Grinding equipment

Abstract

To provide a technique for realizing a function for mitigating excessive cutting when changing override commands, in a grinding device and a control method thereof.SOLUTION: When operating an override switch, a function is prepared for automatically conducting an operation in which a grindstone rotary device is fed once in a radial direction at a linear axis in a direction of distancing from a grinding object in applying override so as to gradually return to original coordinates, thus the switch shall not be applied as it is to a control device. In addition, a mechanism is comprised for automatically determining whether an exterior side is ground or an interior side is ground in order to move the grindstone rotary device, by combining operation of a previous automatic cutting device and a type of command in a rotational direction of circular interpolation.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a grinding device (and its control method), and in particular to a grinding device that can feed or fix a grinding wheel rotating device with a grinding wheel attached, such as a jig grinder, in the radial direction using a linear axis called a cutting device, and can grind the inner or outer surface of a circle by rotating both devices using a separate rotating device, and further relates to a grinding device (and its control method) that can simultaneously control the coordinate space of the XYZ three axes together with this separate rotating device using a feeding device. [Background technology]

[0002] Grinding of a workpiece (hereafter referred to as "workpiece") by a jig grinder is achieved, for example, in a so-called single-column machine, by moving the workpiece placed on a table back and forth (Y-axis direction) and left and right (X-axis direction) on a slide while moving a so-called quill, which has a grinding wheel and a high-frequency motor for rotating it attached to its bottom end, up and down (Z-axis direction). In the case of a so-called double-column (gantry) jig grinder, the workpiece is moved only in the X-axis direction, while the grinding wheel (main spindle body) moves in the Y-axis direction. Needless to say, the names of the axes, such as X-axis, Y-axis, and Z-axis, can be interchanged depending on the machine manufacturer.

[0003] More specifically, there are two main types of grinding: One is a grinding method in which the rotation axis of the grinding wheel (grinding wheel shaft) is made eccentric (cutting) relative to the spindle, so that the grinding wheel rotates about the grinding wheel shaft while the spindle continues to rotate, i.e., the grinding wheel rotates in a planetary fashion, and at the same time, the quill is moved up and down to rotate the grinding wheel in a spiral, thereby boring a perfectly round hole by evenly grinding the inner wall. In this case, the hole diameter is basically determined according to the size of the outer diameter of the grinding wheel and the degree of eccentricity of the grinding wheel spindle (cutting depth (for example, maximum 50 mm)). The other is grinding to process non-circular holes with an inconstant curvature or edges with an inconstant curvature. In this case, so-called chopping is performed. In detail, the grinding wheel spindle is not eccentric, or the grinding wheel is eccentric in the opposite direction (negative direction) to the above-mentioned cutting depth by an amount equivalent to the radius of the grinding wheel so that the spindle rotation center and the outer periphery of the grinding wheel coincide, and first the workpiece is moved to the processing position (grinding point) by X and Y axis feed. Then the net cutting depth is added. The grinding wheel is automatically eccentric by the amount of work, i.e., chopping is performed while automatically cutting. When the grinding wheel cuts into the work surface of a workpiece with an inconsistent curvature, the angle of the spindle is controlled (indexed) so that the normal at the cutting point where the workpiece contacts always coincides with the cutting direction of the grinding wheel. Patent Document 1 discloses the main configuration of such a jig grinding machine. However, Patent Document 1 omits the configuration for raising and lowering the grinding wheel. Here, chopping refers to linear reciprocating motion, and there is no definition that sets any restrictions on the reciprocating speed used in general chopping, whether slow or fast. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-102891 Summary of the Invention [Problem to be solved by the invention]

[0005] In the jig grinding machine described above, depending on the selection of CNC functions and the design of the control software, for example, the grinding wheel may approach the surface beyond the range immediately after the override switch is activated or the settings of the oscillation range, speed, or center position are changed. Therefore, there is a need for software or a mechanical device that prevents the grinding wheel from colliding with the surface beyond the range of reciprocation by momentarily superimposing a command to separate the end of the grinding wheel's reciprocation range from the surface beyond the grinding surface when the settings of the oscillation range, speed, or center position, including the override switch, are changed during chopping and oscillation grinding, and then the override switch or the aforementioned setting change is applied, gradually returning the grinding wheel to its normal position over the number of reciprocations. The inventors have filed patent applications for grinding devices and control methods that meet this need (Patent Application Nos. 2018-160030 and 2019-107534).

