JPS6365469B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for determining a tool evacuation and return path in a machine tool. Conventionally, when a tool abnormality occurs during automatic operation of an NC machine tool, the tool is replaced by stopping the machine and manually moving the tool to a predetermined evacuation position. When machining is restarted, the tool and NC tape are manually returned to the starting position of the program block corresponding to the part at the time the machine was stopped. Such operations are very time-consuming and troublesome. Therefore, it has been proposed to perform the above operations automatically, but as shown in JP-A-51-147077, simply retracting and returning the tool in one direction may cause interference between the tool and the workpiece. In addition, if the tool is to be retracted and returned in a manner that follows the contour of the machining surface as shown in Japanese Patent Publication No. 45-37709, a large-capacity memory means must be prepared to move from the machining start position to the retraction start position. Since all tool paths must be stored in the storage means, the device configuration becomes complicated and expensive. In view of this, the present invention provides a method capable of determining an appropriate tool evacuation and return path without interference without using a large-capacity storage means. Therefore, in the present invention, when an abnormality occurs in a tool in an NC machine tool, the first position D is moved from the current position C of the tool to the machining start side by a preset distance l along the machining surface of the workpiece, and a second position E, which is on a line segment parallel to the NC axis along the direction away from and passing through the first position D, and is away from the machined surface by a predetermined distance from the first position D; , the tool is evacuated from the current position C via the second position E, and after the abnormality of the tool is cleared, the tool is returned to the first position D via the second position E. That's what I do. Embodiments of the present invention will be described below with reference to the drawings. When carrying out the present invention, first, a block for tool evacuation and return mode selection is set in a block in the NC tape that requires the evacuation and return of the tool, or a block that effectively acts on that block.
NC information, such as M81, M82, M83, etc.
A code is inserted and this determines the mode for evacuation and return, that is, the basic way the tool moves. In addition, in this example, M81
indicates NC information for external diameter machining, M82 for end face machining, and M83 for evacuation and return mode selection for internal diameter machining. Tool retreat and return modes are determined depending on the type of machining, such as external machining, end face machining, and internal machining, and each of these modes also includes control procedures such as tool movement procedures and spindle rotation. ing. Further, each mode holds numerical values such as the evacuation start position and evacuation position required during the movement procedure as variables. The evacuation start position is determined by reading the current position of the tool when the tool evacuation position signal is received, and the evacuation position is set in the block where the NC tape is to be ejected or returned, or in the block before this block. It can be pre-stored or it can be inserted each time by manual input, for example a manual switch. Further, in each mode, parameters such as the necessary escape amount l during the tool evacuation and return path are stored in the block in which the evacuation and return are to be performed, or in a predetermined block before this block. The flowchart in FIG. 1 shows a procedure executed by an NC device, etc., which will be described later. In the NC device, each time a tool movement command is input, the command value is stored (set) in a storage means. Also, when NC information such as a G code or M code for setting the evacuation position A (see Figs. 3, 4, and 5) and evacuation position A are stored in the NC tape, stores its evacuation position. Note that whether or not to set the evacuation position is determined depending on whether or not the NC information such as the G code is present in the block. Further, if the NC information for setting a parameter and the parameter, for example, tool relief amount l, are stored in the NC tape, the parameter l is set. This parameter set is also similar to the above evacuation position, such as G code, etc.
This is determined based on whether or not NC information is included in the block. Next, it is determined whether there is an evacuation signal. This determination is made based on the presence or absence of NC information such as the M code, for example. If no save signal is input, normal NC operation is performed. That is, in the case of outer diameter machining shown in FIG.
It is moved from position P ₁ to cutting position P ₁ and then moved from position P 1 along a path 10 shown by a broken line. However, if the evacuation signal is not input, cutting along this path 10 is continued. On the other hand, for example, if a tool abnormality occurs for some reason at cutting position C shown in Fig. 2 and an evacuation signal is input, in this case, the NC information for evacuation mode selection is stored in the block currently being processed. It is determined whether or not there is. If there is a mode selection code M, then according to this mode M, the current position (abnormality occurrence position), NC command position (target position in the relevant block of the NC program, that is, the machining end position for the relevant block), and evacuation position Using parameters such as the escape amount, etc., the tool evacuation and return paths are determined as shown in Table 1 below.

