Machine tool, machining path generation method, and computer program

Abstract

The present application provides a kind of machine tool, machining path generation method and computer program capable of high precision and short time generation processing path.The machine tool (1) has: spindle (30), its front end part installs tool;Moving part (6), it makes the spindle (30) installed with tool (30a) along the reference path of the outer periphery side or inner periphery side of main workpiece (9) to the peripheral edge of main workpiece (9) or the way of moving away from the peripheral edge;First detection part (CPU 41), it detects the contact of tool (30a) and peripheral edge;Acquisition part (CPU 41), whenever the first detection part detects the contact, acquisition part (CPU 41) obtains the coordinate of spindle (30);And first generation part (CPU 41), it generates first machining path based on the multiple coordinates detected by acquisition part.

Description

TECHNICAL FIELD

[0001] The present technology relates to a machine tool that performs deburring, grinding, or the like, a machining path generation method, and a computer program. BACKGROUND

[0002] When removing burrs generated on the surface of a workpiece or when grinding the workpiece, an operator installs a tool on a spindle of a machine tool and moves the spindle on the outer periphery side of the workpiece to perform machining. There is a machine tool having a parallel link mechanism in the machine tool. The parallel link mechanism has a plate that is triangular in plan view, two arms (links) that are parallel and whose one end portions are joined to each edge portion of the plate in a manner that the two arms can rotate, and a moving portion that is joined to the other end portion of each arm in a manner that can rotate. The plate is used to hold the spindle. The moving portion is moved in a direction that intersects the plate, and the plate and the spindle are moved in a desired direction.

[0003] The machining path of the spindle is generated by programming based on design drawing information of the workpiece (for example, Patent Literature 1) or is generated using a CAM device.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Publication No. 2019-150864 SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] When the workpiece is a die cast or a casting, the shape error with respect to the design drawing is large. Therefore, the machine tool sometimes fails to perform machining because the tool does not contact the workpiece or excessively contacts the workpiece to cause excessive machining when performing machining. The off-line teaching of Patent Literature 1 and the like that generates a path in a manner that the tool does not directly contact the main workpiece is one of the machining methods. Even if the accuracy of the shape of the workpiece is high, the off-line teaching is difficult to generate a machining path that well imitates the surface of the workpiece due to various reasons such as movement error of the spindle, difference in tool length, difference in tool shape, deviation of the machining origin, and the like. The on-line teaching that teaches a path in a manner that the tool directly contacts the main workpiece requires a large amount of time to create a machining path that imitates the surface of the workpiece that has been deformed and can cause deviation of the machining path depending on the operator. In addition, when the batch of the workpiece is different, when the shape of the workpiece or the burr changes due to maintenance of the casting mold, the machining path is corrected every time, which is very troublesome.

[0009] An object of the present application is to provide a machine tool, a machining path generation method, and a computer program that can generate a machining path with high accuracy and in a short time.

[0010] Solution for solving the problem

[0011] The machine tool of the present application is provided with: a spindle to which a tool is attached at a front end portion thereof; a movement control section that moves the spindle along a reference path on the outer periphery side or the inner periphery side of a main workpiece after machining in a desired accuracy, in a manner to approach or to move away from the peripheral edge portion of the main workpiece; a first detection section that detects a case where the tool contacts the peripheral edge portion; an acquisition section that acquires coordinates of the spindle each time the first detection section detects the contact; and a first generation section that generates a first machining path based on a plurality of coordinates acquired by the acquisition section. The reference path is a path that is not along a rough machining path of the main workpiece. Specifically, it is a path of a machining program used in mass production machining. As described above, in a case where the main workpiece has a hole portion or the like on the inner periphery side thereof, the reference path is also set on the inner periphery side of the main workpiece.

[0012] According to the above-described structure, the machine tool moves the spindle along the reference path to approach or to move away from the peripheral edge portion of the main workpiece, acquires the coordinates of the spindle when the contact of the tool with the peripheral edge portion is detected, and is able to generate the machining path in high accuracy and in a short time based on the coordinates. Therefore, when machining is performed based on the generated machining path, the machining accuracy of the machine tool is good.

[0013] In addition, when the shape of the workpiece is changed due to a difference in the shape, a shape correction, a change in the molding conditions, a difference in the lot, or the like, or when the mounting position is deviated or changed to a tool with a slightly different shape due to a change in the arrangement of the jig, the machine tool produces the main workpiece each time. Since the machine tool generates a machining path that imitates the surface of the main workpiece, it is able to reduce the effort of adjusting the machining path each time at the time of mass production.

[0014] The movement control section of the machine tool of the present disclosure moves the spindle along the reference path in a sawtooth shape.

[0015] According to the above-described structure, the machine tool is able to detect the contact efficiently and well.

[0016] The movement control section of the machine tool moves the spindle to approach or to move away at points, i.e., approach-movement-away points, that are provided at a prescribed interval on the reference path.

