JPS6159862B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting chatter vibrations occurring during cutting. The conventional method for machine tools has been to directly detect vibrations in the machine body by attaching a vibration detection pickup directly to the machine body, such as the spindle head or tool rest.

However, the conventional method only detects the vibration state of the machine body, and it was possible to detect chatter vibrations that occur when cutting exceeds the dynamic rigidity limit of the machine. However, it has been difficult to detect chatter vibrations with relatively high frequencies caused by insufficient rigidity of workpieces and tools with conventional pickups that are directly attached to the machine body. In other words, conventionally it has been difficult to detect crack vibrations caused by workpieces or tools for purposes such as monitoring cutting conditions or adaptive control, especially in machining centers where the workpiece is on an index table. It is conceivable to extract minute signals through a slip ring or the like, but this method would be expensive and would have problems with reliability, so it could not be considered a practical method. Furthermore, even if it is possible to attach the pick-up directly to a workpiece or tool, this method involves attaching it to a movable body, which is a harsh cutting environment, and there is a risk of damaging the pick-up, resulting in structural limitations. Therefore, it lacks reliability and cannot be called a practical method. Therefore, it was not possible to obtain reliable detection results as to whether the workpiece or tool was normal or not.

The present invention has been made in view of the above circumstances.According to the present invention, detection is performed using a simple device at a position far from the cutting location, and in a non-rotating part that is not affected by the adverse environment associated with cutting. This method is simple, low-cost, and reliable, and overcomes the drawbacks of the conventional method. That is, the present invention detects the vibration of a resonance plate that resonates in a correlation with the cutting vibration of a workpiece or a tool, and by using the resonance plate, it is possible to perform machining with a comparatively simple configuration and an amplifying effect. The point is that it is a method for indirectly detecting chatter vibration of objects and tools.

The details of the present invention will be explained below with reference to the drawings.

FIG. 1 shows an embodiment applied to a boring and milling machine. A column 2 is placed on a T-shaped bed 1 so as to be slidable in the X direction. A guide path 3 is provided in the column 2 in the vertical direction, and a spindle head 4 is mounted so as to be slidable in the Y direction. A rotatably supported spindle 5 is horizontally provided on the spindle head 4, and a tool 6 is attached to the end of the spindle 5. On the other hand, a saddle 7 is placed on the guide path 1A on the bed 1 so as to be slidable in the Z direction orthogonal to the moving direction X of the column 2 and the moving direction Y of the spindle head 4. In this embodiment, the feed in each of the X, Y, and Z directions is controlled by a motor via a ball screw (not shown). A table 8 is incorporated into the saddle 7 so that it can be indexed, and when indexed to a predetermined position, the saddle 7 and the table 8 are fixed together.

The workpiece 1 is attached to the table 8 via a fixture 9.
0 is attached.

The relative movement of the tool 6 with respect to the workpiece 10 is based on movement in the three directions, ie, the X, Y, and Z directions described above. Further, the tool 6 and the fixture 9 are connected to the workpiece 1.
It has a configuration that can be changed if 0 changes.

A sounding plate 11 is attached to the side surface of the saddle 7. Ideally, the resonance plate 11 should be attached to a part close to the actual cutting condition, but as mentioned above, the attachment location is limited because it depends on the cutting environment. In this embodiment, the saddle 7 is mounted at the position shown in FIG. 1 because it is capable of reciprocating movement only in the Z direction and to protect it from the harsh environment associated with cutting. A pickup 12 for detecting vibrations is attached to a portion of the resonance plate 11 where resonance is likely to occur. A lead wire from the pickup 12 is connected to a vibration meter 13 to transmit the vibration state of the resonance plate 11.

The resonance plate 11 is a thin steel plate (for example, about 1 mm),
A material with a relatively large area is used so that resonance points can be detected even when processing conditions change, and it resonates over the entire frequency range. Although the shape and material of the resonance plate 11 are not particularly limited, it is more effective to avoid a symmetrical shape and to reduce the peak of the resonance width in order to avoid the resonance frequency as much as possible.

