JPH03161238A - Nc cutting device - Google Patents

Abstract

PURPOSE:To automatically adjust a tool feeding speed corresponding to sudden variation of load on a cutting tool by modifying the tool feeding speed indicated by numerical control data according to an override quantity computed with an override computing device, and relatively moving the cutting tool at this modified tool feed speed. CONSTITUTION:Cutting load of a cutting tool 20 is detected with respective motor load sensors of X-axis, Y-axis, X-axis, and main spindle 41-44. Next, an override quantity corresponding to the tool cutting load detected with these load sensors 41-44 is computed with an override computing device 32. According to the override quantity, a tool feed speed indicated by numerical control data is modified with a NC computing device 30 to automatically deal with sudden variation of cutting load.

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 ball end mill attached to a spindle at the required speed in the X, Y, 2nd direction (multi-axis direction) relative to the workpiece, according to the NC data stored in advance. While sequentially moving the amount,
The rotational speed of the spindle is controlled to form the desired shape. The tool feed speeds in the x, y, and z directions and the rotational speed of the spindle are set to optimal values in consideration of tool breakage, reduction of cutting time, 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 material to be cut is not fully understood, the tool feed rate is constantly adjusted to the optimum value to prevent tool breakage. NC that prevents accidents and shortens processing time
The purpose is to provide a cutting device.

(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. There is provided an NC cutting device characterized in that the speed is corrected and the cutting tool is relatively moved at the corrected cutting speed.

(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.

(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, the general structure of the NC die carving machine 1 will be shown with reference to FIG. 1. A table 10 of the NC die carving machine 1 has a workpiece W mounted thereon and is movable in the X-axis direction by an X-axis motor (servo motor) 11. A cross beam l4 spans the left and right columns 12, and this cross beam l4 is movable in the vertical direction (Z-axis direction) perpendicular to the X-axis direction by a Z-axis motor (servo motor) 15. Ru. A spindle head l6 is attached to the cross beam l4, and this spindle head l6 is driven by a Y-axis motor (servo motor) 17 in the longitudinal direction of the cross beam l4, that is, in a direction perpendicular to the X-axis and the Z-axis (Y-axis direction). can be moved along.

A main shaft (not shown) rotatably driven by a main shaft motor 18 is rotatably supported in the main shaft head l6 in the Z-axis direction, and a cutter (pole 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 die carving machine 1 is controlled by the NC control device 30, the aforementioned speed control device 32, the input device 34, and the 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 41, 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 4l to 4 mentioned above
Based on the load of each motor detected by 4, the tool feed rate of the cutter 20 is overridden so that it reaches the target speed (in this case, the feed rate 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 unit 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 an operation key (not shown) on the surface of the manual operation panel 39, and this is switched to the manual operation panel 39 side. The signal is supplied to the NC calculation unit 30a via the selected changeover switch 38. 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 unit 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 drive amount of 17.18 is calculated, and a control signal corresponding to the calculated drive 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.

Procedure for generating an override amount by the speed control device Next, a procedure for automatically generating an override amount by the speed control device 32 will be explained with reference to FIGS. 28 to 2G.

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 312, where an operating condition input routine is executed, and 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 of the sensors, step S15 is executed and the process returns to step S12.

In step S15 described above, the override amount KOR is
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. Note that 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 amount of override! If the value exceeds 00%, it means that the feed rate is corrected to that value and accelerated.

If there is input from the load sensor, step S16
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, etc. 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 S18).

This determination is made based on whether the AE signal read in step Sl6 is greater than a predetermined threshold.

In step Sl8, if the AE signal is not detected, the process advances to step S20, and the cutting flag CFL is set to the value l.
Determine whether or not. This cutting flag CFL is a program control variable for remembering that cutting was performed in the previous loop, and if this cutting flag CFL is the value l, it is reset to the value O (step S22) and the register is It is cleared (step S24), and the process returns to step S12 via the aforementioned step 315. On the other hand, if the cutting flag CFL is not the value l, then step S
The process returns to step S12 via step S15.

