Design System

Abstract

To reduce the occurrence of edge chipping in face milling.SOLUTION: A design system for designing a face milling process for cutting a machining surface of a work piece with a face mill, includes: a calculation unit that calculates a withdrawal angle in a tool path which is a movement path of a face milling cutter on the machining surface; and a change unit that changes the tool path already set so that a machining area in which the withdrawal angle is within a predetermined range on the machining surface becomes smaller. The change unit changes the tool path by at least one of the following means (i) to (iii): (i) offsetting a position of the tool path from an end face of the work piece; (ii) swapping a start point and an end point of the tool path; and (iii) changing an entry angle of the tool path to the machining surface.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a design system. [Background technology]

[0002] For example, the finishing device described in Patent Document 1 performs finishing by pressing a processing tool against the work surface where burrs are generated so that the shape of the work surface approaches a target shape. At this time, the movement path of the processing tool along the work surface (hereinafter referred to as the "tool path") is created in advance based on CAD data of the target shape. Setting the tool path is necessary when using a machining center that performs automatic processing by numerically controlling the movement of the processing tool based on the shape of the work and the processing position, and is widely used. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2006-58961 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in conventional processing devices such as the above-mentioned finishing device, only tool paths are created to remove burrs that have been generated, and there has been no thought of creating tool paths that suppress the generation of burrs in the first place. For this reason, conventional devices have had problems in that they cannot suppress the generation of burrs and the occurrence of chipping that accompanies the generation of burrs (a phenomenon in which material that has accumulated on the cutting edge during processing does not remain as a burr, and part of the workpiece is chipped together with the burr). [Means for solving the problem]

[0005] The present disclosure can be realized in the following forms.

