Control device of a machine tool

Abstract

The present invention provides a control device and a control system for a machine tool. Processing data in polygon machining is stored in a processing data storage unit (17). A position detection unit (18) detects a cutting start position A and a cutting end position B of a workpiece based on changes in the processing data. The position detection unit (18) detects a machining surface from the cutting start position A and the cutting end position B.

Description

Technical Field

[0001] The present invention relates to a control device and a control system for a machine tool. Background Art

[0002] Polygon machining refers to a technique of machining a workpiece into a polygon (polygon) shape by rotating a tool and a workpiece at a certain ratio. In polygon machining, by changing the rotation ratio of the workpiece and the tool and the number of mounting pieces of the tool blade for polygon machining, the workpiece can be machined into a polygon such as a quadrilateral or a hexagon.

[0003] In polygon machining, after a polygon is formed on the workpiece surface, sometimes subsequent machining such as drilling is performed. At this time, it is necessary to determine the center of the workpiece machining surface and perform accurate positioning of the workpiece and the tool.

[0004] In order to determine the machining surface after polygon machining, the position of the tool axis (tip position) is acquired in advance before polygon machining. In the case where the tip position is not known, processing operations such as aligning the tip position with the center of the machining surface of the workpiece are required before the start of polygon machining.

[0005] As a method of adjusting the position of a polygon angle, Japanese Patent Laid-Open No. 4-164557 discloses: "When machining a polygon shape of a workpiece, the position deviation obtained by dividing the command speeds of two main shafts by their respective position loop gains is offset from the machining start position of the workpiece and the tool position, and then the two main shafts are driven. After the two main shafts reach the command speeds, machining is started to machine from the set position of the workpiece, so that an angle of a polygon shape is generated at the set position on the circumferential surface of the workpiece."

[0006] However, this technique adjusts the position of the angle of the polygon formed by polygon machining and does not support the positioning of the tool and the workpiece in subsequent machining after polygon machining. Summary of the Invention

[0007] In the field of machine tools, a technique for detecting the position of a machining surface formed on a workpiece by polygon machining is desired.

[0008] A control device according to one aspect of the present disclosure controls a machine tool having a first axis for rotating a tool and a second axis for rotating a workpiece, and rotates the first axis and the second axis to machine the workpiece into a polygon. The control device includes: a machining data acquisition unit that acquires machining data that changes as the workpiece is machined; and a position detection unit that detects the angle of the second axis after machining at which the position of the workpiece machining surface is based on the change in the machining data.

[0009] A control system according to one aspect of the present disclosure controls a machine tool having a first axis for rotating a tool and a second axis for rotating a workpiece, and rotates the first axis and the second axis to machine the workpiece into a polygon. The control system includes: a machining data acquisition unit that acquires machining data that changes as the workpiece is machined; and a position detection unit that detects the angle of the second axis after machining of the position of the machined surface of the workpiece based on the change in the machining data. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a hardware configuration diagram of the numerical control device in the present embodiment.

[0011] Figure 2 is a block diagram of the numerical control device in the present embodiment.

[0012] Figure 3 is a chart showing an example of the change in load torque.

[0013] Figure 4 is a block diagram of the value control device in the present embodiment.

[0014] Figure 5 is a diagram showing the detection method of the machining surface center detection unit.

[0015] Figure 6 is a block diagram of the numerical control device in the present embodiment.

[0016] Figure 7 is a diagram showing the inspection method of the machining surface center detection unit.

[0017] Figure 8 is a block diagram of the numerical control device in the present embodiment.

[0018] Figure 9 is a diagram showing the change in the machining surface cutting and load torque for multiple times.

[0019] Figure 10 is a diagram showing an example of a program using variables.

[0020] Figure 11 is a block diagram of the numerical control device in the present embodiment.

[0021] Figure 12 is a diagram showing the axis conversion process.

[0022] Figure 13 is a block diagram of the numerical control device in the present embodiment.

[0023] Figure 14 is a diagram showing the prevention process of error detection.

[0024] Figure 15It is a flowchart showing the operation of the numerical control device.

[0025] Figure 16 It is a diagram showing the processing of the representative value calculation unit.

