Machine tool control devices and control systems

Abstract

A control device for polygon processing that controls a workpiece and a tool to rotate simultaneously to form a polygon on the surface of the workpiece obtains information related to the radial offset of a tool (T) mounted on a tool body, generates a pulse for correcting the radial offset of the tool (T), and outputs a pulse to an X-axis servo motor (152) to move the tool (U) in a direction opposite to the radial offset of the tool (T). Thus, the accuracy of polygon processing is improved by correcting the radial offset of the tool (T).

Description

Technical Field

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

[0002] In the past, there was polygonal machining in which a workpiece was machined into a polygonal shape by rotating a tool and a workpiece at a fixed ratio. In polygonal machining, the tool tip describes an elliptical orbit relative to the workpiece. If the rotation ratio between the workpiece and the tool and the number of tools are changed, the phase and number of the ellipse will change, and the workpiece can be machined into a polygon such as a quadrilateral or hexagon.

[0003] Fig. 7A This shows the movement path of the tool tip relative to the workpiece when the workpiece center is the origin. In this example, the rotation speed ratio between 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 track 1, and the movement path of tool T2 relative to the workpiece is track 2. During one rotation of the workpiece, the two tools T1 and T2 draw elliptical tracks around the workpiece, forming a quadrilateral on the workpiece surface. Figure 7B This is the movement path of the tool T when the rotation ratio is 1:2 and there are three tools. In this case, the three tools describe an elliptical orbit around the workpiece, and when the workpiece surface is cut along the orbit, a hexagon is formed.

[0004] The tool for polygon processing is called a polygon cutter, which is composed of a tool body and a cutter mounted on the tool body. Patent document 1 describes the following: the polygon processing tool is composed of a cutter body in an annular shape, three cutting blades, three fixing bolts for fixing the three blades respectively, and a positioning bolt for positioning and adjusting the blade tip of the blade.

[0005] In the processing tool (equivalent to a polygonal cutter) of the above-mentioned patent document 1, when a blade (equivalent to a tool) is arranged and fixed in a hollow hole of a cutter body, one of the cutting blades is installed to protrude from the outer peripheral surface of the tool body. When the cutting blade is fixed by a fixing bolt, the rotation of the blade in the hollow hole is prevented by the fastening force thereof.

[0006] In the processing tool of patent document 1, by making a structure in which a blade is installed on a cutter body, the tool diameter can be enlarged without increasing the tool mechanism, thereby improving the accuracy of polygon processing. In addition, by having a positioning bolt and a fixing bolt, the positioning adjustment function of the tool is improved.

[0007] Prior art literature

[0008] Patent Literature

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

[0010] Problems to be solved by the invention

[0011] The processing tool of Patent Document 1 is provided with a positioning bolt and a fixing bolt, which improves the positioning accuracy of the tool. However, the tool is installed manually, so sometimes there is some deviation in the installation position. In addition, in polygon processing, each tool repeatedly cuts and idles while rotating, but due to the load when the tool contacts the tool, sometimes there is a deviation in the installation position and the tool is deformed. The deviation in the installation position and the deformation of the tool will affect the accuracy of the processed shape.

[0012] like Fig. 7A as well as Figure 7B As shown in the figure, polygon processing is to make a polygon by combining ellipses, so the cutting surface becomes a gentle curve, which is not suitable for high-precision processing that requires high flatness. Compared with polygon processing using a milling machine, polygon processing takes a shorter processing time. Therefore, it is practically used for processing parts that will not cause problems even if high precision is not required (bolt heads, screwdriver drill bits, etc.).

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

[0014] In the field of polygon processing, technology for improving accuracy is desired.

[0015] Means for solving problems

[0016] One disclosure of the present invention is a control device that controls polygonal processing in which a workpiece and a tool are rotated simultaneously to form a polygon on the surface of the workpiece, and the control device comprises: a workpiece axis command generating unit that generates a command for the angular velocity of the workpiece; a tool axis command generating unit that generates a command for the angular velocity of the tool; an offset acquisition unit that acquires information related to the radial offset of a tool mounted on the tool; an adjustment amount generating unit that generates a pulse for adjusting the position of either or both of the tool axis and the workpiece axis based on the information related to the radial offset of the tool acquired by the offset acquisition unit; and an adjustment amount command unit that outputs a pulse to move the tool axis and the workpiece axis, or either the tool axis and the workpiece axis.

