JPH0248702A - Numerical controller - Google Patents

Abstract

PURPOSE:To attain working having high concentric accuracy by using a specified control shaft as the driving shaft of a rotary table and executing rotary- operation of machining, optional positioning and an outline interpolation operation with the other control shaft by means of a part program. CONSTITUTION:All the control shafts are composed of digital software servo control circuits, and a constant required for servo control has a command which can optionally be altered on the part program which a user generates. The command can directly alter the constant which cuts the position field back loop of the servo control circuit and the constant for normalizing the quantity of rotation in a servo motor. The specified shaft of the control shafts is mechanically connected to the rotary table and the rotary operation and positioning for machining, and the outline interpolation operation with the control shaft are switched by the part program so as to attain operation. Thus, working having high concentric accuracy is executed and a set-up time at the time of switching a kind is shortened, whereby working information is easy to be accumulated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a numerical control device for controlling a machine tool equipped with a rotary table, and in particular, it is used for turning a workpiece fixed to a rotary table and for arbitrary positioning. The present invention also relates to a numerical control device capable of performing two operations using a single servo motor: drilling and milling by contour interpolation with other control axes.

[Prior Art] In the field of machine tools, two operations are often required: turning a workpiece fixed on a rotary table, and drilling and milling by arbitrary positioning and contour interpolation with other control axes. It may happen.

Conventionally, these processes have been carried out using two machine tools: turning with a numerically controlled illumination lathe and a numerically controlled milling machine, and milling with a machining center, or a composite numerically controlled lathe that can perform turning and milling. Or, it was done using a special machine.

[Problems to be Solved] The conventional numerical control device described above has the following problems.

■ In the former method, which uses two machine tools, firstly, the workpiece is machined by two machines, so it is necessary to attach and detach the workpiece, making it difficult to obtain high concentric accuracy; Each time the type of product changes, setup time is required, and thirdly, the use of two machines incurs various expenses such as high capital investment and an increase in the floor space for installing the machines.

■In the method of using a multifunction machine, there is a machine called a turning center that is equipped with a rotary tool on a numerically controlled lathe and is capable of milling. This is achieved by using two motors and performing mechanical switching. For this reason,
This requires a complicated switching structure and an additional drive motor, which inevitably increases the system price.

■The latter method, which uses a dedicated machine, generally does not use a numerical control device, and is achieved mainly by using mechanical cams and stoppers, so the first priority is to obtain high machining accuracy. Second, it takes time to set up each time the type of workpiece changes, and third, it is impossible to accumulate information for processing.

The present invention was made in view of the above problems, and is capable of performing machining with high concentric accuracy, shortens setup time when changing types, facilitates the accumulation of machining information, and is a numerically controlled machine tool. The purpose of the present invention is to provide a numerical control device that can achieve smaller size and lower cost.

[Means for Solving Problems] In order to achieve the above object, the numerical control device of the present invention is a numerical control device for a machine tool having a rotary table controlled by a digital software servo control circuit. A digital software servo control constant changing means for arbitrarily changing the constant, and a position feedback loop in the servo control of the control axis that drives the rotary table are cut, the rotary table is rotated at a constant desired rotation speed, and the other control axes are A turning processing mode switching means for turning a workpiece fixed on a rotary table by giving commands to the rotary table, and a position feedback loop in servo control of the control axis that drives the rotary table to perform arbitrary positioning and other operations. The configuration includes a milling machine mode switching means that performs drilling and milling by giving a contour interpolation command with the control axis.

In other words, in the numerical control device of the present invention, all of the control axes are configured with digital software servo control circuits, and the constants necessary for this servo control are determined using a display device and a keyboard for servo adjustment. In addition to being equipped with an input means, it also has commands that can be changed arbitrarily on the part program created by the user.

This command can directly change the constant that disconnects the position feedback loop of the servo control circuit and the constant that normalizes the rotation speed of the servo motor, and is a feature of the numerically controlled lathe. A specific axis of the control axes is mechanically connected to the rotary table, and the rotation operation for turning, arbitrary positioning, and contour interpolation operation with other control axes can be switched and operated using a part program.

[Example] Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 1 is a block diagram of a digital software servo control circuit of a numerical control device according to an embodiment of the present invention.

In the figure, l represents the entire software processing of the digital software servo control circuit.

First, 2 receives the command data S1 from the interpolation calculator provided in the numerical control device, calculates the formula (1) with the command coefficient parameter PI set in advance, and obtains the calculated data S2. This is the command coefficient calculation process to be output.

S15 are mutually 9 pulses generated from a rotary incremental pulse generator 11 directly connected to the servo motor 10.
This position feedback data is obtained by counting up the two-phase pulse output S14 with a phase difference of 0 degrees using 13 up/down counter circuits, and periodically sampling and reading out the contents of the counter.

3 is a position feedback coefficient calculation process in which the position feedback data s15 is received, the equation (2) is calculated between it and a preset position feedback coefficient parameter P2, and calculated data S3 is output.

S4 indicates positional deviation data, which is calculated using equation (3) in process Nl.

52-53=S4... (3) 4 indicates position feedback loop processing, has a position deviation register, stores value ΣS4 obtained by adding position deviation data s4 every cycle in the position deviation register, and
Preset position loop gain parameter P3
Equation (4) is calculated using the value ΣS4 of the position deviation register and the speed command S5 is calculated.

Σ 54 This shows the speed feedback data that is read out by counting up the counter and periodically sampling the contents of the counter.

