Numerical control device

Abstract

A numerical control device that controls, based on a program, a five-axis machine tool that drives a tool tip point of a tool using axes including three straight axes and two rotary axes to perform machining on a workpiece mounted on a table, the numerical control device comprising: - a command analysis unit configured to read and analyze a block of the program and output motion command data generated based on the analysis result, - an interpolation unit configured to generate interpolation data by performing interpolation processing based on the motion command data and to output the generated interpolation data, - a servo control unit configured to control a servo motor that controls the axes based on the interpolation data, - a path displacement determination unit configured to based on the motion command data and the interpolation data, calculate a distance between a program command path instructed by the program and the tool tip point of the tool after adding movement amounts of the axes in this control period to current positions of the axes, the current positions of the axes being obtained based on feedback by the servo control unit from the servo motor, and to determine whether the calculated distance is equal to or greater than a predefined permissible amount, and - an alarm unit configured to issue an alarm when the path displacement determining unit determines that the distance is equal to or greater than the predefined allowable amount.

Description

Background of the invention 1. Field of the invention

[0001] The present invention relates to a numerical control device, and more particularly to a numerical control device that detects a displacement of a moving path of a tool. 2. Description of the related prior art

[0002] In a five-axis machine tool, a control point trajectory is obtained for a commanded tool tip trajectory by taking into account the rotation of a tool and the rotation of a table. By causing a motor to operate on the control point trajectory, a tool tip of an actual machine finally operates on the commanded trajectory (e.g., Japanese Patent Laid-Open No. 2003-195917 or the like). Although there is a numerical control device for obtaining a tool tip trajectory from a control point trajectory (e.g., Japanese Patent Laid-Open No. 2011-43874), this tool is directed toward verification after machining completion, not toward preventing erroneous operation during machining.

[0003] There is a case where, during automatic operation for workpiece machining using a five-axis machine tool, an operator interrupts the automatic operation and switches the operation to manual operation to change a tool or confirm a machining state. As long as the operator needs to move a tool from a position when the automatic operation is interrupted by manual operation to change the tool or confirm the machining state, there is a problem that if the operator moves a tool tip to an incorrect position after reaching the target (without returning the tool tip to the original position after manual operation) and restarts machining, the actual tool tip position will deviate from the commanded trajectory, causing erroneous cutting or machine deterioration. Summary of the invention

[0004] As in Fig. 1, the present invention solves the above-described problem by providing a numerical controller with a function of obtaining a tool tip position with respect to a control point position to be output by the numerical controller by performing a calculation reverse of the normal calculation based on a rotary axis position and a machine tool length, calculating a distance between the obtained tool tip position and a program command path, and, when the calculated distance deviates by an amount equal to or greater than an allowable amount, outputting an alarm without outputting a movement pulse to the control point position to stop the automatic operation.By constantly performing this monitoring during machining, the numerical control device of the present invention can prevent erroneous cutting and machine deterioration caused by an unexpected problem.

[0005] The numerical control device of the present invention controls, based on a program, a five-axis machine tool that drives a tool tip point of a tool that performs machining on a workpiece mounted on a table using axes including three straight axes and two rotary axes, and comprises a command analysis unit configured to read and analyze a block of the program and output motion command data generated based on the analysis result, an interpolation unit configured to generate interpolation data by performing interpolation processing based on the motion command data and output the generated interpolation data, a servo control unit configured to control the axes based on the interpolation data, a path displacement determination unit configured toafter adding movement amounts of the axes in this control period, based on the movement command data, the interpolation data, and the current positions of the axes, calculating a distance between a program command path instructed by the program and a tool tip point of the tool and determining whether the calculated distance is equal to or greater than a predefined allowable amount; and an alarm unit configured to issue an alarm when the path displacement determination unit determines that the distance is equal to or greater than the predefined allowable amount.

[0006] According to the present invention, by constantly monitoring the displacement of the web during processing, it is possible to prevent erroneous cutting and machine deterioration caused by an unexpected problem. Brief description of the drawings

[0007] The above and other objects and features of the present invention will become apparent from the following description of an embodiment with reference to the following accompanying drawings. Fig. 1 is a diagram showing a case where a tool tip point is moved from a program command path; Fig. 2 is a diagram explaining a displacement of a trajectory of the tool tip point assumed in the present invention; Fig. 3 is a figure (1) explaining a method for calculating a distance between the program command path and the tool tip point; Fig. 4 is a figure (2) explaining a method of calculating a distance between the program command path and the tool tip point; Fig. 5 is a figure (3) explaining a method of calculating a distance between the program command path and the tool tip point; Fig. 6 is a schematic hardware configuration diagram of a numerical control device according to an embodiment of the present invention; and Fig. 7 is a schematic functional block diagram of the numerical control device according to an embodiment of the present invention. Detailed description of the preferred embodiments

[0008] An embodiment of the present invention will be described below in conjunction with the drawings. First, using Fig. 2 to Fig. 5 describes the basic features of a path displacement detection function of the present invention.

