JPH10254520A - Original point returning method for nc control axis - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the original point returning method of an NC control axis capable of improving the setting workability of the detector of a machine original point in the narrow movable range of the control axis and returning to an original point without interfering with a material to be worked. SOLUTION: In this original point returning method of the NC control axis provided with an incremental encoder 44, the NC control axis provided with the movable range of less than 10mm is moved in the direction of the machine original point at a first prescribed speed, stopped when a touch switch 48 is operated during movement, moved for a first prescribed distance in the direction of separating from the machine original point thereafter and then, immediately stopped when the touch switch 48 is operated again in the middle of being moved for a second prescribed distance at a second prescribed speed in the direction of the machine original point again and the stopped position is defined as the original point. Also, it is preferable that the second prescribed speed is slower than the first prescribed speed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of returning to the origin of an NC control axis, and more particularly to a method of returning to the origin with high accuracy when the movable range of the control axis is narrow.

[0002]

2. Description of the Related Art Conventionally, in a machine tool or a processing apparatus by NC control, an incremental position encoder or the like is often used as a position detector of an NC control axis. In order to perform position feedback by this incremental encoder and perform position control to accurately move each control axis to an absolute coordinate position commanded by an NC program stored in an NC control device such as the machine tool, etc. In addition, it is necessary to perform the home return operation before performing the first NC control immediately after the power is turned on. By performing the home position return operation, the mechanical origin mechanically set at a predetermined absolute position and the absolute coordinate position on the control specified in the NC program can be associated one-to-one. I have. For the purpose of improving workability, many return methods for completing such an origin return operation in a short time have been conventionally proposed.

For example, Japanese Patent Publication No. 61-124124 discloses a means for detecting a fine origin set near the mechanical origin for each control axis of the NC machine tool, and a means for detecting the fine origin set immediately before the fine origin. Means for detecting the coarse origin,
The control body of the NC machine tool is moved toward the fine origin by an origin return operation, and is moved in the same direction even after the coarse origin is detected, and is moved in the opposite direction when the fine origin is detected. A method of returning to the fine origin again at a very low speed when the fine origin is no longer detected and stopping when the fine origin is detected again, and using this stop position as the mechanical origin, is disclosed. In this case, the coarse origin is detected by a limit switch, and the fine origin is detected by a position detector such as a position encoder. This home position return operation enables accurate home position return in a short time.

[0004]

However, if the movable range of the control axis is restricted to a very narrow range at the time of return to origin, the return to origin cannot be performed by the above-mentioned conventional return to origin method. Alternatively, there is a problem that it takes a very long time to install the limit switch and the position encoder. For example, when cutting the inner surface of a non-circular workpiece such as a piston ring by NC control, it is necessary to return the origin of the control axis on the inner surface within a very narrow moving range. The restriction on the movement range of the control axis in the inner surface machining in this case will be described below in detail with reference to FIGS.

FIG. 4 is a view showing a workpiece before machining the inner surface and the outer surface of the piston ring and a ring shape after the machining. In FIG. 1, a workpiece 1 is a hollow material having a substantially cylindrical shape, and a plurality of ring members 2 having a predetermined height L1 corresponding to a desired piston ring groove width are stacked. Then, both end surfaces of the workpiece 1 (in the illustrated example,
A support device, which will be described later, is provided on the upper and lower end surfaces), and the workpiece 1 is supported by the support device from both end surfaces with a predetermined magnitude of clamping force. Further, a tool 4 for cutting an inner surface is provided in a hollow portion of the workpiece 1, and a tool 5 for cutting an outer surface is provided outside the workpiece 1. While the work piece 1 is supported by the support device, the work piece 1 is rotated around the rotation axis O in the illustrated direction, for example, in the direction of arrow 13, and the tools 4, 5 are reciprocated in the direction of arrow 11 in synchronization with this rotation. The plurality of rings 3 are manufactured by driving the workpiece 1 in the axial direction (for example, the direction of arrow 12 in the drawing). Although the ring 3 has a substantially heart shape, a portion P corresponding to a concave portion on the outer periphery thereof is cut off by a cutting device (not shown) and removed to complete the piston ring.

FIG. 5 is a front view showing an example of a piston ring processing machine for processing as described above. Bed 2
A column 22 is installed at a substantially central rear part of the upper part of the first part 1,
In front of the column 22, a Z-axis supported movably in the axial direction (Z-axis direction) of the workpiece 1 by a guide rail (for example, a ball-type linear guide or the like) laid on the front surface of the column 22. A slide 25 is provided. Further, a Z-axis motor 24 composed of, for example, a servomotor or the like is disposed on the upper portion of the column 22. The Z-axis motor 24 vertically drives the Z-axis slide 25. The Z-axis motor 24 has a Z-axis slide 2
5 is provided with a Z-axis position sensor 26 that detects the position in the Z-axis direction, for example, an encoder or the like.

