Workpiece processing method and workpiece processing device

Abstract

The processing device (1) comprises: a position offset detection unit (131) for calculating a correction value for correcting the position offset between an ideal contour line (P1) and an actual contour line (P3) in multiple angular directions based on the center of the hemispherical shape of the tool (3); a distance effect coefficient calculation unit (332) for calculating a first distance effect coefficient (Ed) indicating the influence of the position offset when processing the second processing point (T2) based on the distance between the tool (3) and the second processing point (T2) when the processing point of the tool (3) changes from one-point processing of a processing point (T1) on a workpiece (5) to two-point processing of a first processing point (T1) and a second processing point (T2); and a position offset correction unit (331) for correcting the position offset of the tool (3). When the processing point of the tool (3) changes from one-point processing to two-point processing, the position offset correction unit (331) corrects the position offset based on the correction value at the first processing point (T1) and the first distance effect coefficient (Ed) when the distance between the tool (3) and the second processing point (T2) is within a specified distance.

Description

Technical Field

[0001] The present invention relates to a workpiece processing method and a workpiece processing device. Background Art

[0002] In the past, the following workpiece processing device was used: using an NC program, a ball-end milling cutter (a tool with a hemispherical front end, hereinafter referred to as "the tool") was positioned relative to the workpiece (the material to be processed), and the tool was rotated to perform cutting processing on the workpiece.

[0003] In such machining devices, the tool is clamped and fixed to a tool holder, such as a spindle, to be positioned relative to the workpiece before cutting. Consequently, due to improper clamping, the tool may shift position when fixed to the tool holder. Furthermore, initial shape errors may occur in the tool. In such cases, the tool cannot be moved to the correct cutting position relative to the workpiece, resulting in the inability to perform high-precision cutting.

[0004] For example, Patent Document 1 discloses that, when machining a workpiece with a tool, the position of the tool (end mill) is corrected to take into account tool degradation due to wear. Specifically, Patent Document 1 discloses that the tool shape, which changes as the tool progresses in machining the workpiece, is scanned with a laser to calculate shape errors. Based on the calculated shape errors, a correction amount for the tool position is calculated, and by correcting the tool position, errors in the cutting surface are prevented.

[0005] However, the technology disclosed in Patent Document 1 corrects tool wear and tear, not tool shape or positioning errors. Furthermore, while Patent Document 1 mentions correcting errors when machining a workpiece with a single-point tool-to-workpiece contact, it does not mention correcting errors when machining with multiple (e.g., two) points of contact.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 63-233403 (JP S63-233403A) Summary of the Invention

[0009] The machining device of Patent Document 1 has a problem in that errors of the tool (end mill) cannot be corrected with high precision when the workpiece is machined at multiple points by the tool (end mill).

[0010] The present invention is made to solve such previous problems, and its purpose is to provide a workpiece processing method and a workpiece processing device, which can process the workpiece with high precision even when the workpiece is processed at multiple points by a tool (ball end mill).

[0011] In order to achieve the above-mentioned purpose, the workpiece processing method involved in the present invention is used to process the workpiece into a desired shape, wherein the above-mentioned processing method has the following steps: detecting the position offset between the contour line of the above-mentioned end mill when the end mill is held in the tool holding part, that is, the actual contour line and the contour line of the above-mentioned end mill in an ideal shape, that is, the ideal contour line, the lower end of the end mill is hemispherical, and the end mill rotates around the rotation axis to cut the above-mentioned workpiece; calculating the correction value for correcting the above-mentioned position offset between the above-mentioned ideal contour line and the above-mentioned actual contour line in multiple angular directions based on the center of the above-mentioned hemispherical shape; when the processing point processed by the above-mentioned end mill is removed from the first processing surface of the above-mentioned workpiece When the one-point machining of the first machining point is transformed into the two-point machining of the first machining point and the second machining point on the second machining surface different from the first machining surface, the first distance effect coefficient representing the influence of the above-mentioned position offset when machining the above-mentioned second machining point is calculated according to the distance between the above-mentioned end mill and the above-mentioned second machining point; and when the above-mentioned one-point machining is performed by relying on the above-mentioned end mill, the position offset of the above-mentioned first machining point is corrected based on the above-mentioned correction value, and when the one-point machining is transformed into the two-point machining, when the distance between the above-mentioned end mill and the above-mentioned second machining point is close to the specified distance, the position offset is corrected based on the above-mentioned correction value at the above-mentioned first machining point and the above-mentioned first distance effect coefficient.

[0012] The workpiece processing device involved in the present invention is used to process the workpiece into a desired shape, wherein the above-mentioned processing device comprises: an end mill, the lower end of the end mill is hemispherical, and the end mill rotates around a rotation axis to cut the above-mentioned workpiece; a tool holding portion, the tool holding portion is used to hold the above-mentioned end mill; a position offset detection portion, the position offset detection portion is used to detect the position offset between the contour line of the above-mentioned end mill, that is, the actual contour line, and the contour line of the above-mentioned end mill in an ideal shape, that is, the ideal contour line when the above-mentioned end mill is held in the above-mentioned tool holding portion; a position offset correction portion, the position offset correction portion calculates the position offset of the contour line of the above-mentioned end mill with the center of the above-mentioned hemispherical shape as a reference a correction value for correcting the positional deviation between the ideal contour line and the actual contour line in a plurality of angular directions, and further correcting the positional deviation of the end mill based on the calculated correction value; and a distance effect coefficient calculation unit that calculates a first distance effect coefficient indicating the magnitude of the influence of the positional deviation when machining the second machining point based on the distance between the end mill and the second machining point when machining the machining point by the end mill transitions from single-point machining of a first machining point on a first machining surface of the workpiece to two-point machining of the first machining point and a second machining point on a second machining surface different from the first machining surface. The positional deviation correction unit corrects the positional deviation of the first machining point based on the correction value when machining the single-point machining by the end mill, and corrects the positional deviation based on the correction value at the first machining point and the first distance effect coefficient when the distance between the end mill and the second machining point comes within a predetermined distance during the transition from the single-point machining to the two-point machining.

[0013] According to the workpiece machining method and workpiece machining apparatus of the present invention, the workpiece can be machined with high precision even when the workpiece is machined at multiple points by a ball end mill. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A block diagram schematically showing the configuration of a workpiece processing apparatus according to an embodiment.

[0015] Figure 2 This is an explanatory diagram showing a state in which a workpiece is machined by a tool (a ball end mill).

[0016] Figure 3 (a) is an explanatory diagram showing the contour error of the actual contour line of a stationary tool relative to the ideal contour line, Figure 3 (b) is an explanatory diagram showing a contour error between an actual contour line and an ideal contour line when an actual tool is rotated.

[0017] Figure 4 It is an explanatory diagram showing the contour error generated at each angle of the tool.

[0018] Figure 5 This is an explanatory diagram showing a situation in which a tool moves along a machining path of a workpiece.

[0019] Figure 6 It is a diagram showing an equation of coordinates of a machining position depending on a tool, and shows the coordinates of a machining position without correction based on a contour error.

[0020] Figure 7 : is a diagram showing an equation of coordinates of a machining position depending on a tool, and shows coordinates of the machining position after correction based on a contour error.

[0021] Figure 8 This is an illustration showing the machining position of the workpiece by the tool when switching from one-point machining to two-point machining. Figure 8 (a) shows the situation when the tool approaches the processing point Tt1. Figure 8 (b) shows the cutting condition when the tool reaches the processing point Tt1. Figure 8 (c) shows the correction situation for avoiding cutting in, Figure 8 (d) shows the specific correction status.

[0022] Figure 9 (a) Figure 9 (b) shows the implementation Figure 8 (d) is a diagram showing the position coordinates of the tool during correction.

[0023] Figure 10 (a)~ Figure 10 (c) is an explanatory diagram showing a machining point of a workpiece when a contour error occurs in the tool.

[0024] Figure 11 (a) Figure 11 (b) is an explanatory diagram showing a machining position depending on the tool when the actual contour line of the tool protrudes from the ideal contour line.

[0025] Figure 12 These are explanatory diagrams showing machining conditions when the actual contour line of the tool coincides with the ideal contour line, when the actual contour line is smaller than the ideal contour line, and when the actual contour line is larger than the ideal contour line.

[0026] Figure 13 It is a graph showing the relationship between the ideal value and the actual value of the distance between the tool and the workpiece. Sa indicates when the actual contour line is consistent with the ideal contour line, Sb indicates when the actual contour line is smaller than the ideal contour line, and Sc indicates when the actual contour line is larger than the ideal contour line.

[0027] Figure 14 It is corrected by using the distance effect coefficient Figure 13The graphs following the graphs of Sa, Sb, and Sc are shown.

[0028] Figure 15 It is a graph showing the relationship between the distance Da from the processing point and the distance effect coefficient Ed.

[0029] Figure 16 It's a contrast Figure 14 and Figure 15 The graph shown is the graph shown.