[0006] (1) According to one embodiment of the present disclosure, a design system is provided that performs process design for face milling, which cuts a machined surface of a workpiece with a face milling cutter, and includes: a calculation unit that calculates a draft angle of the face milling cutter relative to the machined surface, the draft angle being defined as an angle between a direction in which a cutting edge of the face milling cutter leaves an end surface of the workpiece adjacent to the machined surface and the end surface of the workpiece; and a modification unit that modifies the tool path that has already been set so that a machining region on the machined surface in which the draft angle falls within a predetermined range is reduced, and the modification unit modifies the tool path by at least one of the following means (i) to (iii). (i) offsetting a position of the tool path from the end face of the workpiece; (ii) swapping the start and end points of the tool path; (iii) changing an approach angle of the tool path on the machining surface; According to this embodiment, the changer changes the tool path by at least one of the means (i) to (iii) so that the machining area in which the clearance angle of the face milling cutter falls within a predetermined specified range is reduced. Experiments have confirmed that there is a correlation between the clearance angle of the face milling cutter during machining and the height of the burr generated after machining. In general, if the burr height is high, edge chipping is more likely to occur. Edge chipping means that when the burr does not remain on the product but is scattered, a part of the product is chipped together with the burr, and the occurrence of such edge chipping results in a defective product. The applicant has found that there is a correlation between the clearance angle of the face milling cutter during milling and the occurrence of "edge chipping". Then, by setting the specified range in advance to a range in which edge chipping is likely to occur, the tool path is changed so that the machining area in which the clearance angle falls within the specified range is reduced, making it possible to suppress the occurrence of burrs and edge chipping. Furthermore, it can be understood that the machining area where the draft angle is within the specified range is a concern area where chipping is likely to occur after machining. Therefore, in the above embodiment, the change unit changes the tool path by at least one of the means (i) to (iii), thereby making it possible to reduce the concern area. In other words, according to the above embodiment, the tool path is changed so as to reduce the concern area where chipping is predicted to occur, and the final tool path is designed, so that the occurrence of chipping can be reduced during face milling. (2) In the above aspect, the present invention may further include a creating unit that automatically creates the tool path before it is changed by the changing unit. According to this embodiment, first, a tool path is automatically created by a creating unit included in the design system, and then the changing unit changes the tool path already set by the creating unit. For example, compared to a form in which a tool path created by another system is loaded into this system, the same system can process everything from the automatic creation of a reference tool path to the process of changing the tool path to reduce the number of areas where chipping may occur. (3) In the above embodiment, the predetermined range of the escape angle may be equal to or greater than 70° and equal to or less than 110°. The applicant has found that edge chipping occurs frequently when the draft angle is 70° or more and 110° or less. According to the above embodiment, the tool path is changed by the changing unit so that the machining area to be machined at the draft angle of 70° or more and 110° or less, where edge chipping is likely to occur, is reduced, so that the occurrence of edge chipping can be more reliably reduced. (4) In the above embodiment, the tool path may further include a pattern acquisition unit that acquires a pattern of the tool path that has already been set, and the change unit may select the means to be used from among (i) to (iii) according to the pattern acquired by the pattern acquisition unit, and change the tool path using the selected means. According to this embodiment, an appropriate modification means is selected according to the tool path pattern acquired by the pattern acquisition unit, and the tool path is modified by the modification unit. Therefore, compared to a case where a modification means is selected unconditionally regardless of the tool path pattern, it is possible to reliably reduce the number of problem areas and to perform efficient modification processing. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic block diagram showing a functional configuration of a design system according to a first embodiment of the present disclosure. [Diagram 2] FIG. 13 is a plan view for explaining a draft angle and is a schematic view of a workpiece and a face milling cutter. [Diagram 3] 13 is a flowchart showing the procedure of a tool path generation process executed by the design system. [Figure 4] 13 is a flowchart showing details of a tool path changing process. [Diagram 5] FIG. 13 is a graph showing the change in the amount of chipping caused by the face milling cutter depending on the clearance angle. [Figure 6] This is a visual representation of the primary tool path created when designing the finishing machining of a workpiece. [Figure 7] FIG. 7 is a diagram visually illustrating a region of concern when machined by the primary tool path shown in FIG. 6. [Figure 8] FIG. 13 is a visual representation of the modified secondary tool path. [Figure 9] FIG. 9 is a visual representation of a region of concern when machined using the secondary tool path shown in FIG. 8. [Figure 10] FIG. 7 is a visual representation of a first tool path created when designing the finish machining of a workpiece different from that shown in FIG. 6. [Figure 11] FIG. 11 is a diagram visually showing a portion of concern when machined by the primary tool path shown in FIG. 10. [Figure 12] FIG. 13 is a visual representation of the modified secondary tool path. [Figure 13]FIG. 13 is a visual representation of a region of concern when machined using the secondary tool path shown in FIG. 12. [Figure 14] FIG. 12 is a visual representation of a first tool path created when designing the finish machining of a workpiece different from that shown in FIGS. 6 and 10. [Figure 15] FIG. 15 is a diagram visually showing a portion of concern when machined by the primary tool path shown in FIG. 14. [Figure 16] FIG. 13 is a visual representation of the modified secondary tool path. [Figure 17] FIG. 17 is a visual representation of a region of concern when machined using the secondary tool path shown in FIG. 16. [Figure 18] FIG. 13 is a visual representation of a primary tool path in another embodiment. [Figure 19] FIG. 19 is a diagram visually illustrating a secondary tool path obtained by changing the angle of the primary tool path shown in FIG. 18 so that the tool path is vertical. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] A. Embodiment: A1. Overall configuration of the design system: A design system 100 of the present disclosure will be described with reference to Figs. 1 to 17. Fig. 1 is a schematic block diagram showing a functional configuration of the design system 100 in a first embodiment of the present disclosure. The design system 100 of the first embodiment is a system that performs a process design for face milling in which a face mill imitates the machined surface of a workpiece (hereinafter also simply referred to as a "workpiece") so that the plane to be machined of the workpiece approaches the plane accuracy of a target shape. The workpiece is, for example, various parts mounted on a vehicle, and is a casting made of iron or aluminum.

[0009] The design system 100 generates a tool path. The "tool path" is the path of movement of a face milling cutter as a machining tool when machining an object by a machining machine. More specifically, it is a central orbit through which the center of the diameter of the face milling cutter passes. Note that the "center" here is not limited to the "center" in the strict sense, but has a broader meaning including a point within a predetermined distance range from the center. The above-mentioned predetermined distance is, for example, a value of 5 mm or less, and more preferably, a value of 2 mm or less.

[0010] In Fig. 1, only components necessary for explaining the features of this embodiment are shown as functional blocks, and some of the general components are omitted. In other words, each component shown in Fig. 1 is a functional concept, and does not necessarily have to be physically configured as shown. For example, the specific form of distribution and integration of each functional block is not limited to that shown in the figure, and all or part of them can be functionally or physically distributed or integrated in any unit.

