Precision of machining center geometry examines standard research

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source:LONTL CNC Machining

Machining center, the automatic machine tool of the specific interpose that serves as the person when eliminating to machine, its geometrical precision examines must the regularity requirement that bona fide report forms the point of a knife of workpiece outline surface to nod contrail of opposite workpiece motion inside its work area, accordingly, the key that its examine, the form that should be influence workpiece treatment precision. The article alters with respect to content during the geometrical precision in bigger ISO/DIS10791 examines to be carried out soon partly, the ministry of JB/GQ1140-89 machining center that contrasts to be being carried out at present promulgates standard, express a narrow view, discuss the rationality that precision of machining center geometry examines. 1 announce the linearity that the component of motion of two kinds of errors of component motion linearity moves along each reference axis, affect the appearance precision of workpiece directly not only, the positional precision that still affects work secondhand (the parallelism that moves through the component, verticality) with dimension precision (the) of fixed position precision that moves through the component, reason it is the key that precision of machining center geometry examines and foundation. Well-known, the sharp movement of the component always is containing 6 errors element: The either on athletic component has representative place (wait like center of dot of point of a knife, work or workbench center) a position error on athletic way, the angle error that two line sum of errors of this bits of contrail should nod orbit 3 times (graph 1) . When only when the linearity that axis of X of check component edge moves, eliminate position error EXX this element, should axis of Y of test point edge (inside XY plane) with Z axis (inside XZ plane) the EXY of line value error of directional translation, EXZ and dot circle X axis to tilt, the EAX of error of value of corner coming back that circles Y to the axis swings and circle Z axis to rise and fall, EBX and ECX of these 5 errors all, be short of one cannot (ought to point out, as a result of the influence of Abbe error, the different point on athletic component gets the influence rate that measures so that horn is worth linearity error is different) , because horn is worth line of sum of errors to be worth an error,this is it is two kinds of property completely different linearity error. Incorporate is in: (1) their formation mechanism differs completely, translation of component of the motion in moving causes line value error, horny cost error is athletic component rotates in move those who cause. (2) two kinds of errors from theoretic tell cannot direct and mutual conversion, cannot compensate another kind of error with a kind of error (of course, angle very hour, the corresponding arc value that error of the value that use a line represents to horn is worth an error approximately is permission) . (3) line is worth an error to use the length estimation with deviate linear ideal, horny cost error is deviate former the corner value that circles axes, with ratio, small part or small arc plan. (Error of 4) line value can be worth detector to provide with the line only (smooth feet and dial gauge, steel wire and microscope, collimation binoculars or laser interferometer) examine, horny cost error must be provided with angle check (gradienter, wait from interferometer of collimation appearance, laser) ability check goes out. Accordingly, little check in these 5 errors any, can cause the leakage check of linear error. For example, the linearity that uses workbench of check of feet of dial gauge peace to move along X axis only (graph 2) , it is no matter inside horizontal or vertical plane, metropolis occurrence graphic representation the sort of motion is actual and rough straight and dial gauge reading is changeless from beginning to end however (show flat) circumstance, leakage check horn is worth an error. Same, when the linearity that sheet uses gradienter or moves along X axis from workbench of collimation appearance check, also can not give a picture in the check inside horizontal or vertical plane 3 are shown in that way translation linearity error. Graph 1 horizontal machining center moves continuously sketch map of component motion error pursues the corner error that 2 workbench move continuously pursues the translation error that 3 workbench move continuously 2 machining center examine related standard of precision of new, old geometry the JB/GQ1140 that review analyse, linearity of motion of standard of precision of 89 machining center examines in JB/GQ1140-89 standard, to linearity of motion of each coordinate axes examine, have apparent leakage check appearance. For example the linearity with mobile axis of workbench edge X, the A that passes serial number G2 only and B two, detected axis of its edge Z (inside horizontal) with Y axis (inside vertical plane) the error of linearity of two lines value of translation, detected through serial number G3 again the error of horny cost linearity that it bypasses X axis to tilt, and leakage check it circles Y axis swing and circle