Since the cutting plate was almost Δ91 ri, cutting was not done in the previous loop, and AE was not performed in this loop.
If a signal is detected to indicate that cutting has started,
That is, if the AE signal is detected in step 518, the process advances to step S26.

The start of cutting may be detected at the start of machining, or at the time when intermittent cutting is repeated and the workpiece transitions from a non-cutting section to a cutting section.

In step 326, it is determined based on the AE signal 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 E 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, override amount 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.
The corrected value (VTLXKOR÷100) multiplied by
(See the period between 11 and 11).

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 startup amount HX (%) required to return to
Calculate and store this.

HX=100-KOR (A
1) Then, in steps 33B and 338, a deceleration flag DFL and a cutting flag CFL, which will be described later, are set to the value l, and the process returns to step S12.

When normal cutting of the workpiece W is started, the above-mentioned step S12. S18, S26, etc. are executed sequentially, and step S
The determination result in step 30 is now positive, and the subsequent steps 840 to S49 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 S50, 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 352 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 the tool cutting load TA is set to a predetermined reference value Xst.
It is determined whether or not it is smaller than that. If the result of this determination is affirmative, it is determined whether the deceleration flag DFL described above is the value 1 (step 856). This flag DFL 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. The recovery process is executed.

Incidentally, if the deceleration flag DFL is not set to the value 1, the determination result in step S56 is negative, and the process proceeds to step S.
Proceeding to 70, 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 858, 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 l, 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; Even if the cutting load TA is less 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 steps described below will be performed. The return processing after S84 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 884 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 886 is executed.

FIG. 5 shows a flowchart of the lO% start-up processing routine. First, the count value N counted by the down counter is
Determine whether tlP is 0 (step 3860
). 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 O. This is a timer that measures the time (see (b)).

Immediately after the cutting start deceleration processing routine is executed, this 10
When the % startup processing routine is executed, the count value NtlP of the down counter should be 0, and the determination result in step 8860 is affirmative, and step 886
Go to 1.

In step 3861, the previously set override amount K
A first predetermined value ΔKl (for example, 10%) is added to OH, and this added value is converted to a new override amount KOR (=KO
R+ΔKl). Then, the above formula (At
) to calculate startup ilHX (step S862).
, sets the down counter and ends the routine (step S863).

This routine is repeatedly executed as long as the return process is executed and the determination result in step S85 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. 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 rise amount HX becomes equal to or less than the predetermined value X}IX, the determination result in step S85 becomes negative, and the process proceeds to step S87, where a 20% rise processing routine is executed this time.

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 0 (step 3870)
. 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. If the count value NtJP is not 0, the routine ends without changing the override amount KOrl and the start-up amount HX. However, when the predetermined time TUP elapses and the count value NUP becomes O, Each step after the next step S871 is executed every time the time TOP elapses.

In step S871, the previously set override amount K
A second predetermined value ΔK2 (for example, 20%), which is set to a value larger than the above-mentioned l-th predetermined value ΔK l (IOX), 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 100%, and if it is less than 100%, the process directly proceeds to step $874, but if it is greater than 100%, the override amount KOR is set to 100%. Try again (Step S)
873), the process proceeds to step S874. That is, this 20%
In the startup processing routine, the override amount KOR 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 8875, the 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 KQR 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
(between time t2 and time t3 in Figure (b)).

When the start-up amount HX reaches 0, in step 384,
If the determination result is affirmative, the process proceeds to step 38B, 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 section 30a after checking the upper limit value and lower limit value in steps S90 and 391, 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 addition, in the return process shown in FIG. 2E, the start-up amount}{X
After reaching the predetermined value When HX reaches a predetermined value XHX, the override amount KOR may be raised to 100% at once.

As long as cutting is started and no cutting abnormality is detected by the AE sensor 40 (if no abnormality signal is detected according to the determination result in step S26), as will be described later, the cut-off amount KOR is set according to the tool cutting load, The tool feed rate is controlled by modifying the tool feed rate set by the NC data with 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, in steps S40 to S43 in FIG. 2B, the speed control device 32 calculates the current values AS,
Sample and import AX, AZ, AYIN.