[0017] Another disclosure of the present invention is a control system that controls polygonal processing in which a workpiece and a tool are rotated simultaneously to form a polygon on the surface of the workpiece, and the control system comprises: a workpiece axis instruction generating unit that generates an instruction for the angular velocity of the workpiece; a tool axis instruction generating unit that generates an instruction for the angular velocity of the tool; an offset acquisition unit that acquires information related to the radial offset of the tool mounted on the tool; an adjustment amount generating unit that generates a pulse for adjusting the position of either or both of the tool axis and the workpiece axis based on the information related to the radial offset of the tool acquired by the offset acquisition unit; and an adjustment amount instruction unit that moves the workpiece axis and the tool axis, or either the workpiece axis and the tool axis, in accordance with the pulse.

[0018] Effects of the Invention

[0019] According to the present disclosure, it is possible to improve the accuracy of polygon processing. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0022] Figure 3A This is a diagram showing an example (ideal state) of a tool in which radial deviation does not occur.

[0023] Figure 3B This is a diagram showing an example of a tool in which radial deviation has occurred (a state in which deviation exists).

[0024] Figure 4A It is a diagram for explaining a method of correcting radial deviation.

[0025] Figure 4B It is a diagram for explaining a method of correcting radial deviation.

[0026] Figure 4C It is a diagram for explaining a method of correcting radial deviation.

[0027] Figure 5A It is a diagram showing the change of the trajectory of the tool in the present disclosure.

[0028] Figure 5B It is a diagram showing the change of the trajectory of the tool in the present disclosure.

[0029] Fig. 6A This is a diagram for explaining a method of calculating the radial deviation of a tool from a workpiece obtained as a result of trial machining.

[0030] Figure 6B This is a diagram for explaining a method of calculating the radial deviation of a tool from a workpiece obtained as a result of trial machining.

[0031] Fig. 7A This is a diagram for explaining conventional polygon processing.

[0032] Figure 7B This is a diagram for explaining conventional polygon processing. DETAILED DESCRIPTION

[0033] An example of a numerical controller 100 having a polygon processing adjustment function is shown below. Figure 1 As shown, the numerical controller 100 includes a CPU 111 for overall control of the numerical controller 100, a ROM 112 for recording programs and data, and a RAM 113 for temporarily expanding data. The CPU 111 reads the system program recorded in the ROM 112 via a bus 120 and controls the overall numerical controller 100 according to the system program.

[0034] The nonvolatile memory 114 is backed up by, for example, a battery (not shown), and maintains the stored state even when the power supply of the numerical controller 100 is turned off. The nonvolatile memory 114 stores programs read from the external device 72 via the interfaces 115, 118, and 119, user operations input via the input unit 30, and various data (e.g., setting parameters, sensor information, etc.) acquired from various components of the numerical controller 100, the machine tool 200, and the like.

[0035] The interface 115 is an interface for connecting the numerical controller 100 and an external device 72 such as an adapter. Programs, various parameters, etc. are read from the external device 72. In addition, programs, various parameters, etc. edited in the numerical controller 100 can be stored in an external storage unit via the external device 72. The PLC 116 (Programmable Logic Controller) performs control by inputting and outputting signals with the machine tool 200, the robot, and sensors installed in the machine tool 200 and the robot through the I / O unit 117 using the sequence program built into the numerical controller 100.

[0036] Display unit 70 displays an operation screen of machine tool 200 , a display screen showing the operating state of machine tool 200 , and the like. Input unit 30 is composed of an MDI, an operation panel, a touch panel, and the like, and transmits an operator's operation input to CPU 111 .

[0037] The servo amplifier 140 controls each axis of the machine tool 200. The servo amplifier 140 receives the axis movement instruction amount from the CPU 111 and drives the servo motor. The machine tool 200 includes at least a servo motor 151 for rotating the tool axis and a servo motor 152 for the X axis (or a servo motor for the Y axis). The servo motor 151 for rotating the tool axis and the servo motor 152 for the X axis (or the servo motor for the Y axis) have a built-in position speed detector, and the position speed feedback signal from the position speed detector is fed back to the servo amplifier 140 to perform feedback control of the position speed.

[0038] The numerical controller 100 sets a virtual coordinate system for the machine tool 200. In the following description, the central axis of the workpiece W is the Z axis, the axis connecting the workpiece center O and the tool center is the X axis, and the axis orthogonal to the X axis and the Z axis is the Y axis.

[0039] The machine tool 200 of the present disclosure includes at least a tool axis rotating servo motor 151 for rotating a tool U (tool axis) and an X-axis servo motor 152 for moving a tool post (hereinafter referred to as a tool U) in the X-axis direction.

[0040] The spindle amplifier 161 receives a spindle rotation command for a 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 rotation speed. The spindle 164 is coupled to a position encoder 163, and the position encoder 163 outputs a feedback pulse in synchronization with the rotation of the spindle 164, and the feedback pulse is read by the CPU 111.

