JPH0794103B2 - NC cutting device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an NC cutting device, and more particularly to a cutting device that is suitably applied to an NC die cutter or the like and has an override function.

(Prior Art) For example, an outer panel such as an automobile door panel or a fender panel is press-worked, and this press-working requires a press die that is rich in shape change. For the press die, the NC die engraving machine is used to rough-process the casting die, and after the curved shape is given, the details are finished based on the die model.

Roughing with an NC die engraving machine requires a ball end mill mounted on a spindle in the X, Y, Z, etc. direction (multi-axis direction) relative to the workpiece at the required speed in accordance with the stored NC data. While being sequentially moved by the amount, the rotational speed of the spindle is controlled to form the desired shape. Then, the tool feed speed in the X, Y, and Z directions and the rotation speed of the spindle are set to optimum values in consideration of tool breakage, shortening of cutting time, and the like.

(Problems to be solved by the invention) In the rough machining by the conventional NC die engraving machine, it is difficult to accurately grasp the outer dimensions of each work due to the manufacturing error at the time of casting. If the dimensions cannot be grasped accurately and cutting is performed under the cutting conditions specified by the numerical control data, the tool will be greatly deviated from the preset optimum depth and width of cut and a heavy load will be applied to the tool, resulting in a tool breakage accident. There was a problem such as. Therefore, at the start of cutting in rough machining and at the initial stage of rough machining,
It is necessary for the operator to manually adjust the feed amount and feed rate of the tool, which imposes a heavy burden on the operator and requires the experience and skill of the operator. Further, in order to avoid a sudden change in the tool load due to a sudden change in shape, it is not possible to set the tool feed speed to a large value, and there is a problem that machining takes time.

The present invention has been made to solve such a problem, and accurately detects the cutting load of the cutting tool and feeds the tool even when the outer shape of the work material is not sufficiently grasped. It is an object of the present invention to provide an NC cutting device that constantly adjusts the speed to an optimum value to prevent tool breakage accidents, thereby shortening the machining time.

(Means for Solving the Problems) According to the present invention in order to achieve the above-mentioned object, a cutting tool is provided for an object to be cut based on numerical control data read from an external data reading device into an NC computing device. Relatively
Sequentially move to the required position in the multi-axis direction at the required speed,
In the NC cutting device that cuts the work piece into the required shape,
A plurality of drive motors that move the cutting tool in multiple axis directions including rotation, and a load that detects the cutting load of the cutting tool from the sum of at least two or more current loads of the plurality of drive motors. A sensor and an override computing device that computes an override amount according to the tool cutting load detected by the load sensor, wherein the NC computing device specifies the numerical control data according to the override amount computed by the override computing device. There is provided an NC cutting device, characterized in that the tool feed speed to be corrected is corrected, and the cutting tool is relatively moved at the corrected tool feed speed.

Preferably, a reference motor is defined, a current load detected from at least one of the plurality of drive motors is converted into a current load of the reference motor, and the sum of the current loads is added using the converted current load. Is desirable.

(Operation) The override computing device constantly computes the overwrite amount for tool feed speed optimization according to the tool cutting load, and the NC computing device specifies numerical control data according to the override amount. By modifying the tool feed rate, it becomes possible to automatically cope with sudden changes in the tool cutting load. At this time, the load sensor detects the cutting load of the cutting tool from the sum of at least two current loads of the plurality of drive motors, and the disturbance is determined by calculating the cutting load from the current load of each drive motor. Is eliminated, which is advantageous in terms of detection accuracy.

Embodiment An embodiment of the present invention will be described in detail below with reference to the drawings. Note that the present invention can be applied to various NC cutting devices, but in this embodiment, an example will be described in which the present invention is applied to an NC die engraving machine that rough-processes a press die by a ball end mill.

Structure of NC type engraving machine First, referring to FIG. 1, a schematic structure of the NC type engraving machine 1 is shown.
On the table 10 of the NC type engraving machine 1, the work W is placed and fixed, and X
The axis motor (servo motor) 11 can move in the X-axis direction. A cross beam 14 is bridged between the left and right columns 12, and the cross beam 14 can be moved by a Z-axis motor (servo motor) 15 in a vertical direction (Z-axis direction) orthogonal to the X-axis direction. Spindle head for cross beam 14
16 is attached to the main spindle head 16 by a Y-axis motor (servo motor) 17 in the longitudinal direction of the cross beam 14,
That is, it can move along a direction (Y-axis direction) orthogonal to the X-axis and the Z-axis.

A spindle (not shown) rotatably driven by a spindle motor 18 is rotatably supported on the spindle head 16 in the Z-axis direction.
A cutter (ball end mill) 20 is attached to the spindle. Then, in the vicinity of the cutter 20 on the lower end surface of the spindle head 16, an AE for detecting a driving sound generated when the cutter 20 is cut
The sensor 40 is attached. 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.