[0030] Figure 17 It is an explanatory diagram showing the positional relationship between the tool and the workpiece when the machining point by the tool shifts from the first machining surface M1 to the second machining surface M2.

[0031] Figure 18 This is a diagram showing an equation for correcting the coordinates of the machining position of the tool using the distance effect coefficient.

[0032] Figure 19 is Figure 18 The diagram shows an equation obtained by substituting specific numerical values ​​of the distance effect coefficient into the equation shown.

[0033] Figure 20 This is a flowchart showing the processing procedure of correcting an NC program in the workpiece machining apparatus according to the first embodiment.

[0034] Figure 21 This is an explanatory diagram showing a situation when the contour error of the tool is set in units smaller than 1°.

[0035] Figure 22 (a)~ Figure 22 (c) is an explanatory diagram showing a machined surface on which three-point machining is performed on three surfaces of a workpiece.

[0036] Figure 23 (a) shows Figure 22 An explanatory diagram of a plane S including the normal line of the first processed surface and the normal line of the second processed surface among the three surfaces shown in (c), Figure 23 (b) is an explanatory diagram showing a state in which the tool is corrected based on the movement vector on the plane S.

[0037] Figure 24 (a) Figure 24 (b) is an explanatory diagram showing the deviation between the tool and the third machined surface when the tool is corrected based on the movement vector.

[0038] Figure 25 Is to show the correction Figure 24 (b) is an explanatory diagram of the diverging vector shown.

[0039] Figure 26 (a) Figure 26 (b) is an explanatory diagram showing a correction vector VcA3 when the tool cuts into the third machined surface based on the contour error of the tool.

[0040] Figure 27 (a) Figure 27 (b) is an explanatory diagram showing a method of calculating a correction vector perpendicular to the plane S.

[0041] Figure 28 (a)~ Figure 28 (c) is an explanatory diagram showing correction when the tool cuts into the third machined surface.

[0042] Figure 29 This is a diagram showing an equation of a correction vector for eliminating the penetration into the third machined surface caused by the correction processing of the first machined surface and the second machined surface.

[0043] Figure 30 It is a diagram showing the formula of the correction vector of the third processing surface.

[0044] Figure 31 It shows that Figure 30 The graph of the formula obtained by expanding a part of the terms shown in formula (12).

[0045] Figure 32 It shows that Figure 31 The graph of the formula obtained by expanding a part of the terms shown in formula (13).

[0046] Figure 33 This is a diagram showing an equation obtained by expanding the X, Y, and Z coordinates of the final correction vector.

[0047] Figure 34 : is a diagram showing the equation for collecting the final correction vector. DETAILED DESCRIPTION

[0048] Hereinafter, a workpiece processing method and a workpiece processing apparatus according to embodiments will be described with reference to the drawings.

[0049] [Description of the First Embodiment]

[0050] Figure 1 1 is an explanatory diagram schematically showing the structure of a workpiece processing apparatus 1 (hereinafter referred to as "processing apparatus 1") that uses the processing method according to the first embodiment. Figure 1 As shown, the processing device 1 includes: a bed 19 serving as a base; a work table 21 provided on the upper surface of the bed 19; a column 23 that is in an inverted U shape when viewed from the front and is arranged in a manner that spans the bed 19 from the side of the bed 19; and a spindle support body 25 arranged near the upper center of the column 23.

[0051] In the following, one direction defined on the upper surface of the bed 19 is referred to as the X-axis direction (front-back direction), the direction on the upper surface of the bed 19 that is perpendicular to the X-axis direction is referred to as the Y-axis direction (left-right direction), and the direction perpendicular to the upper surface of the bed 19 (i.e., the normal direction) is referred to as the Z-axis direction. The X-axis, Y-axis, and Z-axis form an orthogonal coordinate system.

[0052] The worktable 21 includes a workpiece holder 7. The workpiece holder 7 secures the workpiece 5 to be processed by the processing apparatus 1. The worktable 21 is supported on the bed 19 via linear guide bearings (not shown) and is movable in the X-axis direction relative to the bed 19 by an actuator (not shown), such as a linear motor. Specifically, by controlling the worktable 21, the workpiece 5 can be positioned at a desired position on the X-axis on the bed 19.

[0053] The column 23 is formed integrally with the bed 19. A frame-shaped spindle support 25 is provided near the center of the upper portion of the column 23. A spindle frame 27 is provided on the lower surface of the spindle support 25.

[0054] A spindle 29 for fixing and rotating a ball end mill 3 (end mill, hereinafter referred to as "tool") having a hemispherical lower end is provided at an appropriate position on the lower surface of the spindle frame 27 .

[0055] The spindle 29 is provided with a tool holder 9, which allows the tool 3 to be attached and detached. This allows the desired tool to be attached depending on the type of workpiece 5 being machined. The tool 3 is positioned at a desired position in the Z-axis direction of the spindle 29. Furthermore, the spindle 29 is movable in the Z-axis direction. Therefore, the Z-axis position of the tool 3 can be adjusted by controlling the spindle 29.

[0056] The spindle frame 27 is supported on the spindle support 25 via linear guide bearings (not shown). Therefore, the tool 3 can be moved in the Y-axis direction by an actuator (not shown), such as a linear motor. In other words, by controlling the spindle frame 27, the tool 3 can be positioned at a desired position on the Y-axis.

[0057] Thus, by controlling the movement of the table 21, the spindle frame 27, and the spindle 29, the three-dimensional relative position of the workpiece 5 and the tool 3 can be set. In other words, the tool 3 can be brought into contact with a desired processing portion of the workpiece 5 to perform cutting processing on the workpiece 5.

[0058] Figure 2 3 is an explanatory diagram showing the state of contact between the tool 3 and the workpiece 5 during cutting. Figure 2 As shown, the tool 3 has a shape that is line-symmetrical about the center line C1 (center axis) as the rotation axis when viewed from the side during rotation.

[0059] The tool 3 is provided with a cutting edge portion (not shown) on the outer periphery of the tip portion 17, and the cutting edge portion can cut the workpiece 5. The center of the hemispherical shape of the end mill 3 is denoted by C2.

[0060] The upper end of the tool 3 ( Figure 2 The tool 3 held by the tool holding portion 9 is rotated about the center line C1 in the Z-axis direction, and the workpiece 5 is cut by the cutting edge portion.

[0061] like Figure 1 As shown, the machining apparatus 1 includes a control unit 13 that performs overall control of the machining apparatus 1 including movement control of the table 21, the spindle housing 27, and the spindle 29. The control unit 13 includes a positional deviation detector 131 and a memory 14 for storing various data.

[0062] The control unit 13 controls the movement of the table 21 to which the workpiece 5 is fixed and the spindle 29 to which the tool 3 is fixed, based on an NC program. It also controls the rotation of the tool 3. The control unit 13 can be configured as an integrated computer including, for example, a central processing unit (CPU) and storage devices such as RAM, ROM, and a hard disk.

[0063] The NC program is set by the CAM 39 based on the CAD data 37 of the workpiece 5. The NC program sets a machining path 41 for moving the tool 3 relative to the workpiece 5 and the three-dimensional coordinates of the machining path 41. The NC program set by the CAM 39 is sent to the computer 33.

[0064] like Figure 1 As shown, the machining apparatus 1 includes a tool shape measuring device 31 for measuring the shape of the tool 3. The tool shape measuring device 31 is, for example, a laser measuring device that irradiates the tool 3 with laser light from the side and measures the shape of the tool 3 by receiving the irradiated laser light. The positional deviation detecting unit 131 calculates the contour line of the tool 3 (referred to as "actual contour line P3") based on the shape of the tool 3 measured by the tool shape measuring device 31.

[0065] Specifically, the positional deviation detection unit 131 detects the positional deviation between the actual contour line (i.e., the contour line of the tool 3) when the tool 3 is held in the tool holding unit 9 and the ideal contour line (i.e., the ideal contour line P1) of the tool 3 in its ideal shape. Specifically, the unit calculates contour error correction values ​​to correct the positional deviation between the ideal contour line P1 and the actual contour line P3 in multiple angular directions relative to the center of the hemispherical shape of the tip of the tool 3. The calculated correction values ​​are stored in the memory 14.

[0066] The computer 33 includes a calculation unit 33a. The calculation unit 33a performs processing to correct the machining path 41 included in the NC program when the tool 3 cuts the workpiece 5. Specifically, the calculation unit 33a of the computer 33 obtains the NC program including the machining path 41 through the CAM 39 and, based on the correction values ​​obtained through a calculation process described later, corrects the three-dimensional coordinates of the machining path 41. The calculation unit 33a of the computer 33 corrects the NC program based on the correction values. The tool 3 then cuts the workpiece 5 according to the corrected machining path 43. More specifically, the calculation unit 33a includes a position offset correction unit 331, a distance effect coefficient calculation unit 332, and a storage unit 333.