[0017] According to the above-described structure, the machine tool is able to detect the contact efficiently and well.

[0018] The machine tool has a plurality of reference points on a reference path. When the first detection unit detects contact, the movement control unit moves the spindle away based on a third vector that is a sum of a first vector and a second vector, and moves the spindle closer based on a fourth vector, wherein the first vector is directed from the center of the spindle toward the shortest reference point in the travel direction of the spindle and has a predetermined first length, the second vector is orthogonal to the first vector and has a predetermined second length, and the fourth vector has an opposite direction to the second vector and has a third length that is longer than the second length.

[0019] According to the above structure, the machine tool can make the tool perpendicularly contact the peripheral portion of the main workpiece and can generate the machining path more favorably.

[0020] The first machining path of the machine tool includes a linear trajectory or a curved trajectory of a plurality of coordinates.

[0021] According to the above structure, the machine tool can generate the machining path favorably.

[0022] The spindle is rotated by driving of a spindle motor, and the machine tool has a second detection unit that detects a load applied to the spindle. The first detection unit detects contact based on a change in the load detected by the second detection unit.

[0023] According to the above structure, the machine tool can favorably detect contact.

[0024] The second detection unit of the machine tool detects a rotational speed, a torque, or a deviation amount of the spindle when the spindle motor is positively or negatively rotated at a low speed.

[0025] According to the above structure, the machine tool can favorably detect contact without damaging the workpiece.

[0026] The machine tool further has a fixing unit that fixes the spindle, and the second detection unit is a force sensor that is provided to the fixing unit and detects a force applied to the spindle.

[0027] According to the above structure, the machine tool can favorably and easily detect contact.

[0028] The movement control unit of the machine tool controls a movement shaft motor that drives a movement shaft. The machine tool further has a third detection unit that detects a load applied to the movement shaft. The first detection unit detects contact based on a change in the load detected by the third detection unit.

[0029] According to the above structure, the machine tool can favorably detect contact.

[0030] The machine tool further has a voltage application unit that applies a voltage to the spindle, and a current sensor that is connected to the voltage application unit. The first detection unit detects contact based on a current detected by the current sensor.

[0031] According to the above structure, when the tool contacts the main workpiece, current flows due to the voltage applied to the spindle by the voltage application section. The ammeter detects the flow of the current, and thus the machine tool can inexpensively detect the contact.

[0032] The movement control section of the machine tool moves the spindle along the first machining path generated by the first generation section so as to approach or move away from the peripheral portion of the main workpiece. The machine tool further includes a second generation section that generates a second machining path based on the plurality of coordinates detected by the acquisition section, a calculation section that calculates a matching rate of the first machining path and the second machining path, and a storage section that stores the first machining path when the matching rate calculated by the calculation section is equal to or less than a predetermined value.

[0033] According to the above structure, the machine tool can generate the machining path with higher accuracy.

[0034] The machining path generation method includes the steps of holding the main workpiece on a holding table of a machine tool, installing a tool on a front end of a spindle, moving the spindle along a reference path on an outer circumferential side or an inner circumferential side of the main workpiece so as to approach or move away from a peripheral portion of the main workpiece, detecting contact of the tool with the peripheral portion, acquiring coordinates of the spindle each time the contact is detected, and generating a machining path based on the plurality of acquired coordinates.

[0035] According to the above structure, the machine tool can generate the machining path with high accuracy and in a short time, and the machining accuracy is good.

[0036] The computer program causes a computer to execute the following processing: moving a spindle of a machine tool on which a tool is installed along a reference path on an outer circumferential side or an inner circumferential side of a main workpiece so as to approach or move away from a peripheral portion of the main workpiece, detecting whether the tool contacts the peripheral portion, acquiring coordinates of the spindle when it is determined that the tool contacts the peripheral portion, and generating a machining path based on the plurality of acquired coordinates.

[0037] According to the above structure, the computer program can generate the machining path with high accuracy and in a short time, and the machining accuracy is good.

[0038] Effects of the Invention

[0039] The machine tool of the present disclosure can move the spindle along the reference path so as to approach or move away from the peripheral portion of the main workpiece, acquire the coordinates of the spindle when the contact of the tool with the peripheral portion is detected, and generate the machining path based on the coordinates with high accuracy and in a short time. Thus, the machining accuracy is improved. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 is a schematic perspective view of a machine tool.

[0041] Figure 2 is a block diagram showing the structure of the machine tool.

[0042] Figure 3 is an explanatory diagram illustrating generation of a reference path.

[0043] Figure 4 is an explanatory diagram illustrating generation of a machining path.

[0044] Figure 5 is an explanatory diagram illustrating machining based on the machining path.

[0045] Figure 6 is a flowchart showing steps of machining path generation processing by the CPU.

[0046] Figure 7 is an explanatory diagram showing an example of a display screen of the display section.

