JPH0725015B2 - Feed rate control device for cutting machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a feed rate control device for a cutting machine,
Particularly, it relates to improvement of feed rate control in the case of including both rough cutting and finish cutting.

[Prior Art] In cutting machines for press dies,
With the expansion of NC from cutting to cutting tool exchange and setup, continuous unmanned operation has been performed for a long time. Then, in order to improve the efficiency of cutting by such continuous unmanned operation, it is necessary to shorten the time required for machining per die. The following is performed as a method of this efficiency improvement.

Detects the time when the cutting tool is actually cutting the material to be cut (during actual cutting) and the time when it is not actually cutting (during empty cutting), and increases the feed rate during empty cutting, Shortening the machining time Detects the current value of the spindle motor that rotates the cutting tool in the cutting machine and controls the feed speed of the work piece by changing this current value to shorten the machining time. The determination using the AE sensor can be performed by, for example, Japanese Patent Laid-Open Nos. 61-159354 and 57-1734.
62 have been proposed.

[Problems to be Solved by the Invention] The conventional technology as described above has the following problems.

The method using the spindle current sensor cannot identify a minute load because the spindle motor has a large rotational inertia.
Therefore, in cutting such as a press die in which rough cutting and finish cutting are mixed, it is very difficult to identify the blank cutting, the actual cutting, and the load variation during the finish cutting.

The AE sensor is generally used in the band where the frequency characteristic is not flat, and its characteristic is not sufficiently clarified, so it is not used for the discrimination of the load fluctuation, and it is not used for the discrimination of the blank cutting and the actual cutting. It was used only as an on / off signal.

The present invention has been made in order to solve such a problem, and relates to a cutting machine capable of significantly shortening the processing time in a long-time continuous unmanned operation of a cutting machine in which rough cutting and actual cutting are mixed. An object is to provide a feed rate control device.

[Means for Solving Problems] The feed rate control device in the cutting machine according to the present invention is
In a die cutting machine for rough cutting and finish cutting a material to be cut by a cutting tool, a feeder for relatively moving the material to be cut and a spindle current sensor for detecting a current of a spindle motor for rotating the cutting tool. From the AE sensor attached to the cutting machine, the bandpass filter that extracts the AE sensor output value in the predetermined frequency band from the detection value obtained by this AE sensor, and the AE sensor output value and the spindle current sensor Both the spindle current value of the main input is input and the AE sensor output value is used to distinguish between blank cutting and actual cutting.The spindle current value is used for feed rate control during rough cutting during actual cutting, and AE is used during finish cutting during actual cutting. And a feed rate controller that controls the feeding device by using a sensor output value.

[Operation] The feed rate control device in such a cutting machine is
It works as follows.

The material to be cut and the cutting tool are relatively moved by the feeding device. Then, the material to be cut is cut by a cutting tool that rotates while performing this movement. At this time, the current value of the spindle motor that rotates the cutting tool is detected by the spindle current sensor,
The AE generated during cutting is detected by the AE sensor. Then, the detection value of the AE sensor is converted into an AE sensor output value in a predetermined frequency band by the bandpass filter. The spindle current value obtained by the spindle current sensor and the AE sensor output value are input to the feed speed controller. The feed rate controller uses the AE sensor output value to distinguish between rough cutting and actual cutting. In addition, the spindle current value is used during actual cutting during rough cutting, and the feed rate is controlled using the AE sensor output value during actual cutting during finish cutting.

[Embodiment] Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows the entire configuration of a system having a feed rate control device in a cutting machine according to the present invention. The work material 10 is placed and fixed on the table 12. The cutting tool 14 is connected to an output shaft of a spindle motor 18 via a spindle head 16 fixed to a machine frame (not shown) or the like. The feed motor 20 moves the table 12 in one axis (X axis in the figure, front and rear) direction and the spindle head 16 in two axes (Y, Z axis in the figure, left and right up and down) direction. And the AE sensor is on the table 12.
22, a spindle current sensor 24 is attached to the spindle motor 18. The AE processor 26 processes the AC waveform AE detection signal a obtained by the AE sensor 22 and converts it into a DC waveform AE sensor output value b. Feed rate controller 28
Includes an AE sensor output value b from the AE processor 26, a spindle current value c from the spindle current sensor 24, and a machine controller.
The cutting tool information and the like from 30 is input, and the feed rate coefficient k is output. The machine controller 30 receives the cutting tool information and the like from the NC controller 32, and outputs this to the automatic cutting tool changer (ATC). The machine controller 30 also transfers the feed speed coefficient k from the feed speed controller 28 to the NC controller 32. NC controller
An NC program including locus information, feed command value, cutting tool information and the like is input to 32 and is supplied to the machine controller 30 and the feed motor servo unit 34. Also,
The NC controller 32 feeds a speed instruction value v obtained by multiplying the feed speed coefficient k input from the machine controller 30 by the feed command value in the NC program.
Supply to. The feed motor servo unit 34 controls the speed of the feed motor 20 based on the speed instruction value v.

