generated in a manner corresponding to FIG. 1, i.e. the offset distance is a constant value. The offset distance Ox in the x-direction is equal to the offset distance Oz in the z-direction, and the thickness of the first layer 11 is uniform. The parting angle α is set to 45°. The outer boundary 13 of the first layer comprises three convex portions 14, 46, 47 corresponding to the convex portions 6, 27, 28 of the target shape 5, and one or two concave portions 15, 47 in the form of well-defined internal angles. The first layer 11 is completely within the material.

[0134] Since there is material outside the first layer 11, a second layer 34 is generated as shown in FIG. 32. The inner boundary of the second layer is equivalent to the outer boundary of the first layer 13. The second layer 34 is generated in the same way as the first layer 11. The outer boundary of the second layer 34 is related to the outer boundary 13 of the first layer in the same way that the outer boundary 13 of the first layer is related to the target shape 5. The outer boundary of the second layer is spaced from the outer boundary 13 of the first layer by a constant value, i.e. the vertical distance from the outer boundary 13 of the first layer to the outer boundary 13 of the second layer is a constant value and is the same value or offset distance as the outer boundary 13 of the first layer. In this way, the first and second layers 11, 34 have the same thickness. The second layer 34 is partially in the material. The blank shape 10 extends partially outside the outer boundary of the second layer.

[0135] The third layer 35 shown in FIG. 33 is generated. The outer boundary of the third layer 35 is completely outside the blank shape 10. Therefore, no further layers are generated. The third layer 35 is generated in the same way as the first and second layers 11, 34. The layers 11, 34, 35 are then each divided into segments. The boundary lines 19, 20, 29, 30, 41 for the first layer are arranged according to the procedure of FIG. 3. Since the first cutting direction 25 is along the Z axis, each boundary line 20, 29, 30 that intersects with the convex portion 6, 27, 28 of the target shape 5 is arranged parallel to the Z axis. Each boundary line 19, 41 that intersects with the concave portion of the outer boundary 13 of the first layer is parallel to the X axis. The boundary lines in the second and third layers 34, 35 are generated in a corresponding manner. The number of segments is equal for each of the layers 11, 34, 35. From the segment 18 adjacent to the first target endpoint 22, every other segment is a longitudinal segment 18, 11, 43 and every other segment is a radial segment 17, 42, 44. From the same end of each of the second and third layers 34, 35, there is a corresponding alternation between the longitudinal and radial segments. The outer layer, the third layer 35, is removed first by removing all segments of the third layer that contain material, i.e., that are intersected by the blank shape 10. In FIG. 33, this includes all segments except one longitudinal segment 62. Since the first cutting direction 25 is along the Z-axis, all longitudinal segments 58, 60 of the third layer 35 that contain material are removed first, followed by all radial segments 59, 61, 63 of the third layer 35. Since the first cutting direction 25 is toward the left, each of the longitudinal segments 58, 60 is removed by moving the turning tool (not shown) toward the left. Preferably, segment 60 is removed before segment 58 to reduce air time. Then, radial segments 59, 61, 63 are removed by moving the turning tool (not shown) downwards, i.e., in the second cutting direction 26 for each segment. Preferably, the order of removal is segment 59 first, followed by segment 61 and segment 63 last. Then, all segments containing material of the second layer 34 are removed in a corresponding manner.The order of removal is preferably segment 56, segment 54, segment 52, segment 53, segment 55, segment 57. Afterwards, all segments containing material of the first layer 11 are removed in a corresponding manner. The order of removal is preferably segment 43, segment 16, segment 18, segment 17, segment 42, segment 44.

[0136] FIG. 34 shows how the same target shape 5 can be produced from the same blank shape 10 with the same layers 11, 34, 35 as in FIG. 33, if the first and second cutting directions 25, 26 are set differently. In FIG. 34, the first cutting direction 25 is along the X-axis downwards, i.e. towards the axis of rotation (not shown). The second cutting direction 26 is along the Z-axis towards the left. Since the first cutting direction 25 is along the X-axis, the boundary lines 19, 20, 29, 30, 41 are arranged in the same manner as in FIG. 4 for all layers 11, 34, 35. All segments contain material, and the order of removal is preferably segment 59, segment 61, segment 63, segment 62, segment 60, segment 58, segment 53, segment 55, segment 57, segment 56, segment 54, segment 52, segment 17, segment 42, segment 44, segment 43, segment 16, segment 18. The turning tool (not shown) of the method described in FIGS. 33 and 34 corresponds to the turning tool of FIG.

