JPH0669659B2 - Cutting monitoring equipment - Google Patents

Description

Description: [Industrial application] The present invention relates to a cutting monitoring device for monitoring a machining abnormality by a current value of a spindle motor. More specifically, the present invention relates to a direct tapping cutting monitoring device that performs tap monitoring by holding a tap with a holder that does not float, that is, when tapping using a so-called tapperless tap, by using the current value of a spindle motor that rotationally drives the tap. .

[Prior Art] In order to perform thread cutting with a machining center, thread processing is performed with a tap holder fixed to a rotating spindle. The Z-axis feed rate is calculated and calculated from the spindle speed and the tap pitch. However, a certain rise time is required for the rotation speed of the spindle holding the taps to reach the commanded rotation speed. This is because the spindle / spindle motor has a time constant. During this rising time,
A so-called transient current flows, in which the current flowing through the spindle drive motor is temporarily high.

Therefore, when monitoring the load of tapping by the value of the current flowing in the spindle drive motor, the transient current at the time of starting the spindle motor is a characteristic of the motor itself, which is not related to cutting,
This time is excluded from load monitoring. In the load monitoring device currently used, first, the time for the current value to stabilize is set in advance for each rotation speed of the spindle motor. The load monitoring device reads the S function (spindle function) of the spindle rotation speed, the M function of the spindle forward rotation and the reverse rotation, and then determines the time until it stabilizes when the spindle motor is instructed to rotate normally, reversely, or stop. From the above, the load monitoring was cut during the set time until stabilization.

At this time, as the holder of the tap, a so-called floating holder is used in which the holder and the tap slide in the feed direction when a constant overload is applied.

[Problems to be Solved by the Invention] Recently, in place of the method described above, a direct tap in which a tap holder is not fixed and a tap is fixed to a spindle is used. High-speed, high-accuracy tapping methods that achieve complete synchronization have become popular. However, when this spindle synchronous feed command is issued, the normal rotation command and the reverse rotation command of the spindle motor and the feed motor are generated and processed inside the control device, so that they are not output from the control device to the outside such as the cutting monitoring device.

That is, the S function of the spindle motor, the spindle forward rotation (MO3), the spindle reverse rotation (MO4), and the spindle stop (MO5) command are not output from the numerical controller. This is because the rotation of the Z-axis feed motor and the rotation of the spindle cannot be perfectly synchronized with these commands.
For this reason, it is not possible to cut the transient current when the spindle motor starts up because the command start time is not known, and load monitoring is not performed in direct tapping processing. The present invention focuses on these problems and achieves the following objects.

An object of the present invention is to provide a cutting monitoring device that monitors a machining load only when the Z-axis feed motor is in a steady feed state.

[Means for Solving the Problems] In order to solve the problems, the present invention employs the following means.

The first means are: a. A spindle for holding and fixing the tool, b. A spindle motor (16) for rotationally driving the spindle, and c. An axial direction of the spindle or a direction perpendicular to the axial direction of the tool or the tool. Feed motor (7) for feeding the workpiece
D. Steady-state signal generating means (4) that outputs a steady-state feed signal indicating that the feed speed is in a steady state except when the feed motor (7) is being driven and is in the start-up or deceleration state, and e. Machining monitoring means (13) for monitoring the cutting load of the tool after the preset unobservable time (t ₁ ) after the steady feed signal is generated and during the time during which the steady feed signal is generated, f. A cutting monitoring device comprising an unmonitorable time storage means (14) for previously storing the unmonitorable time (t ₁ ) and g.

It is still more effective if the first means comprises the unmonitorable time storage means for storing the unmonitorable time (t ₁ ) for each rotation speed of the spindle motor (16).

In the first means, it is still effective when the tool whose cutting load is monitored is a direct tap.