[0041] A workpiece W is mounted 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 mounted on the tool axis cuts the workpiece surface and forms a polygon on the workpiece surface.

[0042] Figure 2 It is a block diagram of a control system 1000 having a polygon processing adjustment function.

[0043] The CPU 111 of the numerical controller 100 executes a program recorded in a storage device such as a ROM 112 to realize the functions in the block diagram.

[0044] The numerical control device 100 includes a polygon machining control unit 10. The polygon machining control unit 10 includes a workpiece axis command generating unit 11 that generates a rotation command for the workpiece axis, a tool axis command generating unit 12 that generates a rotation command for the tool axis, and a movement axis command generating unit 13 that generates a movement command for the tool U.

[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 for rotating the spindle 164 at a fixed angular velocity ω, and outputs the command 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. As a result, the workpiece W mounted 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 for rotating the tool U at a fixed angular velocity, and outputs the command to the servo amplifier 140. The servo amplifier 140 controls the tool axis rotation servo motor 151 according to the command from the tool axis command generation unit 12. The tool axis rotation servo motor 151 rotates the tool U at a fixed angular velocity according to the control of the servo amplifier 140. The angular velocity of the tool U is determined by the rotation ratio of the workpiece W to the tool U. In the example described later, the angular velocity of the tool U is 2ω.

[0047] The movement axis command generation unit 13 generates a movement command for the tool rest on which the tool U is placed. The movement command controls the movement of the tool U in the X-axis direction.

[0048] The command in the X-axis direction is the adjustment amount in the radial direction of the tool. The X-axis servo motor 152 adjusts the interaxial distance between the tool axis and the workpiece axis according to the command of the adjustment amount command unit 16 .

[0049] The position deviation acquisition unit 14 acquires information on the radial deviation of the tool T. The radial deviation amount σ of the tool T can be measured by a vernier caliper, an optical measuring instrument, an image measuring instrument, etc., but the measurement method is not specific. The measurement result is input to the position deviation acquisition unit 14 .

[0050] The adjustment amount generating unit 15 calculates the adjustment amount for each tool T i The radial offset σ i Adjustment amount μ i , generating and calculating the adjustment amount μ i The corresponding pulse.

[0051] The adjustment amount instruction unit 16 outputs pulses to the X-axis servo motor 152 during the idle timing. The pulses cause the tool axis to move in the X-axis direction. As a result, the interaxial distance between the workpiece axis and the tool axis can be adjusted. The pulses cause the tool (set to T) for the next cutting to move. i ) axis distance change adjustment amount μ i , to calibrate tool T i The adjustment of the distance between axes is performed during the idle timing of polygon machining. The idle timing refers to the time when the tool T of the tool U does not cut the workpiece W but idles, which does not affect the cutting.

[0052] [First disclosed offset adjustment method]

[0053] The first disclosed offset adjustment method is described. As a premise, the tool U for polygon processing is called a polygon cutter. The polygon cutter is composed of a cutter body and a cutter, and the cutter is installed on the cutter body for use. When the cutter is installed on the cutter body, radial installation errors may occur. The installation error affects the processing accuracy. In addition, there are also cases where the offset occurs due to wear of the cutter and the bearing. The offset caused by wear also affects the processing accuracy.

[0054] The following formula is a calculation formula for the adjustment amount μ. In the present disclosure, by using the following formula, the adjustment amount μ can be calculated regardless of the number N of tools T and the offset amount σ.

[0055] If the direction in which the tool T and the workpiece W are brought closer is positive, then for each tool T i The radial offset σ i Adjustment amount μ i for:

[0056] μ i =σ i-1 -σ i

[0057] (In the above formula, μ 1 =σ N -σ 1 In addition, the adjustment amount μ for the first cutting i -σ i ).

[0058] If the adjustment amount μ is calculated in this way i , and the position of the tool axis is adjusted by the initial cutting -σ i Adjustment, then tool T i The offset + σ i is canceled and becomes zero. i At the end of cutting, the tool axis position offset is -σ i If the position of the tool axis is σ i -σ i+1 Adjustment, the tool axis position deviation becomes -σ i+1 , tool T i+1 The offset +σ i+1 are canceled out and become zero.

[0059] In tool T i+1 At the end of cutting, the tool axis position offset is -σ i+1 If the position of the tool axis is σ i+1 -σi+2 Adjustment, the offset of the tool axis becomes -σ i+2 , tool T i+2 The offset +σ i+2 is canceled and becomes zero. Tool T i Rotation, adjustment amount μ i With cutting tool T i Correspondingly, it changes periodically.

