JPS6144626B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention includes a contact detection device that detects when a tool attached to a spindle of a machine tool comes into contact with a workpiece, and a contact detection signal from the contact detection device detects the contact of the tool. The present invention relates to a feed control device that controls feed.

In recent years, machine tools equipped with a contact detection device that detects when a tool attached to the spindle has come into contact with a workpiece have been developed. The feed rate of the tool can be reduced from the rapid feed rate to the cutting feed rate, or the tool can be moved until it comes into contact with the workpiece reference surface, and the tool feed can be controlled based on this contact position.

However, when performing the above operations in such machine tools, the contact detection device reduces the tool feed speed or stops the tool feed based on the signal from the contact detection device, which may cause the contact detection device to malfunction. If the tool stops working, the feed speed of the tool will not be reduced or the feed will not be stopped even when the tool comes into contact with the workpiece, which may not only damage the workpiece but also cause damage to the tool. It was hot.

In view of such conventional problems, the present invention verifies whether the contact detection device operates normally before controlling the tool feed using the contact detection signal,
If the contact detection device does not operate normally, it sends out an abnormality signal to prevent the start of tool feed control based on the contact detection signal.An embodiment thereof will be described below with reference to the drawings.

In FIG. 1, 10 is a saddle that is guided so as to be movable in the left-right direction (Z-axis direction) on the bed 11 and is moved by a servo motor 12, and 13 is a saddle that is placed on this saddle 10 in the X-axis direction perpendicular to the plane of the paper. This work table 13 is a work table that is movably guided and moved by a servo motor 14 (not shown).
A workpiece W is placed on top.

On the other hand, 15 is a spindle head that is guided movably in the vertical direction (Y-axis direction) on a column 16 provided at the rear of the bed 11 and is moved by a servo motor 17. , tool T at the tip
The main shaft 18 equipped with the main shaft 18 is mounted on a shaft via a bearing (not shown), and is connected to a main shaft driving motor 20 via a gear mechanism 19. Further, a brush body 21 is provided at the rear of the spindle head 15, the tip contact portion 21a of which comes into contact with the rear end surface of the spindle 18 by the pressing force of a built-in spring, thereby bypassing the oil film resistance of the bearing that supports the spindle 18. I'm starting to do that.

Furthermore, on the front surface of the spindle head 15, a coil 22 for contact detection is connected to the AC power supply PS via a resistor R _S for current detection and is wound in a toroidal shape so as to surround the spindle 18. An annular magnetic flux is generated around the main shaft 18. Therefore, when the tool T contacts the workpiece W, the workpiece W, the work table 13, the saddle 10, the bed 11, the column 16, the spindle head 15, the spindle 18, and the tool T form a part as shown by the broken line in the figure. An induced current flows through the current path 24, and the excitation current flowing through the coil 22 increases.

The contact detection circuit 23 detects contact between the tool T and the workpiece W by detecting an increase in the excitation current flowing through the coil 22 due to an increase in the potential difference generated between both ends of the resistor R _S . The contact detection signal TDS is output at the same time as the tool T contacts the workpiece W, but if a failure of the contact detection circuit 23, a disconnection of the detection coil 22, wear of the brush body 21, etc. occurs,
Even if the tool T contacts the workpiece W, a contact detection signal is not generated.
TDS will no longer be sent.

FIG. 2 shows a control circuit that controls the feed of the machine tool configured as described above, and the contact detection signal TDS output from the contact detection circuit 23 is connected to the drive circuit 31 that drives the servo motors 12, 14, and 17. ,M
A contact detection signal is given to a numerical control device 30 connected to a decoder 32 that decodes the code.
By sending TDS, the servo motors 12, 14,
It is used to stop the rotation of the tool T to stop the movement of the tool T, or to reduce the feed speed of the tool T by switching the moving speeds of the servo motors 12, 14, and 17. Further, the main shaft motor drive circuit 33 is
A circuit that controls rotation and stop of the main shaft motor 20,
MO that commands the rotation of the main shaft 18 from the decoder 32
When the command signal No. 3 is output, the spindle motor 20 starts rotating, and when the decoder 32 outputs MO5, which commands the stop of the spindle 18, the rotation of the spindle motor 20 is stopped. The drive circuit 33 is configured to send an auxiliary function completion signal MFIN to the numerical control device 30 after a certain period of time after the command signal is given. decoder 3 until it is given
A command signal is output from 2.

