JP4998140B2 - Cutting tool runout control method - Google Patents

Description

The present invention relates to a technique for suppressing runout of a cutting tool such as an end mill used for ultraprecision machining.

In recent years, the machining accuracy of machine tools such as machining centers has improved dramatically due to improvements in motion accuracy, tool shape accuracy, and development of measurement technology, but in actual machining it is difficult to reduce tool runout to zero. is there. Such runout of the cutting tool causes premature wear and machining variations.

Patent Document 1 discloses a method for detecting runout of a cutting tool. In this method, a means for detecting the position of the tool edge by means of a light beam is arranged inside the machine tool, and when the tool is rotated, the data of the position of the highest and lowest cutting edges is calculated to calculate the vibration of the tool. Is what you want.

However, even if tool run-out is detected by this method, it is necessary to repeatedly attach and remove the tool to the spindle, which takes time and is not stable. The shake remains. In addition, there is a method of using a high-precision special chuck such as a shrink fit chuck or a hydraulic chuck as a chuck (attachment portion) of the spindle to which the tool is attached, but even in this case, a vibration of about several μm remains. In addition, there is a mechanism that uses a screw to mechanically adjust the tool around the spindle, but because this mechanism is large, it can only handle large-diameter tools, and it can eliminate runout of about a few μm. Can not.
Japanese Patent Application Laid-Open No. 11-188577

Accordingly, an object of the present invention is to provide a method for suppressing runout of a cutting tool that can restrain runout with high accuracy in a non-contact manner.

In order to achieve the above object, the present invention connects a shank portion of the tool or the tool and the main shaft in a machine tool in which a tool is attached to the main shaft, the main shaft is rotated, and the workpiece is cut by the tool. Using a material that transforms by heating by laser irradiation and subsequent cooling to the coupler and causes expansion or contraction, and detects the deflection with respect to the shaft center in a state where the tool is attached to the main shaft. There is provided a method for suppressing runout of a cutting tool, wherein the material portion is irradiated with a laser, the material portion is transformed by heating and cooling thereafter, and expansion or contraction is caused to reduce runout.

In the present invention, in a state where the tool is attached to the spindle, the tool is rotated to detect the deflection. Since shake has its direction (phase) and amount, the direction and amount of shake are detected by a known method. For detection of shake, a non-contact detector or a contact detector may be used. Next, in a state where the main shaft is stopped, a laser is irradiated to a shank portion or a connecting tool of a tool using a material that is transformed by heating by laser irradiation and subsequent cooling to cause expansion or contraction. Upon irradiation with the laser, the shank or connector of the tool is heated locally, and subsequent cooling transforms the tissue and expands or contracts. Residual stress is generated due to expansion or contraction due to tissue transformation, and the deflection of the tool is corrected. Since the laser can heat the material locally at a high temperature and at a high speed, it does not unnecessarily heat a wide range, can prevent a decrease in the strength of the material, and can adjust the vibration little by little. In the present invention, it is possible to correct shake by 0.1 μm by adjusting the position, range, intensity, time, etc. of laser irradiation. As an application, it can be used to correct runout of a millimeter or submillimeter tool (end mill, grindstone) used for ultra-precision machining.

The laser irradiation part may be a shank portion of the tool or a connecting tool for connecting the tool and the main shaft. When the tool is made of a cemented carbide, the structure cannot be transformed. Therefore, the connector may be made of a material that can be transformed. For the coupling tool, for example, a component such as a sleeve integrally fixed to the shank portion of the tool by shrink fitting or the like can be used.

As a preferred embodiment, the material portion that is transformed by laser irradiation may be formed of a steel material, heated to an austenite structure by laser irradiation, and rapidly martensitic transformed by quenching. Alternatively, the pearlite transformation may be performed by heating to an austenite structure by laser irradiation and slow cooling. In the former case, it expands due to tissue transformation, while in the latter case, it contracts due to tissue transformation.

