JPH07328891A - Hole position copying work method - Google Patents

Abstract

PURPOSE:To work a hole having a normal shape in a prescribed position regulated by a prepared hole even if work is started in a condition where dislocation exists between the center of the prepared hole and the rotational center of a rotary tool. CONSTITUTION:A maximum value of cutting force F by synthesizing loads of servomotors 50 and 51 on the X axis and the Y axis to support a work object 207 through a table 204, that is, a maximum value Fm of translational force acting on the table 204 in single rotation of a drill 203a is detected, and a turning angle A of a chisel edge of the drill 203a corresponding to this is found by using a coordinate system of the table 204 as a reference. The table 204 is moved by an extremely small quantity L in the direction of the turning angle A, and a change in the maximum value Fm is detected, and the dislocated direction of the drill 203a to a prepared hole 208 is specified, and the table 204 is sent in the direction for reducing the maximum value Fm, and the center of the drill 203a and the center of the prepared hole 208 are made to coincide with each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hole position for aligning the center of a prepared hole with the center of rotation of a rotary tool in hole drilling for expanding the hole diameter by cutting the inner circumference of the prepared hole with a rotary tool. The present invention relates to a copying method.

[0002]

2. Description of the Related Art Hole making which cuts the inner circumference of a prepared hole previously formed in a workpiece with a rotary tool to expand the hole diameter is already known. For example, secondary making of hole making by a drill. It is also known as deburring and spot facing by a reamer, and further, inner circumference grinding of a cylinder by a jig grinder that makes a planetary motion. In hole drilling and deburring with a drill or reamer, the rotary tool simply rotates and cuts the inner peripheral surface of the work piece with the cutting edges of its tip and outer periphery.
In the case of a jig grinder, the rotating tool revolves while rotating and revolves to cut the inner peripheral surface of the workpiece, but the revolution radius of the jig grinder is the tool radius of the rotating tool in the drill or reamer, and the jig grinder The center of revolution is regarded as the center of rotation of the tool in the drill or reamer.At the same time, the revolution movement of the jig grinder is regarded as the rotation of the rotating tool in the drill or reamer, and the whetstone of the jig grinder that rotates is regarded as the drill or reamer. From the point of view of operation, there is no significant difference between the hole removal and deburring process by a drill or reamer and the inner circumference grinding of a cylinder by a jig grinder from the viewpoint of operation.

Needless to say, in this type of hole drilling and similar machining, it is most important to start the machining by aligning the center of rotation of the tool with the center of the prepared hole, and the centers of both are offset. If this happens, problems such as noise due to chattering of the tool, breakage of the tool itself, and biting into the workpiece become problems. Naturally, if the center of rotation of the tool and the center of the prepared hole do not match, it is not possible to form a hole with a normal shape at the prescribed position defined by the prepared hole. It is even possible that the bearing part) will be damaged and the processing accuracy thereafter cannot be guaranteed.

Therefore, when it is not possible to be confident in the positioning accuracy when a workpiece having a prepared hole is placed on the table, the center of the rotary tool is previously determined according to the prepared hole position of the workpiece. It is necessary to match the positions.

As means for matching the center position of the rotary tool in accordance with the prepared hole position of the work piece, after the work piece is placed on the table, the prepared hole position is read from the machining drawing,
The touch probe of the machine tool is applied to the design reference surface of the work piece to adjust the origin of the machine coordinate system, and then the table is fed to the predetermined position on the machining drawing, and the prepared hole position and rotary tool Check the contact between the probe and the inner peripheral surface of the pilot hole by inserting the touch probe directly into the pilot hole of the workpiece and sending the table in the forward and reverse directions of the X axis. The maximum and minimum values at the time are read from the X-axis position detecting means to obtain an average value, and Y
A method is known in which an average value for the Y-axis is obtained by performing the same operation for the axes and the table is sent to the coordinate position defined by each average value. However, the operations are both cumbersome and time-consuming. In addition, there is a problem that the achievable positioning accuracy varies depending on the operator. After all, it is difficult to guarantee that the alignment accuracy at the start of hole drilling will converge to a predetermined range even with the method described above, and if the hole drilling work is started while the alignment is incomplete, the above-mentioned problem occurs. Will result.

[0006]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to perform the machining as it is when there is a slight deviation between the center of the prepared hole and the rotation center of the rotary tool. To provide a hole position copying machining method capable of performing a hole having a normal shape at a predetermined position defined by a prepared hole without adversely affecting a rotating tool, a work piece, and a machine tool even if started. is there.

[0007]

SUMMARY OF THE INVENTION The present invention detects a cutting force acting on a rotary tool during hole making, corresponding to the rotational position of the rotary tool, and the cutting force of the rotary tool becomes maximum or minimum. Obtaining the rotational position, in the direction of the rotational position of the rotating tool which becomes the maximum or minimum, in the direction in which the fluctuation of the cutting force becomes small,
The above object was achieved by moving the rotary tool relative to the workpiece in a plane orthogonal to the rotation axis of the rotary tool.

Further, the center of the prepared hole and the center of rotation of the rotary tool are automatically moved by automatically moving the rotary tool relative to each other by a set amount in a direction in which the variation of the cutting force is reduced for each rotation of the rotary tool. So that they can be matched.

Further, the load of the motor of each axis for relatively moving the rotary tool and the workpiece in the plane orthogonal to the rotary axis of the rotary tool is obtained, and the loads are combined to obtain the cutting force, whereby the rotation is performed. Regardless of the number of blades of the drill etc. forming the tool, it is possible to accurately detect the one-sided contact of the rotating tool with respect to the prepared hole and ensure that the center of the prepared hole and the rotation center of the rotating tool can be matched. .

Further, the rotational position of the rotary tool at which the cutting force becomes maximum and minimum is obtained, and the set amount is proportional to the set amount for each rotation of the rotary tool until the difference between the maximum and the minimum becomes a set value or less. By automatically moving the rotary tool relative to the work piece in the direction in which the fluctuation of the cutting force is reduced by the amount, it is possible to prevent the careless vibration motion of the rotary tool after the center positions match. .

