JPH03161240A - Nc cutting device - Google Patents

Abstract

PURPOSE:To reduce operator's load of manual operation, previously prevent breakage trouble of a tool, and highly institute a tool feed speed command in numerical control data, by constituting the device so as to automatically adjust a tool feed speed corresponding to sudden variation of load applied on a cutting tool. CONSTITUTION:When an override quantity is instituted at a value to accelerate a tool feed speed after the override quantity is instituted at a value on the side to decelerate a tool feed speed from a prescribed standard value to maintain the tool feed speed indicated by numerical control data, namely, when the tool feed speed is varied on the side to incrase cutting load, the present value of override quantity is instituted so as to limit variation of the present value within a prescribed allowable variation with a NC computing device 30. Hereby, sudden variation of cutting load on a tool 20 due to unexpected variation of form of an object to be cutting worked W is previously prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an NC cutting device, and particularly to a cutting device that is suitably applied to an NC die-sinking machine and has an override function.

(Prior Art) For example, the outer panels of automobiles, such as door panels and fender panels, are press-formed, and this press-forming requires a press mold with a wide variety of shapes. For press molds, a casting mold is roughly machined using an NC die carving machine to give it a curved shape, and then detailed finishing is done based on the mold model.

Rough machining using an NC die-sinking machine is performed by moving a pole end mill attached to a spindle relative to the work in X, Y, etc. according to pre-stored NC data. While sequentially moving the required amount at the required speed in directions such as Z (multi-axis directions),
The rotational speed of the spindle is controlled to form the desired shape. The tool feed speed in the x, y, and z directions and the spindle rotation speed are set to optimal values in consideration of tool breakage, cutting time reduction, and the like.

(Problem to be solved by the invention) In rough machining using a conventional NC die-sinking machine, it is difficult to accurately grasp the external dimensions of each workpiece due to manufacturing errors during casting, and the external dimensions of the workpiece If the dimensions cannot be accurately determined and cutting is performed using the cutting conditions specified by numerical control data, the tool will deviate significantly from the optimum depth of cut and width of cut, placing a large load on the tool.
There were problems such as tool breakage accidents. Therefore,
At the start of cutting or at the initial stage of rough machining, the operator must manually adjust the feed rate and feed rate of the tool, which places a heavy burden on the operator and requires less experience and skill. It was necessary. Furthermore, in order to avoid a sudden change in the tool load due to a sudden change in shape, the feed rate of the tool cannot be set high, resulting in the problem that machining takes time.

The present invention was made to solve these problems, and even when the external shape of the workpiece is not fully known, the tool feed rate is always adjusted to the optimum value, and even when the external shape of the workpiece is not fully understood, An object of the present invention is to provide an NC cutting device that prevents tool breakage due to tool cutting loads and shortens machining time.

(Means for Solving the Problems) In order to achieve the above-mentioned object, according to the present invention, the cutting tool is moved against the workpiece based on the numerical control data read into the NC calculation device from the external data reading device. A load sensor that detects a cutting load of the cutting tool in an NC cutting device that relatively moves sequentially to required positions in multiple axis directions at a required speed to cut a workpiece into a required shape;
and an override calculation device that calculates an override amount according to the tool cutting load detected by the load sensor, and the NC calculation device calculates the tool feed specified by the numerical control data according to the override amount calculated by the override calculation device. The speed is corrected, and the cutting tool is relatively moved at the corrected tool feed rate, while the override amount is a side that decelerates the tool feed rate from a predetermined reference value that maintains the tool feed rate specified by the numerical control data. After the tool feed rate is set to a value that should be accelerated, the amount of change between the previous value and the current value of the override amount is compared with a predetermined allowable change amount, and the amount of change is determined as this predetermined allowable change amount. An NC cutting device is provided, characterized in that when the amount of change is exceeded, the current value of the override amount is set such that the amount of change in the current value is limited to the predetermined allowable amount of change.

(Function) The override calculation device constantly calculates the override amount for optimizing the tool feed rate according to the tool cutting load. By modifying the feed rate, it is possible to automatically cope with sudden changes in the tool cutting load. After the override amount is set to a value that decelerates the tool feed rate from a predetermined reference value that maintains the tool feed rate specified by the numerical control data, it is set to a value that should accelerate the tool feed rate. In other words, when changing the tool feed rate to the side where the tool cutting load increases, the current value of the override amount is set so that the amount of change in the current value is limited to the predetermined allowable change amount. This prevents sudden changes in the tool cutting load due to unexpected changes in the shape of the tool.

(Example) An example of the present invention will be described in detail below based on the drawings. Although the present invention is applicable to various NC cutting devices, in this embodiment, an example in which the present invention is applied to an NC die carving machine for rough machining a press die using a ball end mill will be described.

First, a schematic structure of the NC die carving machine 1 will be shown with reference to FIG. A table 10 of the NC die carving machine 1 mounts and fixes a work W, and is movable in the X-axis direction by an X-axis motor (servo motor) 11. A cross beam 14 spans the left and right columns 12, and this cross beam 14 is movable in the vertical direction (Z-axis direction) perpendicular to the X-axis direction by a Z-axis motor (servo motor) 15. cross beam l
4 is attached with a spindle head l6, and this spindle head l6 is driven by a Y-axis motor (servo motor) 17 along the longitudinal direction of the cross beam 14, that is, the direction perpendicular to the X-axis and the Z-axis (Y-axis direction). It is possible to move.