[0067] When the machining point of the tool 3 transitions from one-point machining of a first machining point on a first machining surface of the workpiece 5 to two-point machining of the first machining point and a second machining point on a second machining surface different from the first machining surface, the distance effect coefficient calculation unit 332 calculates a distance effect coefficient indicating the magnitude of the influence of positional deviation during machining of the second machining point based on the distance between the tool 3 and the second machining point. The distance effect coefficient calculation unit 332 stores the calculated distance effect coefficient in the storage unit 333.

[0068] The position offset correction unit 331 corrects the NC program based on the contour error correction value stored in the memory 14 of the control unit 13 and the distance effect coefficient stored in the storage unit 333 of the calculation unit 33a. When performing one-point machining with the tool 3, the position offset correction unit 331 corrects the position offset of the first machining point based on the contour error correction value. When transitioning from one-point machining to two-point machining, and when the distance between the tool 3 and the second machining point is within a specified distance, the position offset is corrected based on the contour error correction value at the first machining point and the distance effect coefficient. In this way, the NC program is corrected based on the contour error correction value and the distance coefficient.

[0069] Next, a description will be given of a process for correcting the positional deviation between the ideal contour line P1 of the tool 3 and the actual contour line P3 of the tool 3 .

[0070] When the tool 3 is actually machining the workpiece 5, as previously described, positional deviation occurs when the tool 3 is fixed to the spindle 29. Furthermore, the tool 3 exhibits shape errors. Consequently, an error (referred to as "profile error") occurs between the ideal contour line P1 and the actual contour line P3. This profile error causes an error in the machining position of the workpiece 5, reducing machining accuracy. In the first embodiment, a process is implemented to correct the profile error generated by the tool 3. This is described in detail below.

[0071] Figure 3 (a) Figure 3(b) is an explanatory diagram showing the outer shape of the tool 3. Figure 3 In (a), the dotted curve (symbol P1) is the outer shape of the tool 3 in an ideal shape at rest, and the solid curve (symbol P2) is the outer shape of the tool 3 in an ideal shape with shape errors at rest. The outer shape of the tool 3 in an ideal shape is defined as the ideal contour line P1, and the outer shape of the end mill with shape errors is defined as the contour line P2. Figure 3 As shown in (a), the contour line P2 is located slightly to the right of the center line C1 relative to the ideal contour line P1. Figure 3 In (a), the deviation between the ideal contour line P1 and the contour line P2 is exaggerated.

[0072] exist Figure 3 In (b), the dotted curve (symbol P1) represents the contour line when the ideal shape tool 3 is rotated along the center line C1 (corresponding to Figure 3 The solid line curve (symbol P3) represents the contour line when the tool 3 with shape error is rotated along the center line C1 (this is set as the actual contour line P3). Figure 3 The contour line P2 shown in (a) deviates from the ideal contour line P1, so the radius of the actual contour line P3 is larger than that of the ideal contour line P1. Figure 3 (b) is an example, and the actual contour line P3 may be smaller than the ideal contour line P1.

[0073] In the first embodiment, the difference between the ideal contour line P1 and the actual contour line P3, that is, the contour error, is calculated, and the calculated contour error data is stored as a correction value in the Figure 1 The memory 14 is shown. This process is performed by Figure 1 The calculation method of the contour error is described below.

[0074] [Calculation of contour error]

[0075] like Figure 2 As shown, the workpiece 5 is processed by the front end 17 of the tool 3, so the contour error of the tool 3 is as follows Figure 4 As shown, the calculation may be performed based on a quarter of the arc of the distal end portion 17 (ie, within a range of an angle of 90°).

[0076] Specifically, the center line C1 of the ideal contour line P1 is used as the center, and the difference between the arc of the ideal contour line P1 (the arc of 1 / 4 circle) and the arc of the actual contour line P3 (the arc of 1 / 4 circle) is calculated as the contour error. And, the contour error is stored in Figure 1 The memory 14 is shown.

[0077] As an initial process for calculating the correction value, a tool shape measuring device 31 (see Figure 1 ) to measure the shape of the tool 3. Here, an example in which a laser measuring device is used as the tool shape measuring device 31 will be described.

[0078] The laser measuring device irradiates the laser from the side of the tool 3 and measures the shape of the tool 3 by receiving the irradiated laser. Figure 3 As shown in (a), the contour line P2 of the tool 3 is obtained, and then the Figure 3 The actual contour line P3 shown in (b) of FIG. 1 can also be read from the memory 14 of the control unit 13 .

[0079] The position of the tool 3 is corrected based on the machining point T1 machined by the tool 3 (see Figure 2 The three-dimensional position of tool 3 is corrected in at least one of the X-axis, Y-axis, and Z-axis directions. The directions of the X-axis, Y-axis, and Z-axis are determined by the unit normal vector V1 (described later in detail) and the contour error of tool 3.

[0080] Figure 4 : is an explanatory diagram showing the relationship between the angle (0° to 90°) of the arc of the tool 3 and the correction value for correcting the contour error. Figure 4 In FIG, the ideal contour line P1 and the actual contour line P3 of the tool 3 are shown. Figure 4 In the example, the vertical direction is set to an angle of 0° and the horizontal direction is set to an angle of 90°. Figure 4 As an example, the following shape is shown: within the range of 0° to 45° based on the center line C1 of the arc, the actual contour line P3 protrudes outward compared to the ideal contour line P1, and within the range of 45° to 90°, the actual contour line P3 is recessed compared to the ideal contour line P1.

[0081] And, as Figure 4 As shown, ten straight lines L00 to L90 extending from the centerline C1 of the arc toward the outer shape of the 90° arc of tool 3 are set at 10° intervals. The straight lines are set at 10° intervals. The intersection angle between the centerline C1 of tool 3 and straight line L00 is 0°. In other words, straight line L00 and centerline C1 are parallel (colinear).

[0082] The intersection angle between center line C1 and straight line L10 is 10°. Similarly, the intersection angles between center line C1 and straight lines L20 to L90 are 20° to 90°. Specifically, the direction parallel to center line C1 is 0°, and the direction perpendicular to center line C1 is 90°. Multiple straight lines are set at 10° intervals.

[0083] Here, the intersection point between straight line L00 and ideal contour line P1 is defined as intersection point Q00a. Similarly, the intersection points between straight lines L10, L20, ..., and L90 and ideal contour line P1 are defined as intersection points Q10a, Q20a, ..., and Q90a, respectively. Meanwhile, the intersection points between straight lines L00, L10, L20, ..., and L90 and actual contour line P3 are defined as intersection points Q00b, Q10b, Q20b, ..., and Q90b, respectively. Therefore, since the distance (i.e., the difference) between two intersection points on each straight line represents the contour error, this value is set as the "correction value." For example, for straight line L10, "Q10b - Q10a" is set as the correction value.

[0084] Furthermore, the correction values ​​of each angular direction are set as reference symbols #500, #510, ··, #590 and stored in Figure 1 Specifically, let "#500 = Q00b - Q00a", let "#510 = Q10b - Q10a", and similarly let "#590 = Q90b - Q90a" be used hereinafter.

[0085] In addition, Figure 4 To avoid complexity, the example in which correction values ​​are calculated for straight lines L00, L10, ..., L90 at 10° intervals is shown. However, in practice, correction values ​​are set at smaller intervals (e.g., every 1°). Therefore, correction values ​​for every 1° interval are stored in memory 14 as reference symbols #500, #501, #502, ..., #589, and #590.

[0086] That is, from Figure 4 From the center line C1 of the ideal contour line P1 shown, straight lines L00 to L90 are drawn at angles of 1° each, and correction values ​​are calculated for each straight line. The calculated correction values ​​are stored in the memory 14 as reference symbols #500, #501, #502, ..., #589, and #590. The three-dimensional coordinates of the NC program are then corrected using the reference symbols #500 to 590 calculated through this correction process.

[0087] Next, a description will be given of a process of correcting the three-dimensional coordinates of the NC program using the above-mentioned correction values.

[0088] [Correction of three-dimensional coordinates]

[0089] Initially, based on the aforementioned Figure 1 The CAD data (data representing the shape of the workpiece 5 as a finished product) 37 shown and the NC program produced by CAM39, that is, the NC program when the workpiece is processed by the end mill 3 of the ideal shape, calculate the unit normal vector V1 at the desired processing point (set to T1) of the workpiece 5.

[0090] Figure 5 3 is an explanatory diagram showing the movement of the tool 3 according to the machining path when the tool 3 is machining the workpiece 5. Figure 5 As shown, when the tool 3 cuts the workpiece 5, the point where the tool 3 and the workpiece 5 come into contact becomes the machining point T1 of the workpiece 5. Then, the unit normal vector at the machining point T1 is calculated (denoted as V1).

[0091] This processing is performed, for example, by the calculation unit 33a of the computer 33 (see Figure 1 The three-dimensional coordinates of the processing point T1 can be obtained through the NC program, or when an ideal tool (ball end mill) is installed, it can be obtained by actually moving the tool according to the processing path.

