Control device and control system of machine tool

Abstract

A control device controls polygon machining in which a workpiece and a tool are rotated simultaneously to form a polygon on the surface of the workpiece. The control device inputs information related to the deviation of the rotational direction of a cutting tool (T) mounted on a tool body, generates an adjustment pulse for correcting the deviation of the rotational direction of the cutting tool (T), and generates a rotation command for rotating a tool axis for performing polygon machining at a predetermined angular velocity. Moreover, when the tool is idling, the generated adjustment pulse is superimposed on the generated rotation command to correct the deviation of the rotational direction of the cutting tool (T), thereby improving the accuracy of polygon machining.

Description

Technical Field

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

[0002] Conventionally, there has been a type of polygon machining in which a workpiece is machined into a polygon shape by rotating a tool and a workpiece at a fixed ratio. In polygon machining, the tool tip describes an elliptical orbit relative to the workpiece. By changing the rotation ratio of the workpiece and the tool and the number of tools, the phase and number of the ellipses change, and the workpiece can be machined into a polygon such as a quadrilateral or a hexagon.

[0003] Figure 11A This shows the movement path of the tool tip relative to the workpiece when the center of the workpiece is the origin. In this example, the rotation speed ratio of the workpiece and the tool is 1:2, and the number of tools is 2. The movement path of tool T1 relative to the workpiece is orbit 1, and the movement path of tool T2 relative to the workpiece is orbit 2. During one rotation of the workpiece, the two tools T1 and T2 describe elliptical orbits around the workpiece, and a quadrilateral is formed on the workpiece surface. Figure 11B This is the movement path of tool T when the rotation ratio is 1:2 and the number of tools is 3. In this case, the three tools describe elliptical orbits around the workpiece, and if the workpiece surface is cut along this orbit, a hexagon is formed.

[0004] A tool for performing polygon machining is called a polygon cutter and is composed of a tool body and a cutting tool mounted on the tool body. Patent Document 1 describes the following: The polygon machining tool is composed of an annular cutter body, three cutting blades, three fixing bolts provided to fix these three blades respectively, and a positioning bolt for positioning adjustment of the tool tip of the blade.

[0005] In the machining tool (equivalent to a polygon cutter) of the above Patent Document 1, when the blade (equivalent to a cutting tool) is arranged and fixed in the hole of the cutter body, one cutting edge is installed to protrude from the outer peripheral surface of the tool body. When the cutting edge is fixed with the fixing bolt, its fastening force prevents the blade from rotating in the hole.

[0006] In the machining tool of Patent Document 1, by adopting a structure in which the blade is mounted on the cutter body, the tool diameter can be increased without increasing the tool mechanism, and the accuracy of polygon machining can be improved. In addition, by providing a positioning bolt and a fixing bolt, the positioning adjustment function of the cutting tool is improved.

[0007] Prior Art Documents

[0008] Patent Documents

[0009] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2018-140482 Summary of the Invention

[0010] Problems to be Solved by the Invention

[0011] In the processing tool of Patent Document 1, a positioning bolt and a fixing bolt are provided, which improve the positioning accuracy of the tool. However, the installation of the tool is carried out manually, so sometimes there are some offsets in the installation position. In addition, in polygon machining, each tool rotates while repeatedly performing cutting and idling. However, due to the load when the tool contacts the tool, there are sometimes offsets in the installation position and tool deformation. The offsets in the installation position and tool deformation will affect the accuracy of the machining shape.

[0012] In addition, as Figure 11A and Figure 11B shown, polygon machining is performed by combining ellipses to form a polygon, so the cutting surface becomes a gentle curve, which is not suitable for high-precision machining that requires high flatness. Compared with polygon machining using a milling machine or the like, polygon machining takes less time. Therefore, it is practically used for machining parts (such as the head of a bolt and the drill bit of a screwdriver) that do not pose an obstacle even if they are not highly precise.

[0013] However, if the accuracy of polygon machining can be improved, high-precision machining can be performed in a shorter machining time.

[0014] In the field of polygon machining, a technique for improving accuracy is desired.