Z axis rise and fall error of linearity of two character cost, because the machine tool of this certificate of proof still may be unqualified. Here ought to point out, g3 check the parallelism that calls shift does not accord with ISO230-1 ∶ 1996 in the definition of parallelism, it is a concept apparently not clear or the name nots agree with solid. Manage together, z axis direction is the same as likeness of X axis direction, check two lines value and the linearity error that bypass Z axis banking angle to be worth, leakage check circle X axis rise and fall to swing with what circle Y axis error of linearity of two character cost. And Y axis direction a check two lines are worth linearity error, error of horny cost linearity leaks entirely check. In addition, did not list at all examine main shaft and ram (when having this structure) the linearity error that moves along axes. Athletic parallelism and verticality examine in JB/GQ1140-89 standard, to concerning athletic parallelism examine, check the parallelism that main shaft axes moves to Z axis and X axis movement are right chamfer of workbench T form or the parallelism by the side of arris, and the main shaft that affects treatment precision badly and the parallelism that ram moves to Z axis along its axes and X axis move or Z axis motion is opposite the parallelism of workbench face did not list however examine. To concerning athletic verticality examine, also check vertical reference axis is right the verticality of workbench face, not the verticality that motion of check X axis moves to Y axis and Z axis moves. The positional precision of such a few mutual motion not check, assume ambiguous position, the geometrical precision of machine tool of not real report, apparent unreasonable, unscientific. The parallelism of the main shaft axes of static state of G11 place check and working mesa (horizontal) or verticality (vertical) , economic sense is not great, and of the linearity of chamfer of workbench T form of G19 static state detect, can cancel more, because this is the check of workbench spare parts. Precision of geometry of ISO/DIS10791 international standard examines to move partly linearity examines in ISO/DIS10791 standard, to X, Y and Z3 of error of linearity of reference axis motion detect, it is to press detect respectively the method of error of 3 angular displacement undertakes sum of errors of 2 displacement of the lines, the law of reasonable check proved recipe of linearity is narrated before be being accorded with completely. Should emphasize here those who point out is, y axis circles Y axis to tilt in athletic linearity the check law of heft, because gradienter cannot be placed, cannot use; And need to put illuminator on main shaft box from collimation appearance, cannot make sure the synchronism from collimation appearance and illuminator moves continuously again precision, unfavorable also with. Reason is shown 4 times like the graph, it is have the aid of is worth check to provide dial gauge and round angle square at the line, two when grow in workbench apart D locally, all move along Y axis dial gauge, 5 when be the same as a side generatrix at round angle square equidistant dot parts reading, computation measures high workbench every the poor value of two positions reading, can get (the greatest poor value, the least poor value) / the D in type of D=tand ≈ D -- circle error of Y axis banking angle to also be listed at the same time examined main shaft and ram edge linearity of its axes shift. Athletic parallelism and verticality examine ISO/DIS10791 standard (draft) , set what the parallelism between the component and verticality move related each to examine. The parallelism that already workbench face and main shaft axes move to relevant reference axis severally and verticality, the verticality between the parallelism that also main shaft and motion of axes of edge of main shaft ram move to Z axis and motion of each reference axis. These examining make clear, what new standard emphasizes is machining center what issue geometrical precision in condition of each component movement is comprehensive examine, and not check is dormant the geometrical precision of condition, this mirrorred axes of workbench face, main shaft and reference axis space directly the position when real work affects, also demonstrated form of immediate impact workpiece of precision, the positional precision between the reference axis when coordinate linkage, because this is reasonable. Replace old standard with new standard, be helpful for machine mass undoubtedly rise, imperative. 