JPS582028B2 - Tekiou Seigiyosouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an adaptive control device in a numerically controlled lathe.

SUMMARY OF THE INVENTION An object of the present invention is to provide an adaptive control device that can control feed rate so that cutting conditions such as cutting force are within allowable values.

Conventionally, in cutting, especially turning, it is necessary to control the feed rate in order to keep the cutting force constant without changing the tool path.

The feed amount during turning is determined by the blade position on the cutting surface before one rotation of the workpiece and the blade position at the same rotational position in the next rotation.

Therefore, even if the feed rate is immediately changed by a wide range because the cutting force is excessive, the result will not be correct until the main shaft rotates once.

Therefore, control becomes unstable. This instability is particularly noticeable when cutting begins.

In the present invention, a comparison circuit is provided that compares the output of a sensor that detects the cutting state with a reference value of a cutting reference value register and outputs a cutting signal, and the start of cutting is determined based on this comparison circuit.

Furthermore, in order to eliminate the conventional drawback that the air cutting time becomes long due to the shape error of the workpiece, the present invention provides a prediction that allows setting an arbitrary value between the upper and lower limits of the feed rate as the expected feed rate. A feed rate setting circuit is provided, and the value of the expected feed rate setting circuit is set in the register A which selects the data selector based on the determination of the start of cutting and instructs the pulse spread rate of the BRM.

This makes it possible to set approximately the desired feed rate at the start of cutting and stabilize the control system.

As a result, in the blade feed state when not cutting, that is, during air cutting, the feed rate can be significantly increased and the expected feed rate can be achieved at the same time as cutting, and the air cutting time can be significantly shortened.

Furthermore, conventionally, depending on the shape of the workpiece, the depth of cut may be small and the cutting force may be small.

In this case, even if the feed rate is increased in order to make the cutting force equal to the allowable cutting force, the cutting force does not actually increase, and there is a drawback that a thread with a large lead ends up being cut.

Therefore, in the present invention, the above-mentioned problem is solved by setting an upper limit value for the feed and preventing the feed from increasing faster than the upper limit even if the cutting force is smaller than the allowable value.

That is, a first full adder that calculates the output of the sensor and the allowable value of the allowable cutting register, and a second full adder that adds the output from the first full adder and the contents of register A stored in register B. Then, the output of the second full adder is compared with the feed rate upper limit value of the feed upper limit value command circuit, and if the output of the second full adder is larger than the upper limit value, the output of the second full adder is replaced with the output of the second full adder. A main feedback circuit is constituted by a comparator circuit that selects the upper limit value and a register A that instructs the BRM to set a pulse spreading rate based on the selected upper limit value, so that the feed is not faster than the upper limit value. is controlled.

When controlling the feed in turning, there is a problem in that the control results are not displayed correctly until after one rotation.

For this reason, stable cutting cannot be achieved even if controlled at high speed.

In order to solve this conventional problem, in the present invention, register A
The value of is stored in register B, and the value of the difference between the cutting force from the first full adder and the allowable value is given to the second full adder and added to register B.

By giving the result of this second full adder to register A, the BRM for feed rate control is controlled so that the difference between the cutting force and the tolerance value is reduced. By controlling according to the rotational speed of the spindle, it is possible to control the feed rate smoothly and achieve stable control.

As a result of the above, the feed is set to the expected feed rate at the same time as cutting begins, and excessive cutting force is not applied, so a large number of rotations is not required to control excessive cutting force, and a decrease in control response speed is avoided. It doesn't bring.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention, where 1 is a main shaft that rotates while gripping a workpiece, and 2 is a position coder that rotates in synchronization with the main shaft 1. FIG.

3 is a numerical control device that controls the X-axis and Z-axis of the lathe, gives a feed motion to the cutter to cut the workpiece gripped by the spindle 1, and receives output pulses from the position coder 2 to control the speed per rotation of the spindle. The feed rate of the cutter is determined.

Reference numeral 4 denotes an ink face, which determines commands from the numerical control device 3, such as MO3 for normal rotation of the main shaft, MO5 for stop of the main shaft, etc., and issues commands to various parts.

In the present invention, for example, M90 and M9
1 gives a command, and when M90 gives a command for normal cutting,
When M91 is selected, the normal cutting command is canceled.

