JP2004220307A - Numerical controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a numerical controller capable of carrying out precise speed control for making loads uniform. <P>SOLUTION: Interpolation data are calculated by interpolating a movement command (S1 to S3). Then, the interpolation data are recalculated in a cycle which is the same as an interpolation cycle for making cutting loads constant based on a spindle load or the servo load of a feeding shaft (S4). The corrected interpolation data are accelerated/decelerated, and outputted to the servo (S5, S6). The interpolation data are recalculated so that the loads can be made constant, and the corrected interpolation data are calculated so that the driving currents of the spindle motor or the servo motor of the feeding shaft can be made coincident with a reference value. The corrected interpolation data are calculated in each interpolation cycle so that it is possible to carry out precise speed control for making the loads constant. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a numerical control device for controlling machine tools, industrial machines, and the like.
[0002]
[Prior art]
As a method for optimizing the processing conditions, a method called AC (adaptive control) is employed. In this method, the feed rate is controlled in accordance with the servo load current and the spindle load current at the time of machining, so that machining is performed at an optimal machining speed. This method usually employs a method of controlling the feed speed by applying an override to the commanded feed speed according to the servo load current or the spindle load current.
[0003]
For example, a feed speed calculating means is provided to reduce the feed speed of the tool when the load current of the spindle motor reaches the set upper limit, and to increase the feed speed of the tool when the load current reaches the set lower limit to obtain a feed speed command. There is known a method of performing processing by interpolation processing based on a speed command (see Patent Document 1).
[0004]
In addition, experimentally determine the processing load based on data on the workpiece, such as the shape, dimensions, and material of the workpiece, data on the tools, such as the tool type, dimensions, material, and number of blades, and processing conditions such as the spindle rotation speed and feed rate. Is stored as a table or a function, a predicted load command is obtained from the table or the function according to the command position, and the obtained predicted load command is added to the acceleration command output from the speed command control unit for control. A method is also known (for example, see Patent Document 2).
[0005]
[Patent Document 1]
JP-A-6-297296 [Patent Document 2]
JP-A-9-47940
[Problems to be solved by the invention]
In the conventional method of controlling the feed rate by applying an override, the override signal is not usually subjected to high-speed signal sampling and is controlled at a relatively long time interval. The correction of the speed is delayed, and the control for keeping the load applied to the tool constant is delayed, so that it is difficult to control the load with high accuracy.
However, recently, for the purpose of extending the life of the tool, there has been an increasing demand to make the load applied to the tool constant during machining, and the speed is corrected as quickly as possible based on the servo load or the spindle load to make the load constant. It is desirable.
Therefore, an object of the present invention is to provide a numerical controller capable of responding to a change in load at high speed and performing precise speed control.
[0007]
[Means for Solving the Problems]
In a numerical control device that analyzes a movement command for a control axis to create interpolation data for each control axis and sends the data to a servo drive control unit, the invention according to claim 1 reads the interpolation data and performs a predetermined operation. The servo drive control section is provided with an interpolation data changing means for outputting corrected interpolation data later, so that the interpolation data once created can be corrected again. According to a second aspect of the present invention, the corrected interpolation data is calculated by the interpolation data changing means based on the load data of the servomotor driving the control axis. According to a third aspect of the present invention, the corrected interpolation data is calculated by the interpolation data changing means based on load data of a spindle motor for driving a spindle of the machine tool. As a result, the speed can be controlled so that the cutting load or the like is constant. Further, in the invention according to claim 4, the calculation by the interpolation data changing means is executed every interpolation cycle, and corrected interpolation data is output.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a block diagram of a numerical control device 100 as one embodiment of the present invention. The CPU 11 is a processor that controls the numerical control device 100 as a whole. The CPU 11 reads out a system program stored in a memory 12 composed of a ROM, a RAM, a CMOS memory backed up by a power supply, and the like via a bus 17, and controls the entire numerical controller according to the system program. The CMOS memory in the memory 12 stores a machining program read via the interface 13, a machining program input via the MDI / DiSPLAY unit 80, and the like. Based on this machining program, machining is performed by driving the servo motors and spindle motors of the respective feed axes of the X, Y, and Z axes.