In such a cutting system, when the NC program is supplied to the NC controller 32, a predetermined cutting process is performed based on the NC program.
The feed rate is changed by the AE sensor output value b and the spindle current value c.

Here, the AE detection signal a by the AE sensor 22 will be described first. The AE detected by the AE sensor 22 is an abbreviation for Acoustic Emission, which is a "phenomenon in which energy released due to deformation and destruction of a solid becomes an acoustic pulse and propagates". Here, as a cause of AE when the material to be cut is cut by the cutting tool, the material to be cracked, the plastic deformation of the material to be cut in the sheared surface, the friction between the material to be cut and the cutting tool, the breaking of chips, Possible causes include collision between chips and a material to be cut or a cutting tool, elastic waves generated by collision between a cutting tool and a material to be cut, chatter between the cutting tool and the material to be cut, and the like. The AE generated due to such causes is the AE sensor 22.
Detected in. AE detection signal a obtained by this AE sensor 22
Is repeated up and down according to the vibration, and the amplitude represents the magnitude of the vibration. 2A and 2B show an example of the result of frequency analysis of the AE detection signal a. Here, FIG. 2A
Is for actual cutting, and FIG. 2B is for blank cutting. Thus, the AE detection signal a at the time of actual cutting has a peak in the frequency band of 50 to 80 kHz, and at the time of idle cutting, it has a peak in the frequency band of 50 kHz or less. From this, the AE generated by cutting
Shows that the frequency is in the band of 50-80kHz. The peak during idle cutting is caused by table feed and the like. Further, the AE detection signal a obtained by the AE sensor 22 becomes an AC waveform signal which intermittently repeats the maximum of the amplitude according to the frequency with which the cutting tool collides with the material to be cut. For example, 2
2 minutes for 1 minute when rotating a single-blade tool at 1000 rpm
The AC waveform has a maximum value of 000 times.

The AE detection signal a obtained by such an AE sensor 22 is input to the AE processor 26, and the processing shown in FIG. 3 is performed. That is, the AE detection signal a has an amplification ratio of 20-40.
It is amplified by a preamplifier (AMP) that can be switched between several dB. And low pass filter (LPF)
The signal of 80kHz or more is cut by the high pass filter (H
The signal below 50kHz is cut by PF), and only the signal of 50k to 80kHz is extracted. Then, the signal of the specific frequency is amplified again by the intermediate amplifier (AMP) and then detected by both waves. This detected signal is input to a peak hold circuit (peak hold), where the maximum values are sequentially held. The above processed values are smoothed by a smoothing circuit (smoothing) and then input to the feed speed controller 28 as an AE sensor output value b of a DC waveform.

Further, the spindle current sensor 24 supplies the current value of the spindle motor 18 to the feed speed controller 28 as the spindle current value c.
FIG. 4 shows an example of the AE sensor output value b, which is the output value of the AE processor 26, and the spindle current value c, which is the output value of the spindle current sensor 24, when the flat plate-shaped workpiece 10 is cut. Fourth
As is clear from FIG. A, the AE sensor output value b becomes large when the cutting tool starts to contact the work material and when the cutting tool separates from the work material. That is, this signal becomes maximum at the start and end of cutting. Therefore, it can be seen that the response to the change between the blank cutting and the actual cutting is very good, which is very suitable for this discrimination. Further, it can be seen from FIG. 4B that the spindle current has a very poor response to the change between the blank cutting and the actual cutting and is not suitable for this discrimination.