[Operation] The spindle that holds and fixes the tool is driven to rotate by the spindle motor,
And start the tool. This feed motor starts to start up, goes out of the acceleration state, and a steady signal indicating that the feed speed has reached a steady state is issued.After this steady feed signal is generated, the preset tool monitoring Monitor the processing load.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a functional block diagram showing an embodiment of the cutting monitoring apparatus of the present invention. The numerical control (NC) device 1 is a known control device and controls a servomotor according to a program to give a desired trajectory to a tool. The NC device 1 has various commands to a main program memory 2 that stores a machining program, a system control unit 3 that has a central processing unit (CPU) and generalizes the whole, a servo control unit 6, a high-voltage control panel (PC) 10, and the like. It includes a distribution controller 4 for inputting and outputting signals.

A setting display board 5 including a CRT screen for inputting / outputting data and displaying data and a keyboard is connected to the NC device 1. Normally, the NC device 1 and the setting display board 5 are integrally incorporated and arranged. Distribution control unit 4
Is to distribute a pulse train to each axis such as X, Y, and Z and output it to the servo control unit 6 of each axis. The servo controller 6 controls each axis motor 7 with an encoder 8 for axis drive to create a desired locus.

The high-power control panel 10 includes a spindle motor 16 and hydraulic equipment (not shown).
It controls power equipment such as. The sequence control unit 11 controls the entire sequence of the high voltage control panel 10. The operation sequence of the sequence control unit 11 functions according to the program stored in the sequence program memory 12. The program stored in the sequence program memory 12 is rewritable.

The cutting monitoring control unit 13 receives a steady signal sent from the distribution control unit 4 and a setting monitoring disabled time t ₁ described later to generate a cutting monitoring valid signal, and monitors the cutting load during this time. The operation of the cutting monitoring control unit 13 is controlled according to a program stored and held in the cutting monitoring program memory 14. The cutting monitoring program memory 14 stores the unmonitorable time t ₁ for each spindle rotational speed, which will be described later. The cutting monitor control unit 13 receives and inputs the load current of the spindle motor 16 and the load current value of the feed servomotor 7 from the spindle control unit 15 and the servo control unit 6.

The cutting monitoring control unit 13 receives these load current values and outputs them to the sequence control unit 11, and outputs a necessary operation command as described later. The spindle control unit 15 receives a command from the sequence control unit 11 of the distribution control unit 4 and drives the spindle motor 16. The rotation speed of the spindle motor 16 is fed back by the encoder 17 to the spindle control unit 15. Figure 2 (a) is Z
It is a diagram showing the feed speed of the shaft feed motor 7, where the horizontal axis represents time and the vertical axis represents speed. FIG. 2B shows the spindle motor 16
The load current is measured by a load meter, and the horizontal axis represents time and the vertical axis represents load current.

As can be seen in FIG. 2 (b), the current during the starting time of the spindle motor 16 rises sharply. After this rapid increase of the current, the spindle motor 16 starts to start, and the current drops rapidly and then becomes stable. This unmonitorable time t ₁ is a time zone during which load monitoring cannot be performed because it is in a transient state. FIG. 2C shows a steady feed signal output from the distribution control unit 4 when the feed speed of the Z-axis servomotor is out of the acceleration / deceleration state. Figure 2 (d) is an illustration of the cutting monitoring signal output time t ₃ when excluding the monitoring disabled time t ₁ from the feed constant signal output time t _2.

Operation FIG. 3 is a flow chart of load monitoring during the tapping cycle. This flow starts when the direct mode command is issued and the fixed cycle command (G84) for tapping is issued. The directives in this program are usually of the form:

M21 G84X_Y_Z_R_P_F_L_ M21 is a direct mode command and means tap processing by direct tap. X and Y indicate tap hole position coordinates on the X axis and the Y axis. Z indicates the coordinates of the hole bottom position in the Z-axis direction. R has an operation starting point for tapping processing. P indicates the dwell time at the time of returning to the bottom of the tap hole and the R point. F is indicated by the feed speed, and is a value obtained by multiplying the spindle rotation speed by the feed pitch. L indicates the number of repetitions for tap processing.