A main shaft (not shown) rotatably driven by a main shaft motor l8 is rotatably supported in the main shaft head l6 in the Z-axis direction, and a cutter (ball end mill) 20 is attached to the main shaft. An AE sensor 40 is attached near the cutter 20 on the lower end surface of the spindle head l6 to detect vibration noise generated when the cutter 20 cuts. The AE sensor 40 is electrically connected to a speed control device 32 (described later) via an input device 34, and supplies a detection signal to the speed control device 32.

The operation of the Hongsei-Yori-Kouo wide die carving machine 1 is controlled by an NC control device 30, the aforementioned speed control device 32, an input device 34, and an NC data reading device 3.
6. This is performed using the manual operation panel 39 or the like. On the input side of the input device 34, in addition to the above-mentioned AE sensor 40, there are an X-axis motor load sensor 4l, a Y-axis motor load sensor 42, and a Z-axis motor load sensor 43 that detect the load (current value) of each motor mentioned above. , and main shaft motor load sensors 44 are connected to each of the motors, and these load sensors supply load detection signals of each motor to the speed control device 32 via the input device 34. The input device 34 includes an amplifier circuit, a filter circuit, an A/D conversion circuit, and the like.

The NC data reading device 36 reads NC data (numerical control data) from the outside using an NC tape or the like, and reads the NC data from the outside.
NC calculation section 30a of C control device 30 and speed control device 3
Supply to 2. The output side of the speed control device 32 is connected to the calculation section 30a of the NC control device 30 via a changeover switch 38. The speed control device 32 has an override amount calculation program as described later, and this calculation program calculates the position/speed command value specified by the NC data, the tool diameter, the tool feed rate depending on the type of workpiece material, and Current data of each servo motor and the load sensors 41 to 4 mentioned above
Based on the load of each motor detected by 4, the tool feed speed of the cutter 20 is overridden so that it reaches the target speed (in this case, the feed speed in the x, y, and z axis directions and the rotation speed of the main shaft are included). Calculate the amount and send it to the NC calculation section 3.
Supply to 0a.

A manual operation panel 39 is connected to the ° input side of the changeover switch 38, and an override amount is set by operating operation keys (not shown) on the surface of the manual operation panel 39.
This is supplied to the NC calculation section 30a via the changeover switch 38 which is switched to the manual operation panel 39 side. The switching of the changeover switch 38 is normally performed by operating a specific key on the manual operation panel 39, and also by a switching command from the speed control device 32 or the NC calculation section 30a. The output side of the manual operation panel 39 is also connected to the speed control device 32, so that a work command signal inputted by the operator from the manual operation panel 39 can also be supplied to the speed control device 32.

As will be described in detail later, the NC calculation unit 30a calculates the moving position of the cutter 20, the tool feed speed specified by the NC data from the NC data reading device 36, and the override amount or manual operation output by the speed control device 32. Based on the override amount output by the panel 39, each axis motor 1
1, 1 5. The driving amount of 17.18 is calculated, and a control signal corresponding to the calculated driving amount is supplied to the servo motor drive control section 30b. The servo motor drive control unit 30b controls each axis motor 11, 15, 17, 18 according to the control signal.
to drive.

Generation of Override Amount by Speed Control Next, the procedure for automatically generating an override amount by the speed control device 32 will be explained with reference to FIGS. 28 to 26.

First, in step SIO, the speed control device 32
Initialization of memory values of various control variables, constants, etc.
initialization). These stored values include tool blade length, tool diameter, type of work material, current data for each axis motor, various discrimination values, and the like.

Also, registers are cleared in this step.

Next, the process advances to step 812, where an operating condition input routine is executed, and the operating conditions of the die engraving machine I are input from the NC data reading device 36. Then, it is determined whether there is an input signal from each load sensor (step S14), and if there is no input signal from any sensor, step Sl5 is executed and the process returns to step Sl2.

In step S15 described above, the override amount KOR is set to 1.
00% and outputs this to the NC calculation section 30a.

This override amount signal of 100% is sent to the NC calculation unit 30.
In a, it means that each motor is driven without making any correction to the tool feed speed VTL calculated by NC data. In addition, setting the override amount KOR to a value of 100% or less means that the feed speed VTL is set to the value (V
TLXKOR÷100'). For example, an override amount of 50% means deceleration to 50% of the feed speed specified by the NC data, and an override amount of 0% means that the feed speed is reduced to 0%, that is, stopped. On the other hand, the override amount is 100%
If the value exceeds , it means that the feed rate is corrected to that value and accelerated.

If there is input from a load sensor, step 816
Then, the AE signal input routine is executed and the AE signal from the AE sensor 40 is taken in.