[0092] When the tool 3 cuts the workpiece 5, the tool 3 moves relative to the workpiece 5 in at least one of the X-axis, Y-axis, and Z-axis directions.

[0093] The surface of the workpiece 5 centered at the machining point T1 is either a flat surface or a curved surface. However, if limited to an extremely small area, even a curved surface in that area can be considered a flat surface.

[0094] The unit normal vector V1 is a vector perpendicular to the aforementioned small region (plane) and has components in the X-axis, Y-axis, and Z-axis directions. The scalar value of the unit normal vector V1 is naturally "1." In other words, if the values ​​of the X-axis, Y-axis, and Z-axis components of the unit normal vector V1 are multiplied by themselves, the sum of the values, and the square root (root) is calculated, the value is "1."

[0095] Furthermore, in the first embodiment, the correction values ​​(differences between the ideal contour line P1 and the actual contour line P3) stored as the aforementioned reference symbols #500, #501, ··, #589, and #590 are set as offsets in each angular direction. Furthermore, the unit normal vector V1 is decomposed into components in the three-dimensional directions of the X-axis, Y-axis, and Z-axis as a vector, and the offsets in each direction are calculated. Figure 6 、 Figure 7 The formula shown is explained in detail.

[0096] Figure 6 The three-dimensional coordinates of the position where tool 3 performs cutting work are shown when the tool 3 moves in the order of machining points f51, f52, f53, f54, and f55. These three-dimensional coordinates represent the coordinates when tool 3 is in an ideal shape. In other words, they represent the three-dimensional coordinates of the machining path initially set in the NC program.

[0097] Furthermore, in the first embodiment, the three-dimensional coordinates of the machining path are corrected based on the unit normal vector V1 and the aforementioned reference symbols. Figure 6 The coordinates of the processing points f51, f52, f53, f54, and f55 shown are corrected to Figure 7 The coordinates of the processing points f61, f62, f63, f64, and f65 are shown. Figure 7 The calculation formula shown is stored in the memory 14, and the coordinates of the processing point T1 are corrected using this calculation formula.

[0098] Specifically, for example, Figure 6 The three-dimensional coordinates of the machining point f51 are shown as X=-1.60657, Y=-0.42583, and Z=-1.09809. On the other hand, the coordinates of the actual contour line P3 when it deviates from the ideal contour line P1 are corrected to Figure 7 The processing point f61 is shown.

[0099] Processing points f51 and f61 are Figure 4 The angle of the tool 3 shown is 64 degrees. Therefore, the correction value stored as reference symbol #564 is read from the memory 14, and then, based on the above-mentioned unit normal vector, the correction value is decomposed in each direction of the X axis, Y axis, and Z axis, and the correction value of each axis direction is calculated. And, based on the correction value, the three-dimensional coordinates of the processing point f51 before correction are corrected to calculate Figure 7 The three-dimensional coordinates of the processing point f61 are shown.

[0100] The following, Figure 7 The calculation formula for processing point f61 shown in FIG. By decomposing the unit normal vector V1 at processing point f61 into its X-axis, Y-axis, and Z-axis components, for example, (X, Y, Z) = (-0.89101, 0.11528, -0.4391) can be obtained. Since the angle at the processing point is 64°, the correction value stored as reference symbol #564 is used.

[0101] That is, in Figure 7In the equation shown in "f61," the X-coordinate correction value, [-0.89101 × #564], is the value obtained by multiplying the correction value set as reference symbol #564 by "-0.89101," which is the X-axis component of unit normal vector V1. Furthermore, the Y-coordinate correction value, [0.11528 × #564], is the value obtained by multiplying the correction value set as reference symbol #564 by "0.11528," which is the Y-axis component of unit normal vector V1. The Z-coordinate correction value, [-0.4391 × #564], is the value obtained by multiplying the correction value set as reference symbol #564 by "-0.4391," which is the Z-axis component of unit normal vector V1.

[0102] therefore, Figure 7 The three-dimensional coordinates of the processing point f61 are the coordinates reflecting the correction value based on the contour error. By driving the tool 3 based on the coordinates to perform cutting, even if a contour error occurs between the ideal contour line P1 and the actual contour line P3, the influence of the contour error can be avoided and high-precision cutting can be performed. Figure 6 The three-dimensional coordinates of the processing point f51 shown are corrected to Figure 7 The three-dimensional coordinates of the processing point f61 shown enable a desired portion of the tool 3 to contact the processing point on the workpiece 5 , thereby performing cutting processing on the workpiece 5 .

[0103] [Amount to avoid]

[0104] By correcting the contour error as described above, the tool 3 may sometimes come into contact with a point (contact point) of the workpiece 5 other than the processing point, and at this contact point, the tool 3 cuts into and processes the workpiece 5. In this case, it is necessary to avoid contact between the tool 3 and the contact point. Figure 8 (a)~ Figure 8 (d) Figure 9 (a) Figure 9 (b) is described in detail.

[0105] Figure 8 The line indicated by the two-dot chain line in (a) shows the contour line of the tool 3 having an ideal shape with no contour error. Figure 8 The solid line in (a) shows the contour of the tool 3 having a contour error.

[0106] When machining by tool 3 Figure 8 When machining point Tt1 shown in (a), if no contour error occurs, that is, if it is an ideal shape, the tool 3 is in contact with the machining point Tt1 to perform cutting. Figure 8When a contour error occurs as shown by the solid line in (a), the machining position of the tool 3 is corrected based on the correction value described above.

[0107] Therefore, if Figure 8 As shown in (b), correction is performed so that the lower end of the tool 3, which has a contour error, contacts the machining point. As a result, the tool 3 contacts the inclined surface of the workpiece 5 at contact point Tt2, causing a cut (bite) 45. If cutting is performed in this state, the workpiece 5 will be overcut.

[0108] In the first embodiment, in order to avoid unnecessary cutting due to the interference, as shown in FIG. Figure 8 As shown in (c), the position of the tool 3 is corrected. Specifically, Figure 8 As shown in (d) of FIG. 1 , a vector VA is calculated that lies on the plane defined by the unit normal vectors of the machining point Tt1 and the contact point Tt2 and is orthogonal to the unit normal vector VB of the machining point Tt1. This vector VA is set as the avoidance vector. Furthermore, by correcting the machining position of the tool 3 using this avoidance vector VA, penetration 45 into the contact point Tt2 is avoided.

[0109] That is, by performing a correction by withdrawing the avoidance amount VA in a direction perpendicular to the normal line of the processing point Tt1, the penetration 45° can be avoided. The avoidance amount VA can be calculated as (correction amount VB of processing point Tt1 × tanθ). "θ" is the intersection angle between the normal line of processing point Tt1 and the plane in contact with the contact point Tt2 (the plane that includes processing point Tt1 and is perpendicular to the normal line of contact point Tt2).

[0110] To further illustrate, the coordinates of tool 3 in the X-axis direction, Y-axis direction, and Z-axis direction are given by Figure 9 The sum of the numerical values ​​shown in (1) and (2) of (a) is expressed.

[0111] The coordinate value of tool 3 in the X direction is given by Figure 9 The coordinate value (calculation formula) f111 of (b) indicates that "0.123" in the coordinate value f111 is the coordinate value of the tool 3 in the X-axis direction before correction (when no contour error correction is performed).

[0112] In addition, at the coordinate value f111, the reference symbol "#513" shown in "correction amount of machining point Tt1" is the same as the one mentioned above. Figure 4 The following describes the correction value of the contour error (scalar) at the machining point Tt1 of the tool 3. The "0.216" at the coordinate value f111 is the X-direction component of the unit normal vector at the machining point Tt1.

[0113] At the coordinate value f111, the reference symbol "#513" shown in "Avoidance of machining point Tt1" is used Figure 4 The correction value for the contour error (scalar) at machining point Tt1 of tool 3 is described below. The "-0.816" at coordinate value f111 is the X-direction component of the avoidance vector (unit vector) at machining point Tt1. The "0.613" at coordinate value f111 is the value of tanθ mentioned above. The same applies to the components in the Y- and Z-directions.

[0114] When the above-mentioned coordinate value f111 is generally expressed, it becomes the following formula (1).

[0115] X coordinate = Px + (i1 × #50A + i11 × #50A × tanθ)

[0116] Y coordinate = Py + (j1 × #50A + j11 × #50A × tanθ)

[0117] Z coordinate = Pz + (k1 × #50A + k11 × #50A × tanθ) …(1)

[0118] [Operation when the processing point changes from 1-point processing to 2-point processing]

[0119] When machining, for example, the vicinity of a junction between two machined surfaces using the tool (ball end mill) 3 , the machining point may shift from one-point machining to two-point machining.

[0120] Figure 10 (a)~ Figure 10 (c) is an explanatory diagram showing the movement of the tool 3 when the tool 3 processes the first processing point T1 of the workpiece 5 and then switches to processing the second processing point T2. Figure 10 (a) shows the situation where the tool 3 processes the first processing point T1. Figure 10 (b) shows a state in which the tool 3 processes both the first processing point T1 and the second processing point T2, that is, a two-point processing state.