[0026] Figure 17 It is a program example of this embodiment. Detailed implementation mode

[0027] Hereinafter, an embodiment in which the control device of the present disclosure is installed in the numerical control device 100 is shown.

[0028] Figure 1 It is a hardware structure diagram of the numerical control device 100 of one embodiment.

[0029] The CPU 111 included in the numerical control device 100 of this embodiment is a processor that integrally controls the numerical control device 100. The CPU 111 reads out the system program stored in the ROM 112 via the bus 120 and controls the overall numerical control device 100 according to the system program. Temporary calculation data, display data, and various data input by the operator via an input unit (not shown) are temporarily stored in the RAM 113.

[0030] The non-volatile memory 114 is composed of, for example, a memory supported by a battery (not shown), an SSD (Solid State Drive), etc. The non-volatile memory 114 maintains the storage state even when the power supply of the numerical control device 100 is turned off. Programs read in from the external device 72 via the interface 115, programs input via the input unit 30, and various data (for example, set parameters obtained from the machine tool, etc.) obtained from each part of the numerical control device 100 or the machine tool are stored in the non-volatile memory 114. The programs or various data stored in the non-volatile memory 114 can also be loaded into the RAM 113 during execution / use. In addition, various system programs such as a known analysis program are pre-written in the ROM 112.

[0031] The interface 115 is an interface for connecting the numerical controller 100 and an external device 72 such as an adapter. Programs and various parameters are read in from the external device 72 side. In addition, programs and various parameters edited in the numerical control device 100 can be stored in an external storage unit via the external device 72. The PMC (Programmable Machine Controller) 116 controls the input / output of signals between devices such as machine tools, robots, and sensors installed on the machine tool or robot via the I / O unit 117 through a sequence program built in the numerical control device 100.

[0032] The display unit 70 outputs and displays various data read into the memory, data obtained as a result of executing a program, etc. via the interface 118. In addition, the input unit 30 composed of an MDI, an operation panel, a touch panel, etc. transmits commands and data based on the operator's operation to the CPU 111 via the interface 119.

[0033] The axis control circuit 130 for controlling each axis of the machine tool receives the axis movement instruction from the CPU 111 and outputs the axis instruction to the servo amplifier 140. The servo amplifier 140 receives the instruction and drives the servo motor 150 for moving the axis of the machine tool. The servo motor 150 of the axis has a built-in position / speed detector, and feeds back the position / speed feedback signal from the position / speed detector to the axis control circuit 130 to perform position / speed feedback control. Figure 1 In the hardware structure diagram of FIG. 1 , the axis control circuit 130, the servo amplifier 140, and the servo motor 150 are each shown as one, but in fact, the number of axes of the machine tool to be controlled is the same as that of the axes of the machine tool to be controlled. Figure 2 ) in which the control device of the present embodiment represents a tool axis driven by a servo motor.

[0034] The spindle control circuit 160 receives a spindle rotation command for the machine tool spindle and outputs a spindle speed signal to the spindle amplifier 161. The spindle amplifier 161 receives the spindle speed signal, rotates the spindle motor 162 of the spindle at the commanded speed, and drives the workpiece axis. A position encoder 163 is coupled to the spindle motor 162, and the position encoder 163 outputs a feedback pulse in synchronization with the spindle rotation, and the feedback pulse is read by the CPU 111.

[0035] Figure 2FIG. 0 is a block diagram showing a main part of a numerical control device 100 according to an embodiment of the present disclosure. The numerical control device 100 includes: a program 11 that describes a coordinate system of a machine tool, machining instructions, end instructions, etc.; a program analysis unit 12 that analyzes the program 11 and generates a movement instruction for an interpolation unit 13 and an axis rotation instruction for a spindle control unit 14; an interpolation unit 13 that generates interpolation data for an instruction path of a tool by interpolation calculation based on the movement instruction from the program analysis unit 12 and outputs the interpolation data to a servo control unit 15; a spindle control unit 14 that rotates a workpiece based on the axis rotation instruction from the program analysis unit 12; a servo control unit 15 that rotates the tool based on the interpolation data; a machining data acquisition unit 16 that acquires machining data in polygon machining; a machining data storage unit 17 that stores the machining data acquired by the machining data acquisition unit 16; and a position detection unit 18 that detects the position of a machined surface of the workpiece based on the machining data stored in the machining data storage unit 17. In addition, the structure of the present embodiment may be such that the tool axis is driven by a servo motor 150 and the workpiece axis is driven by a spindle motor 161, but it may also be that both axes are driven by a servo motor.

