JP2000061779A - Machine tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a machine tool capable of certainly avoiding chattering vibration in the middle of machining with trial and error without depending on skill of a worker. SOLUTION: This machine tool is furnished with a tool 7 to machine a work piece OB, a main spindle 9 free to rotate to support this tool 7, an acceleration pickup device 21 set on this main spindle 9 and to detect information concerning acceleration of the main spindle 9 by converting it to an electric signal, a signal amplifying circuit 22 to amplify the electric signal detected by this acceleration pickup device 21, a vibration discriminating circuit 23 to discriminate generation of chattering vibration by frequency-analyzing the electric signal amplified by this signal amplifying circuit 22 and a damping system 30 to supply a damping damper material 30a to a space part 31 in the tool 7 through a main spindle draw bar joint in the main spindle 9 and a conduit run 32 passing through a tool holder 8 at the time when generation of chattering vibration is discriminated by this vibration discriminating circuit and to control supply quantity of this damping damper material 30a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a machine tool such as an NC machine tool, and more particularly to "chatter" generated during machining.
Regarding devising measures to suppress vibration.

[0002]

2. Description of the Related Art Conventionally, N represented by a machining center
In the C machine tool, as a countermeasure when chatter vibration occurs during machining, the machining conditions such as motor rotation speed are changed,
Increase the rigidity of the work piece, tool, jig to change its natural frequency, add a configuration to pick up the vibration of the tool and actively perform damping, and use different materials for the tool materials with different natural frequencies. And the like are implemented.

[0003]

However, the above-mentioned method of changing the processing conditions is usually an empirical work involving trial and error in many cases, which strongly depends on the skill of the operator, and the effect thereof is also large. I'm not sure. Further, it is difficult to accurately grasp the directionality of the method by increasing the rigidity of the workpiece, the tool, and the jig to increase the natural frequency of the jig. Furthermore, in the method of changing the mass of the tool, the dynamic balance of the tool is often lost, which is not particularly suitable for recent high-speed machining. In the method of applying a superhard material as the material of the tool core, the rigidity is increased, but on the contrary, there is a disadvantage that the effect of suppressing chatter vibration is limited.

In any of the methods, the measure for avoiding chatter vibration generally takes time, and there are many cases in which production is interrupted, which causes a problem in continuous automatic processing.

The present invention has been made in consideration of such conventional problems, and provides a machine tool capable of reliably avoiding chatter vibration during machining without trial and error regardless of the skill of the operator. With the goal.

[0006]

In order to achieve the above object, a machine tool according to the invention of claim 1 is a machine tool for machining a workpiece, and a rotatable spindle supporting the tool. An acceleration pickup device which is installed on the main shaft and converts the information about the acceleration of the main shaft into an electric signal for detection, a signal amplification means for amplifying the electric signal detected by the acceleration pickup device, and an amplification by the signal amplification means. And a vibration identifying unit for identifying the occurrence of chatter vibration by frequency-analyzing the generated electric signal.

According to a second aspect of the present invention, in the first aspect of the present invention, a vibration damper for supplying a vibration damper material to the inside of the tool when the occurrence of the chatter vibration is identified by the vibration identification means. It is characterized by further comprising a material supply means and a means for controlling the supply amount of the vibration damper material by the vibration damper material supply means.

According to a third aspect of the present invention, in the second aspect of the present invention, the vibration damping damper material supplying means is means for supplying the vibration damping damper material to the inside of the tool via the main shaft. It is characterized by having.

According to a fourth aspect of the present invention, in the third aspect of the present invention, a tool holder for holding the tool is provided, and the damping damper material supply means includes the main shaft and the tool holder attached to the main shaft. It is a means for supplying the damping damper material to the inside of the tool via the above.

According to a fifth aspect of the present invention, in the fourth aspect of the present invention, the spindle includes a spindle drawbar and a joint that connects the spindle drawbar and the tool holder to each other, and the vibration damper material supply means. Is means for supplying the vibration damping material to the inside of the tool via the draw bar, the joint, and the tool holder.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a machine tool according to the present invention will be specifically described below with reference to the drawings.