5 is a sensor that is incorporated into the tool post to detect the main cutting force, but it also detects the power of the moke that drives the main shaft, the feed component force, and the thrust force. Sensors are also possible.

The output of this sensor 5 is converted into a digital signal by an AD converter 6.

Reference numeral 7 denotes a zero adjustment circuit, which functions to store the output of the sensor at no load and send out only the net load of the sensor at load.

8 is a cutting force register, which is a register for storing the net cutting force.

9 is a clock pulse generation circuit, 10 is a command pulse generation circuit, and AD is controlled by a signal from the clock pulse generation circuit 9.
An AD conversion start command is issued to the converter 6, and the AD converter 6
Upon receiving the AD conversion completion signal from the zero adjustment circuit 7, a zero adjustment instruction is issued in synchronization with the clock pulse, and the cutting force register 8 is stored in synchronization with the clock pulse after the zero adjustment is completed.
An AD conversion command is issued in synchronization with the next clock pulse.

The above operations are always repeated at a very fast rate, usually once every 50 microseconds.

The value in the cutting force register 8 is compared with the cutting reference value in the cutting reference value register 11 in a comparison circuit 12 .

When the value of the cutting register 8 becomes larger than the cutting reference value, the comparator circuit 12 issues a cutting signal.

That is, as shown by the thick line in FIG. 1a, there is a comparison circuit 12 which compares the output of the sensor 5 with the cutting reference value of the cutting reference value register 11 and outputs a cutting signal, and an upper limit value and a lower limit value of the feed rate, which will be described later. An expected feed rate setter 28 that can set any value between the two as the expected feed rate; A cutting start control circuit 26 that selects a feed rate, and a pulse spreading rate based on the selected expected feed rate signal that controls the BRM 21.
The expected feed rate command circuit is formed by the register A20 that instructs the expected feed rate.

On the other hand, the value of the cutting force register 8 and the allowable cutting force register 13 which gives the allowable value of the cutting force in the adaptive control device to be executed now are subtracted by the first full adder 14 by (allowable cutting force and total cutting force). Let's do it.

Further, the output of the first full adder 14 is input to the second full adder 15 and added to the contents of the register B16.

The output of the second full adder 15 is input to a data selector 17 and a comparison circuit 18.

The comparison circuit 18 compares the upper limit value from the feed upper limit value command circuit 19 and the output of the second full adder 15, and
When the output of the second full adder 15 is large, a command is issued to the data selector 17 so that the data selector 11 selects and outputs the upper limit value from the feed upper limit value command circuit 19, and when the output of the second full adder 15 is small, the second The input from the full adder 15 is output as is.

The data selector 17 is connected to the second full adder 15 as described above.
The output from
Before selecting either the output from the full adder 15 or the upper limit from the feed upper limit value command circuit 19 and outputting it to the register A20, the expected feed rate is determined by a cutting start signal from the cutting start control circuit 26 as described later. The expected feed rate set in the setter 28 is selected and output to the register A20.

Register A20 is a binary rate multi-counter (B
RM) Acts as a register to command the spreading rate of 21,
The pulse train from position coder 2 is converted to B according to this rate.
The RM21 spreads and is sent to the numerical control device 3.

That is, as shown by the thick line in FIG. 1b, the first full adder 14 calculates the output of the sensor 5 and the allowable value of the allowable cutting force register 13, and the output from the first full adder 14 is stored in the register B16. The output of the second full adder 15 is added to the stored content of the register A20, and the output of the second full adder 15 is compared with the feed speed upper limit value of the feed upper limit command circuit 19. a comparison circuit 18 that causes the data selector 11 to select the upper limit value instead of the output of the second full adder 15 when the output is larger than the upper limit value; A main feedback circuit is formed by the register A20 that instructs.

Note that the expected feed rate setter 28 can set an arbitrary value between the upper limit and the lower limit of the feed rate to, for example, a digital switch, and when the signal g is input to the data selector 17, it is set to the data selector 1γ. This set expected feed rate value is selected and output to register A20.

With this configuration, the relationship between cutting force and feed control in turning processing is stabilized.

