Compensation of pitch error of ball guide screw rises precision of fixed position of numerical control machine tool

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  • source:TRIANA CNC Machining
When numerical control machine tool is being machined, to control from the computation of machine program the machine tool undertakes machining is by automata of numerical control system. Because handlers cannot intervene, avoided factitious error, but at the same time also a few errors cannot be compensated artificially. Accordingly, put forward taller precision to ask to itself of numerical control machine tool. On this foundation, still hope to be able to develop the function of numerical control system adequately, compensate a few errors of numerical control machine tool automatically. Portant; Padding: 0px! Important;">portant; Padding: 0px! Important;"> is mixed to open loop machine tool of numerical control of half closed circuit, its locate precision basically depends on the precision of feed guide screw, because machine tool of this numerical control often uses guide screw of high accuracy ball. But screw always has production error, use for a long time can bring about wear away. Accordingly, the pitch error that raises a machine tool to locate one of commonly used methods of precision are pair of ball guide screw further undertakes compensating. Portant; Padding: 0px! Important;">portant; Padding: 0px! Important;">portant; Padding: 0px! Law of Important;">1, hardware compensates the principle Portant; Padding of pitch error of ball guide screw: 0px! Important;">portant; Padding: 0px! Important;">portant; Padding: 0px! Important;"> is before in machine tool of open loop numerical control, often use hardware method to compensate pitch error, the error of guide screw of some axis ball in using mechanical method to measure numerical control machine tool namely distributings curve, error value is accumulated to achieve a pulse in pitch equivalent the position installs a link stopper. When machine tool workbench is mobile, install the micro-gap switch on the machine tool every contact link stopper to give out an error to compensate signal, through dominating circuit instruction pace enters electric machinery to go more or take a few steps less. Portant; Padding: 0px! Important;">portant; Padding: 0px! Important;">portant; Padding: 0px! Method of compensation of this kind of intermittent pulse increased Important;"> a few mechanical components (if compensate lever, link stopper,wait. ) with circuit (the circuit that if will compensate signal,transmits numerical control device from micro-gap switch) the workbench to numerical control machine tool. In addition, method of this kind of compensation more the machine tool of open loop numerical control that applies to a pace to take electric machinery drive and method of pulse increment interpolation, and the machine tool of numerical control of half closed circuit that does not apply to DC or drive of communication servo electric machinery. Accordingly, at present machine tool of most numerical control uses software method to compensate the pitch error of ball guide screw. Portant; Padding: 0px! Important;">portant; Padding: 0px! Important;">portant; Padding: 0px! Law of Important;">2, software compensates the principle of pitch error of ball guide screw. Portant; Padding: 0px! Important;">portant; Padding: 0px! Important;">portant; Padding: 0px! The basic idea of compensation method of software of Important;"> pitch error is: Inside the whole journey limits of guide screw of the ball on axis of some of numerical control machine tool, with numerical control the instruction locates workbench the instruction regards as the position in certain position, the real position that measures a system to measure these places with high accuracy position (at present interferometer of major use laser serves as high accuracy to measure instrument) , have these real positions and instruction place comparative, computation gives ball guide screw to distributing in the error inside whole journey curve. The error arrives with the formal input of form in numerical control device. When numerical control device is controlling an axis to move later, error of can automatic consideration is worth and undertake compensating through the program of the work out. Portant; Padding: 0px! Important;">portant; Padding: 0px! Important;">portant; Padding: 0px! Device of Important;">3, test and result analyse Portant; Padding: 0px! Important;">portant; Padding: 0px! Important;">portant; Padding: 0px! Important;"> is with the fore-and-aft ball guide screw of milling machine of numerical control vertical exemple, the effective job length of this directional ball guide screw is 800mm, every 15mm dictates for the position is nodded in its 300mm length. The fixed position error that every statement position nods is measured (its resolution is 0. Interferometer of laser of 01 Um) Shuang Pin. Get the curve of fixed position error before compensation of error of a simple move or action, the curvilinear place that if pursue medium,the group gives is shown. After method of software of classics of error of a simple move or action is compensated, place of curve of the circle in locating error curve is like a graph is shown. Apparent, pass the compensation of pitch error, the fixed position precision of numerical control machine tool rises greatly. Portant; Padding: 0px! Important;">portant; Padding: 0px! Important;">portant; Padding: 0px! Compensation of Important;"> pitch error is one of efficient ways that raise precision of open loop and fixed position of machine tool of numerical control of half closed circuit, but not be all-purpose. Tigidity of daily transmission system and make what cause not accurately repeat set error to cannot be compensated. Additional, the pitch error of screw and environmental temperature have very big concern. Accordingly, want to raise the precision of numerical control machine tool further, use system of numerical control of complete closed circuit only. In system of numerical control of complete closed circuit, pitch error and a few otherer the error is in positional closed circuit, can be amended through closed circuit. CNC Milling