A method for converting location tolerance to coordinate dimension tolerance

Abstract

The application provides a calculation method for converting position tolerance into coordinate size tolerance, belongs to the technical field of position tolerance measurement, and is used for calculating the position tolerance with a symbol phi in front of the position tolerance value, and comprises the following steps: S1, selecting a theoretical geometric model of the position tolerance and corresponding mathematical formula according to the characteristics of the position tolerance; S2, determining a theoretical correct size of the position tolerance; S3, calculating the ratio of the nominal value of the coordinate size according to the theoretical correct size; S4, obtaining the coordinate size tolerance by using the equal distribution method; S5, substituting the mathematical formula into Excel to obtain an Excel calculation model; and S6, substituting the theoretical correct size and the trial size into the Excel calculation model to obtain the coordinate size tolerance. The method converts the difficult-to-measure position tolerance into the visually measurable coordinate size, uses the distance size meter to replace the actual position tolerance, so that the position tolerance can be measured simply and conveniently, and clear coordinate size data is provided for actual processing.

Description

Technical Field

[0001] This invention belongs to the field of coordinate measuring technology, specifically relating to a calculation method for converting position tolerance into coordinate dimension tolerance. Background Technology

[0002] In geometric tolerance measurement, position measurement is recognized as one of the most challenging aspects. Position tolerance, as an important concept in geometric tolerance, is used to control the allowable variation of the actual position of an element (such as a point, line, surface, or hole) relative to its theoretical position. It is usually defined by a tolerance zone of a curve / surface, and the extraction center of the actual element must fall within this tolerance zone.

[0003] Currently, by having the surveyor click the "Position Degree" button on the coordinate measuring machine, the software instantly completes all the complex mathematical calculations (coordinate system changes, vector calculations, least squares fitting, etc.). If the user does not have a deep understanding, it is difficult to judge whether the results fitted by the software are reasonable, or if anomalies occur, they will not know how to troubleshoot.

[0004] Given the above background, positional tolerances are difficult to measure intuitively. Therefore, a method is needed to convert these difficult-to-measure positional tolerances into intuitively measurable coordinate dimensional tolerances. Summary of the Invention

[0005] The purpose of this invention is to solve the problem that positional tolerances cannot be directly measured in actual engineering, and to provide a method for converting positional tolerances into coordinate dimensional tolerances that can be directly measured.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for calculating position tolerance to coordinate dimension tolerance, used to calculate position tolerance values ​​with the sign φ, comprising: S1: Based on the characteristics of position degree, select the theoretical geometric model of position degree and the corresponding mathematical formula. The characteristics of position degree include the number of references, position degree tolerance value and annotation elements of the drawing. The mathematical formula is the position degree expression formula. S2: Determine the theoretically correct dimensions for positional accuracy; S3: Calculate the ratio of the nominal values ​​of the coordinate dimensions based on the theoretically correct dimensions, and select to proceed to S4 or S5 based on the ratio; S4: Obtain coordinate dimension tolerances using the amortization method; S5: Substitute the mathematical formula selected in S1 into Excel to obtain the Excel calculation model; S6: Substitute the theoretically correct dimensions and trial dimensions obtained in S2 into the Excel calculation model in S5 to obtain the coordinate dimension tolerance.

[0007] The method for converting positional tolerance into coordinate dimension tolerance provided by this invention also has the following technical feature: when the positional tolerance features include two references and the drawing annotation element is a single shallow hole, the theoretical geometric model is a planar circle model. When the positional feature includes three references and the drawing annotation element is a single deep hole, the theoretical geometric model is a cylindrical model. When the positional feature includes one or two references, and the drawing annotation elements are a set of circumferentially distributed holes, the theoretical geometric model is a rotary shaft type model.

[0008] The method for converting positional tolerance into coordinate dimension tolerance provided by this invention also has the following technical feature: when the theoretical geometric model is a planar circular model, the mathematical formula is:

[0009] Where D is the positional tolerance value; When the theoretical geometric model is a cylindrical model, the mathematical formula is:

[0010] Where D is the positional tolerance value, and no less than two sets of data are measured in the reference direction perpendicular to the hole; When the theoretical geometric model is a rotation axis type model, the mathematical formula is:

[0011] Where D is the positional tolerance value.