In other words, in turning, the feed amount is determined by the blade position on the cutting surface before one rotation of the workpiece and the blade position at the same rotational position in the next rotation, and the product of the feed amount and the depth of cut is the cutting force. decide.

Therefore, if the depth of cut is constant, even if the cutting force is excessive and the feed rate is immediately changed by a wide range, the result will not be correct until the spindle rotates once.

This phenomenon is particularly noticeable at the start of cutting, making the system unstable.

In order to prevent this and make the system stable, the feed rate is set to the expected feed rate at the start of cutting.

Also, when the cutting force is small, the feed rate is increased, but in turning with a single cutting tool, if the depth of cut is small, no matter how high the feed rate is, the cutting force will not increase significantly; This will result in a thread-shaped cut.

To prevent this, a feed upper limit value command circuit is provided to prevent thread-shaped cutting from occurring.

Furthermore, another effect of setting the upper limit is that the feed can be controlled within the effective range of the chip breaker in order to cut chips that are continuously generated.

If the contents of the register A20 are smaller than the output of the lower limit value setting circuit 22, an output 24 can be output to the outside.

The setting of this lower feed limit value means that a large decrease in the feed rate has occurred in a situation that would not occur in normal cutting, such as when the cutting edge is worn out and cannot be used.

The comparison circuit 23 discriminates this and outputs an output 24 to the outside.

This output is used to temporarily stop the feed and alert the operator.

On the other hand, the contents of register A20 are stored in register B16 by a command from register control circuit 25.

Then, the contents of the register A20 are changed by the control circuit 25 and the OR circuit 27, so that after the spindle 1 rotates at the expected feed rate for the first rotation, the feed rate is corrected for each rotation. The cutting force is controlled to be equal to the allowable cutting force.

That is, as shown by the bold line in FIG. 1c, the feed rate correction circuit adjusts the expected feed rate signal selected and output from the data selector 17, the feed rate signal corresponding to the output of the second full adder 15, and the feed rate signal. The register B16 stores the speed upper limit signal, and the second full adder 1 stores the contents of the register B16 every rotation of the spindle 1.
The register control circuit 25 outputs the register A20 storage command of this register control circuit 25 and the register A20 storage command from the cutting start control circuit 26 to the register A.
20.

Next, the register control circuit 25, cutting start control circuit 26, and OR circuit 27 will be explained with reference to FIG.

When cutting using adaptive control begins, the blade first begins cutting the workpiece.

The slight increase in cutting force at the beginning of cutting is detected by the comparator circuit 12, and this cutting signal ON signal a is input to the cutting start control circuit 26.

101 is a shift register, and signal a serves as its data input.

Further, 102 is an AND circuit, and when the signal a and the memory finger 4d to the cutting force register 8 are not being commanded, the inverter 103
The input pulse to the shift register 101 is determined by the signal that becomes a significant signal, the clock pulse C, and the output of the fourth bit of the shift register 101.

The cutting ON signal a is also input as a clear signal to the shift register 101, and clears the shift register 101 when cutting is not in progress.

When cleared, the output Q1-Q of the shift register 101
2, Q3, and Q4 become zero level, and the output Q1
, Q2, Qs, and Q4 are at level 1.

When cutting starts and the cutting is in progress, and the cutting ON signal a becomes 1 level, the AND circuit 102 opens and the clock pulse C
is given to the shift register 101.

Since the data in the shift register 101 is also at level 1, Q1 becomes 1 with the first pulse, and Q1 with the next pulse.
2 also becomes 1.

Also, in the next pulse, Q3 becomes zero, and in the next pulse, Q4
will also be zero.

Therefore, the output of gate 104, which is an AND circuit, is the first
The signal g to the data selector 17, which remains at 1 level from the input of the pulse 1 to the input of the fourth pulse, instructs the data selector 17 to select and output the output of the expected feed rate setter 28.

At the second pulse, the output of gate 105, which is an AND circuit, is 1.
Then, the storage command e is given to the register A20 through the OR circuit 27.

With the third pulse, the output of the gate 105 disappears, and with the fourth pulse, Q4 becomes zero level and the AND circuit 102 is closed.

In other words, even if a clock pulse comes to the AND circuit 102, it will not pass through.