[0036] The machining data acquisition unit 16 acquires machining data in polygon machining. The machining data includes load torque, machining sound, vibration, heat, etc. For example, when the tool contacts the workpiece, phenomena such as an increase in load torque, generation of a specific sound, vibration of the tool or workpiece, and heat generation at the contact part occur. The machining data acquisition unit 16 acquires the machining data that changes in such polygon machining.

[0037] The machining data acquisition unit 16 also acquires the positions (angles) of the rotation axis (first axis) of the tool and the rotation axis (second axis) of the workpiece. The machining data acquisition unit 16 acquires the position information of the rotation axis of the workpiece from a position encoder 163 and the position information of the rotation axis of the tool from the servo control unit 15. The machining data storage unit 17 stores the machining data acquired by the machining data acquisition unit 16 in polygon machining in association with the position information of the tool axis and the workpiece axis.

[0038] Refer to Figure 3 , the change of machining data in polygon machining will be described. In the following description, the load torque, which is one of the machining data, is taken as an example, but other machining data may also be used.

[0039] In polygon machining, the tool and the workpiece rotate simultaneously. At this time, the tool does not always contact the workpiece for cutting, but there are cases where the tool and the workpiece are not in contact (referred to as the non-cutting state). In the non-cutting state, the tool idles, so the load torque shifts at a low value. When the tool starts cutting the workpiece, that is, when the tool contacts the workpiece, the load torque increases (the rise of the load torque). And during the period when the tool cuts the workpiece, the load torque is high. When the tool and the workpiece are released, that is, when the cutting of the workpiece ends, the load torque decreases (the fall of the load torque).

[0040] The position detection unit 18 detects the position of the workpiece machining surface based on the change in the value of the machining data. The detection method varies according to the machining data. When the machining sound is used as the machining data, the position of the machining surface is detected based on the sound when the tool contacts the workpiece, the sound when the tool cuts the workpiece, the sound when the tool idles, etc. When the vibration is set as the machining data, the position of the machining surface is detected based on the vibration when the tool contacts the workpiece, the vibration when the tool cuts the workpiece, the vibration when the tool idles, etc. When the heat is set as the machining data, the position of the machining surface is detected based on the heat when the tool contacts the workpiece, the heat when the tool cuts the workpiece, etc.

[0041] The position of the machining surface detected by the position detection unit 18 is stored as the detection position 19. The position information of the machining surface stored as the detection position 19 becomes the analysis object of the program analysis unit 12. Since the position detection unit 18 of the numerical control device 100 of this method automatically detects the position of the machining surface, the numerical control device 100 can automatically grasp the position of the cutting surface of the workpiece, and there is no need for a processing step such as aligning the tool position with the workpiece center before polygon machining or subsequent machining.

[0042] Next, refer to Figure 4 Describe the numerical controller 100a as another method of the present disclosure. The position detection unit 18a of the numerical control device 100a has a cutting start detection unit 21 that detects the start of cutting of the machining surface based on the machining data, and a machining surface center detection unit 22 that calculates the center of the machining surface of the workpiece based on the position of the workpiece axis when the cutting start is detected.

[0043] The cutting start detection unit 21 detects the start of cutting of the workpiece based on the change in the machining data, but the detection method of the cutting start varies according to the type of the above machining data (load torque, machining sound, vibration, heat, etc.). At the position of the cutting start, the position (angle) of the rotation axis of the workpiece at the start of cutting is set as A.

