JPH01115548A - Detector for detecting defective position detector of numerical control machine tool - Google Patents

Abstract

PURPOSE:To prevent defective working by informing defective return of a limit switch when the deviation of the present position of a table from the regular operation position of limit switch gets out of a specified value in the return of table to an origin. CONSTITUTION:When a table 20 is returned to the origin by a motor 3 and drive shaft 27 according to a command from a NC unit 2, the deviation of the preset position of table 20 returned to the origin through a memory circuit 47 by a pulse generator 33 from the regular operation position of limit switches LS1, LS2 for detecting the vicinity of origin and the origin deceleration position memorized in memory circuits 48, 49 is calculated by a calculation circuit 51. When the calculated value is deviated from a specified value, the limit switches LS1, LS2 judges the return to be defective and generates the defective return signal to an external control board 5. Thus, workpiece can be prevented from defective working.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a position detector for a numerically controlled machine tool that detects malfunction of a position detector for detecting the position of each movable part in a numerically controlled machine tool. The present invention relates to a defect detection device.

[Prior Art] In general, in numerically controlled machine tools (NG machine tools), each movable part such as a saddle, table, indexing plate, etc. is moved around each axis so that the workpiece is positioned in a predetermined position and direction on the bed. direction,
Alternatively, move it around the axis, and then move the column in this state.
The main spindle is moved in each axial direction or around the axis to give the tool a predetermined depth of cut, thereby performing pre-programmed machining. Each movable part of such a numerically controlled machine tool has an origin, which is a reference position for machining, and is moved in parallel from this origin by a predetermined amount in the direction of each axis, and also rotates around the axis. It is composed of

By the way, when processing a workpiece using the numerically controlled machine tool, the power is of course turned off when the work is completed, and when the power is turned off, each of the movable parts stops at the position. On the other hand, as described above, each movable part is translated in parallel by a preprogrammed movement amount based on the origin.
Since it is rotated, it is first necessary to return each movable part to its origin before starting work.

In this return-to-origin operation, the axis is fed at high speed to a deceleration command position set in advance in the return direction, decelerated to a low speed at the command position, and further axis-feeded to the origin.

When performing such a return-to-origin operation, conventionally, all movable parts are moved from their stop positions in the direction of each axis and around the axis by a predetermined amount, that is, the distance or angle from each origin to the deceleration command position at the time of return to origin. Move in the opposite direction to return to origin,
After that, the above-mentioned return-to-origin operation is performed. However, with conventional devices that regularly apply axis feed in the opposite direction to return to origin, even if a certain movable part has stopped on the opposite side of the origin from the deceleration command position, This results in a further movement away from the origin by the predetermined amount described above, which causes a problem in that it takes a corresponding amount of time to return to the origin, resulting in a reduction in machining efficiency.

In order to solve the problems with conventional equipment as described above,
A storage means for determining and storing whether or not each movable part of the numerically controlled machine tool is located closer to the origin than the deceleration command position for returning to the origin set on each of the movement axes, and a signal from the storage means. When it is confirmed that each movable part is located closer to the origin than the deceleration command position, the axis is fed in the direction opposite to the return to the origin until the movable part exceeds the deceleration command position, and when the signal from the storage means changes. The apparatus is provided with a home return means that performs a home return operation and immediately performs a home return operation when it is confirmed that each movable part is located on the opposite side of the home from the deceleration command position. The amount of axis feed in the opposite direction to return should be the minimum amount necessary to reach the deceleration command position when the movable part is located on the home side, and zero when it is located on the opposite side to the home position. , a method has been proposed in which the time required for returning to the origin is shortened by that amount and machining efficiency is improved (see, for example, Japanese Patent Laid-Open No. 61-202202).

By the way, in the above-mentioned conventional numerically controlled machine tool, whether each movable part is located on the origin side or on the opposite side from the deceleration command position is detected by the origin return cam switch consisting of a limit switch. The return-to-origin cam switch may malfunction due to adhesion of workpiece chips, coolant, etc. that occur during the use of controlled machine tools.

As described above, when a malfunction occurs in the origin return cam switch, there is a problem in that the origin alignment of each movable part cannot be performed accurately, and the workpiece cannot be processed correctly.

[Object of the Invention] An object of the present invention is to detect malfunction of a limit switch that is placed at a predetermined position on the movement trajectory of the table of a numerically controlled machine tool and detect the movement position of the table, and to issue an alarm and It is an object of the present invention to provide a defect detection device for a position detector of a numerically controlled machine tool, which prevents the occurrence of defects in machining of objects.