Further, the finger +b from the interface 4 and the signal negated by the inverter 106 of the cutting ON signal a pass through the OR circuit 107, and the register A preset signal h presets the register A20, making the output of the register A20 all 1. Make it.

Therefore, all outputs of the register A20 are 1 when cutting is not being performed and when the pulses of the position coder 2 should not be applied to the BRM 21 according to a command from the numerical control device 3.

Next, the function of the register control circuit 25 will be explained.

A pulse P synchronized with the rotation of the main shaft from the position coder 2 is input to the register control circuit 25, and is counted by a 10-bit binary counter 201.

In this embodiment, the pulse from the position coder 2 is sent to the main shaft 1.
The rotation will be explained as 1024 pulses.

The binary counter 201 becomes all 1 at the 1023rd pulse, and outputs a carry pulse to the flip-flop 202 at the 1024th pulse.

The flip-flop 202 receives a set pulse once per rotation of the main shaft.

The output Q of the flip-flop 202 is at level 1, and the level is 5.
The data input signal D of the bit shift register 203 is set to 1.
Also, the reset state of flip-flop 204 is released.

The storage command d to the cutting force register 8 is stored in the flip-flop 2.
When 04 is activated, the Q output of the flip-flop 204 becomes 1 level, and the gate 205, which is an AND circuit, is opened and the clock pulse C is passed through the 5-bit shift register 20.
Sends a 3 hectare clock pulse.

The shift register 203 sets Q1 to 1 at the first pulse of the clock pulse, sets Q2 to zero at the second pulse, sets Q3 to 1 at the third pulse, sets Q4 to zero at the fourth pulse, and sets Q5 to 1 at the fifth pulse. do.

Therefore, gate 206, which is an AND circuit, connects Q1 and Q
When the first pulse is input by the signal No. 2, an output is output to the OR circuit 27, and when the second pulse is input, no output is output.

Q3 and Q4 are input to the gate 207, which is an AND circuit, and when the third pulse is input, the gate outputs an output, and when the fourth pulse is input, the gate stops outputting.

Therefore, the cutting force register 8 first stores the information, and the first full adder 14 and the second full adder 15 are stored until the next pulse, that is, the first pulse to the shift register 203.
completes the calculation, the data selector 17 normally selects and outputs the output of the second full adder 15, stores it in the register A20 with the first pulse and the second pulse, and stores the stored contents in the third pulse and the second pulse. It is stored in register B16 with 4 pulses.

With the fifth pulse, Q5 becomes 1, and the flip-flop 202 is reset through the gate 208, which is an OR circuit, and its output Q becomes zero.

The above is the function of the register control circuit 25 for each rotation of the main shaft.

The output of gate 105 caused by the cut ON signal passes through gate 208 to reset flip-flop 202 and resets 10-bit binary counter 201.

An overview of the operation of this embodiment based on the above explanation is as follows:
Register A20 that controls BRM21 when not cutting
is preset to all 1, and the BRM 21 sends the pulses of the position coder 2 to the numerical control device 3 without disturbing them.

If, for example, the adaptive control is activated in M46 and the normal numerical control is activated in M47 according to a command from the numerical control device 3, the register A20 is preset to all 1s in M47.

In the case of M46, when cutting starts, a cutting signal is issued from the comparator circuit 12, the data selector 17 selects the expected feed rate, the expected feed rate is input to the register A20, and the BRM21 receives the signal from the position coder 2. The pulse is spread and sent to the numerical control device 3, and as a result, the numerical control device 3
will advance the cutting edge at the expected feed rate.

The gate 105 turns on the binary counter 2 by the cutting ON signal a.
01 and flip-flop 202 are reset, the feed proceeds at the expected feed rate during one spindle rotation, but when the binary counter 201 exceeds, the feed rate is changed based on the difference between the cutting force and the allowable cutting force. The contents of register A for control can be changed.

The feed rate is adjusted every rotation of the main shaft, and the cutting force is controlled to be equal to the allowable cutting force.

As a result of the control, when there is a possibility that the feed may exceed the upper limit value, the comparison circuit 18 provided in the feedback circuit described above is used to control the feed so as not to exceed the upper limit value, and when the feed reaches the lower limit value, it is considered that there is an abnormality and the feed is stopped. The comparator circuit 23 performs processing such as stopping.