[0011]

[Operation] The cutting force that acts on the rotary tool during hole drilling is detected in correspondence with the rotary position of the rotary tool, and the rotary position of the rotary tool that maximizes or minimizes the cutting force is calculated. The rotating tool is relatively moved with respect to the workpiece in a plane orthogonal to the rotation axis of the rotating tool in a direction in which the fluctuation of the cutting force decreases in the direction of the rotational position of the rotating tool.

The fluctuation of the cutting force of the rotary tool depends on the cutting edge of the rotary tool formed discontinuously with respect to the circumferential direction of the rotary tool on the same plane orthogonal to the center of rotation at the tip or outer peripheral portion of the rotary tool. It occurs depending on whether the inner peripheral surface of the prepared hole is cut under various circumstances.For example, in the case of a drill, it depends on how much the tip of the chisel edge at the tool tip bites into the inner peripheral surface of the prepared hole. Be different. In addition, the difference in the cutting edge of the cutting edge directly reveals how the center of rotation of the tool deviates from the center of the prepared hole, that is, at which rotational position the chisel edge comes in the prepared hole. The direction of misalignment of the rotary tool with respect to the prepared hole is specified depending on whether the peripheral surface is deepest or shallowly cut, that is, at which rotational position the chisel edge comes to have the maximum or minimum cutting force. More specifically, if the cutting force is the maximum, the tool is displaced with respect to the prepared hole at the time by the extension line of the chisel edge that goes outward in the tool radial direction. Based on the case where the force is the minimum, the tool is displaced with respect to the prepared hole at that time in the direction of the extension line of the chisel edge directed inward in the tool radial direction.

Therefore, in the present invention, the rotational position of the rotary tool at which the cutting force is maximum or minimum is obtained, and the variation of the cutting force is reduced, that is, the rotational position of the rotary tool at which the cutting force is maximum or minimum. In the case of the drill, in the case of the drill, the relative feed is applied to the tool in the direction of the extension line of the chisel edge that goes inward in the radial direction of the tool when the rotational position where the cutting force is maximum is used as the reference, and When the rotational position that minimizes the cutting force is used as a reference, the tool is relatively fed in the direction of the extension line of the chisel edge that extends outward in the radial direction of the tool, and the rotational center of the tool is aligned with the center of the prepared hole. .

Further, by automatically moving the rotary tool by a set amount in a direction in which the fluctuation of the cutting force is reduced for each rotation of the rotary tool, the center of the prepared hole and the center of rotation of the rotary tool are Displacement is eliminated in the initial stage of hole drilling start.

Here, in the case of a rotary tool such as a drill having two blades, when one chisel edge cuts the inner peripheral surface of the prepared hole deepest, the other chisel edge cuts the inner peripheral surface of the prepared hole. When cutting at the shallowest, and when the diameter connecting both chisel edges is orthogonal to the direction of deviation of the center position, a phenomenon occurs in which both chisel edges cut the inner peripheral surface of the prepared hole to a medium degree, respectively. If the stationary torque acting on the rotating tool is directly detected as the cutting force from the driving source of the rotating tool, the sum of the load resistance moments around the tool axis becomes constant, and the cutting force becomes uniform. It may be difficult to detect the minimum cutting force. However, if the load of the motor of each axis that moves the rotary tool and the workpiece relative to each other in the plane orthogonal to the rotary axis of the rotary tool is detected, and the load is combined to obtain the cutting force, Of the force that the tool gives to the work piece, a biased moment that does not form a pair with the center of rotation of the rotary tool as a reference, that is, not a couple force, but a partial contact of the rotary tool such as a drill Since the force capable of translating the object is accurately detected, the cutting force associated with the biting condition of the cutting edge is appropriately obtained.

Further, the relative movement of the tool per revolution determined according to the set amount or the difference between the maximum and the minimum of the cutting force is such that the difference between the maximum and the minimum of the cutting force during one revolution is less than the set value. When the tool and the center position of the prepared hole are aligned, the tool shaft will not be inadvertently vibrated in the radial direction due to subsequent minute load fluctuations. Absent.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 5A is a side view schematically showing an example of the machine tool 200 used for hole making, and FIG. 5B is the same side view. Needless to say, 201 is a column, 2
Reference numeral 02 is a machining head provided with a vertical spindle, 203 is a rotary tool mounted on the tip of the spindle, 206 is a bed, 205 is a saddle, and 204 is a table for mounting and fixing a workpiece. The saddle 205 is placed on a fixed element such as a guide rail fixedly provided on the bed 206 side, and its sliding direction is restricted only to the Y-axis direction. It is mounted on a fixed element such as a guide rail fixed to the side, and the sliding direction with respect to the saddle 205 is restricted only to the X-axis direction. Saddle 2
There is a configuration in which 05 is omitted and a cross key is interposed between the table 204 and the bed 206.
The sliding function of the table 204 based on 6 is the same as above. Also, in the example shown in FIG.
Processing head 2 mounted on a column 201 fixed to
02 is configured to be vertically movable along the Z-axis, and the Z-axis servo motor 5 is configured to move the processing head 202 in the vertical direction.
2. Y-axis servo motor 51 for feeding the table 204 in the Y-axis direction via the saddle 205, table 204
Each of the X-axis servomotor 50 for feeding the X-axis direction and the spindle motor 62 for rotating the main shaft on which the rotary tool 203 is mounted is appropriately drive-controlled by the numerical controller 10 described later. In the example of the machine tool 200 of FIG. 5 having a vertical spindle, the axes for moving the rotary tool 203 relative to the workpiece in a plane orthogonal to the spindle are of course the X axis and the Y axis. become. Here, a machine tool 20 corresponding to a drilling machine, a milling machine, or the like.
The jig grinder that grinds the inner circumference of the cylinder is not particularly described, but the revolution radius of the jig grinder is the tool radius of the rotary tool 203, and the center of the revolution of the jig grinder is the rotation center of the rotary tool 203. At the same time, the revolving movement of the jig grinder is simultaneously controlled by the rotary tool 2
If the grinding stone of the jig grinder that rotates is considered as the cutting edge of the rotary tool 203, the rotary tool 20 of the machine tool 200 is seen from the point of operation.
There is no great difference between the hole making and deburring process by No. 3 and the inner peripheral grinding of the cylinder by the jig grinder.

