KR830002788B1 - How to control the speed schedule - Google Patents

Abstract

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Description

How to control the speed schedule

1 is a circuit block diagram of a peripheral speed constant control apparatus for realizing a constant speed constant control method according to the present invention.

2 to 4 are explanatory views for explaining the processing mode to which the constant speed constant control method of the present invention can be applied.

2 is an explanatory diagram of a machining mode in which a positioning operation by a feeding command exists before cutting.

3 is an explanatory diagram of a machining mode in which a feed command in the main axis direction (Z axis direction), a tool change command, and an X axis direction feed command exist before cutting.

4 is an explanatory diagram of a processing form by a fixed cycle.

5 is a diagram illustrating the relationship between a person and a work piece.

6 is an explanatory diagram showing the relationship between the position of a person according to the present invention and the circumferential speed of a workpiece.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a constant speed constant control method, and more particularly, to a constant speed constant control method in which a main axis is rotated so that the main speed of a workpiece becomes a commanded main speed before a person reaches a cutting time point.

In general, in machining, an optimum cutting speed is selected so as to increase the life of the person and shorten the machining time, and then perform cutting as the cutting speed. The cutting speed is determined according to the material, cutting depth, etc. of the workpiece or person.

In general, in a lathe or the like, generally, a cylindrical workpiece is fixed to the main shaft through a chuck and is always rotated. The cutting is continued by moving in the direction perpendicular to the main axis (X axis direction) to obtain the final shape. In this cutting operation, the cutting speed therefore depends on the circumferential speed of the workpiece. The circumferential speed V of the workpiece is expressed by the following equation when the rotation speed of the spindle is n and the radius of the workpiece is R.

V = 2πRn... … (One)

However, in the cutting process of the lathe, the cutting is carried out while feeding the figures continuously or intermittently in the X-axis direction as described above, so that the diameter of the workpiece changes gradually with the progress of the machining. Even if the processing is initially performed at the optimum cutting speed, the cutting speed changes as the processing proceeds. Therefore, it is common to calculate the main shaft rotational speed from the means of monitoring the position of the person in the X axis direction (distance from the center of the main axis to the person), such as the X value register and the contents of the command main speed and the X value register. Whenever a person moves a predetermined amount in the X-axis direction or outputs a pulse distributed in the X-axis direction, the calculation means installs a negative reversible coefficient to the contents of the X-value register according to the movement direction. Memorizes the current position X in the X-axis direction, and calculates from this current position and the command

n = V / 2? … (2)

Calculation is performed to gradually obtain the main shaft rotational speed n, and is controlled in real time so that the main shaft rotates as the main shaft rotational speed n. In this control, since the current position x of the person under cutting is equal to the radius R of the workpiece at the cutting point, the main axis is always rotated at the command circumferential speed during cutting so that the cutting speed is kept substantially constant.

However, the contents of the X value register are updated in accordance with the movement of the person not only when the person moves in the cutting command but also when the person moves by the feeding command, for example, when the person is positioned at the cutting start point by feeding. The current position x of the person is always stored in the register, and the main axis rotation control is always performed by this current position x. Thus, for example, when the distance in the X-axis direction between the feeding start point and the end point (cutting start point) of the person becomes long and the difference between the main rotational speed at which the main speed of the workpiece at the feeding post point becomes the command speed becomes large, Due to the short determination time and the slow response of the spindle motor, a situation occurs in which the spindle motor does not reach a predetermined number of revolutions even when a person is positioned at the cutting start point. Therefore, in the conventional numerical control apparatus, after the positioning is completed, the dwell command is programmed after the feeding command or turned by external sequence control to prohibit cutting until the rotation speed of the spindle motor reaches the predetermined speed. In this case, a standby sequence was inserted during the sequence. As a result, there is a drawback that the processing time is increased due to the waiting time as well as the programming and the external sequence.

