JP2505811B2 - Tool damage detection device for spindle head - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a spindle head for machining,
The present invention relates to a tool damage detection device that detects tool damage from changes in load torque.

Conventional technology and its problems In order to realize unmanned machining, it is essential to have a system that monitors the tool status on behalf of the operator. Therefore, load current monitoring method, strain gauge method, AE Many types such as (Acoustic Emission) sensor type have been proposed.

The load current monitoring method that has been used for a long time detects wear and breakage of tools by detecting the overload current of the spindle drive motor, but it is not easily affected by the voltage fluctuation of the power supply. In a multi-spindle head in which one motor drives a plurality of spindles at the same time, it is impossible to specify which spindle has a damaged tool.

In the strain gauge method, a strain gauge is attached to a spindle or a housing, and damage of the tool is detected by monitoring the vertical force or axial torque of the spindle due to cutting. However, regardless of whether the strain gauge is attached to the housing or the spindle, the diameter of the housing around the strain gauge increases due to the attachment space, and the spindle becomes longer than necessary. Particularly in the case of a multi-axis spindle head, the pitch between adjacent spindles is restricted by the increase in the diameter of the housing. In addition, when the strain gauge is attached to the spindle side, a slip ring is indispensable for taking out the gauge output, and maintenance is troublesome in addition to the above-mentioned increase in diameter around the gauge.

Furthermore, when attaching the strain gauge to the spindle, it is usual to use adhesive, so if the strain gauge is used in situations with large torque fluctuations, the strain gauge may peel off.
In addition to the possibility of falling off, the durability will drastically decrease when immersed in a lubricant.

On the other hand, the AE sensor method detects the breakage of the tool by capturing the elastic wave (ultrasonic wave) generated when the tool breaks. It is easily affected, and improvement in detection accuracy cannot be expected.

In order to solve the above-mentioned various problems, the present invention is designed to detect tool damage as torque fluctuation by a magnetostrictive torque sensor.

Means for Solving the Problems The present invention is a magnetostrictive type in which a spindle is a magnetostrictive shaft in the vicinity of a tip of a spindle on which a predetermined cutting tool is mounted, and damage of the cutting tool is detected as torque fluctuation. Torque sensor is provided. This torque sensor is provided directly on the outer peripheral surface of the spindle and is disposed on the outer periphery of the spindle and a plurality of grooves forming a predetermined angle with the axial direction of the spindle. And a plurality of coils forming a magnetic circuit.

As shown in the embodiment, the grooves are formed in such a manner that they are inclined in opposite directions with respect to the circumferential direction of the spindle by a predetermined angle.

Looking at the relationship between damage and torque of the working cutting tool, when the cutting edge of the tool becomes worn or a part of it is cut, the cutting resistance increases rapidly, and the torque of the spindle increases accordingly. Further, when the tool is cut off from the root and falls off, the cutting resistance sharply decreases, and the torque accordingly decreases.

Therefore, for example, a bridge circuit including the above coil is configured to obtain a torque output according to the torsional torque of the spindle.

As the output processing, according to the level of the torque output, for example, it is determined whether the tool is worn or broken,
A tool replacement command is output in the case of wear, and a machining stop command is output in the case of tool breakage.

Embodiments FIGS. 1A and 1B are schematic explanatory views showing an embodiment of the present invention, illustrating a multi-axis spindle head.

In the housing 2 of the multi-spindle head 1, a large number of spindles 3 are supported via bearings 4, and each spindle 3 has an intermediate shaft 7 via transmission gear trains 5 and 6.
It is connected to the. The intermediate shaft 7 is connected to an output shaft 10 of a drive motor 9 by a coupling 8. Therefore,
When the drive motor 9 is started, the spindles 3 are driven to rotate at the same time. 11 is a housing cover.

A cutting tool 12, such as a drill or a boring cutter, is attached to the tip of each spindle 3, and a magnetostrictive torque sensor 14 having the spindle 3 itself as a magnetostrictive axis is mounted near the tip of each spindle 3.
It is arranged through 13.

As shown in FIG. 2 in addition to FIGS. 1 (A) and (B), the torque sensor 14 has an angle of 45 degrees with the axial direction on the outer peripheral surface of the tip portion of the spindle 3 having a magnetostrictive effect. The spindle 3 itself is used as a magnetostrictive axis by forming the plurality of formed grooves 15a, 15b symmetrically with respect to the circumferential direction of the spindle 3 as the center of symmetry. Then, on the outer periphery of the spindle 3, two exciting coils 1 are arranged along the axial direction.
6 and 17 are arranged side by side, and a yoke 18 made of a high magnetic permeability material such as permalloy is disposed on the outer peripheral portion of the exciting coils 16 and 17 with a gap G between the exciting coils 16 and 17 and the spindle 3. It covers the coils 16 and 17. Therefore, the third
As shown in the figure, by applying an alternating voltage to the two exciting coils 16 and 17, magnetic circuits passing through the spindle 3, the gap G and the yoke 18 are formed around the exciting coils 16 and 17, respectively.

