JP2008046913A - Numerical control device of machine tools - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform overlap control in increased time efficiency by obtaining a start position of an overlap passage while working, reducing loads on a programmer and avoiding interference reliably between worked objects and tools. <P>SOLUTION: An interpretation part 12 of a numerical control device 10 identifies an overlap command from a working program and sends fast-forward information on two consecutive fast-forward blocks at a corner part of the worked objects to an overlap start position calculation part 23. A calculation part 23 calculates a start position of the overlap passage on the basis of two pairs of fast-forward information, shapes of the worked objects, and shapes of the tools. An overlapping timing control unit 24 monitors a blade tip position of the tools while fast-forward operation of one of the blocks and, when the blade tip position has reached the start position of the overlap passage, controls fast-forward operation of the other block. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a numerical control device that causes a workpiece and a tool to overlap each other on a path that does not interfere with each other in a machine tool.

Conventionally, two continuous rapid feed operations are overlapped at the corner of the workpiece, and the workpiece and the tool are overlapped on a path that does not interfere with each other, reducing the rapid feed time without cutting and improving machining efficiency. The technology to do is known. For example, in Patent Document 1, a programmer creating an NC program calculates a “bypass amount” (overlap amount) of one fast-forwarding block based on a tool shape and a workpiece shape, and calculates the calculated value in the NC program. And a control method and apparatus for relatively moving the workpiece and the tool on the “short path” (overlap path) by executing this program.
JP-A-6-180605

  This prior art will be described in accordance with a YZ plane machining model illustrated in FIGS. As shown in FIG. 2, in this machining model, an overlap route R1 is set between the fast-forward block N1 and the fast-forward block N2 that are continuous at one corner of the workpiece W. In the other corner portion of the workpiece W, an overlap route R2 is set between the fast-forward block N5 and the fast-forward block N6. For these overlap paths R1, R2, conventionally, the programmer has previously specified the overlap amounts Q1, Q2 in the NC program.

  When this NC program is executed, if it is determined that the fast-forward block is continuous, as shown in FIG. 3, the remaining amount of movement to the target position in the Y-axis direction (area of the hatched portion) is calculated in the fast-forward block N1. When the remaining movement amount reaches the overlap amount Q1 designated in advance (timing T1), movement in the Z-axis direction in the fast-forward block N2 is started, and the tool T and the workpiece W are moved on the overlap route R1. Relative feed. The same control is performed with respect to the overlap route R2, and in the fast-forward block N5, when the remaining movement amount to the target position in the Z-axis direction reaches the overlap amount Q2 designated in advance (timing T2), the fast-forward block The movement in the Y-axis direction at N6 is started.

  According to the conventional control method, the fast-forwarding time of the corner portion can be shortened by overlapping two consecutive fast-forwarding operations. However, according to the conventional method, it has been necessary for the programmer to calculate overlap amounts Q1 and Q2 suitable for the shapes of the workpiece and the tool in advance and specify them in the NC program. For this reason, each time the shape of the workpiece or the type of tool changes, there is a trouble of calculating the overlap amount, which increases the burden on the programmer. In addition, when the shape of the corner is complex, in order to avoid interference between the tool and the workpiece, it is necessary to specify a small overlap amount to ensure safety, reducing the effect of reducing non-cutting time There was also the problem of doing.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a numerical control device that can determine the start position of an overlap operation during the execution of an NC program, reduce the burden on the programmer, and can perform safe and time-efficient overlap control. It is in.

  In order to solve the above-described problems, the numerical control apparatus of the present invention controls two machine tools so that a workpiece and a tool overlap each other in a path where they do not interfere with each other by overlapping two rapid feed operations. A device for storing a tool shape and a workpiece shape, a means for interpreting an overlap command for overlapping two consecutive rapid traverse operations, and a start position of an overlap path according to the overlap command. The means for calculating based on the stored information of the tool shape and the workpiece shape, and when the relative position between the workpiece and the tool reaches the start position of the overlap path during one of the fast feed operations, the other rapid feed operation is started. Means.

  Here, the overlap command is a command for setting an overlap operation between two rapid feed operations when the rapid feed operation is continuous. Preferably, the overlap command is a cutting feed command and a rapid feed command. In the NC program to be included, it may be specified in association with the fast-forward command. Apart from this, an overlap command may be key-inputted on the operation panel of the numerical controller by the MDI (manual data input) method, or may be set in advance in the numerical controller as a parameter.

The start position of the overlap path is the start position (P1, P2) of the path (overlap path R1, R2 illustrated in FIG. 2) in which the workpiece and the tool can move relative to each other without causing interference. Of the two consecutive fast-forwarding operations, it is obtained by calculation during the preceding fast-forwarding operation. By determining this start position, the distance (overlap amount Q1, Q2) between the start position and the target position of each feed axis is determined, and the overlap path is also determined based on the start position and the acceleration / deceleration of each feed axis. Determined. The overlap path can be a straight line or a curved line depending on the corner shape of the workpiece.