Therefore, the object of the present invention is to eliminate the defects by the conventional method, and to control the rotational speed of the main shaft so that the main speed of the workpiece becomes the commanded main speed at the same time as the start of positioning by the feeding, before the figure reaches the cutting point. It is to provide a method of controlling the constant speed to make programming of dwell command and insertion of standby sequence to facilitate programming, etc., and to shorten machining time by eliminating or reducing waiting time.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a circuit block diagram of a constant speed constant control device for realizing a constant speed constant control method according to the present invention, and FIGS. 2 to 4 are explanatory views for explaining a processing form to which the same constant speed constant control method can be applied. 2 is an explanatory diagram when a positioning operation by rapid command is present before cutting, and FIG. 3 is a rapid command in the main axis direction (Z axis direction), a tool change command, and an X axis direction feeding command before cutting. Explanatory drawing of FIG. 4 is explanatory drawing which showed the processing form by a fixed cycle.

In FIG. 1, the example part DR is an X value register configurable by a preset reversible counter and corresponds to the distance X from the main axis center line CL (Z) to the position of the person TL as shown in FIG. Whenever a distribution pulse Xp for storing the number of pulses to move and moving the person in the X-axis direction is generated from the pulse divider described below, the contents are moved one by one in the positive or negative direction according to the movement direction of the person. Update In Fig. 5, WK is a workpiece, MT is a lathe OPC, and the spindle speed n is expressed by the formula (2) from the command x speed V _O (m / min) and the contents x of the X value register (DR). Is an arithmetic circuit for digital value arithmetic operation, and NOR is a rectification circuit for normalizing the digital value (spindle rotation rate n) outputted from the arithmetic circuit OPC in 12-bit binary number. That is, since the output n of the operation circuit OPC is different from the unit of the command circumferential speed V and the content x of the X value register DR, it cannot be output as a spindle speed command as it is, so it is normalized by the normalization circuit NCR. Output is made with the spindle speed command N. CT is a correspondence label that stores the correspondence between n and N. The main spindle speed command N (= 2000) corresponding to the maximum value of n (2 ¹² -1 = 4095) is stored in the normalization circuit (NOR). The ICP normalizes the operation circuit (OPC) output by proportional calculation from this correspondence, and the ITP performs interpolation operation according to the position command to apply the distribution pulses Xp and Zp to the servo controller (SVC). A pulse divider that moves in the Z-axis direction, TP is a paper tape with numerical control information perforated, COT is information from the paper tape TP and a dispensing end signal DEN from the pulse divider ITP, and not shown. A control circuit which generates and controls various control signals according to signals from an operation panel, etc., and a DOP is an arithmetic circuit which calculates the X coordinate of the next cutting start point in a fixed cycle, etc. IG is a rapid feeding instruction (GOO). Is a gate circuit that prevents the X-axis distribution pulse Xp from being applied to the X-value register DR while the person is moving, and the DAC is a digital-to-analog converter for converting the spindle speed command N into an analog voltage. DM is a motor, TG is a motor-mounted generator that outputs an analog voltage according to the actual speed (speed) of the main shaft, and MCC has a zero (0) deviation between the command speed and the actual speed. Is a sub control circuit that outputs a voltage proportional to the deviation.

The constant speed control will be described below.

First, the person TL is positioned at point B from the point A of FIG. The control circuit COT generates a gate control signal GS immediately after the feed command GOO is read from the paper tape TP, closes the gate circuit IG, and simultaneously reads the B after the feed command GOO. The X coordinate value of the point is preset in the X value register DR. If the position command is an incremental command, the control circuit COT calculates the coordinate value of the point B X as the present position of the person stored in the memory not shown in the operation circuit DOP and the increment value thereof, and converts the result of the calculation into an X value. When the register DR is preset, the operation circuit OPC calculates the spindle speed n from the equation (2) according to the contents of the command main speed V _O and the X value register DR input from the control circuit COT. Calculate The spindle speed n is normalized to the spindle rotation command N in the normalization circuit NOR and applied to the servo control circuit MCC through the DA converter DAC. The servo control circuit (MCC) starts the servo control so that the actual spindle speed coincides with the spindle speed command N when this spindle rotation command N is input, and the position command X, Z in parallel with the spindle speed control. By the pulse divider ITP, pulses Xp and Zp are distributed, and these distribution pulses Xp: Zp are input to the servo control system SVC and shift the person to point B at the feeding speed. In other words, at the same time as the positioning of the person is started by feeding, the constant speed control operation is started by the workpiece diameter at point B. When the positioning is completed, the main speed of the workpiece coincides with the command circumferential speed V _O or the command circumferential speed. It is close to V _O. 6 is an explanatory diagram showing the relationship between the position of the person and the main speed, showing the position of the person on the horizontal axis and the actual main speed on the vertical axis, in which A and B respectively indicate the starting point of feeding and the end point of feeding (cutting start point). This corresponds to point A and point B in FIG. 2, where V _A is the main speed at A and V _O is the command main speed.

