JP6879766B2 - Path correction method and control device for multi-axis machine - Google Patents

Description

The present invention relates to a path correction method and a control device for a multi-axis machine.

For example, in Patent Document 1, the actual machining position (predicted path) corresponding to the command position (target path) of each block of NC data is obtained, and the NC data is corrected by using the difference between the command position and the machining position as a correction amount. The correction method to be performed is disclosed. In the correction method of Patent Document 1, the correction amount is calculated based on the error between the processing position and the command position.

Japanese Unexamined Patent Publication No. 2012-254517

By the way, due to the characteristics of the motor provided in the multi-axis machine, for example, when machining so as to have a shape with a large curvature, the motor cannot follow the instructed output, and it is between the command position and the machining position. An error may occur. In such a case, even if the correction is performed by the method described in Patent Document 1, the actual processing path deviates greatly from the commanded path, for example, when processing a curved shape having a large curvature. It may not be possible to process it into a desired shape.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to more accurately correct a machining path of a multi-axis machine.

In the present invention, as a first means relating to a path correction method for solving the above problems, a region in contact with a work piece is set on a curved surface, and a long tool is moved with reference to a plurality of reference axes. This is a path correction method for machining the work piece, and is used to set a predicted path stored in advance at a reference point provided inside the tip of the tool and the work piece as a target shape. A configuration is adopted in which the position of the tool is corrected based on the error of the reference point from the target path.

As a second means relating to the path correction method, in the first means, the tool is an end mill, and the reference point is the tool center of the tool.

As a third means according to the path correction method, in the first or second means, the predicted path is calculated by measuring the motion locus of the tool in advance.

As a fourth means relating to the path correction method, in the first or second means, the predicted path is calculated in advance by simulating the motion locus of the tool.

As the first means related to the control device of the multi-axis machine, the area in contact with the work piece is set to a curved surface, and the long tool is moved with reference to a plurality of reference axes to be machined. A control device for a multi-axis machine that processes an object, which is a predictive path calculating means for calculating a predictive path of a motion locus of a reference point provided inside the tip of the tool by simulation, the predictive path, and the work to be machined. A configuration is adopted in which a correction means for correcting the momentum of the tool is provided based on an error of the reference point with the target path for setting the object into the target shape.

According to the present invention, the correction amount is determined based on a reference point provided inside the tool rather than the tip point of the tool of the multi-axis machine. Therefore, in the control, the position of the reference point can be grasped more accurately, and the machining path of the multi-axis machine can be corrected more accurately.

It is a schematic view of the multi-axis machine in one Embodiment of this invention, (a) is an overall view, and (b) is an enlarged view of a tool. It is a control block diagram in the X-axis, Y-axis and C-axis directions of the control device in one Embodiment of this invention. It is a control block diagram in the Z-axis direction of the control device in one Embodiment of this invention. It is a control block diagram in the B-axis direction of the control device in one Embodiment of this invention. It is a schematic diagram which shows the operation with respect to the workpiece of the tool of the multi-axis machine in one Embodiment of this invention. It is a flowchart which shows the operation of the control device in one Embodiment of this invention. It is a schematic diagram which shows the correction of the tool target path of the multi-axis machine in one Embodiment of this invention. It is a figure which shows the result of the correction by the control device in one Embodiment of this invention.

Hereinafter, an embodiment of the control device for the multi-axis machine according to the present invention will be described with reference to the drawings. In the drawings below, the scale of each member is appropriately changed in order to make each member recognizable.

First, the multi-axis machine 100 controlled by the control device 1 in the present embodiment will be described. In the following description, one direction parallel to the installation surface is defined as the X-axis direction, the direction parallel to the installation surface and perpendicular to the X-axis direction is defined as the Y-axis direction, and is perpendicular to the installation surface. The direction is the Z-axis direction. Further, the direction of rotation about the Y-axis is the B-axis direction, and the direction of rotation around the Z-axis is the C-axis direction.

The multi-axis machine 100 includes a column 110, a Y-axis base portion 120, a Z-axis base portion 130, a head portion 140, a table portion 150, and a swivel mechanism 160.

The column 110 is a rectangular parallelepiped member having a Y-axis base portion 120 installed at the upper portion, and has a rail mounting area protruding in the Y-axis direction at the lower portion. Two X-axis direction rails 111 are formed along the X-axis direction on the upper surface of the rail mounting area. A table portion 150 is installed on the X-axis direction rail 111. By moving the table portion 150 along the X-axis direction rail 111, the table portion 150 can be moved in the X-axis direction. The Y-axis base portion 120 has a flat plate shape perpendicular to the Z-axis, and two Y-axis direction rails 121 are formed on the upper surface along the Y-axis direction. A Z-axis base portion 130 is installed on the Y-axis direction rail 121. By moving the Z-axis base portion 130 along the Y-axis direction rail 121, the Z-axis base portion 130 can be moved in the Y-axis direction.

