CN114184158A - Method for measuring coaxiality of long-distance hole system in three-coordinate system - Google Patents
Method for measuring coaxiality of long-distance hole system in three-coordinate system Download PDFInfo
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- CN114184158A CN114184158A CN202111439404.7A CN202111439404A CN114184158A CN 114184158 A CN114184158 A CN 114184158A CN 202111439404 A CN202111439404 A CN 202111439404A CN 114184158 A CN114184158 A CN 114184158A
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- 238000005259 measurement Methods 0.000 abstract description 14
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- 238000000691 measurement method Methods 0.000 abstract description 4
- 238000007689 inspection Methods 0.000 abstract description 3
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B21/00—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant
- G01B21/22—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring angles or tapers; for testing the alignment of axes
- G01B21/24—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring angles or tapers; for testing the alignment of axes for testing alignment of axes
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Abstract
The invention provides a method for measuring coaxiality of a long-distance hole system in three coordinates, which belongs to the technical field of metering. The method is most suitable for the actual conditions of assembly and operation, has high requirement on the coaxiality of the long-distance hole system, good measurement stability, simple measurement method and convenient part inspection, and improves the detection precision and efficiency of the coaxiality of the workpiece.
Description
Technical Field
The invention belongs to the technical field of metering, and particularly relates to a method for measuring coaxiality of a long-distance hole system in three coordinates.
Background
For a long time, in the production and manufacturing process of diesel engines, the tolerance precision of some measured coaxiality of long-distance hole series workpieces needs to meet certain requirements. The coaxiality detection is that the coaxiality error is the variation of the deviation of a detected axis relative to a reference axis, the variation is reflected on the eccentricity of a circle center on a cross section, a measurement object of the coaxiality is a revolving body part, the coaxiality detection is a detection item frequently encountered in measurement work, the coaxiality detection is carried out by using three coordinates, and the coaxiality detection is visual and convenient. However, due to the different selection of the measurement method and the measurement reference, and the influence of factors such as the sampling strategy and the measurement environment, the phenomena of large measurement result error and poor repeatability often occur.
The error caused by the length and distance between the reference axis and the measured axis is called amplification error, which is one of the most controversial errors. Taking a typical case as an example: how accurately two short cylinders relatively far apart evaluate coaxiality. As shown in fig. 1, it is assumed here that the distance between two measurement cross sections on the reference is relatively small, the distance between one layer cross section of the reference and the first layer cross section of the measured cylinder is large, if there is a measurement error of 5 μm at the center position of the second cross section of the reference cylinder, according to the principle of similarity of triangles, the measurement axis has been enlarged to 50 μm when reaching the measured cross section, and the result of direct evaluation cannot truly reflect the actual situation of the part according to the coaxiality error of which the calculation power 50 × 2 is 100 μm. As shown in fig. 2, if the direct evaluation is performed as required, the result is that the reference axis is extended, and the maximum distance between the measured axis and the reference axis is multiplied by 2; if there is an error in the reference axis, after extension, the error will be amplified and introduced into the coaxiality calculation. To solve the above problem, a reasonable measurement method is selected to avoid the problem. For the above reasons, improvements are therefore proposed.
Disclosure of Invention
The technical problems solved by the invention are as follows: the invention provides a method for measuring the coaxiality of a long-distance hole system in three coordinates, which adopts a common reference axis, adopts a long axis as a reference by fitting two short axes, and calculates the coaxiality of the two short axes by using the long axis (a positioning minimum area method), and if two cylinders are regarded as a complete long cylinder, the result is approximately equal to and certainly greater than the straightness of the long cylinder axis (the minimum area method). The method is most suitable for the actual conditions of assembly and operation, has high requirement on the coaxiality of the long-distance hole system, good measurement stability, simple measurement method and convenient part inspection, and improves the detection precision and efficiency of the coaxiality of the workpiece.
The technical scheme adopted by the invention is as follows: the method for measuring the coaxiality of the long-distance hole system in three coordinates is a method for measuring the coaxiality error of a reference cylinder and a measured cylinder on a workpiece when the axial lengths of the reference cylinder and the measured cylinder are short and the distance between the reference cylinder and the measured cylinder is long, and comprises the following steps of:
step S1: measuring two layers of section circles at two ends of a reference cylinder and determining the circle centers of the section circles, measuring two layers of section circles at two ends of a measured cylinder and determining the circle centers of the section circles, and taking the circle center connecting line of the four layers of section circles obtained on the reference cylinder and the measured cylinder as a common reference axis;
step S2: evaluating the coaxiality of the axis of the reference cylinder relative to the common reference axis to obtain a reference cylinder axis error, and evaluating the coaxiality of the axis of the measured cylinder relative to the common reference axis to obtain a measured cylinder axis error;
step S3: comparing the reference cylinder axis error and the measured cylinder axis error obtained in the step S2, and taking the maximum value as the coaxiality error of the measured cylinder relative to the reference cylinder in the workpiece.