FIG. 1 is a block diagram showing an outline of a numerical controller 10 for driving and controlling a machine tool 200. The processor 11 is a processor for controlling the numerical control apparatus 10 as a whole, reads a system program stored in the ROM 12 via the bus 21, and executes the control of the numerical control apparatus 10 as a whole according to the system program. R
Temporary calculation data, display data, etc. are stored in the AM 13, and the current load values of the servo motors 50, 51 for each axis obtained by the servo control CPU provided in the axis control circuits 30, 31 for each axis are also stored. The data is sequentially updated and stored here. The CMOS 14 is backed up by a battery (not shown), and is configured as a non-volatile memory that retains a storage state even when the numerical control device 10 is powered off.

The interface 15 is an interface for an external device, and is connected to an external device 72 such as a paper tape reader, a paper tape puncher, a paper tape reader / paper tape puncher, or the like. The processing program is read from the paper tape reader, and the processing program edited in the numerical controller 10 can be output to the paper tape puncher.

A PMC (Programmable Machine Controller) 16 controls the machine tool 200 with a sequence program built in the numerical controller 10. That is, according to the function instructed by the machining program, the sequence program converts the signals into those required on the machine tool 200 side, and outputs the signals from the I / O unit 17 to the machine tool 200 side. This output signal activates various actuators on the machine tool 200 side. Further, it receives signals from limit switches on the machine tool 200 side and various switches on the machine control panel, performs necessary processing, and passes the signals to the processor 11.

Current position of each axis, alarm, parameter,
Image signals such as image data are sent to the CRT / MDI unit 70.
Is sent to the display device and displayed on the display device. The interface 18 receives the data from the keyboard in the CRT / MDI unit 70 and transfers it to the processor 11. The interface 19 is connected to the manual pulse generator 71 and receives pulses from the manual pulse generator 71. The manual pulse generator 71 is mounted on the machine operation panel on the machine tool 200 side, and is used for manually positioning the movable part of the machine precisely.

The axis control circuits 30 to 32 receive the movement command of each axis from the processor 11 and output the command of each axis to the servo amplifiers 40 to 42. In response to this command, the servo amplifiers 40-42 receive the servo motors 50-5 for the respective axes described above.
Drive 2 X-, Y-, and Z-axis servo motors 50 to 52
Has a built-in pulse coder for position detection, the position signal from this pulse coder is fed back to the axis control circuits 30 to 32 as a pulse train, and the speed obtained by F / V (frequency / velocity) conversion of the pulse train. Detection signal v
x, vy, vz are fed back to the axis control circuits 30-32. Each of the servo control CPUs incorporated in the axis control circuits 30 to 32 performs each processing of a position loop, a velocity loop, and a current loop based on these feedback signals and the above-mentioned movement command, for final drive control. The torque commands ux, uy, uz are obtained for each axis to control the positions and speeds of the servomotors 50 to 52 of the respective axes. In this embodiment, each axis that moves the rotary tool 203 relative to the workpiece in a plane orthogonal to the main axis, that is, the X axis and the Y axis.
Loads Tdx, T acting on the axis servomotors 50, 51
dy is obtained individually, the loads are combined, and the rotary tool 2
The cutting force of No. 03 is obtained, and the loads Tdx and Tdy acting on each axis need to be obtained. Therefore, load torques Tdx and Tdy are estimated by forming observers 160x and 160y for the servo motors 50 and 51 of each axis. I am trying to do it. The load torque Tdz further acting on the Z-axis is obtained by the same configuration, and the load torques Tdx, Tdy, Td are calculated.
Alternatively, z may be combined to obtain the cutting force of the rotary tool 203.

Since the configurations of the observers 160x and 160y for each axis are substantially the same, the function of the observer 160x of the X-axis servomotor 50 will be described below with reference to the block diagram of FIG. .

In FIG. 3, elements 152 and 153 are terms of the transfer function of the servomotor 50. The torque command ux output by the speed loop processing is multiplied by the torque constant Kt of the servomotor 50 to obtain the torque. Is added with the additional torque Tdx and divided by the inertia J to obtain a motor speed Vx. Elements 161, 1
“B” of 65 is the torque constant K of the X-axis servomotor 50
It is an estimated ratio of t and inertia J. That is (Kt / J)
Is an estimated value of. Also, K1 and K2 of the elements 162 and 163
Is a parameter of this observer, S is a Laplace operator, and element 164 represents an integral element.

Referring to the block diagram of the observer in FIG. 3, b = Kt
When analyzed as / J, {ux · Kt + Tdx} (1 / J · S) = vx (1) {ux · (Kt / J) + (vx−vxa) K1 + (vx−vxa) (K2 / S )} (1 / S) = vxa (2) (Note that vxa is the output of the integral element 164 and the estimated speed) From the equation (1), ux = (vx · J · S−Tdx) / Kt (3) ) By substituting the equation (3) into the equation (2) and rearranging, (vx · J · S−Tdx) / J + (vx−vxa) K1 + (vx−vxa) (K2 / S) = vxa · S (4) S (vx-vxa) + (vx-vxa) .K1 + (vx-vxa) (K2 / S) = Tdx / J (5) From formula (5), (vx-vxa) = (Tdx / J) · {1 / [S + K1 + (K2 / S)] (6) From the equation (6), the integrated value Tdx1 which is the output of the element 163 is expressed by the following equation (7). Tdx1 = In (vx-vxa) · (K2 / S) = (Tdx / J) · {K2 / S 2 + K1 · S + K2} ... (7) (7) equation, the parameters K1, K2 so pole is stabilized If selected, Tdx1 = Tdx / J can be approximated. If the calculated integral value Tdx1 is multiplied by the reciprocal 1 / b (= J / Kt) of the estimated ratio b (processing of element 165), Tdx2 = Tdx1. (1 / b) = (Tdx / J). ( J / Kt) = (Tdx / Kt) (8) and the estimated value Tdx of the load torque Tdx (proportional to it)
2, that is, the load torque Tdx is a torque command (current command)
The value obtained in the unit of is obtained (if Tdx is divided by the torque constant, the same dimension as the torque command ux is obtained).