[Table] In other words, when the save signal is input during the outer diameter machining shown in Fig. 3, the code M indicating the outer diameter mode is sent to the block currently being executed in the NC program.
81, the current position C shown in the figure
(X _C , Z _C ) to movement position E (X _D +2a, Z _D ), F
A tool retraction path C→E→F→A is determined, which reaches the retraction position A (X _A , Z _A ) via (X _A , Z _D ). Also, a return path A→F→E→D from the retreat position A through the movement positions F and E to the machining restart position D (X _D , Z _D ) is also determined at the same time. The tool 10 is moved along the above-described retraction path to the retraction position, where it is replaced with a normal tool. Then, when the return signal is input, the machine is moved along the return path to the machining restart position D. FIG. 4 and FIG. 5 show tool retraction and return paths during end face machining and inner diameter machining, respectively. In the case of end face processing, the current position C (X _C ,
Z _C ) → Movement position E (X _D , Z _D +a) → Movement position F
An evacuation path (X _D , Z _A ) → evacuation position A (X _A , Z _A ) is determined, and a tool return path from position A → F → E → machining restart position D (X _D , Z _D ) is determined. be done. In addition, during inner diameter machining, the current position C (X _C ,
Z _C ) → Movement position E (X _D -2a, Z _D ) → Movement position F
(X _D -2a, Z _A ) → Retract position A (X _A , Z _A ) is determined, and the tool return path is determined as position A → F → E → machining restart position D (X _D , Z _D ). A route is determined. In this manner, according to this embodiment, the tool retraction and return paths adapted to each machining mode are determined, and thereby the tool 1 can be retracted and returned in a manner that does not interfere with the tool 1 and the workpiece 2. In addition, since the machining restart position D is set to a position closer to the machining start side by the escape amount than the tool abnormality occurrence position C, sections C and D are reworked and the traces in the same section due to the tool abnormality are removed. removed. Note that the tool is moved diagonally in sections C and D for the following reason. In other words, for example, if the tool is installed obliquely counterclockwise with respect to the X-axis as shown in Fig. 2, the side end surface of the workpiece that the side surface of the cutting edge of the tool touches will also be inclined along the side surface of the cutting edge. become. This is because, in such a case, if the tool is retracted in a direction parallel to the X-axis, the tool will interfere with the workpiece, making it impossible to retract it. In Figures 3, 4, and 5, the position (X _B , Z _B ) is the NC command position (machining end point position) in the corresponding block, which is the machining restart position as described later. used to determine D(X _D , Z _D ). Furthermore, a is a parameter for determining the position E, and is set in advance according to the machining shape of the workpiece together with the relief amount. In Table 1, "fast" represents the rapid feed of the tool, and "cut" represents the cutting feed of the tool. Also, in the same table and Figures 3 to 5, the values for the X axis are expressed as "diameter values," so the actual size on the XZ coordinates is 1/2 of the indicated value. . For example, the actual coordinate value of position E in FIG. 5 is (X _D -2a)/2. Here, the method of determining the machining restart position D (X _D , Z _D ) will be explained with reference to FIG. 8. In the case of outer diameter machining, it is usual to perform the machining so that the machined surface is slightly tapered with respect to the Z axis, as shown in FIG. In the figure, the following relationship holds true. _{d 1 ' / d 1 = _ _} ^_ +d ₂ ′ ² ) ^1/2 = | d ₁ ′ | + | d ₂ ′ | …(2). Considering that X _B and X _C are expressed using the diameter values described above, |d ₁ '|=|X _B −X _C |/2 (3). Also, |d ₂ ′|= |Z _B −Z _C | …(4), so from equations (2), (3), and (4), l′= |X _B |−|X _C |/2+ The following relationship is obtained: |Z _B −Z _C | …(5). From equations (1) and (5), X _B −X _C /X _C −X _D = |X _B −X _C |/2/l+|Z _B −Z _C |/