"Structure of the Invention" For this reason, the present invention provides the following features: When a table that can be moved forward and backward by the operation of a drive shaft having an incremental pulse generator returns to its origin, the current position of the table from its origin is outputted from a current position detection means; The deviation from the normal operating position of a limit switch that is placed at a predetermined position on the movement locus of the table stored in the limit switch operating position storage means and detects the moving position of the table is calculated by the reset failure detection means, and the deviation is calculated. The present invention is characterized in that a return failure of the limit switch is detected based on the value.

When the table returns to its origin, the return failure detection means calculates the deviation between the current position of the table and the normal operating position of the limit switch. If the value deviates from the specified value, it is determined that the limit switch has failed to return, and a signal indicating the failure to return is output. This makes it easy to monitor whether or not the table of the numerically controlled machine tool has been accurately returned to its origin.

[Effects of the Invention] According to the present invention, when the table returns to its home position, if the deviation between the current position of the table and the normal operating position of the limit switch deviates from a specified value, it is determined that the limit switch has returned poorly; Since a signal indicating a return failure is output, the operator can use this signal to know that the limit switch has returned to a faulty state, thereby preventing the occurrence of machining defects on the workpiece.

[Example] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a block diagram of the overall configuration of a numerically controlled machine tool equipped with a defect detection device for a position detector of a numerically controlled machine tool according to the present invention.

The above-mentioned numerically controlled machine tool includes a machine tool main body l, a numerical control device 2. A speed servo amplifier section 4 for controlling the speed of the motor 3 for machining provided in the machine tool main body 1. and an external control panel 5.

In FIG. 1, only the main parts of the machine tool main body l related to the present invention are schematically shown, but a more specific configuration thereof is shown in FIG.

In FIG. 2, rails 12 extending in the Z-axis direction perpendicular to the plane of the paper are located on the left and right sides of the top surface of the bed 11 of the machine tool body l.
is fixed. A saddle 13 is provided above the bed 11, and guide members are provided on the left and right sides of the bottom surface of the saddle 13. A guide 7114a recessed in the guide member 14 is fitted into the rail 12 so as to be slidable in the Z-axis direction. Also, a nut member 1 is attached to the center of the lower surface of the saddle 13.
5 is screwed with a screw member 16, and although not shown, one end of the screw member 16 is connected to a drive motor attached to the bed 11, thereby causing the saddle 13 to move on the bed 11. is movable in the Z-axis direction.

A rail 18 extending in the left and right X-axis directions in FIG. 2 is fixed to the upper surface of the saddle 13 with bolts.

Further, a table 20 which is a movable part is arranged above the saddle 13, and guide members 21a are fixed to the left and right parts of the lower surface of the table 20.

21b is slidably fitted to the rail 18 in the X-axis direction.

An indexing board 24 is disposed above the table 20, which can rotate around the vertical Y axis in FIG. 2, and by supporting and rotating the workpiece, This is for determining the machining position.

In FIG. 1, only a mechanism for moving the table 20 in the X-axis direction and a configuration for controlling the same are shown. saddle 13
The movement and control of the table 20 in the Z-axis direction and the Y-axis direction of the indexing board 24 are performed in the same manner as for the table 20, so the control of the table 20 in the X-axis direction will be described below.

Referring again to FIG. 1, a drive shaft 27 made of a threaded member connected to the output shaft of the motor 3 and rotatably supported by bearing members 25 and 26 at both ends has a nut fixed to the lower part of the table 20. Members (not shown) are screwed together. The table 20 is rotated by the normal rotation of the motor 3.
It moves forward in the direction shown by arrow A1 toward the workpiece 28, and retreats in the direction shown by arrow A by reversing the motor 3.

As a result, the tool 29a held by the tool holding device 29 on the table 20 moves forward and backward relative to the work 28.

The movement range of the table 20 is restricted by stoppers 31 and 32. An incremental pulse generator 33 is also coupled to the motor 3.

On the other hand, the table 20 includes a cam portion 35 for actuating an actuator 34 of an origin detection limit switch LSI provided to detect that the table 20 is near the origin when returning to its origin; A cam portion 37 is formed to operate an actuator 36 of an origin deceleration position detection limit switch LS2 provided to detect that the table 20 has reached a position where it starts decelerating toward the origin.

The above-mentioned movement of the table 20 of the machine tool main body l and its movement speed are output from the command circuit 38 of the numerical control device 2. The command signal is converted into a pulse signal by the pulse conversion circuit 39, and then manually inputted to the deviation counter 41. This deviation counter 41 compares the pulse signal inputted from the pulse conversion circuit 39 with the feedback pulse representing the position of the table 20 fed back from the pulse generator 33 of the machine tool main body I, and detects the deviation signal. Ru. This deviation signal is D/
After being converted into an analog signal by the A converter 42, it is applied to the comparator 43 of the speed servo amplifier section 4.