In this way, the X-axis servomotor 50
Observer 160x for the servomotor 5
The load torque Tdx applied to 0 is calculated.

FIG. 4 shows a servo control C of the axis control circuit 30.
6 is a flowchart of processing executed by the PU for controlling the X-axis servomotor 50 in each speed loop processing cycle, and the processing of the observer 160x is mainly described.
The parameters K1 and K necessary for this observer processing are
2. The estimated ratio b is set in advance.

The servo control CPU of the axis control circuit 30 executes the processing shown in FIG. 4 every speed loop processing cycle.
The actual speed vx (i) of the motor sent from the pulse coder of the servomotor 50 is read, and the torque command ux stored and obtained by the speed loop processing of the previous cycle is read.
Read (i-1) (steps A1 and A2). Next, a value obtained by subtracting the estimated speed vxa (i-1) estimated in the previous cycle stored in the register from the actual speed vx (i) read in step A1 is added to the parameter K2 as the integral gain of the observer and the speed loop period Ts. The value multiplied by is added to the integrated value Tdx1 (i-1) up to the previous cycle stored in the accumulator to obtain the integrated value Tdx1 (i) of the observer in the cycle. That is, the processing of the element 163 in FIG.
1 is obtained (step A3).

Next, the torque command ux (i-1) of the previous cycle stored in the register is multiplied by the estimated ratio b of (torque constant / inertia), and the integrated value Tdx obtained in step A3.
1 (i), and a value obtained by subtracting the estimated speed vxa (i-1) obtained in the previous cycle stored in the register from the actual speed vx (i) of the cycle read in step A1, and the parameter K1 as a proportional gain. The value obtained by multiplying the added value by the speed loop period Ts, and then multiplying the added value by the estimated speed vxa
It is added to (i-1) to obtain the estimated speed vxa (i) of the cycle (step A4). That is, element 16 in FIG.
The process of obtaining the estimated speed vxa is executed according to 4.

Then, the integrated value Tdx obtained in step A3
The estimated value Tdx2 (i) of the load torque is obtained by multiplying 1 (i) by the reciprocal of the estimated ratio b of (torque constant / inertia) (step A5). The estimated value Tdx2 (i) of the load torque thus obtained is updated and written in the register of the RAM 13 as the current value of the load torque acting on the X-axis servomotor 50 (step A6). Then, the speed command obtained by the position loop processing similar to the conventional one is read, and the speed command and the actual speed vx (i) read in step A1 perform the speed loop processing similar to the conventional one, and the torque command ux.
(I) is obtained and stored in the register, and is also passed to the current loop, and the processing of the speed loop is finished (step A8).

By the above processing, the estimated load torque Tdx2 proportional to the current value of the load torque acting on the X-axis servomotor 50 is stored in the RAM 13.

Similarly, the servo control CPU of the axis control circuit 31 performs the same processing as the above in the processing of its speed loop, and the load torque acting on the Y-axis servo motor 51 is stored in the RAM 13. The estimated load torque Tdy2 proportional to the current value is stored.

The spindle control circuit 60 also outputs a spindle speed signal to a spindle amplifier 61 in response to a spindle rotation command and a spindle orientation command. The spindle amplifier 61 receives the spindle speed signal and rotates the spindle motor 62 at the commanded rotation speed. Further, the rotation position of the main shaft is positioned at a predetermined position by the orientation command.

The spindle motor 62 is connected with a main shaft by a gear or a belt, and a position coder 63 is connected with the main shaft. Therefore, the position coder 6
3 rotates in synchronization with the main axis and outputs a feedback pulse, which is read by the processor 11 via the spindle control circuit 60. As a result, the position and speed of the spindle motor 62 can be controlled. The position coder 63 outputs one rotation signal once at a predetermined rotation position of the spindle directly connected to the rotary tool 203.

Observers 160x, 16 are provided for the X-axis servo motor 50 and the Y-axis servo motor 51, respectively.
By setting 0y, the present values of the load torques Tdx and Tdy acting on the X and Y axes are calculated in real time to obtain R
Except for the fact that AM13 is updated and stored,
The hardware of the numerical control device 10 (obviously excluding the software program) and the configuration of the machine tool 200 are the same as those of the conventional product.

The hole position copying method according to this embodiment will be described below with reference to the case where secondary drilling is performed by using the drill 203a as a rotary tool by the machine tool 200 such as a drilling machine or a milling machine.

FIG. 6A is a schematic view showing the outline of the secondary processing by the drill 203a. Reference numeral 207 denotes a work piece in which a prepared hole 208 is formed in advance, which is placed and fixed on the table 204 of the machine tool 200. It should be noted that this example is not an example of the case where the workpiece 207 is placed and fixed on the table 204 and the secondary machining is performed by performing the automatic tool exchanging work or the like (in this case, the spindle The positional deviation does not pose a problem), the work piece 207 having the prepared hole 208 formed by the primary machining or the like by another machine tool is again mounted and fixed on the table 204 of the machine tool 200 to start the secondary machining. In the case of, for example, the case where the machine tool 200 performs the primary machining of the prepared hole AKE, then removes it from the table 204, performs the mounting and fixing work again, and then starts the secondary machining. Example, in short, drill 20 with table feed by inputting the feed amount numerically
This is a processing example in the case where it is difficult to completely match the center of 3a with the center of the prepared hole 208.
Before starting the next processing, the center of the drill 203a should be substantially aligned with the center of the prepared hole 208 by a conventionally known method, for example, a positioning method using a processing drawing or a touch probe. Although it is possible to perform the positioning work in the initial stage with the amount of division, this embodiment is for carrying out the work of correcting the positional deviation of the center position after the drill 203a actually contacts the workpiece 207. In order to perform more accurate machining, it may be rough, but it is desirable to perform some positioning work before starting the secondary machining.

FIG. 7 is a conceptual diagram showing an example of the positional deviation which could not be removed by the positioning work at the initial stage. Next, referring to FIG. 7, the principle of operation of the hole position copying machining method in this embodiment. Will be explained.