[0015] Means for Solving the Problems

[0016] One disclosure of the present invention is a control device for controlling polygon machining, where the polygon machining is to rotate a workpiece and a tool simultaneously to form a polygon on the surface of the workpiece. The control device includes: a workpiece axis command generation unit that generates a command for the angular velocity of the workpiece; a tool axis command generation unit that generates a command for the angular velocity of the tool; an offset acquisition unit that acquires information related to the offset in the rotation direction of the tool mounted on the tool; an adjustment amount generation unit that generates a pulse for adjusting the phase of either or both of the tool axis and the workpiece axis based on the information related to the offset in the rotation direction of the tool acquired by the offset acquisition unit; and an adjustment amount superposition unit that superimposes the pulse on either or both of the command for the angular velocity of the workpiece and the command for the angular velocity of the tool.

[0017] Another aspect of the present invention is a control system for controlling polygon machining, where the polygon machining involves rotating both a workpiece and a tool simultaneously to form a polygon on the surface of the workpiece. The control system includes: a workpiece axis command generation unit that generates a command for the angular velocity of the workpiece; a tool axis command generation unit that generates a command for the angular velocity of the tool; an offset acquisition unit that acquires information related to the offset in the rotation direction of a cutting tool mounted on the tool; an adjustment amount generation unit that generates a pulse for adjusting the phase of either or both of the tool axis and the workpiece axis based on the information related to the offset in the rotation direction of the cutting tool acquired by the offset acquisition unit; and an adjustment amount superposition unit that superimposes the pulse on either or both of the command for the angular velocity of the workpiece and the command for the angular velocity of the tool.

[0018] Advantages of the Invention

[0019] According to the present disclosure, the accuracy of polygon machining can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a hardware configuration diagram of the numerical control device in the present disclosure.

[0021] Figure 2 is a block diagram of the control system in the present disclosure.

[0022] Figure 3 is a diagram showing an example of calculating the adjustment amount for three cutting tools.

[0023] Figure 4A is a diagram showing an example of a tool with no offset in the rotation direction (ideal state).

[0024] Figure 4B is a diagram showing an example of a tool with an offset in the rotation direction (state with offset).

[0025] Figure 5 is a diagram showing the change in the angle of the tool axis when correcting the offset in the rotation direction.

[0026] Figure 6A is a diagram showing the track change of the cutting tool in the present disclosure.

[0027] Figure 6B is a diagram showing the track change of the cutting tool in the present disclosure.

[0028] Figure 7A is a diagram showing the shape change of the machined product due to the offset of the cutting tool.

[0029] Figure 7B is a diagram showing the shape change of the machined product due to the offset of the cutting tool.

[0030] Figure 8This is a diagram showing the shape change of the processed product due to the offset of the tool.

[0031] Figure 9 This is a block diagram of the numerical control device in the third disclosure.

[0032] Figure 10 This is a diagram showing the relationship between the change in load torque and the adjustment time of the offset amount.

[0033] Figure 11A This is a diagram explaining the conventional polygon machining.

[0034] Figure 11B This is a diagram explaining the conventional polygon machining. Detailed implementation mode

[0035] Hereinafter, an example of the numerical control device 100 having an adjustment function for polygon machining is shown. As Figure 1 shown, the numerical control device 100 includes a CPU 111 that integrally controls the numerical control device 100, a ROM 112 that records programs and data, and a RAM 113 that temporarily expands data. The CPU 111 reads out the system program recorded in the ROM 112 via the bus 120 and controls the overall numerical control device 100 according to the system program.

[0036] The non-volatile memory 114 is backed up by a battery (not shown), for example, and maintains the storage state even when the power of the numerical control device 100 is turned off. Programs read from an external device 72 via the interfaces 115, 118, 119, user operations input via the input unit 30, and various data (such as set parameters, sensor information, etc.) obtained from each part of the numerical control device 100, the machine tool 200, etc. are stored in the non-volatile memory 114.

[0037] The interface 115 is an interface for connecting the numerical control device 100 and an external device 72 such as an adapter. Programs, various parameters, etc. are read from the external device 72 side. In addition, programs, various parameters, etc. edited in the numerical control device 100 can be stored in an external storage unit via the external device 72. The PLC 116 (programmable logic controller) controls the input and output of signals via the I / O unit 117 between the machine tool 200, the robot, and devices such as sensors installed on the machine tool 200 and the robot through a sequence program built into the numerical control device 100.