The comparator 43 compares the deviation signal with a signal representing the moving speed of the table 20, which is manually input by the pulse generator 33 through the D/A converter 44. Then, a speed control signal generated by the speed controller 45 based on the output is given to the power amplification section 46. Thereby, the motor 3 moves the table 20 by a predetermined amount at a predetermined speed in response to the command signal from the command circuit 38.

On the other hand, in connection with the present invention, the numerical control device 2 includes a mechanical coordinate system storage circuit 47, an origin vicinity detection limit switch L.
Home point vicinity data storage circuit 48 that stores data of the ON position of SI, home point deceleration position detection limit switch LS
The present invention includes an origin deceleration data storage circuit 49 that stores data for the ON position of No. 2, and an arithmetic circuit 51.

The machine coordinate system storage circuit 47 constitutes a current position detecting means for detecting the current position of the table 20 from the origin when the table 20 of the machine tool body l returns to its origin. A pulse signal is input to the machine coordinate system storage circuit 47 from the pulse generator 33 of the machine tool body I in response to movement of the table 20. The memory of the mechanical coordinate system storage circuit 47 is backed up by a power failure protection circuit 47a.

On the other hand, the arithmetic circuit 51 operates on the table 2 of the machine tool main body 1.
0 and the normal operating position at which the origin detection limit switch LSI and origin deceleration position detection limit switch LS2 should operate due to the movement of the table 20,
and constitutes return failure detection means for detecting return failure of the origin deceleration position detection limit switch LS2. The arithmetic circuit 51 receives a signal indicating the current position of the table 20 from the machine coordinate system storage circuit 47, and receives a signal indicating the current position of the table 20 from the origin vicinity data storage circuit 48 and the origin deceleration data storage circuit 49 from which the table 20 of the machine tool main body l is moved. Therefore, the data signals of the normal operating positions at which the origin vicinity detection limit switch LSI and the origin deceleration position detection limit switch LS2 should be operated are input. The arithmetic circuit 51 also receives output signals from the origin detection limit switch LSI and the origin deceleration position detection limit switch LS2, while -JOG signals are input from the external control panel 5.
Command signals, that is, a command signal for moving the table 20 of the machine tool body 1 forward and a command signal for returning to the origin are input. When the deviation between the current position of the table 20 and the normal operating position of the origin vicinity detection limit switch LSI and the origin deceleration position detection limit switch LS2 deviates from a specified value, the arithmetic circuit 51 causes the external control panel 5 to detect the origin. Outputs a return failure signal of the vicinity detection limit switch LSI and a return failure signal of the origin deceleration position detection limit switch LS2.

The numerically controlled machine tool shown in FIG. 1 processes the workpiece 28 according to the machining parameters of the workpiece 28 inputted to the automatic coordinate system storage circuit 52 of the numerical control device 2 from the automatic coordinate system parameter setting circuit 52a. A pulse signal indicating the position of the table 20 is input to the automatic coordinate system storage circuit 52 from the pulse generator 33 of the machine tool main body l.

Its memory contents disappear when the power is turned off.

Next, the operation of the numerically controlled machine tool shown in FIG. 1 when returning to the origin will be described with reference to the flowchart in FIG. 3 and the table 20 in FIG. 4 showing the origin return operation.

When the power of the numerically controlled machine tool shown in Fig. 1 is turned on, the third
The origin return program shown in the figure starts.

When the home return program starts, the above calculation circuit 5
1, first executes step St, and determines whether or not the origin vicinity detection limit switch LSI is on.

Now, at the start of the home return program, the table 20 of the machine tool main body l (Fig. 1) is at the position shown, for example, by Pl in Fig. 4, and the home position detection limit switch LSI is on, and the first External control panel 5 shown in the figure
When a -JOG command is issued, the arithmetic circuit 51 advances the table 20 forward at a constant speed after accelerating it a certain distance, as shown in FIG. 4 (step S2).

When the table 20 moves forward, its current position changes. This current position data is stored in the mechanical coordinate system storage circuit 47. Then, the arithmetic circuit 51 performs step S
At step 3, the current position data of the table 20 stored in the machine coordinate system storage circuit 47 is read.

The arithmetic circuit 51 also determines in step S4 whether or not the origin vicinity detection limit switch LSI is on. If it is determined in step S4 that the origin detection limit switch LSI is on, the arithmetic circuit 51 executes step S5. Then, the value obtained by subtracting the current position data of table 20 from the return failure monitoring position data (setting value "2") of the near-home detection limit switch LSI is not negative (minus), that is, this subtraction value is zero or positive (plus ), step S above
3. Repeat the loops of S4 and S5. In this state, if the near-origin detection limit switch LSI does not turn off and becomes (set value r2J) - (current value) <0, this means that the table 20 indicates the near-origin detection limit switch LSI.
Even if the SI moves forward past its normal operating position, this means that the origin detection limit switch LSI continues to be turned on as shown by the dotted line in FIG.
1 outputs a signal indicating that the near-origin detection limit switch LSI is defective to the external control panel 5 in step S6, informs the operator of the return failure number of the near-origin detection limit switch LSI, and in step S7 performs numerical control work. Stop after stopping the machine.