In FIG. 7, G is the center of the prepared hole 208 and g is the center of rotation of the drill 203a. There is a positional deviation between the center G and the center g which cannot be removed by the conventional positioning work before the start of machining. Exists. r is pilot hole 2
08 radius, R is a drill 20 used for hole machining of secondary processing
The tool radius is 3a, and naturally the tool radius R is larger than the radius r of the prepared hole. If the Z-axis servomotor 53 is driven and the machining head 202 is lowered to start the hole machining for the secondary machining as it is in the state shown in FIG. 7, the blade of the drill 203a naturally moves to the prepared hole 208. In the workpiece 207, the hatched portion in the drawing is cut more than necessary, and the amount of cutting is insufficient on the inner peripheral surface of the prepared hole 208 opposite to this. Will be done. Since the main force acting around the axis of the drill 203a is the cutting resistance when the chisel edge of the drill 203a rushes into the work piece 207 and squeezes a part of it to separate it, if the cutting of the drill 203a The blade is 1
If the number of chisel edges is one and the cutting force acting on the drill 203a is one cycle for one rotation of the spindle as shown in FIG. 6 (b) in relation to the rotation angle of the drill 203a. Fluctuation occurs.

That is, since the drill 203a is constantly fed at a predetermined speed in the Z-axis direction by the lowering of the machining head 202, the chisel edge always moves the uncut surface of the inner peripheral surface of the prepared hole 208 in the Z-axis direction, In short, it will be cut with a constant width along the depth direction of the prepared hole, and the cutting width in the XY plane is the biting amount of the chisel edge with respect to the inner peripheral surface of the prepared hole 208, that is, the figure. It is proportional to the thickness of the crescent-shaped hatched portion shown in Fig. 7 in the radial direction of the drill system. Since the cutting width in the Z-axis direction is constant, the cutting resistance naturally changes in proportion to the thickness of the crescent-shaped hatched portion. For example, when the chisel edge is at the rotation position H1 in FIG. It becomes the minimum, then the cutting resistance gradually increases from reaching the rotation position of H2, reaches the maximum at the rotation position of H via H4, and further increases H5, H
3, the phenomenon opposite to the above occurs as it moves to the rotational position of H1, and the cutting resistance gradually decreases, and thereafter, the same phenomenon repeatedly occurs every one rotation of the drill 203a. Therefore, as a result, the cutting resistance acting on the drill 203a repeats a sinusoidal variation for each rotation of the spindle as shown in FIG. 6B in relation to the rotation angle of the drill 203a. Therefore, in the case where the cutting edge of the drill 203a is a single row, it is necessary to detect the reaction force acting around the axis of the drill 203a corresponding to the rotation angle of the drill 203a, for example, the load acting on the spindle motor 62. By detecting the resistance corresponding to the rotation angle of the drill 203a and further detecting the rotation angle A of the chisel edge when the load resistance is maximized, the deviation of the rotation center g of the drill 203a from the center G of the prepared hole 208 is detected. It is possible to find the direction.

Although it is possible to detect the rotational position H1 of the chisel edge where the load resistance is minimized to find the deviation direction of the rotation center g of the drill 203a with respect to the center G of the prepared hole 208, the deviation is considerably large. In such a case and when the tool radius R is very close to the radius r of the prepared hole, the rotational position where the chisel edge does not scrape the inner peripheral surface of the prepared hole 208 at all, that is, the load resistance is the minimum. Since there is a possibility that the rotation position will be continuously detected during one rotation,
It may be difficult to detect the rotational position where the load resistance is minimum. To dare to obtain the deviation direction of the center position from the rotational position where the load resistance is minimum, the rotational position H3 at which the minimum detection of the load resistance is started and the rotational position H2 at which the minimum detection of the load resistance is completed are obtained, and both are averaged. It may be necessary to treat the average rotation angle as the deviation direction. Needless to say, in the case of detecting the maximum value and obtaining the deviation direction and in the case of detecting the minimum value and obtaining the deviation direction, even if the deviation direction is the same, the direction is detected oppositely. It

Although a special example which can be applied only when the cutting edge of the drill 203a has one row has been described above, the most commonly used in actual machining is a drill having two cutting edges. 203a. If there are two cutting edges, the chisel edge of one cutting edge is 180 ° out of phase with the chisel edge of the other cutting edge when cutting the part with the most cutting It means that the cutting portion is being cut (relationship between H and H1 in FIG. 7), and similarly, when the chisel edge of one cutting blade is cutting the middle biting portion of the other cutting blade, The chisel edge of No. 2 also has a phenomenon of cutting the intermediate bite portion (relationship between H4 and H5 in FIG. 7). Therefore, as long as the reaction force acting on the drill 203a itself (load torque of the spindle motor 62) is viewed, the sum of reaction force moments around the axis of the drill 203a is irrespective of the rotation angle of the drill 203a, for example, as shown in FIG. In some cases, it becomes almost constant as in the example, and it becomes difficult to detect the deviation direction in the above-mentioned special example.

Therefore, in this embodiment, as described above, X
Observer 1 for axis and Y axis servomotors 50, 51
Loads Tdx2 and Tdy acting in the X and Y axial directions, which are the moving directions of the table 204, by providing 60x and 160y.
2 is detected and the load is combined to obtain the cutting force F. As a result, among the forces exerted by the drill 203a on the workpiece 207, deviations that do not form a pair with the rotation center g of the drill 203a as a reference are generated. Moment, that is, drill 203
A force generated by the one-side contact of a and capable of translating the workpiece 207 is detected, and the biting direction of the drill 203a, that is, the direction of the center deviation is detected.

Explaining this point, first, assuming that the drill 203a has two cutting blades, as described above, the chisel edge of one cutting blade and the chisel edge of the other cutting blade are H4 in FIG. And H5 at the rotational position, the chisel edges on both sides have the same biting amount, so that on the work piece 207, the forces having the same magnitude but opposite directions act at the points H4 and H5. . However, this is just a couple acting on the work piece 207. The work piece 207 that receives these forces tries to rotate about the rotation center g of the drill 203a, but in reality, the work piece 207 is fixed to the table 204 and does not rotate. As a result, these forces are transmitted to the table 204. The table 204 is a guide rail that restricts the movement of the table 204 only in the X-axis and Y-axis directions and their combined directions, that is, in the translational movement direction. Since it is made non-rotatable by the fixing element, the couple does not rotate and the couple acting around g is absorbed by the drag force from the fixing element such as the guide rail. in short,
At this time, the force acting on the table 204 is just the mass point g.
It is only a couple acting around, and has no directionality with respect to the X axis and the Y axis. That is, theoretically, no load acts on the X-axis servo motor 50 that supports the table 204 along the X-axis direction and on the Y-axis servo motor 51 that supports the table 204 along the Y-axis direction. It will be.

