Grinding device and control method thereof

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: A control method of a grinding device includes the steps of: determining whether or not a change in speed occurs when an override change takes place during processing; calculating a release addition amount and executing a release addition operation when a change in speed occurs; changing the speed and implementing cutting at the changed speed. If there is no change in speed, a release attenuation operation is executed.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a grinding machine and a control method thereof, and more particularly to a grinding machine and a control method thereof that can grind the inner or outer surface of a circle by rotating a grinding wheel rotating device with a grinding wheel attached, such as a jig grinding machine, in a radial direction using a linear axis or by fixing the device, and further by rotating the device itself using a separate rotating 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 (amount of cutting (for example, up to 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 made eccentric, or the grinding wheel is made eccentric in the opposite direction (negative direction) to the cutting by an amount equivalent to the radius of the grinding wheel so that the center of rotation of the spindle 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 workpiece is automatically moved by the amount of net cutting. In this method, the grinding wheel is eccentrically moved, i.e., chopping is performed while automatically cutting. When the grinding wheel cuts into the workpiece surface 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 moving the grinding wheel up and down. Here, chopping refers to linear reciprocating motion, and the term chopping is not defined with 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 operating the override switch or changing the settings of the oscillation range, speed, or center position. 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 superimposing a command that momentarily separates the end of the grinding wheel's reciprocation range from the surface beyond the grinding surface when changing the settings of the oscillation range, speed, or center position, including the override switch, during chopping and oscillation grinding. 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 jig grinding machine described above has an automatic infeed device that can feed or fix the grinding wheel rotating device with a grinding wheel attached in the radial direction using a linear axis, and by rotating each of these devices using a separate rotating device (a device equivalent to the main shaft described above), it is possible to grind the inner or outer surface of a circle.In addition, there are some machines where the rotation speed of the device equivalent to the separate rotating device can be freely changed by the operator using an override switch to multiply the rotation speed by the command rotation speed. However, changing the rotation speed of a device that corresponds to another rotating device can cause overcutting due to centrifugal force, etc., and when a particularly sudden change occurs due to an override switch, etc., the overcutting is often felt. Therefore, the development of a jig grinder with a function to mitigate overcutting when such an override command is changed is desired, but there have been few effective proposals to solve this problem.

[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 inventors have conducted extensive research into the configuration of a grinding machine and a control method thereof that realizes an overcut mitigation function when an override command is changed. As a result, they have conceived that such a mitigation function can be realized by first feeding the grinding wheel rotation device along its linear axis in the radial direction away from the workpiece to apply the override, rather than directly applying the override to the control device when the override switch is operated. Alternatively, they have conceived that a similar mitigation function can be realized by providing a function that automatically performs the operation of first feeding the grinding wheel rotation device along its linear axis in the radial direction away from the workpiece to apply the override and gradually returning it to the original coordinate, rather than directly applying the override to the control device when the override switch is operated. Furthermore, they have found that it would be preferable to be able to change the relief direction when grinding the outer surface and the inner surface.

[0009] That is, according to a first aspect of the present invention, A grinding machine having an automatic infeed device that can feed or fix a grinding wheel rotating device with a grinding wheel attached in the radial direction on a linear axis, and further capable of grinding the inner or outer surface of a circle by rotating the entire automatic infeed device including the grinding wheel rotating device with a separate rotating device, wherein the grinding machine is configured so that an operator can freely change the rotation speed of the separate rotating device with an override switch, and wherein when the override switch is operated, the operation is not immediately applied to a control device, but the automatic infeed device is first operated to feed the grinding wheel rotating device in the radial direction on a linear axis in a direction away from the object to be ground, and then the rotation speed override of the separate rotating device is applied, characterized in that the escape direction is changed when grinding the outer surface and when grinding the inner surface. is obtained.

