Tool path correction device and tool path correction method

Abstract

A tool path modification device according to an embodiment of the present disclosure, which enables high precision machining with a small computational load, is provided with: a tool path acquisition unit that acquires tool path information that specifies a tool path along which a tool for machining a workpiece travels using the coordinates of a plurality of command points through which the tool should pass; a command point adjustment unit that modifies the tool path information by changing the coordinates of the command points or adding or removing the command points; a curvilinearization section extraction unit that extracts, from the tool path information modified by the command point adjustment unit, a curvilinearization section for curvilinearizing the tool path; a tool path curvilinearization unit that replaces the information of the curvilinearization section in the tool path information modified by the command point adjustment unit with curve information; and a tool path output unit that outputs the tool path information after the tool path curvilinearization unit has replaced the information of the curvilinearization section.

Description

[Technical Field]

[0001] The present invention relates to a tool path correction device and a tool path correction method. [Background technology]

[0002] In order to machine a workpiece with a tool in a machine tool, an NC program is created using a numerical control device to control the machine tool so that the tool moves relatively along the target shape (product shape) of the workpiece after machining, which is generated using CAD, etc. Creating an NC program for a numerical control device from CAD data is generally done by creating CL data that describes the movement path of the tool from the CAD data in CAM, and then converting the CL data into an NC program using a postprocessor.

[0003] In CL data and NC programs, the tool path is generally described as a set of multiple command points that specify the coordinates through which the tool's reference point must pass. In particular, in areas with large curvature in the target shape, the machining point may deviate from the target shape between the command points. Furthermore, the tool moves to scan the target shape—that is, moves in a specified feed direction, shifts slightly in a direction intersecting the feed direction, and then moves again in the feed direction, repeating this process. If there is a difference in the depth of cut between adjacent movement paths, a minute step will be formed, resulting in an unintended pattern on the surface of the workpiece after machining.

[0004] In order to suppress such machining errors, a technology has been proposed that analyzes the machining program and inserts new command points between command points described in the machining program to reduce errors in the cutting depth (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2018 / 020663 Summary of the Invention [Problem to be solved by the invention]

[0006] Inserting a large number of command points improves machining accuracy, but increases the computational load on the numerical control device. For this reason, technology that enables accurate machining even with numerical control devices that do not have high processing power is desired. [Means for solving the problem]

[0007] A tool path modification device according to one aspect of the present disclosure includes a tool path acquisition unit that acquires tool path information that specifies a tool path along which a tool that machines a workpiece moves, based on the coordinates of a plurality of command points through which the tool must pass; a command point adjustment unit that modifies the tool path information by changing the coordinates of the command points or by adding or removing the command points; a curved section extraction unit that extracts a curved section along which the tool path is curved from the tool path information after modification by the command point adjustment unit; a tool path curving unit that replaces information of the curved section in the tool path information after modification by the command point adjustment unit with curved information; and a tool path output unit that outputs the tool path information after the tool path curving unit has replaced the information of the curved section.

[0008] A tool path correction method according to another aspect of the present disclosure includes the steps of acquiring tool path information that identifies a tool path along which a tool that processes a workpiece moves by the coordinates of a plurality of command points through which the tool must pass; correcting the tool path information by changing the coordinates of the command points or adding or removing the command points; extracting a curved section from the corrected tool path information that curves the tool path; replacing information about the curved section in the corrected tool path information with curve information; and outputting the tool path information after replacing information about the curved section. [Effects of the Invention]

[0009] According to the present disclosure, machining can be performed with high machining accuracy with a small computational load. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a block diagram showing a configuration of a machining system including a tool path correction device according to a first embodiment of the present disclosure. [Figure 2] FIG. 2 is a schematic diagram illustrating a tool path generated by CAM. [Figure 3] 3 is a schematic diagram illustrating the position adjustment of a command point of the tool path in FIG. 2; [Figure 4] 4 is a schematic diagram illustrating an example of adjusting the density of command points of the tool path of FIG. 3. FIG. [Figure 5] 3 is a schematic diagram illustrating a curved section of the tool path in FIG. 2; FIG. [Figure 6] FIG. 10 is a block diagram showing the configuration of a machining system including a tool path correction device according to a second embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] First Embodiment Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Fig. 1 is a block diagram showing the configuration of a machining system including a tool path correction device according to a first embodiment of the present disclosure. The machining system of Fig. 1 includes a CAD 1, a CAM 2, a tool path correction device 3 according to an embodiment of the present disclosure, a postprocessor 4, a numerical control device 5, and a machine tool 6.