In the vibration meter 13, the transmitted vibration, that is, the vibration signal transmitted in the form of acceleration, is amplified and further outputted as a voltage proportional to the amplitude through a double integration circuit. Next, this detected output signal is applied to the Schmitt circuit 14 and compared with a set upper limit value or lower limit value. This Schmitt circuit 1
4 outputs a stop signal when a voltage exceeding a certain limit value is input. Furthermore, this output stop signal is applied to the machine stop circuit of the machine controller 16 via the interface 15 to stop the operation of the machine, that is, stop the rotation of the motor, etc.

FIG. 2 shows a specific configuration in which the resonance plate 11 is attached to the saddle 7. Sound board 11
It has a simple structure and is attached to the saddle 7 with bolts 17.

FIG. 3 shows an example showing experimental values when a pickup 12 for direct vibration detection is attached to the workpiece 10 and the sounding plate 11 and cutting is performed under four types of cutting conditions.
That is, in contrast to the cutting conditions shown below in Fig. 3, the detected values at two locations under the cutting conditions are plotted, with the vibration amplitude of the resonance plate 11 on the slave axis and the vibration amplitude of the workpiece 10 on the horizontal axis. This is what I did.

The vibration amplitude of the workpiece in this experimental example was measured under experimentally settable conditions. That is, the measured values were obtained by not indexing the table and by mounting the pick-up in a position protected from flying chips, but this method of mounting is effective in practical use, and the cutting conditions do not differ from the experimental values. As is clear from FIG. 3, there is a clear correlation between the detected values at two locations on the workpiece 10 and the resonance plate 11, as shown in the direction along the two-dot chain line, and the method of the present invention This correlation is used. After all, if the detected value of the vibration of the sounding plate 11 attached to the saddle 7 is known, the vibration value of the workpiece 10 can be determined without measuring the vibration value of the workpiece 10, and the vibration value of the sounding plate 11 can be used to determine the vibration value of the workpiece 10. thing 10
The point is that it can be substituted for the vibration value of . The difference in the vibration direction of the cutting point is detected by the vibration of the sounding plate 11 in the same direction, which is practically no problem. It is well known that chatter vibrations are generally much larger than vibrations in normal cutting conditions. Therefore, the present invention provides the resonance plate 1
A pick-up 12 attached to the machine constantly detects the vibration state, and when the vibration value exceeds a certain set tolerance value, that is, the limit value of the dynamic stiffness of the machine, the machine is stopped and the machine, tools, and workpieces are The goal is to prevent damage from becoming more serious. Furthermore, although it is common practice to attach a pickup to the machine body to detect the vibration state, it is difficult to directly detect the chatter vibration itself that occurs in the relative relationship between the tool and the workpiece.

According to the method of the present invention, chatter vibration can be detected relatively simply. In carrying out the present invention, a more accurate crack vibration detection state can be obtained by performing the correlation between the workpiece and the sounding plate based on a large number of data in accordance with each machine configuration. Further, the mounting of the resonance plate 11 is not limited to only on the saddle 7.

The present invention is applicable not only to the above-described embodiments but also to a turning machine or the like, in which crack vibrations in the cutting state can be detected in a similar manner by attaching a sounding plate to the carriage of the tool rest.

As described above, the present invention is not limited to the configurations shown in the embodiments, and modifications are expected without departing from the technical idea of the present invention as described in the claims.

[Brief explanation of the drawing]

Figure 1 is a system diagram of vibration detection implementing the present invention.
Fig. 2 is a structural diagram with a sounding plate attached, and Fig. 3 is a diagram showing the correlation between experimental vibration amplitudes of the workpiece and the sounding plate. In the figure, 1...Bed, 2...Column, 4
...Spindle head, 6...Tool, 7...Saddle, 9...
Fixture, 10... Workpiece, 11... Resonance plate, 12
...Pick up.

Claims (1)

[Claims] 1. In detecting cutting vibration of a machine tool, a sounding plate is attached to a movable base that moves the workpiece or tool, and a detector is installed on the sounding plate to detect the cutting vibration state of the workpiece or tool as the vibration state of the sounding board. The vibration value detected from the resonance plate is compared with a comparison value set in advance based on the correlation with the vibration of the workpiece or tool, and the comparison result is sent to the control circuit to control the machine based on the detection result. A method for detecting vibration of a machine tool, characterized in that the vibration is controlled by