In the AE signal input routine, the signal output from the AE sensor 40 is amplified, filtered, and so on. Then, the presence or absence of the AE signal is determined, that is, it is determined whether cutting by the cutter 20 has started (step 318).
. This determination is made based on whether or not the AE signal read in step Sl6 indicates a dog based on a predetermined threshold value.

If the AE signal is not detected in step 318, the process advances to step S20, and the cutting flag CFL is set to a value of 1.
Determine whether or not. This cutting flag CFL is a program control variable for remembering that cutting was performed in the previous loop, and when this cutting flag CFL has the value l, it is reset to the value 0 (step S22) and the register is It is cleared (step S24), and the process returns to step 312 via step 315 described above. On the other hand, if the cutting flag CFL is not the value l, then step S
The process returns to step Sl2 via l5.

There was no cutting in the previous loop, and there was no cutting in this loop.
If a signal is detected to indicate that cutting has started,
That is, if the AE signal is detected in step 31B, the process advances to step S26.

The start of cutting may be detected at the start of machining, or when intermittent cutting is repeated and the workpiece transitions from a non-cutting section to a cutting section.In step 326, the AE signal is detected. It is determined whether or not a tool abnormality has occurred. The AE sensor 40 can detect abnormal vibration signals and abnormal acoustic signals that occur when an abnormal load is applied to the tool or when the tool breaks.
If there is no abnormality in the signal, the process advances to step S30 in FIG. 2B.

In step S30, the cutting flag CFL is set (CF
L=1).

Since this determination is negative at the time of starting cutting (time "to" in FIG. 4), the process advances to step S32, and a cutting start deceleration processing routine is executed.

FIG. 3 shows a flowchart of the cutting start deceleration processing routine, in which the speed control device 32 sets the override amount KOR to a predetermined value Xin and outputs it to the NC calculation unit 30a (step S321). Then, the process advances to step S322, waits for the predetermined time Tin to elapse (see FIG. 4(b)), and ends the routine. In addition, the amount of opalide is KO
The NC calculation unit 30a that receives R inputs an override amount KO to the tool feed speed VTL set by the NC data command.
Multiply R and corrected value (VTLX KOI{+10
0 ) as a control signal, which is supplied to the drive control section 30b over a predetermined period Tin (see FIG. 4(b)).
)).

In this way, in the cutting start deceleration processing routine, the AE
0, when the cutter 20 comes into contact with the workpiece and the start of cutting is detected, the tool feed rate is once decelerated and held at that value for a predetermined period of time Tin.

Next, the process proceeds to step S34 in FIG. 2B, where the speed control device 32 changes the decelerated tool feed speed to the original command speed VTL.
The start-up ffiHX (%) required to return to
1) and store it.

HX = 1 0 0 - KOR -...
- (AI) Then, in steps 336 and 338, a deceleration flag DFL and a cutting flag CFL, which will be described later, are set to the value 1, and the process returns to step S12.

When normal cutting of the workpiece W is started, steps Sl2, Sl8.326, etc. described above are executed in sequence, and step S
The determination result in step S30 is now positive, and the subsequent steps S40-349 are sequentially executed, and the tool cutting load T
A is detected. Details of the method for detecting this tool cutting load TA will be described later. Then, in step S5Q, after confirming that no excessive load is applied to the cutter 20 by comparing the tool cutting load TA with a predetermined determination value XMAX, the process proceeds to step S52 in FIG. 2D.

In step S52, it is determined whether the tool cutting load TA is greater than a predetermined reference value Xst, and if the determination result is affirmative, a deceleration calculation process to be described later is executed. on the other hand,
If the determination result in step S52 is negative, the process proceeds to step S54, where it is determined whether the tool cutting load TA is less than a predetermined reference value Xs. If the result of this determination is affirmative, it is determined whether the deceleration flag DFL described above is 1 (step 356). This flag D
FL is set to the value l by executing the cutting start deceleration processing routine described above, and immediately after the cutting start deceleration processing is executed, this determination result becomes affirmative, and the process proceeds to step S84, which will be described later, to return after the deceleration processing. Processing is executed. Note that if the deceleration flag DFL is not set to the value l,
The determination result in step S56 is negative, and step S7
The process advances to 0, and an acceleration calculation processing routine to be described later is executed.

On the other hand, if the determination result in step S54 is negative, that is,
If the tool cutting load TA is equal to the predetermined reference value Xst and neither deceleration calculation processing nor acceleration calculation processing is performed, the process advances to step 358, and the deceleration flag DF is also set in this step.
It is determined whether L is the value l. Then, if the deceleration flag DFL is set to the value 1, step S
The process advances to step S84, where a return process after the deceleration process is executed, and if the value l has not been set, the process proceeds to step S80, where a speed maintenance process, which will be described later, is executed.

In this way, immediately after the cutting start deceleration processing routine is executed, if the tool cutting load TA is greater than the predetermined reference value Xst and the cutting speed should be reduced, this deceleration processing is given priority, but the tool cutting Even if the load TA is smaller than or equal to the predetermined reference value Xst and acceleration calculation processing or speed maintenance processing should be executed, these processing will be ignored by setting the deceleration flag DFL, and the process will be ignored in step S84, which will be described later. Subsequent return processing will be executed with priority.