[0011] 1, the design system 100 includes a CAD (Computer Aided Design) device 1, a database device 2, and a tool path generating device 3. The CAD device 1, the database device 2, and the tool path generating device 3 are electrically connected to each other. The CAD device 1 is capable of creating, processing, and displaying CAD data.

[0012] The database device 2 includes a storage unit 21, receives CAD data created or processed by the CAD device 1 from the CAD device 1, and stores the received CAD data, etc. in the storage unit 21. More specifically, the database device 2 stores before-machining shape data 22, after-machining shape data 23, basic machining data 24, tool path model data 25, tool path pattern data 26, etc. in the storage unit 21.

[0013] The before-machining shape data 22 includes information on the before-machining shape of the workpiece, such as three-dimensional CAD data on the before-machining shape and coordinate data that represents the three-dimensional CAD data in a predetermined fixed coordinate system. The before-machining shape data 22 is created by the CAD device 1.

[0014] The after-machining shape data 23 includes information on the shape of the work after machining (the target shape of the finished product), and includes, for example, three-dimensional CAD data on the shape after machining and coordinate data that expresses the three-dimensional CAD data in a predetermined fixed coordinate system. The after-machining shape data 23 is created by the CAD device 1.

[0015] The basic machining data 24 includes information necessary for generating a tool path. The basic machining data 24 includes information about the processing machine and information about the tools attached to the processing machine. Specifically, the basic machining data 24 includes the work feed speed of the processing machine, the shape, diameter, and radial rake angle of the face milling cutter, position information, and the like.

[0016] The tool path model data 25 includes information such as a tool path that is a model for generating a tool path to form a finished shape for each finished shape data, a machining procedure, and a feed rate of a machining tool for each machining procedure. The tool path pattern data 26 includes information on a tool path pattern that is selected and determined according to the type of tool path. More specifically, in this embodiment, the data includes three types of patterns: an "overlap pattern", a "curve pattern", and a "straight line pattern". Details of each pattern will be described later.

[0017] The tool path generating device 3 automatically creates a tool path based on the CAD data sent from the CAD device 1 or the database device 2, and then generates a final tool path through a tool path modification based on the draft angle. The final tool path generated by the tool path generating device 3 is output as NC data to a processing machine (not shown).

[0018] The tool path generating device 3 includes an automatic tool path creating unit 31, a draft angle calculating unit 32, a tool path pattern acquiring unit 33, and a tool path changing unit 34. The tool path generating device 3 is, for example, a microcomputer including a CPU, a ROM, a RAM, a calculation device, a display device, other input / output ports, etc. (not shown), and the CPU of the microcomputer reads out and executes a program stored in the ROM, thereby functioning as the automatic tool path creating unit 31, the draft angle calculating unit 32, the tool path pattern acquiring unit 33, and the tool path changing unit 34. The calculation device performs calculation processing based on various information. The display device displays information such as various input information and calculation results by the calculation device.

[0019] The automatic tool path creation unit 31 is executed by, for example, well-known CAM (Computer Aided Manufacturing) software, and automatically creates a tool path. The automatic tool path creation unit 31 uses three-dimensional shape data of a product shape model that is the processing target designed by CAD, three-dimensional shape data of a work before processing, and three-dimensional shape data of a tool to set the moving speed of the tool and automatically generate a tool path. In the following explanation, the tool path automatically created at this stage is called the "primary tool path." The automatic tool path creation unit 31 corresponds to the "creation unit."

[0020] The draft angle calculation unit 32 calculates the draft angle θ. Here, the draft angle θ will be described with reference to FIG. 2. FIG. 2 is a diagram for explaining the draft angle θ, and is a plan view that typically shows the workpiece W and the face milling cutter 42. As shown in FIG. 2, the workpiece W has a processing surface 44 and an end surface 41 adjacent to the processing surface 44. The "draft angle θ" is an angle between the end surface 41 of the workpiece W and the direction in which the cutting edge 43 of the face milling cutter 42 exits from the end surface 41 of the workpiece W when viewed in the direction in which the face milling cutter 42 is pressed against the workpiece W (also called the axial direction). As shown in FIG. 2, the face milling cutter 42 has a plurality of cutting edges 43 called chips on its outer periphery. The face milling cutter 42 performs finish machining by cutting the processing surface 44 by rotating at high speed in the direction of arrow A1 around the milling axis center C, which is the center of the milling axis not shown. The face milling cutter 42 moves on the processing surface 44 along a direction (arrow A2) that intersects the milling axis.