[0060] As a specific example, refer to Figure 3A to Figure 4C , for 2 tools T 1 , T 2 Adjustment amount μ 1 , μ 2 The calculation method of is explained below. Figure 3A and Figure 3B This is an example of installing two knives at equal intervals. When installing two knives at equal intervals, it is ideal that Figure 3A As shown, the distance from the center Q of the tool U to the tip of the tool is r, but for some reason, such as Figure 3B As shown in Figure 1, radial offset (offset + σ) may occur. If the tool on the left side of the figure is set to T 1 , set the tool on the right side of the figure to T 2 , then tool T 1 , T 2 The radial offset (σ 1 , σ 2 )=(0,+σ).

[0061] In tool T 1 , T 2 The offset (σ 1 , σ 2 )=(0,+σ), according to the above formula, the adjustment amount (μ 1 , μ 2 )=(+σ, -σ: -σ only in the first cutting 1 . Reference Figure 4A to Figure 4C Specifically, in the first cutting, tool T 1 When cutting, tool T 1 The offset is 0, so no correction is performed ( Figure 4A ). In the second cut, tool T 2 When cutting, tool T 2 The radial offset is +σ, so when using tool T 2 The idle timing before cutting the workpiece W causes the tool U to move -σ in the X-axis direction and correct the offset to zero ( Figure 4B ). In the third cutting, tool U rotates 1 turn and tool T is used again. 1 Cutting is performed. Tool T1 The adjustment amount is +σ. Therefore, when using tool T 1 The idle timing before cutting the workpiece W moves the tool U in the X-axis direction by +σ, and the movement amount of the tool U returns to 0 ( Figure 4C ).

[0062] In this way, when the tool T 1 When cutting starts, the tool U is moved in the X-axis direction in the order of 0, -σ, +σ, -σ, . . . to correct the radial deviation.

[0063] The result of the correction is that the trajectory of tool T is as follows Figure 5A and Figure 5B Change like that.

[0064] Figure 5A The dotted line represents the tool path in ideal polygon processing. Figure 5A The dot-dashed line represents the trajectory of the tool when one of the tools is offset. When one of the tools is offset by +σ relative to the reference length r, the tool's cutting depth is longer than σ, so the tool T describes the trajectory of the tool relative to the workpiece W. Figure 5A The distance from the workpiece center O to the cutting surface is shortened by σ as shown by the single-dot chain line.

[0065] Figure 5B The solid line indicates the tool T 2 Tool T when the tool moves -σ during cutting 1 , T 2 The trajectory relative to the workpiece W. It can be seen that the trajectory of the corrected polygonal machining overlaps with the trajectory of the ideal polygonal machining and follows the same trajectory. In this way, by correcting the position of the tool U and correcting the radial offset of the tool T, the quadrilateral S formed by the polygonal machining becomes a roughly square.

[0066] [Second Publication]

[0067] [Method for measuring the offset σ]

[0068] In the second disclosure, the radial deviation amount σ is calculated using the workpiece W obtained as a result of trial machining. The deviation amount σ can be calculated by measuring the distance between the opposing surfaces of the workpiece W.

[0069] The measurement is performed by an operator, for example. Examples of measuring equipment include, but are not limited to, vernier calipers and image measuring instruments. The operator inputs the measured distance to the input unit 30. The position deviation acquisition unit 14 calculates the deviation amount σ.

[0070] Reference Fig. 6A as well as Figure 6B , the calculation method of the offset σ is explained. Fig. 6A] represents the shape of the workpiece W formed by the ideal tool U. The distance from the center W of the workpiece to the surface of the workpiece when cutting with the ideal tool U is denoted as l.

[0071] If the tool tip of tool U deviates by +σ, the cutting depth becomes deeper by +σ. Figure 6B As shown, the distance from the workpiece center O to the workpiece surface becomes shorter by +σ. At this time, the distance between the opposing surfaces of the workpiece is 2l-2σ. Since l is known, if the distance between the opposing surfaces of the workpiece is measured, the radial offset σ of the tool T can be calculated.

[0072] As an example, an example in which two tools T are used to form a quadrilateral has been described. However, by using the above method, the radial deviation amount σ of the tool T can be calculated from the workpiece W obtained as a result of trial machining regardless of the number of tools T.

[0073] As described above, the numerical controller 100 of the present disclosure generates a pulse corresponding to the radial deviation amount σ of the tool T and moves the tool U in the X-axis direction at the idle timing of the tool shaft, thereby being able to correct the radial deviation amount of the tool T without replacing the tool T.