[0121] Contour errors occur in tool 3, such as Figure 10 In the case where the actual contour line H1 (solid line) protrudes relative to the ideal contour line H0 (dashed line) as shown in (c), if processing based on the NC program is performed, then when only one-point processing of the first processing point T1 is performed, that is, before the transition to two-point processing, the tool 3 will contact the second processing point T2, and the tool 3 will cut into the workpiece 5.

[0122] For example, Figure 11 As shown in (a), in the NC program, when the distance between the tip of the tool 3 and the second processing point T2 is 7 μm, when the error of the tip of the tool 3 is 2 μm (when it protrudes 2 μm), the distance between the tool 3 and the second processing point T2 becomes 5 μm. Figure 11 As shown in (b), if the error of the tip of the tool 3 exceeds 7 μm, the tip of the tool 3 will come into contact with the workpiece 5 and cut into it.

[0123] Therefore, when switching from single-point machining at the first machining point T1 to two-point machining at the first machining point T1 and the second machining point T2 , the position of the tool 3 needs to be corrected in consideration of the tool 3 approaching the second machining point T2 .

[0124] In the first embodiment, after machining the first machining point T1 with the tool 3, when the tool 3 then transitions to machining two machining points, T1 and T2, a correction value is calculated based on the distance (approach distance) between the tool 3 and the second machining point T2. Specifically, a coefficient (referred to as the "first distance effect coefficient Ed") that changes according to the distance between the tool 3 and the second machining point T2 is set, and the machining position of the tool 3 is corrected based on this first distance effect coefficient Ed. The first distance effect coefficient Ed is a value between 0 and 1.

[0125] [Explanation of the first distance effect coefficient Ed]

[0126] Next, the first distance effect coefficient Ed will be described. Figure 12 1 and 2 are explanatory diagrams showing machining of a workpiece 5 by an ideal contour line q1 (dashed line) and an actual contour line q2 (solid line) of a tool 3 . Figure 12 (a1) indicates that the ideal contour line q1 is consistent with the actual contour line q2. Figure 12 (a2) indicates that the actual contour line q2 is smaller than the ideal contour line q1 (for example, 5 μm smaller). Figure 12 (a3) is a case where the actual contour line q2 is larger than the ideal contour line q1 (for example, larger by 5 μm).

[0127] And, if by having Figure 12 The tool 3 with the actual contour line q2 of the shape shown in (a1) to (a3) ​​is used to machine the machining surface M11 of the workpiece, and the result is Figure 12 Specifically, Figure 12 As shown in (a1), when the ideal contour line q1 and the actual contour line q2 are consistent, as shown in Figure 12 As shown in (b1), the tool 3 is in contact with the processing point on the processing surface M11. Figure 12 As shown in (a2), when the actual contour line q2 is smaller than the ideal contour line q1, as shown in Figure 12 As shown in (b2), the tool 3 cannot reach the processing point on the processing surface M11. Figure 12As shown in (a3), when the actual contour line q2 is larger than the ideal contour line q1, as shown in Figure 12 As shown in (b3), the tool 3 cuts inward from the processing point of the processing surface M11.

[0128] If the relationship between the distance between the tool 3 and the workpiece 5 (machined surface M11) at this time is shown in a graph, it becomes Figure 13 Like that. Figure 13 In FIG. 5 , the horizontal axis represents the ideal value of the distance between the tool 3 and the workpiece 5, and the vertical axis represents the actual distance (actual value) between the tool 3 and the workpiece 5. Figure 12 When the tool 3 is an ideal contour line as shown in (a1), the curve Sb is as follows: Figure 12 When the actual contour of the tool 3 is small as shown in (a2), the curve Sc represents Figure 12 When the actual outline of the tool 3 is large as shown in (a3).

[0129] If the curves Sb and Sc are corrected so as to be close to the curve Sa, the contour error of the tool 3 relative to the machined surface M11 can be corrected. Figure 14 As shown in FIG. 1 , the following first distance effect coefficient Ed is set: the contour error is gradually reduced according to the distance between the tool 3 and the processing surface M11. When the distance between the tool 3 and the processing surface M11 becomes zero, the contour error is zero. Then, by multiplying the contour error (correction value) by the first distance effect coefficient Ed, the correction value is changed so as to become Figure 14 Curves Sb1 and Sc1.

[0130] At this time, in order to generate the curves Sb1 and Sc1 from the curves Sb and Sc, the first distance effect coefficient Ed is calculated based on the following formula (2).

[0131] Ed=1.25exp(-10 6 ·Da 3 -300·Da) …(2)

[0132] In formula (2), "Da" represents the distance between the ideal tool 3 and the machined surface M11, and "exp" represents an exponential function. The calculation formula shown in formula (2) is an example, and the first distance effect coefficient Ed can also be calculated using other calculation formulas.

[0133] If the above formula (2) is expressed by a curve, it becomes Figure 15 As shown in the curve F1. Figure 15In the figure, the horizontal axis represents the ideal distance Da between tool 3 and workpiece 5, and the vertical axis represents the first distance effect coefficient Ed. As can be understood from curve F1, the first distance effect coefficient Ed varies within the range of "0-1", with the rate of change (the slope of the curve) increasing as the distance between tool 3 and workpiece 5 decreases.

[0134] By considering the first distance effect coefficient Ed, even if an error occurs between the tool 3 and the machining surface M11 of the workpiece 5, the correction value is gradually changed according to the approach distance so that the tool 3 is in contact with the machining surface M11. Therefore, a sharp change in the correction value of the tool 3 when switching from one-point machining to two-point machining is avoided.

[0135] To explain in more detail, when tool 3 is machining surface M11 of workpiece 5, based on the pre-measured profile error of tool 3, if, for example, the diameter of tool 3 is 5 μm smaller than the ideal value, "+0.005" is stored in reference symbol #50A. Alternatively, if the diameter of tool 3 is 5 μm larger than the ideal value, "-0.005" is stored in reference symbol #50A. Furthermore, "#50A" refers to the angle (0° to 90°) between machining point T1 and machining surface M11, where machining point T2, among the aforementioned #500 to #590, contacts the angle. For example, if it is 1°, "#501" is stored.

[0136] And, if you refer to Figure 15 As shown in the curve F1, when Da = 0, that is, when the tool 3 contacts the machining point T2 to machine the workpiece 5, Ed = 1. Therefore, when the tool 3 is 5 μm larger than the ideal value, the correction value is -5 μm.

[0137] When Da = 10 μm, Ed = 0.4096. When the tool 3 is 5 μm larger than the ideal value, the correction value becomes -2.048 μm (refer to Figure 14 ).

[0138] When Da=3μm, Ed=0.81314. When the tool 3 is 5μm larger than the ideal value, the correction value becomes -4.066μm (refer to Figure 14 ).

[0139] In particular, in the case of Da = 3 μm, if the tool 3 is 5 μm larger than the ideal value, without correction, "3 - 5 = -2," resulting in a 2 μm undercut. However, by multiplying by the first distance effect coefficient Ed, a correction of -4.066 μm is achieved, thus avoiding undercutting.

[0140] Preferably, the first distance effect coefficient Ed is set so that the inclination increases as the distance approaches zero. Specifically, Figure 16As shown, the inclination is set so that in the long distance region γ1 from the tool 3 to the workpiece 5, the inclination is small, the inclination gradually increases in the intermediate region β1, and the change in inclination becomes even greater in the short distance region α1 from the machining point. In other words, the first distance effect coefficient Ed changes so that the rate of increase gradually increases as the distance from the specified distance approaches the second machining point T2. This allows the influence of the first distance effect coefficient Ed to gradually increase.

[0141] [Coordinate calculation when switching from one-point machining to two-point machining]

[0142] Next, the correction of the coordinates of the tool 3 when the machining point of the workpiece 5 by the tool 3 is changed from one point to two points will be described. Figure 17 As shown, the correction of the X, Y, and Z coordinates of the tool 3 when the tool 3 approaches the second machining point T2 from the state where the tool 3 is machining the first machining point T1 in the workpiece 5 will be described.

[0143] Will Figure 17 The unit normal vector of the first processing point T1 on the first processing surface M1 shown is set to (i1, j1, k1), and the correction amount of the first processing point T1 is set to #50B. "#50B" refers to the angle (0° to 90°) corresponding to the first processing point T1 among the aforementioned #500 to #590. That is, it is the point and Figure 4 The angle of the straight line connecting the center C2 shown is based on the center line C1.

[0144] Furthermore, let the unit normal vector of the second machining point T2 on the second machining surface M2 be (i2, j2, k2), and the correction amount for the second machining point T2 be #50A. Similarly, "#50A" is the value of the angle (0° to 90°) corresponding to the second machining point T2 between #500 and #590.