[0038] The operation screen of the machine tool 200, the display screen showing the operating state of the machine tool 200, etc. are displayed on the display unit 70. The input unit 30 is composed of an MDI, an operation panel, a touch panel, etc., and transmits the operation input of the operator to the CPU 111.

[0039] The servo amplifier 140 controls each axis of the machine tool 200. The servo amplifier 140 receives the axis movement command amount from the CPU 111 to drive the servo motor 150. The servo motor 150 is built-in with a position and speed detector, and feeds back the position and speed feedback signal from the position and speed detector to the servo amplifier 140 to perform position and speed feedback control. A tool axis is installed on the servo motor 150. A plurality of cutting tools T for performing polygon machining are installed on the tool body.

[0040] The spindle amplifier 161 receives the spindle rotation command for the spindle 164 of the machine tool 200 and drives the spindle motor 162. The power of the spindle motor 162 is transmitted to the spindle 164 via gears, and the spindle 164 rotates at the commanded rotational speed. The spindle 164 is coupled with a position encoder 163, and the position encoder 163 outputs feedback pulses synchronously with the rotation of the spindle 164, and the feedback pulses are read by the CPU 111.

[0041] A workpiece W is installed on the spindle 164. The spindle 164 is parallel to the axial direction of the tool axis, and the spindle 164 and the tool axis rotate at a predetermined rotation ratio. When the spindle 164 and the tool axis rotate simultaneously, the tool U installed on the tool axis cuts the workpiece surface, and a polygon is formed on the workpiece surface.

[0042] [First Publication]

[0043] Figure 2 It is a block diagram of the control system 1000 in the first publication. The functions within this block diagram are realized by the CPU 111 of the numerical control device 100 executing programs recorded in storage devices such as the ROM 112.

[0044] The numerical control device 100 is equipped with a polygon machining control unit 10. The polygon machining control unit 10 is equipped with a workpiece axis command generation unit 11 for generating a rotation command for the workpiece axis and a tool axis command generation unit 12 for generating a rotation command for the tool axis.

[0045] The workpiece axis command generation unit 11 generates a rotation command for the spindle 164. The workpiece axis command generation unit 11 generates a command to rotate the spindle 164 at a fixed angular velocity ω and outputs it to the spindle amplifier 161. The spindle amplifier 161 controls the spindle motor 162 according to the command from the workpiece axis command generation unit 11. The spindle motor 162 rotates the spindle 164 at a fixed angular velocity ω. Thereby, the workpiece W installed on the spindle 164 rotates at a fixed angular velocity ω.

[0046] The tool axis command generation unit 12 generates a rotation command for the tool U. The tool axis command generation unit 12 generates a command to rotate the tool U at a fixed angular velocity and outputs it to the servo amplifier 140. The servo amplifier 140 controls the servo motor 150 according to the command from the tool axis command generation unit 12. The servo motor 150 rotates the tool U at a fixed angular velocity according to the control of the servo amplifier 140.

[0047] The tool axis command generation unit 12 includes a phase shift acquisition unit 13, an adjustment amount generation unit 14, and an adjustment amount superposition unit 15.

[0048] The first disclosed phase shift acquisition unit 13 acquires information related to the offset in the rotation direction of the cutting tool T. The offset amount δ in the rotation direction of the cutting tool T is the difference between the actual angle and the ideal angle. The angle of the cutting tool T can be measured using a laser displacement meter, an angle meter, an image measuring machine, etc., but the measurement method is not specified. The measurement result is input to the phase shift acquisition unit 13.

[0049] The adjustment amount generation unit 14 calculates the adjustment amount γ for each cutting tool T i of the offset amount δ i and generates a pulse corresponding to the calculated adjustment amount γ i . i

[0050] The adjustment amount superposition unit 15 superposes the pulse generated by the adjustment amount generation unit 14 on the rotation command generated by the tool axis command generation unit 12 in accordance with the idle timing of polygon machining. The idle timing of polygon machining refers to the time when the cutting tool T of the tool U is idling without cutting the workpiece W. The adjustment amount superposition unit 15 superposes the pulse during the idle timing to shift the phase of the tool axis by the adjustment amount γ i of the cutting tool (assumed to be T i ) for the next cutting, and performs phase alignment. Thereby, the offset in the rotation direction of the cutting tool T i is corrected.