[0012] CAD 1 is a known system for performing design using a computer device. That is, CAD 1 is used to design a target shape (product shape) of a workpiece to be machined by a machine tool 6. The target shape may be specified by a plane, a cylindrical surface, a spherical surface, a Bezier surface, a NURBS surface, or the like.

[0013] CAM2 is a known system that generates machining programs and the like used by a numerical control device 5 that controls a machine tool 6 to machine a workpiece into a target shape designed by CAD1 using the machine tool 6. CAM2 generates tool path information that specifies the tool path along which a tool that machines the workpiece moves by using a plurality of command points through which the tool must pass. To this end, CAM2 may generate the shape of a machining area corresponding to the target shape created by CAD1. The tool path information may be generated in the form of Cutter Location (CL) data that does not take into account the configuration and settings of each individual machine tool 6. CAM2 may be configured integrally with the computer device that constitutes CAD1.

[0014] The tool path information may include information about which part of the tool moves on the tool path. Examples of the part of the tool that moves on the tool path (hereinafter sometimes referred to as the reference point) include the tip of the tool and the center of the tool shape (for example, the ball center of a ball end mill). The tool path information may also include information about whether the movement of the tool along the tool path is a cutting feed or a non-cutting feed (rapid feed). Furthermore, the tool path information may also include information about the specific feed rate when the tool moves along the tool path.

[0015] Fig. 2 shows a tool path F including multiple command points P. Fig. 2 also shows the tool shape M and target shape S at each command point P. As shown in the figure, the tool shape M at the command point P ideally contacts the target shape S, but in reality, there are cases where the tool shape M cuts into the target shape S or moves away from the target shape S.

[0016] The tool path modification device 3 includes a tool path acquisition unit 31, a tool shape acquisition unit 32, a target shape acquisition unit 33, a command point adjustment unit 34, a curved section extraction unit 35, a tool path curving unit 36, and a tool path output unit 37. The tool path modification device 3 can be realized by, for example, executing an appropriate control program on a computer device equipped with a CPU, memory, an input / output interface, etc. The tool path acquisition unit 31, the tool shape acquisition unit 32, the target shape acquisition unit 33, the command point adjustment unit 34, the curved section extraction unit 35, the tool path curving unit 36, and the tool path output unit 37 of the tool path modification device 3 are functionally distinct and do not necessarily need to be clearly distinguishable in terms of physical configuration and program configuration. The tool path modification device 3 may also be integrated with other devices such as a CAM 2 and a post-processor 4. That is, the tool path modification device 3 may be realized by adding control programs to the CAM 2, the post-processor 4, etc. The tool path modification device 3 is a device that implements one aspect of the tool path modification method according to the present disclosure.

[0017] The tool path acquisition unit 31 acquires the tool path information generated by the CAM 2. The tool path acquisition unit 31 may acquire the tool path information via a server, a recording medium, or the like (not shown).

[0018] The tool shape acquisition unit 32 acquires tool shape information that specifies the shape of a tool. The tool shape acquisition unit 32 can be configured to acquire, from the CAM 2, the tool shape information that the CAM 2 used to generate the tool path information. The tool shape acquisition unit 32 may also be configured to acquire the tool shape information from a server, a recording medium, or the like (not shown).

[0019] The target shape acquisition unit 33 acquires target shape information that specifies the target shape of the workpiece after machining. The target shape information may be information on the product shape generated by CAD1, or information on the shape of the machining area created by CAM2 (for example, the shape of the machining surface approximated as a collection of multiple planes). In other words, the target shape acquisition unit 33 may acquire the target shape information from CAD1 or from CAM2. The target shape acquisition unit 33 may also acquire the target shape information from another device or a recording medium.

[0020] The command point adjustment unit 34 modifies the tool path information by changing the coordinates of the command points P of the tool shape information acquired by the tool shape acquisition unit 32, or by adding or removing command points P, so that the difference between the tool path F and the target shape S is reduced when the tool moves along a path connecting the command points P with line segments.

[0021] 3, the command point adjustment unit 34 can be configured to adjust the position of the command point P based on the tool shape information and the target shape information so that the tool shape M comes into contact with the target shape S. Note that "the tool shape comes into contact with the target shape" allows for a certain amount of error and means that the distance or overlap between the target shape S and the tool shape M is equal to or less than a certain value.