[0009] Fig. Fig. 2 is a diagram explaining a displacement of a path of a tool tip point assumed in the present invention. It should be noted that Fig. 2 illustrates a program command path between respective program command points by a straight line for convenience of description. The present invention assumes a numerical control device that controls a five-axis machine tool disclosed in Japanese Patent Laid-Open No. 2003-195917, Japanese Patent Laid-Open No. 2011-43874, or the like.A numerical control device of the present invention outputs an alarm to stop automatic operation without adding movement amounts to respective axes (outputting a movement pulse) when, in moving a tool tip point to a program command point instructed by each block of an executed program, a movement target point to which the tool tip point is to be moved in a current control period is away from the program command point by an amount equal to or greater than a predefined allowable amount.

[0010] In the example of Fig. 2 shows an example in which an operator during the execution of a block N2 in performing an automatic operation according to a method shown in a lower section of Fig. 2 interrupts an automatic operation and performs a manual operation, and the operator moves a tip of a tool to an incorrect position after the manual operation and restarts the automatic operation.At this time, the numerical control device of the present invention calculates a distance between a program command path drawn through the tool tip point according to a command of block N2 when the automatic operation were to continue and a position of the tool tip point obtained based on a position of a control point when movement amounts to be added to respective axes in a current control period are added to a current position of the control point, and, when the calculated distance is equal to or larger than a predetermined allowable value defined in advance, outputs an alarm without adding the movement amounts to the respective axes (outputting a movement pulse) and stops the automatic operation.

[0011] The numerical control device of the present invention calculates a distance between the program command path and the position of the tool tip point T in each of three cases.

[0012] Fig. 3 is a diagram illustrating a method for calculating a distance between the program command path and the position of the tool tip point T when an intersection point P of a straight line including the program command path of a block executed when the automatic operation is interrupted and a vertical line extending from the position of the tool tip point T to the straight line is located between a start point and an end point of the program command path. Fig. 3, the numerical control device of the present invention sets a distance between the tool point T and the intersection point P of the program command path of the block executed when the automatic operation is interrupted, based on the position of the tool tip point T and the vertical line to the program command path, as a distance between the program command path and the position of the tool tip point T.

[0013] Fig. 4 is a diagram illustrating a method for calculating a distance between the program command path and the position of the tool tip point T when the intersection point P of the straight line comprising the program command path of the block executed when the automatic operation is interrupted and the vertical line extending from the position of the tool tip point T to the straight line is located beyond the start point of the program command path as viewed from the end point of the program command path. Fig. 4, the numerical control device of the present invention sets a distance between the tool point T and the start point of the program command path as the distance between the program command path and the position of the tool tip point T.

[0014] Fig. 5 is a diagram illustrating a method for calculating a distance between the program command path and the position of the tool tip point T when the intersection point P of the straight line comprising the program command path of the block executed when the automatic operation is interrupted and the vertical line extending from the position of the tool tip point T to the straight line, as viewed from the start point of the program command path, is located beyond the end point of the program command path. Fig. 5, the numerical control device of the present invention sets a distance between the tool point T and the end point of the program command path as the distance between the program command path and the position of the tool tip point T.

[0015] A configuration of the numerical control device according to an embodiment of the present invention will be described below.

[0016] Fig. 6 is a hardware configuration diagram illustrating the main parts of the numerical control device according to an embodiment of the present invention and a machine tool driven and controlled by the numerical control device. A CPU (Central Processing Unit) 11 provided in the numerical control device 1 is a processor that controls the numerical control device 1 as a whole. The CPU 11 reads a system program stored in a ROM 12 via a bus 20 and controls the entire numerical control device 1 according to the system program. A RAM 13 stores temporary calculation data, display data, various types of data input by the operator via a display / MDI unit 70 described later, or the like.

[0017] A non-volatile memory 14 is configured as a memory in which a stored state is maintained, for example, by a battery-backed power source (not shown), even when the numerical controller 1 is turned off. A machining program loaded via an interface 15 and a machining program input via a display / MDI unit 70 described below are stored in the non-volatile memory 14. Although a machining program operation processing program or the like to be used to operate the machining program is further stored in the non-volatile memory 14, these programs are expanded into the RAM 13 upon execution. Furthermore, various types of system programs for executing editing mode processing required for creating and editing the machining program are written in advance in the ROM 12.

[0018] The interface 15 is an interface for connecting the numerical control device 1 to an external device 72, such as an adapter. Machining programs, various types of parameters, or the like are loaded from the external device 72. Furthermore, the machining program edited in the numerical control device 1 can be stored in external storage devices via the external device 72. A PMC (Programmable Machine Controller) 16 performs control by outputting signals to peripheral devices (e.g., an actuator such as a robot hand for changing a tool) of the machine tool via an I / O (input / output) unit 17 using a sequence program included in the numerical control device 1.Furthermore, the PMC 16 receives signals from various types of switches and the like of an operation panel arranged on the body of the machine tool, performs necessary signal processing, and transmits the signals to the CPU 11.