Configuration of Control Device The operation control of the die-cutting machine 1 is performed by the NC control device 30, the speed control device 32, the input device 34, the NC data reading device 36, the manual operation panel 39 and the like. On the input side of the input device 34, in addition to the AE sensor 40 described above, 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 described above. , Spindle motor load sensors 44 are connected to the spindle motor load sensors 44, and these load sensors supply load detection signals of the respective motors to the speed control device 32 via the input device 34. The input device 34 is composed of 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 uses this to read the NC control device.
It is supplied to the NC calculation unit 30a of 30 and the speed control device 32. The output side of the speed control device 32 is connected to the calculation unit 30a of the NC control device 30 via a changeover switch 38. Speed controller 32
Has a program for calculating the amount of override, as will be described later. With this calculation program, the position / speed command values specified by NC data, the tool diameter, the tool feed speed depending on the type of work material, and the servo motor From the current data and the load of each motor detected by the load sensors 41 to 44 described above,
The tool feed speed of the cutter 20 is the target speed (in this case, X, Y,
(The feed rate in the Z-axis direction and the rotation speed of the spindle are included.)
Supply to 30a.

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 panel of the manual operation panel 39, and this is switched to the manual operation panel 39 side. It is supplied to the NC calculation unit 30a via the selected changeover switch 38. The changeover switch 38 is normally changed over by a specific key operation on the manual operation panel 39, and also by a changeover command from the speed control device 32 or the NC calculation unit 30a. Further, the output side of the manual operation panel 39 is also connected to the speed control device 32, and a work command signal input by the operator from the manual operation panel 39 can also be supplied to the speed control device 32.

As will be described later in detail, the NC calculation unit 30a is configured to specify the moving position of the cutter 20, the tool feed speed, and the override amount or manual operation output by the speed control device 32, which is designated by the NC data from the NC data reading device 36. The drive amount of each axis motor 11, 15, 17, 18 is calculated based on the overwrite amount output from the panel 39, and a control signal corresponding to the calculated drive amount is supplied to the servo motor drive control unit 30b. The servo motor drive control unit 30b drives the respective axis motors 11, 15, 17, 18 according to the control signal.

Procedure for Generating Override Amount by Speed Controller Next, a procedure for automatically generating an override amount by the speed controller 32 will be described with reference to FIGS. 2A to 2G.

The speed control device 32 first initializes stored values of various control variables, constants, etc. in step S10. These stored values include the tool blade length, the tool diameter, the type of work material, the current data of each axis motor, various discriminant values, and the like. Also, the register is cleared at this step.

Next, in step S12, the operating condition input routine is executed and the operating conditions of the die-cutting machine 1 are input from the NC data reading device 36. Then, it is determined whether or not there is an input signal from each load sensor (step S14), and if there is no input signal from any sensor, step S15 is executed and the process returns to step S12. In step S15 described above, the overwrite amount KOR is set to 100.
%, And outputs this to the NC calculation unit 30a. The signal of 100% of the override amount means that each motor is driven without any correction to the tool feed speed VTL calculated by the NC data in the NC calculation unit 30a. It should be noted that if the override amount KOR is set to a value of 100% or less, the feed speed VTL is set to the feed speed VTL by the override amount K
It means to decelerate after correcting to a value (VTL x KOR / 100) that is multiplied by OR. For example, 50% override amount
Decelerates to 50% of the feed speed specified by the NC data, and when the override amount is 0%, the feed speed is 0%, that is,
It means to stop. Conversely, the amount of override is 10
If the value exceeds 0%, it means that the feed rate is corrected to that value to accelerate.

If there is an input from the load sensor, the process proceeds to step S16, the AE signal input routine is executed, and the AE signal from the AE sensor 40 is fetched. In the AE signal input routine, the signal output from the AE sensor 40 is amplified and filtered. Then, the presence or absence of the AE signal is determined, that is, the cutter
Determine whether cutting by 20 has started (step
S18). This determination is made based on whether or not the AE signal read in step S16 is larger than a predetermined threshold value.

When the AE signal is not detected in step S18, the process proceeds to step S20, and it is determined whether or not the cutting flag CFL has the value 1. This cutting flag CFL is a program control variable for storing that the cutting was performed in the previous loop, and when this cutting flag CFL is the value 1, it is reset to the value 0 (step S22) and the register is set. After clearing (step S24), the process returns to step S12 via the above-mentioned step S15. On the other hand, when the cutting flag CFL is not 1, the process directly returns to step S12 via step S15.

Control at the start of cutting If cutting is not performed in the previous loop and it is detected that the AE signal is detected in this loop to start cutting, that is, if the AE signal is detected in step S18, Proceed to S26. This cutting start may be detected at the beginning of machining, and intermittent cutting is repeated.
In some cases, it may be at the time when the non-cutting part of the workpiece is changed to the cutting part.