[0010] According to a second aspect of the present invention, A grinding machine having an automatic infeed device that can feed or fix a grinding wheel rotating device with a grinding wheel attached in the radial direction on a linear axis, and further capable of grinding the inner or outer surface of a circle by rotating the entire automatic infeed device including the grinding wheel rotating device on a separate rotating device, wherein the grinding machine is configured so that an operator can freely change the rotation speed of the separate rotating device with an override switch, and wherein when the override switch is operated, the operation is not immediately applied to a control device, but rather the automatic infeed device is first operated to feed the grinding wheel rotating device in the radial direction on a linear axis in a direction away from the object to be ground, and then an override is applied to gradually return it to the original coordinates over time, and wherein the grinding machine is characterized in that the escape direction is changed when grinding the outside and when grinding the inside. is obtained.

[0011] Furthermore, according to the present invention, there is provided a grinding apparatus that has an automatic cutting device that can feed or fix a grinding wheel rotating device with a grinding wheel attached in the radial direction using a linear axis, and that can grind the inner or outer surface of a circle by rotating the entire device including the grinding wheel rotating device and the automatic cutting device using a separate rotating device, and that is configured so that an operator can freely change the rotation speed of the separate rotating device using an override switch, and that has a first step of determining whether a speed change will occur if an override change occurs during processing, a second step of calculating an amount of escape addition and performing an escape addition operation if a speed change occurs, and a third step of changing the speed and performing cutting at this changed speed, and a control method for a grinding apparatus characterized in that the first to third steps are performed in this order. 。 [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. 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 direction of movement or rotation of each axis. The U-axis feeder can move the grinding wheel shaft 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 shaft 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 shaft area 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 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 or linear drive axis) whose axial direction is parallel to the rotational axis, called 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, and 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 center of the grinding wheel spindle. 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. The jig grinder 10 shown in Figures 1 to 5, as clearly shown in Figure 3 in particular, is a grinding machine that can grind the inner or outer surface of a circle (cylindrical in consideration of thickness) to be ground by rotating a grinding wheel rotation device 102 (which of course includes a grinding wheel rotation motor 102A, a grinding wheel motor inverter 102inv [see Figure 5], etc., but only the portion of the grinding wheel rotation device that can be inserted into the machining chamber) with a grinding wheel 100 attached, using a separate rotation device (C-axis rotation device) 106 (which of course includes a C-motor for C-axis rotation, a C-axis motor drive [see Figure 5], etc.) to freely change the rotation speed of the separate rotation device (C-axis rotation device) 106 by using an override switch to freely change the magnification of the rotation speed relative to the command rotation speed. However, if the rotation speed of the device equivalent to the other rotating device (C-axis rotating device) 106 is changed, there is a possibility that excessive cutting may occur due to centrifugal force, etc., due to its mass. In particular, there is a risk that excessive cutting may be felt when there is a sudden change, such as when an override command is changed.

[0019] Therefore, in the grinding device and its control method according to the embodiment of the present invention, when the override switch is operated, the override is not directly applied to the control device 300 (see FIG. 5), but the grinding wheel rotation device 102 is first moved radially along the linear axis (U-axis) in a direction away from the object to be ground, and the override is applied. That is, the grinding apparatus 10 of an embodiment of the present invention has an automatic infeed device 104 that can feed or fix the grinding wheel rotation device 102, to which the grinding wheel 100 is attached, in the radial direction on a linear axis (U-axis), and further, the entire automatic infeed device 104, including the grinding wheel rotation device 102, is rotated by a separate rotation device (C-axis rotation device) 106 to grind the inner or outer surface of a circle (cylindrical if the thickness is taken into consideration) to be ground.In this grinding apparatus, the rotation speed of the separate rotation device (C-axis rotation device) 106 can be freely changed by the operator using an override switch, and when the override switch is operated, the operation is not immediately applied to the control device 300 (see Figure 5), but rather the automatic infeed device 104 is first operated to feed the grinding wheel rotation device 102 in the radial direction on the linear axis (U-axis) away from the grinding object, and then the override of the rotation speed of the separate rotation device (C-axis rotation device) 106 is applied. In addition, the grinding machine 10 may have a function that automatically performs the following operation: instead of immediately applying the override switch to the control device 300 (see FIG. 5), the automatic infeed device 104 is first operated to feed the grindstone rotation device 102 radially along the linear axis (U-axis) away from the workpiece, and then an override of the rotational speed of another rotation device (c-axis rotation device) 106 is applied, gradually returning the grindstone to the original coordinates (target coordinates for CNC control) over time. In addition, the grinding machine 10 may have a function that automatically performs the following operation when grinding the outside of the workpiece (e.g., when grinding the outer peripheral surface) and the inside of the workpiece (e.g., when grinding the inner peripheral surface). FIG. 6 is a graph showing the relationship between (a) the override command, (b) the automatic infeed position, and (c) the actual rotational speed in a grinding machine and a control method thereof according to an embodiment of the present invention.In the grinding machine and its control method according to an embodiment of the present invention, as shown in FIG. 6(a), when the override switch is operated, instead of immediately applying (to the control device 300 (see FIG. 5)), as shown by the dashed line in FIG. 6(b), the automatic cutting position by the automatic cutting device 104 is temporarily moved radially away from the object to be ground and then gradually returned to the original (coordinate) command position, and as shown in FIG. 6(c), the actual rotational speed also catches up with a corresponding delay.