The machine tool shown in FIG. 1 is an NC machine tool (for example, a horizontal machining center) applied, and has a jig (fixing table) 1 for mounting and fixing a workpiece OB, and a jig 1 for mounting the jig on the jig 1. The machine body 2 installed at a position facing the workpiece OB and the machining operation by the both 1 and 2 are N
An NC device 3 for C control is provided, and an actuator 5 such as a servomotor is operated via a spindle control circuit 4 by a machining command S1 from the NC device 3 to drive the jig 1 and the machine main body 2 so as to drive the workpiece. The workpiece OB is subjected to machining such as cutting under controlled machining conditions.

In the machine body 2, a tool 7 having a cutting tool 6 such as a cutting tool for machining an object OB placed on the jig 1, and a conical tool holder 8 for holding the tool 7.
And a rotatable main shaft 9 supporting the tool holder 8 are installed.

Of these, the main shaft 9 is provided with a shaft portion 12 rotatably supported by a bearing 11 in a cylindrical housing 10 as shown in FIG. The shaft portion 12 receives the end of the tool holder 8 on the conical top side in a tapered recess 13 formed at its tip, and the end portion of the tool holder 8 in the inserted state is passed through a joint 14 to a main shaft. It has a connection structure connectable to the drawbar 15.

The above machine tool has a vibration recognition system 20 for recognizing chatter vibration of the tool 7, and a vibration of the tool 7 for suppressing chatter vibration when the vibration recognition system 20 recognizes the chatter vibration. And a vibration damping system 30 for damping the vibration.

As shown in FIGS. 1 and 2, the vibration recognition system 20 includes an acceleration pickup 21 embedded in a housing 8 of a main shaft 7, and a signal amplification circuit 22 for amplifying a detection signal from the acceleration pickup 21. A vibration identification circuit 23 for identifying the occurrence of chatter vibration by frequency-analyzing the amplified signal from the signal amplification circuit 22 and comparing the analysis data with the data during normal processing. Chatter vibration identification data by the vibration identification circuit 23 can be stored in a memory in the NC device 3.

As shown in FIG. 2, the vibration damping system 30 includes a space 31 into which the vibration damping damper material 30a formed in the tool 9 and composed of a viscoelastic fluid can be injected and stored, and this space 31. A flow passage 32 of a vibration damper material 30a, which is formed by inserting the joint 14 and the main shaft drawbar 15 in the main shaft 7 from inside the tool holder 8 facing the above, and a vibration damper material connected to this pipe 32. Storage tank 33 for
An actuator 34 for a vibration damper material, which is a drive source of the storage tank 33, and a vibration damper material supply control circuit 35 which gives a control command S2 to the actuator 34 to control the operation thereof.

Next, the overall operation of this machine tool will be described.

First, when starting the machine tool, the NC device 3
A machining command S1 is issued to the actuator 5 via the spindle control circuit 4. The actuator 5 is driven under the processing conditions based on the processing command S1, the main shaft 9 is rotated by the power, and the rotational force is transmitted to the tool 7 via the tool holder 8, so that the workpiece OB on the jig 1 is processed. NC processing is performed.

During the NC machining, the vibration received by the tool 7 is detected by the acceleration pickup 21 embedded in the spindle 9, and the signal is amplified by the signal amplifier circuit 22,
The vibration identification circuit 23 performs frequency analysis, and the analysis data is compared with the data at the time of normal processing, whereby the presence or absence of chatter vibration is identified.

When the vibration identification circuit 23 identifies the occurrence of chatter vibration, the identification data is stored in the memory of the NC device 3, and the vibration damping damper material supply control circuit 35 uses the identification data based on the data. The supply amount of the vibration damper material 30a into the inside 7 is adjusted, and the control command S2 is issued to the actuator 34. The actuator 34 is driven under the condition based on the control command S2, and the vibration damper material 30a in the storage tank 33 is supplied by the power to the space portion 31 in the tool 7 via the pipe 32 at a controlled supply amount. As a result, the natural frequency of the tool 7 changes and chatter vibration is suppressed.