As described above, according to the present invention, the vibration is detected in a state where the tool is attached to the main shaft, and a laser is irradiated on the shank portion or the connecting tool of the tool according to the vibration to partially transform the structure. Since the expansion or contraction is performed, it is possible to eliminate or reduce a minute shake of several μm or less, which has been impossible in the past. As a result, it is possible to improve machining accuracy, reduce surface roughness, and extend the tool life.

Hereinafter, preferred embodiments of the present invention will be described based on examples.

FIG. 1 shows an example of a machine tool such as an end mill for carrying out the method of the present invention. The machine tool is provided with a spindle head 1 that can move in the X, Y, and Z directions, and a spindle 2 that is rotationally driven by a motor (not shown). A cutting tool 4 is attached to the main shaft 2 via a collet holder 3. As shown in FIG. 2, the collet holder 3 is a known one. As shown in FIG. 2, the split collet 3c is inserted into the tapered hole 3b formed at the tip of the holder shank 3a, and the fastening tool 3d is screwed into the tip of the holder shank 3a. By doing so, the split collet 3c is tightened.

A sleeve 5 is inserted into the split collet 3c and is fastened and fixed by a fastening tool 3d. The sleeve 5 is fixed to the shank portion 4a of the tool 4 without backlash by shrink fitting or the like. As will be described later, the sleeve 5 is made of a material that transforms by heating by laser irradiation and then cooling, and causes expansion or contraction, for example, a steel material such as S45C or SUJ2.

A workpiece W fixed on the table 6 is disposed directly below the tool 4. The spindle 2 is lowered from the standby position shown in FIG. 1, and the tool 4 is brought into contact with the workpiece W as desired. Process. A shake detection device 10 is disposed on the side of the tool 4 and detects the shake of the tool 4 while the tool 4 is still attached to the spindle 2. As the shake detection device 10, for example, a method in which a lever-type electric micrometer is brought into contact with the shank portion 4 a of the tool 4 and the main shaft 2 is rotated at a low speed to read the amplitude of the micrometer indicated value, or a laser measuring device is used. It may be used to measure the runout of the cutting edge of the tool 4. In the latter case, the runout of the cutting edge can be measured during high-speed rotation, so that it can be measured in a state closer to the machining state. FIG. 1 shows an example of a laser measuring device. The detection signal of the shake detection device 10 is sent to the control device 11. The control device 11 calculates a shake amount and a shake direction based on the detection signal of the shake detection device 10 and the rotational position signal of the main shaft 2 from the head 1 and controls the irradiation device 20 described later.

FIG. 3 shows a case where there is a runout a between the spindle 2 and the tool 4. When the rotation center of the main shaft 2 is O1, and the center of the tool 4 is O2, the distance between the centers O1 and O2 is a deflection a. When the spindle 2 is rotated once, the tool 4 rotates around O1, and the outermost locus C draws a circle as shown by a broken line. Assuming that the diameter of the tool 4 is d, the outer diameter of the circle C is d + 2a. Therefore, the deflection amount a can be obtained from the outer diameter of the circle C. By detecting the rotational position of the spindle 2 simultaneously with the shake amount a, the shake direction (phase) can also be measured. In the case of FIG. 3, the deflection direction θ = 0 at the initial position, that is, the center O2 of the tool 4 is directly above the rotation center O1 of the main shaft 2.

An irradiation device 20 that irradiates the sleeve 5 with a laser beam from an orthogonal direction and locally heats the sleeve 5 is disposed on the side of the main shaft 2. After detecting the deflection amount a and the deflection direction of the tool 4 by the deflection detection device 10 as described above, the side surface on the deflection direction side of the sleeve 5 is irradiated with a laser beam while the main shaft 2 is stopped. The position, range, intensity, and time for applying the laser are adjusted according to the shake amount a. The laser may irradiate the shank portion 4a of the tool 4, but if the tool 4 is made of cemented carbide, it cannot be transformed, so that the sleeve 5 made of a transformable material as described above is applied to the sleeve 5. It is better to irradiate.