The Z-axis base portion 130 is movable along the Y-axis direction, and two Z-axis direction rails 131 are provided along the Z-axis direction on a plane in the direction along the Z-axis. Further, a head portion 140 is installed on the Z-axis direction rail 131. By moving the head portion 140 along the Z-axis direction rail 131, the head portion 140 can be moved in the X-axis direction. The head portion 140 is movable in the Z-axis direction, and has a tool post 141 protruding downward in the Y-axis direction and the Z-axis direction, and a tool 142.

A tool 142 included in the multi-axis machine 100 is attached to the lower surface of the tool post 141, and the tool 142 is rotatably held. As shown in FIG. 1B, the tool 142 has a long shape that is long in the rotation axis O direction, and is installed on the tool post 141 so that the rotation axis O is along the Z axis. The tip of the tool 142 is a spherical ball end mill, and the center point of the tip in the spherical region is the tool center point P1 (reference point). Further, in the tool 142, the point that protrudes most in the rotation axis O direction from the cutting tool 141 is defined as the action point P2.

The table portion 150 is movable along the X-axis direction, has a bottom portion provided in the Y-axis direction, and a side wall portion erected in the Z-axis direction, and has a Y-axis direction and a Z-axis. It is a member bent in a substantially L shape in the direction. The table portion 150 is provided with a swivel mechanism 160 on the side wall portion. The swivel mechanism 160 has a pallet 161 so that the pallet 161 can rotate in the B-axis direction and the C-axis direction. The pallet 161 is a member on which the workpiece W is placed and fixed.

The control device 1 is a device that calculates a route at the time of machining of the multi-axis processing machine 100, and includes a route calculation unit 1a (prediction route calculation means) and a route correction unit 1b (correction means). The control device 1 may be, for example, a computer and may include output means and input means (not shown). The path calculation unit 1a calculates the target path to be followed by the tool center point P1 of the tool 142 from the target shape of the workpiece W, and further, it is obtained by a simulation simulating the characteristics of the servo system of the multi-axis machine 100. The predicted path, which is the predicted path of the tool center point P1, is calculated from the position and angle, or the position and angle measured and recorded by the position or angle sensor of each moving axis of the multi-axis machine. The target route and the predicted route are a set of a plurality of coordinate values, and each is stored in the control device 1 as a table. The route correction unit 1b acquires the target route and the predicted route, calculates the difference value between the target route and the predicted route, reverses the sign of the difference value with respect to the target route, and adds the difference value.

The control configuration of each reference axis of the route correction unit 1b will be described with reference to FIGS. 2 to 4.
Of the reference axes, on the X-axis, Y-axis, and C-axis, as shown in FIG. 2, the P controller a performs proportional calculation processing on the difference value between the command value and the output of the integrator b, and the PI controller c performs proportional calculation processing. Proportional integration processing is performed on the difference value between the output of the P controller a and the control amount indicating the position of the feed shaft drive unit d. Further, the output obtained by adding the output of the friction compensator e to the output of the P controller a is supplied to the PI controller c as an operation amount. The integrator b integrates and outputs the control amount with a predetermined time constant, and the friction compensator e controls the correction coefficient corresponding to the drive friction in the feed shaft drive unit d. Multiply the quantity and output.

Further, on the Z axis, as shown in FIG. 3, the P controller a performs proportional calculation processing on the difference value between the command value and the output of the integrator b, and the PI controller c performs the output of the P controller a and the feed axis drive. Proportional integration processing is performed on the difference value from the control amount indicating the position of part d. Further, the output of the PI controller c minus the disturbance force f due to gravity is supplied to the feed shaft drive unit d as an operation amount. Further, the output obtained by adding the output of the friction compensator e to the output of the P controller a is supplied to the PI controller c as an operation amount. The integrator b integrates and outputs the control amount with a predetermined time constant, and the friction compensator e controls the correction coefficient corresponding to the drive friction in the feed shaft drive unit d. Multiply the quantity and output.

Further, on the B axis, as shown in FIG. 4, the P controller a performs proportional calculation processing on the difference value between the command value and the output of the integrator b, and the PI controller c performs the output of the P controller a and the feed axis drive. Proportional integration processing is performed on the difference value from the control amount indicating the position of part d. Further, the output of the PI controller c minus the disturbance torque g due to gravity is supplied to the feed shaft drive unit d as an operation amount. Further, the output obtained by adding the output of the friction compensator e to the output of the P controller a is supplied to the PI controller c as an operation amount. The integrator b integrates and outputs the control amount with a predetermined time constant, and the friction compensator e controls the correction coefficient corresponding to the drive friction in the feed shaft drive unit d. Multiply the quantity and output.