  In addition, the numerical control apparatus of the present invention is characterized by comprising means for simulating a change in the workpiece shape based on the cutting information and updating the storage information of the workpiece shape according to the result of the simulation. More specifically, the simulation means relatively moves the workpiece and the tool on the virtual model on the basis of the workpiece shape and tool shape storage information and the orthogonal three-axis cutting information, and machining by the tool. The cutting amount of the workpiece is calculated in real time, and the storage information of the workpiece shape is sequentially updated based on the calculation result.

  According to the numerical control device of the present invention, since the start position of the overlap path is calculated during machining, it is not necessary to specify the overlap amount in advance when creating the NC program, and the burden on the programmer is reduced. In addition, there is an effect that time-efficient control can be executed by accurately calculating the maximum overlap amount within a range in which the workpiece and the tool do not interfere with each other.

  In addition, since the memory information of the workpiece shape is updated by simulation, when the same part of the workpiece is cut a plurality of times, the start position of the overlap path is sequentially changed according to the shape change due to cutting, There is an effect that the rapid feed time of cutting can be shortened in total.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a block diagram functionally showing the configuration of the numerical controller of this embodiment, FIG. 2 is a machining model diagram of the YZ plane illustrating the overlap control by the numerical controller, and FIG. 3 is a diagram of the machining model. FIG. 4 is a flow chart showing a method for calculating the start position of the overlap path, and FIGS. 5 to 9 show the calculation method in FIG. 2 as a machining model. It is a schematic diagram demonstrated according to it.

  As shown in FIG. 1, the numerical control device 10 of this embodiment includes a machining program storage unit 11 and a machining program interpretation unit 12. The interpretation unit 12 interprets the machining program stored in the storage unit 11 and sends a cutting feed command to the XYZ axis cutting feed function generation unit 13 in the case of a cutting feed command, and a fast feed command in the case of a fast feed command. Are sent to the corresponding X-axis fast-forwarding function generator 14, Y-axis fast-forwarding function generator 15 or Z-axis fast-forwarding function generator 16. Then, each function generating unit 13, 14, 15, 16 generates a movement position command at regular intervals, and the X-axis servo control unit 17, the Y-axis servo control unit 18, and the Z-axis servo control unit 19 work according to this command. The servo control of three orthogonal axes in the machine is executed.

  The numerical controller 10 also simulates a workpiece shape storage unit 20 for storing the shape of the workpiece, a tool shape storage unit 21 for storing the shape of a tool used for processing, and a shape change of the workpiece due to cutting. A workpiece cutting simulation unit 22 is provided. The simulation unit 22 reads the workpiece shape and the tool shape from the storage units 20 and 21, inputs a movement position command (cutting information) from the XYZ cutting feed function generation unit 13, and based on the information, the tool Are simulated on the virtual model, and the amount of workpiece removal is calculated in real time, and the storage information in the workpiece shape storage unit 20 is sequentially updated based on the calculation result.

  Further, the numerical control device 10 includes an overlap start position calculation unit 23 and an overlap timing control unit 24. The calculation unit 23 calculates the start position of the overlap route according to the overlap command. The overlap command is specified in association with the preceding command among two consecutive fast-forward commands in the machining program, and is identified by the machining program interpretation unit 12. Then, the interpreter 12 sends the fast-forward information of the fast-forward block including the overlap command and the fast-forward information of the subsequent fast-forward block to the calculator 23, and the calculator 23 stores the two sets of fast-forward information, the workpiece shape and the tool shape. The start position of the overlap route is calculated based on the information, and the calculation result is output to the overlap timing control unit 24 together with the two sets of fast-forward information. Even when the overlap command is an MDI input or a parameter is set, the interpretation unit 12 determines this, and when the fast-forward blocks are continuous, the fast-forward information of two consecutive fast-forward blocks is sent to the calculation unit 23, and the same It is sufficient to perform the process.

  The overlap timing control unit 24 first sends the fast-forward information of the preceding fast-forward block to the corresponding fast-forward function generators 14, 15, and 16 to generate a function corresponding to the feed information. Further, the control unit 24 receives the movement position command from the fast-forwarding function generation units 14, 15, and 16, monitors the current tool position, preferably the cutting edge position of the tool, and the overlap where the cutting edge position is obtained by the calculation unit 23. When the path start position is reached, the fast-forward information of the subsequent fast-forward block is sent to the corresponding fast-forward function generators 14, 15, and 16 to generate a function corresponding to the feed information.

  Thereby, as illustrated in FIGS. 2 and 3, at the first corner portion of the workpiece W, when the tool T reaches the overlap path start position P1 of the preceding fast-forward block N1 (timing T1). Thus, the acceleration of the Z-axis is started simultaneously with the deceleration of the Y-axis, and the tool T is fast-forwarded on the overlap path R1 (straight line a) by the overlap control on the YZ plane. Similarly, in the second corner portion, the overlap control on the ZY plane is started when the tool T reaches the start position P2 of the overlap path of the rapid traverse block N5 (timing T2). The tool T is fast-forwarded on the overlap route R2. In addition, although the example of a process which sends the tool T was shown in FIG. 2, the same control is applicable also when sending the workpiece W or sending both the workpiece W and the tool T.