[0021] In Fig. 2, when the face milling cutter 42 is viewed in the axial direction, the angle between the direction in which the cutting edge 43 leaves the end face 41 of the workpiece W and the end face 41 is defined as "draft angle θ". In other words, the "draft angle θ" can also be said to be "the angle between the tangent T at the milling cutter diameter φ of the tip of the cutting edge 43 and the edge of the workpiece W". The draft angle calculation unit 32 calculates the draft angle θ for each predetermined region of the created primary tool path. The draft angle calculation unit 32 corresponds to the "calculation unit".

[0022] The tool path pattern acquisition unit 33 refers to the tool path pattern data 26 to determine which tool pattern the primary tool path created by the tool path automatic creation unit 31 corresponds to, and acquires the pattern. The tool path change unit 34 changes the primary tool path based on the exit angle θ calculated by the exit angle calculation unit 32 and the tool path pattern acquired by the tool path pattern acquisition unit 33. The tool path pattern acquisition unit 33 corresponds to a "pattern acquisition unit." The tool path change unit 34 corresponds to a "change unit." Details of the operations of the exit angle calculation unit 32 and the tool path change unit 34 will be described in detail below in conjunction with the operation of the system.

[0023] A2. Overall Operation of Design System 100: Next, the tool path generation process executed by the design system 100 described above in detail will be described. FIG. 3 is a flowchart showing the procedure of the tool path generation process executed by the design system 100. As shown in FIG. 3, first, in step 10 (hereinafter, step will be abbreviated as "S"), predetermined shape data is read from the database device 2 into the tool path generation device 3. Next, in S20, conditions for the machining process are set. Specifically, conditions such as the diameter and radial rake angle of the face milling cutter 42 are input by the operator. Then, in S30, a primary tool path is calculated by the automatic tool path creation unit 31.

[0024] Next, in S40, the clearance angle θ of the primary tool path is calculated by the clearance angle calculation unit 32. In this clearance angle calculation step, the clearance angle θ is calculated for each predetermined region of the primary tool path based on the diameter and radial rake angle of the face milling cutter 42, information on the faces constituting the edge of the target workpiece W, and the like. Then, in S50, the tool path is changed by the tool path change unit 34. In this embodiment, the "predetermined region" refers to a region set for each unit length in the tool path, and means a region of a predetermined shape and size that includes a path equivalent to that unit length.

[0025] Fig. 4 is a flowchart showing details of the tool path changing process. As shown in Fig. 4, first, in S51, the tool path pattern acquisition unit 33 selects a tool pattern of a primary tool path. Here, the closest tool path pattern is selected from among "overlap pattern", "curve pattern", and "straight line pattern" based on the planar shape of the primary tool path and the like. Details will be described later. Next, in S52, the tool path changing unit 34 selects a changing means according to the tool path pattern, and the tool path is changed by the selected changing means. Specific changing means are the following three (i) to (iii).

[0026] (i) Offsetting the position of the tool path from the end face 41 of the workpiece (workpiece W) (hereinafter also referred to as the "offset means"). (ii) Swapping the start and end points of the tool path (hereinafter also referred to as the "swapping means"). (iii) Changing the approach angle of the tool path on the machining surface 44 (hereinafter also referred to as the "approach angle changing means"). Note that "changing the approach angle of the tool path on the machining surface 44" means, in other words, changing the proceeding direction of the tool path on the machining surface 44 relative to the workpiece when the machining surface 44 is viewed in a plan view with the workpiece fixed. Note that the details of each of the above-mentioned changing means will be described later. When the tool path is changed in S52 in this manner, the tool path changing process (S50) is completed and the tool path generating process ends. The tool path generated by the tool path generating process, i.e., the changed tool path obtained by S50, is transmitted to a control device of the processing machine such as a PLC (Programmable Logic Control), and the milling process is controlled according to the tool path.

[0027] A3. Toolpath modification process details: Next, the above-mentioned primary tool path change process (S52) will be described in more detail using a specific example. Fig. 5 is a graph showing the change in the amount of edge chipping caused by the draft angle θ of the face milling cutter 42, with the horizontal axis representing the draft angle θ and the vertical axis representing the amount (number) of edge chipping. Experiments conducted by the applicant have revealed that, as shown in Fig. 5, approximately 80% or more of edge chipping occurs when the draft angle θ is in the range of 70° to 110°. Therefore, in this embodiment, the machining area by the tool path with a draft angle θ of 70°≦θ≦110° is defined as a "problem area" where edge chipping is a concern.