[0020] 7 is a flowchart of the control process from start to finish of the grinding process in the grinding machine of this embodiment. Specifically, the grinding process is started in the grinding machine of this embodiment (S701). A check is made to see if an override switch is operated during grinding, causing an override change (S702), and a determination is made as to whether a speed change will occur (S703). If a speed change will occur (YES in S703), an additional clearance amount is calculated for the remaining clearance amount at that time (S704), the clearance direction is determined (S705), a clearance addition operation is performed (S706), and the speed is changed (S707). Cutting is performed at this changed speed, and a determination is made as to whether the grinding wheel rotation has ended (S708). If the grinding wheel rotation has ended (YES in S708), the grinding process ends (S709). On the other hand, if the grinding wheel 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.

[0021] The amount of overcut (radius change Δr) corresponding to a change in rotation speed is generally defined by the following formula (1): c(u) may be a constant, or it may be defined as a function related to the U-axis coordinate depending on the configuration of the automatic cutting device 104. In this case, the relationship between the U-axis coordinate and the radius change Δr for a constant R and ω may be investigated in advance, and the relationship may be defined using polynomial approximation or a table.

number

[0022] 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 apparatus having an automatic infeed device that can feed or fix a grinding wheel rotating device with a grinding wheel attached in the radial direction on a linear axis, and further capable of grinding the inner or outer surface of a circle by rotating the entire automatic infeed device including the grinding wheel rotating device on a separate rotating device, wherein the grinding apparatus is configured so that the rotation speed of the separate rotating device can be freely changed by an operator with an override switch, and wherein when the override switch is operated, rather than immediately applying the override to a control device, the automatic infeed device is first operated to feed the grinding wheel rotating device in the radial direction on a linear axis in a direction away from the object to be ground, and then the rotation speed override of the separate rotating device is applied, characterized in that the escape direction is changed when grinding the outside and when grinding the inside.

2. A grinding apparatus having an automatic infeed device that can feed or fix a grinding wheel rotating device with a grinding wheel attached in the radial direction on a linear axis, and further capable of grinding the inner or outer surface of a circle by rotating the entire automatic infeed device including the grinding wheel rotating device on a separate rotating device, wherein the grinding apparatus is configured so that the rotation speed of the separate rotating device can be freely changed by an operator with an override switch, and wherein when the override switch is operated, rather than immediately applying the operation to a control device, the grinding apparatus has a function of once operating the automatic infeed device to feed the grinding wheel rotating device in the radial direction on a linear axis in a direction away from the object to be ground, and then applying an override to gradually return it to the original coordinates over time, characterized in that the escape direction is changed when grinding the outside and when grinding the inside.

3. A grinding apparatus having an automatic cutting device that can feed or fix a grinding wheel rotating device with a grinding wheel attached in the radial direction using a linear axis, and further capable of grinding the inner or outer surface of a circle by rotating the entire device including the grinding wheel rotating device and the automatic cutting device using a separate rotating device, and configured so that an operator can freely change the rotation speed of the separate rotating device using an override switch, said grinding apparatus comprising: a first step of determining whether a speed change will occur if an override change occurs during processing; a second step of calculating an amount of escape addition and performing an escape addition operation if a speed change occurs; and a third step of changing the speed and performing cutting at this changed speed, wherein said first to third steps are performed in this order.

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