[0006] The above-mentioned feeding device can perform circular interpolation on two axes, for example, in the (XY) plane, while using another rotating device to orient the cutting device in the normal direction, outward or inward, making it possible to process a size that exceeds the feed range of the cutting device.In addition, many devices allow the operator to freely change the speed of circular interpolation by using an override switch. However, changing the speed of circular interpolation can cause deviations depending on the order of the servo system and whether or not feedforward control is used, and can also cause overcutting due to centrifugal force, etc. Also, there is a risk of feeling overcutting immediately after operating the override switch, especially when there is a sudden change. Here, for example, the radius reduction ΔR in a typical servo control system for a machine tool, even if only using the servo, can be approximated as shown in the following formula (2) if the response of the velocity loop and current loop is sufficiently fast and linear acceleration / deceleration after interpolation is used.

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[0007] An object of the present invention is to provide a technology for realizing a function for mitigating overcutting when an override command is changed in a grinding machine and a control method thereof. [Means for solving the problem]

[0008] The inventor has studied the configuration of a grinding machine and its control method that realizes a function to mitigate overcutting when an override command is changed, and has found that when the override switch is operated, the grinding wheel rotation device is temporarily moved away from the grinding object by the infeed device, rather than being directly applied to the control device. Move Alternatively, instead of directly applying the override switch to the control device when the override switch is operated, the grinding wheel rotating device is first rotated in the radial direction on a linear axis in a direction away from the grinding object. Move Apply the override 、 We came up with the idea of ​​providing a function that automatically performs the operation of gradually returning the coordinates to their original positions.

[0009] Furthermore, it has been found that it is preferable to change the relief direction when grinding the outside and when grinding the inside.

[0010] Furthermore, a mechanism may be provided that automatically determines whether grinding is being performed on the outside or inside in order to operate the aforementioned device by combining the operation of the automatic cutting device immediately before and the type of command for the rotation direction of the circular interpolation.

[0011] In addition, in the release step, the operation history of the automatic cutting device is traced back. move It is preferable to [Effects of the Invention]

[0012] According to the present invention, in a grinding machine and a control method thereof, it is possible to realize a function for mitigating excessive cutting when an override command is changed. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a perspective view showing a jig grinding machine as an example of a grinding device to which the present invention is applied; [Figure 2]2 is a diagram for explaining the grinding device (jig grinding machine) shown in FIG. 1 together with the direction of movement or rotation of each axis. FIG. [Figure 3] FIG. 2 is an enlarged view of the U-axis feed device and the grinding wheel spindle area in the grinding machine (jig grinding machine) shown in FIG. [Figure 4] 2 is a diagram showing the relationship between the machining of a workpiece by a rotating grindstone in the grinding device (jig grinder) shown in FIG. 1 and the axial movements of the U axis and the Z axis. FIG. [Figure 5] 2 is a block diagram showing an outline of a control system of the grinding device (jig grinder) shown in FIG. 1. FIG. [Figure 6] 4 is a graph showing the relationship between an override command, an actual rotation speed, and an automatic cutting position in the grinding machine and the control method thereof according to the first embodiment of the present invention. [Figure 7] 4 is a flowchart of a control process from the start to the end of a machining process in the grinding device according to the first embodiment of the present invention. [Figure 8] 2 is a functional block diagram showing an outline of a control system for circular interpolation of the grinding device (jig grinding machine) shown in FIG. 1. FIG. [Figure 9] FIG. 1 is a functional block diagram showing an outline of a control system for general circular interpolation. DETAILED DESCRIPTION OF THE INVENTION

