CN202726639U - Cutting condition monitoring system based on computerized numerical control (CNC) milling machine spindle servo motor current signal - Google Patents

Cutting condition monitoring system based on computerized numerical control (CNC) milling machine spindle servo motor current signal Download PDF

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Publication number
CN202726639U
CN202726639U CN 201220400867 CN201220400867U CN202726639U CN 202726639 U CN202726639 U CN 202726639U CN 201220400867 CN201220400867 CN 201220400867 CN 201220400867 U CN201220400867 U CN 201220400867U CN 202726639 U CN202726639 U CN 202726639U
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CN
China
Prior art keywords
cutting
signal
current
milling machine
servo motor
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CN 201220400867
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Chinese (zh)
Inventor
仇健
刘春时
林剑峰
马晓波
曹文智
刘启伟
任宝钢
范世平
杨顼
谭延林
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沈阳机床(集团)设计研究院有限公司
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Priority to CN 201220400867 priority Critical patent/CN202726639U/en
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Abstract

The utility model provides a cutting condition monitoring system based on a computerized numerical control (CNC) milling machine spindle servo motor current signal and belongs to the field of the CNC milling machine cutting condition monitoring. The cutting condition monitoring system based on the CNC milling machine spindle servo motor current signal comprises a Hall current sensor, a lowpass filtering (LPF) adjusting device, a data acquisition (DAQ) card, an alternating current and direct current conversion module, a computer and the like. The cutting condition monitoring system is based on a mapping relation between a spindle current and a cutting force and reflects the variation of the machine cutting condition by utilizing the spindle servo motor current signal. Wavelet decomposition is performed on the servo drive current signal collected by the Hall current sensor. Signal features generated in the signal due to the cutting is collected and then reconstituted. The reconstituted signal is used as an input variable of cutting force-current model after the alternating current and direct current conversion. The input variable is calculated by the system software part to achieve the purpose of reflecting the cutting machining condition of the machine at real time. The cutting condition monitoring system based on the CNC milling machine spindle servo motor current signal achieves the purpose of using the low cost Hall current sensor to indirectly replace a high cost force sensor by means of the cutting force in the process of CNC milling spindle servo motor current monitoring.