[0028] In the modification process, the primary tool path is modified so as to reduce the above-mentioned problem areas. If the problem areas can be reduced in size at the design stage, it is possible to reduce chipping that occurs after milling. In the following description, the tool path after the primary tool path is modified by the modification unit 34 is referred to as the "secondary tool path."

[0029] As an example, the finish machining design process of the workpiece W1 will be described with reference to Figs. 6 to 9. Figs. 6 to 9 are plan views visually showing the tool paths P1 and Pa1 generated and the derived part of concern E in the finish machining design of the workpiece W1. Fig. 6 is a diagram visually showing the primary tool path P1 created when finishing the workpiece W1. In Fig. 6, the machining surface 45 is shown by cross-hatching. In this embodiment, the machining surface 45 is an annular surface having a predetermined width arranged so as to surround the entire circumference of the opening. Also, in Fig. 6, the face milling cutter 42 is shown by a two-dot chain line, and the primary tool path P1 is shown by a thick line.

[0030] In the primary tool path P1 shown in Fig. 6, a portion 51 that cuts the upper side of the machining surface 45 shown in Fig. 6 and a portion 52 that cuts the lower side of the machining surface 45 shown in Fig. 6 overlap with an end face 53 of the machining surface 45, and the proportion of this overlapping portion to the entire primary tool path P1 is large, approximately 80% or more. Such a pattern of the primary tool path P1 corresponds to an "overlap pattern." Note that the value "80%" is an example and can be changed as appropriate.

[0031] 7 is a diagram visually showing the part of concern E when machined by the primary tool path P1 shown in FIG. 6. In FIG. 7, the part of concern E is illustrated by a thick line. In this embodiment, in the tool pattern acquisition step (S51), an "overlap pattern" is acquired as the tool pattern, and in the change means selection and change step (S52), the means (i) (offset means) is selected as the change means, and the primary tool path P1 is changed according to the means (i). This is because the part where the tool path and the end face 53 of the workpiece W1 overlap is a part where the load on the cutting edge 43 is large during machining, and it is expected that the part of concern E can be reduced by reducing the overlapping part by the offset means.

[0032] FIG. 8 is a diagram visually showing the secondary tool path Pa1 after the change. As shown in FIG. 8, the secondary tool path Pa1 is offset so that the portion overlapping the end face 53 in the primary tool path P1 is shifted from the end face 53. Here, the offset direction may be any direction as long as the machining surface 45 can be machined by the tool path after the offset. However, from the viewpoint of shortening the design time, it is desirable that the increase rate of the total length of the tool path is as small as possible. In the example in FIG. 8, the milling surface overlapping the machining surface 45 is offset in a direction in which it becomes larger. That is, the portion 51 (see FIG. 7) that cuts the upper machining surface 45 is moved upward in FIG. 8 in the secondary tool path Pa1, and the portion 52 (see FIG. 7) that cuts the lower machining surface 45 is moved downward in FIG. 8 in the secondary tool path Pa1.

[0033] FIG. 9 is a diagram visually showing the parts of concern E when machined by the secondary tool path Pa1 shown in FIG. 8. In FIG. 8, the parts of concern E are shown in bold. As is clear from a comparison of FIG. 9 with FIG. 7, the total number of parts of concern E in the secondary tool path Pa1 (see FIG. 9) is less than the total number of parts of concern E in the primary tool path P1 (see FIG. 7). Note that the total number of parts of concern E is the total value of the lengths of the parts of concern E shown in bold. According to tests conducted by the applicant, a specific reduction of approximately 66% was confirmed as a result of the change processing.

[0034] As another example, the finish machining design process of the workpiece W2 having a machining surface different from that of the workpiece W1 will be described with reference to Figs. 10 to 13. Figs. 10 to 13 are diagrams visually showing the tool paths P2 and Pa2 generated and the derived concern area E in the finish machining design of the workpiece W2. Fig. 10 is a diagram visually showing the primary tool path P2 created when finishing the workpiece W2. In Fig. 10, the machining surface 46 is shown by cross-hatching. In Fig. 10, the primary tool path P2 is shown by a thick line. The primary tool path P2 shown in Fig. 10 has a complex curved shape formed by combining multiple curves. Such a pattern of the primary tool path P2 corresponds to a "curve pattern". In this curve pattern, the machining surface shape is also curved, the machining area is relatively small, and the degree of freedom that can be taken as the tool path shape is small. In the primary tool path P2, the face milling cutter 42 moves from the arrow A3 side toward the arrow A4.