[0014] First, to facilitate understanding of the present invention, a grinding machine to which the present invention is applicable will be described with reference to the drawings. FIG. 1 is a perspective view showing an example of a grinding machine to which the present invention is applicable. FIG. 2 is a diagram illustrating the grinding machine along with the movement or rotation direction of each axis. The U-axis feeder can move linearly along the Z-axis and rotate around the Z-axis (referred to as the C-axis) relative to the head. The U-axis feeder can move the grinding wheel spindle linearly along the U-axis. Each axis may be a combination of multiple parallel axes. FIG. 3 is an enlarged view of the U-axis feeder and the grinding wheel spindle in the grinding machine (jig grinder). FIG. 4 is a diagram illustrating the relationship between the machining of a workpiece by a rotating grinding wheel in the grinding machine (jig grinder) and the movement of the U-axis and Z-axis. As shown in FIG. 1, a grinding machine (jig grinder) 10 to which the present invention is applicable has a table feeder 36 and a table 30 supported on a bed 12 via rails 16 for movement in the Y-axis direction (front-back direction). The column 14 is fixed to the bed 12, but relative motion can be imparted between the column 14 and the feed device 36 in a direction along the rail 16. A motor for moving the feed device 36 (not shown) is disposed at the rear of the bed 12, and this motor moves the table feed device 36 back and forth along the rail 16 via a ball screw (not shown) or other means. A head 18 is supported on the column 14 so as to be movable (liftable) in the W-axis direction. A grinding wheel spindle 20 is provided at the tip of the head 18, and a grinding wheel 100 (see FIG. 3) is attached to the tip of the grinding wheel spindle 20. A head lift motor (not shown) is disposed above the column 14, and this motor lifts and lowers the head 18 via a ball screw (not shown) or other means. A grinding wheel spindle rotation motor (motor C of 302 in FIG. 5) is disposed inside or at the rear of the head 18, and this motor rotates the grinding wheel spindle 20. An encoder (not shown) constituting a measuring means is attached to the head lift motor. The other linear and rotary axes, excluding the grinding wheel spindle, are equipped with encoders and motors (not shown) so that the feed amount or rotation amount can be calculated and controlled. The data output from these encoders is used to calculate the lift amount of the head 18 and the cutting depth into the workpiece (see Figure 4), which will be described later.The Z-axis is provided parallel to the W-axis direction, and Z-axis movement can be imparted without interfering with the W-axis head movement, C-axis rotation, and U-axis linear movement.

[0015] As described above, the Y-axis feed device 36 is mounted on the bed 12 via rails 16. The Y-axis feed device 36 is configured to be able to move linearly back and forth in the Y-axis direction along the direction of the rails 16. The table 30 is supported on the Y-axis feed device 36 via rails (not shown). The table 30 is configured to be able to move linearly left and right (in the X-axis direction) relative to the Y-axis feed device 36. A workpiece (not shown) is removably mounted and fixed on its upper surface. Naturally, a motor for moving the Y-axis feed device 36 is provided on the bed 12, and the motor moves the Y-axis feed device 36 along the rails 16 via a ball screw (not shown) or other device. The table 30 also moves on the Y-axis feed device 36 via a motor, ball screw, or other device (not shown). Then, while the grinding wheel spindle 20 is rotated by the grinding wheel spindle rotation motor, the head 18 (grinding wheel spindle 20) is lowered by the head elevation motor, so that the grinding wheel 100 attached to the tip of the grinding wheel spindle 20 comes into contact with the surface of the workpiece on the table 30. The table 30 can be freely moved in the X and Y directions by the two motors mentioned above, thereby grinding the surface of the workpiece with the grinding wheel 100. The grinding device 10 is equipped with various operation switches or similar input devices, and is configured so that the state can be changed by an operator during operation. The grinding device 10 is also equipped with an AE (acoustic emission) sensor (not shown) on the workpiece side as a means for detecting contact between the grinding wheel 100 and the workpiece. When the AE sensor detects contact between the workpiece and the grinding wheel 100, it displays this to the operator or sends a skip signal to stop feeding the grinding wheel 100.