[0044] Figure 5A method for calculating the angle α from the position A of the tool rotation axis when starting to cut the workpiece to the center of the machining surface is shown. If the outer shape of the tool (tool correction amount) is set as R, the outer shape of the workpiece (diameter of the workpiece before polygon machining) is set as D, and the cutting amount of the tool is set as X, then the triangle connecting the center of the rotation axis of the workpiece, the center of the rotation axis of the tool, and the cutting start point is a triangle with side lengths of R, D, and R + D - X. The side connecting the center of the rotation axis of the workpiece and the center of the rotation axis of the tool passes through the center of the machining surface of the workpiece, so the angle α formed by this side and the side with length D becomes the difference from the cutting start position to the center of the machining surface.

[0045] This angle α can be calculated as follows using the cosine theorem.

[0046] R 2 = D 2 +(R + D - X) 2 - 2D(R + D - X)cosα ※ Cosine theorem

[0047] cosα = ((R + D - X) 2 - R 2 + D 2 ) / (2D(R + D - X))

[0048] α = arccos(((R + D - X) 2 - R 2 + D 2 ) / (2D(R + D - X)))

[0049] The position detection unit 18a adds α to the angle A detected at the start of cutting, and obtains the center of the machining surface (A + α).

[0050] Next, refer to Figure 6 A numerical control device 100b as another embodiment of the present disclosure will be described. The position detection unit 18b of the numerical control device 100b includes a cutting start detection unit 21 that detects the contact between the tool and the workpiece, a cutting end detection unit 23 that detects the release of the tool and the workpiece, and a machining surface center detection unit 22 that detects the center of the machining surface based on the cutting start position and the cutting end position.

[0051] Figure 7A method for the position detection unit 18b to detect the center of the machining surface. Here, the load torque is used as the machining data, and the machining surface of the workpiece is detected based on the position of the rotation axis of the workpiece (hereinafter referred to as the workpiece axis). In the non-cutting state where the tool and the workpiece are not in contact, since the load applied to the workpiece rotation axis is low, the load torque changes at a low value. When the workpiece contacts the tool, the load torque rises, and the position A of the workpiece axis at this time is called the cutting start position. The workpiece and the tool rotate simultaneously, and when the workpiece disengages from the tool (is released), the load torque decreases. At this time, the position B of the workpiece axis is called the cutting end position. Since the center of the machining surface is the middle of the cutting start position and the cutting end position, the position detection unit 18b uses the following formula to calculate the center P of the machining surface.

[0052] P = A + (B - A) / 2

[0053] Figure 8 The numerical control device 100c shown has a function of improving the accuracy of the machining surface center P by calculating the representative value. The position detection unit 18c of the numerical control device 100c includes a machining surface number detection unit 24 that detects the number of machining surfaces formed on the workpiece and a representative value calculation unit 25 that calculates the representative value of the detected centers of multiple machining surfaces. The numerical control device 100c calculates the machining surface center multiple times and sets the average value as the representative value.

[0054] In addition, the cutting start detection unit 21, the cutting end detection unit 23, and the machining surface center detection unit 22 have the same functions as the existing numerical control device 100b. Therefore, the same reference numerals are added, and their descriptions are omitted.

[0055] Figure 9 The case of a multi-cutting tool is shown. In Figure 9 (a), the tool moves while rotating along the long axis (Z axis) of the workpiece to perform polygon machining. Figure 9 (c) shows the change in the load torque during polygon machining. In polygon machining, the load torque rises and falls each time a machining surface is formed. The number of faces of the polyhedron is equal to the number of times the load torque rises (or falls) during one rotation (360°) of the workpiece axis. When the load torque rises m times during one rotation of the workpiece axis, the number of faces of the polyhedron formed on the workpiece axis is m.

[0056] If the number of faces of the polyhedron is known, the machining data can be corresponded to the machining surfaces. For example, if the number of faces of the polyhedron is m, the machining is repeated from the 1st face to the mth face. In this embodiment, the cutting start position is represented as A ij and the cutting end position is represented as B ij and the machining surface center is represented as P ij . The additional subscripts ij represent the rotational speed and the number of faces. For example, A11 is the first surface after one revolution, A 12 is the second surface after one revolution, ……, A nm is the cutting start position of the m-th surface after n revolutions. B 11 is the first surface after one revolution, B 12 is the second surface after one revolution, ……, B nm is the cutting end position of the m-th surface after n revolutions.