3 pairs of new standards (draft) linearity of a few deliberate is the base that parallelism and verticality measure, the author thinks to examining two linear parallel or perpendicular when should consider linearity error to go in, from this, the undermentioned content of new standard is worth deliberate. ISO/DIS10791 standard is aleatoric to Z and Y, Y and X and X and Z of verticality of two motion axes examine, all press two contrail the check law of mutual orthogonality, make first of angle square at the same time exact parallel at on the component a bit edge among them the orbit Ⅰ that a reference axis moves, the orbit Ⅱ diagonally foot that measures this a little bit to move along another reference axis again the another parallelism that hangs an edge, make the equidistant error of a certain number of dots is in allow difference (the measurement of verticality the measurement that essence is parallelism) . Press this check standard: Must stipulate component of orbit Ⅰ motion is supporting the firm position on slideway, and ask without this in new standard, this will be put in the leakage check phenomenon of partial error, bring about examine the demur of the result. Move with axis of workbench edge X now, the verticality that axis of Y of edge of main shaft box moves examines for exemple (graph 5) , the analysis is as follows: Inside the whole journey that moves in axis of workbench edge X, orbit Ⅰ has axis of Y of the edge in including XY plane for certain translation and circle Z axis to rise and fall horny error inside linearity error, adjust park smooth feet and orbit Ⅰ are accurate and parallel on workbench, also can be orbit only two end or narrow point are equidistant. The linearity error of orbit Ⅰ , circle Z axis to rise and fall especially the linearity error heft of horny error, be sure to bring about workbench to be in when the position differring inside the journey, the included angle of mesa and ideal X axes each different, axis of immediate impact X and the verticality error reading that Y axis moves. Visible, take no account of the linearity that workbench moves, will cause the check of leakage of this part error that causes from this, and the impact that considers linearity of X axis motion, must set detect feet of diagonal of Y axis motion the reasonable and firm position of the workbench when the another parallel that hang an edge, have check of leakage of this kind of bigger error possibly otherwise. The layout form that if the Z axis motion of the machine tool is pillar edge Z,moves point-blank to lathe bed (graph 5) , criterion X axis and the verticality that Y axis moves examine to still should set, detect orbit Ⅱ and angle square when the another parallel that hang an edge, pillar the firm position that goes up to lathe bed slideway in Z. The pillar that because grant axis of Y of edge of main shaft box motion,directs, need to finish the sharp movement of edge Z axis, the heft of linearity horn error that Z axis circles to rotate in motion will make pillar tilts, bring about main shaft box to move along the diagonal of axes of Y of ideal of a deviate, produce Y axis and the verticality error that X axis moves thereby. Apparent, pillar fixed position is in Z to different position, the dip of pillar also is different. The error of Y axis banking angle of linearity of motion of axis of graph 4 Y examines graph A, B, C -- 3 kinds of numeric size are equal but the linearity error DZs with different form, among them DZsa=dZsb=dZsc Ⅰ , Ⅱ , Ⅲ -- 3 kinds of direction and DZp of numeric and different parallelism alignment error, among them DZp1=0, the error size of DZp2 and DZp3 is equal way is opposite. Graph the sketch map that the linearity of 6 motion and the axis of synthetic graph 5 X of parallelism alignment error and verticality of Y axis motion examine is based on same argument, ISO/DIS10791 standard is examining when main shaft axes and the parallelism that Z axis moves, did not consider the impact of error of linearity of Y axis motion, the affirmatory height that did not set main shaft box to go up in pillar. Examine respectively Kong Ji of straight fixed position of the platoon on working mesa allows and workbench side fixed position is standard when the parallelism that moves to Z axis, did not consider X axis to move to circle Y axis to swing inside XZ plane the influence of heft of linearity horn error, did not stipulate workbench is in the firm position of X direction. They will be brought about examine the uncertainty of the result, carry out finally hard carry out. To the component that moves along a reference axis, by the machine tool layout with the oriented component that moves along another reference axis, if pursue 1 in the position condition with the oriented slide carriage that the workbench that moves along X axis is moved on lathe bed by edge Z axis, still existing the problem of complex of two parts error that the linearity that workbench moves is affected by linearity of slide carriage motion. Circle the heft of error of this linearity horn that Y axis swings because of what slide carriage moves, will make slide carriage tilts, bring about slide carriage to go up originally parallel moves at the workbench of ideal X axis slideway, produced parallelism alignment error, bring about the accretion of error of linearity of final workbench motion thereby. The graph is shown 6 times be in for workbench X to total travel L inside, the A with poor same value, B, c3 is planted DZs of type linearity error, be in by slide carriage Z differs 3 kinds to the Ⅰ of 3 positions, Ⅱ , Ⅲ banking angle influence, when the DZp of parallelism alignment error that add generation workbench moves, workbench compounds the metabolic condition of error DZs+p. Can see, the effect of the linearity that the linearity that axis of Z of slide carriage edge moves moves to axis of workbench edge X is very distinct, cannot ignore, ISO/DIS10971 standard did not consider this influencing factor, what can affect it directly apparently is accurate with reasonable. CNC MillingCNC Machining