Study On The On-line Monitoring Of The Spindle Motor Current In Micro-hole Drilling

With the development the modern technology, especially in theaspects of miniaturization and integration of product, the numbers ofmicro-holes'machining has greatly increased, widely used in cars,laser machining, beam machining and spark discharge machining. However,machining by using drills tends to be the most useful in practice. .When drills are used to machine micro-holes there is the seriousdrawback in that the drill is mechanically weak and breaks easily,resulting in short-lived working drills. Besides this drawback, thestatistical scatter of micro-drill lives is large and it is verydifficulty to predict just how long the working life of a micro-drillmight be. This is important from the point of drill breakage resultsin part of the broken drill remaining trapped in the workpiece. Oftenit is impossible to extract this trapped part thereby causing workpiecewastage.Theory and experiment show that the main reason for the drillbreak is the increase of drilling force a after the workpiece havingwear .But it is difficult to obtain the macro-holes'drilling signal,much change need to be done to the tongs construction, and it will affectthe performance of the craft system. Its application is limited incertain degree. Based on development of the electrical spindle motorand controlling technique, the spindle motor brushless of high speedis widely applied. Because of low electric voltage and high electriccurrent relatively, it is possible to judge the cutting state bymonitoring the change of current and we don't need to change theconstruction of equipments. Little change will be taken to the powersupply circuit of the spindle motor. So we can do with that simply andeasily. Therefore, in this dissertation on-line monitoring system ofmicro drilling spindle motor's current is developed and on-linemonitoring experiment has been conducted basing on the dependabletheories.The dissertation develops an on-line monitoring hardware system ofmicro drilling. This system regards computer as the core, is controlledby the SCM to finish the movement of drilling's displacement .At thesame time, computer controls the AD card to gather the datum of the shaftmotor's current, and realize the serial communication among thecomputer and the SCM. To pick up main shaft's current signal, adoptsthe Hall electric current sensor which is rapid respond and good lineardegree.In feed control system, the step motor realizes spindle motorto feed. The controlling pulse is given by a SCM and the lightelectricity separates equipment insulates the SCM system and the stepmotor system, it can reduce system suffering and increase thedependability of the system. The experimental system regards LabVIEW software as the mainprogramming environment. Fully utilizes the intuitionistic andconvenient programming advantage of G language to realize transformingtraditional hardware instrument with software programming. Still havefinished the collection of the voltage signal, wave filtration,transferring, showing, storing and serial communication with SCM,etc.. This dissertation mainly study the distributing rule of Voltage-lowlimit value when micro-aiguille drills. It means the Voltage-lowbetween the shaft motor's current limit value which is transferred byI/V and the initialization value.Voltage-low limit value which can begot as the aiguille breaks possibly obeys normal distribution,log-normal distribution and Weibull distribution.The conclusion isthat the limit value of voltage difference obey the Weibull distributionof three parameters after the method illustrated table and analysis andKolmogorov test, Basing on the dependable theories, the dependablefunction and on-line monitoring mathematics model of spindle motor'scurrent can be deduced by the distribution function of the limited valueof voltage difference, then dependable voltage difference is easilygained using this model at a certain dependable degree. By the on-linemonitoring experiment of spindle motor's current basing on dependabledegree, the monitoring value calculated by mathematics model can avoidperfectly the drill breakage during the drilling process, whichprovides some theoretical basis and practical experience for achievingautomation of micro drilling process. Below is the innovation in this paper: 1.The dissertation develops an on-line monitoring closed loopsystem of spindle motor's current depending on PC. 2.Make the testing equipment of Hall current sensor by myself. Thisequipment has the characters of rapid respond, output signal'sstability and anti-interfere strongly etc. 3. It realizes the voltage of signal's collection, straining wave,show, function of storing etc and replaces traditional Visual C++...