[0051] [Calculation method of adjustment amount γ]

[0052] The following formula is the calculation formula for the adjustment amount γ. In the present disclosure, by using the following formula, the adjustment amount γ can be calculated regardless of the number N of cutting tools T and the offset amount δ of the cutting tool.

[0053] When the counterclockwise direction is set as the positive direction (plus), the adjustment amount γ i for the offset amount δ i of each cutting tool T i becomes the following formula:

[0054] γ i = δ i-1 - δ i

[0055] Among them, in the above formula, γ 1 = δ N − δ 1 (N is the number of tools T), in addition, the adjustment amount γ i for the first cutting is -δ i .

[0056] When calculating the adjustment amount γ i in this way, in the initial cutting, if the phase of the tool axis is adjusted by -δ i , then the offset of the tool T i +δ i is canceled out and becomes zero. At the end of the cutting of the tool T i , the phase of the tool axis is offset by -δ i , so if the phase of the tool axis is adjusted by δ i − δ i+1 , then the offset of the phase of the tool axis becomes -δ i+1 , and the offset of the tool T i+1 +δ i+1 is canceled out and becomes zero. At the end of the cutting of the tool T i+1 , the phase of the tool axis is offset by -δ i+1 , so if the phase of the tool axis is adjusted by δ i+1 − δ i+2 , then the offset of the phase of the tool axis becomes −δ i+2 , and the offset of the tool T i+2 +δ i+2 is canceled out and becomes zero. The tool T i rotates, corresponding to the offset δ i of the tool T i , the adjustment amount γ i changes periodically.

[0057] As a specific example, referring to Figure 3 , for the offsets δ 1 , δ 2 , δ 3 of the three tools T 1 , δ 2 , δ 3 , the calculation methods of the adjustment amounts γ 1 , γ 2 , γ 3 are described. When there are three tools T, for each tool T i , the adjustment amounts (γ 1 , γ 2 , γ 3 ) become (γ 1 , γ 2 , γ3 ) = (δ 3 −δ 1 , δ 1 −δ 2 , δ 2 −δ 3 | only for the first cutting −δ i ).

[0058] In Figure 3 's example, in the first pass, cutting is performed by the tool T 1 . In this case, the adjustment amount for the first cutting is -δ 1 . Therefore, the phase of the tool axis is offset by −δ 1 . After the first cutting, the adjustment amount γ i can be calculated based on the tool T i performing the cutting. As Figure 3 shows, the adjustment amount γ i corresponds to the tool T i performing the cutting. As (γ 1 , γ 2 , γ 3 ) = (δ 3 −δ 1 , δ 1 −δ 2 , δ 2 −δ 3 ), it changes periodically.

[0059] Figure 4A and Figure 4B represent the tool U with an offset, Figure 5 represents the angular change of the tool axis when correcting the offset, Figure 6A and Figure 6B represent the change in the machining surface when correcting the offset.

[0060] In Figure 4A and Figure 4B 's tool U, two tools T 1 , T 2 are equally spaced. When two tools T 1 , T 2 are installed, ideally, as Figure 4A shows, the angle between one tool T 1 and the other tool T 2 is 180 degrees. However, due to some reason, sometimes as Figure 4B shows, an offset in the rotation direction occurs. In this figure, with the left tool T 1 as the reference (offset amount δ 1 = 0), the right tool T 2 is offset by -δ (offset amount δ 2). If the offset (δ 1 , δ 2 )=(0, -δ), then the adjustment amount (γ 1 , γ 2 )=(δ 2 -δ 1 , δ 1 -δ 2 )=(-δ, +δ; where the adjustment amount for the first cutting is -δ i ).

[0061] Figure 5 Indicates correction Figure 4B The relationship between the angle of the tool axis and time when the offset is . The dotted line represents the conventional polygon processing, and the solid line represents the polygon processing of the present disclosure. In the conventional polygon processing, the angular velocity of the tool axis is fixed.