Note that the deceleration flag DFL is set to the value l not only in the cutting start deceleration processing routine described above, but also immediately after the deceleration calculation processing routine described later is executed, and in such a case, it is also set to the value l in step S84, which will be described later. Then, the recovery process is executed.

In step S84 of the return process, it is determined whether the start-up amount HX is 0, that is, whether the override amount KOR set in the previous loop has already returned to 100%. Immediately after the cutting start deceleration process is executed (immediately after time 0 in FIG. 4), this start-up amount HX is not 0, so step S85 is executed, and the start-up amount HX is set to a predetermined value XHX (for example, 40%). It is determined whether or not it is larger than that. Immediately after the cutting start deceleration process is executed, this determination result should be affirmative, and the start-up process of step S86 is executed.

FIG. 5 shows a flowchart of the 10% start-up processing routine. First, the count value N counted by the down counter is
Determine whether upfJ<o (step S8
60). When this down counter is set or reset, the count value is returned to the initial value, and the count value is decremented at predetermined time intervals until the value becomes 0. This is a timer that measures the time (see (b)).

Immediately after the cutting start deceleration processing routine is executed, this lO
When the % startup processing routine is executed, the count value NUP of the down counter should be O, and the determination result in step 8860 is affirmative, and step 8861 is executed.
Proceed to.

In step 3861, the previously set override amount K
A first predetermined value ΔKl (for example, 10%) is added to OR, and this added value is used as a new override amount KOR (=KO
R+ΔKl). Then, the above formula (AI
) to calculate the rise amount HX (step S862),
Set the down counter and end the routine (
step 3863).

This routine is repeatedly executed as long as the return process is executed and the determination result in step 385 is affirmative. Then, the same override amount KOR is maintained until the determination result in step 8860 becomes affirmative, that is, until the down counter is set to the initial value and finishes counting down, and the predetermined time TUP has elapsed, and the predetermined time TOP has elapsed. Each time, the override amount KOR changes its value to a predetermined value Δ
Kl, and the start-up amount HX is increased to a predetermined value ΔKl.
(from time t1 to time t2 in FIG. 4(b)).

When the start-up amount HX becomes less than the predetermined value XHX, step S
The determination result of 85 is negative, and the process advances to step S87.
This time, the 20% startup processing routine is executed.

FIG. 6 shows a flowchart of the 20% start-up processing routine. First, the count value N counted by the down counter is
Determine whether UP is O (step S87
0). This down counter may be the same as that used in the above-mentioned 1O% startup processing routine, or another down counter whose initial value is set to a different value, that is, whose clock time is different, may be used. You may.

Then, if the count value NuP is not 0, the routine ends without changing the override amount KOR and the start-up amount HX. Each step after the next step 3871 is executed every time the time TUP elapses.

In step S871, the previously set override amount K
A second predetermined value ΔK2 (for example, 20%) that is set to a value larger than the first predetermined value ΔK 1 (IOX) described above is added to OR, and this added value is used as a new override amount KOR (= KOR+ΔK2). Then, it is determined whether the newly set override amount KOR is less than or equal to 100%, and if it is less than or equal to 100%, the process directly proceeds to step S874, but if it is greater than 100%, the override amount KOR is set to lOO%. Fix it (Step S)
8 7 3), the process advances to step S874. That is, in this 20% startup processing routine, the override amount K
OR is never set to a value greater than 100%.

Next, the rise amount HX is calculated using the above-mentioned formula (A) (step S874), and the process proceeds to step S875.

In step S875, a down counter is set to return the count value to the initial value, and the routine ends.

This 20% startup processing routine is repeatedly executed as long as the return processing is executed and the determination result in step S84 is positive, and each time the predetermined time TUP elapses, the override amount KOR transfers its value to the predetermined value ΔK2. At the same time, the start-up amount HX is decreased by a predetermined value ΔK2 (fourth
From time t2 in Figure (b) (3 time points).

The start-up amount HX reaches O, and in step S84,
If the determination result is affirmative, the process proceeds to step 388, where the deceleration flag DFL is reset to 0, and the return process ends.

Note that the override amount KOR set as described above is output to the NC calculation unit 30a after checking the upper limit value and lower limit value in steps S90 and S91, which will be described later. Since this is the same as the override amount control according to the tool cutting load, the details will be described later.

In this way, the tool feed rate is first decelerated at the start of cutting, and then gradually increased, so cutting can proceed smoothly at the start of cutting, and tool breakage accidents caused by sudden changes in tool load can be prevented. can be prevented. Furthermore, the tool feed rate can be automatically reduced, which was conventionally done manually by the operator at the start of cutting.

In the return process shown in FIG. 2E, after the start-up amount HX reaches the predetermined value XHx, the 20% start-up process is executed to gradually increase the override amount KOR to the second predetermined value ΔK2. , the invention is not limited to this example,
When the rise amount HX reaches the predetermined value XHX, the override amount KOR may be raised all at once to 100%.

As long as cutting is started and no cutting abnormality is detected by the AE sensor 40 (if no abnormal signal is detected according to the determination result in step 326), an override amount KOR is set according to the tool cutting load as described later, and the NC data is The tool feed rate is controlled by modifying the tool feed rate set by the override amount KOR. here,
A method for detecting tool cutting load will be explained.