5 receives the speed feedback data S16 and sets the speed feedback coefficient parameter P set in advance.
4 and calculate the equation (5). This is speed feedback data coefficient calculation processing for calculating S6.

S7 indicates speed deviation data, which is calculated using equation (6) in process N2.

55-56=S7... (6) 6 indicates speed feedback loop processing, in which calculation is performed to convert speed deviation data S7 into current command s8. Sl indicates an analog voltage detected in the drive unit 9 from the load current of the servo motor 1o, and SIO, which is converted into digital data in S9 by the A/D converter 12, indicates current deviation data, and in processing N3 ( 7) Calculate using the formula.

58-59=S10 (7) 7 indicates current feedback loop processing, which performs calculation to convert current deviation data S10 into current output command Sll. The current output command Sll becomes a command to the next pulse width conversion process 8. 8 is a pulse width conversion process for converting the current output command Sll into a switching command S12 for the power control circuit built in the drive section unit 9.

Reference numeral 9 indicates a drive unit that amplifies the switching command and supplies power to the servo motor 10, and S13 indicates a power supply line to the servo motor 10. Servo motor 1
0 is used as a drive source for the machine, and 11 indicates a rotary incremental pulse generator, which is directly connected to the servo motor 10 and usually plays the role of a position detector and a speed detector.

The numerical control device equipped with the digital software servo control circuit configured as described above uses the part program example shown in FIG. 2 to change each parameter of PI, P2, P3, and P4 of the completely digital software servo control circuit described above. It is possible to do so.

Next, the part program of this embodiment will be explained based on FIG.

The program (2) is a command to set the speed feedback coefficient parameter P4 to r3125J.

Since the processing speed of software servo control is 3125H2, the minimum unit of speed feedback pulse is 1
It is normalized to be pulses/second.

The program (2) is a command to set the position feedback coefficient parameter P2 to "O", and disconnects the position feedback loop of software servo control. When the value of P2 is set to 0, 52=54...(8) is obtained from equations (2) and (3), indicating that the position feedback loop is disabled.

The programs ① and ② are commands for convenience in terms of the rotation command format of the servo motor.

Equation (9) shows the relationship between the rotation speed of the servo motor and the command.

Servo motor rotation speed (rpm) = (Number of command pulses (pulses)
ev)) ...(9) The number of command pulses in equation (9) is the value ΣS4 of the position deviation register in the position feedback loop process in Fig. 1, and the command minimum unit is the position relative to lrpm. Set the value of the deviation register to 1.

A Vertical loop gain parameter P3 Pa... (10) In this embodiment, a numerical example is given when a rotary incremental pulse generator that can generate 10,000 speed detection pulses per rotation of the motor is applied.

In addition, the program (2) is used for convenience by setting the movement command l pulse of the control axis in units of 1 rpm of the rotation speed of the servo motor. That is, in equation (1), P 1 =
Substituting 16384 results in 51=S2 (11).

■The program moves the C-axis servo motor to 250 Orp.
This is a command to rotate by m. Traditionally, this directive
This means a linear interpolation operation with a feed rate of 300 mm/min and a movement amount of 2500 pulses, but in this example, the position feedback loop is disconnected, so
The C-axis servo motor rotates continuously at 250 rpm, which is one of the intentions of the present invention.

The program (2) is a series of programs for other control axes while the C-axis is turning, and is usually a program for performing turning processing.

The program (2) is a command to stop the rotation of the C-axis servo motor. Similar to the program in ■, conventionally,
This command means a linear interpolation operation with a feed rate of 300 mm/rnin and a movement amount up to the C-axis coordinate im O, but in this example, the C-axis will be stopped.
This is one of the intentions of the present invention.

The program ① is a command to stop the preprocessing buffer, and is used to adjust the timing of the servo parameter change programs ① to ＠. ■ ~ @ program is Pl, P2 to enable the position feedback loop.
, P3, and P4 are returned to their original values.

The program (2) is a program in which the C-axis is used as a normal control axis and includes commands such as positioning and contour interpolation, and performs a series of drilling and milling operations.

[Effects of the Invention] As explained above, the present invention configures its control axis with a completely digital software servo control circuit,
Machining with high concentric accuracy is achieved by using a specific control axis as the drive axis of the rotary table and performing rotational movement and arbitrary positioning for turning and contour interpolation with other control axes using a part program. is possible,
The present invention has the effect of providing a numerical control device that can shorten setup time when changing product types, facilitate the accumulation of machining information, and reduce the size and cost of numerically controlled machine tools.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a digital software servo control circuit of a numerical control device according to an embodiment of the present invention, and FIG. 2 is a diagram showing an example of a part program used in the numerical control device of FIG. l: Overall software processing of digital software servo control circuit lO: Servo motor

Claims (1)

[Claims] In a numerical control device for a machine tool that has a rotary table controlled by a digital software servo control circuit,
A digital software servo control constant changing means for arbitrarily changing the constants required for digital software servo control, and a position feedback loop in the servo control of the control axis that drives the rotary table is cut to keep the rotary table at a desired rotation speed. A turning mode switching means for rotating and giving commands to other control axes to turn the workpiece fixed on the rotary table, and a position feedback loop in the servo control of the control axis that drives the rotary table. 1. A numerical control device comprising a milling machine mode switching means for performing drilling and milling by giving commands for arbitrary positioning and contour interpolation with other control axes.