[0062] In the polygon processing of the present invention, when using the tool T 1 When starting cutting, the adjustment amount γ due to the first cutting 1 =0 (from time t1 to t2), the workpiece W is cut with the phase shift being zero. 2 When cutting, the angular velocity is accelerated to shift the phase by +δ during the idle timing (from time t2 to t3) before the start of cutting. In the second cutting (from time t3 to t4), the workpiece W is cut with the phase shifted by +δ. After the tool U rotates one turn, the tool T is used again. 1 When cutting is performed, the angular velocity is decelerated during the idle timing (time t4 to t5) before the start of cutting to return the phase shift to zero. In the third cutting (time t5 to t6), the workpiece W is cut with the phase shift at zero. Thereafter, the numerical control device 100 repeats the processing from t2 to t6.

[0063] In such Figure 5 When the phase is controlled in this way, the trajectory of tool T is as follows Figure 6A and Figure 6B Then use two tools T 1 , T 2 When cutting workpiece W, if tool T 1 , T 2 Installed in the ideal location, Figure 6A As shown by the dotted line, the quadrilateral S formed by polygon processing becomes a roughly square. 1 , T 2 The tool T of one side 2 When tilted, Figure 6A As shown by the dashed line, the inclined tool T 2The orbit is inclined, and the cutting tool T 2 The formed cutting surface is also inclined, thus becoming a rhombus.

[0064] Figure 6B The solid lines represent two cutting tools T in the polygon machining of the present invention 1 、T 2 's orbits. In the polygon machining of the present invention, during the idling timing when the cutting tool T 1 、T 2 is not cutting, the offset of the rotation direction is corrected. As a result, the orbits of the cutting tools T 1 、T 2 during cutting are consistent with the ideal orbits. Thus, the offset of the rotation direction of the cutting tool T is corrected, and the quadrilateral S formed by polygon machining becomes a substantially square.

[0065] [Second Disclosure]

[0066] [Measurement Method 1 of Offset δ]

[0067] In the second disclosure, the workpiece W obtained as a result of trial machining is used to calculate the offset δ of the rotation direction. As Figure 6A shown, the deviation amount of the machining surface of the workpiece W from the cutting tool T. Therefore, the offset δ of the rotation direction of the cutting tool T can be calculated using the angle θ formed by the machining surface of the workpiece W obtained as a result of trial machining.

[0068] The measurement of the workpiece W is performed by an operator, for example. The measuring devices include a laser displacement meter, an angle meter, an image measuring instrument, etc., but are not limited thereto. When measuring the angle of the workpiece W, the operator inputs the angle of the workpiece W to the numerical control device 100 via the input unit 30. The calculation of the offset δ is performed by the phase offset acquisition unit 13.

[0069] The following formula is the calculation formula for the offset δ. In the present disclosure, by using the following formula, the offset δ can be measured according to the angle θ of the workpiece W subjected to trial machining regardless of the number N of cutting tools. The calculation method of the offset δ using the angle θ of the workpiece W will be described.

[0070] In this example, a tool U with the number of cutting edges N is used, and rotation is performed at a rotation ratio of 1:2 between the workpiece axis and the tool axis. If polygon machining is performed under this condition, the outer shape of the workpiece becomes a regular 2N-sided polygon. Strictly speaking, polygon machining is to machine the workpiece surface through a combination of ellipses, so each surface becomes a smooth curved surface, and the outer diameter of the workpiece does not become a perfect regular 2N-sided polygon, but is regarded as a regular 2N-sided polygon here. When the machining surface is regarded as a regular 2N-sided polygon, the two opposite sides of the regular 2N-sided polygon are parallel to the major axis of the ellipse depicted by each cutting tool T. Let the cutting tool number be n (=1,..., N), and the cutting tool T with the cutting tool number n nThe formed cutting surface is designated as S n Using the same tool T n Two opposite surfaces are formed, but the cross-section observed from the workpiece axis direction is line-symmetric, so only one side of the surface will be described.