In step S26, it is determined whether or not a tool abnormality has occurred based on the AE signal. The AE sensor 40 can detect an abnormal vibration signal or an abnormal acoustic signal generated when an abnormal load is applied to the tool or the tool is broken, and if there is no abnormality in the AE signal, the step of FIG. 2B is performed. Proceed to S30.

In step S30, the cutting flag CFL is set (CFL = 1)
Is determined. At the start of cutting (see Fig. 4
Since this determination is negative at (t0), step S32
Then, the cutting start deceleration processing routine is executed.

FIG. 3 shows a flowchart of a cutting start deceleration processing routine. 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, in step S322, a predetermined time Tin
Wait for the progress of (see FIG. 4 (b)), and the routine ends. Note that the NC calculation unit 30 that has input the override amount KOR
a is the tool feed speed VTL set by the NC data command
Is multiplied by the overwrite amount KOR and the corrected value (VTL x K
OR ÷ 100) is used as a control signal and is supplied to the drive control unit 30b for a predetermined period Tin (see the period from time t0 to time t1 in FIG. 4B).

In this way, in the cutting start deceleration processing routine, when the cutter 20 contacts the work by the AE 40 and detects the start of cutting, the tool feed speed is once decelerated and held at that value for a predetermined period Tin.

Next, proceeding to step S34 in FIG. 2B, the speed control device 32
Calculates the start-up amount HX (%) required to return the decelerated tool feed speed to the original command speed VTL by the following equation (A1) and stores it.

HX = 100-KOR (A1) Then, in steps S36 and S38, the deceleration flag DFL and the cutting flag CFL, which will be described later, are set to the value 1, and the process returns to step S12.

When the normal cutting of the work W is started, the above-mentioned steps
S12, S18, S26, etc. are sequentially executed, and the determination result in step S30 is affirmative this time, and the subsequent steps S40 to S49.
Are sequentially executed, and the tool cutting load TA is detected. Details of the method for detecting the tool cutting load TA will be described later. Then, in step S50, the tool cutting load TA is compared with the predetermined determination value XMAX to confirm that the cutter 20 is not subjected to an excessive load, and then the process proceeds to step S52 in FIG. 2D.

In step S52, the tool cutting load TA is a predetermined reference value Xst.
It is determined whether or not it is larger, and if the determination result is affirmative, deceleration calculation processing described later is executed. On the other hand, if the determination result in step S52 is negative, the process proceeds to step S54, and it is determined whether or not the tool cutting load TA is smaller than a predetermined reference value Xst. Then, if the determination result is affirmative, it is determined whether or not the deceleration flag DFL is 1 (step S56). This flag DFL is set to a value of 1 by executing the cutting start deceleration processing routine described above, and the determination result is affirmative immediately after the cutting start deceleration processing is executed, the process proceeds to step S84 described later, and after the deceleration processing. The restoration process of is executed. If the deceleration flag DFL is not set to the value 1, the determination result of step S56 is negative, the process proceeds to step S70, and the acceleration calculation processing routine described below 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 is neither deceleration calculation processing nor acceleration calculation processing, step S58
And the deceleration flag DFL has the value 1 also in this step.
Is determined. Then, if the deceleration flag DFL is set to the value 1, the process proceeds to step S84 to execute the recovery process after the deceleration process, and if it is not set to the value 1, the process proceeds to step S80 to maintain the speed to be described later. The process is executed.

As described above, immediately after the cutting start deceleration processing routine is executed, when the tool cutting load TA is larger than the predetermined reference value Xst and the cutting speed is to be decelerated, this deceleration processing is prioritized. The load TA is smaller than the predetermined reference value Xst,
Even if the acceleration calculation processing or the speed maintenance processing is to be executed, these points are ignored by setting the deceleration flag DFL, and step S84 described later will be performed.
Subsequent recovery processing will be executed with priority.

The deceleration flag DFL is set to the value 1 immediately after the deceleration calculation processing routine described below is executed in addition to the above-described cutting start deceleration processing routine. Then, the return processing is executed.

In step S84 of the return processing, it is determined whether or not the startup maximum HX is 0, that is, whether or not the override amount KOR set in the previous loop has already returned to 100%. Immediately after the cutting start deceleration processing is executed (immediately after the time t0 in FIG. 4), since the startup amount HX is not 0, step S85 is executed and the startup amount HX is the predetermined value XHX (for example, 40%). It is determined whether or not it is larger. 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% startup processing routine. First, the count value NUP counted by the down counter.
It is determined whether is 0 (step S860). When the down counter is set or reset, the count value is returned to the initial value, and the count value is decremented every predetermined time until the value becomes 0, and the down time TUP (FIG. 4). (See (b)). Immediately after the cutting start deceleration processing routine is executed,
When the 10% start-up processing routine is executed, the count value NUP of the down counter should be 0, the determination result of step S860 is affirmative, and the process proceeds to step S861.

