JPH0453649A - Irregular revolution speed cutting method - Google Patents

Abstract

PURPOSE:To check a chattering vibration without requiring any exclusive jig and tools by varying a spindle speed irregularly within the range of the preset speed, in a control system having the spindle speed and a cutting feed rate synchronized. CONSTITUTION:A spindle speed command of a program memory 21 is read by a program interpretative part 22, and when an irregular speed command exists in that part, both upper and lower limit values of the irregular revolution of program designation are stored in a revolution range storage part 23. Next, whether there is an irregular speed starting signal or not is checked, and when YES is the case, random numbers are generated within both these upper and lower values at the random number generating part 24, and the random number is converted into the corresponding revolution at a random number revolution converting part 25, outputting a revolution command varying in random. With this constitution, a spindle is irregularly rotated by the irregular revolution command preferentially inputted by way of an interrupt input circuit of a function generating speed control part 26.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of cutting by driving the main shaft of a machine tool such as an NC lathe or machining center at an irregular rotation speed.

Conventional technology Conventionally, when cutting the outer diameter of a long workpiece using an NC lathe,
When performing wide-width, deep-groove cutting, or when performing deep hole machining with a boring bar on an NC lathe or machining center, if the rigidity of the workpiece or the cutting tool is low, vibration is likely to occur during cutting. Even if you take measures such as changing the shape or cutting conditions, stable cutting is often not achieved. For long workpieces, use a support device such as a steady rest.
Currently, boring bars with anti-vibration structures are used and cutting conditions are lowered.

Problems to be Solved by the Invention The method of machining a long workpiece using a support device such as a steady rest, as described in the conventional technology, has poor workability, requires specialized technology, and cannot be automated. The method of using a boring bar with an anti-vibration structure has problems in that it is costly and cannot be expected to be completely effective.

The present invention was made in view of the above-mentioned problems of the conventional technology, and its purpose is to control the spindle rotation speed irregularly in a control system that synchronizes the spindle rotation speed and the cutting feed rate. It is an object of the present invention to provide a cutting method that can suppress chatter vibration without requiring special jigs and tools.

Means for Solving the Problems In order to achieve the above object, the irregular rotational speed cutting method of the present invention irregularly adjusts the spindle rotational speed at locations where chatter is likely to occur during cutting within a preset speed range. It is something that changes.

In addition, the location where chatter occurs is detected in advance by a sensor and stored in the machining program using a learning function, and the spindle rotation speed at the location where chatter occurs is irregularly changed within a preset range from the next cutting process. .

In addition, a sensor detects the occurrence of chatter during cutting,
The spindle rotational speed is changed irregularly within a preset speed range.

Operation claim 1 is characterized in that the machining program is preset at irregular rotational speeds.
By setting the lower limit and entering irregular rotation 0N-OFF commands before and after areas where chatter is likely to occur, when the cutting process reaches an area where chatter is likely to occur, the spindle will rotate at an irregular rotation speed that changes randomly. Machining is performed using a cutting feed rate synchronized with the spindle.

A second aspect of the present invention is to detect the occurrence of chatter with a sensor when cutting the first item, and use a learning function to insert and memorize an irregular rotation 0N-OFF command in the machining program, so that from the next time onwards, when the occurrence of chatter occurs, Rotates the main shaft irregularly.

According to a third aspect of the present invention, irregular rotation is started when the sensor detects chatter during cutting, and the irregular rotation is canceled when the next block command is issued after the feed shaft has been positioned and stopped.

Embodiment A first embodiment will be described with reference to FIGS. 1 to 3.

In a well-known NC lathe, there is a headstock 2 on the left side of the bed 1.
is installed, and a main spindle 3 is rotatably supported on a headstock 2 by a plurality of bearings. The main shaft 3 is an NC fixed on the bed.
It is rotated by the main motor 4 of wI@ via the heald 5,
A pulse generator 6 is attached to the headstock 2 to detect rotation of the spindle. A tailstock 7 is movably mounted on a sliding surface in the Z-axis direction cut on the bed 1, and a long workpiece is gripped by a chuck 8 fitted to the tip of the spindle 3. The right end of W is supported by the 6-press center 9.