[0071] Let the angle formed by two adjacent surfaces S of a regular N-sided polygon n and S n+1 be θ n Regarding n = N, θ N is the angle formed by S N and S 1 In the case where the tool T has no offset, all the angles are (180 - 180 / N)° ( = θ). For simplicity, taking the tool T with n = 1 1 as a reference, let the offset of the rotation direction of each tool T n be δ n Since the reference is the tool with n = 1, δ 1 = 0. Due to the offset δ n of the tool T n , the machined surface S n formed by the tool T n is also inclined by the angle δ n , so for n (= 1,..., N - 1), it becomes θ n = θ + δ n - δ n+1 For n = N, it becomes θ n = θ + δ N - δ 1 Since θ and δ 1 are known, if the angle θ 1 formed by the surface S 1 formed by the reference tool T N and the surface S N formed by the tool T N is measured, then the offset δ N of the tool T N can be calculated. Similarly, if the angle θ n of the regular N-sided polygon is measured, then the offset δ n of each tool T n can be calculated according to the above formula.

[0072] As a specific example, the cases of two tools and three tools will be described. As Figure 4A and Figure 4B shown, if the tool U equipped with two tools T 1 , T 2 is rotated at a rotation ratio of 1:2 between the workpiece axis and the tool axis, the outer shape of the workpiece W becomes a square. As Figure 4A shown, in the tool T1 , T 2 , when installed in an ideal position, as Figure 7A shown, the angles of the four corners of the square are 90°. However, as Figure 4B shown, when the cutting tool T 2 is offset by δ in the rotational direction 2 , the surface S formed by the offset cutting tool T 2 is also inclined by an angle δ 2 , as 2 shown, and the angles of the opposite corners become θ Figure 7B = 90 - δ° and θ 1 = 90 + δ° of a rhombus. Therefore, if the angles θ 2 of the workpiece W obtained as a result of trial machining are substituted into the above formula, the offset δ 1 of the cutting tool T 2 can be calculated, and the adjustment amounts γ 2 and γ 2 can also be calculated. 1 2 .

[0073] When there are three cutting tools, the offset δ can also be calculated based on the angles of the workpiece W. When the cutting tools T 2 and T 3 are offset by δ 2 and δ 3 in the rotational direction 2 , the surfaces S 3 formed by the respective cutting tools T 2 and S 3 are also inclined by the angles δ 2 and δ 3 , as Figure 8 shown, and become θ 1 = 120 - δ 2 °, θ 2 = 120 + δ 2 - δ 3 °, θ 3 = 120 + δ 3 °. Therefore, the offsets δ 1 and δ 2 of the cutting tools T 3 can be calculated based on the angles θ 2 , θ 3 of the workpiece W obtained as a result of trial machining, and the adjustment amounts γ 2 and γ 3 can also be known. When there are four or more cutting tools, the calculation can be performed in the same manner. 2 3 .

[0074] Thus, in the second disclosure, as information related to the offset in the rotation direction of the tool, the angle θ of the polygon obtained as a result of trial machining is acquired, and the offset amount δ of each tool is calculated.

[0075] In the numerical control device 100 of the second disclosure, the offset amount δ in the rotation direction of the tool T can be detected based on the angle θ of the workpiece W obtained as a result of trial machining.

[0076] In addition, in the above description, it is configured that the operator measures the angle of the workpiece W and the numerical control device 100 calculates the offset amount δ, but it may also be configured that the operator calculates the offset amount and inputs it into the numerical control device 100.

[0077] [Third Disclosure]

[0078] [Adjustment Method 2 of Offset Amount δ]

[0079] In the third disclosure, the phase offset acquisition unit 13 uses the load torque to adjust the offset amount δ.

[0080] Figure 9 is a block diagram of the control system 1000 of the third disclosure. The numerical control device 100 of the third disclosure includes: a phase offset acquisition unit 13 that acquires information related to the offset in the rotation direction; an adjustment amount generation unit 14 that generates a pulse for correcting the offset amount δ based on the value of the load torque; an adjustment amount superposition unit 15 that superposes the pulse in accordance with the idling timing of the tool U; and a torque detection unit 16 that detects the load torque.

[0081] The torque detection unit 16 detects the load applied to the tool axis and outputs the detection result of the load torque to the phase offset acquisition unit 13.