[0047] Figure 8 is an explanatory diagram illustrating exploration method No. 1.

[0048] Figure 9 is an explanatory diagram illustrating generation of a machining path.

[0049] Figure 10 is an explanatory diagram when a smoothing function is used.

[0050] Figure 11 is an explanatory diagram showing a first example of a contact detection method.

[0051] Figure 12 is an explanatory diagram showing a second example of a contact detection method.

[0052] Figure 13A is a side view showing a third example of a contact detection method.

[0053] Figure 13B is a front view showing a third example of a contact detection method.

[0054] Figure 14 is an explanatory diagram showing a fourth example of a contact detection method.

[0055] Figure 15 is an explanatory diagram illustrating exploration method No. 2.

[0056] Figure 16 is an explanatory diagram illustrating exploration method No. 3.

[0057] Figure 17 is Figure 16 a partial enlarged view. DETAILED DESCRIPTION

[0058] Hereinafter, based on the drawings showing the machine tool 1 of the present application, the explanation will be made. In the following explanation, the upper, lower, front, rear, left, and right shown in the drawings are used.

[0059] The machine tool 1 is provided with a base 2 that is rectangular in plan view. A plurality of reinforcing cylinders 2a are provided on the upper surface of the base 2. A holding table 3 is provided on the reinforcing cylinder 2a in the central portion of the base 2. The holding table 3 is cylindrical, and holds a workpiece.

[0060] Three columns 4 are provided around the holding table 3, and the three columns 4 extend upward from the reinforcing cylinder 2a. The three columns 4 are arranged at a phase interval of about 120 degrees in plan view. A rail 5 is provided on the side surface of each column 4 on the holding table 3 side, and extends in the up-and-down direction.

[0061] A moving portion 6 and a drive source are provided on the rail 5. The drive source is, for example, a ball screw 14 and a moving shaft motor 13 (refer to Figure 12 ). The ball screw 14 driven by the moving shaft motor 13 moves the moving portion 6 in the up-and-down direction along the rail 5. That is, the moving portion 6 is movable in a direction that intersects the first support plate 10 described later. A mounting portion for mounting the first link 11 and the second link 21 described later is provided on the side surface of the moving portion 6 on the holding table 3 side. The mounting portion is, for example, a hole or a protrusion.

[0062] The first support plate 10 is arranged on the upper side of the holding table 3. The first support plate 10 is triangular in plan view, and is substantially parallel to the upper surface of the holding table 3. Three edges of the first support plate 10 respectively oppose the three columns 4. That is, the three edges respectively correspond to the three moving portions 6. Each edge portion is connected to each moving portion 6 by two first links 11 that are parallel. The first link 11 is rod-shaped. One end of each of the two first links 11 is connected to both end portions of the edge portion via a rotatable joint 7. The other end of each of the two first links 11 is connected to the moving portion 6 via the rotatable joint 7. The joint 7 is, for example, a universal joint.

[0063] The first support plate 10 holds a main shaft 30 that protrudes upward and downward. The main shaft 30 holds a tool 30a at the end portion.

[0064] The second support plate 20 is arranged on the upper side (moving portion 6 side) of the first support plate 10, and a connecting cylinder 8 (connecting portion) that is axial in the up-and-down direction is provided between the first support plate 10 and the second support plate 20. The connecting cylinder 8 connects the first support plate 10 and the second support plate 20. The connecting cylinder 8 integrates the first support plate 10 and the second support plate 20.

[0065] The upper portion of the main shaft 30 penetrates the second support plate 20 from the inner side of the link cylinder 8. The second support plate 20 is triangular in plan view, and is substantially parallel to the first support plate 10. Three edges of the second support plate 20 respectively oppose the three columns 4. That is, the three edges respectively correspond to the three moving portions 6. Each edge portion is connected to each moving portion 6 by two second links 21 that are parallel. The second links 21 are rod-shaped. One end of each of the two second links 21 is connected to both end portions of the edge portion via a rotatable joint 7. The other end of each of the two second links 21 is connected to the moving portion 6 via a rotatable joint 7. The joint 7 is, for example, a universal joint.

[0066] The link cylinder 8 is hexagonal in plan view, and three of the six edge portions of the upper end portion of the link cylinder 8 that are circumferentially separated by one are connected to the three edge portions of the second support plate 20. Three of the six edge portions of the lower end portion of the link cylinder 8 that are circumferentially adjacent to each other are connected to the three edge portions of the first support plate 10.

[0067] When the three moving portions 6 are at the same height position, the main shaft 30 is located substantially directly above the center of the holding table 3.

[0068] When two of the moving portions 6 are at the same up-down position and the other moving portion 6 is moved to a position lower than the two moving portions 6, the main shaft 30 moves only in the horizontal direction toward the opposite side of the moving portion 6 that is moved downward.