[0145] In addition, the avoidance vector of the first processing point T1 is set to (i11, j11, k11), and the intersection angle between the normal line of the first processing point T1 and the plane connected to the second processing point T2 is set to "θ" (refer to Figure 8 ). In addition, the avoidance vector of the second processing point T2 is set to (i22, j22, k22).

[0146] Therefore, the corrected X coordinate, Y coordinate, and Z coordinate are as follows Figure 18 Calculate as shown in formula (3). Figure 18 In , Px, Py, and Pz represent the ideal values ​​of the three-dimensional coordinates. Figure 18In the figure, the first item r1 in parentheses represents the correction amount for the first processing point T1. The second item r2 represents the correction amount for the second processing point T2. The third item r3 represents the avoidance amount for the first processing point T1 (first avoidance amount). The fourth item r4 represents the avoidance amount for the second processing point T2 (second avoidance amount).

[0147] For example, when the distance between the tool 3 and the second processing point T2 is 10 μm, Figure 15 As shown in FIG, the first distance effect coefficient Ed = 0.4096. Therefore, Figure 18 The formula (3) shown becomes Figure 19 As shown in formula (4).

[0148] In this way, when the processing point of the tool 3 is changed from the one-point processing of the first processing point T1 to the two-point processing of the first processing point T1 and the second processing point T2, according to the distance when the tool 3 approaches the second processing point T2, as shown in FIG. Figure 15 The first distance effect coefficient Ed is changed as shown in the curve F1. Therefore, when switching from one-point machining to two-point machining, a sudden position change of the tool 3 due to correction can be avoided. Therefore, machining of the workpiece 5 by the tool 3 can be stably performed.

[0149] [Explanation of NC program correction processing]

[0150] Next, refer to Figure 20 The flowchart shown in FIG. 1 will be used to explain the processing procedure of the correction processing of the processing point by the processing device 1 according to the first embodiment. Figure 20 The processing shown is performed by Figure 1 The processing is executed by the control unit 13 and the calculation unit 33a of the computer 33. The processing shown below is stored in the computer 33 as a computer program.

[0151] At first, in Figure 20 In step S11 shown, by Figure 1 The CAM 39 shown creates an NC program that becomes a machining path for the tool 3. This machining path is a machining path when the tool 3 is accurately attached to the spindle 29 of the tool holding portion 9 and the tool 3 has no shape error.

[0152] In step S12 , the positional deviation detection unit 131 of the control unit 13 calculates the ideal contour line P1 of the tool 3 . The ideal contour line P1 can be read from the ideal tool dimensions stored in the memory 14 .

[0153] In step S13, the position deviation detecting unit 131 obtains the actual contour line P3 of the tool 3. Specifically, the position deviation detecting unit 131 obtains the actual contour line P3 of the tool 3. Figure 1The tool shape measuring device 31 shown in FIG. 1 irradiates laser light from the side of the tool 3, detects the laser light passing through the tool 3, and calculates the contour line P2. Therefore, the actual contour line P3 is calculated based on the contour line P2 (refer to FIG. 1 ). Figure 3 (a) Figure 3 (b)).

[0154] In step S14, the position deviation detection unit 131 calculates the correction value for each angular direction of the arc-shaped portion of the tool 3 based on the ideal contour line P1 and the actual contour line P3, and sets the calculated correction value as reference symbols #500 to 590 (refer to Figure 4 ).

[0155] In step S15, the position offset correction unit 331 of the calculation unit 33a calculates the unit normal vector V1 at the first machining point T1 of the workpiece 5 and corrects the coordinates of the machining point in the X-, Y-, and Z-axis directions using the correction values ​​stored in reference symbols #500 to #590. Specifically, the correction value, such as that set as reference symbol #564, is obtained based on the machining position angle (0° to 90°) where the tool 3 contacts the first machining point T1. The unit normal vector V1 is then decomposed into its components in the X-, Y-, and Z-axis directions. These components are then multiplied by the correction values ​​to correct the coordinates of the machining point in the X-, Y-, and Z-axis directions.

[0156] In step S16, the distance effect coefficient calculation unit 332 of the calculation unit 33a calculates the first distance effect coefficient Ed corresponding to the distance between the tool 3 and the second processing point T2. Specifically, based on Figure 15 The curve F1 shown is calculated for a first distance effect coefficient Ed (a numerical value of 0 to 1) which increases as approaching the second processing point T2.

[0157] In step S17, the position deviation correction unit 331 of the calculation unit 33a corrects the coordinates of the machining position of the tool 3 using the first distance effect coefficient Ed. Specifically, based on Figure 18 The formula (3) shown above corrects the X coordinate, Y coordinate, and Z coordinate depending on the machining position of the tool 3. Then, this process ends.

[0158] Thus, when transitioning from one-point machining to two-point machining, the coordinate values ​​in the NC program can be corrected to appropriate values ​​by setting a correction value corresponding to the distance between the tool 3 and the second machining point T2. Furthermore, by implementing control using the corrected NC program, the workpiece 5 can be machined stably.

[0159] [Description of Effects of the First Embodiment]

[0160] In this manner, in the workpiece machining apparatus 1 according to the first embodiment, the workpiece 5 is machined using the tool 3 (a ball end mill). When the machining point by the tool 3 shifts from single-point machining of the first machining point T1 to two-point machining of the first machining point T1 and the second machining point T2, the first distance effect coefficient Ed is calculated based on the distance when the tool 3 approaches the second machining point T2. Furthermore, the correction value based on the second machining point T2 is changed based on the first distance effect coefficient Ed.

[0161] Therefore, if the tool 3 approaches the second machining point T2, the correction value of the second machining point T2 is used to correct the machining position of the tool 3. Therefore, when switching from one-point machining to two-point machining, it is possible to avoid problems such as the tool 3 not reaching the second machining point T2 or cutting into the workpiece 5 from the second machining point T2.

[0162] Furthermore, in the workpiece machining apparatus 1 according to the first embodiment, when switching from one-point machining to two-point machining, abrupt contact with the second machining point T2 can be avoided. Therefore, stable machining of the workpiece 5 can be performed.

[0163] In addition, in the workpiece processing device 1 according to the first embodiment, as Figure 18 As shown, the calculation formula of the corrected machining path is stored in the memory 14, and the reference symbols #500 to #590 are substituted into the calculation formula to correct the three-dimensional coordinates. Therefore, the calculation load during machining can be reduced, and the time required for machining the workpiece 5 can be shortened.

[0164] In the first embodiment, the example in which the correction value is calculated every 1° in the range of 0 to 90° of the arc shape portion of the tool 3 is described. For example, Figure 21 As shown, at an angle of 63.9°, the correction value is calculated by allocating the adjacent reference symbols #563 of 63° and #564 of 64° at a ratio of 1 to 9. This method enables more accurate correction of machining points.

[0165] [Description of Second Embodiment]

[0166] Next, the second embodiment will be described. In the first embodiment, correction is described when performing two-point machining of a first machining point T1 on a first machining surface M1 and a second machining point T2 on a second machining surface M2 of a workpiece 5. In the second embodiment, three-point machining is described.

[0167] Figure 22 This is an explanatory diagram showing the structure of the workpiece processing surface when performing three-point processing. Assume the following shape: Figure 22As shown in (a), an uneven V-shaped cutting depth 52 is formed on a rectangular workpiece 51, and then as shown in Figure 22 As shown in (b), a flat plate 53 is inserted into the cutting depth 52 of the workpiece 51 from an inclined direction. Figure 22 As shown in (c) of FIG. 1 , the three surfaces surrounded by the cutting depth portion 52 and the flat plate 53 are designated as the first machining surface M1, the second machining surface M2, and the third machining surface M3, respectively. Furthermore, in the second embodiment, a correction value for the tool 3 is set when transitioning from two-point machining of machining points on the first machining surface M1 and the second machining surface M2 to three-point machining with the addition of machining points on the third machining surface M3 (third machining points). This will be described in detail below.

[0168] Initially, assuming two-point machining of the first machining surface M1 and the second machining surface M2, the machining position of the tool 3 is corrected using the method of the first embodiment. Next, a plane S (specified plane) is defined that passes through the machining points or near points of the first machining surface M1 and the second machining surface M2 and is defined by the unit normal vectors of the machining points of each machining surface M1 and M2. At this time, as Figure 23 As shown in (a), on the plane S, not only the unit normal vectors of the processing points of the first processing surface M1 and the second processing surface M2 but also the avoidance vectors of the processing points or the approach points are located.

[0169] That is, all the vectors for correcting the machining points of the first machining surface M1 and the second machining surface M2 exist on the plane S. In other words, the correction vector for correcting the first machining point T1 and the correction vector for correcting the second machining point T2 exist on the plane S. Therefore, Figure 23 As shown in (b), in the process of correcting the processing positions in the first processing surface M1 and the second processing surface M2, no matter how concave and convex the contour error of the tool 3 is, the movement vector (referred to as "movement vector Vc12") for correcting the final processing position that synthesizes all correction actions also exists on plane S.