[0074] In the numerical controller 100 of the second disclosure, the radial deviation amount σ of the tool T can be calculated by measuring the distance between the opposing surfaces of the workpiece W obtained as a result of trial machining. The distance between the opposing surfaces of the workpiece W can be measured using a vernier caliper or the like, so no special measuring equipment is required.

[0075] One embodiment has been described above, but the present invention is not limited to the above disclosure and can be implemented in various ways by adding appropriate changes. For example, in the present disclosure, the workpiece axis is set as the main axis and the tool axis is set as the servo axis, but it can also be set as the inter-spindle polygon processing in which both axes are main axes.

[0076] Furthermore, the inter-spindle distance may be adjusted by moving the workpiece axis in the X-axis direction instead of the tool axis.

[0077] Furthermore, correction of the deviation in the rotational direction of the tool T and correction in the radial direction may be combined.

[0078] The tool T generally deviates not only in the radial direction but also in the rotational direction. Therefore, it is preferable to perform correction by combining both.

[0079] In the correction of the offset in the rotation direction, first, the offset amount δ in the rotation direction is detected. The offset amount in the rotation direction can be calculated, for example, based on the angle of the workpiece obtained as a result of the trial processing. In addition, the offset can be detected using the load torque. In addition, the offset amount δ can also be detected using a direct measurement tool U such as a laser displacement meter, an angle meter, or an image measuring machine.

[0080] The offset δ can be corrected by accelerating or decelerating the tool axis. That is, when the tool T deviates from the reference phase in the positive direction, the tool axis is decelerated to make the offset zero. Alternatively, when the tool T deviates from the reference phase in the negative direction, the tool axis is accelerated to make the offset zero.

[0081] Since the offset amount δ in the rotation direction is different for each tool T, if the offset amount in the rotation direction of the tool Ti is δi, the offset amount δi in the rotation direction and the offset amount σi in the radial direction are corrected simultaneously at the idle timing before cutting by the tool Ti.

[0082] If the correction in the rotational direction and the radial direction are performed simultaneously, the accuracy of polygon processing can be improved without changing the tool.

[0083] Description of Reference Numerals

[0084] 1000 Control Systems

[0085] 100 Numerical control device

[0086] 200 Machine Tools

[0087] 10 Polygon processing control unit

[0088] 11 Workpiece axis command generation unit

[0089] 13 Moving axis command generation unit

[0090] 14 Position offset acquisition unit

[0091] 15 Adjustment amount generation unit

[0092] 16 Adjustment amount command unit

[0093] 17 Torque detection unit

[0094] 111 CPU

[0095] 112 ROM

[0096] 113 RAM

[0097] 140 Servo amplifier

[0098] 151 Servo motor for tool axis rotation

[0099] 152 X-axis servo motor

[0100] 161 Spindle amplifier

[0101] 162 Spindle motor

[0102] 164 Spindle.

Claims

1. A control device for controlling polygonal machining in which a workpiece and a tool are rotated simultaneously to form a polygon on the surface of the workpiece, It is characterized in that The control device comprises: a workpiece axis instruction generating unit, which generates an angular velocity instruction of the workpiece; a tool axis command generating unit, which generates a command for an angular velocity of the tool; an offset acquisition unit that acquires information related to a radial offset of a tool mounted on the tool; an adjustment amount generating unit for generating a pulse for adjusting the position of one or both of the tool axis and the workpiece axis based on the information on the radial offset of the tool input to the offset acquiring unit; as well as an adjustment amount instruction unit that outputs the pulse when the tool is idling during the polygon machining, The information on the radial deviation of the tool is the distance between the opposing surfaces of the workpiece when the trial machining is performed.

2. The control device according to claim 1, It is characterized in that The adjustment amount generating unit adjusts the interaxial distance between the workpiece axis and the tool axis.

3. A control system for controlling polygonal machining in which a workpiece and a tool are rotated simultaneously to form a polygon on the surface of the workpiece. It is characterized in that The control system comprises: a workpiece axis instruction generating unit, which generates an angular velocity instruction of the workpiece; a tool axis command generating unit, which generates a command for an angular velocity of the tool; an offset acquisition unit that acquires information related to a radial offset of a tool mounted on the tool; an adjustment amount generating unit that generates a pulse for adjusting the movement of one or both of the tool axis and the workpiece axis based on the information on the radial deviation of the tool acquired by the deviation acquiring unit; as well as an adjustment amount command unit that outputs the pulse to move the workpiece axis and the tool axis, or one of the workpiece axis and the tool axis, when the tool is idling during the polygon machining. The information on the radial deviation of the tool is the distance between the opposing surfaces of the workpiece when the trial machining is performed.

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