l…(6) The following relationship is obtained, and from this, X _C −X _D = 2l(X _B −X _C )/|X _B −X _C |+2|Z _B −Z _C |…
(7) Therefore, the X coordinate X _D of the machining restart position D can be obtained from the following equation (8). _{X D = _ _ _ _ _}
(8) On the other hand, in the same figure, the following relationship also holds. d ₂ ′／d ₂ ＝Z _B −Z _C ／Z _C −Z _D ＝l′／l …(9) Therefore, from equations (5) and (9), Z _B −Z _C ／Z _C −Z _D = |X _B −X _C |/2/l+|Z _B −Z _C |/
l…(10) From this, Z _C −Z _D = 2l(Z _B −Z _C )/|X _B −X _C |+2|Z _B −Z _C |…
(11) Therefore, the Z coordinate Z _D of the machining restart position D can be obtained from the following equation (12). Z _D =Z _C +2l(Z _C −Z _B )／｜X _B −X _C |+2｜Z _B −Z _C ｜…
(12) Thus, the coordinates of the machining restart position D (X _D , Z _D )
can be obtained from equations (8) and (12). It is also clear from the above explanation that the machining restart position D (X _D , Z _D ) in the internal diameter machining shown in FIG. 5 is expressed by equations (8) and (12). Machining restart position D in end face machining shown in Fig. 4
(X _D , Z _D ) can also be obtained from the above equations (8) and (12) for the following reasons. That is, in the case of FIG. 4, the X-axis and Z-axis in FIG. 8 may be replaced with the Z-axis and the X-axis, respectively. In this case, the following equations (13), (14), (15), and (16), which correspond to equations (1), (3), and (4), hold true. d ₁ ′／d ₁ ＝Z _B −Z _C ／Z _C −Z _D ＝l′／l …(13) ｜d ₁ ′｜＝｜Z _B −Z _C ｜ …(14) ｜d ₂ ′｜＝ |X _B −X _C |/2 …(15) l′=|Z _B −Z _C |+|X _B −X _C |/2 …(16) Therefore, from equations (15) and (16), Z _B −Z _C /Z _C −Z _D = |Z _B −Z _C |/l+|X _B −X _C |/2/
The relationship l, that is, the same relationship as equation (10), holds, and equation (12) is derived from this. Also, since the relationship d ₂ ′/d ₂ =X _B −X _C ／X _C −X _D =l′/l (17) corresponding to equation (9) holds, this equation (17) and (16 ) equation, X _B −X _C /X _C −X _D = |Z _B −Z _C |/l+|X _B −X _C |/2/
The relationship l, that is, the same relationship as equation (6), holds, and from this, equation (8) is derived. As described above, the relationships in equations (8) and (12) also hold true in the case of end face processing. Next, a control device for implementing the present invention will be described. In FIG. 6, the numerically controlled machine tool 10 includes a chuck 11 that is rotationally driven, a movable table 13 that reciprocates in the Z direction along a guide 12, and this movable table 1.
The tool rest 14 is provided with a tool rest 14 that reciprocates on the tool rest 3 in the X direction, and the tool 1 is attached to the tool rest 14. The automatic tool exchanger 16 automatically exchanges the tool 1 that has been retracted to the retracted position A with a normal tool or chip stored in a tool magazine. The numerical control device (hereinafter referred to as NC device) 17 is
Based on the machining program input via the tape, predetermined operation commands are given to the numerically controlled machine tool 10 and the automatic tool changer 16. Further, the tool abnormality detection mechanism 18 functions to detect tool abnormality based on, for example, current or vibration of the spindle motor or the like. When machining the outer diameter of the workpiece 2 using the tool 1, an outer diameter machining program is input to the NC device 17. NC device 1 based on this program
The control signal output from 7 is passed through the changeover switch 20 and pulse distributor 21 shown in FIG.
23 (referred to as an axis servo motor), the tool 1 is moved from the origin P (X _p , Z _p ) shown in FIG. 2 and the outer diameter of the workpiece 2 is machined. A machining program is sequentially input to the NC device 17 for each unit block. Then, the target position included in the block currently being processed is stored in the register 27 of the storage device 25 as the position (X _B , Z _B ) of the processing end point B for the block. During machining, if a tool abnormality occurs at a certain position C (see Figures 3, 4, and 5), the tool abnormality detection mechanism 18 detects this and issues an abnormality signal _R1.