Description

Cutting state monitoring system based on CNC milling machine spindle servo electric machine current signal
Technical field
The utility model relates to Cutting Parameters in NC Milling Machine status monitoring field, is specially a kind of system based on CNC milling machine main axle servo current monitoring cutting state.
Background technology
Milling Process is a kind of interrupted cut method, and different blades participate in cutting can produce impact to workpiece, forms cutting force.Cutting force is the important physical amount that characterizes cutting state, cutting force increases sharply and has reflected that the lathe operation conditions is unstable, supervenes vibration, cutter-workpiece contact zone temperature rising, causes the part crudy to worsen, serious meeting causes cutter to gall and decreases, even destroys machine tool accuracy.In order to reduce the loss, often to reduce cutting parameter and guarantee to cut stable, continuous and good part quality.Can reflect in real time machining state by gathering Cutting Force Signal, reach the purpose of cutting state monitoring, give full play to the cutting usefulness of lathe.But because cutting force sensor processing is expensive, and Milling Process is that the cutter rotation is cut, and therefore, the power sensor that volume is larger can't be installed on main shaft or the cutter, more can't be built in part to be processed.
Summary of the invention
The technical problems to be solved in the utility model provides a kind of measuring system of brand-new monitoring numerical control machine tool cutting state, CNC milling machine main axle servo electric current and load variations when this system can not only monitor cutting, and can indirectly measure and monitor by the model parameter conversion situation of change of the machine tooling status signals such as cutting force, the cutting moment of torque, and then reflect the cutting situation of lathe.
The purpose of this utility model is achieved through the following technical solutions: the cutting state monitoring system based on CNC milling machine spindle servo electric machine current signal is characterized in that: it comprises Hall current sensor, LPF regulating instrument, data collecting card, AC-DC conversion module, computer; Hall current sensor is installed in respectively on the three phase drive cables of milling machine spindle driving servomotor, is used for gathering the three-phase alternating current signal of telecommunication of main shaft drives servomotor; Carry out signal condition through the filtering of LPF regulating instrument; Signal after the conditioning is input to data collecting card and is transferred on the computer through the AC-DC conversion module.
Described computer is connected with digital control system, and digital control system is connected with the feed shaft servomotor.
Operation principle of the present utility model:
Carry out time domain, frequency-domain analysis by Cutting Parameters in NC Milling Machine power that cutting experiment is measured and spindle servo electric machine current signal and through the DC characteristics amount that AC-DC conversion obtains, the three-phase current of finding spindle servo electric machine changes and the vibration frequency existence frequency component consistent with cutting force in amplitude, can be used for characterizing cutting load, the reflection cutting state.
Hall current sensor is installed in respectively on U, V, the W three-phase alternating current cable of machine tool chief axis servomotor, Hall current sensor is powered by the 15-24V D.C. regulated power supply, its holding wire is drawn and is connected on the LPF regulating instrument, through signal condition further with RS232 interface or USB interface form through the data collecting card real time record to computer.
When ac current signal was recorded in acquisition system, the three-phase current signal that obtains needed be converted to the Equivalent DC signal of telecommunication through root mean square (RMS value) calculating as AC-DC, so that as the characteristic quantity of main shaft drives servomotor electric current.
The DC characteristics amount that obtains through AC-DC conversion also includes other interference separation when comprising the cutting force frequency separation, signal adopts the wavelet analysis means to carry out signal recognition or reconstruct before importing computation model, extracts thus the component of signal relevant with cutting force in the main shaft drives servomotor electric current rms signal.
Set up the mapping relations of cutting force and electric current spare, and form forecast model, and then indirectly reflect the cutting state of lathe, realize substituting with low-cost Hall current sensor the method for power sensor.The cutting state monitoring system of finally utilizing the utility model to form realizes the monitoring of machine tooling state.
The beneficial effect that the utility model is created: the utility model has overcome the limitation of traditional cutting force measurement and modeling method, mechanism from servo drive system, by in the CNC milling machine spindle servo electric machine current signal with the relevant signal extraction of cutting, identification, reconstruct and modeling, for the operation conditions of lathe in carrying out metal cutting process provides safeguard, lathe is after the cutting fault occurs, effectively in the monitoring and prediction cutting process because of machined parameters arrange improper, misoperation, the cutting-impact that cutting-vibration or emergency situations cause is effectively avoided scrapping because cutting state worsens the part that causes, the cutter loss, the unnecessary losses such as lathe life-span reduction.In addition, based on the current signal monitoring force signal of main axle servo driver element, indirectly set up the forecast model of real-time cutting force signal, the cutting force measurement in the time of can being further used as without dynamometer equipment and intelligent milling monitoring system.
Description of drawings
Fig. 1 is the schematic diagram that the utility model carries out cutting force and the checking of spindle servo electric machine current relationship.
Fig. 2 is drive system AC-DC conversion schematic diagram.
Fig. 3 is that the utility model utilizes current sensor to replace the schematic diagram of power Sensor monitoring cutting state.
Fig. 4 is drive system structure and the cutting load bang path figure of mechanical type main shaft.
Fig. 5 realizes the systematic schematic diagram of cutting state monitoring and control for adding digital control system.