[0137] Figures 35-38 show how the same target shape 5 as in Figures 31-34 can be produced from the same blank shape 10 if the layers 11, 34, 35 are produced in a different manner. The difference with Figures 31-34 is that the outer boundary 13 of the first layer comprises a well-defined convex corner 14 associated with the concave portion 6, 27, 28 of the target shape 5. Said corner 14 is produced in the same way as described with respect to Figures 5 and 6. Further layers 34, 35 are produced in a corresponding manner as shown in Figures 36-38, respectively.

[0138] In FIG. 37, the first cutting direction is along the Z axis. Thus, the boundary lines 19, 20, 30, 41 are generated in the same way as in FIG. 5. The boundary lines for the second and third layers 34, 35 are generated in the same way as in the first layer 11. The second cutting direction 26 is upwards along the X axis, i.e. away from the blank's rotation axis (not shown). All segments except one longitudinal segment 62 contain material. The segments are removed in the same order as in FIG. 33. All longitudinal segments 58, 60, 52, 54, 56, 18, 16, 43 are removed by moving the turning tool towards the right side. All radial segments 63, 61, 59, 57, 55, 52, 44, 42, 17 are removed by moving the turning tool upwards.

[0139] In Figure 38, the first cutting direction is along the X-axis. Thus, the boundaries 19, 20, 30, 41 are generated the same as in Figure 6. The boundaries for the second and third layers 34, 35 are generated the same as in the first layer 11. The segments are removed in the same order as in Figure 33.

[0140] FIG. 39 shows a target shape 5 and a blank shape 10, which have a different shape than those described above. A first ply 11, which is partially in the blank, is generated such that the outer boundary 13 of the first ply is spaced from the target shape 5 by a certain offset distance. Said distance is measured perpendicularly from the target shape 5 to the outer boundary 13 of the first ply. The parting angle α is set to 45°. The auxiliary lines 31, 32, 49 connecting the target shape 5 and the outer boundary 13 of the first ply are arranged such that said boundary lines 31, 32, 49 respectively form an angle with the Z axis equal to the parting angle α. Two auxiliary lines 32, 49 each intersect with a respective convex portion 6, 27 of the target shape. One auxiliary line 31 intersects with a convex portion 7 of the target shape. Since the first cutting direction 25 is along the Z axis, the boundary lines 20, 29 intersecting with the convex portions 6, 27 are arranged parallel to the Z axis. Said boundary lines 20, 29 each intersect with a respective auxiliary line 32, 49 at the target shape 5. One boundary line 19 is arranged parallel to the X-axis and intersects with one auxiliary line 31 at the outer boundary 13 of the first layer. The boundary lines 19, 20, 29 separate alternating longitudinal and radial segments 18, 16; 17. The angle β that the target shape 5 forms with the Z-axis is less than or equal to 45° for all longitudinal segments 16, 18. In this case, the target shape 5 specifically means the inner boundary of each longitudinal segment 16, 18.

[0141] The turning tool 1 differs from the above-mentioned turning tools in that the first and second cutting edges 2, 3 are relatively short and the turning insert 50 includes third and fourth cutting edges 64, 65 spaced apart from the nose cutting edge 4 by a distance less than the offset distance. The third and fourth cutting edges 64, 65 form an angle of 60° or less. The segments are removed such that the order of removal is the longitudinal segments 18 and 16, then the radial segments 42 and 17. During the removal of the longitudinal segments 18, 16, respectively, the turning tool 1 is moving towards the right side. When removing the radial segments 42, 17, the turning tool 1 is moving upwards.

[0142] FIG. 40 differs from FIG. 39 in that the first and second cutting directions are swapped. Thus, the boundary lines 19, 20, 29 are arranged in a different manner. The boundary lines 20, 29 intersect the target shape 5 at the same point as in FIG. 39, but are arranged parallel to the X-axis. The boundary line 19 intersects the outer boundary 13 of the first layer at the same point as in FIG. 39, but are arranged parallel to the Z-axis. The radial segments 42, 17 are removed before the longitudinal segments 18, 16. The direction in which the turning tool 1 moves while removing the segments 42, 17, 18, 16 is the same as in FIG. 39.