Next, in steps S44 to S46, reference motor conversion processing is performed on the current value AYIN of the Y-axis motor l7. 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 1l and the Y-axis motor 17 and the feed speed VF in a no-load state (non-cutting state), and as is clear from the figure, The current ratio (AX/AV) is approximately 7 times to 40 times. In addition, FIG. 8 shows that the feed speed VF of the X-axis motor 11 and Y-axis motor 17 is 700 mm/min, respectively.
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 lO and spindle head l6, 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 the 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, 20A. 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 l7 is calculated using the following equation (B1). .

AY=AYIN+XK1...
・(Bl) 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 S46, where the reference converted current value AY of the Y-axis motor 17 is calculated using the following equation (B2).

AY = AYIN XK l =-...-
(B2) Here, Kl is a correction coefficient, for example, the value 1
．． Set to 4. FIG. 9 shows the relationship between the reference converted current value AY converted as described above and the actual current value AY[N.

In this way, when the conversion of the current value necessary for the reference current value conversion is completed, the process advances to step S47, and the current value of each axis mork obtained in the current loop is added to the total sum TA of the current values calculated in the previous loop. The current value TA is calculated by the following equation (B3).

TA=TA+AS+AX+AY+AZ ・・・・・・
(B3) The process then proceeds to step 348 in FIG. 2C, where it is determined whether the number of sampling times N1 has reached a predetermined value XNI. If it has not been reached, the number of sampling times Nl
After adding the value l to (step S49), step 31
Return to step 2 and repeat the detection of the current value of each axis motor. Then, when the number of sampling times Nl reaches the predetermined value XNI, the sum of the XNl sampling values of each axis motor added as described above is stored as the tool cutting load TA, and the process proceeds to step 350 described above.

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

In step S52, the speed control device @32 sets 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 X s t and the reference value X s t 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
Corresponds to the area surrounded by 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 Fig. 10, rather than comparing the detected current value for each sampling with the reference value. So,
The influence of disturbances and detection errors can be minimized.

If the determination result in step 352 is affirmative, that is, the tool cutting load TA is greater than the predetermined reference value Xst, step S6
0, and 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 1 in step S62, 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 larger than 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 S
Proceed to step 91, this time compare it with the lower limit value MIN, 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 KOH.

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 896, 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 l, 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 3603, where the override amount KORn set in step S601 of the current loop and the previous NC are calculated.
Override amount KORn-1 output to the calculation unit 30a
The deviation Δk is calculated.

Δk = KORn − KORn−1 ・
...{CI) Next, check whether this deviation Δk is a negative value, that is, the override amount set this time K ORn
It is determined whether or not the override amount KORn-1 is smaller than the override amount KORn-1 outputted to the NC calculation unit 30a last time. If the determination result is positive, that is, if a tool cutting load TA larger than the previous one is detected, the override amount KOR set in step S601 is NC without being changed.
It will be output to the calculation section 30a.

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

When the count value NUP of the down counter reaches O,
The determination result in step $606 is positive, 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 of the return process described above, and if the result of this determination is affirmative. If so, proceed to step S609,
The above-mentioned deviation Δk is equal to the above-mentioned lth predetermined value ΔKl (10%
). That is, it is determined whether the difference between the previous and current override amounts KOR is greater than a predetermined value ΔKl, and if it is, the previous N
Override amount KORn-1 output to C calculation unit 30a
The predetermined value ΔK1 is added to the above-mentioned predetermined value ΔK1, and this is set as the override amount KOR in the current loop (step S610). Then, the process advances to step 3616, 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 or equal to the predetermined value ΔK1, the process proceeds to step 8616 without making any change to the override amount KOR calculated in step S601.

That is, when the tool feed rate should be increased with respect to the override amount KOR 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.