Circuit 34 surrounded by two-dot chain line in Fig. 2
is an abnormality detection circuit that detects when contact detection is no longer performed normally and stops numerical control operation.
Timer TIM, flip-flop FF1, FF2, AND gate AG1, AG2, inverter INV1,
It mainly consists of INV2 and one-shot circuit OSC.

This abnormality detection circuit 34 focuses on the fact that rotation of the spindle motor 20 is always commanded a predetermined time before the tool T contacts the workpiece W in machining each machining location, and the rotation of the spindle motor 20 is commanded. If the contact detection signal TDS is not sent out from the contact detection circuit 23 during a set time longer than the predetermined time, it is detected that the contact detection is no longer performed normally. , a set time longer than the predetermined time is set as the time-up time of the timer TIM.

When this timer TIM receives the MO3 command signal that commands the rotation of the spindle motor 20 from the decoder 32, it resets the count value to zero and then starts counting pulses from the built-in clock generator.
When the set time elapses, a time-up signal TUS is output. The time-up signal TUS from this timer TIM is supplied to the AND gate AG1 via the inverter INV1, and also to the AND gate AG2.
It is now being supplied directly to The contact detection signal TDS output from the contact detection circuit 23 is applied to the other input of the AND gate AG1, and the output signal from the AND gate AG1 is applied to the set terminal S of the flip-flop FF1. The reset terminal of FF1 is configured to receive a signal from a one-shot circuit OSC which outputs a pulse with a fixed time width when the MO3 command is output from the decoder 32. Therefore, if the contact detection signal TDS is output from the contact detection circuit 23 after the rotation of the spindle 18 is commanded until the timer TIM times up, the flip-flop FF1 is set.
If the contact detection signal TDS is not sent out even once during this period, the reset state remains.

The signal from the reset output terminal of flip-flop FF1 is applied to the set terminal S of flip-flop FF2 via AND gate AG2, and if flip-flop FF1 is not set when timer TIM times up, flip-flop FF2 is set. be done. The signal output from the reset output terminal of this flip-flop FF2 is applied to an AND gate AG3 provided in the middle of a signal line 36 that sends an auxiliary function completion signal MFIN from the spindle motor drive circuit 33 to the numerical control device 30. When flip-flop FF2 is set, an auxiliary function completion signal MFIN is sent to the numerical control device 30.
will no longer be sent. As a result, the numerical control device 30 completes the machining of the currently machining location, and stops its operation at the time when the main spindle 18 is commanded to stop.

Therefore, if the contact detection operation is no longer performed normally, the numerical control operation is stopped at the time when machining of the machining location that was started after the contact detection operation was no longer performed normally is completed. Contact detection signal
It is rare that machining is performed continuously by controlling the feed of the tool T using TDS, and in normal cases, before machining is performed using machining feed using the contact detection signal TDS, normal machining must be performed. will be held. Therefore, by checking the operation of the contact detection device as described above, it is possible to prevent processing feed from being started using the contact detection signal TDS in a state where contact detection cannot be performed normally.

Note that a lamp PL1 is connected between the reset output terminal of flip-flop FF2 and the power supply +Vcc, which is lit by the setting of flip-flop FF2.
is connected through a resistor R1, and the occurrence of an abnormality is notified to the operator.