[0012] The method for converting position tolerance into coordinate dimension tolerance provided by the present invention also has the following technical feature: in step S2, determining the theoretically correct size of the position tolerance includes the coordinate dimension marked with a box starting from the datum plane as the theoretically correct size.

[0013] The method for converting positional tolerance into coordinate dimension tolerance provided by the present invention also has the following technical features: in step S3, when the ratio of the nominal values ​​of the two coordinate dimensions is between 1 and 1.2, proceed to step S4; when the ratio of the nominal values ​​of the two coordinate dimensions is greater than 1.2, proceed to step S5.

[0014] The method for converting positional tolerance into coordinate dimension tolerance provided by this invention also has the following technical feature: step S4 obtains the coordinate dimension tolerance according to the following table:

[0015] The method for converting positional tolerance into coordinate dimension tolerance provided by the present invention also has the following technical features: S6 includes: trial selection of actual values ​​of coordinate dimensions, using the idea of ​​infinite approximation to change the criterion from qualified to unqualified, and then changing the criterion from unqualified to qualified, to find the actual value closest to the critical maximum value, and the difference between the actual value and the theoretically correct size is the one-sided deviation of the coordinate dimension tolerance.

[0016] The method for converting positional tolerance into coordinate dimension tolerance provided by this invention also has the following technical feature: during the trial selection process, more tolerance can be allocated to those with larger nominal values, and less tolerance can be allocated to those with smaller nominal dimensions.

[0017] Beneficial effects: Compared with the prior art, the method for converting positional tolerance into coordinate dimension tolerance provided by this invention converts the difficult-to-measure positional tolerance into a coordinate dimension that can be measured intuitively, and uses the distance dimension meter to replace the actual positional tolerance, thereby enabling simple and convenient measurement, providing guidance for the investigation and analysis of positional tolerance errors, and providing clear coordinate dimension data for actual processing. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the positional degree of a point in a two-dimensional plane. Figure 2 This is a schematic diagram of the position of a line in any direction. Figure 3 This is a schematic diagram of the positional tolerance of the rotary axis. Figure 4 This is a schematic diagram of Excel criteria for different types of position degrees. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be noted that these embodiments are not intended to limit the present invention. Equivalent changes or substitutions in function, method, or structure made by those skilled in the art based on these embodiments are all within the protection scope of the present invention.

[0021] In the description of the embodiments of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the invention.

[0022] Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0023] The terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art will understand the specific meaning of these terms in this invention based on the specific circumstances.

[0024] like Figure 1-4 As shown, this embodiment of the invention provides a method for calculating position tolerances by converting position tolerances into coordinate dimension tolerances, used to calculate position tolerance values ​​with the sign φ, including: S1: Based on the characteristics of position degree, select the theoretical geometric model of position degree and the corresponding mathematical formula. The characteristics of position degree include the number of references, position degree tolerance value and annotation elements of the drawing. The mathematical formula is the position degree expression formula. S2: Determine the theoretically correct dimensions for positional accuracy; S3: Calculate the ratio of the nominal values ​​of the coordinate dimensions based on the theoretically correct dimensions, and select to proceed to S4 or S5 based on the ratio; S4: Obtain coordinate dimension tolerances using the amortization method; S5: Substitute the mathematical formula selected in S1 into Excel to obtain the Excel calculation model; S6: Substitute the theoretically correct dimensions and trial dimensions obtained in S2 into the Excel calculation model in S5 to obtain the coordinate dimension tolerance.

[0025] In some embodiments, When the positional feature includes two references and the drawing annotation element is a single shallow hole, the theoretical geometric model is a planar circle model. When the positional feature includes three references and the drawing annotation element is a single deep hole, the theoretical geometric model is a cylindrical model. When the positional feature includes one or two references, and the drawing annotation elements are a set of circumferentially distributed holes, the theoretical geometric model is a rotary shaft type model.

[0026] In some embodiments, When the theoretical geometric model is a planar circular model, the mathematical formula is:

[0027] Where D is the positional tolerance value; When the theoretical geometric model is a cylindrical model, the mathematical formula is:

[0028] Where D is the positional tolerance value, and no less than two sets of data are measured in the reference direction perpendicular to the hole; When the theoretical geometric model is a rotation axis type model, the mathematical formula is:

[0029] Where D is the positional tolerance value.