[0035] Fig. 11 is a diagram visually showing the part of concern E when machined by the primary tool path P2 shown in Fig. 10. In Fig. 11, the part of concern E is illustrated by a thick line. In this embodiment, in a tool pattern acquisition step (S51), a "curve pattern" is acquired as the tool pattern, and in a change means selection and change step (S52), the means (ii) (exchange means) is selected as the change means, and the primary tool path P2 is changed in accordance with the means (ii).

[0036] This is because by switching the start point and end point, the rotation and revolution (the orbit along the primary tool path P2) of the face milling cutter 42 both rotate clockwise, changing from down-cutting to up-cutting, where only the revolution is counterclockwise, which changes the way the cutting edge 43 contacts the machining surface 46, and is expected to reduce the area of ​​concern E. This is particularly applicable when it is difficult to move the tool path line itself due to the shape of the machining surface. This is particularly applicable to soft materials such as aluminum, which is considered to have a relatively low load on the cutting edge 43 even in up-cutting.

[0037] Fig. 12 is a diagram visually showing the changed secondary tool path Pa2. As shown by arrows A5 and A6 in Fig. 12, in the secondary tool path Pa2, the face milling cutter 42 moves from the side of arrow A5 toward the side of arrow A6. That is, in the secondary tool path Pa2, the start point and end point of the primary tool path P2 are swapped.

[0038] FIG. 13 is a diagram visually illustrating the area of ​​concern E when machined by the secondary tool path Pa2 shown in FIG. 12. In FIG. 13, the area of ​​concern E is illustrated by a thick line. As is clear from a comparison between FIG. 11 and FIG. 13, The sum of the concern areas E in the secondary tool path Pa2 (see Fig. 13) is the sum of the concern areas E in the primary tool path P2 (see Fig. 11). Tests by the applicant have shown that the modified treatment results in a specific reduction of approximately 42%.

[0039] As yet another example, the finish machining design process for the workpiece W3 having a machining surface 47 different from the workpieces W1 and W2 will be described with reference to Figs. 14 to 17. Figs. 14 to 17 are diagrams visually showing the tool paths P3 and Pa3 generated and the derived part of concern E in the finish machining design for the workpiece W3. Fig. 14 is a diagram visually showing the primary tool path P3 created when finishing the workpiece W3. In Fig. 14, the machining surface 47 is shown by cross-hatching. Also, in Fig. 14, the primary tool path P3 is illustrated by a hollow arrow. The primary tool path P3 shown in Fig. 14 is a straight line. The pattern of the primary tool path P3 consisting of only straight lines in this way corresponds to a "straight line pattern."

[0040] The workpiece W3 assumed here is a relatively small object to be machined, such as a valve body, and is finish-machined in one pass using a face mill 42 having a milling diameter Φ larger than the vertical width of the machining surface 47 perpendicular to the feed direction.

[0041] FIG. 15 is a diagram visually showing the part of concern E when machined by the primary tool path P3 shown in FIG. 14. In FIG. 15, the part of concern E is illustrated by a thick line. In this embodiment, in the tool pattern acquisition step (S51), a "straight line pattern" is acquired as the tool pattern, and in the change means selection and change step (S52), the means (iii) (change of approach angle) is selected as the change means, and the primary tool path P3 is changed according to the means (iii). This is because changing the approach angle of the face milling cutter 42 changes the way the cutting edge 43 hits, and it is expected that the part of concern E will be reduced. This is particularly effective for things that can be machined in one pass with a linear movement.

[0042] Fig. 16 is a diagram visually showing the secondary tool path after the change. As shown in Fig. 16, the secondary tool path Pa3 has a different approach angle with respect to the primary tool path P3. Fig. 17 is a diagram visually showing the part of concern E when machined by the secondary tool path Pa3 shown in Fig. 16. In Fig. 17, the part of concern E is shown by a thick line.