In the Z-axis slide 25, the workpiece 1
A support device is provided for clamping and supporting the upper work support means 32 and the lower work support means 33, which are vertically separated from each other and arranged at positions facing each other. It is configured. The two support means are rotatably supported in the same direction by a drive transmission means such as a gear train (not shown). The drive means is driven by a C-axis motor 31 such as a servomotor mounted on the upper portion of the column 22. It is configured to be rotated synchronously via the transmission means. The C-axis motor 31 is provided with a C-axis position sensor 34 that detects the rotational position of the upper work support means 32 and the lower work support means 33 in the C-axis direction, for example, an encoder or the like.

The upper work support means 32 is supported so as to be vertically movable, and is vertically moved by a hydraulic cylinder (not shown) provided above the Z-axis slide 25. Due to the expansion and contraction of the hydraulic cylinder, the workpiece 1 can be clamped between the upper clamp head 32a provided below the upper work support means 32 and the lower clamp head 33a provided above the lower work support means 33. It has become.

An outer surface processing means 70 for processing the outer surface of the workpiece 1 is disposed substantially in the middle of the column 22. The outer surface processing means 70 includes the tool 5 attached to the tip end.
And the tool support means 72 attached to the column 22 and capable of moving the tool support means 72 in a horizontal direction and in a direction (X direction) to approach or separate from the workpiece 1. X guide means 73 for guiding
An X-axis motor 71, such as a servomotor, attached to the guide means 73 via a cover 74, and a ball screw, for example, that transmits the rotational force of the X-axis motor 71 in the moving direction of the tool support means 72. Transmission means 75
And Further, the X-axis motor 71 is provided with an X-axis position sensor 76 which is configured by, for example, an encoder or the like and detects the position of the tool 5 in the X-axis direction. And this X
The rotation of the shaft motor 71 moves the tool support means 72 in the X direction so that the outer surface of the workpiece 1 can be cut by the tool 5.

Further, an inner surface processing means 90 for processing the inner surface of the workpiece 1 is provided above the bed 21 and in front of the column 22. The inner surface processing means 90 is provided in a hollow portion of the workpiece 1 and supports a tool 4 attached to an upper end thereof, a boring bar 93, a U-axis slide 92 supporting the boring bar 93, A guide rail 94 for supporting the U-axis slide 92 in a horizontal direction and movably in a direction approaching or separating from the workpiece 1 (U-axis direction); , And a U-axis motor 91 composed of, for example, a linear motor or the like. Also,
A U-axis position sensor 95 for detecting the position of a U-axis slide 92 is provided near the guide rail 94.
The axis position sensor 95 is constituted by, for example, a linear scale or the like. The upper end of the boring bar 93, that is, the position of the tool 4 is set so as to enter the hollow portion of the workpiece 1, and by driving the U-axis motor 91, the tool 4 The inner surface can be cut.

As described above, the boring bar 93 is provided on the inner surface machining axis (U axis) of the piston ring.
Since the home return operation must be performed in a state where the boring bar 93 is inserted into the hollow portion, it is necessary to prevent the boring bar 93 from interfering with the workpiece 1. Since the workpiece 1 must be rotated at high speed (C axis) and the U axis must be controlled in complete synchronization with the rotation angle, the rigidity of the boring bar 93 needs to be increased. The outer diameter dimension of the boring bar 93 is inevitably large so as to obtain a predetermined rigidity. As a result, there is no margin in the distance between the inner surface of the piston ring, the outer surface of the boring bar 93, and the tip position of the tool 4, and the movable range of the U-axis is very narrow, for example, 10 mm or less.

In the case where the movable range of the control axis is restricted to a very narrow range at the time of the home return, a conventional home return method disclosed in Japanese Patent Publication No. 61-124124 described above. Then, the following problems have arisen. 1) There is no room in a narrow movable range for securing a space for installing a limit switch or the like for detecting the coarse origin. Even if a limit switch or the like can be installed, the limit switch or the like is operated for a long distance, so that the limit switch is often turned on from the start of the home position return. Therefore, it is impossible to start moving at a high speed toward the fine origin, and the origin return operation cannot be performed.

2) When an encoder for detecting a fine origin is mechanically installed, an incremental switch is used after detecting a limit switch or the like at a coarse origin to reduce the moving speed of the control axis to a predetermined medium speed. It is necessary to install the encoder so that one rotation detection signal of the encoder is detected. Therefore, it is necessary to adjust the positional relationship between the position of the limit switch and the one-rotation detection signal of the encoder so as to satisfy the above condition. However, since the movable range is very narrow (for example, 10 mm or less), it takes a very long time to perform the above-mentioned adjustment within this narrow range, and the work at the time of installing the limit switch and the incremental encoder is required. Sex is very bad.