[0057] And, P 11 is the position of the machining surface center of the first surface in the first revolution, P 12 is the position of the machining surface center of the second surface in the first revolution, ……, P nm represents the machining surface center of the m-th surface in the n-th revolution.

[0058] The representative value calculation unit 25 uses the values P of the machining surface centers detected by the machining surface center detection unit 11 , ……, P nm to obtain the representative value (here, the average value) of each machining surface center. The formula for calculating the average value is as follows.

[0059] Machining surface center P1 (average of the first surface) = (P 11 + P 21 + … + P n1 ) / n

[0060] Machining surface center P2 (average of the second surface) = (P 12 + P 22 + … + P n2 ) / n

[0061] ……

[0062] Machining surface center Pm (average of the m-th surface) = (P 1m + P 2m + …… + P nm ) / n ※ n: rotational speed When the workpiece axis rotates n times like this (or when using n amounts of machining data), the sum of the center positions of each machining surface is divided by the rotational speed n to obtain the average value.

[0063] As the representative value, in addition to the average value, statistical quantities such as the median or the most frequent value can also be used. Additionally, the deeper the cut, the higher the accuracy, so instead of using the initially detected machining data, machining data after a certain number of times can also be used. The machining data can be weighted.

[0064] In addition, as Figure 9As shown in (b), there is also a machining process in which cutting is performed multiple times while fixing the Z axis, and the cutting depth in the X-axis direction is gradually increased. Even in such a machining process, the center of the machining surface can be detected multiple times, and the representative value of the detected center of the machining surface can be calculated.

[0065] Figure 8 The numerical control device 100c records the value of the center of the machining surface as the detection position. In this example, the positions of the centers P1 to P6 of the six surfaces 1 to 6 formed on the workpiece surface are stored as variables #3301 to #3306. By storing them as variables, the position of the center of the machining surface automatically detected can be referred to by the program and can be used in subsequent machining after polygon machining.

[0066] Figure 10 This is an example of a program using variables. In Program Example 1, the C axis is moved to #3301 (the center of surface P1) by "G00 C#3301" to determine surface P1, and the C axis is moved to #3304 (the center of surface P4) by "G00 C#3304" to determine surface P4. "G00 C[#3305 + 30.0]" moves the C axis to the position obtained by adding 30 degrees to #3305 (the center of surface P5) to determine surface P5 + 30 degrees.

[0067] Figure 10 Program Example 2 of this generates dedicated commands P1, P2,..., Pm for determination. The commands P1, P2,..., Pm correspond to the center positions P1, P2,..., Pm of the machining surface. The C axis is moved to the center of surface P1 by "G00 C00P1" to determine surface P1, the C axis is moved to the center of surface P4 by "G00 C00 P4" to determine surface P4, and the C axis is moved to the position obtained by adding 30 degrees to the center of surface P5 by "G00 C00 P5Q30.0" to determine surface P5 + 30 degrees.

[0068] Next, referring to Figure 11 This describes the numerical control device 100d as another embodiment of the present disclosure. The position control unit 18d of this numerical control device 100d has an axis conversion unit 26 that converts the position of the tool axis into the position of the workpiece axis. In this example, the axis conversion unit 26 performs an axis conversion process from the cutting surface center P' of the tool axis to the machining surface center P'' of the workpiece axis. The cutting surface center of the tool axis is the center position (angle) of the position (angle) where the tool starts cutting and the position (angle) where it ends. The cutting surface center detection unit 27 uses machining data to detect the cutting start position and the cutting end position. The detection method is the same as that of Figure 6 the machining surface center detection unit 22 of this.

[0069] The following represents the cutting center P′ for two revolutions of the tool (one revolution of the workpiece). 11 ~P′ 22 The formula for this is as follows. Here, it is expressed using the cutting start position A′ of the tool lk , the cutting end position B′ lk , and the cutting surface center P″ lk . The suffix lk represents the rotational speed l of the tool and the cutting surface k machined by the tool. In the case of more than two revolutions, the cutting center can also be obtained in the same way.