[0016] As described above, the machine tool (grinding machine) 10 shown in FIG. 1 is a CNC-controlled machine tool (grinding machine) capable of simultaneous control of at least three axes: X, Y, and Z. It also has a drive axis (rotational axis [C-axis] or linear drive axis) whose axial direction is parallel to the rotational axis, i.e., the grinding wheel spindle 20. Specifically, the machine tool (grinding machine) 10 has a U-axis feed device 40 below the head 18. This U-axis feed device 40 is a linear feed mechanism including the grinding wheel spindle 20 and the disk 27 mounted thereon. It moves the grinding wheel spindle 20 and the disk 27 mounted thereon linearly within a predetermined stroke range depending on the angular position of the C-axis at that time. The direction of this linear movement is defined as the U-axis (direction). In other words, in the machine tool (grinding machine) 10 shown in FIG. 1, the head 18 can move linearly (up and down) in the Z-axis direction. This is referred to as the W-axis feed device to distinguish it from the Z-axis. Furthermore, the U-axis feed device 40 can be rotated relative to the head 18 in a linear motion along the Z-axis and around the Z-axis (referred to as the C-axis). The U-axis feed device 40 can linearly move the grinding wheel spindle 20 in the U-axis direction. To explain the drive axis control of the machine tool (grinding device) 10 more specifically with reference to Figures 2 and 3, in the machine tool (grinding device) 10, the U-axis linear feed mechanism is mounted on the rotating side of the C-axis. A feed command for the grinding wheel spindle (U-axis) can linearly move the U-axis feed device 40 along the U-axis. A rotation command for the C-axis rotates the entire center of the grinding wheel spindle 20. Furthermore, this C-axis device can be linearly moved vertically by the Z-axis device.

[0017] Figure 5 is a block diagram showing an outline of the control system of the jig grinding machine shown in Figure 1. The jig grinding machine according to the present invention has, as its control system, a control device 300, an input / output device 310, axis motors 320 and their respective motor drivers 330, a grinding wheel rotation motor 102A, and a grinding wheel motor inverter 102inv. The control device 300 has a computer numerical control (CNC) 302, a programmable controller 304, and an I / O (input / output) module 306. The control system of the jig grinding machine according to the present invention also has, as input / output device 310, a keyboard, various switches, a temperature sensor, etc., as well as a tool setter related to skip signals, an AE sensor, etc.

[0018] Here, we will explain the problems of the conventional example again. In the grinding machine (jig grinder) 10 shown in Figures 1 to 5, the feed device described above performs circular interpolation on two axes, for example, in the (XY) plane, while using another rotation device (C-axis rotation device) to orient the automatic infeed device 104 (corresponding to the U-axis feed device 40; the same applies below) in the normal direction, outward, or inward, thereby enabling machining of sizes beyond the feed range of the automatic infeed device 104. Furthermore, many circular interpolation speeds are freely adjustable by the operator using an override switch. However, changing the circular interpolation speed can result in deviations depending on the order of the servo system and the presence or absence of feedforward control, and can also result in overcutting due to centrifugal force, etc. Furthermore, there is a possibility that overcutting may be felt immediately after operating the override switch, especially when the speed changes suddenly.

[0019] Therefore, in the grinding machine and its control method according to an embodiment of the present invention, rather than directly applying the override switch to the control device 300 (see FIG. 5), the grinding wheel rotation device 102 is temporarily fed away from the grinding target by the automatic infeed device 104, thereby applying an override. Alternatively, rather than directly applying the override switch to the control device 300 (see FIG. 5), a function is provided to automatically feed the grinding wheel rotation device 102 along the linear axis (U-axis) in the radial direction away from the grinding target, thereby applying an override and gradually returning the grinding target to its original coordinate system. Furthermore, it is preferable to be able to change the escape direction when grinding the outside and the inside. Furthermore, a mechanism may be provided to automatically determine whether grinding is being performed on the outside or the inside of the grinding machine, based on the immediately preceding operation of the automatic infeed device 104 and the type of command for the rotation direction of the circular interpolation. In the release, it is preferable to send the operation history of the automatic cutting device 104 in the retroactive direction.