[0143] FIG. 41 shows a further example in which the target shape 5 and the turning tool 1 are identical to FIG. 1, but the blank shape 10 is different. The first layer 11 is generated and segmented in the same way as in FIG. 6, since the first cutting direction 25 is along the same axis, namely the X-axis. The blank shape 10 extends beyond the outer boundary 13 of the first layer. The second layer 34 is generated and segmented in a manner corresponding to the first layer 11. Segments of the second layer 34 are removed by moving the turning tool 1 away from the rotation axis (not shown), such that the first radial segment 53 is removed first. Secondly, the longitudinal segment 54 is removed by moving the turning tool 1 towards the right side. Each of the above passes ends when there is no material remaining in the respective cutting direction 25, 26. Due to the radius of curvature of the nose cutting edge 4, a small amount of material may remain in each of said segments 53, 54. However, such remaining material is removed during removal of the subsequent layers, i.e., segments 16, 17, 18 of the first layer 11. After the second layer 34, segments 17, 18, 16 of the first layer 11 are removed following the sequence and direction of FIG.

[0144] FIG. 42 shows a blank shape 10 similar to FIG. 41, but with the first and second cutting directions 25, 26 swapped. The first and second layers 11, 34 are produced similar to FIG. 41. Only one segment 53 of the second layer 34 contains material. Said segment 53 is removed by moving the turning tool in an upward direction, i.e. in the second cutting direction 26. Then, according to FIG. 5, segments 18, 16, 17 of the first layer 11 are removed.

Claims

1. 1. A computer-implemented method for generating a tool path cycle for removing material (12) from a blank using a turning tool (1), the turning tool (1) comprising first and second cutting edges (2, 3) connected by a convex nose cutting edge (4) such that a predefined target shape (5) is formed, the blank being rotatable about an axis of rotation represented by a Z-axis, an X-axis being orthogonal to the Z-axis and representing a radial direction; the target shape (5) comprises a plurality of portions (6, 7, 8, 9, 21, 24, 27, 28, 38, 39, 40), the plurality of portions (6, 7, 8, 9, 21, 24, 27, 28, 38, 39, 40) comprising one or more convex portions (6, 27, 28) and one or more concave portions (7, 24); at least one radial portion (8, 38, 40) extends along said X-axis to a greater extent than said Z-axis; at least one longitudinal portion (9, 21, 39) extends along the Z-axis to a greater extent than along the X-axis; one or more of the concave portions (7, 24) of the target shape (5) comprises an arcuate portion (7) having a radius of curvature equal to or greater than the radius of curvature of the nose cutting edge (4), the arcuate portion (7) connecting one radial portion (8) and one longitudinal portion (9); receiving input of a blank shape (10); and receiving an input of the target shape (5), The method comprises: the further step of setting an offset distance (m); a further step of receiving input of a turning tool (1); A further step of setting a first cutting direction (25) and a second cutting direction (26), a further step of setting cutting directions, one of the first and second cutting directions (25, 26) representing a direction of movement of the turning tool (1) along the X-axis and one of the first and second cutting directions representing a direction of movement of the turning tool (1) along the Z-axis; A further step of producing a first layer (11) completely or partially within said material (12), said first layer (11) being bounded by said target shape (5) and a first layer outer boundary (13); the outer boundary (13) of the first layer is spaced from the target shape (5) by the offset distance (m); a further step of producing a first layer, the outer boundary (13) of said first layer comprising one or more convex portions (14, 46, 48) and one or more concave portions (15, 47); a further step of arranging a boundary line (19, 20, 29, 30, 41) parallel to said Z axis and / or parallel to said X axis, the further step of positioning said boundary lines (19, 20, 29, 30, 41) such that each of said boundary lines extends between said target shape (5) and said first layer outer boundary (13) and intersects either a concave portion (15, 47) of said first layer outer boundary (13) or a convex portion (6, 27, 28) of said target shape (5); Consequently, a further step of dividing said first layer (11) into segments (16, 17, 18, 42, 43, 44) separated by said boundary lines (19, 20, 29, 30, 41), one longitudinal segment (11, 18, 43) adjacent to each longitudinal portion (9, 21, 39); one radial segment (17, 42, 44) adjacent each radial portion (8, 38, 40); a further step of dividing the first layer into segments, wherein one boundary line (19) is arranged to separate the radial segments (17) and the longitudinal segments (16) such that the arcuate portion abuts one of the radial and longitudinal segments (17, 16) by intersecting the concave portion (15) of the outer boundary (13) of the first layer; a further step of removing all segments (16, 17, 18, 42, 43, 44) such that the segment bordering the arcuate portion is removed after the segment adjacent to the segment, wherein the turning tool (1) is moved in one direction along the Z-axis when removing one or more of the longitudinal segments (11, 18, 43) and the turning tool (1) is moved in one direction along the X-axis when removing one or more of the radial segments (17, 42, 44); and the further step of removing all segments where the directions along the X-axis and the Z-axis are both either both towards the concave portion (7, 24) or both away from the concave portion (7, 24).