[0022] The command point adjustment unit 34 may move the command point P in the direction of the rotation axis of the tool. By moving the command point P in the direction of the rotation axis of the tool, it is often possible to reduce the calculation load for adjusting the position of the command point P. More specifically, the command point adjustment unit 34 calculates the distance between the tool shape M and the target shape S at the command point P of the tool path F, and if this distance exceeds an allowable value, the command point P may be moved in the direction of the rotation axis of the tool so that the tool shape M comes into contact with the target shape S.

[0023] Furthermore, the command point adjustment unit 34 may move the command point P in the normal direction of the target shape S. By moving the command point P in the normal direction of the target shape S, the amount of movement of the command point P can be made relatively small. Furthermore, the command point adjustment unit 34 may set a constraint surface within which the tool should be moved at the coordinates of the command point P, and move the command point P within this constraint surface.

[0024] 4, the command point adjustment unit 34 generates corrected path information in which command points P are added and deleted, thereby further reducing the difference between the tool path F and the target shape S when the command points P are connected by line segments. That is, by adjusting the density of the command points P so that the density of the command points P increases as the curvature of the target shape S increases, the deviation of the tool path F from the target shape S can be reduced. Note that, although the tool path F can be brought closer to the target shape S as the number of command points P increases, it may be effective to reduce the density of the command points P in areas where the curvature of the target shape S is small in order to prevent the calculation load on the post processor 4 and the numerical control device 5 from becoming excessive.

[0025] The curved section extraction unit 35 extracts curved sections to be curved by the tool path curving unit 36 ​​from the tool path information (corrected path information) after the command point adjustment unit 34 corrects the command points P. Specifically, the curved section extraction unit 35 can be configured to set division points Ps that divide the tool path F into a plurality of sections, and to sort the plurality of sections into curved sections Rc that should be curved and non-curved sections Rs that do not need to be curved, as exemplified in Fig. 5. Note that the "tool path information after correction" includes the tool path information after processing in the case where no change has been made to the tool path information despite the processing related to correction.

[0026] The curved section extraction unit 35 preferably extracts the curved section Rc so as not to cross over command points P corresponding to edges of the shape of the workpiece after machining. In other words, the curved section extraction unit 35 can be configured to divide the tool path F using command points corresponding to edges of the shape of the workpiece after machining as division points Ps, and to extract, from these sections, sections where the curvature is equal to or greater than a predetermined value, sections where cutting feed is performed, etc. as curved sections Rc to be curved.

[0027] As the command points to be set as division points Ps, it is possible to select a command point P at which cutting feed and non-cutting feed are switched, a command point P where the tool travel direction changes before and after by more than a threshold value, a command point P where the ratio of the distance between the previous and next command points P changes by more than a threshold value, etc. Furthermore, the division points Ps may be set by the command point adjustment unit 34 when rearranging the command points P.

[0028] In addition, the curved section extraction unit 35 may extract curved sections Rc by setting as division points Ps points where the trend of change in the curvature of the tool path F changes, such as the start and end points of the curvature change, inflection points of the curvature change (points where the positive and negative signs of the change rate are reversed), and points where the change rate changes discontinuously.

[0029] Furthermore, the curved section extraction unit 35 may extract the curved section Rc by taking into account the target shape information. For example, the curved section extraction unit 35 may be configured to extract the curved section Rc by setting the command point P closest to the edge of the target shape S as the segment point Ps. By taking into account the target shape information, it is possible to easily and accurately identify the command point P that corresponds to the edge of the shape of the workpiece after machining.

[0030] The curved section extraction unit 35 may also extract the curved section Rc taking tool shape information into consideration. When the orientation of the tool's rotation axis is constant, if the target shape S has an edge, the tool path F will draw a shape that is an inverse of the tool shape M to prevent the tool shape M from biting into the target shape S. Therefore, if the tool path F draws a shape that is an inverse of the tool shape M or a shape smaller than the inverse of the tool shape M, it can be determined that an edge will be formed in the machined shape of the workpiece. Therefore, by taking the tool shape M into consideration, it is possible to identify the command point P corresponding to the edge of the machined shape of the workpiece. For example, if the tool is a ball end mill, the point where the curvature of the tool path F is equal to or smaller than the curvature of the tool shape M can be set as the segment point Ps. Naturally, using both the target shape information and the tool path allows for more appropriate extraction of the curved section Rc.