3) When the fine origin is detected at a medium speed and stopped, and when the fine origin is moved in the reverse direction until the fine origin is turned off, a response delay of a control system such as a control program or a servo amplifier, and a steady-state deviation. In some cases, the coasting distance from the detection of the off state to the stop of the movement may be long depending on the size of the vehicle. In this case, since the movable range is narrow, there is a possibility that the workpiece 1 interferes with the boring bar 93 or the tool 4.

The present invention has been made in view of the above problems, and has a good workability of setting a detector at a machine origin and interferes with a workpiece in a narrow movable range of a control axis. It is an object of the present invention to provide a method of returning to the origin of an NC control axis which can return to the origin without any problem.

[0016]

In order to achieve the above object, an invention according to claim 1 is directed to a method for returning to the origin of an NC control shaft provided with an incremental encoder 44, which is not more than 10 mm. The NC control axis having a movable range is moved at a first predetermined speed in the direction of the machine origin, stops when the touch switch 48 is actuated during the movement, and thereafter moves in the direction away from the machine origin by a first predetermined speed. When the touch switch 48 is actuated again during the movement by the second predetermined distance at the second predetermined speed in the direction of the machine origin again at the second predetermined distance, the touch switch 48 is stopped immediately. And how to do it.

According to the first aspect of the present invention, the mechanical origin is detected by the touch switch, and the origin return is started at the first predetermined speed in the direction of the touch switch.
Therefore, since the origin can be returned from the vicinity of the touch switch, the origin can be returned even when the movable range is as narrow as 10 mm or less, for example. Further, since a position detector for the home position return operation is not used except for the touch switch, there is no need to adjust and install a positional relationship with other position detectors, so that the device can be easily installed. Therefore, workability at the time of installing the touch switch is improved. Furthermore, when the mechanical origin is finally detected, the moving distance in the direction of the origin is set to a predetermined distance that does not cause interference, so that interference between the tool and the workpiece (work) can be reliably prevented.

According to a second aspect of the present invention, there is provided a method for returning to the origin of an NC control axis according to the first aspect, wherein the second predetermined speed is lower than the first predetermined speed.

According to the second aspect of the present invention, the second moving to the mechanical origin to finally detect the mechanical origin.
Is preferably lower than the first predetermined speed, which enables highly accurate home return.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS.
An embodiment will be described in detail. FIG. 1 is a block diagram of the N according to the present invention.
FIG. 2 is a block diagram illustrating a hardware configuration for explaining a method of returning to the origin of a C control axis. The servo motor 43 is a motor for controlling the position and the moving speed of the control shaft, and can be constituted by, for example, a linear servo motor, an electric motor, a hydraulic motor, or the like. An incremental encoder (hereinafter, referred to as an encoder) 44 for detecting the position of the control axis is attached to the servo motor 43. The output shaft 45 of the servo motor 43 is connected to a control body 47, and the control body 47 is movable in the left-right direction in the figure. At the end of the path along which the control body 47 moves in the origin return direction 46, a touch switch 48 representing a mechanical origin is disposed so as to be operable in the movement direction of the control body 47. The touch switch 48 is moved and comes into contact with and pushes the operating lever 48a to be operated. Further, a fixed stopper 49 for stopping mechanically when the control body 47 is overrun is provided outside the operation lever 48a in the origin return direction 46.

The servo control command to the servo motor 43 is N
The incremental position signal output from the C control device 41 and output from the encoder 44 is output from the NC control device 41.
Has been entered. An operation signal (ON or OFF signal) of the touch switch 48 is input to the sequencer 42.

The sequencer 42 controls the operation sequence of the entire processing apparatus having the above-mentioned control axis, such as a piston ring processing machine, and performs a home return command and an automatic operation according to a predetermined sequence program which is set and stored in advance. The operation command of the control axis at the time is output to the NC control device 41. Further, the NC control device 41 stores a predetermined NC control program corresponding to the origin return command, the operation command of the control axis at the time of the automatic operation, and the like. Based on the NC control program, each control axis is controlled. Movement control.

Further, a mode selection switch 52 and a start switch 51 are connected to the sequencer 42.
The mode selection switch 52 is a changeover switch capable of selecting at least an origin return mode and an automatic operation mode, and each mode signal is input to the sequencer 42. The start switch 51 is an operation switch that starts an origin return operation and an automatic operation operation, and this start signal is input to the sequencer 42. Note that the mode signal and the start signal are not limited to the input method using the switch as described above, but may be a signal input from a host computer or the like through communication.