The multi-axis machine 100 is a 5-axis machine capable of moving the tool 142 in the Y-axis direction and the Z-axis direction and moving the workpiece W in the X-axis direction, the B-axis direction, and the C-axis direction. .. During machining, the multi-axis machine 100 orbits around the workpiece W while the point of action P2 is constantly in contact with the workpiece W, as shown in FIG. At this time, the tool 142 and the workpiece W are moved so that the rotation axis O of the tool 142 is always in the normal direction of the workpiece W. As a result, the tool 142 always comes into contact with the workpiece W in the curved surface region.

Subsequently, the route correction method of the control device 1 in the present embodiment will be described with reference to FIG.

First, the control device 1 calculates the target route (step S1). In step S1, the path calculation unit 1a acquires the target shape of the workpiece W, and calculates the target path to be followed by the tool center point P1 of the tool 142 with respect to the workpiece W from the target shape. Further, the control device 1 calculates the prediction route (step S2). In step S2, the path calculation unit 1a calculates the path to be followed by the tool 142 when the tool 142 is moved along the target path by numerical calculation simulation.

Next, the control device 1 calculates the difference between the target route and the predicted route (step S3). In step S3, the path correction unit 1b calculates and stores the difference value between the coordinates on the predicted path predicted to be followed by the tool center point P1 and the coordinates on the corresponding target path. Further, the control device 1 performs the route correction (step S4). In step S4, as shown in FIG. 7, the sign of the difference value is inverted, a correction path added to the coordinates on the target path is calculated, and the calculated correction path is set as a new target path on the new target path. The coordinate values are output to the multi-axis processing machine 100. The vector direction of the difference value is the same as or substantially the same as the normal direction of the target path in FIG. 7.

FIG. 8 shows the target shape of the workpiece W according to the present embodiment, and the points of action (tip points) when the correction is not performed, when the correction is performed by the conventional method, and when the correction is performed according to the present invention. It is a figure which compares the motion locus.
The target shape of the workpiece W is a flat shape that is long in the Y-axis direction and has the maximum thickness in the X-axis direction in the central region in the Y-axis direction. It is said that. Further, the curvature of the other end of the workpiece W is set to be larger than that of one end in the Y-axis direction.

When the correction shown in FIG. 8A is not performed, the end portion of the workpiece W in the Y-axis direction is largely deviated inward from the target shape shown by the broken line. Then, in the result when the correction by the conventional method shown in FIG. 8 (b) is performed, the target shape shown by the broken line is closer than that when the correction is not performed, but at the end portion on the side where the curvature is large, the tool is used. Since the angle formed by the trajectory of the actual machining path changes, the amount of error cannot be calculated correctly, and the shape is shifted outward from the target system. On the other hand, the corrected shape in the present embodiment shown in FIG. 8 (c) is not affected by the change in the angle formed by the locus of the tool and the machining path. It is almost the same.

In CAM (computer aided manufacturing), which is a machining program of the multi-axis machine 100 stored in the control device 1, the action point of the tool on the setting is described in the CL data which is the tool position information, and the action point P2 described above is described. It is said that. During actual machining, the locus of the machining path has a motion error, so that the angle formed by the tool 142 and the locus of the machining path changes even if the tool postures are the same. Therefore, the conventional method of performing error correction using the point of action P2 as a reference point has a problem that the amount of error between the target shape and the locus of the processing path cannot be calculated correctly. In the control device 1 according to the present embodiment, attention is paid to a reference point (tool center point P1) provided inside the tip of the tool 142, and the angle formed by the tool 142 and the locus of the machining path changes. However, the error can be calculated accurately without being affected.

According to the control device 1 of the multi-axis machine 100 in the present embodiment, the correction path is calculated based on the difference between the target path and the predicted path of the tool center point P1 of the tool 142. Therefore, even if the locus of the action point P2 set in the machining program and the locus of the action point P2 actually traced are different due to the inclination of the locus due to the motion error or the like, the control device 1 is the multi-axis machine 100. The amount of error can be accurately calculated based on the position of the tool center point P1 of the above, and correction can be performed. Therefore, as shown in the result of FIG. 8, the machining path of the multi-axis machine 100 can be corrected more accurately.

Further, according to the control device 1 in the present embodiment, the reference point is the tool center point P1. The tool center point P1 is equidistant to any contact position even when the contact position with the workpiece W at the tip of the tool 142 changes. Therefore, the error can be calculated and corrected without changing the reference point depending on the contact posture of the tool 142.

Further, the multi-axis machine 100 in the present embodiment calculates a predicted path by simulation. Therefore, the prediction path can be easily calculated without actually processing by the multi-axis processing machine 100.