[0069] When two of the moving portions 6 are at the same up-down position and the other moving portion 6 is moved to a position higher than the two moving portions 6, the main shaft 30 moves only in the horizontal direction toward the moving portion 6 that is moved upward. When the three moving portions 6 are moved by the same distance in the up-down direction, the main shaft 30 moves in the up-down direction. These movements are combined, whereby the machine tool 1 positions the main shaft 30 to a desired up-down front-rear left-right position. Thus, the main shaft 30 is connected to the ball screw 14 via the first support plate 10, the second support plate 20, the link cylinder 8, the first links 11, the second links 21, the joints 7, and the moving portions 6.

[0070] The main shaft 30 is provided with a main shaft motor 12 (refer to Figure 2 ). The main shaft 30 that is positioned to a desired position is rotated by the main shaft motor 12, and a tool 30a that is attached to the main shaft 30 processes a work that is held by the holding table 3.

[0071] As Figure 2The control device 40 includes a CPU 41, a storage section 42, a RAM 43, an input / output interface 44, an operation section 45, and a display section 46. The CPU 41 controls the operation of each section of the machine tool 1. The storage section 42, which can be rewritten, is an EPROM, an EEPROM, or the like. The storage section 42 stores a machining program DB 421 and a machining path generation program (hereinafter referred to as a program) 422. The machining program DB 421 stores a plurality of control programs (not shown) for controlling the machine tool 1 and machining programs for machining the workpiece 95 (refer to FIG. 1). The program 422 performs processing for generating a machining path. The program 422 is stored in a computer-readable recording medium 423 such as a CD-ROM, a DVD-ROM, or a USB memory, and is saved from the recording medium 423 to the storage section 42. The program 422 can be stored in the storage section 42 after being acquired from an external computer (not shown) connected to a communication network. Figure 5

[0072] Table 1 below is an example of a storage table of the machining program DB 421. The machining program DB 421 stores a No. column, a machining program column, and a machining path column. The No. column stores the serial number of the machining program. The machining program column stores the program of each machining. The machining path column initially stores a reference path L0 generated by an on-line teaching method or the like using CAM software or the like. The CPU 41 stores the machining path Ll in the machining path column when the machining path Ll is generated based on the program 422.

[0073] [Table 1]

[0074] Table 1

[0075]

[0076] When the operator operates the operation section 45, a signal is input from the operation section 45 to the input / output interface 44. The operation section 45 is a keyboard, a button, a touch panel, or the like. The input / output interface 44 outputs a signal to the display section 46. The display section 46 is a liquid crystal display panel or the like, and displays characters, graphics, symbols, or the like.

[0077] The control device 40 further includes a spindle control circuit 47 and a servo amplifier 48 corresponding to the spindle motor 12, and a moving shaft control circuit 49 and a servo amplifier 50 corresponding to the moving shaft motor 13. The spindle control circuit 47 outputs a command indicating a target value of the rotation direction, the rotational speed, or the like of the spindle motor 12 to the servo amplifier 48 based on an instruction from the CPU 41. The servo amplifier 48 supplies power to the spindle motor 12 based on the command. The encoder 18 detects the rotational position and the speed of the spindle motor 12, and sends a detection signal to the servo amplifier 48. The servo amplifier 48 compares the detection signal with the target value, and controls the power to be output. ​

[0078] The movement axis control circuit 49 outputs a command indicating a target value of the movement direction, speed, and the like of the three movement sections 6 to the servo amplifier 50 based on an instruction from the CPU 41. The servo amplifier 50 supplies electric power to the movement axis motor 13 based on the command. The encoder 19 detects the rotational position and speed of the movement axis motor 13 and sends a detection signal to the servo amplifier 50. The servo amplifier 50 compares the detection signal with the target value to control the electric power to be output. The CPU 41 corresponds to a movement control section.

[0079] In the machining path generation method, the deburred main workpiece 9 is held to the holding table 3 of the machine tool 1, and the tool 30a is mounted to the front end of the spindle 30. The main workpiece 9 has been deburred and thus has a desired machining accuracy. As Figure 3 , a reference path L0 is generated on the outer peripheral side of the main workpiece 9 by using an on-line teaching method of a CAM device or the like. The reference path L0 is a path based on a plurality of teaching points P a on the reference path L0. Figure 3 is a perspective view of the main workpiece 9. The spindle 30 moves along the reference path L0 in a manner to approach or move away from the peripheral edge portion of the main workpiece 9 based on the program 422.

[0080] The CPU 41 detects the contact of the tool 30a with the peripheral edge portion, and acquires the coordinates of the center P of the spindle 30 each time the contact is detected. As Figure 4 , the CPU 41 generates a machining path L1 based on the acquired coordinates of the plurality of centers P. In deburring machining of the burr workpiece 95, the workpiece 95 is held to the holding table 3. The spindle 30 on which the tool 30a is mounted is moved along the machining path L1 as Figure 5 , based on the corresponding machining program, to machine the workpiece 95.