2. When the first cutting direction (25) is along the Z-axis, one boundary line (20, 29, 30) that intersects with the convex portion (6, 25, 26) of the target shape (5) is arranged parallel to the Z-axis; the further step of arranging one boundary line (19, 41) that intersects with the concave portion (15, 47) of the outer boundary (13) of the first layer parallel to the X-axis; the further step of arranging one boundary line (20, 29, 30) that intersects with the convex portion (6, 27, 28) of the target shape (5) parallel to the X-axis and one boundary line (19, 41) that intersects with the concave portion (15, 47) of the outer boundary (13) of the first layer parallel to the Z-axis when the first cutting direction (25) is along the X-axis; a further step of removing said one or more longitudinal segments (11, 18, 43) followed by removing said one or more radial segments (17, 42, 44) if said first cutting direction (25) is along said Z-axis; a further step of removing said one or more radial segments (17, 42, 44) followed by removing said one or more longitudinal segments (11, 18, 43) if said first cutting direction (25) is along said X-axis; The method of claim 1 , comprising:

3. When the first cutting direction (25) is along the Z-axis, removing the one or more longitudinal segments (11, 18, 43) by moving the turning tool (1) in one direction along the Z-axis, and subsequently removing the one or more radial segments (17, 42, 44) by moving the turning tool (1) in one direction along the X-axis; When the first cutting direction (25) is along the X-axis, removing the one or more radial segments (17, 42, 44) by moving the turning tool (1) in one direction along the X-axis, and subsequently removing the one or more longitudinal segments (11, 18, 42) by moving the turning tool (1) in one direction along the Z-axis. The method of claim 2.

4. the radial portions (8, 38, 40) are parallel to the X-axis and the longitudinal portions (9, 21, 39) are parallel to the Z-axis; one of the radial and longitudinal portions (8, 38, 40; 9, 21, 39) is formed by a single pass; The method of claim 1.

5. said target shape (5) comprising a further longitudinal portion (21); said further longitudinal portion (21) and said radial portion (8) are connected by said convex portion (6) in the form of an arcuate portion (6), a third segment (18) is delimited by said further longitudinal portion (21); The method of claim 1.

6. a further step of receiving an input of one parameter or two parameters (Ox, Oz) representing an offset distance in the X direction (Ox) and an offset distance in the Z direction (Oz). The method of claim 1 , comprising:

7. said convex portion (6) connects said radial portion (8) parallel to said X-axis and a further longitudinal portion (21) parallel to said Z-axis; a radial portion of the outer boundary (13) of the first layer is parallel to the radial portion (8) and is spaced apart in the Z direction by the offset distance (Oz); a longitudinal portion of the outer boundary (13) of the first layer is parallel to the further longitudinal portion (21) and is spaced apart in the X direction by the offset distance (Ox); the first portion and the longitudinal portion of the outer boundary (13) of the first layer intersect at a convex portion (14) of the outer boundary (13) of the first layer, the convex portion (14) being in the form of a 90° angle; The method of claim 6.