On the other hand, step S6. When the origin detection limit switch LSI is turned off while the loop of S4 and S5 is being repeatedly executed, the arithmetic circuit 51 proceeds to execute each step from step 88 onwards.

Incidentally, when the origin vicinity detection limit switch LSI is off at the start of the program shown in FIG. 3, each step from step 88 onward is executed directly from step S1.

The table 20 is an origin detection limit switch LSI.
When the vehicle passes the position P, where the motor is turned off, the vehicle moves forward for a while while decelerating and then stops (see Fig. 4).

In this state, when the origin return command signal is manually input from the external control panel 5 to the arithmetic circuit 51 (step S8), the arithmetic circuit 51 transmits the machine coordinate system memory circuit 47 in step S9.
Read the current position data of Hable 20 stored in .

The arithmetic circuit 5I also determines in step SIO whether or not the origin deceleration position detection limit switch LS2 is on. If it is determined in step SIO that the origin deceleration position detection limit switch LS2 is on, the arithmetic circuit 51 executes step S11. Then, from the return failure monitoring position data (setting value "l") of the origin deceleration position detection limit switch LS2, table 20
The value obtained by subtracting the current position data of is not negative (minus),
That is, when this subtraction value is zero or positive, step S9. Repeat the loop of SlO and Sll. In this state, the origin deceleration position detection limit switch LS2 does not turn off and (set value rN) - (
If the current value) becomes 0, this means that even if the table 20 advances beyond the normal operating position P4 of the home deceleration detection limit switch LS2, the home deceleration position detection limit that was turned on when the table 20 reached position P3 switch LS2
This means that it continues to be turned on as shown by the dotted line in FIG.
The origin deceleration detection limit switch LS2 is installed on the external control panel 5.
A defective signal is output, informing the operator of the return failure of the origin deceleration detection limit switch LS2, and at the same time, in step S7, the numerically controlled machine tool is stopped.

On the other hand, step S9. When the origin deceleration position detection limit switch LS2 is turned off while the SIO and Sll loops are being repeatedly executed, the arithmetic circuit 51
In step S13, it is determined whether the return to the origin is completed.

Then, the table 20 stops at the first pulse P from position P in FIG. The return-to-origin completion lamp (not shown) of No. 5 is turned on, and the return-to-origin is completed. If it is determined in step S13 that the return to origin is not completed, and if an error in return to origin occurs for some reason (step 5I5), the numerically controlled machine tool is stopped (step S7) and then stopped.

As described above, the origin detection limit switch LS
When a return failure occurs in I and the origin deceleration detection limit switch LS2, the external control panel 5 warns the operator of the return failure, and at the same time, the numerically controlled machine tool also stops. Thereby, it is possible to easily know the origin return failure.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of an embodiment of a defect detection device for a position detector of a numerically controlled machine tool according to the present invention, and Fig. 2 is an explanatory diagram of the machine tool main body of the numerically controlled machine tool of Fig. 1. , Fig. 3 is a flowchart of defect detection of the defect detection device of the position detector of the numerically controlled machine tool shown in Fig. 1, and Fig. 4 shows the operation of the main parts when the numerically controlled machine tool shown in Fig. 1 returns to the origin. It is an explanatory diagram. ■... Machine tool body, 2... Numerical control device, 3...
・Motor, 4...Speed servo amplifier, 5...
・External control panel, 20...Table, 27...Drive shaft, 33...Pulse generator, 35.37.
...Cam part, 47...Machine coordinate system storage circuit, 47a...Power failure protection circuit, 48...Origin point vicinity data storage circuit, 49...Origin deceleration data storage circuit, LSI...Origin vicinity detection Limit switch, LS2・
・・Home deceleration position detection limit switch. Patent applicant: Mazda Motor Corporation agent Patent attorney: 2 people, Aohaku and Sogai, Figure 4, 1 child

Claims (1)

[Claims] (1) A drive shaft having an incremental pulse generator, a table that can be moved back and forth by the operation of the drive shaft, and a limit switch that is placed at a predetermined position on the movement trajectory of the table to detect the movement position of the table. A defect detection device for a position detector of a numerically controlled machine tool, comprising: current position detection means for detecting the current position of the table from the origin when the table returns to the origin; and current position detection means for detecting the current position of the table from the origin; Calculate the deviation between the current position of the table detected by the limit switch operating position storage means storing the operating position and the current position detection means and the normal operating position of the limit switch stored in the limit switch operating position storage means. and return failure detection means for detecting return failure of the limit switch.