FIG. 4 is a diagram showing the positions of the R and Z points during the tap cycle. When the tapping cycle is started by the above command, the Z-axis servomotor 7 drives
The tip of the tap reaches point R. The spindle motor 16 and the Z-axis servomotor 7 are started, and the spindle-synchronous feed in which the Z-axis servomotor 7 is synchronized with the rotation of the spindle motor 16 is started. It is determined whether the feed of the Z-axis servomotor 7 has reached a constant steady speed. Or the feed constant signal time t ₂ became the feed in R point or cutting starting point (not the position actually started cutting.) After starting, a steady speed condition where the Z-axis servo motor 7 is commanded from the acceleration state It is issued after judging whether or not (step
P ₁ ).

When the feed reaches the instructed feed speed, the distribution control unit 4 sends a steady feed signal (Fig. 2 (C)) to the cutting monitoring control unit 13.
Output to (P ₂ ). Since the load current value of the spindle motor 16 (Fig. 2 (b)) does not go into the transient state even when the feeding is in the steady state, it is preferable to set and store this unmonitorable time t ₁ in advance. Note that this unmonitorable time t ₁ is
An experimentally determined value is stored for each rotation speed of the spindle motor 16. When the unmonitorable time t ₁ has elapsed (P ₃ ), the cutting monitoring signal t ₃ is output (P ₄ ).

After this monitoring disabled time (P _3), the cutting monitoring controller 13 starts the load monitoring (P _4). When the feed is decelerated, the distribution control unit 4 turns off the feed steady signal t ₂ . The cutting monitoring signal t of the cutting monitoring control unit 13 is received in response to the OFF signal of the steady feed signal.
_{3 is} also turned off.

[Other Embodiments] In the above embodiments, the cutting of the spindle motor is monitored, but the load of the feed motor may be similarly monitored. FIG. 5 (a),
(B) is an example showing a trajectory of the actual absolute value of the load current of the spindle motor and the speed of the feed motor. Although the example of tapping is described in the above embodiment, it is not necessary to limit to tapping, and the technical idea of the present invention can be applied to machining such as groove machining and cam surface machining.

[Effects of the Invention] As described in detail above, the present invention can directly grasp a tool without using a plurality of floating chuck mechanisms and can monitor the processing load. As a result, there is an effect of improving the processing speed.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing an embodiment of a cutting monitor for direct tapping, and FIGS. 2 (a) and 2 (b),
(C) and (d) are time charts showing waveforms during direct tapping, FIG. 3 is a flow chart showing the operation of the cutting monitoring device for direct tapping, and FIG. 4 is a diagram showing the trajectory of the tap cycle, and FIG. (A), (b) is a figure which shows the locus | trajectory of the actual load current of a spindle motor, and the speed of a feed motor. 1 ... NC device, 3 ... system control unit, 4 ... distribution control unit, 10 ... strong electric control panel, 13 ... cutting monitoring control unit, 14 ...
Cutting monitoring program memory, 15 ... Spindle control unit

Claims (3)

[Claims] 1. A spindle for holding and fixing a tool, b. A spindle motor (16) for rotationally driving this spindle, and c. An axial direction of the spindle or a direction perpendicular to the axial direction of the tool or the tool. Feed motor (7) for feeding the workpiece
D. Steady-state signal generating means (4) that outputs a steady-state feed signal indicating that the feed speed is in a steady state except when the feed motor (7) is being driven and is in the start-up or deceleration state, and e. Machining monitoring means (13) for monitoring the cutting load of the tool after the preset unobservable time (t ₁ ) after the feed steady signal is generated and during the time when the feed steady signal is generated, f. A cutting monitoring device comprising an unmonitorable time storage means (14) for previously storing the unmonitorable time (t ₁ ) and g. 2. The cutting monitoring device according to claim 1, further comprising: the unmonitorable time storage means for storing the unmonitorable time (t ₁ ) for each rotation speed of the spindle motor (16). 3. The cutting monitoring device according to claim 1, wherein the tool whose cutting load is monitored is a direct tap.