According to the present invention, in order to minimize control errors due to disturbances, measurement errors, etc., the current value supplied to each axis motor is detected a predetermined number of sampling times XNI, and the sum of these is calculated. The magnitude of the tool cutting load is determined from More specifically, the speed control device 32 performs steps S40 to S. in FIG. 2B. In 43,
Current value AS detected by each axis motor load sensor 4l to 44
, AX, AZ. Sample and import AYIN.

Next, in steps S44 to S46, reference motor conversion processing is performed on the current value AYIN of the Y-axis motor 17. This conversion process is performed for the following reasons.

When each axis motor is driven in a no-load state, the current value supplied to each axis motor differs even though there is no load. FIG. 7 shows the relationship between each current value A supplied to the X-axis motor 11 and the Y-axis motor 17 and the feed rate VF in a no-load state (non-cutting state), and as is clear from the figure, The current ratio (AX/AY) is approximately 7 times to 40 times. In addition, FIG. 8 shows that the feed speed VF of the X-axis motor l1 and Y-axis motor l7 is each 700 mm/min.
This figure shows the relationship between the depth of cut and the current value A of each motor when cutting the workpiece material with the settings set to 1.2
It is about 1.4 times to 1.4 times. These differences in supply current values are due to sliding resistance of the table 10 and spindle head 16, differences in weight, differences in motor capacity, etc., and tool cutting in each axis direction is performed without taking these differences into account. It is not possible to calculate the load. Therefore, for shaft motors where the influence of the above-mentioned sliding resistance etc. cannot be ignored, it is attempted to accurately grasp the tool cutting load by converting it into a reference current value of the shaft motor.

In the embodiment, current detection conditions are made uniform by converting the actual current value AYIN of the Y-axis motor 17 into the current value of this reference motor using the X-axis motor 11 as the reference motor. Therefore, it is determined whether the actual current value AYIN of the Y-axis motor l7 is smaller than a predetermined determination value XAY (step S44). This discrimination value
Alternatively, it is set to a value that allows it to be determined whether cutting is in progress, for example, 2OA. If the actual current value AYIN is smaller than the predetermined determination value XAY, it is determined that idle cutting is in progress, and the process proceeds to step S45, where the reference converted current value AY of the Y-axis motor 17 is calculated by the following equation (Bl). .

AY=AYIN+XK1...
・(81) Here, XKI is a correction constant, for example,
It is set to 15A.

If the determination result in step S44 is negative, that is, the actual current value AY
If IN is larger than the predetermined determination value XAY, it is determined that cutting is in progress, and the process proceeds to step 846, where the standard converted current value AY of the Y-axis motor 17 is calculated using the following equation (B2).

AY = AYIN X K l -...
...(B2) Here, Kl is a correction coefficient, for example,
It is set to a value of 1.4. FIG. 9 shows the relationship between the reference current value AY converted as described above and the actual current value AYIN.

In this way, when the conversion of the current value required for standard current value conversion is completed, the process proceeds to step 347, where the current value of each axis motor obtained in the current loop is added to the total sum TA of the current values calculated in the previous loop. Then, the current value TA is calculated using the following equation (B3).

TA=TA+AS+AX+AY+AZ =・=- (B
3) The process then proceeds to step 848 in FIG. 2C, where it is determined whether the number of sampling times Nl has reached the predetermined value XNI. If the value has not been reached, the value l is added to the sampling number Nl (step S49), and then the process returns to step Sl2 to repeat detection of the current value of each axis motor. and,
When the number of sampling times Nl reaches the predetermined value XNI, the sum of the XNI sampling values of each axis motor added as described above is stored as the tool cutting load TA, and the process proceeds to step S50 described above.

Next, a description will be given of the deceleration calculation process executed according to the tool cutting load TA determined as described above.

In step 352, the speed control device 32 controls the tool cutting load TA obtained as described above to a predetermined reference value Xst.
Determine whether the value is greater than or not. This tool cutting load TA
The relationship between the reference value Xst and the reference value Xst is shown in FIG. The tool cutting load TA is a value obtained by summing the current values of the respective axis motors by sampling XNl times, and the area of the shaded portion in the figure corresponds to the tool cutting load TA. On the other hand, the reference value Xst is the value obtained by adding the reference current value Ast XNI times, and in the same figure, the reference value Xst is the value obtained by adding the reference current value Ast XNI times, and in the same figure,
Corresponds to the area surrounded by Ast-0. In this way, the tool cutting load TA is determined by comparing the size of the tool cutting load TA with the reference value by comparing the areas as shown in Figure 1O, rather than comparing the detected current value for each sampling with the reference value. Therefore, the influence of disturbances and detection errors can be minimized.

If the determination result in step S52 is affirmative, that is, if the tool cutting load TA is greater than the predetermined reference value X s t, the process proceeds to step 360, where a deceleration calculation processing routine is executed.

11A and 11B show a flowchart of this deceleration calculation processing routine, and the speed control device 32 first sets an override amount KOR according to the tool cutting load TA (step S601).

