RU2386519C2 - Device for forecasting and control of accuracy of turning treatment of parts in equipment with numerical program control (npc) - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to machine-tool construction, in particular to the field of forecasting and control of accuracy of part surface turning treatment in equipment with numerical program control. Device includes actuating mechanisms, spindle, back and front mandrels, faceplate, cutter-holding block and cutter. It comprises marker of spindle rotation angle, unit of signal amplification, two optical detectors with digital code at the outlet, detector of position, unit of valves and computer. Computer includes a unit for introduction of disturbing effects, control unit of allowances, unit of part radius calculation, unit of subtraction, unit of reference dimensions recording, unit of precision coefficient introduction, unit of multiplication and summator. Two optical detectors with digital code at the outlet are connected to inlet of part radius calculation unit.

EFFECT: increased geometrical accuracy of part treatment.

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Description

The invention relates to the fields of machine tools, forecasting and subsequent control of the accuracy of machining parts on equipment with numerical control (CNC) and can be applied, including in methods of turning metals by cutting on high-precision equipment.

A device for automatically controlling the accuracy of processing on multi-spindle automatic lathes, comprising sensors for measuring the dimensions of the part and the position of the spindles, a node for adjusting the initial corrective movements of the tool and an organ for correcting its position. The disadvantages of this device include the complexity of the design and the fact that the sensor is designed to measure the size of the workpiece, contact. The disadvantage of contact sensors is the low accuracy of measurements, and over time, with constant contact with the surfaces of the controlled parts, physical and chemical deformation of the surfaces of the probes occurs, which reduces the reliability of the information received [1].

Closest to the invention in technical essence is a control device for precision machining of parts on high-precision CNC equipment, including a signal amplification unit, an actuator and a cutter. The disadvantages of this device - when processing parts are not taken into account distortion of the shape of the part caused by bending under the action of the cutting force, and the variation in the size of the parts when processing a batch of workpieces. Also, the device does not allow to simulate the manufacturing process of parts [2].

An object of the invention is to increase the geometric accuracy of machining a part by predicting the accuracy of the machined surface of the part before machining it on the machine.

The problem is solved in that in a device that includes actuators, a spindle and a tailstock with centers for installing the workpiece in them, a headstock and a faceplate mounted on it, a tool holder and a cutter, a spindle angle indicator mounted on the front headstock is introduced, signal amplification unit, two optical sensors with a digital code at the output, a position sensor on the tool holder, a valve block equipped with a hydraulic pressure supply and connected to a hydraulic master a cylinder with a tool holder and a tool, and a computer having a disturbance input unit, a tolerance control unit, a part radius calculation unit, a subtraction unit, a reference size recording unit, a refinement coefficient input unit, a multiplication unit and an adder, with two optical sensors with a digital code at the output is connected to the input of the part radius calculation unit, and its output is connected to the input of the subtraction unit, to which the outputs of the standard size recording unit and the tolerance control unit are connected, the output of the subtraction unit The unit is connected to the input of the multiplication unit, and its output and outputs of the disturbance introducing unit, the reference size recording unit and the refinement coefficient input unit are connected to the inputs of the adder, the output of which is connected through the amplifier unit to the valve block input, and the output of the position sensor is connected , the output of the valve block is connected to the actuators, and the output of the position sensor is connected to the amplification block.

A device for predicting and controlling the accuracy of turning parts on numerically controlled equipment (CNC) (Fig. 1) consists of a rotation angle indicator for spindle 1, headstock 2, spindle 3, part 4, tailstock 5, tool holder 6, cutter 7 , plates 11, actuators 12, an amplification unit 19, a valve block 20 and a position sensor 21, which is equipped with a tool holder, two optical sensors with a digital output 8 and 9, a computer 10, containing a disturbance input unit 13, control The tolerance block 14, the radius calculation block 15, the subtraction block 16, the unit for recording the reference sizes 17, the block for introducing the refinement coefficient 18, the multiplication block 22, and the adder 23.

The connections in the device for predicting and controlling the accuracy of turning parts on numerically controlled equipment (CNC) are arranged in the following order: the spindle angle indicator 1 is mounted on the headstock 2 of the CNC equipment and connected to its spindle 3. The workpiece 4 is installed in the center spindle 3 and the center of the tailstock 5. On the tool holder 6 is installed a cutter 7 and an optical sensor with a digital code at the output 9, which interacts with the side surface of the plate 11 of the front headstock ki 2. An optical sensor with a digital code at output 8 takes readings from the surface of the workpiece 4. The outputs of two optical sensors with a digital code at output 8 and 9 are connected to the inputs of the radius calculation block 15, the output of which is connected to the input of the subtraction unit 16. Also with the input of the subtraction unit 16 is connected to the outputs of the recording unit of the reference dimensions 17 and the control unit of tolerances 14. The output of the subtraction block 16 is connected to the input of the multiplication unit 22, and its output and the outputs of the disturbance input unit 13, the recording unit of the reference sizes 17 and How to introduce the refinement coefficient 18 are connected to the inputs of the adder 23.