[0081] Next, the machining path generation method will be described in detail.

[0082] The workpiece that has been deburred and is a good product is held as the main workpiece 9 to the holding table 3 by the operator. The operator mounts the tool 30a to be used to the spindle 30.

[0083] Figure 6 is a flowchart showing the steps of the machining path generation processing by the CPU 41. The CPU 41 acquires the reference path L0 (S1). The CPU 41 acquires the corresponding reference path L0 with reference to the machining program DB 421 after acquiring the serial number (No.) of the machining program based on the operation of the operator. Alternatively, the spindle 30 is moved to make the tool 30a touch the main workpiece 9, and the coordinates of a point indicating a corner of the main workpiece 9 and the coordinates of a point at which the posture of the tool 30a changes are acquired as the teaching points Pa , based on the teaching point P a to acquire the reference path L0.

[0084] The CPU 41 causes the display section 46 to display the reference path L0 and an input field (S2). The input field is used to input conditions such as the search method No., the search interval, and the search width. The search method is described later. Figure 7 is an example of a display screen of the display section 46. The CPU 41 displays the main workpiece, the teaching point P a , and the reference path L0 in a perspective view or a plan view on the right side of the display screen. The perspective view or the plan view can be switched by an operation of the worker. The CPU 41 displays the input field on the left side of the display screen. The worker confirms the reference path L0 displayed by the CPU 41 on the display section 46. When there is a portion of the reference path L0 that the worker wants to correct, the worker instructs the portion using the operation section 45. The worker inputs the search method No., the search interval, and the search width using the operation section 45. The search interval and the search width can also be shown as candidates to be selected by the worker. The CPU 41 acquires the search method No., the search interval, and the search width input by the worker to set the conditions for the search (S3). In the case of the second time and after, when the worker inputs the correction portion, the conditions for the search are set in such a manner that the search interval of the correction portion is reduced (S3).

[0085] The CPU 41 generates a search path T based on the reference path L0 and the search interval and the search width and the like in the set conditions (S4). The CPU 41 causes the spindle motor 12 to rotate at a low speed (forward rotation or reverse rotation) and moves the spindle 30 along the search path T using the moving axis motor 13 (S5). The low speed is suitably set to 100 rpm to 1000 rpm.

[0086] The CPU 41 determines whether the main workpiece 9 and the tool 30a are in contact (S6). The CPU 41 repeatedly performs the determination of S6 when it is determined that there is no contact (S6: "No"). The CPU 41 acquires the coordinates of the center P of the spindle 30 at the time point of contact when it is determined that there is contact (S6: "Yes") (S7). The CPU 41 generates a machining path L1 based on the coordinates of the plurality of centers P and stores the machining path L1 in the RAM 43 (S8).

[0087] The CPU 41 determines whether the generation of the machining path L1 is the first time (S9). When the determination is that it is the first time (S9: "Yes"), the CPU 41 sets the machining path L1 as the reference path L0 (S10), and returns the process to S2. The worker can input a small exploration interval in order to improve the accuracy, and the CPU 41 sets the input exploration interval in the setting of the second time condition (S3). The CPU 41 generates the exploration path T based on the new reference path L0, and repeats the processes of S4 to S8. In S8, the second machining path L1 is generated. The CPU 41 in S8 when the second machining path L1 is generated corresponds to the second generation section. When the determination in S9 is that it is not the first time (S9: "No"), the matching rate is calculated based on the first machining path L1 with respect to the second machining path L1 (S11). The matching rate can be represented by a ratio of the deviation area of the portion A enclosed by the first machining path L1 and the portion B enclosed by the second machining path L1 to the area of the portion A. The CPU 41 in S11 corresponds to the calculation section.

[0088] The CPU 41 determines whether the matching rate is below the threshold value (S12). The CPU 41 returns the process to S10 when the determination is that the matching rate is not below the threshold value (S12: "No"). The CPU 41 repeats the processes of S2 to S11 until the matching rate becomes below the threshold value. The CPU 41 stores the latest generated machining path L1 in the machining path column of the machining program of the corresponding No. of the machining program DB 421 and ends the process when the determination is that the matching rate is below the threshold value (S12: "Yes") (S13). The CPU 41 in S13 corresponds to the storage section.

[0089] As Figure 8 shown in FIG. 6, the reference path L0 is a path initially stored in the machining program DB 421. There are a plurality of teaching points P a on the reference path L0. The CPU 41 generates the exploration path T in which the spindle 30 moves in a zigzag manner based on the exploration interval and the exploration width set along the reference path L0. In Figure 8 , the broken line connecting the points P b is the exploration path T. The exploration width is the total width of the movement width in which the spindle 30 approaches the peripheral portion of the main workpiece 9 from the center of the reference path L0 and the movement width in which the spindle 30 moves away from the peripheral portion from the center, and is the swing width when the spindle 30 moves in a zigzag manner. The exploration interval is the distance in the advancing direction until the spindle 30 approaches the main workpiece 9 again after the closest approach to the main workpiece 9. The CPU 41 acquires the coordinates of the center P of the spindle 30 when the contact of the tool 30a with the main workpiece 9 is detected. The CPU 41 acquires the coordinates of the centers P1, P2,... P7,... of the spindle 30 every time the contact is detected.