The operation at the time of returning to the origin in such a configuration will be described in detail below with reference to FIGS. FIG. 2 is a diagram for explaining the origin return method according to the present invention. First, an origin return mode selection signal is input to the sequencer 42, followed by a start signal. As a result, the sequencer 42 outputs a predetermined delay feed command to the NC controller 41, and the NC controller 41
3 to output a servo control command to move the control body 47 in the origin return direction 46 at a first predetermined speed V1 (usually a low speed). Then, when the control body 47 presses the operation lever 48a of the touch switch 48 to turn on the operation signal (point A in the drawing), the speed of the control shaft is reduced and temporarily stopped. Next, an NC control program (here, the program number is “0 0003”) stored in the NC control device 41 as shown in FIG. 3 is started.

FIG. 3 shows an example of an NC control program for performing origin return. According to the NC control program, in the sequence number N001, the current position (point B in the drawing) where the touch switch 48 is turned on is linearly interpolated in the forward direction of the U axis (that is, the direction opposite to the origin return direction 46). First predetermined distance L1 (here, 1
mm) at the first predetermined speed V1 (here, for example, 100 mm / min) to stop. Next, in the sequence number N002, the robot moves in the backward direction of the U-axis (that is, the origin return direction 46) at a second predetermined speed V2 (here, for example, 20 mm / min) lower than the first predetermined speed V1. Let it. In this case, if the operation signal of the touch switch 48 is turned on (point A in the drawing) during the movement of the designated second predetermined distance L2 (here, 1 mm), the movement is interrupted and stopped immediately. The control process shifts to the next sequence number N003. Then, in the sequence number N003, the NC control program ends, and
Complete the home return operation.

According to the above-described origin return operation, since the origin return can be started near the touch switch 48 indicating the mechanical origin, the return can be performed even if the moving distance for the return operation is very small. Further, since only the touch switch 48 needs to be used as a detector for setting the origin position, there is no need to consider the relationship with other detectors, and the origin position can be easily set. Workability can be improved. Further, after the touch switch 48 is operated for the first time at the time of home return, the touch switch 48 returns at a predetermined speed in the reverse direction by a first predetermined distance L1 (for example, 1 mm), and then returns to the home return direction by a second predetermined distance L2 (first 1 predetermined distance L1
When the touch switch 48 is turned on during the movement by the following distance (here, 1 mm), the touch switch 48 is stopped, and this position is set as the mechanical origin. As described above, since the allowable maximum value of the moving distance is specified near the mechanical origin, interference between the workpiece and the tool 4 or the boring bar 93 due to coasting or the like is eliminated.

In the sequence number N002 of the NC control program, the second predetermined speed V2 is lower than the first predetermined speed V1, but the present invention is not limited to this. Instead, both speeds may be equal. The second predetermined distance L2 is equal to the first distance L2.
May be shorter than the predetermined distance L1.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a hardware configuration for explaining an origin return method according to the present invention.

FIG. 2 is an explanatory diagram of an origin return method according to the present invention.

FIG. 3 shows an example of an NC control program for explaining an origin return method according to the present invention.

FIG. 4 is an explanatory diagram of a piston ring inner surface machining that requires origin return in a narrow movable range according to the present invention.

FIG. 5 is a front view showing an example of a piston ring inner surface processing machine according to the present invention, which needs to return to the origin in a narrow movable range.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Work material, 2 ... Ring material, 3 ... Ring, 4, 5 ... Tool, 11, 12, 13 ... Arrow, 21 ... Bed, 22 ... Column, 24 ... Z-axis motor, 25 ... Z-axis slide, 26 …
Z-axis position sensor, 31 C-axis motor, 32 upper work support means, 32a upper clamp head, 33 lower work support means, 33a lower clamp head, 34 C
Axis position sensor, 41 NC controller, 42 sequencer, 43 servo motor, 44 incremental encoder (encoder), 45 output shaft, 46 origin return direction, 47 control body, 48 touch switch, 48a
... operating lever, 49 ... fixed stopper, 51 ... start switch, 52 ... mode selection switch, 70 ... outer surface processing means,
71: X-axis motor, 72: Tool support means, 73: X guide means, 74: Cover, 75: Transmission means, 76: X-axis position sensor, 90: Inner surface processing means, 91: U-axis motor, 9
2: U-axis slide, 93: boring bar, 94: guide rail, 95: U-axis position sensor.

Claims (2)

[Claims] 1. A method for returning to the origin of an NC control axis provided with an incremental encoder (44), wherein the NC control axis having a movable range of 10 mm or less is moved in a direction of a machine origin at a first predetermined speed. Stops when the touch switch (48) is actuated during the movement, thereafter moves by a first predetermined distance in a direction away from the machine origin, and then moves again at a second predetermined speed in the direction of the machine origin. Wherein when the touch switch (48) is actuated again during the movement of a predetermined distance, the stop is immediately performed, and the stop position is used as the origin. 2. The method of claim 1, wherein the second predetermined speed is lower than the first predetermined speed.