[0082] The adjustment amount generation unit 14 detects the phase offset amount of the rotation direction of the tool T based on the change in the load torque acquired by the phase offset acquisition unit 13 and generates a pulse for correcting the offset. 1 With the tool T 2 and generates a pulse for correcting the offset.

[0083] Figure 10 is when using the tool T 1 to machine the workpiece W, and then using the tool T 2 The change in the load torque when machining the workpiece W. The load applied to the tool axis rises at the moment A1 when the tool T 1 contacts the workpiece W, remains at a relatively high level during the period when the tool T 1 machines the workpiece W, and drops at the moment B1 when the tool T 1 leaves the workpiece W. Then, at the moment A2 when the next tool T 2 contacts the workpiece W, it rises, and at the moment when the tool T 2During the cutting of the workpiece W, it remains at a high level and drops at the moment B2 when the tool T 2 leaves the workpiece W.

[0084] In the case of forming a regular polygon, since the sides of the same length are formed in sequence, the time from the rise of the load torque to the next rise should all be equal. In Figure 10 the example of, for the period Term1 from the start of cutting of the tool T 1 to the start of cutting of the tool T 2 and the period Term2 from the start of cutting of the tool T 2 to the start of cutting of the next tool T 1 ideally, the relationship is Term1 = Term2.

[0085] Conversely, in the case of Term1 ≠ Term2, a phase shift occurs. Therefore, the difference between Term1 and Term2 is obtained and used as the phase offset amount, and a pulse for correcting this time difference is generated.

[0086] The adjustment amount superposition unit 15 superposes the pulse generated by the adjustment amount generation unit 14 on the rotation command generated by the tool axis command generation unit 12 in matching with the idling timing of the polygon machining. The idling timing of the polygon machining can be detected based on the torque load. In Figure 10 the example of, during the period from the moment B1 when the torque load drops to the moment A2 when the next torque rises, the pulse for correcting the time difference between Term1 and Term2 is overlapped.

[0087] In this way, in the numerical control device 100 of the second disclosure, the load torque is used to detect and correct the offset of the tool. In this method, the offset can be automatically corrected in the state where the tool U and the workpiece W are mounted on the machine tool. In addition, in the case of forming a regular polygon, it is only necessary to make the time from the rise of the load to the rise of the next load fixed.

[0088] In addition, in the present disclosure, the period from the rise of the load to the next rise is set as the correction reference, but the drop of the load can also be set as the correction reference, and other timings can also be set as the correction reference.

[0089] As described above, the numerical control devices 100 of the present disclosures 1 to 3 generate a pulse corresponding to the offset amount δ in the rotation direction of the tool T and superpose the pulse on the rotation command of the tool axis, thereby being able to correct the offset of the tool T without adjusting the installation position of the tool T.

[0090] In the second disclosed numerical control device 100, the offset δ is calculated using the angle of the workpiece W obtained as a result of trial machining. Since the angle of the workpiece W can be measured by an instrument such as a goniometer, no special measuring equipment is required. Also, the offset can be adjusted without removing the tool U from the machine tool.

[0091] In the third disclosed numerical control device 100, since the load torque is used to adjust the offset amount, the offset can be corrected in a state where the workpiece W and the tool U are installed on the machine tool. Further, in the third disclosure, since the shape of the machining surface is a regular polygon, the adjustment is performed in a time-fixed manner, but in the case where the shape of the machining surface is other than a regular polygon, the adjustment time can also be changed in accordance with the shape of the machining surface.

[0092] As described above, one embodiment has been described, but the present invention is not limited to the above disclosure and can be implemented in various ways by making appropriate changes.

[0093] For example, in the above embodiment, the phase of the tool axis can also be adjusted to adjust the phase of the workpiece axis after correcting the offset amount of the tool T, thereby correcting the offset amount of the tool T.

[0094] In the above description, the case where the offset of the tool T is caused by the installation error has been described, but the numerical control device 100 of the present disclosure can also correct the offset caused by reasons other than the installation error, such as tool wear and bearing wear.

[0095] The step of calculating the adjustment amount γ based on the offset amount δ by the adjustment amount generation unit 14 is not limited to the above steps. If the reference tool T is selected or the ideal positions of the respective tools T are calculated in such a way that the adjustment amount γ is reduced, the phase of the tool T can be quickly matched, which is very efficient.