When the response of the servomotor of the main axis motor is fast or when the distance between the A and B points is long, the command main speed V _O is reached before the person reaches the B point as indicated by the dotted line in the drawing. When the response of the surgeometer is slow or when the distance between A and B is short, the main speed of the workpiece does not reach the command circumferential speed V _O as indicated by the dashed-dotted line in the figure. Do not. However, even in this case, the circumferential speed of the workpiece is almost close to the command circumferential speed V _O.

However, when the positioning by the rapid feeding command is completed, the content of the X value register DR is the same as the X coordinate of the person's current position at this completion point, and then the workpiece diameter is stored. When the positioning is completed, when the distribution completion signal DEN is input from the pulse distributor ITP to the control circuit COT, the control circuit COT drives a tape reader (not shown) to read the next block information, that is, cutting command. And input the position information X and Z to the pulse divider (ITP). At this point, if the spindle speed command N is equal to the actual spindle speed (i.e., the main speed of the workpiece coincides with the command speed) (see dotted line in Fig. 6), the servo controller (MCC) The speed coincidence signal VE is output, and the pulse divider ITP executes a pulse distributing operation for cutting immediately, and transmits the distributing pulses Xp and Zp to a servo for driving a person to start cutting. However, if the spindle speed command N does not coincide with the actual spindle speed, that is, if the circumferential speed of the workpiece does not match the command speed (see dashed line in Fig. 6), the speed coincidence signal VE does not occur. Therefore, in the pulse divider ITP, pulse distribution calculation based on the cutting command is prohibited until the speed coincidence signal VE occurs. However, if the main speed of the workpiece is approximately equal to the command main speed V _O , the speed coincidence signal VE is applied to the pulse distributor ITP and is also input to the control circuit COT. The control circuit COT opens the gate circuit IG immediately by setting the gate control signal GS "0" by the input of the speed coincidence signal VE. As a result, the distribution pulse Xp can be applied to the X-value register DR through the gate circuit IG, and then performs the same operation as before until the rapid feeding command GOO occurs. That is, when feeding is yiryeong allocated to the X-axis by (such as cutting command) pulses Xp other than the command generating X value register (DR) is always calculated, and stores the radius of the workpiece, by the radius of the reference velocity V _O circuit ( OPC) and the like, and the spindle speed command N is calculated and pushed. The servo control circuit MCC controls the servo so that the actual spindle speed matches the spindle speed command N so that the main speed of the workpiece is equal to the command speed. Next, the figure TL moves rapidly from point A to point B, as shown in FIG. The case will be described. In such a processing mode, the X coordinate value of C point can be set in the X value register DR by the feeding command at point B, similarly to the constant speed control method in the processing mode of FIG. If the response of the servo is not fast or the distance between point B and C is short, as indicated by the dashed-dotted line in FIG. _O does not match. Therefore, if the X value at point C, which is the cutting start point, that is, the set of the workpiece diameter R to the X value register DR is executed at the same time as the feeding command of A to A or before the feeding command of A, In all cases, upon completion of positioning of the person at point C, the circumferential speed of the workpiece coincides with the commanded circumferential speed V _O. This is because the rapid command GCO Z… at A point. GCO Z… R… Just change the ^* . Where GCO is the rapid feed command, Z… Is the Z-axis position command, R... Is the radius set command, and ^* is the block end.