[0070] P11′ = A11′ + (B11′ - A11′) / 2

[0071] P12′ = A12′ + (B12′ - A12′) / 2

[0072] P13′ = A13′ + (B13′ - A13′) / 2

[0073] P21′ = A21′ + (B21′ - A21′) / 2

[0074] P22′ = A22′ + (B22′ - A22′) / 2

[0075] P23′ = A23′ + (B23′ - A23′) / 2

[0076] The axis conversion unit 26 performs (1) the conversion of the rotational speed and the cutting surface (machined surface), and (2) the conversion of the position (angle).

[0077] (1) In the conversion of the rotational speed and the cutting surface (machined surface), the rotational speed l of the tool axis is converted to the rotational speed j of the workpiece axis, and the cutting surface k of the tool axis is converted to the machined surface i of the workpiece axis. In polygon machining, the relationship (rotational speed l of the tool axis) × (number of cuts h per revolution) + (cutting surface k of the tool axis) = (number of machined surfaces m) × (rotational speed j of the workpiece axis) + (machined surface i of the workpiece axis) holds between the tool axis and the workpiece axis. Further, since the rotation ratio between the tool axis and the workpiece axis is fixed and the number of cuts h per revolution of the tool axis is the same as the number of tool blades, when the rotational speed l of the tool axis and the cutting surface k of the tool are determined, the rotational speed j of the workpiece axis can be converted to the machined surface i of the workpiece.

[0078] (2) In the conversion of the position (angle), the rotation ratio between the tool axis and the workpiece axis is used, and the position of the workpiece axis relative to the tool axis is used. For example, when the rotation ratio between the tool axis and the workpiece axis is R:S, if the position (angle) of the tool axis is multiplied by S / R, the rotation amount of the workpiece axis is obtained. If the initial phase difference θ between the tool axis and the workpiece axis is added to this value, the conversion from the position of the tool axis to the position of the workpiece axis can be performed.

[0079] In Figure 12 the example, the rotation ratio of the tool axis to the workpiece axis is 2:1, so S / R is 1 / 2, and the conversion formula is as follows. In this example, the machining data for two rotations of the tool axis is converted into the machining data for one rotation of the workpiece axis. Additionally, in this example, the machining center position of the tool axis is converted into the machining center position of the workpiece axis, but it is also possible to transform the cutting start position A' and the cutting end position B' of the tool axis into the cutting start position and the cutting end position of the workpiece axis.

[0080] P 11 ″ = θ + P 11 ′ / 2

[0081] P 12 ″ = θ + P 12 ′ / 2

[0082] P 13 ″ = θ + P 13 ′ / 2

[0083] P 14 ″ = θ + P 21 ′ / 2

[0084] P 15 ″ = θ + P 22 ′ / 2

[0085] P 16 ″ = θ + P 23 ′ / 2

[0086] In Figure 12 (c)'s formula, the machining surface center Pi when rotating the workpiece n times is obtained. The machining surface center Pi is the machining surface center P detected from the machining data of the workpiece axis ij and the average of converting the cutting surface center P' of the tool axis ij into the machining surface center P″ of the workpiece axis ij . The average calculation formula is as follows (n is the rotational speed of the workpiece axis).

[0087] Machining surface center P1 (the first surface) = (P 11 +……+Pn1+P 11 ″+……+P n1 ″) / 2n

[0088] Machining surface center P2 (the second surface) = (P 12 +……+P n2 +P 12 ″+……+P n2 ″) / 2n

[0089] ……

[0090] Here, based on the machining surface center P detected from the machining data of the workpiece axis ij and the cutting surface center P' of the tool axis ij changed to the machining surface center P" of the workpiece axis ij The average is calculated based on the sum, but the average of either one can also be calculated.

[0091] Next, refer to Figure 13 to describe the numerical control device 100e as another embodiment of the present disclosure. The cutting start detection unit 21e and the cutting end detection unit 23e of the numerical control device 100e perform error prevention detection processing.

[0092] Figure 14 It shows the error prevention detection processing when using the load torque as the machining data. The numerical controller 100e sets two values, the non-contact state level (L1) and the contact state detection level (L2).

[0093] The non-contact state level (L1) is, for example, the average value of the load torque in the non-contact state (the average load torque from after reaching the specified rotation speed to before the start of cutting).