[0031] The tool path curve generating unit 36 ​​replaces the information of the curved section Rc of the tool path information after the command point adjustment unit 34 corrects the command points P with curve information. That is, the tool path curve generating unit 36 ​​expresses the tool path F in the curved section Rc by function approximation such as a circular arc, an elliptical arc, a helical curve, a spiral curve, an involute curve, a NURBS curve, or a Bézier curve, rather than by linear approximation that connects multiple command points P with line segments. In particular, by using a NURBS curve, it is possible to reduce the difference between the tool path F after curve information conversion and the target shape S, regardless of the type of curve the tool path F and the target shape S are. Note that since the curves that can be handled may differ depending on the numerical control device 5, the tool path curve generating unit 36 ​​selects a function to be used for curve conversion in accordance with the numerical control device 5.

[0032] When a NURBS curve is used, the approximate curve of the curved section Rc is calculated by the coordinates C(u1) to C(u m ) and the coordinates of n control points P1 to P n and the well-known B-spline basis function N i Using (X), it is expressed by the following equation (1).

[0033]

number

[0034] That is, the tool path curve generating unit 36 ​​generates a curve by using the coordinates P1 to P2 of the n control points. n and replaces the curved section Rc of the tool path information with information that specifies the above formula (1). Since a small number of control points is likely to result in large errors, it is preferable to increase the number of control points in order until the distance between the approximation curve and the command point P becomes equal to or less than a predetermined threshold.

[0035] The tool path curve forming unit 36 ​​may set a contribution degree to the command points P in the curved section Rc and derive curve information. The coordinates of the command points P may deviate from a position that accurately corresponds to the intended target shape S due to errors caused by calculation accuracy, human error during modeling, errors when importing data created in a different system, etc. Such position deviations are generally very small as distance errors. However, when the distance between the command points P is small, the error in the angle of the line segment connecting the command points P may become relatively large. In such cases, by setting a small contribution degree for the command points P that are close to adjacent command points P, it is possible to prevent errors in the command points P from causing large errors in the derived curve.

[0036] Specifically, when a NURBS curve is used, the approximate curve of the curved section Rc is, for example, a curve with a contribution α e When setting, it can be expressed by the following equation (2).

[0037]

number

[0038] In equation (2), the contribution α e If the value of is set to be smaller than 1, the influence of the e-th command point P becomes relatively small. A contribution greater than 1 may be set, or contributions may be set for multiple or all command points P.

[0039] The tool path output unit 37 stores the tool path information that has been corrected by the command point adjustment unit 34 and in which the information of the curved section Rc has been replaced with curve information by the tool path curve unit 36, and outputs it to the post-processor 4 as needed.

[0040] The post-processor 4 converts the data format of the tool path information output from the tool path correction device 3 into a data format that can be processed by the numerical control device 5. Typically, the post-processor 4 converts the tool path information written in CL data format into a machining program written in G-code, STEP-NC, or the like. Curve information of the tool path information is converted into a corresponding function interpolation command statement. A well-known post-processor can be used as the post-processor 4.

[0041] The numerical control device 5 controls the machine tool 6 in accordance with the tool path information input from the post-processor 4. As the numerical control device 5, a well-known device can be used.

[0042] The machine tool 6 uses a tool to machine the workpiece in accordance with instructions from the numerical control device 5. As the machine tool 6, a well-known machine can be used.

[0043] As described above, the machining system in Fig. 1 is equipped with the tool path correction device 3, which reduces the deviation between the actual machining points and the target shape S, allowing the workpiece to be machined to the target shape S with high precision. In addition, high-precision machining is possible because the deviation in the cutting depth between adjacent tool paths F when the tool scans the surface of the workpiece is reduced. This makes it possible to prevent unintended patterns from being formed on the surface of the workpiece, thereby improving the aesthetic appearance of the product obtained by machining the workpiece.

[0044] A tool path correction method according to one embodiment of the present disclosure, which is implemented by the tool path correction device 3, includes the steps of acquiring tool path information that identifies a tool path F along which a tool that processes a workpiece moves by the coordinates of a plurality of command points P through which the tool must pass; correcting the tool path information by changing the coordinates of the command points P or adding or removing command points P; extracting a curved section Rc from the corrected tool path information that curves the tool path F; replacing the information of the curved section Rc in the corrected tool path information with curve information; and outputting the tool path information in which the information of the curved section Rc has been replaced with curve information.

[0045] Second Embodiment Fig. 6 is a block diagram showing the configuration of a machining system including a tool path correction device according to a second embodiment of the present disclosure. The machining system of Fig. 6 includes a CAD 1, a CAM 2, a tool path correction device 3A according to an embodiment of the present disclosure, a post-processor 4, a numerical control device 5, and a machine tool 6. In the machining system of Fig. 6, components similar to those in the machining system of Fig. 1 are designated by the same reference numerals, and redundant explanations will be omitted. In the machining system of Fig. 6, the tool path correction device 3A corrects a machining program written in, for example, G-code, which is input by the post-processor 4 to the numerical control device 5.