In the step S1, the centers of the two layers of cross-sectional circles and the cross-sectional circles on the reference cylinder and the centers of the two layers of cross-sectional circles and the cross-sectional circles on the measured cylinder are obtained by placing the workpiece on the coordinate measuring machine and calculating by the least square method, and the common reference axis is also automatically obtained by the coordinate measuring machine.
In the above step S2, the coaxiality of the axes of the reference cylinders with respect to the common reference axis and the coaxiality of the axes of the measured cylinders with respect to the common reference axis are both directly obtained on the coordinate measuring machine.
Compared with the prior art, the invention has the advantages that:
1. in the scheme, because the central element is controlled, the coaxiality is suitable for realizing the functional requirement of uniform wall thickness/quality, the coaxiality is also used for meeting the assembly requirement in cooperation with the dimensional tolerance, and in order to be closer to the real assembly condition and simplify the analysis process, the axis of the non-associated containing body is approximately used for replacing the derived central line. To avoid measurement errors as in the prior art, a common reference axis is used, and by fitting a long axis to two short axes as a reference and using this long axis to calculate the coaxiality of the two short axes (the minimum area method), if the two cylinders are considered as a complete long cylinder, the result is approximately equal to and certainly greater than the straightness of the axis of the long cylinder (the minimum area method). The method is most suitable for the actual conditions of assembly and operation, has high requirement on the coaxiality of the long-distance hole system and good measurement stability, and is suitable for being matched with the long-distance hole system;
2. the technical scheme has the advantages of simple measuring method, convenient part inspection and high workpiece coaxiality measuring efficiency, improves the detection precision and efficiency of the workpiece coaxiality, is particularly suitable for workpiece detection of assembly part coaxiality, and is convenient to popularize and use.
Drawings
FIG. 1 is a schematic view of a prior art measurement of the present invention;
FIG. 2 is a schematic diagram of direct coaxiality assessment in the prior art;
FIG. 3 is a diagram illustrating a lateral error analysis of coaxiality in an embodiment of the present invention;
FIG. 4 is a diagram illustrating longitudinal error analysis of coaxiality in an embodiment of the present invention;
FIG. 5 is a diagram illustrating a combined coaxiality error analysis according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Embodiments of the invention will be described in detail below with reference to figures 3-5:
the method for measuring the coaxiality of the long-distance hole system in three coordinates aims at measuring the coaxiality error when the axial length of a reference cylinder and the axial length of a measured cylinder on a workpiece are short and the distance between the reference cylinder and the measured cylinder is long. Two problems with large impact need to be solved first-a reasonable sampling strategy is adopted, and the impact of amplification errors is reduced. In short, the sampling strategy of the coaxiality evaluation characteristic is to select a reasonable sampling point mode to collect elements. When measuring the characteristics of a circle or a cylinder, the automatic point collection is utilized to eliminate the error of the point collection, the number of the collected points and the number of layers are properly increased, and the number of the collected points is required to reach a certain number because the measuring elements of the three-coordinate measuring mechanism depend on the least square method. The most common method is the common axis method.
The specific operation comprises the following steps:
step S1: measuring two layers of section circles at two ends of a reference cylinder and determining the circle centers of the section circles, measuring two layers of section circles at two ends of a measured cylinder and determining the circle centers of the section circles, and taking the circle center connecting line of the four layers of section circles obtained by the reference cylinder and the measured cylinder as a common reference axis;
the two layers of section circles on the reference cylinder and the circle centers of the section circles thereof as well as the two layers of section circle machines on the measured cylinder and the circle centers of the section circles thereof are obtained by placing a workpiece on a three-coordinate measuring instrument and automatically obtaining the workpiece through the three-coordinate measuring instrument, and the common reference axis is also automatically obtained through the three-coordinate measuring instrument.
Step S2: evaluating the coaxiality of the axis of the reference cylinder relative to the common reference axis to obtain a reference cylinder axis error, and evaluating the coaxiality of the axis of the measured cylinder relative to the common reference axis to obtain a measured cylinder axis error;
the coaxiality of the axes of the reference cylinders and the measured cylinders relative to the common reference axis are obtained directly on a three-coordinate measuring machine.
Step S3: and comparing the axis error of the reference cylinder and the axis error of the measured cylinder obtained in the step S2, and taking the maximum value as the coaxiality error of the measured cylinder relative to the reference cylinder in the workpiece.