Figure 12 shows the tool cutting load TA and this tool cutting load TA.
The relationship between the override amount KOR and the override amount KOR that is set according to the tool cutting load TA is shown. , the value decreases as the tool cutting load TA increases, and is set to 0% when the tool cutting load TA reaches the maximum cutting value XMAX. here,
The reference value Xst is a value that sets the amount of cutting by the cutter 20 to a predetermined value and corresponds to the cutting load at this time. In addition, the maximum cutting value XMAX is the cutting load current value corresponding to the maximum allowable depth of cut when the depth of cut reaches the tool blade length, and by limiting the maximum value of the tool cutting load TA to this value, tool breakage can be prevented. is prevented. The relationship shown in Figure 12 is that the tool l
It is set to keep the removal amount per blade approximately constant,
As the depth of cut increases, the tool feed rate is set to be slower in inverse proportion to this.

At this time, it is preferable for the life of the tool to slow down the rotation speed of the spindle in proportion to the tool feed speed.

Next, the speed control device 32 determines whether the deceleration flag DFL is set to the value 1 or not. When this deceleration calculation processing routine is executed for the first time, this flag is normally not set, so the subsequent steps are skipped and the routine ends. That is, in this case, the override amount KOR is set as is to the value corresponding to the tool cutting load TA, and the routine ends.

When the deceleration calculation processing routine ends, the deceleration flag DFL is set to the value l in step 362, and then the start-up amount HX (=100-KOR
) is calculated by the above-mentioned formula (At).

Next, proceeding to step S90 in FIG. 2F, it is determined whether the override amount KOR is a dog based on the upper limit value MAX,
If it is large, the override amount KOR is set to this upper limit value MAX.
is reset and the process proceeds to step S96. On the other hand, if the override amount KOR is less than the upper limit value MAX, step 3
Proceed to step 91, this time compare it with the lower limit value MEN, and find the lower limit value MI.
If it is smaller than N, the lower limit value MIN is set again, and if it is greater than or equal to the lower limit value MIN, the process proceeds to step S96 without changing the override amount KOR.

In this embodiment, the lower limit value MIN is set to 0%, and the upper limit value M is set to 0%.
AX is set to 120%, for example, to prevent the feed rate from being controlled at a value outside the allowable range. Of course, these upper and lower limit values can be set to appropriate values depending on the performance of the die carving machine.

In step 396, the override amount KOR set as described above is output to the NC calculation section 30a, the feed speed of the cutter 20 specified by the NC data is decelerated and corrected by this override amount KOR, and the tool cutting load TA is reduced. Sudden changes will be dealt with.

In step S602 of the deceleration calculation processing routine, if the deceleration flag DFL is set to the value 1, that is,
When the deceleration calculation process was executed in the previous loop and the deceleration calculation process is continued in the current loop, the process advances to step S603, where the override amount KORn set in step S601 of the current loop and the previous NC are calculated.
Override amount KORn- outputted to the calculation unit 30a
Calculate the deviation Δk of 1.

Δk = KORn - KORn-1 =
-(CI) Then, whether this deviation Δk is a negative value or not,
That is, the override amount KORn set this time is the override amount KORn outputted to the NC calculation section 30a last time.
It is determined whether it is smaller than n-1. If the determination result is positive, that is, if a tool cutting load TA larger than the previous one is detected, the overwrite amount KOR set in step S601 is output to the NC calculation unit 30a without being changed. It turns out.

On the other hand, if the determination result in step S604 is negative, the first
Proceeding to step 8606 in Figure 1B, it is determined whether the count value NUP counted by the down counter is 0 or not.

This down counter may be the same as that used in the above-described 10% startup processing routine, or may be another down counter whose initial value is set to a different value. If the count value NtJP is not 0, the override amount KOR is calculated by the previous NC calculation unit 30.
The same value KORn-1 as the value outputted to a is set (step 3607), and the deceleration calculation processing routine ends. Then, as long as the override amount KOR calculated in step S601 is greater than or equal to the value output to the NC calculation unit 30a last time, the count value NUP of the down counter described above is 0.
Step S607 is repeatedly executed until the override amount KOR is maintained at a constant value.

When the count value NIP of the down counter reaches 0,
The determination result in step 8606 is affirmative, and step 8
Proceed to 608. The start-up amount HX is the predetermined value XHX (40%)
It is determined whether or not it is larger than that.

This determination is the same as the determination in the restoration process described above, and if the determination result is affirmative, the process advances to step S609, and the aforementioned deviation Δk is equal to the aforementioned first predetermined value ΔKl (to%).
Determine whether the value is greater than or not. That is, it is determined whether the difference between the previous and current override amounts KO[l is larger than a predetermined value ΔKl, and if it is, the previous override amount KOR calculated in step S601 is not used as it is, and
Override amount KORn-1 output to C calculation unit 30a
The predetermined value ΔKl is added to the above-mentioned predetermined value ΔKl, and this is set as the override amount KOR in the current loop (step S610). Then, the process advances to step S616, which will be described later.