[0170] Next, the machining of the third machined surface M3 by the tool 3 is taken into consideration. At this time, the following (A) and (B) need to be corrected.

[0171] (A) Conventional correction of the normal direction of the third processed surface M3.

[0172] (B) Elimination of insufficient cutting depth or insufficient cutting depth with respect to the third machined surface M3 caused by the correction operation of the first machined surface M1 and the second machined surface M2.

[0173] Figure 24 (a) is a plan view of the first to third processed surfaces M1 to M3 as viewed from the axial direction of the tool 3 . Figure 24The vector Vc12 shown in (a) represents Figure 23 The "movement vector Vc12" shown in (b) is along the plane S. Figure 24 The third processing surface M3 shown in (a) is set to an arbitrary direction Y1, and the diagram is viewed from the normal direction of the plane passing through the vertical direction of the direction Y1. Figure 24 (b). Figure 24 As shown in FIG. 5( b ), by moving the tool 3 along the movement vector Vc12 , a divergence vector Vne3 toward the normal direction of the third machined surface M3 is generated between the tool 3 and the third machined surface M3 .

[0174] Here, assuming the unit normal vector of the third machined surface M3 is Vun3, the deviation vector Vne3 can be calculated by taking the inner product of the movement vector Vc12 and the unit normal vector Vun3. In other words, it can be calculated as "Vne3 = Vc12·Vun3." Here, "·" represents the inner product of vectors. Furthermore, the direction of the deviation vector Vne3 is the same as that of the unit normal vector Vun3.

[0175] Furthermore, in an ideal state (a state where the movement vector Vc12 is zero), if the tool 3 is in contact with the third machined surface M3, the influence of the correction performed between the first machined surface M1 and the second machined surface M2 can be eliminated by moving the tool 3 in the opposite direction by the deviation vector Vne3. Figure 25 As shown, a vector VcB3 is set in the opposite direction away from the vector Vne3.

[0176] Next, the correction shown in (A) above is performed. Specifically, similar to the correction shown in the first embodiment, if the tool 3 approaches or cuts into the third processing surface M3, a correction value is calculated to move the tool 3 toward the normal direction of the third processing surface M3. This vector is set to VcA3. For example, Figure 26 As shown in (a), when the tool 3 cuts into the third processing surface M3, if Figure 26 By moving the tool 3 along the vector VcA3 as shown in (b), cutting can be avoided.

[0177] Then, the vector Vc3 obtained by synthesizing the aforementioned vector VcB3 and the vector VcA3 is calculated. That is, (vector Vc3) = (vector VcA3) + (vector VcB3). The synthesized vector Vc3 is the correction vector required for machining the third machined surface M3.

[0178] Here, since the correction due to the contour error of the tool 3 is completed between the first processing surface M1 and the second processing surface M2, if a new correction is added to the processing position of the tool 3, the above correction may be invalidated. However, as mentioned above, the final movement vector between the first processing surface M1 and the second processing surface M2, i.e. Figure 23 The movement vector Vc12 shown in (b) is a vector on the plane S. Therefore, if the movement is in a direction perpendicular to the plane S (the normal direction of the plane S), the movement vector Vc12 is not affected. Therefore, it does not affect the correction between the first machined surface M1 and the second machined surface M2.

[0179] Therefore, if Figure 27 (a) Figure 27 As shown in (b) of FIG. 3 , it is sufficient to transform the vector Vc3 (the resultant vector of VcB3 and VcA3) into a vector in the normal direction of the plane S. This vector in the normal direction is referred to as "VcS3".

[0180] Here, the directions of vectors Vc3 and VcS3 can be obtained from CAD data and calculated in advance. Therefore, the magnitude of vector VcS3 can be calculated based on the magnitude of vector Vc3 (including the positive and negative signs).

[0181] like Figure 28 (a)~ Figure 28 As shown in (c), if the angle between vector Vc3 and vector VcS3 is θ2, the following formula (5) can be obtained.

[0182] |VcS3|×cosθ2=|Vc3|

[0183] That is, |VcS3|=|Vc3| / cosθ2 …(5)

[0184] At this point, the magnitude (including the sign) of vector VcS3 has been determined, and the direction of vector VcS3 can be obtained from the CAD data. Therefore, vector VcS3 is determined.

[0185] Therefore, a correction vector, namely, “vector Vc12 + vector VcS3 ”, which takes corrections on all the processed surfaces, namely the first processed surface M1 , the second processed surface M2 , and the third processed surface M3 , can be obtained.

[0186] Since the vector Vc12 is obtained by the first embodiment described above, the procedure for calculating the "vector VcS3" will be described in detail below.

[0187] When the tool 3 processes the workpiece 5 by two-point contact between the first processing surface M1 and the second processing surface M2, according to the aforementioned Figure 18The coordinates of X, Y, and Z are corrected by using the equation (3) shown in the figure. Furthermore, if the X-axis component of the vector Vc12 is set to Vc12x, the Y-axis component is set to Vc12y, and the Z-axis component is set to Vc12z, then Figure 18 The formula (3) shown becomes the following formula (6).

[0188] X[Px+Vc12x]

[0189] Y[Py+Vc12y]

[0190] Z[Pz+Vc12z] …(6)

[0191] When machining the workpiece 5 through three-point contact between the three machining surfaces M1, M2, and M3, the aforementioned vector VcS3 is added. If the X-axis component of vector VcS3 is VcS3x, the Y-axis component is VcS3y, and the Z-axis component is VcS3z, then the X, Y, and Z coordinates are expressed as Equation (7) below.

[0192] X[Px+Vc12x+VcS3x]

[0193] Y[Py+Vc12y+VcS3y]

[0194] Z[Pz+Vc12z+VcS3z] …(7)

[0195] Therefore, if the formula (7) can be made into a specific NC program, machining relying on the three-point contact of the tool 3 can be implemented.

[0196] First, the second distance effect coefficient Ed3, which varies depending on the distance between the tool 3 and the third machined surface M3, is calculated. The calculation method for the second distance effect coefficient Ed3 is the same as that for the first distance effect coefficient Ed described above. The second distance effect coefficient Ed3 is a variable that varies within the range of "0-1." When the tool 3 is in contact with the third machined surface M3, Ed3 = 1.

[0197] After calculating the second distance effect coefficient Ed3, the normal direction shown in (A) above is corrected. Specifically, the correction vector of the tool 3 relative to the third processing surface M3 is calculated. The X, Y, and Z components of this correction vector are set to VcAx, VcAy, and VcAz, respectively. In addition, if the X, Y, and Z components of the unit normal vector at the processing point of the third processing surface M3 are set to i3, j3, and k3, respectively, and the reference symbol corresponding to the angle of contact between the tool 3 and the third processing surface M3 is set to #50D, the above-mentioned correction vector can be calculated using the following formula (8).

[0198] VcA3x=i3×#50D×Ed3

[0199] VcA3y=j3×#50D×Ed3

[0200] VcA3z=k3×#50D×Ed3 …(8)

[0201] Next, a process is performed to correct insufficient cutting depth or insufficient cutting depth with respect to the third machined surface M3 caused by the correction operation of the first machined surface M1 and the second machined surface M2 as shown in (B) above.

[0202] like Figure 23 As shown in FIG, the vector obtained by setting the inner product of the final movement vector Vc12 of the first processing surface M1 and the second processing surface M2 and the unit normal vector of the third processing surface M3 (denoted as "IPS3c12") in the opposite direction becomes the correction vector for eliminating insufficient cutting or cutting depth. If this vector is denoted as "VcB3", the X, Y, and Z components VcB3x, VcB3y, and VcB3z of the vector VcB3 can be obtained by Figure 29 The calculation is performed using the formula (9) shown in FIG. In the formula (9), “IPS3c12=i3×Vc12x+j3×Vc12y+k3×Vc12z” is used.

[0203] The correction vector Vc3 (Vc3x, Vc3y, Vc3z) of the tool 3 with respect to the third machined surface M3 is calculated by synthesizing the above-mentioned equations (8) and (9). That is, the correction vector Vc3 is calculated using the following equation (10).

[0204] Vc3x=VcA3x+VcB3x

[0205] Vc3y=VcA3y+VcB3y

[0206] Vc3z=VcA3z+VcB3z …(10)

[0207] Next, the correction vector Vc3 is converted into a vector in the normal direction of the plane S, and this vector is set as vector VcS3.

[0208] In this case, the unit normal vector of plane S (i.e., the orientation of vector VcS3) can be obtained in advance. However, the magnitude of vector VcS3, |VcS3|, must be calculated as "|Vc3| / cosθ2" in an NC program. Specifically, the magnitude (scalar) of a vector can be calculated by taking the square root of the sum of the squares of its X, Y, and Z components. However, this calculation is too long to fit into a single line of an NC program.

[0209] Therefore, if the inner product of vector VcS3 and its own unit vector (i3, j3, k3) is calculated, "cos(0°) = 1," so a scalar can be calculated. Furthermore, the sign of vector VcS3 (Sign(VcS3)) is not lost. That is, the following equation (11) is obtained.