8. the further step of setting a splitting angle (α); a further step of locating the boundary line (20, 29, 30) intersecting the convex portion (6, 27, 28) from a point on the convex portion (6, 27, 28) with a normal that forms an angle with the Z axis equal to the division angle (α); The method of claim 1 , comprising:

9. a further step of setting said split angle (α) equal to arctan(Ox / Oz). The method of claim 8, comprising:

10. a further step of calculating the offset distance (m) from the parameters (Ox, Oz) representing the offset distance in the X and Z directions; and a further step of positioning an outer boundary (13) of said first layer vertically spaced from said target shape (5) by said offset distance (m); The offset distance (m) is calculated according to the following formula: m=((90-β)・Ox+β・Oz) / 90 where the angle (β) is the angle the target shape makes with the Z axis. The method of claim 6.

11. a further step of generating vertical auxiliary lines (31, 32, 49) from a point of each concave portion (7, 24) of said target shape (5) forming a normal to said Z axis at an angle equal to said division angle (α); a further step of positioning said one or more boundary lines (20, 29, 30) intersecting a convex portion (6, 27, 28) of said target shape (5) such that said boundary line (20, 29, 30) intersects said point; a further step of positioning said one or more boundary lines (19, 41) to intersect with a concave portion (7, 24) of the outer boundary (13) of said first layer such that said boundary line (19, 41) each intersects with an intersection of one auxiliary line (31, 32, 49) and said outer boundary (13) of said first layer; The method of claim 8, comprising:

12. a further step of immediately or substantially immediately after removing all blank (12) in each segment (16, 17, 18, 42, 43, 44) at the feed rate, moving said turning tool (1) to the subsequent segment at a rate faster than said feed rate. The method of claim 1 , comprising:

13. the further step of positioning the turning tool (1) such that the first cutting edge (2) forms an angle with the Z-axis when all segments (16, 17, 18, 42, 43, 44) are removed; The turning tool (1) comprises a tool body and a turning insert (50), the tool body extends along its longitudinal axis (A1) extending between a front end and a rear end; The rear end is connected to a machine interface (51) of a CNC lathe; the turning insert (50) is connected to the front end of the tool body; The longitudinal axis (A1) is arranged parallel to the X axis, The method of claim 1.

14. a further step of setting said turning tool (1) before setting said first and second cutting directions (25, 26); a further step of setting the first and second cutting directions (25, 26) towards the one or more concave portions (7, 24) when the nose angle of the turning tool (1) is greater than 60° and the first and second cutting edges (2, 3) each have a length in top view that exceeds the offset distance (m); The method of claim 1 , comprising:

15. a further step of setting said first and second cutting directions (25, 26) before setting said turning tool (1); and when one or both of the first and second cutting directions (25, 26) are set in a direction away from the one or more concave portions (7, 24), setting the turning tool (1) such that a nose angle of the turning tool (1) forms an angle of more than 60° or the turning tool has third and fourth cutting edges (64, 65) that form an angle of 60° or less therebetween, the third and fourth cutting edges (64, 65) being spaced from the nose cutting edge (4) by a distance that is less than the offset distance (m). The method of claim 1 , comprising:

16. If the blank shape (10) is at least partially outside the outer boundary (13) of the first layer, a further step of generating one or more further layers (34, 35) further away from the target shape until all generated layers (34, 35) are completely spaced from the material (12), Further layers (34, 35) are defined by inner and outer boundaries (36, 37), respectively; a further step of generating a further layer (34, 35), wherein for each further layer (34, 35), said respective outer boundary (36, 37) is spaced from said respective inner boundary by said offset distance (m); a further step of dividing each of the further layers (34, 35) into a set of segments (52-57; 58-63) separated by boundaries, the sets of segments (52-57; 58-63) respectively correspond to the sets of segments (16, 17, 18, 42, 43, 44) of the first layer (11); a further step of dividing each of the further layers, each of said boundary lines corresponding to a boundary line (19, 20, 29, 30, 41) of said first layer (11); a further step of instructing said turning tool (1) to remove all segments (58-63) containing blank (12) from the top layer (35), and subsequently remove all segments (52-57) containing blank (12) from each subsequent layer (34) until said first layer (11) remains; The method of claim 1 , comprising:

17. A computer program product having instructions that, when executed by a computing device or system, cause the computing device or system to perform the method of any one of claims 1 to 16.

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