A carriage 1) is movably mounted on the Z-axis sliding surface of the bed 1, and the carriage 1) is moved and positioned via a ball screw 13 by a two-axis servo motor 12 fixed to the bed, and the servo A position detector 14 is fixed concentrically to the motor 12. A tool rest 15 is movably placed on a sliding surface in the X-axis direction cut into the upper surface of the reciprocating carriage 1).
5 is moved and positioned via a ball screw 17 by an X-axis servo motor 16 fixed to the carriage, and the servo motor 16
A position detector 18 is fixed concentrically to the position detector 18 .

A turret 19 is provided on the tool rest 1) so as to be rotatable and indexable in the X-axis vertical plane, and a plurality of tools on the outer periphery of the turret 19 are mounted on a stationary run with a pie for outer diameter (TA) and a pie for wide grooving) TB, respectively. It is removably attached.

Next, an embodiment of an NC main shaft rotation and X-axis or Z-axis feed servo system will be described with reference to the block diagram of FIG. Note that part A is a part related to the present invention, and the other parts are the same as a general servo system.

The program memory 21 is a section that stores program contents read by an external device such as a tape reader section or a floppy disk, or program contents input from a servo motor, and the program interpreter section 22 is a section that stores program contents for one block of part programs. The 0 rotation speed range storage section 23, which reads from the memory, interprets it, sorts it into necessary locations, and outputs a signal, is a section that stores the upper and lower limits of irregular rotation speed, and the random number generation section 24 stores the rotation speed. The random number-to-rotation speed converter 25, which generates random numbers such that the target rotation speed changes randomly within the range of the upper limit value and lower limit value stored in the range storage unit 23, converts each rotation speed corresponding to the random number. This is the part that converts random numbers into rotational speeds using a predetermined mask table. Function generation speed control section 2
When the rotational speed of the main motor 4 and the feed rate of the X-axis or Z-axis are inputted from the program interpretation unit 22, 6 generates a function to calculate the feed rate in synchronization with the rotation of the main shaft.
It is equipped with an interrupt input circuit that gives priority to the rotation speed signal input from the random number/rotation speed conversion section 25 over the rotation speed signal input from the program interpretation section 22.

The rotational speed command section 27 compares the signal from the pulse generator 6 with the signal from the function generation speed control section and outputs a signal that makes the commanded rotational speed. This is the part that supplies driving power to the

The position-velocity converter 28 converts the position signal from the X-axis position detector 18 or the Z-axis position detector 14 into a speed signal, and the feed rate command unit 29 converts the signal output from the position-velocity converter 28. The current command section 31 compares the signal output from the function generation speed control section 26 with the signal outputted from the function generation speed control section 26, and sends a signal that achieves the command speed to the current command section 31. A part that compares the input signal to the axis servo motor 16 or the Z-axis servo motor 12 and outputs a signal that makes the target current to the power amplification unit 32. This is a part that supplies driving power to the servo motor 12. Next, the operation of the first embodiment will be explained according to the flowchart of FIG.

In step S1, the main spindle rotation command in the program memory 21 is read by the program interpreter 22, and in step S2, it is confirmed whether or not there is an irregular rotation command among the read main shaft rotation commands. If the answer is YES, then in step S3, the upper limit and lower limit of the irregular rotation speed designated by the program are stored in the rotation speed range storage section 23.

Next, in step S4, it is confirmed whether there is an irregular rotation start signal, and if yes, in step S5, the random number generator 24 randomly generates a random number within the range of the upper limit value and the lower limit value, A random number→rotation speed conversion unit 25 converts the random number into a corresponding rotation speed, and outputs a randomly changing rotation speed command. In step S6, the main shaft 3 is irregularly rotated at a speed as shown in the graph of FIG. In S7, it is confirmed whether irregular rotation is in progress, and if YES, it is confirmed in step S8 whether there is an irregular rotation cancellation command, and if NO, step S
5, the irregular rotation of the main spindle 3 is continued, and cutting is continued with the cutting feed of the tool post 15 synchronized with the main spindle.

If the answer is YES in step S8, it is checked in step S9 whether there is a spindle stop command, and if the answer is YES, the process ends.