Among the figure, the 1st, CNC milling machine main shaft, the 2nd, dish milling cutter, the 3rd, workpiece to be machined, the 4th, milling machine table, the 5th, milling machine spindle drives servomotor, the 6th, Hall current sensor, the 7th, LPF regulating instrument, the 8th, data collecting card, the 9th, AC-DC conversion module, the 10th, computer, the 11st, forecast model, the 12nd, software systems, the 13rd, Cutting Force Signal; The 14th, dynamometer; The 15th, digital control system, the 16th, feed shaft servomotor; The 17th, I/O interface board; The 18th, charge amplifier, 19 is axis system, and 20 is transmission system, and 21 is main shaft drives servomotor and simplification circuit thereof.
The specific embodiment
Before design and building this monitoring system, carry out necessary cutting force-electric current simultaneous test, with the constituent of overall understanding cutting force and current signal and connect each other.Pilot system as shown in Figure 1, the data monitoring object of this pilot system is the Cutting Process system that is comprised of CNC milling machine main shaft 1, dish milling cutter 2 and workpiece 3.Pilot system comprises: piezo crystal dynamometer 14, charge amplifier 18, Hall current sensor 6 and LPF regulating instrument 7, I/O interface board 17 etc.The cutting force test uses dynamometer 14 to be installed on the workpiece 3, and current detecting is used Hall current sensor 6, and three-phase current needs three Hall current sensors 6, and the output signal unification is voltage signal, can make things convenient for follow-up signal to process.The main shaft drives servomotor power of numerical control machining center does not generally wait at 100-300, and Hall current sensor 6 type selectings are generally selected according to the rated power of main shaft drives servomotor power, should guarantee that range guarantees certainty of measurement again.The charge amplifier 18 that Hall current sensor 6 is connected with dynamometer through LPF regulating instrument 7 is connected with the input terminal of I/O interface board 17, and the lead-out terminal of I/O interface board 17 links to each other with data collecting card 8, realizes the synchronous acquisition of current signal and Cutting Force Signal.
Contact very complicated between cutting force and servomotor electric current, and utilize the servomotor electric current under the Hall current sensor collection to be alternating current, formula (1), the relational model of setting up cutting force and electric current need to convert alternating current to the root mean square RMS value that DC current is spindle servo electric machine, formula (2), this signal deduct the initial point drift and namely can be used as the current characteristic signal that characterizes cutting force.AC-DC transfer principle such as Fig. 2, Hall current sensor is installed in respectively on U, V, the W three-phase alternating current cable of milling machine spindle servomotor, because current signal comprises a lot of noise contributions, the Hall element that is connected with U, V, W three-dimensional electric current output signal to LPF regulating instrument 7, signal is nursed one's health through filtering, filtered out the inapparent noisy frequency component of amplitude.Further be transferred to data collecting card 8 with RS232 interface or USB interface form through signal condition, again through AC-DC modular converter 9, output obtains dc current signal.It is worth mentioning that, dc current signal through AC-DC conversion comprises a lot of frequency contents at frequency domain, wherein comprises with main shaft to rotate relevant rotational frequency, participate in cutter tooth frequency and main shaft self the servo current frequency equifrequent composition of cutting with cutter.Wherein the frequency component relevant with cutting mainly is the cutter tooth frequency.Use wavelet analysis signal is extracted and reconstruct, just can obtain the signal component relevant with cutting force.
??????????????????????(1)
??????????????????????????(2)
By above-mentioned verification experimental verification method feasible, build monitoring system such as Fig. 3, the Cutting Process system that the monitoring target of this monitoring system is comprised of CNC milling machine main shaft 1, dish milling cutter 2, workpiece 3, workbench 4; This monitoring system is made of Hall current sensor 6, LPF regulating instrument 7, data collecting card 8, AC-DC conversion module 9, computer 10; Hall current sensor 6 is installed in respectively on the three phase drive cables of milling machine spindle driving servomotor 5, is used for gathering the three-phase alternating current signal of telecommunication of main shaft drives servomotor 5; Carry out signal condition through 7 filtering of LPF regulating instrument; Signal after the conditioning is input to data collecting card 8, is transferred on the computer 10 through AC-DC conversion module 9 again.Computer 10 built-in forecast model 11, software systems 12 according to cutting force and the foundation of electric current mapping relations can be exported Cutting Force Signal 13.
Based on the cutting force Mathematical Modeling of rotating speed and electric current such as formula suc as formula (3).The drive system structure of mechanical type main shaft and cutting load bang path such as Fig. 4 are comprised of axis system 19, transmission system 20 and main shaft drives servomotor and simplification circuit 21 thereof.The CNC milling machine main axis transmission system is considered to an integral body, and whole inertia comprises that main shaft load inertia, rotational inertia of transmission system and the servomotor rotary inertia by axis system forms.The effects such as the whole cutting force that is mainly changed, electromagnetic force, frictional force (comprising main shaft bearing frictional force and motor and transmission system frictional force) and cutting moment.In addition, mechanical main shaft also need be understood each stage gear ratio of main shaft, and revolving structure quality at different levels are in order to calculate input quantity rotary inertia in the formula.If the electric main shaft of main shaft then directly extracts the servomotor signal and gets final product, need not to consider each stage gear ratio, rotary inertia and rotor quality etc.
Utilize formula (3) equation can set up the relational model of cutting force and main axle servo electric current.
????????(3)
Wherein, T c Main shaft cutting moment, T c = F t ' r, rBe tool radius, F t Be the suffered tangential force of cutter, I s For spindle servo electric machine rotates armature supply, K s Be the motor constant of main shaft drives servomotor, ωBe main shaft drives servomotor angular speed, J s For being transformed into the inertia on the motor shaft, T Fs Be axis system total frictional force square, B s Viscous damping coefficient for motor.
Further computer 10 can be linked to each other with digital control system 15, digital control system 15 is connected with feed shaft servomotor 16, when realizing drilling monitoring, realize the change of cutting data in the processing by changing NC instruction control feed servo system, final monitoring and the control that realizes digital control processing is such as Fig. 5.