Further, as shown in FIG. 4A, in the case of a flat work material, the AE sensor output value b corresponds to the magnitude of the load during actual cutting. Therefore, the relationship between the cutting load and the AE sensor output value b is shown in FIG. This is a plate-shaped material cut with a ball end mill with a diameter of 10 mm. In this way, in the case where the feed rate is 200 to 1000 mm / min, the AE sensor output value b increases as the depth of cut increases. Further, in the case where the depth of cut is 0.5 to 2.0 mm, the AE sensor output value b also increases as the feed speed increases. From this, the AE sensor output value b is
It turns out that there is a positive correlation. This is considered to be because the scale of AE generation increases with an increase in the depth of cut and the feed rate, and it can be seen that the AE sensor output value b can be used for feed rate control if appropriate signal processing is performed. Such characteristics can be obtained by investigating the frequency of AE according to the material of the material to be cut by frequency analysis and determining the frequency band to be extracted by this. The frequency band of 50k ~ 80kHz in this example is a general value when the work material is made of cast iron,
For example, in the case of steel materials, a range of several kHz to 20 kHz is selected. The upper and lower limit frequencies of the bandpass filter composed of the lowpass filter and the highpass filter in the AE processor 26 are also included in the NC program, and may be automatically set according to the material of the material to be cut. Good.
The feed rate controller 28 was obtained in this way
In addition to the AE sensor output value b and the spindle current value c being input, the machine controller 30 also inputs the cutting tool classification information.
Then, the feed speed controller 28 calls a set value to be compared with the AE sensor output value b or the spindle current value c, based on the cutting tool information. Here, the set value is composed of an upper limit value, a lower limit value, an idle cutting determination value, etc., which are preset according to the type of cutting tool, and is stored in a memory built in the feed speed controller 28, for example, a nonvolatile memory such as a bubble memory. Has been called and is called at any time. It should be noted that it is possible to determine whether the current cutting is rough cutting or finish cutting depending on the type of cutting tool, but this type may be used as independent information. Furthermore, the AE sensor output value b or the spindle current value c
It is also possible to constantly monitor the magnitude of the value and automatically adopt the value that gives the appropriate value.

The cutting process usually starts with blank cutting. Therefore, the feed speed controller 28 compares the AE sensor output value b with a predetermined idle cutting determination value equal to or higher than a predetermined noise level in the initial state. Since the initial blank cutting is performed, the AE sensor output value b is smaller than the blank cutting determination value, and the blank cutting is identified. Then, the feed rate coefficient k corresponding to the time of blank cutting is called. The feed rate coefficient k in the case of dry cutting is, for example, a value of 1.0 or more, which is 2.0 (the maximum speed coefficient). The feed speed coefficient k is input to the NC controller 32 via the machine controller 30 and is multiplied by the feed command value included in the NC program to obtain the feed speed instruction value v. That is, a value twice the feed command value is the feed speed instruction value v
Is supplied to the feed motor servo unit 34, and the feed motor 20 feeds the table 12 at a speed twice the feed command value.
Next, when the AE sensor output value b exceeds the predetermined idle cutting determination value and it is detected that the actual cutting has started, the object of comparison performed by the feed controller 28 is changed. That is, when the cutting at that time is rough cutting, the cutting load at that time is detected by the spindle current value c, and a signal that the feed speed becomes an appropriate speed is output. That is, when the spindle current value c is larger than the predetermined upper limit value, the cutting load is high, so the feed rate coefficient k is gradually decreased until the spindle current value c becomes smaller than the upper limit value. When the spindle current value c is smaller than the lower limit value, the cutting load is small. Therefore, the feed rate coefficient k is gradually increased until the spindle current value c becomes larger than the lower limit value.

In this way, at the time of actual cutting of rough cutting, the feed rate is controlled using the spindle current value c, and cutting is always performed with an optimum load. The feed rate coefficient k is normally changed within the range of 0.5 to 2.0 and is not changed any more. This is because a large change does not adversely affect other elements of cutting (cutting tool wear / damage, cutting surface accuracy / roughness). For example, if the feed rate is too fast and the load suddenly increases, the cutting delay may cause damage to the cutting tool. In such cases,
If the maximum speed is set according to the strength of the cutting tool and the control delay time, damage to the cutting tool can be prevented. Next, when the AE sensor output value b falls below a predetermined blank cutting determination value, it is identified that the blank cutting has been performed, and the feed speed controller 28 determines that the feed speed coefficient k during the blank cutting is 2.0 (maximum). The speed coefficient) is output, and the feed speed is set to the corresponding high speed.

During finish cutting, the AE sensor output value b is also used to detect the cutting load during actual cutting. That is, at the time of finish cutting, the depth of cut is minute and the cutting load is relatively small. Therefore, the spindle current does not sufficiently respond to the cutting load and cannot be used as a cutting load detecting means. The AE sensor output value b shows a good response to the cutting load when the load is small as in the finish cutting, as shown in FIGS. 4 and 5. The control method is the same as in the case of the spindle current. That is, the AE sensor output value b is compared with the upper limit value and lower limit value for finish cutting that are stored in advance. If the upper limit value is exceeded, the feed speed coefficient k is increased, and if the lower limit value is exceeded, the feed rate coefficient k is increased. Lower the speed coefficient k.