On the other hand, the table 20 is centered around g.
4 is not a force or couple acting but a deviation in magnitude, for example, when the chisel edge of one cutting blade and the chisel edge of the other cutting blade are located at the rotational positions H and H1 in FIG. Then, the situation is different from the above. As described above, at the H point, the bite of one chisel edge is the strongest and the bite of the other chisel edge is the shallowest, so that the force acting on the point H on the workpiece 207 and the H
Although the direction is completely opposite to the force acting on one point,
There will be a considerable difference in their magnitude, and these forces cannot be couples. Needless to say, in this case, the force acting on the point H on the work piece 207 is much larger than the force acting on the point H1. In the example shown in FIG. 7, at the point H1, the other chisel edge of the drill 203a is not in contact with the inner peripheral surface of the prepared hole 208.
The force acting on the point is zero. As a result, this state is equivalent to the force being applied in the tangential direction of the drill 203a only at the point H on the work piece 207 when viewed from the work piece 207 side. As an example, the special example in which the other chisel edge of the drill 203a does not contact the inner peripheral surface of the prepared hole 208 at the H1 point has been described, but the other chisel edge of the drill 203a at the H1 point does not contact the inner peripheral surface of the prepared hole 208. Even if the chisel edge located on the H point side and the other chisel edge located on the H1 point side are in contact with each other as long as there is a difference in the bite amount, the forces acting on the H point and the H1 point A force capable of translational motion is applied to the work piece 207 according to the difference (in the example of FIG. 7, one chisel edge is located at H4 and the other chisel edge is located at H5, and one chisel edge is located at H5). All are included in this category except at H5 and the other chisel edge at H4).

Thus, the rotation center g of the drill 203a
The rotational moments that are biased toward both sides are all forces that translate the work piece 207, that is, the force that moves the table 204 to which the work piece 207 is fixed in the X-axis or Y-axis direction or in the combined direction thereof. And its size F
Can be obtained by combining load torques acting on the X-axis servo motor 50 that supports the table 204 along the X-axis direction and the Y-axis servo motor 51 that supports the table 204 along the Y-axis direction. . Needless to say,
This force F is the force given to the work piece 207 about g by the chisel edge of one cutting blade of the drill 203a and the force given to the work piece 207 about g by the chisel edge of the other cutting blade. Is larger, that is, the bite amount of one chisel edge is larger than the bite amount of the other chisel edge, the larger the difference is. In other words, one of the drills 203a has a maximum load torque F (hereinafter referred to as cutting force) obtained by combining the load torques Tdx2 and Tdy2 acting on the X-axis servo motor 50 and the Y-axis servo motor 51, respectively. Since there are two rotation positions, that is, the cutting blade, the cutting force becomes maximum during one rotation of the main shaft. The drill 2 with respect to the center G of the prepared hole 208 is obtained by obtaining the rotation angle A of the chisel edge when one of them is the maximum.
Of the rotation center g of 03a (H and H1 in the example of FIG. 7).
It is possible to obtain the direction that connects with).

Although the above description is for the case where the cutting edge has two threads, the shift direction of the rotation center g of the drill 203a is obtained in the same manner as above even when the cutting edge has one thread. You can If there is only one cutting edge, the force applied to the work piece 207 by the other chisel edge is eliminated, and the cutting force F obtained by combining the load torques Tdx2 and Tdy2 is obtained by the single chisel edge being the work piece 207. It becomes the same as the cutting resistance when rushing into and squeezing a part of it to separate it. Since this value varies in proportion to the amount of biting of the chisel edge with respect to the inner peripheral surface of the prepared hole 208, the cutting force F obtained by combining the load torques Tdx2 and Tdy2 of the X axis and the Y axis is the maximum. Rotation angle A of chisel etch when it becomes
As described above, the center G of the prepared hole 208 is obtained by
The shift direction of the rotation center g of the drill 203a with respect to can be obtained. In the case of the jig grinder, the rotating grindstone can be regarded as a single-edged chisel edge, and the revolution movement of the grindstone can be regarded as the rotation of the drill.

In FIG. 2, the deviation direction of the rotation center g of the drill 203a with respect to the center G of the prepared hole 208 is automatically obtained in the initial stage at the time of starting the secondary processing based on such a principle. 9 is a flowchart showing an outline of the processing of one embodiment in which the deviation of the center position is automatically corrected by sending the table 204 based on the table.
This control is performed by the processor 11 of the numerical controller 10.
The required program is stored in the ROM 12 in advance. Assuming that the descending operation of the machining head 202 and the rotational driving of the drill 203a by the spindle motor 62 have already started, and the chisel edge located at the tip of the drill 203a has already begun to contact the upper end surface of the workpiece 207. The processing of this embodiment will be described with reference to FIG.

The processor 11 which started this processing stands by until the spindle 1 rotation signal from the above-mentioned fixed position detector is detected (step a1), and when the spindle 1 rotation signal is detected, first, The spindle rotational speed S commanded at the present time, that is, the rotational speed S of the drill 203a is read (step a2), the reciprocal thereof is taken to obtain the time 1 / S required for one rotation of the drill 203a, and further this is determined as the spindle. Dividing by the sampling cycle T of the rotational position to obtain the number of times N the spindle rotational position is sampled per revolution of the drill 203a, a data file for storing N data is developed in the RAM 13 (step a3).

Thereafter, until the next spindle 1 rotation signal is detected, the processor 11 repeats the servo motors 50 for the X and Y axes at every predetermined sampling period T at that time.
The present values of the load torques Tdx2 and Tdy2 acting on 51 are read from the RAM 13, the values are combined each time to obtain the magnitude of the cutting force F, and the values are sequentially stored in the above-mentioned data file ( Step a4).
The magnitude of the cutting force F acting on the XY plane of the table 204 can be calculated by squaring each of the load torques Tdx2 and Tdy2, obtaining the sum of them, and taking the square root. It is not necessary to know the magnitude of F itself, and it is only necessary to know the spindle rotation angle when the cutting force F reaches its maximum. Therefore, it is not necessary to take the square root, and the value can be obtained when the sum of squares is obtained. There is no problem even if is stored as the cutting force F.