Claims (2)

1. based on the cutting state monitoring system of CNC milling machine spindle servo electric machine current signal, it is characterized in that: it comprises Hall current sensor (6), LPF regulating instrument (7), data collecting card (8), AC-DC conversion module (9), computer (10); Hall current sensor (6) is installed in respectively on the three phase drive cables of milling machine spindle driving servomotor (5), is used for gathering the three-phase alternating current signal of telecommunication of main shaft drives servomotor (5); Carry out signal condition through LPF regulating instrument (7) filtering; Signal after the conditioning is input to data collecting card (8) and is transferred on the computer (10) through AC-DC conversion module (9).
2. the cutting state monitoring system based on CNC milling machine spindle servo electric machine current signal according to claim 1, described computer (10) is connected with digital control system (15), and digital control system (15) is connected with feed shaft servomotor (16).
CN 201220400867 2012-08-14 2012-08-14 Cutting condition monitoring system based on computerized numerical control (CNC) milling machine spindle servo motor current signal CN202726639U (en)

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Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103247219A (en) * 2013-05-10 2013-08-14 江南大学 Comprehensive experimental device for cutting jet supporting
CN105033760A (en) * 2015-08-18 2015-11-11 深圳市创世纪机械有限公司 Pre-warning system of numerical control machine tool
CN105312965A (en) * 2015-12-08 2016-02-10 华中科技大学 Breakage monitoring method for milling tool
CN105500111A (en) * 2015-12-25 2016-04-20 鼎奇(天津)主轴科技有限公司 No-load friction moment test method and control system of machine tool main shaft
WO2016192308A1 (en) * 2015-05-29 2016-12-08 东莞思谷数字技术有限公司 Method for balancing external force load in machine tool spindle motor
CN106475855A (en) * 2016-11-22 2017-03-08 无锡职业技术学院 A kind of online detection instrument of main shaft of numerical control machine tool load and detection method
CN107077122A (en) * 2014-10-29 2017-08-18 株式会社牧野铣床制作所 The control method of lathe and the control device of lathe
CN107450481A (en) * 2017-08-31 2017-12-08 福建工程学院 A kind of numerical control machine tool cutting velocity optimization method
CN107765647A (en) * 2017-09-20 2018-03-06 哈尔滨工业大学深圳研究生院 The intelligent speed planing method of processing is repeated based on high-volume single-piece
CN107838747A (en) * 2017-11-16 2018-03-27 山东大学 Cutting tool state intelligent control method based on industrial robot milling process
CN108620950A (en) * 2018-05-08 2018-10-09 华中科技大学无锡研究院 A kind of turning cutting tool drilling monitoring method and system
CN109822382A (en) * 2017-11-23 2019-05-31 上海铼钠克数控科技股份有限公司 The anti-collision machine system and control method of numerically-controlled machine tool

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103247219A (en) * 2013-05-10 2013-08-14 江南大学 Comprehensive experimental device for cutting jet supporting
CN107077122A (en) * 2014-10-29 2017-08-18 株式会社牧野铣床制作所 The control method of lathe and the control device of lathe
US10261495B2 (en) 2014-10-29 2019-04-16 Makino Milling Machine Co., Ltd. Controlling operation of a machining tool
CN107077122B (en) * 2014-10-29 2019-08-06 株式会社牧野铣床制作所 The control method of lathe and the control device of lathe
WO2016192308A1 (en) * 2015-05-29 2016-12-08 东莞思谷数字技术有限公司 Method for balancing external force load in machine tool spindle motor
CN105033760A (en) * 2015-08-18 2015-11-11 深圳市创世纪机械有限公司 Pre-warning system of numerical control machine tool
CN105312965A (en) * 2015-12-08 2016-02-10 华中科技大学 Breakage monitoring method for milling tool
CN105500111A (en) * 2015-12-25 2016-04-20 鼎奇(天津)主轴科技有限公司 No-load friction moment test method and control system of machine tool main shaft
CN106475855A (en) * 2016-11-22 2017-03-08 无锡职业技术学院 A kind of online detection instrument of main shaft of numerical control machine tool load and detection method
CN107450481A (en) * 2017-08-31 2017-12-08 福建工程学院 A kind of numerical control machine tool cutting velocity optimization method
CN107765647A (en) * 2017-09-20 2018-03-06 哈尔滨工业大学深圳研究生院 The intelligent speed planing method of processing is repeated based on high-volume single-piece
CN107838747A (en) * 2017-11-16 2018-03-27 山东大学 Cutting tool state intelligent control method based on industrial robot milling process
CN109822382A (en) * 2017-11-23 2019-05-31 上海铼钠克数控科技股份有限公司 The anti-collision machine system and control method of numerically-controlled machine tool
CN108620950A (en) * 2018-05-08 2018-10-09 华中科技大学无锡研究院 A kind of turning cutting tool drilling monitoring method and system

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