Then, as shown in FIG. 3, a bridge circuit including the exciting coils 16 and 17 as an inductance is configured, so that the output according to the screw torque of the spindle 3 is amplified.
(The construction of such a torque sensor is disclosed in Japanese Patent Application No. 61-28364).

Here, an example of the output processing of the above torque output will be described with reference to FIG. 5. In the present embodiment, the torque output of the torque sensor 14 individually attached to each spindle 3 is used as the determination circuit of the motor 9 control system. It takes in 23 and outputs an alarm as a tool change command or a machining stop command.

That is, regarding the relationship between the damage of the cutting tool 12 and the torque, when the cutting edge of the cutting tool 12 is worn or a part of the cutting edge is chipped (damage), the cutting resistance sharply increases. As a result, the torsional torque of the spindle 3 rapidly increases. When the rod-shaped cutting tool 12, such as a drill, is completely broken and dropped from the root, the cutting resistance sharply decreases, and accordingly, the torsion torque of the spindle 3 sharply decreases.

FIG. 4 shows a concrete example of the torque level. When the torque level when the tool is normal is a, when the cutting edge of the cutting tool 12 is worn and becomes less sharp, the torque level becomes higher as shown by b. Further, when a part of the cutting edge is cut (broken), the cutting resistance is increased as compared with the case of steady wear, and therefore the torque is also higher than b like c. In addition, as described above, when the cutting tool 12 is broken from the root and falls off, the torque is extremely low as indicated by d because there is no cutting resistance.

Therefore, in the determination circuit 23 of FIG.
While monitoring the output of 14, the threshold value corresponding to each tool abnormality is preset in the determination circuit 23, for example, when it is determined as "tool wear", a tool replacement command is output and the cutting tool 12 Encourage early replacement of. On the other hand, if it is determined that the tool is missing, it is difficult to continue machining, so a machining stop command is output. Also tools
If 12 is determined to be a “tool breakage” that is completely broken from the root, it is difficult to perform the subsequent machining in the same manner as above, so a machining stop command is output.

The present invention can be applied not only to a multi-axis spindle head but also to a single-axis spindle head.

EFFECTS OF THE INVENTION As described above, according to the present invention, the damage of the cutting tool is detected as the fluctuation of the torque by the torque sensor having the spindle itself as the magnetostrictive axis.

(1) When applied to a multi-axis spindle head, unlike the conventional load current monitoring method, it is possible to accurately identify which spindle tool has been damaged.

(2) Since only the coil is arranged around the spindle, the torque sensor itself can be miniaturized, and even if it is applied to each axis of a multi-axis spindle head, the pitch between spindles is not restricted. .

(3) Since the slip ring like the strain gauge method is not required, the maintenance becomes easy.

(4) Since there is no adhesive part like the strain gauge method,
No decrease in durability or detection accuracy due to oil.

[Brief description of drawings]

1A is a sectional view of a spindle head showing an embodiment of the present invention, FIG. 1B is an enlarged sectional view of the torque sensor in FIG. 1A, and FIG. 2 is FIG. 1B. ) Cross-sectional view taken along line II-II, FIG. 3 is a detection circuit diagram of the torque sensor, FIG. 4 is an explanatory diagram showing the relationship between torque and tool damage, and FIG. 5 is a torque sensor output process. It is a circuit diagram which shows an example. 1 ... Multi-axis spindle head, 3 ... Spindle, 9 ...
… Drive motor, 12 …… Cutting tool, 14 …… Torque sensor,
15a, 15b …… groove, 16,17 …… excitation coil, 18 …… yoke.

Claims (1)

(57) [Claims] 1. A magnetostrictive torque sensor is provided in the vicinity of the tip of a spindle having a predetermined cutting tool mounted on the tip thereof, the spindle being a magnetostrictive axis, and the damage of the cutting tool being detected as torque fluctuation. , The torque sensor is provided directly on the outer peripheral surface of the spindle to form a plurality of grooves at a predetermined angle with the axial direction of the spindle, and is arranged on the outer periphery of the spindle so that the spindle serves as a part of a magnetic path. A tool damage detection device for a spindle head, comprising: a plurality of coils forming a magnetic circuit.