FIG. 3 shows a modification of the abnormality detection circuit 34, in which the timer 36 is set by sending a command signal from MO3.
A flip-flop FF3 is provided which is reset by sending the command signal No.5.
AND gate AG1 is opened by a signal from set output terminal Q of FF3, and AND gate AG2 is opened by sending a command signal from MO5. Therefore, in this circuit, if the contact detection signal TDS is never sent out while the spindle motor 20 is rotating, it is determined that there is an abnormality and the numerical control operation is stopped. Note that it is detected that the main shaft motor 20 is rotating by sending out a speed signal from a rotation detector for speed feedback attached to the main shaft motor 20, and thereby the AND gate AG1 is detected. ,AG
The opening and closing of 2 may be controlled.

Figure 4 shows an abnormality detection circuit that allows operation confirmation by instructing confirmation of contact detection operation using numerical control data.As shown in Figure 5, before and after the machining program, MA commands the start of operation check and commands the end of operation check
By programming the MB's auxiliary function code, it is possible to check the operation of the contact detection device. That is, in this embodiment as well, as in the second embodiment, a flip-flop FF3 is provided in place of the timer TIM, and this flip-flop FF3 receives an MA signal from the decoder 32 that instructs the start of operation confirmation. It is set and reset when the decoder 32 outputs an MB signal instructing completion of operation confirmation. Therefore, in this circuit, if the contact detection signal TDS is not sent even once while the operation check is being commanded, the numerical control operation will be stopped, and the contact detection signal TDS will be stopped.
By programming the MA and MB codes before and after the machining program before machining the workpiece W using TDS tool feeding, contact detection can be performed even if the contact detection operation is not performed normally. It is possible to prevent tool feeding from being started by the signal TDS. In addition, when using this circuit, a signal generation circuit 37 is provided which outputs an auxiliary function completion signal MFIN after a certain period of time after the command signals MA and MB are sent, and the completion signal outputted from this is sent to the spindle motor drive circuit 33. It is necessary to apply it to the AND gate AG3 together with the completion signal output from the .

As described above, in the feed control device of the present invention, before the tool feed control is performed using the contact detection signal from the contact detection device, the tool contacts the workpiece once during a predetermined period when the tool is contacted by the indirect detection device. It detects whether a detection signal is output or not, and if a contact detection signal is never sent, it is determined that contact detection is no longer being performed normally and an abnormal signal is sent. It is possible to prevent tool feed control from being started using contact detection signals when detection cannot be performed normally.
Damage to workpieces and tools can be prevented.

[Brief explanation of the drawing]

The drawings show embodiments of the present invention; FIG. 1 is a diagram showing a schematic configuration of a machine tool, FIG. 2 is a diagram showing a first embodiment of an electric circuit for controlling the machine tool shown in FIG. Figure 3 shows the abnormality detection circuit 3 in Figure 2.
4 is a diagram showing a second embodiment of the present invention, FIG. 4 is a diagram showing a third embodiment thereof, and FIG. 5 is a diagram showing a numerical control program for checking the operation of the circuit shown in FIG. 4. 11... bed, 13... work table, 15...
Spindle head, 16... Column, 18... Spindle, 20... Spindle motor, 21... Brush body, 22... Contact detection coil, 23... Contact detection circuit, 30... Numerical control device,
31... Servo motor drive circuit, 32... Decoder,
33...Spindle motor drive circuit, 34...Abnormality detection circuit, AG1-AG3...AND gate, FF1-FF3
…Flip-flop, INV1, INV2…Inverter, PL1…Lamp, T…Tool, TIM…Timer,
W...workpiece.

Claims (1)

[Claims] 1 Equipped with a contact detection device that detects when a tool attached to the main shaft of a machine tool comes into contact with a workpiece placed opposite to it, and detects the relative position of the tool by a contact detection signal from this contact detection device. In a feed control device configured to control the stopping of movement, etc., a signal detection means detects whether a contact detection signal is sent from the contact detection device during a predetermined period during which a tool should come into contact with a workpiece at least once. a storage element that is set to a specific state when the signal detection means detects that a contact detection signal is sent from the contact detection device; 1. A feed control device equipped with a contact detection device, characterized in that it is provided with abnormality determination means for sending out an abnormality signal when the contact detection device is not set in the above state.