The block of introduction of disturbances 13, the control block of tolerances 14, the block for calculating the radius 15, the subtraction block 16, the recording unit of the reference sizes 17, the block for introducing the refinement coefficient 18, the multiplication block 22, the adder 23 are part of the computer 10, the signal output from computer 10 the output of the adder 23, which is connected through the amplifier block 19 to the input of the valve block 20. To the output of the amplifier block 19 is connected the output of the position sensor 21. The output of the valve block 20 is connected to the actuators 12. The compression block 6 can equip sensor 21, providing an auxiliary control loop that closes through the amplification unit 19.

The device for predicting and controlling the accuracy of turning parts on equipment with numerical control (CNC) works according to two algorithms: processing a reference part and processing a batch of parts.

The control circuit of the device for predicting and controlling the accuracy of turning parts on equipment with numerical control (CNC) for processing the reference part is presented in figure 2. The principle of her work is as follows.

Before starting processing in the block introducing disturbances 13, which is part of the computer 10, the value is written

where P _y is the cutting force; V is the cutting speed; S - feed; t is the depth of cut; J _A - standard stiffness of the headstock; J _B - standard stiffness of the tailstock (values J _A , J _B are taken from the machine passport); x is the distance from the headstock to an arbitrary point on the part; L is the length of the part; D is the diameter of the part; α _t is the temperature coefficient of linear expansion; With _{about the} coefficient characterizing the processing condition; In - a departure of a cutter; F _p is the cross-sectional area of the cutter; δ _in - the tensile strength of the processed material; t _s - time spent on tool retraction, V _S - stock removal speed; t _∂ - time of change of the controlled size, V _∂ - speed of change of the controlled size; t _u is the time of change of the measuring signal, V _u is the rate of change of the measuring signal of the predicted perturbations ε ', determined by the formula (1).

. The dimensions of the workpiece 4 and the size tolerance (determined from the working drawing of the part, ⌀

.

и длиной l. Данные снимаются через промежутки времени t. Таким образом, формируется профиль детали.Then, the gaps are adjusted between the optical sensor with a digital code at the output 9 and the face of the faceplate 11 and the optical sensor with a digital code at the output 8 and the surface of the part 4. During the passage, the readings are taken from two optical sensors with a digital code at the output 8 and 9 along the entire length of the part at set intervals of time t, which are determined using the angle indicator 1. Figure 4 shows an example of processing the surface of the part ⌀

and length l. Data is taken at time intervals t. Thus, a part profile is formed.

The data in digital code is transmitted to computer 10 to the radius calculation unit 15. During processing, the displacement of the spindle assembly 3 is measured using an optical sensor with a digital code at output 9 and the part offset using an optical sensor with a digital code at output 8, at specified intervals time t, determined using the angle indicator 1. The signal about the start of work on the unit 1 comes from the computer 10, and then to the optical sensors with a digital code at the output 8 and 9. From two optical sensors with a digital code at the output 8 and 9 at the set time intervals t, signals (x _1n , x _2n ) are taken, which are sent to the computer 10, where the radius of the part is calculated in real-time in the block for calculating radius 15 using formula (2).

The radius of the part, taking into account the effect of disturbing errors caused by bending under the action of the cutting force as a result of thermal displacement of the axis of the spindle and the part itself at any point along its length, is determined by the formula:

where i is the number of control points taken at time intervals t; D _n - diameter of the workpiece surface; (± x _1n ) - part offset from the set value (the signal is determined using an optical sensor with a digital code at output 8, the sign depends on the direction of the offset); (± x _2n ) is the displacement of the part as a result of deflection and / or thermal deformation of the spindle unit 3 (the signal is determined using an optical sensor with a digital code at output 9, the sign depends on the direction of displacement). The calculated value of the radius R _i is stored in the block for calculating the radius 15.

Then, taking into account the total value of the disturbing effects acting on the part 4 when the cutter 7 passes along its surface in real time, a correction is made in the computer and a signal is generated to eliminate it.

In this case, in real time, in the subtraction unit 16, the obtained part size is compared from the radius calculation block 15 determined by the formula (2) - R _i with the given part sizes R _z recorded in the control tolerance unit 14. If the size does not exceed established tolerance fields, then it is considered a reference, and from the subtraction block 16, the size is written to the recording block of the reference sizes 17. If the size is outside the allowable limit, then a correction signal is generated in the subtraction block 16 - σ = R _З -R _i (Fig. .4), i.e. the difference between the specified size (recording unit of reference sizes 17) and obtained from the calculation unit of radius 15. The next time the part is worked out at the place where the size was outside the tolerance range, the correction signal σ from the recording unit of reference sizes 17 is transmitted through the amplification block 19 and the valve block 20 to actuators 12 and, thus, a correction is made for the value of σ. When all dimensions defined in the radius calculation block 15 do not go beyond the required tolerance field, the part is considered a reference. The radius sizes at the given points are stored in the recording unit reference sizes 17.