Although the preferred embodiment of the present invention has been described above with reference to the drawings, the present invention is not limited to the above embodiment. The various shapes and combinations of the constituent members shown in the above-described embodiment are examples, and can be variously changed based on design requirements and the like without departing from the spirit of the present invention.

(1) In the above embodiment, the predicted path is calculated by simulation, but the present invention is not limited to this. The predicted path may be measured by actually moving the multi-axis machine 100. In this case, since the control device 1 can acquire the characteristics of the actual servo system of the multi-axis machine 100, more accurate correction can be performed, and even in the result of using the actual machine, the shape error is almost the same. It disappears.

(2) In the above embodiment, the tool 142 is a ball end mill, but the present invention is not limited to this. The tool 142 may be a radius end mill, a square end mill, a barrel tool, or the like. In the case of the barrel tool as well, it is assumed that the reference point is provided inside the tip of the barrel tool and the contact position with the workpiece W is the side peripheral surface. The shape (type) of the tool is not particularly limited to the above-exemplified one, and the present invention can be applied as long as the motion locus of the tool to be used in advance can be simulated using the tool center position P1 and the action point P2 and the like. Is.

(3) Further, in the above embodiment, the control device 1 calculates the predicted route by the route calculation unit 1a, but the control device 1 does not calculate the predicted route, and the predicted route is calculated by a separate computer or the like. May be calculated.

(4) Further, the control device 1 in the above embodiment may be provided in the multi-axis processing machine 100.

(5) Further, in the present embodiment, the two-dimensional path correction method has been described as an example, but the present invention is also applicable to the three-dimensional path correction.

(6) Further, in the above embodiment, the control device 1 uses the tool center point P1 as a reference point, but the present invention is not limited to this, and the tool 142 has a tool 142 rather than an action point P2. If it is inside, the position of the reference point is not limited. When a tool center point other than the tool center point P1 is used as a reference point, an error is obtained by adding or subtracting the difference between the coordinates of the reference point and the tool center point P1 as in the case of using the tool center point P1 as a reference point. Can be calculated and corrected.

1 Control device 1a Path calculation unit 1b Route correction unit 100 Multi-axis machine 110 Column 111 X-axis direction rail 120 Y-axis base part 121 Y-axis direction rail 130 Z-axis base part 131 Z-axis direction rail 140 Head part 141 Tool base 142 Tool 150 Table part 160 Swivel mechanism 161 Pallet a Controller b Integrator c Controller d Axis drive unit e Friction compensator f Disturbance force g Disturbance torque O Rotation axis P1 Tool center point P2 Action point W Work piece

Claims (5)

A path correction method for machining the work piece by setting a curved surface in contact with the work piece and moving a long tool with reference to a plurality of reference axes.
The position of the tool is determined based on the error between the predicted path stored in advance at the reference point provided inside the tip of the tool and the target path of the reference point for setting the workpiece into the target shape. Correct and
The feed shaft drive unit that drives the reference shaft is controlled by adding a correction coefficient corresponding to the drive friction of the reference shaft.
Among the plurality of reference axes, the Z-axis, which is a direction perpendicular to the installation surface of the workpiece, is controlled to drive the feed shaft drive unit so as to feedforward-correct and drive the disturbance force due to gravity. A path correction method characterized in that the feed shaft drive unit is controlled so as to feedback-correct and drive the disturbance torque for the B-axis that rotates around an axis parallel to the installation surface. The tool is an end mill.
The path correction method according to claim 1, wherein the reference point is the center of the tool. The path correction method according to claim 1 or 2, wherein the predicted path is calculated in advance by measuring the motion locus of the tool. The path correction method according to claim 1 or 2, wherein the predicted path is calculated in advance by simulating the motion locus of the tool. A control device for a multi-axis machine that processes a work piece by setting a curved surface in contact with the work piece and moving a long tool with reference to a plurality of reference axes.
Prediction path calculation means for calculating the prediction path of the motion locus of the reference point provided inside the tip of the tool by simulation, the prediction path, and the target path of the reference point for setting the workpiece as the target shape. With a correction means for correcting the position of the tool based on the error of
The correction means controls a feed shaft drive unit that drives the reference shaft in consideration of a correction coefficient corresponding to the drive friction of the reference shaft, and among the plurality of reference shafts, on the installation surface of the work piece. The feed shaft drive unit is controlled so as to feedforward-correct and drive the disturbance force due to gravity for the Z axis in the vertical direction, and the disturbance torque for the B axis rotating around the axis parallel to the installation surface. A control device for a multi-axis machine, characterized in that the feed shaft drive unit is controlled so as to drive the feed shaft with feedback correction.

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