[0019] The display / MDI unit 70 is a manual data input device including a display, a keyboard, or the like, and the interface 18 receives commands and data from the keyboard of the display / MDI unit 70 and transmits the commands and data to the CPU 11. An interface 19 is connected to an operation panel 71 including a manual pulse generator or the like.

[0020] An axis control circuit 30 for controlling axes provided in the machine tool receives a commanded movement amount of the axes from the CPU 11 and outputs the command for the axes to a servo amplifier 40. The servo amplifier 40 receiving this command drives a servo motor 50, which moves the axes provided in the machine tool. The servo motor 50 of the axes has a built-in position / speed detector, feeds a position / speed feedback signal from the position / speed detector back to the axis control circuit 30, and performs feedback control of the position and speed. It should be noted that, although in the hardware configuration diagram in Fig. 6 only shows one axis control circuit 30, one servo amplifier 40, and one servo motor 50, but in reality, these are provided according to the number of axes provided in the machine tool. For example, in a five-axis machine tool, axis control circuits 30, servo amplifiers 40, and servo motors 50 are provided corresponding to the three linear axes (X-axis, Y-axis, and Z-axis) and the two rotary axes (A-axis and C-axis).

[0021] A spindle control circuit 60 receives a main axis rotation command for the machine tool and outputs a spindle speed signal to a spindle amplifier 61. Receiving this spindle speed signal, the spindle amplifier 61 rotates a spindle motor 62 of the machine tool at a commanded speed to drive the tool.

[0022] A position encoder 63 is connected to the spindle motor 62, the position encoder 63 outputs a feedback pulse in synchronization with the rotation of the main axis, and the feedback pulse is read by the CPU 11.

[0023] Fig. 7 is a schematic functional block diagram of the numerical control device according to an embodiment of the present invention, in which a system program for implementing the above-described path displacement detection function in the Fig. 6 shown numerical control device 1. Each in Fig. The function block shown in Figure 7 is implemented by the CPU 11, which is Fig.6, executes the system program of the path displacement detection function, and controls the operation of each unit of the numerical control device 1. The numerical control device 1 of the present embodiment includes a command analysis unit 100, an interpolation unit 110, a servo control unit 130, a path displacement determination unit 140, and an alarm unit 150.

[0024] The command analysis unit 100 analyzes a block of machining commands included in the program read from a memory not shown to generate data related to a movement command, and outputs the generated data related to the movement command to the interpolation unit 110 and the path displacement determination unit 140.

[0025] The interpolation unit 110 generates interpolation data calculated by interpolating points on an instructed path instructed by the data related to the movement command of one control period based on the data related to the movement command received from the command analysis unit 100, and outputs the generated interpolation data (a movement amount of each axis of each control period) to the servo control unit 130.

[0026] The servo control unit 130 then controls the servo motor 50, which controls each axis to be controlled, based on the output of the interpolation unit 110.

[0027] The path displacement determination unit 140 obtains a program command path instructed by each block based on the data related to the movement command analyzed by the command analysis unit 100, executes the above-described processing based on the interpolation data (a movement amount of each axis of each control period) input from the interpolation unit 110 to the servo control unit 130 and a current position of each axis obtained from the servo motor 50 based on feedback or the like by the servo control unit 130, calculates a distance between a currently executed program command path and a position of a tool tip point after adding a movement amount of this control period to each axis, and determines whether the calculated distance is equal to or greater than a predefined allowable amount δ.When the distance between the currently executed program command path and the position of the tool tip point after adding the movement amount of this control period to each axis is equal to or greater than the predefined allowable amount δ, the path displacement determination unit 140 instructs the alarm unit 150 to issue an alarm.

[0028] When the alarm unit 150 receives a command to issue an alarm from the path displacement determination unit 140, the alarm unit 150 instructs the servo control unit 130 to stop adding the movement amount of each axis after that control period (the output of a movement pulse) and notifies the operator of the alarm by means of, for example, a sound, a light, or a display on the display device of the display / MDI unit 70.

[0029] Although the embodiment of the present invention has been described above, the present invention is not limited exclusively to the example of the above-described embodiment and can be implemented in various ways by making appropriate modifications.

Claims

[1] A numerical control device that controls, based on a program, a five-axis machine tool that drives a tool tip point of a tool using axes including three straight axes and two rotary axes to perform machining on a workpiece mounted on a table, the numerical control device comprising: - a command analysis unit configured to read and analyze a block of the program and output motion command data generated based on the analysis result, - an interpolation unit configured to generate interpolation data by performing interpolation processing based on the motion command data and to output the generated interpolation data, - a servo control unit configured to control a servo motor that controls the axes based on the interpolation data, - a path displacement determination unit configured to based on the motion command data and the interpolation data, calculate a distance between a program command path instructed by the program and the tool tip point of the tool after adding movement amounts of the axes in this control period to current positions of the axes, the current positions of the axes being obtained based on feedback by the servo control unit from the servo motor, and to determine whether the calculated distance is equal to or greater than a predefined permissible amount, and - an alarm unit configured to issue an alarm when the path displacement determining unit determines that the distance is equal to or greater than the predefined allowable amount.

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