Further, if the answer is NO in step S2, and if the answer is NO in step S4, step S6
, spindle 3 is rotated according to the rotation speed command specified by the program.
is rotated at a constant rate, and normal cutting is performed by the cutting feed of the tool post 15. Then, if the result in step S7 is NO, and the process jumps to step S9, and the result in step S9 is also NO, the process returns to step S4. If the result in step S4 is also NO, the process is sent to step S6, and the main spindle is Constant speed rotation continues, and normal cutting continues with the cutting feed of the tool post 15. In addition, if the result in step S7 is NO, the process jumps to step S9, and if the result is YES in step S9, the process ends. If the result is NO in step S9, the process returns to step S4, and if the result is YES in step S4, irregular rotation occurs. Switch to

Next, a second embodiment will be described with reference to FIGS. 4 and 5.

Note that the difference between the first embodiment in FIG. 4 and FIG.
Since the other parts are the same, the same parts will be given the same reference numerals and the explanation will be omitted.

The vibration detection unit 35 inputs an output signal proportional to the vibration generated by the chatter of the sensor 36 attached to the tool post 15, and detects when the amplitude of the input signal becomes larger than a preset amplitude range. , which outputs an ON signal for irregular rotation, and outputs an OFF signal when the amplitude of the input signal becomes smaller than the amplitude range. The learning function section 37 detects the irregular rotation 0 sent from the vibration detection section 35.
This is a part where the N-OFF signal is inserted into the fifth position 1 of the machining program and stored in the subprogram memory 38.

Next, the operation of the second embodiment will be explained. In addition, the first
In order to avoid duplicating the explanation of the operation of the embodiment, the explanation will focus on the operation of cutting.

Now, the material of the first workpiece W is gripped by the gripping jaws of the spindle chuck 8, its tip is supported by the 6-push center 9, and the turret 19 is rotated to index the outside diameter cutting tool TA to the cutting position. , due to the movement of the tool post 15 on the X and Z axes)
The cutting edge of A is positioned at the cutting start position.

After the spindle rotation command is read from the NC program memory 21 and the spindle rotates at the rotation speed specified by the program, the cutting feed command in the Z-axis direction is read and the tool rest 1 is rotated.
5 moves to the spindle side and outer diameter cutting is started. As the outer diameter cutting progresses and the cutting position approaches the center of the workpiece W and chatter occurs, the amplitude of the output signal of the sensor 36 increases,
When the cutting position approaches the spindle, the vibration subsides and the amplitude of the sensor output signal becomes smaller. The graph in FIG. 5 shows the output signal of this sensor 36. When the amplitude exceeds the set width, the irregular rotation ON signal is output, and when the amplitude falls below the set width, the irregular rotation starts. An OFF signal is output. This ON-OFF signal is input to the learning function section 37,
The learning function section 37 inserts this into the machining program, and the machining program for the irregular rotation 0N-OFF signal is stored in the subprogram memory.

The machining of the first workpiece W is completed, and the next workpiece W is N.
When the machine is attached to a C lathe and the start button switch is pressed, the machining program in the subprogram memory 38 is read instead of the program memory 21, and outer diameter machining is started. When the outer diameter cutting position enters the chatter region, an irregular rotation ON signal is output, and the spindle 3 is rotated at an irregular rotation speed that changes randomly within a predetermined speed range.
The tool rest is moved at a cutting feed rate that is synchronized with this irregular rotation, suppressing resonance and performing vibration-free cutting. When the vehicle passes through the chatter region, an irregular rotation OFF signal is output and the speed is switched to a constant speed.

Next, in the case of deep grooving work using TH (wide grooving pie), a sensor 36 detects vibrations that occur during cutting feed of the tool post 15 toward the workpiece in the X-axis direction during grooving of the initial workpiece.
is detected and compared with the amplitude width preset in the vibration detection unit 35, and an irregular rotation ON signal is output at the entrance of the chatter area, and an irregular rotation OFF signal is output at the exit of the chatter area. do.

The learning function section 37 inserts this 0N-OFF signal into the machining program and stores it in the subprogram memory 38. From the 0th time onwards, the irregular rotation 0N-OFF signal is stored in the subprogram memory 38 instead of the program memory 21.
The machining program containing the FF signal is read, the main spindle 3 is rotated irregularly in the area where chatter occurs, and in synchronization with this, the cutting feed of the tool post 15 in the X-axis direction is performed to suppress the occurrence of resonance and eliminate chatter. The main shaft returns to constant rotation when it is out of the chatter area.