In step S861, the first predetermined value ΔK1 (for example, 10%) is added to the previously set override amount KOR, and this added value is stored as a new override value KOR (= KOR + ΔK1). Then, the startup amount H is calculated by the above equation (A1).
X is calculated (step S862), the down counter is set, and the routine is finished (step S863).

In this routine, the return process is executed
As long as the determination result of S85 is affirmative, it is repeatedly executed.
Then, until the determination result of step S860 becomes affirmative, that is, until the down counter is set to the initial value, the countdown is completed, and the predetermined time TUP elapses, the same override amount KOR is held and the predetermined time TUP elapses. Every time the override amount KOR is increased, the value thereof is increased to the predetermined value ΔK1 and the rise amount HX is decreased to the predetermined value ΔK1 (from time t1 to time t2 in FIG. 4B).

When the startup amount HX becomes equal to or less than the predetermined value XHX, the determination result of step S85 becomes negative, the process proceeds to step S87, and this time 20
% Startup processing routine is executed.

FIG. 6 shows a flowchart of the 20% start-up processing routine. First, the count value NUP counted by the down counter.
It is determined whether is 0 (step S870). This down counter may use the same down counter used in the 10% startup processing routine described above, or the initial value may be set to a different value, that is, another down counter with a different clock time may be used. You may. If the count value NUP is not 0, the routine is terminated without changing the override amount KOR and the startup amount HX.
When the count value NUP becomes 0 after the lapse of a predetermined time TUP,
That is, each step after the next step S871 is executed every time the predetermined time TUP elapses.

In step S871, the previously set override amount KOR
Is added with a second predetermined value ΔK2 (for example, 20%) which is set to a value larger than the first predetermined value ΔK1 (10%), and this added value is added to a new override amount KOR (= KOR).
It is stored as + ΔK2). Then, it is determined whether or not the newly set override amount KOR is 100% or less. If it is below, the process directly proceeds to step S874, but if it is larger than 100%, the override amount KOR is set to 100%. (Step S873) and proceed 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 start-up amount HX is calculated by the above equation (A) (step S874), and the process proceeds to step S875.

In step S875, the down counter is set, the count value is returned to the initial value, and the routine is finished.

In this 20% startup processing routine, the recovery processing is executed,
It is repeatedly executed as long as the determination result of the above-described step S84 is affirmative, and every time the predetermined time TUP elapses, the override amount KOR increases its value to the predetermined value ΔK2 and the rising amount HX decreases to the predetermined value ΔK2. (T2 in Fig. 4 (b)
From time t3).

When the startup amount HX reaches 0 and the determination result is affirmative in step S84, the process proceeds to step S88, and the deceleration flag D
FL is reset to 0 and the restoration process is completed. The override amount KOR set as described above is output to the NC calculation unit 30a after the upper limit value and the lower limit value are checked in steps S90 and S91, which will be described later. Since it 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 speed is once reduced at the start of cutting and then gradually increased, so that the cutting can be advanced smoothly at the start of cutting, and a tool breakage accident due to a sudden change in the tool load can occur. Can be prevented. In addition, it is possible to automatically reduce the tool feed speed, which was conventionally performed by the operator by manual operation at the start of cutting.

In the return process shown in FIG. 2E, after the startup amount HX reaches the predetermined value XHX, the 20% startup process is executed to gradually increase the override amount KOR to the second predetermined value ΔK2. The present invention is not limited to this embodiment, and the startup amount H
When X reaches the predetermined value XHX, the override amount KOR is set to 1
You may start up to 00% at once.

As long as cutting is started and no cutting abnormality is detected by the AE sensor 40 (when no abnormality signal is detected by the determination result of step S26), the override amount KOR according to the tool cutting load is set and NC data is set as described later. The tool feed rate is controlled by correcting the tool feed rate set by the above with the override amount KOR. Here, a method for detecting the tool cutting load will be described.

According to the present invention, in order to minimize control mistakes due to disturbances, measurement errors, etc., the current value supplied to each axis motor is detected a predetermined number of sampling times XN1 and the sum of these values is calculated. From this, the magnitude of the tool cutting load is determined. More specifically, the speed control device 32 is
In steps S40 to S43 in FIG. 2B, the current values AS, AX, AZ, AYIN detected by the respective axis motor load sensors 41 to 44 are sampled and fetched.