Then, when it is confirmed that the sampling process of the cutting force F corresponding to one revolution of the drill 203a is completed by detecting the next one revolution signal of the spindle (step a).
5) The processor 11 obtains one address m (the smaller address in this embodiment) of the two addresses where the magnitude of the cutting force F has the maximum value from the above-mentioned data file, and the value Fm of the maximum value. Is temporarily stored (step a6), the 1 rotation angle 2π of the drill 203a is multiplied by m / N, and the cutting force F is determined with reference to the predetermined position of the spindle 1 rotation signal.
The rotation angle B of the drill 203a when the maximum value is obtained is obtained (step a7).

Further, the processor 11 moves the drill 203a to a predetermined rotation position corresponding to the output position of the spindle 1 rotation signal.
Chisel edge and table 204 when one is positioned
The angle G (fixed value determined by the mounting state of the drill 203a) formed by the X-axis of No. 1 is added to the above-mentioned angle B, and the rotation angle A of one chisel edge when the cutting force F becomes maximum is determined by the table 204. The coordinate system is used as a reference (step a8). This angle A is as shown in FIG.
This is exactly the direction in which the center of rotation g of the drill 203a deviates from the center G of the prepared hole 208. However, at this stage, although the deviation direction of the rotation center g can be known from the angle A, it is not obvious which side of the chisel edge of the cutting edge bites in the drill 203a having two cutting edges, and the rotation center g I do not know the direction of the deviation. For example, even if the direction of displacement of the center g of the drill 203a with respect to the center G of the prepared hole 208 is actually in the state shown in FIG. 7, the rotation angle A of the chisel edge when the cutting force F becomes maximum is obtained. Is detected as A = A and A = A +
It is similar to the possibility of being detected as π.

Next, the processor 11 multiplies the preset positional deviation allowable value L by the respective values of cosA and sinA to obtain the above-mentioned deviation direction A (however, the detected value A on the left side in each of the above expressions is the detected value A). (Not showing the true biting position as shown in FIG. 7), the elements Xc and Yc when the vector is decomposed in each axial direction are obtained (step a9), and the maximum value Fm of the cutting force detected this time is the maximum cutting. Force memory register M
It is determined whether it is smaller than the current value of AX (step a10). Since the maximum cutting force storage register MAX is preset with a presettable maximum value, the determination result of step a10 executed first is inevitably true, and the processor 11 causes the cutting force detected in this processing to be The maximum of F
m is updated and stored in the maximum cutting force storage register MAX (step a11), and the X-axis and Y-axis servo motors 50,
A register Sg for storing the sign (+1 or -1) in the movement amounts Xc and Yc obtained in step a9 in 51 (initially set to either one, but in this embodiment, +1).
Are assumed to have been initially set)
g * Xc and Sg * Yc are output, the table 204 is moved in the displacement direction A by the allowable value L, and a correction operation for one processing cycle is performed (step a12). Needless to say, the magnitude of the combined movement amount by the movement commands Sg.Xc and Sg.Yc is exactly the same as the positional deviation allowable value L. As a result, when the displacement direction of the drill 203a is detected in the opposite direction, that is, when the displacement is detected as A = A + π, the drill 203a is moved in the direction for eliminating the displacement, and the displacement of the drill 203a is detected. When the orientation is detected in the correct orientation, that is, when A = A is detected, the drill 203a is moved in such a direction as to further bite into the workpiece 207, but the allowable value L is sufficient. Since it is set to a small value, for example, drill 203
Even if a is moved in such a direction as to bite into the workpiece 207, there is substantially no adverse effect on the machining accuracy unless such an operation is repeatedly executed.

When the next spindle 1 rotation signal is detected, the processor 11 repeatedly executes the same processing as described above to obtain the deviation direction A of the rotation center g of the drill 203a with respect to the center G of the prepared hole 208, The movement amounts Xc and Yc are calculated (above, step a1 to step a9), and the newly detected maximum value Fm of the cutting force is stored in the maximum cutting force storage register MAX.
Is smaller than the current value of (step a1
0). Here, if the newly detected maximum value Fm of the cutting force is smaller than the current value of the maximum cutting force storage register MAX, that is, the maximum value of the cutting force detected in the previous processing, the drill 203a in the previous processing cycle is performed. Is moved in the direction of eliminating the positional deviation, and if the newly detected maximum value Fm of the cutting force is larger than the maximum value of the cutting force detected in the previous processing, This means that the drill 203a has been moved in the direction of increasing the positional deviation in the previous processing cycle. Therefore, the processor 11 inverts the code register Sg only when the determination result of step a10 is false, that is, when the direction of sending the table 204 in the previous processing cycle is incorrect (step a13). The same processing as described above will be repeatedly executed.

As a result, the table 204 is prepared in the prepared hole 208.
After the processing is performed several times by gradually moving the drill 203a in the direction in which the deviation of the rotation center g of the drill 203a with respect to the center G is eliminated by the step width of the allowable value L in each processing cycle, The deviation of the rotation center g of the drill 203a with respect to the center G of 208 is automatically corrected to such an extent that it does not matter.