[0043] As is clear from a comparison of Figs. 15 and 17, The sum of the concern areas E in the secondary tool path Pa3 (see Fig. 17) is the sum of the concern areas E in the primary tool path P3 (see Fig. 15). Tests by the applicant have shown a specific reduction of approximately 27% with the modified treatment.

[0044] As described above, in this embodiment, the automatically created primary tool paths P1, P2, and P3 are subjected to data analysis, and it is determined in S51 which pattern the primary tool paths P1, P2, and P3 are. For example, in machining the above-mentioned workpiece W1, whether the end face 53 and the primary tool path P1 overlap can be determined by comparing the coordinate system data of the primary tool path P1 and the end face 53.

[0045] Furthermore, in machining the above-mentioned workpiece W2, when the primary tool path P2 is complexly curved and the machining surface 46 is narrow, and the degree of freedom in changing the tool path is low, the judgment may be determined in advance based on factors such as the shape and size of the machining area of ​​the machining surface 46 and the diameter of the face milling cutter 42. Furthermore, in machining any of the workpieces W1, W2, W3, the outlines of the workpieces W1, W2, W3 and the tool paths P1, P2, P3 may be displayed superimposed on a display device such as a display, and the operator may visually verify and determine the change means.

[0046] [effect] According to the design system 100 of the first embodiment described above, the tool path modification unit 34 modifies the primary tool paths P1, P2, P3 by at least one of the above means (i) to (iii) so as to reduce the machining area in which the clearance angle θ of the face milling cutter 42 falls within a predetermined range (70° or more and 110° or less).

[0047] That is, the change unit 34 changes the primary tool paths P1, P2, and P3 by at least one of the above means (i) to (iii), so that the tool paths are changed to reduce the area of ​​concern E where chipping is predicted to occur, and the final tool path is designed after reducing the machining area where chipping is likely to occur. In this way, by taking an approach that prevents chipping from occurring at the machining design stage, it is possible to reduce the occurrence of burrs and chipping during machining by the face milling cutter 42. In turn, it is possible to reduce the occurrence of defective products.

[0048] The design system 100 of the first embodiment has a tool path pattern acquisition unit 33, and an appropriate change means is selected to change the primary tool paths P1, P2, P3 according to the patterns of the primary tool paths P1, P2, P3 acquired by the tool path pattern acquisition unit 33. Therefore, the change means can be selected more efficiently than a process in which a change means is selected unconditionally regardless of the tool pattern, and then an optimal tool path is derived by calculating whether the concerned part E has been reduced by the changed tool paths Pa1, Pa2, Pa3. As a result, the design process can be made faster.

[0049] B. Other embodiments: (B1) In the design system 100 of the first embodiment described above, for means (i) (offset means) and means (iii) (approach angle changing means), the offset amount and approach angle may be appropriately changed to generate multiple secondary tool paths (candidate secondary tool paths), and one tool path may finally be determined as the secondary tool path using these multiple candidate secondary tool paths.

[0050] That is, the primary tool path may be changed in multiple stages. In such a configuration, for example, in the example of the means (iii) (approach angle changing means), in Fig. 14, the draft angle may be calculated again for each of the different candidate secondary tool paths Pa4 to Pa7 after the change, the portion of concern E may be extracted, the total length of the portion of concern E may be calculated, and the tool path with the shortest length may be determined as the secondary tool path.

[0051] In addition, in an example of means (i) (offset means), the primary tool path may be moved a predetermined amount, and then moved another predetermined amount the next time, and the total length of the area of ​​concern E may be compared between the first and second times (or a total of N times), and the best tool path with the shortest length may be selected as the final secondary tool path.

[0052] (B2) In addition, in the above-mentioned means (ii) (exchanging means), the total of the parts of concern E in the primary tool paths P1, P2, and P3 after the change and before the change may be compared, and the smaller one may be selected. This makes it possible to more reliably reduce the parts of concern E.

[0053] (B3) In the design system 100 of the first embodiment, the angle range of the release angle θ, which is the portion E of concern where edge chipping may occur, is set to 70° or more and 110° or less, but it may also be set to, for example, 85° or more and 95° or less based on the experimental results of Fig. 5. Alternatively, it may be set over a plurality of ranges of values, such as 70° or more and 80° or less, 85° or more and 95° or less, or 100° or more and 110° or less.