Next, in steps S44 to S46, the Y-axis motor 17
The reference motor conversion process is performed on the current value AYIN. The reason for performing this conversion process is as follows. When each axis motor is driven in a no-load state, the value of the current supplied to each axis motor differs even though there is no load. FIG. 7 shows the X-axis motor 11 in the unloaded state (non-cutting state).
Also, the relationship between each current value A supplied to the Y-axis motor 17 and the feed speed VF is shown. As is clear from the figure, the current ratio (AX / AY) is approximately 7 to 40 times. Further, FIG. 8 shows the relationship between the depth of cut and the current value A of each motor when the feed rate VF of the X-axis motor 11 and the Y-axis motor 17 is set to 700 mm / min and the workpiece is cut. As is clear from the figure, the current ratio (AX /
AY) is about 1.2 to 1.4 times. The difference in these supplied current values is due to the sliding resistance of the table 10 and the spindle head 16, the difference in weight, the difference in motor capacity, etc., and the tool cutting in each axial direction without taking these differences into consideration. It is not possible to calculate the load. Therefore, with respect to the above-described shaft motor in which the influence of the sliding resistance and the like cannot be ignored, the tool cutting load is accurately grasped by converting the current value of the reference shaft motor. As the reference shaft motor, one of the above-mentioned shaft motors 11, 15, 17, 18 may be selected and used as the reference motor, or the virtual shaft motor may be used as the reference motor.

In the embodiment, the X-axis motor 11 is used as a reference motor, and the actual current value AYIN of the Y-axis motor 17 is converted into the current value of the reference motor, so that the current detection conditions are made uniform.
Therefore, the actual current value AYIN of the Y-axis motor 17 is set to the predetermined determination value XA.
It is determined whether it is smaller than Y (step S44). This discriminant value XAY is set to a value capable of discriminating whether the Y-axis motor 17 is driven with no load, that is, during idle cutting or during cutting, for example, 20A.
Then, when the actual current value AYIN is smaller than the predetermined determination value XAY, it is determined that the idle cutting is being performed, the process proceeds to step S45, and Y
The reference conversion current value AY of the shaft motor 17 is calculated by the following equation (B1).

AY = AYIN + XK1 (B1) Here, XK1 is a correction constant and is set to, for example, 15A.

If the determination result in step S44 is negative, that is, if the actual current value AYIN is larger than the predetermined determination value XAY, it is determined that cutting is in progress, the process proceeds to step S46, and the reference conversion current value AY of the Y-axis motor 17 is set to the next value. Calculate with formula (B2).

AY = AYIN = K1 (B2) Here, K1 is a correction coefficient, and is set to a value of 1.4, for example. FIG. 9 shows the relationship between the reference converted current value AY converted as described above and the actual current value AYIN.

In this way, when the conversion of the required current value of the reference current value is completed, the process proceeds to step S47, and the current value of each axis motor obtained in this loop is added to the sum TA of the current values calculated in the previous loop. Then, the current value TA is calculated by the following equation (B3).

TA = TA + AS + AX + AY + AZ (B3) Then, in step S48 of FIG. 2C, it is determined whether or not the sampling number N1 has reached a predetermined value XN1. If it has not reached, after adding the value 1 to the sampling number N1 (step S49), the process returns to step S12, and the detection of the current value of each axis motor is repeated. When the number of sampling times N1 reaches the predetermined value XN1, the sum of the sampling values of XN1 times of each axis motor added as described above is stored as the tool cutting load TA, and the process proceeds to step S50.

In this embodiment, the tool cutting load TA is obtained by adding the current value of each axis motor including the main axis motor, but in some cases, two or more current values of the axis motors of the plurality of axes are added, The tool cutting load TA may be obtained from this addition sum.

Deceleration Calculation Process Next, the deceleration calculation process executed according to the tool cutting load TA obtained as described above will be described.

In step S52, the speed control device 32 determines whether or not the tool cutting load TA obtained as described above is larger than the predetermined reference value Xst. The relationship between the tool cutting load TA and the reference value Xst is shown in FIG. Tool cutting load T
A is a value obtained by summing the current values of the respective axis motors by sampling once for XN, and the area of the hatched portion in the figure corresponds to the tool cutting load TA. On the other hand, the reference value Xst
Is a value obtained by adding the reference current value Ast XN1 times, and corresponds to the area surrounded by the point O-XN1-D-Ast-O in the figure. As described above, the tool cutting load TA does not compare the detected current value for each sampling with the reference value, but compares the magnitude of the tool cutting load TA with the reference value by area comparison as shown in FIG. Therefore, the influence of disturbance and the detection error can be minimized.

The determination result of step S52 is positive, that is, the tool cutting load TA
Is larger than the predetermined reference value Xst, the process proceeds to step S60, and the deceleration calculation processing routine is executed.

11A and 11B show a flow chart of this deceleration calculation processing routine, and the speed control device 32 first sets the override amount KOR according to the tool cutting load TA (step S601). FIG. 12 shows the relationship between the tool cutting load TA and the override amount KOR set according to the tool cutting load TA. When the tool cutting load TA is a predetermined reference value Xst, the override amount KOR is 100. Is set to%,
When the tool cutting load TA is greater than the reference value Xst, the value decreases with an increase in the tool cutting load TA, and when the tool cutting load TA reaches the cutting maximum value XMAX, the value is set to 0%. here,
The reference value Xst is a value corresponding to the cutting load when the cutting amount by the cutter 20 is set to a predetermined value. Further, the maximum cutting value XMAX is a cutting load current value corresponding to the maximum allowable depth of cut when the depth of cut reaches the tool blade length. By limiting the maximum value of the tool cutting load TA to this value, the tool breakage occurs. Is being prevented. The relationship shown in FIG. 12 is set so that the machining allowance per tool blade is substantially constant, and when the cutting depth increases, the tool feed speed is set to be slow in inverse proportion to this. At this time, it is preferable from the standpoint of tool life that the rotation speed of the spindle is also reduced in proportion to the tool feed speed.