Next, the third embodiment will be explained with reference to FIG. 6.

The difference between the third embodiment and the second embodiment is part 0 instead of part B, which has an OFF command output part 39 instead of the learning function part 37 and subprogram memory 38, and the vibration detection part 35 is irregular. Since the other parts are the same except that only the rotation ON command is output, the explanation will be omitted.

The operation of the third embodiment is such that the sensor 36 detects chatter, the vibration detection unit 35 outputs an irregular ON signal, irregular rotational speed cutting is started, the chatter subsides, and the vibration element is detected in the signal of the sensor 36. The irregular rotational speed continues even if the rotation speed is stopped, and after the cutting feed axis has been positioned and stopped, the program interpretation unit 2
When the next step command is issued from 2, the OFF command output section 39
The irregular rotation OFF command is issued and the irregular rotation is canceled. Therefore, there is no need to predict in advance the areas where chatter is likely to occur and include an irregular rotation ON-FF signal in the machining program.Chattering during machining is detected from the first product and irregular rotation is automatically executed. do.

Incidentally, the first embodiment, the second embodiment, and the third embodiment are all NC.
Although the explanation has been given using the outer diameter cutting and grooving cutting using a lathe as an example, it is natural that the irregular rotational speed machining of the present invention can also be applied to deep hole drilling using a boring bar, and in this case, a machining center is used. It can also be applied to deep hole drilling.

Effects of the Invention Since the present invention is configured as described above, it produces the following effects.

According to the first aspect of the present invention, the spindle rotation speed at locations where chatter is likely to occur during cutting is changed irregularly within a preset speed range, so that it is possible to cut the outer diameter of a long workpiece or deep groove of a wide groove. Unstable machining that is prone to chatter, such as deep hole machining using deep cutting or boring bars, etc. can be easily suppressed using only NC software, without the need for special equipment or tools such as steady rests or anti-vibration cutting tools. This enables stable machining.

According to a second aspect of the present invention, a sensor detects the location where chatter occurs during cutting of the first item, stores the location where chatter occurs in the machining program using a learning function, and presets the spindle rotation speed at the location where chatter occurs from the next cutting operation. Since machining is performed at an irregular rotation speed that changes irregularly within the specified speed range, it is possible to completely respond to unpredictable locations where chatter occurs, making it possible to perform more stable machining. .

According to a third aspect of the present invention, irregular rotation of the main shaft is started when the sensor detects chatter during cutting, and when the feed shaft is positioned and stopped and the next block command is issued, the irregular rotation is canceled. , irregular rotation is automatically executed when chatter begins to occur during machining, making it easier to create machining programs, and since irregular rotation is executed from the initial product, it is suitable for small workpieces. effective.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the NC control system including a structural diagram of a part of the lathe of the first embodiment, Fig. 2 is a flowchart for explaining the operation of the first embodiment, and Fig. 3 shows irregular rotational speed. Graph diagram, Figure 4 is a block diagram of the NC control system including a structural diagram of a part of the lathe of the second embodiment, Figure 5 is a graph diagram showing the chatter detection signal of the sensor, and Figure 6 is the third embodiment. FIG. 2 is a block diagram of the NC control system including a partial lathe structure diagram. 3...Main axis 15...Turret post 23...Rotation speed range storage section 24...Random number generation section 26...Function generation speed control section 35...Vibration detection section 3G...Vibration sensor 37...Learning I! Function section 39...OFF command output section Fig.

Claims (3)

[Claims] (1) An irregular rotational speed cutting method characterized by irregularly changing the spindle rotational speed at a location where chatter is likely to occur during cutting within a preset speed range. (2) Detecting the location where chatter occurs in advance with a sensor, storing it in the machining program using a learning function, and irregularly changing the spindle rotation speed at the location where chatter occurs from the next cutting process within a preset range. An irregular rotational speed cutting method characterized by: (3) An irregular rotational speed cutting method characterized by detecting the occurrence of chatter during cutting using a sensor and irregularly changing the spindle rotational speed within a preset speed range.