Then, the machining command S1 is sent again from the NC device 3.
Is issued, and the NC processing described above is performed. After that, the above operation is repeated to check the vibration during processing.

Therefore, according to this embodiment, chatter vibration during processing can be automatically suppressed and reliably avoided without changing the processing conditions. As a result, it is not necessary to make adjustments by trial and error depending on the skill level of the worker as in the conventional case, and workability can be greatly improved. Further, since the vibration state during machining can be automatically monitored, there is an advantage that the unmanned operation of the machine tool can be further promoted. Further, by appropriately controlling the supply amount of the vibration damping damper material, finer adjustment can be made.

The material of the vibration damper material may be arbitrary,
For example, silicone gel is preferable. Further, in selecting the material of the vibration damping damper material, it may be used together with an oil wheel type cutting fluid which supplies the cutting fluid from the inside of the tool.

Further, it is also possible to freely change the supply amount or pressure of the vibration damping damper material during processing so as to obtain the optimum natural frequency.

It is also possible to add an expert system to the NC control device, construct a database for defining the relationship between the vibration damper material supply state and the past conditions, and adopt control using this database. It is possible.

Furthermore, in designing the hardware of the vibration recognition system, in addition to the acceleration pickup device, a frequency analysis of the pickup signal is performed, and a computer capable of executing an algorithm for identifying chatter vibration from the analysis data, for example, an existing computer. It is also possible to apply a workstation (WS), a personal computer (PC), or the like.

[0028]

As described above, according to the present invention, a vibration damper material is automatically recognized in the tool when abnormalities due to chatter vibration during machining are automatically recognized. Since the natural frequency and the damping capacity of the tool are supplied to be changed, chatter vibration can be surely suppressed without changing the machining conditions, and the workability is greatly improved. In addition, since the machining conditions such as chatter vibration can be automatically monitored, unmanned machine tools can be operated.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an overall configuration of a machine tool according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view showing a spindle structure.

[Explanation of symbols]

1 jig 2 Machine body 3 NC device 4 Spindle control circuit 5 actuators 6 cutting tools 7 tools 8 tool holder 9 spindle 10 housing 11 bearings 12 Shaft 13 Tapered recess 14 joints 15 Spindle drawbar 20 Vibration recognition system 21 Accelerometer 22 Signal amplification circuit 23 Vibration identification circuit 30 vibration control system 30a Damper material 31 Space Department 32 pipelines 33 Storage tank 34 Actuator for vibration damper material 35 Vibration damper material supply control circuit

Claims (5)

[Claims] 1. A tool for processing a workpiece, a rotatable spindle supporting the tool, and an acceleration pickup installed on the spindle and converting information on acceleration of the spindle into an electric signal for detection. An apparatus, a signal amplification means for amplifying an electric signal detected by the acceleration pickup device, and a vibration identification means for identifying the occurrence of chatter vibration by frequency-analyzing the electric signal amplified by the signal amplification means. A machine tool characterized by having. 2. The vibration damper material supplying means for supplying a vibration damper material to the inside of the tool when the vibration identifying means identifies the occurrence of the chatter vibration, and A machine tool further comprising: a means for controlling a supply amount of the vibration damper material by the vibration damper material supplying means. 3. The machine tool according to claim 2, wherein the vibration damper material supplying means is means for supplying the vibration damper material to the inside of the tool via the spindle. . 4. The invention according to claim 3, further comprising a tool holder for holding the tool, wherein the damping damper material supply means is provided inside the tool via the spindle and the tool holder attached to the spindle. A machine tool characterized in that it is a means for supplying the damping damper material to the. 5. The invention according to claim 4, wherein the spindle includes a spindle drawbar and a joint connecting the spindle drawbar and the tool holder to each other, and the vibration damping damper material supplying means includes the spindle drawbar, A machine tool comprising means for supplying the vibration damping damper material to the inside of the tool via a joint and a tool holder.