[0046] The tool path correction device 3A includes a tool path acquisition unit 31A, a tool shape acquisition unit 32, a target shape acquisition unit 33, a command point adjustment unit 34A, a curved section extraction unit 35A, a tool path curving unit 36A, and a tool path output unit 37A. The tool path correction device 3A can be realized by causing a computer device including, for example, a CPU, a memory, an input / output interface, etc. to execute an appropriate control program, and may be configured integrally with the postprocessor 4, the numerical control device 5, etc.

[0047] The tool path acquisition unit 31A acquires tool path information from the post processor 4. Therefore, the tool path acquired by the tool path acquisition unit 31A is in a format such as G code. The tool path acquisition unit 31A, command point adjustment unit 34A, curved section extraction unit 35A, tool path curving unit 36A and tool path output unit 37A in the machining system of Fig. 6 are the same in function as the tool path acquisition unit 31, command point adjustment unit 34, curved section extraction unit 35, tool path curving unit 36 ​​and tool path output unit 37 in the machining system of Fig. 1, except for the data format they handle.

[0048] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments. Furthermore, the effects described in the above-described embodiments are merely a list of favorable effects resulting from the present disclosure, and the effects of the present disclosure are not limited to those described in the above-described embodiments.

[0049] For example, in the above-described embodiment, the command point adjustment unit adjusts the tool path information using the tool shape and target shape, but the command point adjustment unit may be any unit that can improve the accuracy of the tool path information by adjusting the placement of command points. Therefore, in the tool path correction device, the tool shape acquisition unit and the target shape acquisition unit may be omitted in some cases.

[0050] In the tool path correction device, the tool path information acquired by the tool path acquisition unit may be data in any format, such as a format used inside a CAM, and the tool path information output by the tool path output unit may be data in any format, such as a format used inside a numerical control device. For this reason, the tool path correction device may have a configuration internally for converting the data format of the tool path information. [Explanation of symbols]

[0051] 1 CAD 2 CAM 3 Tool path correction device 4 Post Processor 5. Numerical Control Equipment 6 Machine tools 31, 31A Tool path acquisition unit 32 Tool shape acquisition section 33 Target shape acquisition section 34,34A Command point adjustment section 35, 35A Curved section extraction section 36, 36A Tool path curve section 37,37A Tool path output section F Tool Path M Tool shape P command point Rc curved section Rs Non-curved section S target shape

Claims

1. a tool path acquisition unit that acquires tool path information that specifies a tool path along which a tool for machining a workpiece moves, based on coordinates of a plurality of command points through which the tool should pass; a command point adjustment unit that corrects the tool path information by changing the coordinates of the command points or adding or removing the command points; a curved section extraction unit that extracts a curved section for curving the tool path from the tool path information corrected by the command point adjustment unit; a tool path curve forming unit that replaces information on the curved section in the tool path information corrected by the command point adjustment unit with curve information that represents the tool path as a NURBS curve; a tool path output unit that outputs the tool path information after the tool path curve forming unit replaces the information of the curved section; Equipped with The tool path curving unit sets a contribution degree to each of the command points in the curved section, and reduces the contribution degree of the command point that is close to an adjacent command point.

2. The curved section extraction unit extracts the curved section so as not to cross the command points corresponding to edges of the shape of the workpiece after machining. The tool path correcting device according to claim 1 .

3. a tool shape acquisition unit that acquires tool shape information that identifies the shape of the tool; The tool path correcting device according to claim 1 , wherein the curved section extracting unit extracts the curved section in consideration of the tool shape information.

4. a target shape acquisition unit that acquires target shape information that specifies a target shape of the workpiece after machining, The tool path correcting device according to claim 1 , wherein the curved section extracting unit extracts the curved section in consideration of the target shape information.

5. acquiring tool path information that specifies a tool path along which a tool for machining a workpiece moves, based on coordinates of a plurality of command points through which the tool should pass; modifying the tool path information by changing the coordinates of the command points or adding or removing the command points; A step of extracting a curved section for curving the tool path from the corrected tool path information; replacing information on the curved section in the corrected tool path information with curve information that represents the tool path as a NURBS curve; a step of outputting the tool path information after replacing the information of the curved section; Equipped with A tool path correction method, in which, in the process of replacing information of the curved section with the curve information, a contribution degree is set for each of the command points in the curved section, and the contribution degree of a command point that is close to an adjacent command point is reduced.

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