Next, the speed control device 32 determines whether or not the deceleration flag DFL is set to the value 1. When this deceleration calculation processing routine is executed for the first time, this flag is not normally set, so the subsequent steps are skipped and the routine is ended. That is, in this case, the override amount KOR is set as it is to a 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 step S62.
At 64, the startup amount HX (= 100-KOR) is calculated by the above equation (A1).

Next, proceeding to step S90 in FIG. 2F, the amount of override KO
It is determined whether or not R is larger than the upper limit value MAX, and if it is larger, the override amount KOR is reset to this upper limit value MAX and the process proceeds to step S96. On the other hand, if the overriding amount KOR is less than or equal to the upper limit value MAX, the process proceeds to step S91, and this time, it is compared with the lower limit value MIN.
The value is reset to MIN, and if it is equal to or more than the lower limit value MIN, the override KOR is not changed and the process proceeds to step S96.

In this embodiment, the lower limit value MIN is set to 0% and the upper limit value MAX is set.
Is set to 120%, for example, to prevent the feed rate from being controlled with a value outside the allowable range. Needless to say, these upper and lower limit values can be set to appropriate values depending on the performance of the die-cutting machine.

In step S96, the override amount KOR set as described above is output to the NC calculation unit 30a, and the feed speed of the cutter 20 designated by the NC data is calculated as the override amount KOR.
Deceleration correction is performed with OR to cope with a sudden change in the tool cutting load TA.

In step S602 of the deceleration calculation processing routine, when the deceleration flag DFL is set to the value 1, that is, when the deceleration calculation process is executed in the previous loop and the deceleration calculation process is continuously executed in this loop, step S6
The program proceeds to 03 to calculate the deviation Δk between the override amount KORn set in step S601 of the current loop and the override amount KORn-1 output to the NC calculation unit 30a last time.

Δk = KORn-KORn-1 (C1) Next, whether or not this deviation Δk is a negative value, that is, the override amount KORn set this time is determined from the override amount KORn-1 output to the NC calculation unit 30a. It is determined whether or not it is small. If the determination result is affirmative, that is, if the tool cutting load TA that is larger than the previous time is detected, this is output to the NC calculation unit 30a without changing the override amount KOR set in step S601. become.

On the other hand, if the determination result in step S604 is negative, the process proceeds to step S606 in FIG. 11B, and it is determined whether the count value NUP counted by the down counter is 0 or not. As this down counter, the same down counter as that used in the 10% startup processing routine described above may be used, or another down counter whose initial value is set to a different value may be used. If the count value NUP is not 0, the override amount KOR is the same value KO as the value output to the NC calculation unit 30a last time.
Rn-1 is set (step S607), and the deceleration calculation processing routine is ended. 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, step S607 is repeatedly executed until the count value NUP of the down counter is 0, and the override amount KOR is It is kept constant.

When the count value NUP of the down counter reaches 0, the determination result is affirmative in step S606, and the process proceeds to step S608. It is determined whether or not the startup amount HX is larger than the predetermined value XHX (40%). This determination is the same as the determination of the return processing described above, and if the determination result is affirmative, step
The process proceeds to S609, where the deviation Δk is the first predetermined value Δ
Determine if it is greater than K1 (10%). That is, it is determined whether or not the difference between the previous and current override amounts KOR is larger than a predetermined value ΔK1, and if the difference is larger, the override amount KOR calculated in step S601 is used as it is and output to the NC calculation unit 30a last time. The predetermined value ΔK1 is added to the override amount KOR-n1 and this is used as the override amount K in this loop.
OR (step S610). Then, step S6 described later
Proceed to 16.

On the other hand, in step S609, the determination result is negative, that is,
If the deviation Δk is less than or equal to the predetermined value ΔK1, the step is performed without changing the override amount KOR calculated in step S601.
Proceed to S616.

That is, when the tool feed speed is to be increased with respect to the overwrite amount KOR calculated in step S601 of FIG. 11A, a predetermined value is added each time a predetermined time elapses, and the tool feed speed is gradually increased. .

