To get used to the different need of the user, the machining center with various breed was rolled out on the international market. Bring to the user on one hand convenient, enlarged the limits of machining center of choose and buy, especially professional stronger user, optional buy the machine tool that suits our company to use. But professional to those not very strong user brings a trouble, in wanting the machine tool in basic function likeness, go undertaking definitely choose, so that the choose and buy arrives,suit our company to use a requirement and cheap machining center. Normally, the user is before machining center of choose and buy, want above all from economy and technology two respects undertake evaluating to its. So-called economy evaluation basically is the price that points to a machine tool, be needed to deserve to buy optional the price of accessory and after service charge. The technology evaluates the specifications that is pair of machining center to make comprehensive assessment. After filling a specifications that masters machining center of some kind of model only, is ability right it? " of Quot; cost function makes relatively successful conclusion. Normally, the project that undertakes to machining center the technology evaluates can divide for the following 3 kinds big: · norms includes to process dimension volume of the space among them, limits of main shaft rotate speed, feed speed limits, the size of normative cutting tool and limits, the ability of numerical control device and optional of accessory sort more or less to wait. · function includes static precision, treatment precision, mobile precision, fixed position precision, heat to be out of shape the state is mixed among them fight oscillatory function to wait. · other includes the adaptability with the system among them, maintenance is convenient, the technology supports system and security to wait. In last few years, international Organization for Standardization (the method that ISO) developed function of a few pairs of machine tools to undertake evaluating, and formulate precision of static precision treatment, fixed position precision, repeat precision, heat to be out of shape the level that reachs the trial such as circular motion. To facilitate everybody understands and apply these standards, the article will experiment to circular motion and the concerned content of experiment of fixed position precision makes one introduction. Circular motion experiment and the experiment method that its use circular motion experiment in ISO230/4 circular motion compasses of standard the Communist Party of China is method of 3 kinds of experiments. · measures the method of head and fiducial cylinder with one dimension. · measures head and fiducial circle with two dimension board method. · uses bat method. The applied range that circular motion experiments is very wide, after can be being used at purchasing new machine tool examine into the factory, maintain regularly the test when the examination, still can use at logarithm to be worth those who control all sorts of parameter to adjust etc. When using arc interpolation instruction to undertake machining especially, it can produce tremendous effect. Although be in geometrical appearance error, can go to the lavatory to also see the situation of verticality from course. Still having is to measure backlash, even if the static method that measures feed to quit the position in that way according to experiment of fixed position precision, also be to use feed speed to measure backlash actually. This is a very important characteristic. Use circular motion experiment to be able to make judgement to the following project. · circularity precision wraps the workpiece circularity when be being machined with circular arc interpolation among them, the protruding when changeover is quadrantal takes volume (the degree of outstanding motion) , the installation precision of ball guide screw (appear periodic error) . · backlash precision namely the size of the backlash between two axes (it is to use feed speed to undertake evaluating actually) . Precision of · geometry appearance namely the size of the size of verticality error and linearity error. Precision of · fixed position namely the consistency degree of precision of two axes fixed position and have amendatory volume to span error. · numeric pilot adjusts degree to be opposite namely the adjustment of servo gain degree (positional annulus gain, speed annulus gain) with error following (the radius when rate rises is contractible state) . The application of result of circular motion test undertakes to machine tool function the experiment is 3 plane of the G02 that codes from use G and G03 evaluating circular motion, namely the result understanding that interpolation of the circular arc inside XY plane, YZ plane and ZX plane moves: · is mixed in the verticality inside limits of error of geometrical figure movement linearity. · is inside limits of set of parameter of numerical control device, to gain (positional annulus gain, speed annulus gain) , span error fills and backlash error compensation is proper. The inherent radius of · servo orgnaization is contractible. · other error, the encode that if shield is adjustable,waits with other motion workbench, bracket whether physical sex is interfered. The first phase that predicts to will be used at consign machine tool henceforth is mixed to feed speed measure all sorts of change such as radius to try to determine. If a machine tool looks,have apparent error, its reason nothing more than it is to backlash, verticality appears gain of annulus of error, position is abhorrent narrow with radius wait for 4 respects. When the small diameter that rotates to high speed recently especially establishs milling cutter feed, its speed is compared before rate is gotten high much, consequently circular motion experiment becomes a kind of main evaluation factor. To be being machined of workpiece precision forecast the measurement from circular motion to be able to master well as a result be added the circularity state of workpiece. Should use rotate when cutting tool cutting, will appear the smooth leveling effect that is more than cutting tool radius, often do not identify the tiny and concave and convex appearance that gives to be obtained with place of circular motion experiment. This is caused because of cutting tool be sufferringed by cutting workpiece and the influence that cut bits. And the course that gets by place of circumferential precision motion does not include this kind of effect. But from the circular motion that comes from an user test result is mixed measure the result that give to look with circularity measuring instrument, the result that circular motion experiments not very accurate, and can obtain more accurate result *C with cutting method the opinion that consequently somebody offers to use result of circular motion test no longer. The main reason that produces afore-mentioned problems is to using circularity measuring instrument to make when measuring, want to use low connect filter. If use 15 the result experiments with circular motion when ending with 25 wave crest not photograph be identical. When ending with 500 