[0094] The cutting level (L2) is the threshold value of the load torque for determining whether the tool is in the cutting state. For example, the cutting state level (L2) has a value obtained by adding a predetermined value a to the non-cutting state level (L1) and a load level of b% of the non-cutting state level (L1). The cutting state level (L2) can be an experimental value obtained based on actual machining data. The cutting state level (L2) may be an appropriate value for preventing false detection.

[0095] The cutting start detection unit 21e detects the angle Aa of the workpiece axis when the load torque reaches the cutting state level (L2) and the angle Ab of the workpiece axis when the load torque reaches the non-cutting level (L1) before Aa. The cutting start detection unit 21e classifies the displacement of the load torque between Aa and Ab into two modes, mode 1-1 and mode 1-2. In mode 1-1, the load torque increases and decreases between the angles Aa and Ab. At this time, the angle when the load torque changes from negative to positive is selected as the cutting start angle A. In mode 1-2, the load torque monotonically increases between the angles Aa and Ab. At this time, the angle Ab when the load torque reaches the non-cutting level (L1) is selected as the cutting start angle A.

[0096] The cutting end detection unit 23e monitors the load torque and detects the angle Ba when the load torque drops to the cutting state level (L2) and the angle Bb when it becomes the non-cutting level (L1) after Ba. The cutting end detection unit 23e classifies the displacement of the load torque between Ba and Bb into two modes, mode 2-1 and mode 2-2. In mode 2-1, the load torque increases and decreases between the angles Ba and Bb. At this time, the angle at which the load torque changes from positive to negative is selected as the cutting end angle B. In mode 2-2, the load torque monotonically decreases between the angles Ba and Bb. At this time, the angle Bb at which the load torque reaches the non-cutting level (L1) is selected as the cutting end angle B.

[0097] Fluctuations generated when the tool contacts or releases the workpiece may cause false detection. The cutting start detection unit 21e and the cutting end detection unit 23e classify the change patterns of the machining data that occur during contact or release and select the values to be detected according to this pattern, so false detection can be prevented.

[0098] Next, refer to Figure 15 to describe the operation of the numerical control device 100c.

[0099] The numerical control device 100c performs polygon machining. The machining data acquisition unit 16 acquires the machining data (here, the load torque) of the machine tool to be controlled and the position of the workpiece axis (or tool axis) at this time. The machining data storage unit 17 stores the machining data in a state associated with the position of the workpiece axis (step S1).

[0100] The cutting start detection unit 21 of the position detection unit 18c detects the cutting start angle At from the machining data stored in the machining data storage unit 17. The cutting end detection unit 23 detects the cutting end angle Bt from the machining data stored in the machining data storage unit 17 (step S2). Here, t is the number of detections of the angle A or the angle B.

[0101] The machining surface center detection unit 22 detects the center angle Dt of the machining surface based on the cutting start angle At and the cutting end angle Bt. The formula for detecting the machining surface center is Dt = At + (Bt - At) / 2 (step S3).

[0102] The machining surface number detection unit 24 counts the number of machining surface centers Dt detected within the range of the first one revolution (0 to 360 degrees) of the workpiece axis. The number of machining surface centers Dt detected in one revolution corresponds to the number of machining surfaces m (step S4).

[0103] The representative value calculation unit 25 converts the value of the machining surface center Dt to P ij . P ij The suffix i of P represents the rotational speed, and the suffix j represents the machining surface.Figure 16 (b) means D t Convert to P ij situation.

[0104] Because D1~D m It is the first rotation, so P 11 ~P 1m , D m+1 ~D m+m It is the second rotation, so P 21 ~P 2m , D (n-1) ×m~D n*m It is the nth rotation, so it is converted to P n1 ~P nm (Step S5).

[0105] The representative value calculation unit 25 calculates the processing surface center D t After classifying by rotation speed and machining surface, the average value of the machining surface center is calculated. Figure 16 (c) is the calculation formula for calculating the average value of the center of the machined surface. Find the P equal to the additional character j ij The sum of the two is divided by the speed n, and the average value P of the center of the machining surface is obtained. j .

