# 3 coordinate measure shallow analyse machine the error analysis that measures coaxial to spend

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3 coordinate measure the definition that the influencing factor that casing aperture coaxial spends spends according to coaxial, OK and clear coaxial spends tolerancepublic errand belt, knowable influence measures casing aperture coaxial to spend the element of the error: ① is measured the central line of object aperture bends; ② is measured the central line photograph of object aperture tilts to generation of fiducial aperture axes; ③ is measured the axes position photograph of object aperture produces deflection to the position of fiducial axes. Spend the main factor of the error according to affecting casing aperture coaxial, when measuring coaxial to spend with CMM, can inspect its to measure an error from 3 respects: (1) the collection of fiducial axes and build; (2) the collection of axes of the element that be measured and build; (3) the evaluation that the position affects between fiducial axes and axes of the element that be measured. From measure say on the principle, with the coordinate position that what CMM measures directly is dot of on the workpiece that be measured a few features, need obtains the value of the parameter that be measured through software operation ability, the appearance error that because this is measured,precision basically gets workpiece itself, measure equipment error, outside ambient error, measure software algorithm error, coefficient of sensitivity and measure plan to wait for element influence, measure plan and effect of coefficient of sensitivity among them the biggest. Reasonable measurement plan is to point to same workpiece falls in same environment, reasonable arrangement measures check the number to reach the place that be measured, obtain in order to compare economic ground more accurate taller measurement precision. Arrive to get taller measure precision, the method that can survey plan through the change and measures for many times will obtain. Accordingly, using 3 coordinate to measure machine when measuring coaxial to spend, to raise metrical precision level to should use scientific and reasonable measurement plan is mixed reduce coefficient of sensitivity. 2.

The method that reduces 3 coordinate to measure coaxial to spend an error measures the precision level that coaxial spends to rise, at the same time sensitize coefficient comes to measuring the influence of precision to decrease the smallest, can use the following science to survey plan reasonably. 2.

1 increase fiducial and sectional when the distance between is measuring fiducial element, to reduce error interference, when measuring, should make as far as possible the first sectional with the 2nd sectional the distance between is pulled big. 2.

2 build common spool thread to be mixed when fiducial cylinder as fiducial axes the cylinder that be measured is shorter, and between two cylinder further when, measure respectively a fiducial cylinder and of the cylinder that be measured in sectional, next with in sectional the centre of a circle regards common spool thread as even the line, the coaxial of workpiece spends an error to take the cylinder that be measured and fiducial cylinder to spend maximum at the coaxial of common spool thread relatively. 2.

3 coaxial are spent replace approximately with linearity should be measured to work sectional shorter when, axes deflection is the main influencing factor that workpiece assembles, of the axis tilt to assemble an influence to workpiece lesser, can use those who change the method that measures linearity to replace coaxial spend to measure. Double of the linearity that measures axes deflection to measure axes to connect a line namely actually. 2.

The 4 real cases that try workpiece of the consideration that spur a law, coaxial is spent but direct basis is measured the largest space of element and fiducial element will calculate. With " long axis short aperture " model the coaxial of workpiece is spent measure for exemple. Size of this kind of workpiece is larger, use groovy method to cannot detect, design a requirement to make CMM measures a result to accord with, the end panel that can use opening serves as fiducial, two end short columnar cent undertakes metrical into a certain number of sectional circles next will sectional circle is umbriferous go up to end panel, find out the biggest the centre of a circle to be apart from through computation, the coaxial of two end aperture is spent be apart from for the biggest the centre of a circle of 2 times namely. 2.

5 positions spend a way the datum plane precision when workpiece is taller, and the element that be measured is round when, set fiducial element the centre of a circle for origin, measure the element that be measured next, coaxial spends the coordinate deviation according to its the centre of a circle to judge. 3.

The logical choice coaxial that coaxial spends measurement technique spends measurement technique a lot of, can choose corresponding method according to different type, specific if express,1 is shown. 4.

3 coordinate coaxial spends error example to measure an analysis this second coaxial is spent measure case blueprint (if the graph is shown 1 times) originate actual factory, the coaxial that need measures spends an error to have two: AB aperture coaxial spends coaxial of aperture of AC of sum of errors to spend an error. Fiducial aperture A is mixed in this case B of the aperture that be measured, C is the aperture that boring of essence of life comes out, exterior quality and treatment precision are better, can be informed the axes that be measured and fiducial axes so tilt and the main reason that deflection is generation error. The length in this case is A of 50mm fiducial aperture relatively length is measured for 25mm aperture B is long, and adjacent of two aperture photograph. Measure 3 coordinate of use BS8650 ― L/CS this machine, use diametical 2mm measure a ball, the measurement that uses form a complete set undertakes metrical to two aperture of A, B. Be in above all fiducial aperture A is apparently even take 3 sectional, every sectional measure 6 to nod respectively, get 3 the centre of a circle, through these 3 the centre of a circle construction gives fiducial axes, set this main spool thread finally for X axis, set coordinate origin in aperture of A, B intersect place. Adopt same method to measure B giving opening, can get photograph of B of the aperture that be measured spend an error to the coaxial of fiducial aperture A directly. The coaxial that alternates different position is measured 9 times on machine is measured to spend an error in 3 coordinate, it is respectively 0.

2190mm, 0.

2320mm, 0.

0241mm, 0.

0225mm, 0.

0228, 0.

0228mm, 0.

0235mm, 0.

0234mm, 0.

0240mm. From afore-mentioned measurement the result is knowable, maximum and the least value differ 0.

0022mm, satisfy 3 coordinate to measure machine error range, explain two aperture of A, B accord with true treatment. The length in this case is 500mm to be measured relative to length for A of 50mm fiducial aperture aperture C not photograph adjacent and two aperture apart is further, fiducial aperture A is shorter, measureable sectional the distance between is shorter, bring about coefficient of sensitivity bigger, should measure directly get C of the aperture that be measured spend an error to because fiducial aperture is fictitious,meet what lengthen and arise not to accord with effective treatment circumstance at the coaxial of fiducial aperture A relatively bigger measure an error. Accordingly, the 3 coordinate that cannot choose AB aperture measure plan to measure AC aperture. Coaxial spends the place in the logical choice of measurement technique to narrate above the basis, should choose beg be apart from law or position to spend indirect method of measurement to measure C aperture to be spent relative to the coaxial at A aperture. 5.

The last word is using 3 coordinate to measure machine undertake coaxial is spent when measuring, because get the influence of many sided, so coaxial is spent whether accurate the factor that measures need consideration is more also, need considers integratedly to machine craft and assemble actually. No matter use which kinds of measurement technique, answer to use 3 coordinate to measure a function automatically as far as possible, avoid a hand to move measure those who bring " cosine error " ; When collecting data, take more as far as possible sectional count with measurement point; Can undertake constructional test and verify below the condition that allows in the condition, same perhaps kind plan uses many 3 coordinate to measure machine undertake parting metrical, in order to obtain science, correct measurement result. Bibliographical reference [1] Yang Weidong.

3 coordinate are measured machine detect coaxial of machining spare parts spends an error to analyse [J] .

Information of science and technology, 2012.

[2] Zhang Hui.

The measurement technique that is based on 3 coordinate to measure machine coaxial to spend [J] .

Modern production technology and equipment, 2010.

[3] Wang Wenshu.

3 coordinate are measured machine discuss to what coaxial spends error measurement technique [J] .

Production technology and machine tool, 2010.