Treatment of complete closed circuit exceeds the edge tool that nicety makes

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  • source:WILDA CNC Machining
During EMO2007, in exhibit a house all round, around subway and Han Nuowei downtown, ad saying everywhere of Hai Dehan is visible -- " the efficient way that assures machine tool precision: Complete closed circuit is machined " , "Complete closed circuit is machined " the concept is able to travel extensively. The interior that exhibit a house also exhibited Haidehan and Demaji cooperate exceed accurate production sharp weapon -- half closed circuit, complete closed circuit demonstrates unit. This unit showed the effect of half closed circuit and complete closed circuit to error of whole control loop well, the show that the grating a unit of length that demonstrated Haidehan at the same time leaves in different pollution environment. The reporter is demonstrating the spot to observe, complete closed circuit overcame the limitation of system of half closed-loop control, OK and direct sampling mounts servo drive in last class the position on mechanical movement component feedbacks component (like grating feet, magnetism bar rule, rotate the) such as coder, regard the position as annulus; And the coder feedback on electric machinery regards speed as annulus only right now, the gap that such servo can eliminate the presence on mechanical drive (wait like gear clearance, guide screw clearance) , compensate mechanical drive production error (wait like guide screw pitch error) , realize position of real complete closed circuit to control a function, obtain taller fixed position precision. The part that the spot reveals uses treatment of means of complete closed circuit, half closed circuit respectively, in the difference be clear at a glance on precision. Usually, servo of digital type communication is in mostly the control of half closed circuit works below means. Means of this kind of control is insuperable to the clearance on transmission catenary and error or compensation. To obtain taller control precision, the detecting element that should install high accuracy in final athletic part -- coder of grating feet, photoelectricity, realize full closed-loop control. Well-known, the machine tool is processing the source of error in the process, the geometrical structure error that basically contains a machine tool, error that flexibility is out of shape error and hot denaturation are caused. Among them, hot metamorphic error is occupied about 70% , accordingly it is the main source that machine tool error generates. Be based on this, to the machine tool with precision high demand, general need installs grating feet and angle coder to realize full closed-loop control, replace conventional half closed-loop control, realize high accuracy requirement thereby. British physicist L.

Rayleigh1874 year put forward: The foundation of metric grating technology is Mo Er stripe (Moire Fringes) . Till 20 centuries 50 time, the Mo Er streak that people just begins to use grating undertakes nicety measure. 1950, german Hai Dehan (Heidenhain) initiate DIADUR is duplicate craft, duplicate in the photoetching that plating chromium evaporates on vitreous substrate namely craft, the grating scale feet of cheap of this ability production high accuracy, price. Grating is metric the instrument is accepted for user place thereby, enter commodity market. Hai Dehan company begins to develop grating feet and round bar coder from 1961, make a bar be apart from for 4 μ M (250 lines / Mm) grating feet and 10000 lines / the round grating that turn surveys a system, the measurement that can realize 1 micron and 1 horn second resolution. Made 1966 gave bar to be apart from for 20 μ M (50 lines / Mm) enclosed linear grating coder. In 20 centuries 80 time roll out AURODUR craft again, the metallic strain line that came true to make tall reflectivity on makings of steel base material reflexes grating, and in grating a reference labels (null) increased to be apart from encode on the foundation. Advanced a kind of new interference principle again 1987, use diffractive grating to realize the measurement of accept rice class, allow fuller installation. Rolled out the EnDat that is used at absolutely coder 1997 two-way and serial fast and successive interface, make absolutely coder and increment coder same very convenient application at surveying a system. Now, grating surveys a system very perfect already, applied field is very extensive, whole world grating is linear year of crop of sensor control in 600 thousand, among them enclosed grating feet is occupied about 85% , feet of open type grating is occupied about 15% . And the grating foot that Hai Dehan company produces suits to exceed motion of accurate machine tool to detect more, be like the LI P401 of this company, material length 220 Mm, resolution is 2 Nm, use Zerodur material to be made achieve 0 coefficient of expansion almost (0.

1ppm/k) , activity feet space is 0.

6 ± 0.

1 Mm, low to environmental requirement, install and use convenient, go up because of this international especially Europe is numerous exceed accurate machine tool to produce business to choose ruler of Hai Dehan grating mostly. According to Haidehan Dr. Zhang Xingquan introduces CTO of Chinese limited company, when the machine tool uses half closed-loop control, feedback signal comes from the coder that goes up in electric machinery axis at installation, but right now the system cannot react the error outside feedback loop. And when using full closed-loop control, its feedback signal comes from the grating feet that goes up in athletic rod at installation. As a result of full closed-loop control when, closed circuit servo is a target with the final position of workbench directly, eliminated the full error that enters transmission system thereby, so precision relatively system of half closed circuit wants tall. "Taller to locating precision asks machine tool, the feed servo that must pay close attention to it is to use means of half closed circuit, still be means of complete closed circuit, the precision that must pay close attention to use detecting element reachs stability. " Zhang Xingquan points out. When the machine tool uses means of drive of servo of half closed circuit, precision stability should be affected by element of a few outsides, for example, because of working temperature change causes change of length of ball guide screw in transmission catenary, this makes workbench locates the position produces drift effect actually necessarily, affect the treatment precision that adds workpiece then. And means of full closed-loop control, can obtain taller than half closed circuit displacement precision. The position of servo of this kind of feed detects device installation carries out a component to go up in feed system endmost, its position or displacement measure actual measurement, and the coder that installation carries a department in drive electric machinery serves as detecting element, make speed ring. The position detects device chooses grating ruler more, the check of positional signal goes out is by grating reading the head is finished, rear sight grating (long grating) with demonstrative grating (short grating) install the mobile component in the machine tool and fixed component to go up respectively, both and mutual parallel, maintain between them 0.

05 or 0.

The clearance of 1. When edge of rear sight grating demonstrative grating moves continuously when, the photocurrent change pattern of induction of photoelectricity component place is similar sine is undee, after classics of this sine signal enlarge, plastics, differential circuitry is handled, changeover is digital pulse signal. Rear sight grating is mobile a bar is apart from generation pulse of a computation, will calculate with tally pulse number, can measure so that the displacement of machine tool workbench measures. The method that uses times frequency can raise the resolution precision of grating. The characteristic of grating feet is to measure precision tall, and precision can maintain for a long time. Zhang Xingquan says, at present method of full closed-loop control applies generally already at exceeding accurate machine tool to go up, the respect waits in precision, speed, dynamic sex apparent excel means of half closed circuit. Use the machine tool of structure of full closed-loop control, the heat of machine tool drive disk assembly is out of shape be in positional operating ring in, the error gets automatically compensating; Can eliminate through feedback arrive from electromotor the transmission error in the catenary of whole and mechanical drive of saddle of machine tool bed, get precision of very tall fixed position of machine tool static state thereby. Differ with system of half closed circuit, the compensation effect of system of complete closed circuit is distinct, follow machine tool operating mode scarcely, wear away of state and machine program differ and produce change, the machine tool can maintain initiative treatment precision for a long time. CNC Milling CNC Machining