This signal is applied to both the NC device 17 and the changeover switch 20. When the abnormality signal R1 is input, the changeover switch ₂₀ changes from the normal position, that is, the position that sends the control signal from the NC device to the pulse distributor 21, to the abnormal position, that is, the position that applies the command from the sequence controller 24 to the pulse distributor 21. can be switched to the position. On the other hand, when the abnormal signal R ₁ is input, the NC device 17 stops outputting and the tool 1 at this time
The current position of , ie, the coordinates of the abnormality occurrence position C, is stored in the current position storage register 26 in the storage device 25 . The storage device 25 also includes a tool retraction position storage register 28 that stores the tool exchange position of the automatic tool changer 16, that is, the coordinates (X _A , Z _A ) of the retraction position A of the tool 1, and a register that stores the value a. 29 and an escape amount storage register 30 that stores the escape amount determined by the shape of the workpiece 2.
Equipped with: The contents of each of these registers 26 to 30 are applied to an arithmetic circuit 31. The arithmetic circuit 31 selects one of the outer diameter mode, end face mode, and inner diameter mode based on the mode signal _R2 from the NC device 17, and selects the first mode based on each input value using the arithmetic start command signal _R3 . The positions E, F, and D of the evacuation and return paths shown in the table are calculated, and the tool evacuation path and tool return path are determined based on the calculation results and the contents stored in the storage device 25. First, information about the evacuation route is added to the sequence controller 24. The sequence controller 24 outputs a signal corresponding to the input value and applies it to the changeover switch 20 and the pulse distributor 21. As a result, the pulse distributor 21
applies a predetermined pulse signal to each of the X-axis and Z-axis servo motors 22 and 23 to move the tool 1 diagonally from the abnormality occurrence position C to the first movement position E in rapid traverse,
Next, after moving from this first movement position E to a second movement position F, it is moved from this second movement position F to a retreat position A in the Z-axis direction. When the retracted position A is reached, the automatic tool changer 16
Add exchange command R ₄ to cause the tool to be automatically exchanged. When the tool changer 16 outputs the tool change completion signal R ₅ , the arithmetic circuit 31 adds tool return path information to the sequence controller 24 . As a result, the sequence controller 24 moves the tool 1 again in rapid traverse to the second movement position F and the first movement position E, and moves the tool 1 from this position E to the machining restart position D by cutting feed. . After the tool 1 moves to the machining restart position D, the sequence controller 24 cuts and feeds the tool 1 to the abnormality occurrence position, that is, the retreat start position C. In addition,
This cutting feed removes the traces in sections D and C (length l). At the end of the cutting feed, the sequence controller ₂₄ outputs an operation completion signal R7, and based on this signal, a restart command is given to the NC device 17, and the changeover switch 20 is switched to the normal position. Outer diameter machining based on the machining program is started again. As described above, according to the present invention, it is possible to determine an appropriate tool evacuation and return path without interference without storing the movement path of the tool during machining. Therefore, there is no need for large capacity storage means. Furthermore, since machining is started from a position that is a predetermined distance closer to the machining start side than the retraction start position, it is possible to remove traces on the cutting surface due to tool abnormalities.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing an embodiment of the method for determining tool retraction and return paths according to the present invention, and FIG. 2 is a conceptual diagram showing an example of a machining pattern for a workpiece.
Figures 3, 4, and 5 are conceptual diagrams showing the retraction and return paths of tools during outer diameter machining, end face machining, and inner diameter machining, respectively, and Figure 6 is a numerically controlled machine tool to which the present invention is applied. FIG. 7 is a block diagram showing an example of a control device for carrying out the method of the present invention, and FIG. 8 is an explanatory diagram used to determine the machining restart position. 1... Tool, 2... Workpiece, 10... Numerical control machine tool, 16... Automatic tool changer, 17...
NC device, 18... Tool abnormality detection mechanism, 20...
Changeover switch, 21... Pulse distributor, 22, 2
3...Motor, 24...Sequence controller, 25...Storage device, 31...Arithmetic circuit.

Claims (1)

[Claims] 1. When an abnormality occurs in a tool in an NC machine tool,
A first position D that is closer to the machining start side by a preset distance l along the machining surface of the workpiece from the current position C of the tool, and NC along the direction away from the machining surface.
A second position E, which is on a line parallel to the axis and passes through the first position D, and is away from the machined surface by a predetermined distance from the first position D, is determined, and the current position C is determined. A machine tool characterized in that the tool is evacuated from the machine via the second position E, and after the abnormality of the tool is cleared, the tool is returned to the first position D via the second position E. How to determine the tool evacuation/return path.