wave crest, can obtain completely consistent. Recently, when machining small part and small-sized mould component, the influence that discovery uses diameter of afore-mentioned half-and-half of set of parameter of numerical control device to narrow is more than the error of appearance of machine tool geometry of of course of small radius circular motion. But the unit that buys way of measurable smaller part very hard at present, so the hope develops cheap measurement unit. Machining center of choose and buy uses an end to the investigation basis of of circular motion course, undertake investigating to the circular motion course of the machine tool beforehand, can be opposite whether can this machine tool satisfy treatment precision to ask to make judgement, right the appearance of whole circle, when exchange is quadrantal dash forward the volume that take, tiny oscillatory component, the inherent difference value such as the periodic error, step difference that forms by span error compensation tries to affirm. OK and candid ground says, these are the poor values that technical capability causes. Carry out span error compensation often for example, the step that can discover span error compensates place course so is wrong. When this kind of step poor value arrives greatly cannot when oversight, so explain error of this kind of span compensates methodological impropriety. Because used the ball guide screw with big error and scale feet be caused by,can saying is. This kind of beforehand has the investigation of circular motion course, the design skill that can show machine tool structure clearly and assemble a technology, if guide,allow the design technology of the face, the design technology of feed drive system, and the feature of complex degree of polymerization of they and numerical control parameter. The importance that experiment of fixed position precision locates precision experiments experiments according to the fixed position precision of ISO230/2 standard, it is to be inside limits of whole and mobile length (be less than to length 2, the axis of 000mm) , least to what appoint at 5 o'clock, most the target had fixed position at 21 o'clock, the set value of the via 5 reciprocate each target seat that gives to begging next and the deviation value that quit the position actually undertake evaluating. The deviation average that will measure chief instrument place to obtain with laser and its disperse serve as pressing with a finger, beg the standard deviation σ that gives measured value, by appoint a project to beg an evaluation to be worth. Evaluation project relapses poor B=max[1Bil] of mutual the biggest changeover, on average poor B=1/mBi, only way relapses ↑ of =max[Ri of precision R ↑ ] with ↓ of R ↓ =max[Ri] and two-way repeatedly precision R=max[R1] 10. The desire gives these evaluations to be worth is not a very simple thing. But the dependency that these evaluation values can prove it and treatment precision not only, still can know the close extent that fastens each project and dimension precision concern. The data that fixed position precision uses is all sorts of parameter in rank form. If be opposite,for fundamental expression with the standard the method does not understand very, chose the machine tool of exorbitant precision infructuously so probably. If good machine tool is installed in him workshop, undertake metrical to it directly later, cannot measure its original precision likely. The compasses in the standard yes postulate is comprehensive ground integrated the user decides with the opinion of the manufactory. Have feed rate among them (include fast feed and specific feed rate) , warm-up movement condition (how does warm-up run? With why to plant is feed condition carried out? ) and measure environmental temperature (how to install constant temperature treasure? The temperature of constant temperature treasure how? ) wait. These projects should try to decide beforehand. Had told above, the numerical value in pair of trade catalogue want when choice machine is planted tries to compare. But what must notice is rank trade catalogue medium numerical value explains scarcely is to be in how to be obtained below the condition. But in be being used actually, the condition of the requirement that probable user place has and manufactory is abhorrent, cause the numerical value in checking result and sample to be not accorded with. One of experiment conditions are warm-up movement condition. An axis need of some machine tools runs continuously after a few hours ability is stable. And in workshop, after normally classics warm-up runs, begin to measure namely. Sometimes as a result of the machine tool gradually cold and the distance is ceaseless between occurrence target position positional phenomenon. To get stable result, below the condition that runs without warm-up, undertake metrical with very short time. Measure 5 times according to standard regulation, undertake iteration metrical next. Basically can master the steady state of the machine tool so. The result that the application of result of test of fixed position precision locates precision experiments can serve as span error compensation and backlash to compensate a value to try to apply. The result of test of fixed position precision that introduces above and the dimension precision of the workpiece that be added and positional precision have the concern with immediate . Precision relapses to two-way fixed position in ISO standard when taking degree seriously to locate at only way very relapse precision. Because will tell to target position, be more than the disperse level that approachs cutting tool from a direction to the dimension disperse degree when be close to cutting tool respectively with negative direction from square when workpiece. When machining cubic flank for example, show the precision that dimension estimation is worth between two plane the poorest. Anyhow, the fixed position precision that carries out when choice machine is planted experiments, the hope is in agree with completely user use shape can fall undertake, use achieves evaluation result. The main problem in locating the problem of precision experiment locates precision experiments is to not was in agree with completely undertake determining below the condition of user use condition. It is especially when the add production of large quantities of quantities, want movement for a long time to machine machine tool of many spare parts. In this during whether can stabilize from beginning to end be in in as same as result of earnings of experiment of fixed position precision position is a very big question. This kind of phenomenon is right before when numerical control machine tool machines precision to ask to be 10um level, still do not have how old problem. And the treatment precision of the product asks to reach the level that exceeds micron now, that cannot overlook the change of fixed position precision that change in the temperature in movement as a result of the machine tool and causes. After emphasizing purchasing new machine tool particularly now so, undertake locating precision experiments below the condition that must closing with conform to of effective treatment status. CNC Milling