[0096] In addition, the correction of the offset in the rotational direction of the tool T and the radial correction can be combined.

[0097] The offset of the tool T usually occurs not only in the rotational direction but also in the radial direction. Therefore, it is preferable to combine both for correction.

[0098] In the correction of the radial offset, first, the radial offset is measured. The radial offset can be calculated based on the distances between two opposite sides of the workpiece W obtained as a result of trial machining. In addition, a laser displacement meter, a goniometer, an image measuring machine, etc. can also be used to directly measure the tool U to detect the offset amount δ.

[0099] The radial offset amount σ can be corrected by adjusting the axial distance between the workpiece axis and the tool axis.

[0100] That is, when the tool T is offset outward from the reference position, the axial distance between the workpiece axis and the tool axis is made closer to make the offset zero. Further, when the tool T is offset inward from the reference position, the axial distance between the workpiece axis and the tool axis is made farther to make the offset zero.

[0101] The offset δ in the rotational direction varies for each tool T. Therefore, if the offset δ i in the rotational direction of the tool T is set as δ i , then at the idling timing before cutting using the tool T i , the offset δ in the rotational direction and the offset σ in the radial direction are corrected simultaneously. i and the offset σ in the radial direction i .

[0102] As described above, if the correction in the rotational direction and the correction in the radial direction are performed simultaneously, the accuracy of polygon machining can be improved without replacing the tool T.

[0103] Description of the drawing characters

[0104] 100 Numerical control device

[0105] 200 Machine tool

[0106] 10 Polygon machining control section

[0107] 11 Workpiece axis command generation section

[0108] 12 Tool axis command generation section

[0109] 13 Phase offset acquisition section

[0110] 14 Adjustment amount generation section

[0111] 15 Adjustment amount superposition section

[0112] 16 Torque detection section

[0113] 111 CPU

[0114] 112 ROM

[0115] 113 RAM

[0116] 140 Servo amplifier

[0117] 150 Servo motor

[0118] 161 Spindle amplifier

[0119] 162 Spindle motor

[0120] 164 Spindle.

Claims

1. A control device controls polygon machining in which a workpiece and a tool rotate simultaneously to form a polygon on the surface of the workpiece, characterized in that, the control device includes: a workpiece axis command generation unit that generates a command for the angular velocity of the workpiece; a tool axis command generation unit that generates a command for the angular velocity of the tool; an offset acquisition unit that acquires information related to the offset of the rotational directions of a plurality of cutting tools mounted on the tool from each other; an adjustment amount generation unit that generates a pulse for adjusting the phase of either or both of the tool axis and the workpiece axis based on the information related to the offset of the rotational directions of the cutting tools acquired by the offset acquisition unit; and an adjustment amount superposition unit that superimposes the pulse on either or both of the command for the angular velocity of the workpiece and the command for the angular velocity of the tool.

2. The control device according to claim 1, characterized in that, the adjustment amount superposition unit superimposes the pulse during idling of the tool in the polygon machining.

3. The control device according to claim 1, characterized in that, the information related to the offset of the rotational directions of the cutting tools is the angle of the outer shape of the workpiece during trial machining.

4. The control device according to claim 1, characterized in that, the information related to the offset of the rotational directions of the cutting tools is the load applied to the tool when cutting the workpiece.

5. A control system controls polygon machining in which a workpiece and a tool rotate simultaneously to form a polygon on the surface of the workpiece, characterized in that, the control system includes: a workpiece axis command generation unit that generates a command for the angular velocity of the workpiece; a tool axis command generation unit that generates a command for the angular velocity of the tool; an offset acquisition unit that acquires information related to the offset of the rotational directions of a plurality of cutting tools mounted on the tool from each other; an adjustment amount generation unit that generates a pulse for adjusting the phase of either or both of the tool axis and the workpiece axis based on the information related to the offset of the rotational directions of the cutting tools acquired by the offset acquisition unit; and an adjustment amount superposition unit that superimposes the pulse on either or both of the command for the angular velocity of the workpiece and the command for the angular velocity of the tool.

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