[0090] As Figure 9 , the CPU 41 links the acquired centers P1, P2,... P7,... to generate a machining path L1. As for two centers P, it is not limited to the case of linking in a line segment shape, but can be linked in a circular arc shape or a curved line shape. As Figure 10 , the CPU 41 can correct using a smoothing function (a method of approximation by a smooth curve) so that the curve of the machining path L1 becomes smooth. The smooth curve is a spline curve, a Bezier curve, a NURBS curve, or the like.

[0091] Figure 11 is a diagram showing the machine tool 1 with a simplified model for explanation, and is different in shape from Figure 1 . The spindle 30 held by the linking cylinder 8 is disposed on the side surface of the main workpiece 9 at a prescribed position (a prescribed horizontal plane) on the outer periphery side of the main workpiece 9 in a state of having a prescribed angle with respect to the longitudinal direction of the column 4. The spindle 30 moves based on the above-described exploration path T at a low speed with forward rotation or reverse rotation. The CPU 41 detects the load of the spindle 30 corresponding to the signal output by the servo amplifier 48 based on the detection signal of the encoder 18. The CPU 41 detects the contact of the tool 30a with the main workpiece 9 based on the change in the detected load. Specifically, the CPU 41 detects the amount of change and the amount of deviation of the rotational speed and the torque of the spindle 30, and the like. Thus, the CPU 41 corresponds to a second detection section.

[0092] Figure 12 is a diagram showing the machine tool 1 with a simplified model for explanation, and is different in shape from Figure 1 . As described above, the moving shaft motor 13 drives the ball screw 14, and the moving section moves in the up-down direction along the rail. The CPU 41 detects the load of the ball screw 14 corresponding to the signal output by the servo amplifier 50 based on the detection signal of the encoder 19. The CPU 41 detects the contact of the tool 30a with the main workpiece 9 based on the change in the detected load. Specifically, the CPU 41 detects the amount of change and the amount of deviation of the rotational speed and the torque of the ball screw 14, and the like. Thus, the CPU 41 corresponds to a third detection section. The ball screw 14 corresponds to a moving shaft.

[0093] Figure 13A and Figure 13B is a diagram showing the machine tool 1 with a simplified model for explanation, and is different in shape from Figure 1 . The machine tool 1 is provided with a force sensor 15 between the linking cylinder 8 and the spindle 30. The force sensor 15 detects the load of the spindle 30, and the CPU 41 detects the contact of the tool 30a with the main workpiece 9 based on the change in the detected load. The force sensor 15 corresponds to a second detection section. The linking cylinder 8 corresponds to a fixed section.

[0094] AsFigure 14 A circuit is formed which connects the main shaft 30 on the positive side (+ side) of the battery 16 (voltage application section) and the main workpiece 9 on the negative side (- side) of the battery 16 (voltage application section) via the ammeter 17. The CPU 41 applies voltage to the main shaft 30, and current (power on) flows in the circuit when the tool 30a contacts the main workpiece 9. The ammeter 17 detects the power on. When the main workpiece 9 does not have conductivity, the surface of the main workpiece 9 is wetted with a conductive liquid to detect the power on.

[0095] The present embodiment enables the main shaft 30 to approach or move away from the peripheral portion of the main workpiece 9 along the reference path L0, and when contact of the tool 30a with the peripheral portion is detected, the coordinates of the center P of the main shaft 30 are acquired, and a machining path L1 is generated with high precision and in a short time based on the coordinates. The present embodiment generates the machining path L1 which imitates the surface of the main workpiece 9 each time the main workpiece 9 is produced. Therefore, even when the shape of the workpiece 95 changes due to differences in the outer shape, outer shape correction, differences in the lot, and the like, or when the mounting position deviates due to a change in the arrangement of the jig, the present embodiment does not need to correct the program to adjust the machining path at the time of mass production. The reference path L0 is not limited to the case where it is generated on the outer peripheral side of the main workpiece 9. It can also be generated on the inner peripheral side in the case where the main workpiece 9 has a hole portion or the like on the inner peripheral side. The CPU 41 at the time of execution S6 corresponds to the first detection section, the CPU 41 at the time of execution S7 corresponds to the acquisition section, and the CPU 41 at the time of execution S8 corresponds to the first generation section.