Thus, a reference model of the part is formed, in which the radius at any point of the part is determined taking into account the disturbing effects acting on the part and the temperature deformations of the part itself, the cutter and the spindle block of the CNC equipment.

The algorithm of the device for predicting and controlling the accuracy of processing parts for processing a batch of parts is shown in Fig.3.

Before the start of processing, a value ε 'is introduced into the disturbance introducing unit 13. In the unit for introducing the refinement coefficient 18, the value of the refinement coefficient is recorded.

That is, it is necessary to take into account the degree of increase in accuracy, which determines the quantitative characteristic of the spread in the dimensions of the finished part processed on CNC equipment, which is characterized by a refinement coefficient γ. The refinement coefficient γ is calculated by the formula:

where t _x is the depth of cut; With _p - coefficient characterizing the processing condition; S _x - feed; V _x - cutting speed; To _p - correction factor, taking into account specific cutting conditions; J _soup - caliper stiffness; J _PB - stiffness of the headstock; J _zb - stiffness of the tailstock (values of J _soup , J _pb and J _zb are taken from the machine passport); x is the distance from the headstock to an arbitrary point on the part; L is the length of the part; D is the diameter of the part; a, y, n - exponents for elements of the cutting mode.

This value is recorded in the block entering the refinement coefficient 18.

In the multiplication unit 22 is entered the value of the coefficient of influence of the radial displacement of the spindle unit 3, which is determined by acceptance tests of CNC equipment.

In real time, the readings of two optical sensors with a digital code at the output 8 and 9 are continuously monitored, which are summed up in the radius calculation block 15 and the obtained value is compared with the reference value of the recording unit of the reference sizes 17. The comparison operation is carried out by the subtraction unit 16. The error signal from the subtracting unit 16 it enters the adder 23 by means of the multiplication unit 22. Also, the adder 23 receives signals from the disturbance input unit 13 and the coefficient input unit is updated I 18, where the total corrective effect formed by an algebraic summation of signals received from the aforementioned blocks.

The numerical value of the correction signal obtained in the adder 23 is transmitted to the amplification unit 19, where amplification occurs in accordance with a given law. After that, the signal is transmitted to the valve block 20, which is equipped with a hydraulic pressure supply and is connected by a hydraulic line to the cylinders of the organs of the block of the tool head 6 and the cutter 7. As a result of the supply of control voltage, the valve block 20 is proportionally displaced by the solenoids, which leads to a proportional pressure change hydraulic line. Thus, from the valve block 20, the hydraulic flow is directed to the blocks 7 and 6, thereby realizing the required corrective action in real time. The tool holder 6 is equipped with a position sensor 21, which creates feedback to provide an auxiliary control loop by actuators of the CNC equipment.

Thus, the proposed forecasting and accuracy control of turning parts on equipment with numerical control (CNC), which operates according to the two above-mentioned algorithms, will allow in real time to obtain a reference model of the part. If the part does not correspond to the required value, the correcting effect is determined in the adder, which is transmitted to the actuators of the CNC equipment, thereby ensuring high accuracy of the machined surfaces of the part when processing a batch of parts in real time.

Literature

1. RF patent No. 1292985, cl. B23Q 15/00, 1985 (analog).

2. RF patent No. 2288808, cl. B23B 25/06, B23Q 15/12, 2006 (prototype).

Claims (1)

A device for predicting and controlling the accuracy of turning parts on numerically controlled equipment (CNC), including actuators, a spindle and a tailstock with centers for installing the workpiece in them, a headstock and a faceplate mounted on it, a tool holder and a cutter, characterized by that it contains a spindle angle indicator mounted on the headstock, a signal amplification unit, two optical sensors with a digital output code, a position sensor on the tool post unit, a valve unit equipped with a hydraulic pressure supply and connected by a hydraulic line to the cylinders of the tool holder and the cutter, and a computer having a disturbance input unit, a tolerance control unit, a part radius calculation unit, a subtraction unit, a reference size recording unit, a coefficient input unit refinement, a multiplication unit and an adder, while two optical sensors with a digital code at the output are connected to the input of the part radius calculation unit, and its output is connected to the input of the subtraction unit the output of the subtraction unit is connected to the input of the multiplication unit, and its output and the outputs of the disturbance input unit, the reference size recording unit and the refinement coefficient input unit are connected to the inputs of the adder, the output of which connected through an amplifier block to the input of the valve block, the output of the position sensor is connected to the output of the amplifier block, the output of the valve block is connected to actuators, and the sensor output is Nia connected to the amplification unit.

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