JPH0248389B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a spindle unbalance vibration monitoring device that monitors the unbalanced vibration of a spindle equipped with a tool so that cutting can always be performed in a normal state, especially for various tools such as machining centers. The present invention relates to the above-mentioned vibration monitoring device suitable for a machine tool that cuts a workpiece.

The purpose of the present invention is to capture the unbalanced vibration of the spindle as a speed value, and to make it possible to determine the abnormal state of the unbalanced vibration of the spindle by comparing it with a constant speed tolerance regardless of the spindle rotation speed. That's true.

Generally, in a machine tool such as a machining center, the spindle rotation speed is varied from several tens of revolutions per minute to nearly 10,000 revolutions per minute depending on various tools attached to the main spindle. In such a machine tool, when various tools are attached and the spindle is rotated, the spindle vibrates unbalanced, and if this vibration becomes large, it becomes impossible to ensure the required machining accuracy. For this purpose, the unbalanced vibration of the main shaft is detected as a vibration displacement, and this is compared with a certain displacement tolerance value to detect an abnormal state of the unbalanced vibration of the main shaft.

However, when considered from the sensory and psychological aspects of humans, the above-mentioned devices based on a certain vibration displacement tolerance value have a large sensory and psychological impact on humans, especially during high-speed rotation. Even if there is no problem with machining accuracy, it may be perceived as an abnormal state due to the sense of vibration, which is not realistic. This is because the human sense of vibration is close to the vibration speed when the frequency is 8 Hz or higher (480 rpm or higher) and does not match the vibration displacement.

Therefore, the present invention eliminates unbalanced vibration of the main shaft.
In order to maintain satisfactory machining accuracy at any spindle rotation speed and to ensure that the vibration is not detected as an abnormal state, unbalanced vibration is captured as a speed value, and abnormality is determined by comparing it with a certain speed tolerance. This allows the status to be determined.

Embodiments of the present invention will be described below based on the drawings.
In FIG. 1, 10 indicates a spindle head of a numerically controlled machine tool equipped with an automatic tool changer, for example, and a spindle 11 supported by this spindle head 10 is loaded with various tools 12 according to a predetermined machining program. They are installed in sequence and driven to rotate at a set rotation speed. An electrodynamic displacement detector 13 is attached to the spindle head 10, and this displacement detector 13 detects unbalanced vibrations due to rotation of the spindle 11 as a speed value, and inputs the detection signal to an amplifier 14. A comparator 15 is connected to the amplifier 14, and the comparator 15 compares the speed value A output from the displacement detector 13 with the speed tolerance value B set by the setting device 16, and the speed value A is determined as the speed. If it is smaller than the tolerance value B, an OK signal is sent, and if it is larger than the tolerance value B, an OK signal is sent.
An NG signal is output from the discriminator 17.

FIG. 2 shows how the vibration speed V with respect to the vibration frequency f (f=N/60) is determined by the unbalanced vibration of the main shaft 11 when various tools 12 are attached to the main shaft 11 and rotated at various rotational speeds N. This is experimental data investigated from the perspective of the vibration sensation experienced by humans, and the × in the figure
The marks indicate areas where vibrations were felt to be large, and the circles indicate areas where vibrations were felt to be small. From this figure, it can be seen that regardless of the vibration frequency f (spindle rotational speed N), the vibration sensation given to humans is large above a certain speed value V1, and becomes small when the speed value is below V1. Furthermore, it has been found that when cutting is performed under spindle unbalanced vibration at a speed value of V1 or less, machining accuracy can be well guaranteed.

Therefore, by setting the speed value V1 as the speed tolerance value B in the setting device 16, the speed value A detected by the displacement detector 13 and the speed tolerance set in the setting device 16 can be adjusted at any spindle rotation speed. By comparing with the value BV1, an abnormal state of unbalanced vibration of the spindle 11 can be determined, and if an NG signal is sent, cutting is not performed to prevent a decrease in machining accuracy.

As described above, the present invention detects the unbalanced vibration of the spindle as a speed value, and detects the abnormal state of the unbalanced vibration of the spindle by comparing it with a speed tolerance value that is set constant regardless of the rotation speed of the spindle. Since the configuration is designed to discriminate, it is possible to determine unbalanced vibrations that are satisfactory in terms of machining accuracy by comparing them with a constant speed tolerance at any spindle rotation speed, and that are not recognized as abnormal conditions based on the sense of vibration. This has the effect of making it possible to accurately and easily determine unbalanced vibrations of a main shaft that is rotated at various rotational speeds with various tools attached to it, such as in a machining center.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is a block diagram schematically showing a spindle unbalance vibration monitoring device, and FIG. 2 is experimental data showing the relationship between vibration frequency and vibration speed. 10...Spindle head, 11...Spindle, 12...Tool, 13...Detector, 14...Amplifier, 15...
Comparator, 16...Setter, 17...Discriminator.

Claims (1)

[Claims] 1. A detector for monitoring unbalanced vibrations of a spindle rotated at various rotational speeds with various tools attached thereto, and detecting unbalanced vibrations of the spindle generated by the rotation of the spindle as a speed value; , a setting device that sets a constant speed tolerance regardless of the rotation speed of the main shaft; and a speed value detected by the detector and the speed tolerance set by the setting device are compared. A spindle unbalance vibration monitoring device, comprising: a comparison and discrimination device for determining an abnormal state of unbalance vibration.