As the circuit operation, R... At this point in time, the point of setting the radius value (value after Q) to the X-value register DR through the line l by the second circuit COT is different. Same as As described above, the method of designating R by the program is not limited to the case of FIG. 3, and the radius value can be set in the X-value register DR at any point in time by inserting an instruction to set R in place.

4 is a description of the case where the present invention is applied to a so-called fixed cycle in which the cutting start point is changed by a predetermined amount C and the cutting operation and the positioning operation to the cutting start point after completion of cutting are repeated to obtain a desired final shape. In the fixed cycle, the cutting cycle is performed from the cutting start point, and after the end of the cutting, the axial feeding is carried out from the A point to the B point, and then the feeding starts in the X axis direction to the cutting start C 'point, and the C' point is completed after the feeding is completed. It is a machining form which cuts again, and changes the depth of cut by d afterwards, and repeats the same process, and obtains a final shape.

By the way, in this processing form, this invention X-coordinate value of the next cutting start point (C 'point) to the X-value register DR by the Z-axis feed feeding instruction | command at A point after cutting is completed, ie, the workpiece | work radius Set the main speed of the workpiece as the command circumferential speed V _O between the figures and the transition from point A to point C '. That is, when the fixed cycle mode is commanded from the tape and the feed command GOO is commanded, the main control circuit COT calculates the coordinate value X _O ', that is, the radius value of the workpiece at the cutting point, and the X value register ( DR). In the fixed cycle, the cutting amount d and the X coordinate X _O of the first cutting instruction point C are stored in a memory (not shown) of the main control circuit COT in advance. Therefore, when the GCO is commanded, the DOP

X _O -d → X ' _O

If you perform the operation of, X ' _O becomes the X coordinate of C' point.

Thereafter, the figure reaches the point C 'by a circuit operation such as the constant speed constant control in the machining mode of FIG. 2, and the circumferential speed of the workpiece is at or near the commanded speed at this point of arrival. At one point, a pulse divider operation for cutting is performed on the pulse divider (ITP).

As described above, the present invention prohibits the updating of the contents of the X value register at the same time as the feeding command, and at the same time sets the radius value of the workpiece at the starting point of cutting at the X value register prior to or at the same time as the feeding command. Therefore, at the time of completion of feeding, that is, when the figure reaches the cutting start point, the main speed of the workpiece can be matched to or almost coincides with the command rate, so the waiting time until the workpiece main speed becomes equal to the command speed is reduced to zero. As a result, the machining speed can be greatly improved, and the feed command can automatically preset the radius value of the cutting starting point in the X value register, so there is no need to program the dwell, simplifying programming or external Sequential control can be simplified.

In the above manual, the X-coordinate value of the starting point of cutting, i.e., the radius value of the workpiece, has been described. However, the diameter value or the corresponding value may be stored. In the above description, an example in which a hardware circuit is formed for each function has been described. However, the control method may be softly implemented using a microprocessor or the like.

In addition, although the actual spindle speed is obtained by installing a generator for the rotation system, the lathe is usually equipped with a position coder. In this case, the rotation speed of the spindle can be obtained by the frequency of the position pulse.

Claims (1)

Memory means for updating the stored contents as the person moves, and storing the stored contents as the diameter of the workpiece, and arithmetic means for gradually calculating the number of revolutions of the main shaft rotating the workpiece based on the commanded main speed and the diameter of the workpiece. In the main speed constant control method for rotating the main axis and the constant speed of the workpiece in accordance with the calculated number of revolutions of the spindle, the update of the stored contents is prohibited while the person is moved by the feeding command. The memory means stores in advance the numerical value according to the distance between the position at which the person starts moving and the center of the main axis at a speed other than the speed, and calculates the number of revolutions of the main axis based on the value and the commanded main speed. And controlling the spindle by the spindle speed before reaching.

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