When the laser beam is irradiated on the side surface on the vibration direction side of the sleeve 5 made of steel, the sleeve 5 is locally heated to reach the austenite region, and immediately after heating, it is rapidly self-cooled by the thermal diffusion of the material itself. Causes hardening by martensitic transformation. When the martensitic transformation is performed, the structure expands, so that the cutting edge 4b of the tool 4 is displaced to the side opposite to the laser irradiation portion, and the vibration is reduced. As described above, the sleeve 5 locally undergoes martensite transformation, but since there is almost no change in its mechanical strength, there is no concern that the machining accuracy will be lowered or the wear will be increased during cutting.

The present inventors conducted a shake correction experiment using a material M as shown in FIG. The result is shown in FIG. The material M used here is a round bar made of steel (SUJ2) having a diameter of 6 mm and a length of 100 mm, attached with the root portion fixed to 20 mm, irradiated with a YAG laser at a position 40 mm from the tip, The amount of deflection b in the part was measured.
The laser irradiation conditions are as follows.
Laser output: 15W
Irradiation diameter: φ0.96mm, φ2.88mm

As shown in FIG. 5, when the laser irradiation time is changed from 3 seconds to 12 seconds, when the irradiation size is 0.96 mm, the shake amount can be varied in the range of 3 μm to 6 μm, and the irradiation size is 2.88 mm. In this case, the shake amount could be varied in the range of 1 μm to 7 μm. As a result, it was confirmed that the amount of deflection can be arbitrarily adjusted by the laser irradiation time. Further, it was found that the amount of shake greatly changes when the laser irradiation time is increased or decreased rather than the laser irradiation diameter. In addition to the above, the shake amount can be adjusted by adjusting the irradiation position and the laser output.

In the above examples, the martensite transformation was performed by heating to an austenite structure by laser irradiation and then rapidly cooling, but the pearlite was gradually cooled by heating to an austenite structure by laser irradiation. It may be transformed. In this case, since the contraction is caused by the tissue transformation, the laser may be irradiated on the side opposite to the shake direction side.

In the above embodiment, an example in which the tool 4 is attached to the collet holder 3 via the sleeve 5 has been described. However, the tool 4 may be directly attached to the collet holder 3. In this case, it is necessary to irradiate the shank part 4a of the tool 4 with a laser to transform the structure of the shank part 4a. The type of laser is not limited to the YAG laser, and other lasers such as a CO ₂ laser can also be used.

It is a schematic side view of an example of the machine tool for implementing this invention method. It is a partial cross section side view of the collet holder holding a cutting tool. It is a figure which shows run-out of a cutting tool. It is a figure which shows the shake suppression method by laser irradiation. It is a figure which shows the relationship between laser irradiation time and a shake amount.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Machine tool 2 Spindle 3 Collet holder 4 Cutting tool 4a Shank part 5 Sleeve

Claims (3)

In a machine tool that attaches a tool to the spindle and rotates the spindle to cut the workpiece with the tool,
Use a material that transforms by heating by laser irradiation and subsequent cooling to cause expansion or contraction in the shank part of the tool or the connecting tool that connects the tool and the main shaft,
Detects runout with respect to the shaft center with the tool attached to the spindle.
According to the vibration, the material part is irradiated with a laser, the material part is transformed by heating and subsequent cooling, and the vibration is reduced by causing expansion or contraction to reduce the vibration. . 2. The method for suppressing runout of a cutting tool according to claim 1, wherein the material part is formed of a steel material, and is heated so as to have an austenite structure by the laser irradiation and is rapidly cooled to cause martensitic transformation. 2. The method for suppressing vibration of a cutting tool according to claim 1, wherein the material portion is formed of a steel material, and is heated to have an austenite structure by the laser irradiation and is gradually cooled to cause pearlite transformation.

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