In this example, the feed rate is changed by sampling every rotation of the spindle, but this is because the cutting force in turning is determined by the feed amount, and the result of changing the feed rate is that the spindle is
This is because it will not appear completely unless it is rotated more than once.

Therefore, it is dangerous to change the feed rate after waiting one rotation while keeping the feed rate too high, so the control is performed by changing the feed rate to the expected feed rate at the same time as cutting.

Generally, from a position coder, it is called a one-rotation signal.
Pulses that occur only once per spindle rotation and spindle 1
There are pulses that produce hundreds or thousands of pulses during rotation.

In the embodiment of the present invention, the latter pulse is used, but it is also possible to use the set pulse to the flip-flop 202 in the embodiment as the timing for controlling the feed speed using the one-rotation signal. In this case, the binary counter 201 becomes unnecessary.

Therefore, although it is inexpensive, a method that resets the binary counter at the beginning of cutting and starts the set signal of the flip-flop 202 causes a delay in control for one revolution of the main shaft.

However, since the feed rate is changed to the expected feed rate at the same time as cutting is turned on, it is sufficiently practical.

As described above, according to the present invention, since the start of cutting can be determined, cutting can be performed at the expected feed rate at the same time as the start of cutting.

Therefore, excessive cutting force that is likely to occur at the start of cutting is not generated, and the system is stabilized.

In addition, due to this effect, even if the feed rate is commanded to be about three times faster than the expected feed rate when the cutting edge is not in contact with the workpiece, the expected feed rate can be set at the same time as cutting starts, so cutting It is possible to shorten the so-called air cutting time in which the cutting edge approaches the workpiece without cutting.

In other words, the pulse of the position coder that spreads in BRM is 2048. A very large number of pulses, such as 1024 pulses, are generated per spindle rotation, and as this is confusing, register A is set so that 100% of the pulses from the position coder pass through when cutting is not being performed, so-called air cutting. If, at the same time as cutting starts, the value of register A is reset to 1/3 using the expected feed rate setting device, and the BRM deflection rate is set to 1/3, the speed during air cutting will be three times that during cutting. When the feed rate is given and the air cut time is given in advance at the expected feed rate (
This is 1/3 compared to the amount used in general cutting.
It can be shortened to

Also, during cutting, the pulses of the position coder are scattered by the BRM, and when considering the expected feed rate, 1/3 of the amount is NC.
The amount of pulses sent to the device is approximately 600 or 300 pulses per rotation of the main shaft.

By increasing or decreasing this by 6 pulses or 3 pulses, the cutting force can be changed by 1%, so unlike the conventional override method in which the feed rate is controlled in 10% increments, the air cutting time can be shortened and the cutting force can be changed by 1%. When the feed rate is controlled, the feed rate does not suddenly change by more than 20%, and control accuracy can be maintained at a sufficiently high level.

Further, since the feed rate can be set to the expected feed rate at the same time as cutting starts, excessive cutting force is not generated.

Therefore, there is little fear that the workpiece or cutting edge of the tool will be damaged.

Furthermore, in turning, correct feed control results cannot be obtained until after one revolution of the workpiece, and if the feed rate is changed immediately when the cutting force changes during cutting, the system tends to become unstable.

However, in the present invention, the feed rate is changed in synchronization with the rotation of the main shaft, and the next feed rate is determined and controlled after the results of the changed feed rate are obtained, so the control system is stable.

Further, since the feed rate under control by the feed upper limit value command circuit and the comparison circuit does not exceed the upper limit value, it is possible to keep the roughness of the cut surface within a certain predetermined range.