In step S608, if the determination result is negative, that is,
If the startup amount HX is smaller than the predetermined value XHX, step S
Proceeding to step 612, the deviation Δk is equal to the second predetermined value ΔK.
Determine whether it is greater than 2 (20%). That is, it is determined whether or not the difference between the previous and current override amounts KOR is larger than a predetermined value ΔK2. If the difference is large, the override amount KOR calculated in step S601 is used as it is and output to the NC calculation unit 30a last time. The predetermined value ΔK2 is added to the override amount KORn-1, and this is used as the override amount K in the loop this time.
OR (= KORn-1 + ΔK2) is set (step S614).

On the other hand, in step S612, the determination result is negative, that is,
If the deviation Δk is less than or equal to the predetermined value ΔK2, the step is performed without changing the override amount KOR calculated in step S601.
Proceed to S616. As described above, when the start-up amount HX becomes equal to or less than the predetermined value XHX, the tool feed speed is accelerated and the cutting time is shortened until the reference cutting load is reached.

When the startup amount HX reaches the predetermined value XHX, the override amount KOR may be set to 100% at once. As mentioned above, the tool feed speed is proportional to the depth of cut of the tool, and the cutting load was applied only near the cutting edge of the tool due to the execution of deceleration calculation processing. However, the load applied to the tool due to the increase in the override amount KOR. There is no risk of breakage of the tool even if the position of is raised to a position corresponding to the predetermined value XXH and the depth of cut is increased at once.

13A and 13B show examples of changes in the cutting amount of the cutter 20 and the override amount KOR output to the NC calculation unit 30a. In FIG. 13A, at each time t10, t11, and t12, the tool cutting load TA increases due to a sudden change in the depth of cut, and the override amount KOR is the time when the change in the tool cutting load TA is detected. It is set to a value according to the load TA to reduce the tool feed speed. Then, when a decrease in the tool cutting load TA is detected at time t13, the override amount KOR is not increased to a value corresponding to the tool cutting load TA at once, and a predetermined value is reached every time a predetermined time TUP (for example, 1 sec) elapses. Gradually increasing to ΔK1 (from t13 time to t14
Between time points). In this way, the tool feed speed is immediately reduced in response to a sudden increase in load, and gradually increased in response to a sudden decrease to prevent breakage of the tool.

In FIG. 13B, at t20, the tool cutting load TA increases due to a sudden change in the tool cutting amount, and then at t21, the tool cutting load TA decreases and the override amount KOR gradually increases.
Then, at time t22, the tool cutting load TA again rapidly increases and is rapidly reduced to the override amount KOR according to the magnitude of the load. At t23, the load is reduced again and the overriding amount KOR gradually increases, but at t24 the startup amount HX reaches the specified value XHX, so the overriding amount KOR is reached.
From that point, the increase amount of is gradually increased by the second predetermined amount ΔK2.

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 is the above-mentioned reference value Xs.
When it becomes smaller than t, the tool feed speed should be accelerated from the value specified by the NC data, but if the start-up amount HX has not yet returned to 0%, the above-mentioned step S54
Also, the determination result of step S56 becomes affirmative, the acceleration calculation process is ignored, and the above-described return process of FIG. 2E is executed. Then, the startup amount HX once returns to 0, and step S
After the deceleration flag DFL is reset to 0 at 88, 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 thereafter the tool cutting load TA is set to the reference value Xst.
When it becomes equal to, the tool feed speed should be held at the value specified by the NC data, but if the start-up amount HX has not yet returned to 0%, then the determination in steps S52 and S54 described above is performed. All the results are negative, and
The determination result of step S58 becomes affirmative, the speed maintaining process is ignored, and the above-described returning process of FIG. 2E is executed.
Then, the startup amount HX once returns to 0, the deceleration flag DFL is reset to 0 in step S88, and then the speed maintaining process (step S80) is executed.

Acceleration calculation process When the acceleration calculation process is executed, the tool cutting load TA is smaller than the reference value Xst, and the tool feed speed 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 is NC as it is.
The value may be output to the calculation unit 30a, or the value actually output may be gradually increased until the target override amount is reached. The override amount KOR set in the acceleration calculation process is output to the NC calculation unit 30a after undergoing an upper and lower limit value check described later (steps S90 to S94).

Speed maintenance processing The speed maintenance processing is executed when 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 specified by NC data. Will be held at the specified value.

Abnormality processing When abnormal vibration or abnormal sound is detected by the AE sensor 40 during cutting in step S26, or in step S5
At 0, when it is detected that the tool cutting load TA is equal to or more than the maximum cutting value XMAX, the routine proceeds to step S27 in FIG. 2G and the abnormality processing routine is executed. As the abnormality processing executed in this abnormality processing routine, various processing methods are conceivable. For example, the automatic operation of the NC arithmetic device is suspended,
The rotation of the spindle is stopped, the override amount KOR is set to 0%, the supply of shop air and cutting oil is stopped, and an alarm is issued to the operator. Processing such as processing is executed.