[0106] The calculated values ​​P1, ..., P m The detected position is stored (step S6).

[0107] Figure 17 Is to make the machine tool implement Figure 15 An example of a program for the actions shown in the flowchart. In this program, after positioning the tool axis by "G00X100.0Z20.0S1000M03", the polygonal machining is started by "G51.2 P1 Q2". Cut into the X-axis by "G01X80.0F10.0", wait for 2 seconds by "G04X2.0", retract the X-axis by "G00X100.0", end the polygonal machining by "G50.2", and stop the workpiece axis by "S0M05". This process corresponds to step S1 of the flowchart. The numerical control device 100 detects the position of the machining surface based on the machining data collected here, and records the detection result as a variable (here #3301 to #330m).

[0108] After that, subsequent machining after the end of polygon machining is indicated in the program. The machine tool selects the tool (drill bit) for subsequent machining by "T2". The tool axis is positioned by "G00X50.0". The C axis (workpiece axis) is determined for the machining surface center of the variable "#3301", i.e., the P1 surface, by "G83C#3301X-40.0F5.0", and drilling is performed on the machining surface center by the X axis. Similarly, drilling is performed on the machining surface center of the variable "#3302", i.e., the P2 surface, by "C#3302". Drilling is performed on the surface that is inclined 30 degrees from the machining surface center of the variable "#3305", i.e., the P5 surface, by "C[#3305+30.0]". The fixed cycle is stopped by "G80M5", and the main spindle is stopped. Finally, the program is ended by "M30". If the position of the machining surface center is stored as a variable in this way, the processing of polygon machining and subsequent machining can be described in one program.

[0109] In this way, the numerical control devices 100 to 100e of the present embodiment acquire the data during polygon machining, detect the position of the machining surface formed on the workpiece based on the machining data, and thus can use the detected position information to position the workpiece. Therefore, there is no need for processing operations such as aligning the tip position of the tool with the workpiece center.

Claims

1. A control device controls a machine tool. The machine tool has a first axis for rotating a tool and a second axis for rotating a workpiece, and rotates the first axis and the second axis to machine the workpiece into a polygon. It is characterized in that the control device includes: a machining data acquisition unit that acquires machining data that changes with the machining of the workpiece; and a position detection unit that detects the position of the second axis when the workpiece contacts the tool and the position of the second axis when the workpiece releases from the tool by the change of the machining data, and detects the center of the position of the second axis when the workpiece contacts the tool and the position of the second axis when the workpiece releases from the tool as the intermediate angle between the cutting start angle and the cutting end angle of the second axis after the machining surface of the workpiece is machined.

2. A control device controls a machine tool. The machine tool has a first axis for rotating a tool and a second axis for rotating a workpiece, and rotates the first axis and the second axis to machine the workpiece into a polygon. It is characterized in that the control device includes: a machining data acquisition unit that acquires machining data that changes with the machining of the workpiece; and a position detection unit that detects the contact between the workpiece and the tool by the change of the machining data, and detects the intermediate angle between the cutting start angle and the cutting end angle of the second axis after the machining surface of the workpiece is machined based on at least one of the position of the first axis and the position of the second axis when the contact between the workpiece and the tool is detected and the cutting depth of the tool into the workpiece.

3. The control device according to claim 1 or 2, characterized in that the machining data acquisition unit acquires data of multiple contacts between the workpiece and the tool, and the position detection unit uses all or part of at least one of the position of the first axis and the position of the second axis during the multiple contacts to detect the position of the machining surface.

4. The control device according to claim 1 or 2, characterized in that the machining data acquisition unit detects data of multiple releases between the workpiece and the tool, and the position detection unit uses all or part of the position of at least one of the first axis and the second axis during the multiple releases to detect the position of the machining surface.

5. The control device according to claim 1 or 2, characterized in that the control device includes a machining surface number detection unit that counts the number of changes in the machining data during one rotation of the second axis and detects the number of machining surfaces formed on the workpiece.

6. The control device according to claim 1 or 2, characterized in that the control device includes an axis position conversion unit that converts the position of the first axis into the position of the second axis or converts the position of the second axis into the position of the first axis based on the rotation ratio between the first axis and the second axis.

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