In this embodiment, each time the maximum value Fm of the cutting force is newly detected, the above-mentioned processing is repeatedly executed and the allowable value L is fed to the table 204. Therefore, the center of rotation of the drill 203a is rotated. Although the drill 203a vibrates within a certain allowable range L even after the deviation of g is substantially corrected, the feed of the table 204 is stopped when the value of the register MAX becomes equal to or less than the set value. By doing so, it is possible to eliminate useless vibration generated in the drill 203a. As described above, the cutting force F is the drill 20
It is the value of the translational force applied to the table 204 only when the bite amount of one chisel edge is larger than the bite amount of the other chisel edge, not the rotational moment acting on 3a. In the case of having a blade, regardless of the hardness of the work piece 207 or the tool diameter of the drill 203a, theoretically it is zero when the center g of the drill 203a and the center G of the prepared hole 208 completely match. Become. Therefore, the comparison value (setting value) with the register MAX for stopping the feeding of the table 204 does not necessarily need to be determined in consideration of the hardness of the work piece 207 and the tool diameter of the drill 203a, and is set as a constant value close to zero. It is also possible to close it. However, in reality, when the difference between the maximum value and the minimum value of the cutting force is within a predetermined range, the movement of the table is stopped. In this case, after step a6 in FIG. 2, one of the cutting force minimum values is obtained, and if the difference between the obtained maximum value and the minimum value is greater than or equal to a predetermined value, the processing from step a7 is performed. If it is smaller than the predetermined value, a process may be added to set a flag and not execute this process.

On the other hand, when the drill 203a has only one cutting edge, the center g of the drill 203a is the prepared hole 20.
Even if it completely coincides with the center G of 8, the table 204 is cut by the cutting action of the chisel edge provided only on one side.
Since a translational force always acts on the cutting force, the maximum value Fm of the cutting force does not substantially approach zero. Therefore, in this case, when the maximum value Fm and the minimum value of the cutting force in one rotation are detected and the difference is within a certain range, that is, the cutting that acts on the table 204 regardless of the rotational position of the drill 203a. The feed of the table 204 is stopped when the force F (translational force) becomes substantially constant. Since the translational force acting on the table 204 is related to the hardness of the work piece 207 and the tool diameter of the drill 203a, it is naturally necessary to determine the certain range accordingly. Further, in the above-mentioned embodiment, the value of the allowable value L is fixed by setting and the movement amounts Xc and Yc of the table 204 are obtained.
The value of L may be proportionally changed according to the maximum value Fm of cutting force (in the case of two rows) or the difference between Fm and the minimum value (in the case of one row).

[0058]

According to the hole position copying machining method of the present invention, the cutting force acting on the rotary tool during hole making is detected in correspondence with the rotary position of the rotary tool, and the cutting force becomes maximum or minimum. By detecting the rotating position of the rotating tool, it is possible to detect the uneven contact of the rotating tool, and the rotating tool can be applied to the work piece in a direction in which the fluctuation of the cutting force becomes smaller in the direction of the rotating position of the rotating tool where the cutting force becomes maximum or minimum. By moving the rotating tool relative to each other so that the center of the rotating tool coincides with the center of the prepared hole, there is some deviation between the center of the prepared hole and the center of rotation of the rotating tool. In some cases, even if the machining is started as it is, the rotary tool, the workpiece, and the machine tool are not adversely affected, and the hole having a normal shape can be drilled at the predetermined position defined by the prepared hole.

Further, the load of the motor of each axis for relatively moving the rotary tool and the workpiece is detected in the plane orthogonal to the rotary axis of the rotary tool, and the loads are combined to obtain the cutting force. Therefore, of the forces that the rotating tool gives to the work piece, only the translational force generated by the one-sided contact of the rotating tool can be accurately detected. Even in the case of a drill having two cutting edges, which is difficult to specify, it is possible to accurately detect the one-sided contact of the tool and surely match the center of the prepared hole with the center of rotation of the rotary tool. .

Furthermore, since the relative feed of the tool can be automatically stopped at the stage when the difference between the maximum and the minimum of the cutting force becomes equal to or less than the set value, the tool axis of the tool axis due to a minute load change after the completion of the positioning can be achieved. Vibration can also be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main part of a machine tool of an embodiment to which the present invention is applied.

FIG. 2 is a flowchart showing an outline of a process performed by a numerical control device of a machine tool for automatically correcting a deviation of a center position.

FIG. 3 is a functional block diagram showing a configuration of an observer for each axis of the machine tool.

FIG. 4 is a flowchart showing an outline of processing by an observer.

FIG. 5 is a diagram schematically showing an example of a machine tool used for hole making.

FIG. 6 is a schematic view showing an outline of secondary processing with a drill.

FIG. 7 is a diagram illustrating the operation principle of the embodiment.

[Explanation of symbols]

 10 Numerical Control Device 11 Processor 30-32 Axis Control Circuit 50-52 Servo Motor 62 Spindle Motor 63 Position Coder 160x Observer 200 Machine Tool 203 Rotating Tool 203a Drill 204 Table 207 Workpiece 208 Pilot Hole

Claims (4)

[Claims] 1. In hole drilling for expanding the hole diameter by cutting the inner circumference of a prepared hole previously formed in a workpiece with a rotary tool, a cutting force acting on the rotary tool during the hole drilling is applied. The rotation position of the rotary tool is detected corresponding to the rotation position of the rotary tool to obtain the maximum or minimum cutting force, and the fluctuation of the cutting force decreases in the direction of the rotation position of the maximum or minimum rotation tool. In the same direction, the hole position copying is performed so that the center of the prepared hole and the center of rotation of the rotary tool coincide with each other by moving the rotary tool relative to the workpiece in a plane orthogonal to the rotation axis of the rotary tool. Processing method. 2. The hole position copying machining method according to claim 1, wherein the rotary tool is automatically relatively moved by a set amount in a direction in which the variation of the cutting force is reduced for each rotation of the rotary tool. 3. Among the motors of the respective axes for relatively moving the rotary tool and the workpiece, at least each of the axes for relatively moving the rotary tool and the workpiece within a plane orthogonal to the rotary axis of the rotary tool. The hole position copying machining method according to claim 1 or 2, wherein the load of the motor is obtained, and the loads are combined to obtain the cutting force. 4. In hole drilling for expanding the hole diameter by cutting the inner circumference of a prepared hole previously formed in a workpiece with a rotary tool, the cutting force acting on the rotary tool during the hole drilling is applied. Every rotation of the rotary tool is detected until the rotary position of the rotary tool at which the cutting force becomes maximum and minimum is detected corresponding to the rotary position of the rotary tool, and the difference between the maximum and minimum becomes equal to or less than a set value. A hole position copying machining method in which a rotary tool is automatically moved relative to a workpiece in a direction in which the fluctuation of the cutting force is reduced by a set amount or an amount proportional to the difference.