On the other hand, in step $609, if the determination result is negative, that is, the deviation Δk is less than the predetermined value ΔK1, the process proceeds to step 3616 without making any change to the override amount KOR calculated in step 3601.

That is, when the tool feed rate should be increased with respect to the override amount KOH calculated in step S601 of FIG. 11A, a predetermined value is added every time a predetermined time elapses to gradually increase the tool feed rate.

If the determination result in step 8608 is negative, that is, if the rise amount HX is smaller than the predetermined value
is larger than a predetermined value ΔK 2 (20X). That is, it is determined whether the difference between the previous and current override amounts KOH is larger than a predetermined value ΔK2, and if it is larger,
Override amount KOR calculated in step S601
Instead of directly using , the predetermined value ΔK2 is added to the override amount KORn-1 outputted to the NC calculation unit 30a last time, and this is used as the override amount KOR (=
KORn-1+ΔK2) (step 8614).

On the other hand, if the determination result in step S612 is negative, that is, the deviation Δk is less than or equal to the predetermined value ΔK2, the process proceeds to step 8616 without making any change to the override amount KOH calculated in step 3601.

In this way, when the start-up amount HX becomes equal to or less than the predetermined value XHX, the tool feed rate is accelerated until the reference cutting load is reached, and the cutting time is shortened.

Incidentally, when the rising amount HX reaches the predetermined value XHX, the override amount KOR may be suddenly raised to 100%. As mentioned above, the tool feed rate is proportional to the depth of cut of the tool, and due to the implementation of deceleration calculation processing, the cutting load was applied only to the vicinity of the cutting edge of the tool, but due to the increase in the override amount KOH, the load applied to the tool is Even if the position rises to a position corresponding to the predetermined value XXH and the depth of cut is increased all at once, there is no risk of tool breakage.

13A and 13B show the cutting depth of the cutter 20 and the override amount KOR output to the NC calculation section 30a.
An example of a change in is shown below. In FIG. 13A, t 10, t
11 and t12, the tool cutting load TA increases due to a sudden change in the depth of cut, and the override amount KOR is set to a value corresponding to the tool cutting load TA at the time when a change in the tool cutting load TA is detected. is set to reduce the tool feed rate. Then, when a decrease in the tool cutting load TA is detected at point [13], the override amount KOR
is not increased all at once to a value corresponding to the tool cutting load TA, but is gradually increased to a predetermined value ΔKl every time a predetermined time TUP (for example, lsec) elapses (from time tla to [14 time points)].

In this way, tool breakage is prevented by immediately reducing the tool feed rate in response to a sudden increase in load, and gradually increasing it in response to a sudden decrease in load.

In Fig. 13B, after the tool cutting load TA increases due to a sudden change in the tool depth of cut at time t20, the override ffil<O
R is gradually increasing. Then, at time t22, the tool cutting load TA increases rapidly again, and is rapidly reduced to an override amount KOH corresponding to the magnitude of the load.

At time t23, the load is reduced again and the override amount K
OR gradually increases from that point on, but since the start-up amount HX reaches the predetermined value XIIX at the time point 124, the amount of increase in the override amount KOH is gradually increased by the second predetermined amount ΔK2 from that point.

When the tool cutting load TA is smaller than the reference value Xst, deceleration calculation processing is executed, and then when the tool cutting load TA becomes smaller than the reference value XSt mentioned above, the tool feed rate is accelerated from the value specified by the NC data. However, if the start-up amount HX has not yet returned to 0%, the determination results in step S54 and step 356 described above will be affirmative.
The acceleration calculation process is ignored, and the previously described return process shown in FIG. 2E is executed. Then, after the rise amount HX returns to 0 once and the deceleration flag DFL is reset to 0 in step S88, the acceleration calculation process (step S70) is executed.

Further, when the tool cutting load TA is larger than the reference value Xst, deceleration calculation processing is executed, and then the tool cutting load TA becomes the reference value
When it becomes equal to st, the tool feed rate should be held at the value specified by the NC data, but the start-up amount HX
has not returned to 0% yet, step S described above
The determination results in step S52 and step S54 are both negative, and the determination result in step 35B is affirmative, so the speed maintenance process is ignored and the above-described return process shown in FIG. 2E is executed. Then, the start-up amount HX returns to 0,
After the speed flag DFL is reset to 0 in step 388, speed maintenance processing (step $80) is executed.

When the acceleration calculation process is executed, the tool cutting load TA is smaller than the reference value Xst, and the tool feed rate is accelerated to shorten the cutting time. In this case, the speed control device 32
In step S70, the target override amount KOR corresponding to the tool cutting load TA is calculated from the table shown in FIG. 12. In this case, the value read from the table may be directly output to the NC calculation unit 30a, or the value actually output may be gradually increased until the target override amount is reached. Note that the override amount KOR set in the acceleration calculation process is checked after the upper and lower limit values are checked (step 390 to step S94), which will be described later.
, are output to the NC calculation section 30a.

When the maze bottom maintenance and speed maintenance processing is executed, the tool cutting load TA is equal to the reference value Xst, and in this case, the override amount KOR is set to 100% and the tool feed rate is It will be held at the specified value.