[0096] As for the second embodiment, it has the same structure as the first embodiment except that the exploration method is No. 2. Figure 15 The main shaft 30 is caused to move in accordance with the teaching points P0, P1, P2,... of the reference path L0 based on the set parameters (exploration interval, exploration width). That is, the main shaft 30 is caused to approach or move away in accordance with the points set at the exploration interval on the reference path L0, that is, the approach and away points. In the second embodiment, the exploration path T is generated in such a way that the main shaft 30 approaches or moves away from the peripheral portion of the main workpiece 9 in accordance with the approach and away points set at the exploration interval along the reference path L0.

[0097] • Between P1 and P2 (at the time of idle stroke)

[0098] (i) At the teaching point P1, the main shaft 30 is caused to approach half of the exploration width in the direction of (1) which is at right angles with respect to the vector from the teaching point P1 toward the teaching point P2.

[0099] (ii) When not in contact with the main workpiece 9, the main shaft 30 is caused to move away in the opposite direction, that is, in the direction of (2) by half of the exploration width.

[0100] (iii) After the movement, return to the teaching point P1, and move from the teaching point P1 in the direction of the teaching point P2 ((3) direction) by an amount corresponding to the exploration interval.

[0101] (iv) Perform the same movement as (i) to (iii). 1a

[0102] • P2 - P 2e between (contact during movement of (3))

[0103] (i) At the teaching point P2, after the movement in the direction of (1) and (2) above, return to the teaching point P2, and move from the teaching point P2 in the direction of the teaching point P3 ((3) direction) by an amount corresponding to the exploration interval. When contact is detected during the movement, store the coordinates of the center P 2a of the spindle 30.

[0104] (ii) At the center P 2a , approach the spindle 30 in the direction of (1).

[0105] When contact continues to be detected, move the spindle 30 away in the opposite direction of (2).

[0106] (iii) Move from the retreat point moved in the direction of (2) in the direction of the teaching point P3 ((3) direction) by an amount corresponding to the exploration interval. When contact is detected during the movement, store the coordinates of the center P 2b of the spindle 30.

[0107] (iv) Perform the same movement as above.

[0108] • P 2e - P 3c between (contact during movement of (1))

[0109] (i) When the distance from the center P 2e to the teaching point P3 is shorter than the exploration interval, approach the half of the exploration width in the direction of (1) with respect to the vector from the center P 2e to the teaching point P3. When in contact with the main workpiece 9, store the center P 2e at that time.

[0110] (ii) After the storage, return to the center P 2e , and move in the direction of the teaching point P3 ((3) direction) from the center P 2e to the teaching point P3 by an amount corresponding to the exploration interval.

[0111] (iii) Perform the same movement as above.

[0112] ​This implementation method can generate machining paths with high precision and in a short time, resulting in good machining accuracy.

[0113] Regarding the third embodiment, it has the same structure as the first embodiment, except that the exploration method is No. 3. For example... Figure 16 Initially, the same approach is performed as in the first embodiment. After the first contact is detected, relative to the center P of the main shaft 30 at this time... 1a The vector connecting the shortest teaching point P2 in the direction of travel of the main axis 30 performs approach and departure maneuvers based on the set exploration width (retreat amount, movement amount during measurement) and exploration interval. The exploration path is generated based on the vector, exploration width, and exploration interval after contact is detected.

[0114] like Figure 17 CPU 41 moves the principal axis 30 away from itself based on a third vector c, which is the sum of the first vector a and the second vector b, where the first vector a originates from the center P of the principal axis 30. 1a Oriented towards teaching point P2 and having a first length (exploration interval), the second vector b is orthogonal to the first vector a and has a second length (retreat amount). CPU41 makes the third vector c form an angle θ with the first vector a. a The third vector c is obtained in this way. Next, the CPU 41 uses the fourth vector d to bring the main axis 30 closer, where the fourth vector d has an orientation opposite to the second vector b and has a third length obtained by adding the measurement movement amount to the second length. Until contact with the main workpiece 9 is detected, the CPU 41 uses the endpoint P of the fourth vector d, which is inside the main workpiece 9. b To approach the target.

[0115] The center P of the main shaft 30 at the time of contact 1c When the distance between the teaching point P2 and the teaching point P2 is insufficient to cover the width of the exploration interval, CPU41 uses the distance from P2 as a reference point. 1c A third vector c, which is the sum of a first vector a with a first length and orthogonal to the first vector a and a second vector b with a second length, is used to move the principal axis 30 away from the next teaching point P3.

[0116] Explanation of reference numerals in the attached figures

[0117] 1: Machine tool; 3: Holding table; 4: Column; 6: Moving part; 10: First support plate; 11: First connecting rod; 12: Spindle motor; 13: Moving axis motor; 20: Second support plate; 21: Second connecting rod; 30: Spindle; 30a: Tool; 40: Control device; 41: CPU; 42: Storage unit; 421: Machining program DB; 422: Machining path generation program; 423: Recording medium.