When the above-mentioned processing at the time of abnormality is completed, the speed control device 32 inputs the signal level of a specific key of the myal operation panel 39 (step S28), and checks whether or not the return signal is output from this specific key. It is determined (step S29). Then, steps S28 and S29 are repeatedly executed until the return signal is input. That is, the speed control device 32 waits until the abnormality processing by the operator is completed after the occurrence of the abnormality described above.

When the operator completes the abnormal processing such as the replacement of the cutter and the return signal is input, the speed control device 32 causes the second A
Returning to step S10 in the figure, the stored value is initialized again to restart the above-described control of the tool feed speed and the like.

In the above-described embodiment, the table 10 of the NC type engraving machine moved in the X-axis direction with respect to the cutting tool (cutter) 20, but the table 10 is fixed so that the cutting tool 20 moves with respect to the table 10. It may be mobile. That is, the present invention corrects the relative movement speed between the cutting tool and the work by the amount of override, and either the cutting tool or the work may move. In addition, the table on which the work is placed and fixed rotates and the cutting tool moves in the X, Y, and Z directions in response to this.
Of course, it may be a cutting device.

(Effects of the Invention) As described in detail above, according to the NC cutting device of the present invention, a plurality of drive motors for moving a cutting tool in a multi-axis direction including rotation, and a plurality of these drive motors are provided. A load sensor that detects the cutting load of the cutting tool from the sum of at least two or more current loads, and an override calculation device that calculates the amount of override according to the tool cutting load detected by this load center The NC computing device corrects the tool feed speed specified by the numerical control data according to the amount of override calculated by the override computing device, and the cutting tool is moved relative to this corrected tool feed speed. The tool feed speed can be automatically adjusted in response to sudden changes in the load on the tool, the burden of manual operation on the operator is reduced, and tool breakage accidents can be prevented in advance. Both can be set higher tool feed speed command value in the numerical control data, it is possible to significantly shorten the machining time.

Further, the load sensor detects the cutting load of the cutting tool from the sum of at least two current loads among the plurality of drive motors, and preferably defines a reference motor, and at least one of the plurality of drive motors. The current load detected from one is converted to the current load of the reference motor, and the added sum of the current loads is calculated using this converted current load, so the influence of disturbance etc. is eliminated to the minimum and tool cutting is performed. The load can be calculated accurately.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of an NC type engraving machine according to the present invention, FIGS. 2A to 2G are flow charts for explaining a procedure for generating an override amount KOR, and FIG.
FIG. 4 is a flow chart of the cutting start deceleration processing routine, FIG. 4 is a timing chart showing the relationship between the workpiece outer shape and the tool feed speed, FIG. 5 is a flow chart of the 10% start-up processing routine, and FIG. FIG. 7 is a graph showing the relationship between the tool feed speed VF and the load (current value A) of the shaft motor, FIG.
Fig. 9 is a graph showing the relationship between the depth of cut and the load (current value A) of the shaft motor, Fig. 9 is a graph showing the relationship between the actual current value of the Y-axis motor and the reference converted current value, and Fig. 10 is , The sum TA of the current value of each axis motor sampled a predetermined number of times,
Graphs showing the relationship with the reference value Xst, FIGS. 11A and 11B are flowcharts of the deceleration calculation processing routine,
FIG. 12 is a graph showing the relationship between the tool cutting load TA and the override amount KOR set by it, and FIGS. 13A and 13B show an example of the relationship between the tool cutting amount and the override amount KOR. It is a timing chart. 1 …… NC type engraving machine, 10 …… table, 11 …… X-axis motor,
12 …… Column, 14 …… Cross beam, 15 …… Z axis motor, 16 …… Spindle head, 17 …… Y axis motor, 18 …… Spindle motor, 20 …… Cutter (cutting tool), 30 …… NC Calculation processing, 30a ... NC calculation unit, 30b ... Servo motor drive control unit, 32 ... Speed control device (override calculation device), 36
...... NC data reader, 38 ...... switch, 39 ...... manual operation panel, 40 ...... AE sensor, 41 to 44 ...... axis motor load sensor.

Claims (2)

[Claims] 1. A cutting tool is placed at a required position in a multi-axis direction at a required speed, relative to a workpiece, based on numerical control data read from an external data reading device into an NC computing device. Sequentially move and cut the work piece into the required shape
In the NC cutting device, a plurality of drive motors that move the cutting tool in a multi-axis direction including rotation, and the cutting of the cutting tool from the sum of at least two or more current loads of the plurality of drive motors. A load sensor for detecting the load, and an override calculation device for calculating the amount of override according to the tool cutting load detected by the load sensor,
The NC arithmetic unit corrects the tool feed speed specified by the numerical control data according to the override amount calculated by the override arithmetic unit, and relatively moves the cutting tool at the corrected tool feed speed. NC cutting device. 2. A reference motor is defined, and a current load detected from at least one of the plurality of drive motors is converted into a current load of the reference motor, and the converted current load is used to convert the current load. The NC cutting device according to claim 1, wherein an addition sum is obtained.