[0009]
A PMC (programmable machine controller) 14 sends a signal to an auxiliary device of a machine tool (for example, an actuator such as a robot hand for tool change) via an I / O unit 15 by a sequence program built in the numerical controller 100. Output and control. In addition, it receives signals from various switches and the like of an operation panel provided in the main body of the machine tool, performs necessary signal processing, and passes the signals to the CPU 11.
[0010]
The MDI / DiSPLAY unit 80 is a manual data input device having a display, a keyboard, and the like. The interface 16 receives commands and data from the keyboard of the MDI / DiSPLAY unit 80 and passes them to the CPU 11.
[0011]
The axis control circuits 30 to 32 constituting the servo drive control units of the axis servo motors receive the movement command amounts of the respective axes from the CPU 11 and output the commands of the respective axes to the servo amplifiers 40 to 42. The servo amplifiers 40 to 42 receive the command and drive the servo motors 50 to 52 of each axis. The servo motors 50 to 52 of each axis have built-in position / speed detectors 60 to 62, and feed back the position / speed feedback signals from the position / speed detectors 60 to 62 to the axis control circuits 30 to 32, and Performs speed feedback control. The drive current is fed back to the axis control circuits 30 to 32 from the current detectors provided in the servo amplifiers 40 to 42, and the servo drive current can be detected. This drive current is also fed back to the CPU 11 via the axis control circuits 30 to 32.
[0012]
The spindle control circuit 70 receives a spindle rotation command and outputs a spindle speed signal to the spindle amplifier 71. The spindle amplifier 71 receives the spindle speed signal and rotates the spindle motor 72 at the commanded rotation speed. The position coder 73 feeds back a feedback pulse to the spindle control circuit 70 in synchronization with the rotation of the spindle motor 72 to perform speed control. The drive current of the spindle motor 72 is also fed back to the spindle control circuit 70 from the spindle amplifier 71, and the CPU 11 can detect the drive current of the spindle motor via the spindle control circuit 70.
[0013]
The configuration of the numerical control device described above is the same as the conventional numerical control device. The difference is that an interpolation data changing means for recalculating and outputting interpolation data is provided, and the interpolation data changing means is provided as a customizing means which can be configured by a user.
FIG. 2 is a flowchart of the interpolation processing according to the present embodiment in which interpolation data changing means (customizing means) for recalculating interpolation data and creating corrected interpolation data is added.
[0014]
The CPU 11 analyzes the command read from the machining program or the like, performs pre-processing as in the related art (steps S1 and S2), and then obtains interpolation data at an interpolation calculation cycle (step S3). Conventionally, the interpolation data is subjected to acceleration / deceleration processing (step S5) and output to each of the axis control circuits 30 to 32 (step S6). However, in the present invention, as shown in FIG. 2, the interpolation data is recalculated to obtain the corrected interpolation data. That is, interpolation data recalculation for correcting the interpolation data according to the spindle load or the servo load is performed (step S4). The recalculated interpolation data is subjected to acceleration / deceleration processing (step S5) and is output to each of the axis control circuits 30 to 32. The acceleration / deceleration processing in step S5 may be performed before step S4.
[0015]
The recalculation processing of the interpolation data by the interpolation data customizing means (interpolation data changing means) is performed in the same cycle as the interpolation cycle. Therefore, the correction of the interpolation data is corrected in an extremely short unit of ms or μs, which is the operation cycle of the interpolation.
[0016]
FIG. 3 is a detailed flowchart of the interpolation data customizing means (interpolation data changing means) based on the spindle load current performed every interpolation cycle.
First, the interpolation data is buffered in the read buffer (steps S40 and S41), and it is determined whether the flag F is set to "1" (step S42). If the flag F is not set to "1" (the initial setting is performed first) Is set to "0"), it is determined whether or not the buffered interpolation data is buffered by an amount equal to or more than a predetermined value (step S43). If the buffered interpolation data does not reach the predetermined value, the processing of the cycle ends.
[0017]
Thereafter, the processing of steps S40 to S43 is executed for each interpolation calculation cycle until the buffer stores buffered interpolation data of a predetermined value or more, and the interpolation data is buffered.