[0020] That is, the grinding apparatus 10 according to the embodiment of the present invention has an automatic infeed device 104 that can feed or fix a grinding wheel rotation device 102 having a grinding wheel 100 attached thereto in the radial direction using a linear axis (U-axis), and further, the entire device including the grinding wheel rotation device 102 and the automatic infeed device 104 can be rotated by a rotation device (C-axis rotation device) 106, and is a grinding apparatus that can grind the inner or outer surface of a circle (cylindrical if the thickness is taken into consideration) to be ground by circular interpolation using synchronous control of two or more axes, and is configured so that the direction in which the automatic infeed device 104 feeds the grinding wheel rotation device 102 in a straight line can be aligned with the normal direction of the arc using the rotation device (C-axis rotation device) 106 during the grinding process, and is configured so that the operator can freely change the feed rate of the circular interpolation using an override switch, and when this override switch is operated, an override command is not immediately applied to the control device 300, but is temporarily changed. The grinding wheel rotating device 102 is fed in a direction away from the object to be ground by the automatic cutting device 104, and then an override is applied.

[0021] Also, in a grinding machine having an automatic infeed device 104 that can feed or fix a grindstone rotating device 102 with a grindstone 100 attached in the radial direction using a linear axis (U-axis), and further capable of rotating the entire device including the grindstone rotating device 102 and the automatic infeed device 104 using a rotating device (C-axis rotating device) 106, the grinding machine can grind the inner or outer surface of a circle by circular interpolation using synchronous control of two or more axes, and is configured so that the direction in which the automatic infeed device 104 feeds the grindstone rotating device 102 in a straight line can be aligned with the normal direction of the arc using the rotating device (C-axis rotating device) 106 during this grinding process, and is configured so that the operator can freely change the feed rate of the circular interpolation using an override switch, when this override switch is operated, an override command is not immediately applied to the control device 300, but A feature of this system is that it has a function that automatically performs the operation of using the automatic cutting device 104 to feed the grinding wheel rotation device 102 in the radial direction on a linear axis in a direction away from the grinding object, applying an override, and gradually returning it to the original coordinates (target coordinates for CNC control) over time.

[0022] In the grinding device 10, the direction of the relief may be changed when grinding the outside of the grinding object (when machining the outer peripheral surface, etc.) and when grinding the inside (when machining the inner peripheral surface, etc.). Furthermore, the grinding device 10 may be further provided with a mechanism for automatically determining whether the outside or inside is being ground by combining the immediately preceding operation of the automatic cutting device 104 and the type of command for the rotation direction of the circular interpolation. Furthermore, in the grinding device 10, the operation history of the automatic cutting device 104 may be sent in a retroactive direction during relief.

[0023] Fig. 6 is a graph showing the relationship between (a) an override command, (b) an automatic cutting position, and (c) an actual rotation speed in a grinding machine and a control method thereof according to an embodiment of the present invention. In the grinding machine and a control method thereof according to an embodiment of the present invention, as shown in Fig. 6(a), when the override switch is operated, the automatic cutting position by the automatic cutting device 104 is temporarily moved in the radial direction away from the workpiece to be ground, as indicated by the dashed line in Fig. 6(b), rather than being immediately applied (to the control device 300 (see Fig. 5)), and then gradually returned to the original (coordinate) command position. As a result, the actual rotation speed also catches up with a corresponding delay, as shown in Fig. 6(c).

[0024] 7 is a flowchart of the control process from start to finish of the machining process in the grinding machine of this embodiment. Specifically, the grinding machine of this embodiment starts the machining process (S701), checks whether an override switch is operated during machining, or whether an override change will occur (S702), and determines whether a speed change will occur (S703). If a speed change will occur (YES in S703), calculates an additional clearance amount for the clearance amount remaining at that time (S704), determines the clearance direction (S705), executes the clearance addition operation (S706), and changes the speed (S707). Cutting is performed at this changed speed, and determines whether the C-axis rotation has ended (S708). If the C-axis rotation has ended (YES in S708), the machining process ends (S709). On the other hand, if the C-axis rotation has not ended (NO in S708), the process returns to S702. If it is determined in S703 that there is no change in speed (NO in S703), a release damping operation is performed (S710), and the process returns to S708.