Claims

1. A machine tool comprising: a spindle to which a tool is attached; a movement control section that moves the spindle along a reference path on an outer circumferential side or an inner circumferential side of a main workpiece after machining in a desired accuracy, to approach or move away from a peripheral edge portion of the main workpiece; a first detection section that detects a case where the tool contacts the peripheral edge portion; an acquisition section that acquires coordinates of the spindle each time the first detection section detects the contact; and a first generation section that generates a first machining path based on a plurality of coordinates acquired by the acquisition section, wherein the reference path has a plurality of reference points, wherein, when the first detection section detects the contact, the movement control section moves the spindle away based on a third vector that is a sum of a first vector and a second vector, and moves the spindle based on a fourth vector, wherein the first vector is from a center of the spindle toward a shortest reference point in a traveling direction of the spindle and has a predetermined first length, the second vector is orthogonal to the first vector and has a predetermined second length, and the fourth vector has an opposite direction to the second vector and has a third length that is longer than the second length.

2. The machine tool according to claim 1, wherein the movement control section moves the spindle along the reference path in a zigzag manner.

3. The machine tool according to claim 1, wherein the movement control section moves the spindle to approach or move away at approach- away points provided at regular intervals on the reference path.

4. The machine tool according to any one of claims 1 to 3, wherein the first machining path includes a linear-shaped track or a curved-shaped track of the plurality of coordinates.

5. The machine tool according to any one of claims 1 to 3, wherein the spindle is rotated by driving of a spindle motor, the machine tool further comprises a second detection section that detects a load applied to the spindle, and the first detection section detects the contact based on a change in the load detected by the second detection section.

6. The machine tool according to claim 5, wherein the second detection section detects a rotational speed, a torque, or a deviation amount of the spindle when the spindle motor is positively or negatively rotated at a low speed.

7. The machine tool according to claim 5, further comprising a fixing section that fixes the spindle, and the second detection section is a force sensor that is provided to the fixing section and detects a force applied to the spindle.

8. The machine tool according to any one of claims 1 to 3, wherein the movement control section controls a movement shaft motor that drives a movement shaft connected to the spindle, the machine tool further comprises a third detection section that detects a load applied to the movement shaft, and the first detection section detects the contact based on a change in the load detected by the third detection section. the machine tool further comprises: a voltage application section that applies a voltage to the spindle; and a current sensor that is connected to the voltage application section. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 9. The machine tool according to any one of claims 1 to 3, characterized in that ​ ​ ​ The first detection section detects the contact based on the current detected by the current sensor.

10. The machine tool according to any one of claims 1 to 3, characterized by the movement control section moves the spindle in a manner to approach or move away from the peripheral edge portion of the main workpiece along the first machining path generated by the first generation section, the machine tool further comprises: a second generation section that generates a second machining path based on the plurality of coordinates acquired by the acquisition section; a calculation section that calculates a matching rate of the first machining path and the second machining path; and a storage section that stores the first machining path when the matching rate calculated by the calculation section is below a predetermined value.

11. A machining path generation method comprising the steps of: holding a main workpiece machined at a desired accuracy on a holding table of a machine tool; mounting a tool on a front end of a spindle; moving the spindle in a manner to approach or move away from a peripheral edge portion of the main workpiece along a reference path on an outer circumferential side or an inner circumferential side of the main workpiece; detecting a case where the tool contacts the peripheral edge portion; acquiring coordinates of the spindle each time the contact is detected; and generating a machining path based on the plurality of acquired coordinates, wherein the reference path has a plurality of reference points, when the contact is detected, moving the spindle away based on a third vector that is a sum of a first vector and a second vector, and moving the spindle toward based on a fourth vector, wherein the first vector is from a center of the spindle toward a shortest reference point in a traveling direction of the spindle and has a predetermined first length, the second vector is orthogonal to the first vector and has a predetermined second length, and the fourth vector has an opposite direction to the second vector and has a third length longer than the second length.

12. A computer-readable recording medium recording a computer program that causes a computer to execute the processes of: moving a spindle of a machine tool on which a tool is mounted in a manner to approach or move away from a peripheral edge portion of a main workpiece machined at a desired accuracy along a reference path on an outer circumferential side or an inner circumferential side of the main workpiece; detecting whether the tool contacts the peripheral edge portion; and acquiring coordinates of the spindle when it is determined that the tool contacts the peripheral edge portion, and generating a machining path based on the plurality of acquired coordinates, wherein the reference path has a plurality of reference points, the computer program further causes the computer to execute the processes of: when it is determined that the tool contacts the peripheral edge portion, moving the spindle away based on a third vector that is a sum of a first vector and a second vector, and moving the spindle toward based on a fourth vector, wherein the first vector is from a center of the spindle toward a shortest reference point in a traveling direction of the spindle and has a predetermined first length, the second vector is orthogonal to the first vector and has a predetermined second length, and the fourth vector has an opposite direction to the second vector and has a third length longer than the second length. ​ ​ ​ 13. A computer program product comprising a computer program which, when executed by a processor, performs the machining path generation method according to claim 11.

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