That is, the upper limit value of the feed rate can be set based on the roughness of the cutting surface.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of an adaptive control device according to the present invention, FIG. 1a is an explanatory diagram of an expected feed rate command circuit, and FIG.
FIG. b is an explanatory diagram of the main feedback circuit, FIG. 1c is an explanatory diagram of the feed rate correction circuit, and FIG. 2 is a block diagram of the register control circuit and cutting start control circuit. 1: Main shaft, 2: Position coder, 3: Numerical control device, 4: Interface, 5: Sensor, 6 ...AD
Converter, 7... Zero adjustment circuit, 8... Cutting force register, 9... Clock pulse generation circuit, 10... Command pulse generation circuit, 11. ...
... Cutting reference value register, 12 ... Comparison circuit, 13 ... Allowable cutting force register, 14 ...
...First full adder, 15...Second full adder, 16...Register B117...Data selector, 18...Comparison circuit, 19...・・・
...Feed upper limit value command circuit, 20...Register A
, 21...BRM, 22...Feed lower limit value setting circuit, 23...Comparison circuit, 25...
... Register control circuit, 26 ... Cutting start control circuit, 27, 107, 208 ... OR circuit,
102, 104, 105, 205, 206, 207...
...AND circuit, 101,203...Shift register, 103,106...Inverter,
201... Binary counter, 202, 204...
...flip flop.

Claims (1)

[Claims] 1. A main shaft 1 that grips and rotates a workpiece, a position coder 2 that rotates in synchronization with the main shaft 1, a BRM 21 that spreads output pulses from the position coder 2, and
In an adaptive control device comprising a numerical control device 3 that receives the output of the RM 21 and controls the feed rate, and a sensor 5 that detects the cutting state, the output of the sensor 5 is compared with the reference value of the cutting reference value register 11. a comparison circuit 12 that outputs a cutting signal during cutting; an expected feed rate setter 28 that can set an arbitrary value between the upper limit and the lower limit of the feed rate as an expected feed rate; A cutting start control circuit 2 that causes the data selector 17 to select the expected feed rate set in the expected feed rate setter 28 based on the intermediate signal.
6, and a register A20 for instructing the BRM 21 a pulse spreading rate based on the selected expected feed rate signal.
a first full adder 14 that calculates the output of the sensor 5 and the allowable value of the allowable cutting register 13; The register A20
a second full adder 15 that adds the memory contents of the second full adder 15;
The output of the full adder 15 is compared with the feed rate upper limit value of the feed upper limit value command circuit 19, and when the output of the second full adder 15 is larger than the upper limit value, the data selector 17 selects the output of the second full adder 15. An adaptive control device comprising a main feedback circuit comprising a comparison circuit 18 that causes the upper limit value to be selected instead, and the register A20 that instructs the BRM 21 to set a pulse spreading rate based on the selected upper limit value. 2. A main shaft 1 that grips and rotates a workpiece, a position coder 2 that rotates in synchronization with the main shaft 1, a BRM 21 that spreads output pulses from the position coder 2, and a BRM 21 that spreads output pulses from the position coder 2.
In an adaptive control device including a numerical control device 3 that controls the feed rate in response to the output of M21, and a sensor 5 that detects the cutting state, the output of the sensor 5 is compared with the reference value of the cutting reference value register 11. a comparison circuit 12 that outputs a cutting signal from the comparison circuit 12; an expected feed rate setter 28 that can set an arbitrary value between the upper and lower limits of the feed rate as the expected feed rate; a cutting start control circuit 26 that causes the data selector 17 to select the expected feed rate set in the expected feed rate setter 28 based on the signal;
An expected feed rate command circuit includes a register A20 that instructs the BRM 21 to a pulse spread rate based on the selected expected feed rate signal, and calculates the output of the sensor 5 and the allowable value of the allowable cutting register 13. 1st
a full adder 14, a second full adder 15 that adds the output from the first full adder 14 and the contents of the register A20 stored in the register B16, and an output of the second full adder 15 and a feed upper limit value command. When the output of the second full adder 15 is larger than the upper limit value by comparing the feed rate upper limit value of the circuit 19, the data selector 17 selects the second feed rate.
a comparator circuit 18 that selects the upper limit value instead of the output of the full adder 15; and the register A that instructs the BRM 21 to set a pulse spreading rate based on the selected upper limit value.
20, and the expected feed rate signal selected and outputted from the data selector 17, the feed rate signal corresponding to the output of the second full adder 15, and the signal of the feed rate upper limit value. The register A20 stores the contents of the register A20, the register B16 stores the contents of the register A20, and the register control circuit 25 outputs the contents of the register B16 to the second full adder 15 according to the rotational speed of the main spindle 1. and a feed rate correction circuit.