  Next, a method for calculating the start position of the overlap route will be described with reference to FIGS. First, the slope a of the overlap path is calculated based on the fast-forward information of two consecutive fast-forward blocks (FIG. 4: S1). In the case of the machining models of FIGS. 2 and 3, since the overlap operation is composed of Y-axis deceleration and Z-axis acceleration, the overlap path is based on the acceleration / deceleration in the fast-forward information related to both feed axes. The slope a of R1 is calculated. Next, as shown in FIG. 5A, a straight line LA having a slope a passing through the end point (target position) of the preceding fast-forward block N1 is obtained (FIG. 4: S2).

  Subsequently, as shown in FIG. 5B, distances D1, D2, D3, and D4 between the plurality of vertices formed in the corner portion of the workpiece W and the straight line LA are calculated (FIG. 4: S3). Then, as shown in FIG. 6C, the vertex S having the shortest distance from the straight line LA is selected (FIG. 4: S4). Next, as shown in FIG. 6 (d), a line segment LB passing through the vertex S, parallel to the straight line LA and having the intersections with the fast-forward blocks N1 and N2 as both ends is obtained (FIG. 4: S5). Subsequently, as shown in FIG. 7E, a line segment LC obtained by translating the line segment LB in a direction away from the workpiece W by a predetermined distance (end point direction of the fast-forward block N1) is calculated (FIG. 4). : S6).

  Next, as shown in FIG. 7F, an envelope figure F when the tool T is moved on the line segment LC is obtained (FIG. 4: S7). Next, as shown in FIG. 8G, the contour C closest to the workpiece W is selected from the contours of the envelope figure F (FIG. 4: S8). In the case of the tool T shown in FIG. 8G, the contour line C coincides with the movement locus of the cutting edge point A. However, in the case of the tool T ′ shown in FIG. It matches the movement trajectory. Thereafter, as shown in FIG. 9 (i), the intersection K between the movement trajectory of the cutting edge point A when the contour C is superimposed on the line segment LC and the fast-forward block N1 is calculated as the start position of the overlap path (FIG. 9). 4: S9). In the case of the tool T ′ shown in FIG. 8 (h), the intersection point K ′ between the movement trajectory of the cutting edge point A different from the contour line C and the fast-forward block N1 is calculated as the start position of the overlap path.

According to the numerical control device 10 of the embodiment described above, the following operational effects can be obtained. (1) Since the start positions P1 and P2 (see FIG. 2) of the overlap path are automatically calculated during the execution of the NC program, it is not necessary to calculate the overlap amounts Q1 and Q2 in the NC program creation process. The burden on the programmer is reduced, and the time required to create the program can be greatly reduced.
(2) Even when the shape of the corner portion is complicated, the overlap path start positions P1 and P2 can be accurately obtained without calculation errors, and it is possible to reliably avoid interference between the workpiece W and the tool T. Machine damage can be prevented in advance.

(3) Since the maximum overlap amount can be accurately calculated within a range where the workpiece W and the tool T do not interfere with each other, it is possible to efficiently execute the overlap control with little dead time and high safety.
(4) The tool cutting simulation unit 22 updates the workpiece shape storage information in real time based on the cutting information. Therefore, when finishing the same part of the workpiece W after rough cutting, The overlap path start positions P1 and P2 are sequentially changed in accordance with the shape change due to cutting, and the ratio of the non-cutting rapid feed time to the total machining time can be greatly reduced.

It is a functional block diagram of a numerical controller showing an embodiment of the present invention. It is a processing model figure which illustrates overlap control. It is a speed control figure which shows the example of control of rapid feed speed. It is a flowchart which shows the calculation method of an overlap start position. It is a schematic diagram explaining the process of step S1-S3 of FIG. It is a schematic diagram explaining the process of step S4, S5 of FIG. It is a schematic diagram explaining the process of step S6, S7 of FIG. It is a schematic diagram explaining the process of step S8 of FIG. It is a schematic diagram explaining the process of step S9 of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Numerical control apparatus 12 Machining program interpretation part 20 Workpiece shape memory | storage part 21 Tool shape memory | storage part 22 Workpiece cutting simulation part 23 Overlap start position calculation part 24 Overlap timing control part W Workpiece T Tool R1, R2 Overlap path | route P1, P2 Overlap start position

Claims (3)

  Means for storing a tool shape and a workpiece shape in a numerical control device for controlling a machine tool so that two continuous rapid feed operations overlap and the workpiece and the tool overlap on a path that does not interfere with each other Means for interpreting an overlap command for overlapping two consecutive fast-forward operations, and means for calculating the start position of the overlap path based on the stored information of the tool shape and the workpiece shape according to the overlap command; A numerical control apparatus comprising: means for starting the other rapid feed operation when the relative position between the workpiece and the tool reaches the start position during the rapid feed operation.   2. The numerical controller according to claim 1, wherein the overlap command is specified in association with a fast feed command in an NC program including a cutting feed command and a fast feed command. The numerical control apparatus according to claim 1, further comprising means for simulating a change in the workpiece shape based on cutting information and updating storage information on the workpiece shape according to a result of the simulation.

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