[0210] |Vc3|×Sign(VcS3)=Vc3x×i3+Vc3y×j3+Vc3z×k3…(11)

[0211] If the unit normal vector of the plane S is set to i4, j4, k4, and the angle between the third processed surface M3 and the plane S is set to θ2, the final correction vector Vc3 of the third processed surface M3 is expanded, and it becomes Figure 30 However, the directions of i4, j4, and k4 are close to the normal line of the third processed surface M3, that is, the directions in which the inner product with the normal line of the third processed surface M3 is positive.

[0212] As according to Figure 30 As can be understood from the equation (12) shown, the term "Vc3x×i3+Vc3y×j3+Vc3z×k3" is universal regardless of the X, Y, and Z axes. If this term is expanded, it becomes Figure 31 Equation (13) shown.

[0213] Furthermore, if "IPS3c12" shown in formula (13) is expanded, it becomes Figure 32 Equation (14) shown.

[0214] Therefore, according to Figures 30-32 Equations (12) to (14) are shown, and the vector VcS3 is expanded. The terms contained in these equations are the unit normal vector of the machining point on each surface, the avoidance vector, the first distance effect coefficient, the second distance effect coefficient, trigonometric functions, and the reference symbols #50A, #50C, and #50D determined during machining. These are known numerical values. Therefore, the final "movement vector VcS3" of tool 3 can be calculated.

[0215] Specifically, based on the above equations (3) and (12), we can expand equation (7) to obtain Figure 33 Equations (15) to (18) are shown.

[0216] Furthermore, referring to equations (15) and (18), we can summarize Figure 34 In formula (19), Px, α, β, and γ are all real values. Therefore, the calculation load of the NC program during actual machining does not increase.

[0217] By correcting the machining position of the tool 3 using the movement vector VcS3 in this manner, when the tool 3 contacts three surfaces of the workpiece 5 for machining, stable machining can be performed taking into account the contour error of the tool 3 .

[0218] [Description of Effects of the Second Embodiment]

[0219] Thus, in the processing device involved in the second embodiment, when the tool 3 changes from two-point processing of the first processing surface M1 and the second processing surface M2 of the workpiece 5 to three-point processing of the third processing surface M3, the vector that becomes the normal direction relative to the plane S is calculated, and by correcting the vector, interference between the tool 3 and the third processing surface M3 is avoided.

[0220] Furthermore, when transitioning from two-point machining to three-point machining, when the distance between tool 3 (end mill) and the third machining point is close to the specified distance, the position offset is corrected based on the correction value at the first machining point, the correction value at the second machining point, the correction value at the third machining point, the first distance effect coefficient and the second distance effect coefficient.

[0221] Therefore, when the tool 3 switches from two-point machining, which relies on the first and second machining surfaces M1, M2, to three-point machining, which includes the third machining surface M3, the tool 3 can eliminate the problem of cutting into the third machining surface M3 or insufficient cutting depth. As a result, the workpiece 5 can be machined with high precision even in three-point machining.

[0222] Although the embodiments have been described above, it should not be understood that the description and drawings constituting part of this disclosure limit the invention. Various alternative embodiments, examples, and operational techniques will become apparent to those skilled in the art from this disclosure.

Claims

1. A processing method for processing a workpiece into a desired shape, wherein: The above processing method has the following steps: detecting a positional deviation between an actual contour line of the end mill when the end mill is held in a tool holding portion and an ideal contour line of the end mill having an ideal shape, namely, an ideal contour line; wherein the end mill has a hemispherical lower end and the end mill rotates about a rotation axis to perform cutting processing on the workpiece; calculating correction values ​​for correcting the positional deviation between the ideal contour line and the actual contour line in a plurality of angular directions with the center of the hemispherical shape as a reference; When the machining point to be machined by the end mill changes from one-point machining of a first machining point on the first machining surface of the workpiece to two-point machining of the first machining point and a second machining point on a second machining surface different from the first machining surface, calculating a first distance effect coefficient indicating the magnitude of the influence of the positional deviation when machining the second machining point based on the distance between the end mill and the second machining point; and When the one-point machining is performed by the end mill, the positional offset of the first machining point is corrected based on the correction value. When the one-point machining is switched to the two-point machining, when the distance between the end mill and the second machining point is within a prescribed distance, the positional offset is corrected based on the correction value at the first machining point and the first distance effect coefficient. The above-mentioned first distance effect coefficient is a coefficient that changes in the range of 0 to 1 corresponding to the distance between the above-mentioned end mill and the above-mentioned second processing point. The shorter the distance between the above-mentioned end mill and the above-mentioned second processing point, the greater the rate of change. The above-mentioned first distance effect coefficient is set to 1 when the distance between the above-mentioned end mill and the above-mentioned second processing point is 0.

2. The processing method according to claim 1, wherein: The first distance effect coefficient is set so as to increase as the end mill approaches the second processing point.

3. The processing method according to claim 2, wherein: The first distance effect coefficient changes so that an increase rate gradually increases as the distance from the predetermined distance approaches the second processing point.

4. The processing method according to claim 1, wherein: The above processing method also has the following steps: When the positional deviation of the first processing point is corrected, when the end mill comes into contact with the second processing surface, the amount of cutting into the second processing surface is calculated as the first avoidance amount. When the positional deviation of the second processing point is corrected, when the end mill comes into contact with the first processing surface, the amount of cutting into the first processing surface is calculated as the second avoidance amount. When the end mill processes the first and second processed surfaces, positional deviations of the end mill when processing the first and second processed surfaces are corrected based on the first and second avoidance amounts.

5. The processing method according to claim 1, wherein: When the processing points processed by the end mill are changed from two-point processing of the first processing point on the first processing surface and the second processing point on the second processing surface to three-point processing including the first processing point, the second processing point and the third processing point on the third processing surface different from the first processing surface and the second processing surface, A plane including a correction vector for correcting the first processing point and a correction vector for correcting the second processing point, i.e., a prescribed plane, is defined; a correction value at the third processing point is calculated in a direction orthogonal to the prescribed plane; and the position offset is corrected based on the correction value at the third processing point.

6. The processing method according to claim 1, wherein: The above processing method also has the following steps: When the processing points processed by the end mill are changed from two-point processing of the first processing point on the first processing surface and the second processing point on the second processing surface to three-point processing including the first processing point, the second processing point and the third processing point on the third processing surface different from the first processing surface and the second processing surface, calculating a second distance effect coefficient indicating the magnitude of the influence of the positional offset when performing the two-point machining based on the distance between the end mill and the third machining point; and When the two-point machining is switched to the three-point machining, when the distance between the end mill and the third machining point is within a predetermined distance, the positional offset is corrected based on the correction value at the first machining point, the correction value at the second machining point, the correction value at the third machining point, and the second distance effect coefficient. The above-mentioned second distance effect coefficient is a coefficient that changes in the range of 0~1 corresponding to the distance between the above-mentioned end mill and the above-mentioned third processing point. The shorter the distance between the above-mentioned end mill and the above-mentioned third processing point, the greater the rate of change. The above-mentioned second distance effect coefficient is set to 1 when the distance between the above-mentioned end mill and the above-mentioned third processing point is 0.

7. A processing device for processing a workpiece into a desired shape, wherein: The above-mentioned processing device has: an end mill, the lower end of which is hemispherical and which rotates about a rotation axis to perform cutting processing on the workpiece; a tool holding portion, the tool holding portion being used to hold the end mill; a positional deviation detecting unit configured to detect a positional deviation between an actual contour line of the end mill when the end mill is held in the tool holding unit and an ideal contour line of the end mill in an ideal shape; a positional deviation correcting unit that calculates correction values ​​for correcting positional deviations between the ideal contour line and the actual contour line in a plurality of angular directions with respect to the center of the hemispherical shape, and corrects the positional deviation of the end mill based on the calculated correction values; and a distance effect coefficient calculation unit for calculating, when the machining point to be machined by the end mill is shifted from one-point machining of a first machining point on a first machining surface of the workpiece to two-point machining of the first machining point and a second machining point on a second machining surface different from the first machining surface, a first distance effect coefficient indicating the magnitude of the influence of the positional offset when machining the second machining point based on the distance between the end mill and the second machining point; The position offset correction unit corrects the position offset of the first processing point based on the correction value when the one-point processing is performed by the end mill. When the one-point processing is switched to the two-point processing, when the distance between the end mill and the second processing point is within a prescribed distance, the position offset is corrected based on the correction value at the first processing point and the first distance effect coefficient. The above-mentioned first distance effect coefficient is a coefficient that changes in the range of 0 to 1 corresponding to the distance between the above-mentioned end mill and the above-mentioned second processing point. The shorter the distance between the above-mentioned end mill and the above-mentioned second processing point, the greater the rate of change. The above-mentioned first distance effect coefficient is set to 1 when the distance between the above-mentioned end mill and the above-mentioned second processing point is 0.

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