In step 8608, if the determination result 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 3614).

On the other hand, if the determination result in step 3612 is negative, that is, the deviation Δk is less than or equal to the predetermined value ΔK2, the process proceeds to step S616 without changing the override amount KOH calculated in step S601.

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 KOR, the load applied to the tool is reduced. Even if the position of is raised to a position corresponding to the predetermined value XX}I 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 KOH output to the NC calculation section 30a.
An example of a change in is shown below. In FIG. 13A, t 10, t
11. At each point in time t12, an increase in the tool cutting load TA occurs 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. and the tool feed speed is reduced. Then, when a decrease in the tool cutting load TA is detected at time tla, 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 t13 to time 4).

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 amount KOR gradually increases due to a decrease in the tool cutting load TA at time t21. Then, at time t22, the tool cutting load T
A rapidly increases and is rapidly reduced to an override amount KOR corresponding to the magnitude of the load.

At point 123, the load is reduced again and the override amount K
OR gradually increases from that point, but since the start-up amount HX reaches the predetermined value XHX at t24, the override amount K
From that point on, the amount of increase in OH is gradually increased by a second predetermined amount ΔK2.

When the tool cutting load TA is larger than the reference value Xst, deceleration calculation processing is executed, and then when the tool cutting load TA becomes smaller than the above-mentioned reference value Xst, the tool feed rate is accelerated from the value specified by the NC data. However, if the start-up amount HX has not returned to 0% yet, the determination results in step S54 and step S56 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 O once and the deceleration flag DFL is reset to 0 in step 388, 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 O% yet, the step S described above is performed.
The determination results at step S52 and step S54 are both negative, and the determination result at step 358 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 deceleration flag DFL is reset to 0 in step 888, speed maintenance processing (step S80) 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. 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 weekly speed maintenance process is executed, the tool cutting load TA is equal to the reference value Xst. In this case, the override amount KOR is set to 100% and the tool feed speed is It will be held at the value specified by .

In step S26, when abnormal vibration or abnormal sound is detected by the AE sensor 40 during cutting, or in step S50, the tool cutting load TA reaches the cutting maximum value X.
If it is detected that it is greater than or equal to MAX, the process advances to step 327 in FIG. 2G, and an abnormality handling routine is executed. Various processing methods can be considered as the abnormality processing executed in this abnormality processing routine. 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%, Processes such as stopping the supply of shop air and cutting oil and issuing a warning to the operator are 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 32B), and it is determined whether a return signal is output from this specific key (step S29). Steps 828 and S29 are then repeatedly executed until this return signal is input. 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 10 of the NC die carving machine moved in the X-axis direction with respect to the cutting tool (cutter) 20.
The table 10 may be fixed and the cutting tool 20 may be moved relative to the table IO. 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 be moved.

(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. and an override calculation device that calculates the NC
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 relatively moves the cutting tool at this corrected tool feed rate, so that the cutting tool is Negative 4. The tool feed speed can be automatically adjusted in response to sudden changes in the load, reducing the burden of manual operations on the operator, preventing tool breakage accidents, and controlling the tool feed speed command value using numerical control data. can be set to a high value, resulting in various effects such as being able to significantly shorten the cutting time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall structure of the NC die-sinking machine according to the present invention, FIGS. 2A to 2G are flowcharts for explaining the procedure for generating the override amount KOR, and FIG. , 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 a flowchart 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. ! ...NC die engraver, IO...table, 1l...
X-axis motor, 12...Column, l4...Cross beam, l5...Z-axis motor, 1G...Spindle head, 1
7...Y-axis motor, l8... Main shaft motor, 20...
・Cutter (cutting tool) 30...NC calculation device, 30a
...NC calculation section, 30b... Serpo 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, 4l-44... Shaft motor load sensor. Fig. 1 Fig. 2D Fig. 2E [F] Fig. 2F VTL%KoR+lOO Fig. 6 Figure 118: Full volume K○R Figure 13A Figure 13B Examination

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. NC to do
cutting equipment.