[0030] In some embodiments, in step S2, determining the theoretically correct size of the positional accuracy includes the coordinate dimensions marked with a box starting from the reference plane as the theoretically correct size.

[0031] In some embodiments, in step S3, when the ratio of the nominal values ​​of the two coordinate dimensions is between 1 and 1.2, the process proceeds to step S4; when the ratio of the nominal values ​​of the two coordinate dimensions is greater than 1.2, the process proceeds to step S5.

[0032] In some embodiments, step S4 obtains the coordinate dimension tolerance according to the following table:

[0033] In some embodiments, S6 includes: trying to select the actual value of the coordinate dimension, using the idea of ​​infinite approximation to change the criterion from qualified to unqualified, and then changing the criterion from unqualified to qualified, to find the actual value that is closest to the critical maximum value, and the difference between the actual value and the theoretically correct dimension is the one-sided deviation of the coordinate dimension tolerance.

[0034] In some embodiments, during the trial selection process, a larger tolerance can be assigned to those with larger nominal values, and a smaller tolerance can be assigned to those with smaller nominal dimensions.

[0035] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention. The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the protection scope of the present invention.

Claims

1. A method for calculating positional tolerances to coordinate dimensions, characterized in that, The position tolerance value with the sign φ used for calculation includes: S1: Based on the characteristics of position degree, select the theoretical geometric model of position degree and the corresponding mathematical formula. The characteristics of position degree include the number of references, position degree tolerance value and annotation elements of the drawing. The mathematical formula is the position degree expression formula. S2: Determine the theoretically correct dimensions for positional accuracy; S3: Calculate the ratio of the nominal values ​​of the coordinate dimensions based on the theoretically correct dimensions, and select to proceed to S4 or S5 based on the ratio; S4: Obtain coordinate dimension tolerances using the amortization method; S5: Substitute the mathematical formula selected in S1 into Excel to obtain the Excel calculation model; S6: Substitute the theoretically correct dimensions and trial dimensions obtained in S2 into the Excel calculation model in S5 to obtain the coordinate dimension tolerances. When the positional feature includes two references and the drawing annotation element is a single shallow hole, the theoretical geometric model is a planar circle model. When the positional feature includes three references and the drawing annotation element is a single deep hole, the theoretical geometric model is a cylindrical model. When the positional characteristics include one or two datums, and the drawing annotation elements are a set of circumferentially distributed holes, the theoretical geometric model is a rotary shaft type model. When the theoretical geometric model is a planar circular model, the mathematical formula is: Where D is the positional tolerance value; When the theoretical geometric model is a cylindrical model, the mathematical formula is: Where D is the positional tolerance value, and no less than two sets of data are measured in the reference direction perpendicular to the hole; When the theoretical geometric model is a rotation axis type model, the mathematical formula is: Where D is the positional tolerance value. In step S3, if the ratio of the nominal values ​​of the two coordinate dimensions is between 1 and 1.2, proceed to step S4; if the ratio of the nominal values ​​of the two coordinate dimensions is greater than 1.2, proceed to step S5.

2. The calculation method for converting positional tolerance into coordinate dimension tolerance according to claim 1, characterized in that, In S2, determining the theoretically correct size of the positional accuracy includes the coordinate dimensions marked with a box starting from the reference plane as the theoretically correct size.

3. The calculation method for converting positional tolerance into coordinate dimension tolerance according to claim 1, characterized in that, S4 obtains the coordinate dimension tolerance according to the following table: 。 4. The calculation method for converting positional tolerance into coordinate dimension tolerance according to claim 1, characterized in that, S6 includes: selecting the actual value of the coordinate dimension, using the idea of ​​infinite approximation to change the criterion from qualified to unqualified, and then changing the criterion from unqualified to qualified, to find the actual value that is closest to the critical maximum value. The difference between the actual value and the theoretically correct dimension is the one-sided deviation of the coordinate dimension tolerance.

5. The calculation method for converting positional tolerance into coordinate dimension tolerance according to claim 4, characterized in that, During the trial selection process, more tolerance can be assigned to those with larger nominal values, and less tolerance can be assigned to those with smaller nominal dimensions.

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