Next, the operation in the case where the cutting is actually performed using the material to be cut having the specific shape will be described with reference to FIG. Fig. 6A
The shape of the work material 10 used for this processing is shown in FIG. In this way, it has a three-stepped shape, and the steps are 0.4 mm each. The cutting tool is a ball end mill with a diameter of 10 mm, which moves horizontally from left to right in the drawing with a depth of cut of 0.4 mm and a feed rate command value of 200 mm / min. Therefore, the depth of cut is 0.4, 0.8, 1.2,
It changes in the order of 0.8 and 0.4 mm. At the time of idle cutting, the AE sensor output value b is sufficiently lower than the idle cutting determination value for distinguishing between idle cutting and actual cutting, and it is identified as idle cutting. Therefore, the feed rate coefficient k is set to its maximum value of 2.0, and the feed rate instruction value v is set to a rate twice the feed rate command value. Next, when it is determined from the AE sensor output value b that actual cutting has started, the feed rate coefficient k is once set to 1.0, and cutting is performed with the feed rate command value inserted in the NC program. After that, when the AE sensor output value b is below the lower limit value, the feed rate coefficient k increases, and in this example, in the first step cutting, it increases to the maximum value of 1.5 during actual cutting. Then, the second stage cutting is started at this speed. Then, because the load increases, the AE sensor output value b exceeds the upper limit value, and the feed rate count is reduced to about 0.9. And A
The E sensor output value b is between the upper limit value and the lower limit value of the set value. Next, when the cutting tool enters the third step, the AE sensor output value b again exceeds the upper limit value, and the feed rate coefficient k is reduced. Then, it is set to the minimum value of 0.5. Even when the cutting tool further moves and the load gradually increases, the feed rate control is similarly performed following the load.

Further, when the feed rate controller identifies that the cutting is actual cutting, this actual cutting time is counted by a timer (not shown). Then, this time is accumulated for each cutting tool. Since the service life of each cutting tool is known, if the actual cutting time reaches this service life, the machine controller 30 will send ATC (Automatic
Tool Changer) is issued a command to automatically replace the cutting tool.

According to the device of this embodiment, the following effects can be obtained.

The feed rate is set to the maximum speed during idle cutting, and the feed time during idle cutting can be shortened.

At the time of actual cutting, rough cutting and finish cutting are discriminated by cutting tool information. Then, during rough cutting, the feed rate is controlled by the magnitude of the spindle current value, and the feed rate is controlled by the AE sensor output value. Therefore, accurate feed rate control can always be performed even in cutting with a press die or the like in which rough cutting and finish cutting are mixed.

Since the detection value of the AE sensor is in the specific frequency band by the bandpass filter, the signal according to the cutting load can be stably extracted.

The frequency band extracted by this bandpass filter is changed according to the type of material to be cut.
You can always perform optimal cutting.

[Advantages of the Invention] As described above, according to the feed rate control device in the cutting machine of the present invention, the actual cutting is performed according to the load of the cutting tool even in the cutting work on the press die in which rough cutting and finish cutting are mixed. Since the optimum feed speed can be achieved and the predetermined high speed can be achieved during idle cutting, the effect of efficiently performing long-term continuous unmanned operation of the cutting machine can be obtained.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an outline of a system of an example of a feed rate control device for a cutting machine according to the present invention, FIG. 2 is a waveform diagram showing frequency characteristics of AE sensor output values, and FIG. Fig. 4 is a block diagram showing the contents of the processor, Fig. 4 is a waveform diagram showing an example of the AE sensor output value and spindle current value when cutting the workpiece, and Fig. 5 shows the AE sensor output value with respect to the cutting depth and feed rate. FIG. 6 is an explanatory diagram showing the shape of the material to be cut, the AE sensor output value, and the feed rate during cutting. 10 …… Material to be cut, 12 …… Table, 14 …… Cutting tool, 18 ……
Spindle motor, 20 ... Feed motor, 22 ... AE sensor, 24 ...
… Spindle current sensor, 26 …… AE processor, 28 …… Feed speed controller, 30 …… Machine controller, 32 …… NC
Controller, 34 ... Feed motor servo unit.

Claims (1)

[Claims] 1. A cutting machine for rough-cutting and finish-cutting a material to be cut by a cutting tool, which is a current value of a feed device for relatively moving the material to be cut and a spindle motor for rotating the cutting tool. A spindle current sensor that detects the spindle current value, an AE sensor attached to the cutting machine, and a bandpass filter that extracts the AE sensor output value that is a signal in a predetermined frequency band from the detection value obtained by this AE sensor. Both the AE sensor output value and the spindle current value are input.The AE sensor output value is used to distinguish between blank cutting and actual cutting, and the spindle current value is used for feed speed control during rough cutting during actual cutting. And a feed speed controller for controlling the above-mentioned feeding device by using the output value of the AE sensor during the finish cutting in the actual cutting, and the feed speed in the cutting machine. The control device.