In step S26, if abnormal vibration or abnormal sound is detected by the AE sensor 40 during cutting, or in step S50, the tool cutting load TA is set to the maximum cutting value X.
If it is detected that it is greater than or equal to MAX, the process advances to step S27 in FIG. 2G, and an abnormality handling routine is executed.

The abnormality processing executed by this abnormality processing routine is as follows:
Various processing methods can be considered. For example, the automatic operation of the NC processing unit is stopped, the rotation of the main shaft is stopped, the override amount KOR is set to 0%, the supply of shop air and cutting oil is stopped, and the operator Processing such as issuing a warning is executed.

After the abnormality processing described above is completed, the speed control device 32
The signal level of a specific key on the manual operation panel 39 is input (step 828), and it is determined whether a return signal is output from this specific key (step S29). Steps S28 and S29 are then repeatedly executed until this return signal is input manually. That is, the speed control device 32
After the above-mentioned abnormality occurs, the system waits until the operator completes the abnormality processing.

When the operator completes abnormal processing such as replacing the cutter and a return signal is input, the speed control device 32
Returning to step SIO in Fig. A, the stored values are initialized again and the control of the tool feed rate, etc. described above is restarted.

In the above embodiment, the table lO of the NC die carving machine moved in the X-axis direction with respect to the cutting tool (cutter) 20.
The table IO may be fixed and the cutting tool 20 may be moved relative to the table 10. That is,
The present invention corrects the relative movement speed between the cutting tool and the workpiece by an override amount, and either the cutting tool or the workpiece may move.

(Effects of the Invention) As explained in detail above, according to the NC cutting device of the present invention, the load sensor detects the cutting load of the cutting tool, and the override amount is determined according to the tool cutting load detected by the load sensor. It is equipped with an override calculation device that calculates
The calculation device corrects the tool feed rate specified by the numerical control data according to the override amount calculated by the override calculation device, and moves the cutting tool relatively at the corrected tool feed rate. is set to a value that decelerates the tool feedrate from the specified reference value that maintains the specified tool feedrate, and then is set to a value that should accelerate the tool feedrate, the previous value and current value of the override amount The amount of change in the value is compared with a predetermined allowable change amount, and if the amount of change exceeds the predetermined allowable change amount, the current value of the override amount is limited to the predetermined allowable change amount. Since the setting is made as follows, the tool feed rate can be automatically adjusted in response to sudden changes in the load applied to the cutting tool, reducing the manual operation burden on the operator and reducing the risk of tool breakage. In addition to being able to prevent this from occurring, the tool feed rate command value can be set to a high value in the numerical control data, and the cutting time can be significantly shortened.

[Brief explanation of the drawing]

Fig. 3 is a block diagram showing the overall configuration of the NC die carving machine according to the present invention, Figs. 2A to 2G are flowcharts for explaining the procedure for generating the override amount KOR, and Fig. 3 is a , a flowchart of the cutting start deceleration processing routine, Fig. 4 is a timing chart showing the relationship between the workpiece external shape and tool feed rate, Fig. 5 is a flowchart of the lO% startup processing routine, and Fig. 6 is a 20% Flowchart of the startup processing routine. Figure 7 is a graph showing the relationship between tool feed rate VF and shaft motor load (current value A). Figure 8 is a graph showing the relationship between depth of cut and shaft motor load (current value A). 9 is a graph showing the relationship between the actual current value of the Y-axis motor and the reference converted current value.
11A and 11B are flowcharts of the deceleration calculation processing routine, and FIG. 13A and 13B are timing charts each showing an example of the relationship between the tool depth of cut and the override amount KOR. be. l...NC die engraver, lO...table, 1l...
X-axis motor, 12... Column, l4... Cross beam, 15... Z-axis motor, 16... Spindle head, l
7...Y-axis motor, l8... Main shaft motor, 20...
・Cutter (cutting tool) 30...NC calculation device, 30a
...NC calculation section, 30b... Servo motor drive control section, 32... Speed control device (override calculation device)
, 36... NC data reading device, 38... Changeover switch, 39... Manual operation panel, 40... AE sensor, 41-44... Shaft motor load sensor.

Claims (1)

[Claims] Based on the numerical control data read into the NC processing device from the external data reading device, the cutting tool is sequentially moved to the required positions in multiple axes directions at the required speed relative to the workpiece. An NC cutting device that cuts a workpiece into a required shape, comprising a load sensor that detects the cutting load of the cutting tool, and an override calculation device that calculates an override amount according to the tool cutting load detected by the load sensor. , the NC calculation device corrects the tool feed rate designated by the numerical control data according to the override amount calculated by the override calculation device, and relatively moves the cutting tool at the corrected tool feed rate, while adjusting the override amount. is set to a value that decelerates the tool feedrate from a predetermined reference value that maintains the tool feedrate specified by the numerical control data, and then is set to a value that should accelerate the tool feedrate, the override amount The amount of change between the previous value and the current value is compared with a predetermined allowable change amount, and when the amount of change exceeds the predetermined allowable change amount, the current value of the override amount is set as
An NC cutting device characterized in that the amount of change in the current value is set to be limited to the predetermined allowable amount of change.