[0025] FIG. 8(a) shows the main flow of the control process from start to finish of the machining process shown in FIG. 7 . FIG. 8(b) shows the control process flow for automatically determining whether grinding is performed on the outside or inside by taking into account the immediately preceding operation of the automatic cutting device 104 and the type of command for the rotation direction of the circular interpolation. FIG. 8(c) shows the control process for forwarding the operation history of the automatic cutting device 104 in the backward direction for the escape. The main flow of FIG. 8(a) has been described with reference to FIG. 7. In the grinding device of this embodiment, in order to determine the escape direction in S705 of FIG. 7, an automatic cutting record is further created as shown in FIG. 8(b). That is, when an automatic cutting command is initiated (S801), the cutting direction is recorded (S803) each time an automatic cutting direction command is generated (S802). The escape direction in S705 of FIG. 7 is determined by referring to this cutting direction record (history). Then, once the automatic cutting operation is executed (S804), the automatic cutting command ends (S805). To determine the escape direction, the NC modal information is also referenced, as shown in Figure 8(c). That is, in S806, the mode information, such as the direction of the arc / straight line / normal line (right / left of the path?), is referenced. The escape direction is primarily determined by the direction of return from the last automatic cutting operation. If the previous operation was a move to the start position, the correction amount is treated as 0. If the direction is unknown due to the progress of the process, the normal direction control and circular interpolation modes are checked, and the pre-settings for each machining operation are used. For example, G41.1 and G02 = U-negative direction, G42.1 and G02 = U-positive direction, G41.1 and G03 = U-positive direction, and G42.1 and G03 = U-negative direction.

[0026] The amount of overcut (change in radius Δr) according to the change in rotation speed is generally defined by the following formula (1).

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[0027] In a typical servo control system for machine tools, the decrease in radius ΔR during constant speed rotation with a circular arc command can be approximated by the following formula (2) if the response of the speed control section and current control section is sufficiently fast and the acceleration / deceleration after interpolation is also sufficiently fast.

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[0028] Generally, a control system for circular interpolation as shown in FIG. 9 is used. [Explanation of symbols]

[0029] 10 Jig grinding machine (grinding device), 100 Grinding wheel, 102 Grinding wheel rotating device, 104 Automatic cutting device, 106 Another rotating device (C-axis rotating device), 300 Control device, W Workpiece,

Claims

1. a grinding machine comprising a grinding wheel rotating device that rotates a grinding wheel spindle equipped with a grinding wheel; an automatic infeed device that can move and stop the grinding wheel rotating device in a radial direction about a linear axis; and a separate rotating device having a rotation axis parallel to the grinding wheel spindle, wherein the grinding machine can grind the inner or outer surface of a circle by circular interpolation using synchronous control of two or more axes, and wherein the separate rotating device is configured so that the direction in which the automatic infeed device moves the grinding wheel rotating device in the radial direction is aligned with the normal direction of the arc during grinding, and the grinding machine is configured so that an operator can freely change the feed rate of the circular interpolation with an override switch, characterized in that when the override switch is operated, rather than immediately applying an override command to a control device, the automatic infeed device first moves the grinding wheel rotating device in a direction away from the object to be ground, and then the override is applied.

2. a grinding machine comprising a grinding wheel rotation device that rotates a grinding wheel spindle equipped with a grinding wheel; an automatic infeed device that can move and stop the grinding wheel rotation device in a radial direction about a linear axis; and a separate rotation device having a rotation axis parallel to the grinding wheel spindle, wherein the grinding machine can grind the inner or outer surface of a circle by circular interpolation using synchronous control of two or more axes, and wherein the separate rotation device is used to align the direction in which the automatic infeed device moves the grinding wheel rotation device in the radial direction with the normal direction of the arc during grinding, and wherein the grinding machine is configured so that an operator can freely change the feed rate of the circular interpolation with an override switch, characterized in that when the override switch is operated, the grinding machine has a function of automatically performing an operation of first using the automatic infeed device to move the grinding wheel rotation device in a direction away from the object to be ground, then applying an override, and gradually returning it to its original coordinates over time, rather than immediately applying an override command to a control device.

3. 3. The grinding device according to claim 1, further comprising a structure capable of changing the direction of release when grinding the outside and when grinding the inside.

4. 4. The grinding device according to claim 1, further comprising a mechanism for automatically determining whether the outside or inside of the workpiece is being ground by combining the immediately preceding operation of the automatic cutting device and the type of command for the rotation direction of the circular interpolation.

5. 5. The grinding device according to claim 1, wherein the automatic cutting device is moved in a direction tracing back the operation history during the release.

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