[0018]
When the interpolation data is buffered by a predetermined value or more, the flag F is set to "1" (step S44), the drive current I of the spindle motor is read (step S45), and the interpolation data of the spindle data is fixed so that the spindle load becomes constant. A recalculation is performed (step S46). Recalculation of the interpolation data, a reference current value set in advance when the I _0,
Corrected interpolation data = (original interpolation data) × (I ₀ / I)
Asking. Further, since the original interpolation data is determined by the commanded machining speed, the corrected interpolation data may be obtained based on the speed obtained by multiplying the commanded machining speed by (I ₀ / I). Next, as a result of recalculation of the interpolation data, it is determined whether or not the buffer becomes empty (step S47). If not empty, the recalculated and corrected interpolation data is output to the acceleration / deceleration processing unit (step S47). S49). Then, acceleration / deceleration processing is performed as described above (step S5), and output to the respective axis control circuits 30 to 32 to drive and control the respective axis servomotors 50 to 52 (step S6).
[0019]
The above-described processing is executed for each interpolation calculation cycle, and when there is no more interpolation data sequentially stored in the buffer, and it is detected in step 47 that the buffer is empty, the flag F is set to “0”. Then (step S48), the process proceeds to step 49.
[0020]
Figure 4 shows the original interpolation data and the modified relationship of the interpolation data, the original interpolation data is a fixed value, the driving current I of the spindle motor is less than the reference current value I _0, the acceleration in a possible state, the interpolation data corrected increases, greater than the reference current value I ₀ drive current I of the spindle motor, when in need of deceleration, interpolation data corrected is reduced, decelerated Will be. Thus, always be corrected interpolated data is created so that the drive current I of the spindle motor is equal to the reference current value I _0, so that the load is held constant.
[0021]
In the embodiment described in detail, a load such as a cutting load is detected as a load applied to the spindle by a drive current of the spindle motor. However, the load may be detected as a load related to the feed shaft by the drive current of the servo motors 50 to 52 that drive the feed shaft. In this case, in this embodiment, the drive currents of the three servo motors 50 to 52 having three feed axes of X, Y, and Z are detected. Recalculation of the interpolation data may be performed by the drive current. Alternatively, the drive currents of the three servo motors 50 to 52 may be combined, and the interpolation data may be recalculated based on the combined drive current.
[0022]
Further, in the above-described embodiment, an example in which the corrected interpolation data is obtained so that the cutting load is constant has been described. However, the present invention is such that the once obtained interpolation data itself can be corrected at the interpolation cycle interval. Yes, the customizing means (interpolation data changing means) for correcting the interpolation data can be used to change and control the feed of the control object (machine tool) in real time. Further, the movement locus can be partially changed.
[0023]
【The invention's effect】
Since the interpolation data changing means for changing and correcting the interpolation data is separated from the means for the interpolation itself, it is possible to mount the numerical data control device as a user's own customizing means. In addition, since it is possible to perform a process of directly correcting the interpolation data for each short-time interpolation calculation cycle, it is possible to perform high-precision control without delay with respect to the added speed correction.
[Brief description of the drawings]
FIG. 1 is a main block diagram of an embodiment of the present invention.
FIG. 2 is a flowchart of an interpolation process in the embodiment with addition of a customizing unit for creating modified interpolation data.
FIG. 3 is a flowchart of a recalculation process of interpolation data by a customizing unit in the embodiment.
FIG. 4 is an explanatory diagram illustrating a relationship between interpolation data and recalculated interpolation data.
[Explanation of symbols]
100 Numerical control device 50, 51, 52 Servo motor 60, 61, 62 Position / speed detector 72 Spindle motor 73 Position coder

Claims (4)

A numerical controller that analyzes a movement command for a control axis to create interpolation data for each control axis and sends it to a servo drive control unit. A numerical control device comprising an interpolation data changing means for outputting interpolation data. 2. The numerical control device according to claim 1, wherein the interpolation data changing means calculates the corrected interpolation data based on load data of a servo motor that drives the control axis. 2. The numerical control device according to claim 1, wherein the interpolation data changing means calculates the corrected interpolation data based on load data of a spindle motor that drives a main shaft of the machine tool. 4. The numerical control device according to claim 1, wherein the interpolation data changing unit outputs the corrected interpolation data every interpolation cycle. 5.

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