[0054] (B4) In the design system 100 of the first embodiment, the means to be used for the primary tool paths P1, P2, and P3 are selected and changed according to the pattern, but it is also possible to determine the tool path that minimizes the total length of the concerned portion E as the final tool path from a plurality of calculation results using data changed by arbitrarily adopting the means (i) to (iii) without acquiring the tool path pattern. Also, the means (i) to (iii) may be appropriately combined.

[0055] (B5) Also, the method of determining the tool path pattern can be changed as appropriate. In the above first embodiment, the primary tool paths P1, P2, and P3 are viewed as a whole and are made to correspond to one pattern as a whole, but for example, a pattern may be extracted for each part of the primary tool paths P1, P2, and P3, and each part may be changed by different means (i) to (iii). For example, in the example shown in the machining design of the workpiece W1 (see Figs. 6 to 9), the tool path P1 was determined to be an "overlap pattern" because the overlapping portion was large relative to the entire tool path P1, but instead of determining it based on the ratio, for example, if even a small overlapping portion is detected, only a part of the overlapping primary tool path P1 may be changed to be offset.

[0056] (B6) The means (iii) (approach angle changing means) in the design system 100 of the first embodiment may be changed, for example, to an angle where a primary tool path consisting of only a plurality of straight lines is perpendicular to the edge of the workpiece. Fig. 18 is a diagram visually showing a primary tool path P4 in another embodiment, and Fig. 19 is a diagram visually showing a secondary tool path Pa8 obtained by changing the angle of the primary tool path P8 shown in Fig. 18 to one where the tool path is perpendicular. Such a change may also reduce the area of ​​concern E.

[0057] (B7) In the first embodiment, the design system 100 includes the automatic tool path creation unit 31 that automatically creates the primary tool paths P1, P2, and P3, but this does not have to be the case. In this case, for example, the primary tool paths P1, P2, and P3 created in another system can be read into the design system 100 and modified by the modification unit 34 so as to be optimized. Alternatively, in the case of a simple tool path, a tool path manually created by an individual can be read into the design system 100 and modified by the modification unit 34 so as to be optimized.

[0058] The present disclosure is not limited to the above-mentioned embodiments, and can be realized in various configurations without departing from the spirit of the present disclosure. For example, the technical features in each embodiment corresponding to the technical features in each form described in the Summary of the Invention column can be appropriately replaced or combined in order to solve some or all of the above-mentioned problems or to achieve some or all of the above-mentioned effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted. [Explanation of symbols]

[0059] 1...CAD device, 2...database, 3...tool path generating device, 21...storage unit, 22...before-machining shape data, 23...after-machining shape data, 24...basic machining data, 25...tool path model data, 26...tool path pattern data, 31...automatic tool path creation unit, 32...angle calculation unit, 33...tool path pattern acquisition unit, 34...tool path modification unit, 41, 53...end face, 42...face milling cutter, 43...cutting edge, 44-47...machined surface, 100...design system, C...center axis, E...area of ​​concern, P1, P2, P3...primary tool path, Pa1, Pa2, Pa3...secondary tool path, T...tangent, W, W1, W2, W3...workpiece

Claims

1. A design system for designing a process for face milling, which cuts the machining surface of a workpiece with a face milling cutter, comprising: When the angle between the direction in which the cutting edge of the face milling cutter is released from the end surface of the workpiece adjacent to the processing surface and the end surface of the workpiece is defined as the release angle of the face milling cutter with respect to the processing surface, a calculation unit that calculates the draft angle in a tool path that is a movement path of the face milling cutter on the machining surface; a modification unit that modifies the tool path that has already been set so that a machining area on the machining surface in which the draft angle falls within a predetermined range is reduced; wherein the change unit changes the tool path by at least one of the following means (i) to (iii): (i) offsetting the position of the tool path from the end face of the workpiece; (ii) swapping the start and end points of the tool path; (iii) changing the approach angle of the tool path on the machining surface;

2. The design system according to claim 1 , further comprising a creating unit that automatically creates the tool path before being modified by the modifying unit.

3. 3. The design system according to claim 1, wherein the predetermined range of the draft angle is equal to or greater than 70 degrees and equal to or less than 110 degrees.

4. A pattern acquisition unit that acquires a pattern of the tool path that has already been set is further provided, A design system as described in any one of claims 1 to 3, wherein the modification unit selects the means to be used from among (i) to (iii) above depending on the pattern acquired by the pattern acquisition unit, and modifies the tool path using the selected means.

Images