The feasibility analysis of the common axis method is as follows: to more closely approximate the true assembly case and simplify the analysis process, the derived centerline is replaced by an uncorrelated container axis approximation below. As can be seen from FIG. 3 and FIG. 4, the maximum mandrel diameter allowed to pass under the control of 0.1 coaxiality is between D-0.05 and D-0.1. The common axis method fits a long axis through two short axes, and calculates the coaxiality of the two short axes with the long axis (the positioning minimum area method). And the maximum mandrel diameter that the long cylinder allows to pass through is D-t. As shown in FIG. 5, if t is 0.1, the common axis method is qualified, and the condition of unqualified is directly evaluated (the mandrel with D-0.1 can still pass in the case); if t is 0.05, the direct evaluation is qualified, and the common axis method evaluation is unqualified, so that the requirement is intensified.
The invention has high requirement on the coaxiality of long-distance hole systems and good measurement stability, and is suitable for matching use; the method is simple, the part is convenient to inspect, the detection precision and efficiency of the coaxiality of the workpiece are improved, and the method is particularly suitable for detecting the coaxiality of the assembly part and convenient to popularize and use.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.
Claims (3)
1. The method for measuring the coaxiality of the long-distance hole system in the three-coordinate system is characterized by comprising the following steps of: the measuring method is a coaxiality error measuring method aiming at the condition that the axial length of a reference cylinder and the axial length of a measured cylinder on a workpiece are short and the distance between the reference cylinder and the measured cylinder is long, and comprises the following steps:
step S1: measuring two layers of section circles at two ends of a reference cylinder and determining the circle centers of the section circles, measuring two layers of section circles at two ends of a measured cylinder and determining the circle centers of the section circles, and taking the circle center connecting line of the four layers of section circles obtained on the reference cylinder and the measured cylinder as a common reference axis;
step S2: evaluating the coaxiality of the axis of the reference cylinder relative to the common reference axis to obtain a reference cylinder axis error, and evaluating the coaxiality of the axis of the measured cylinder relative to the common reference axis to obtain a measured cylinder axis error;
step S3: comparing the reference cylinder axis error and the measured cylinder axis error obtained in the step S2, and taking the maximum value as the coaxiality error of the measured cylinder relative to the reference cylinder in the workpiece.
2. The method of measuring coaxiality of a long-range bore system in three coordinates according to claim 1, wherein: in the step S1, the centers of the two layers of cross-sectional circles and the cross-sectional circles on the reference cylinder and the centers of the two layers of cross-sectional circles and the cross-sectional circles on the measured cylinder are obtained by placing the workpiece on the coordinate measuring machine and calculating by the least square method, and the common reference axis is also automatically obtained by the coordinate measuring machine.
3. The method of measuring coaxiality of a long-range bore system in three coordinates according to claim 2, wherein: in the above step S2, the coaxiality of the axes of the reference cylinders with respect to the common reference axis and the coaxiality of the axes of the measured cylinders with respect to the common reference axis are both directly obtained on the coordinate measuring machine.
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| CN202111439404.7A CN114184158A (en) | 2021-11-30 | 2021-11-30 | Method for measuring coaxiality of long-distance hole system in three-coordinate system |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115183723A (en) * | 2022-06-13 | 2022-10-14 | 中国第一汽车股份有限公司 | Method for measuring coaxiality by combining axiality |
Citations (3)
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| CN102494595A (en) * | 2011-12-29 | 2012-06-13 | 南车洛阳机车有限公司 | Coaxiality detection apparatus |
| CN106091900A (en) * | 2016-06-20 | 2016-11-09 | 上海现代先进超精密制造中心有限公司 | Method by three-dimensional coordinates measurement two cylinder axiality |
| CN109696146A (en) * | 2019-01-08 | 2019-04-30 | 杭州大和热磁电子有限公司 | A kind of coaxiality detecting method |
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- 2021-11-30 CN CN202111439404.7A patent/CN114184158A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102494595A (en) * | 2011-12-29 | 2012-06-13 | 南车洛阳机车有限公司 | Coaxiality detection apparatus |
| CN106091900A (en) * | 2016-06-20 | 2016-11-09 | 上海现代先进超精密制造中心有限公司 | Method by three-dimensional coordinates measurement two cylinder axiality |
| CN109696146A (en) * | 2019-01-08 | 2019-04-30 | 杭州大和热磁电子有限公司 | A kind of coaxiality detecting method |
Non-Patent Citations (2)
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115183723A (en) * | 2022-06-13 | 2022-10-14 | 中国第一汽车股份有限公司 | Method for measuring coaxiality by combining axiality |
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