In addition to "English", the international common language, there is another thing that your friends may not know, that is, "shape and position tolerance", which is an international "language" that runs through manufacturing design, production, quality management and other departments.
"The gap between ideal and reality"
As long as the product is made by us, no matter how sophisticated equipment is used, no matter how much effort is made, its size and shape cannot fully meet the theoretical numerical requirements.
So how much can it be close to the theoretical shape and position? We use numerical values to express the degree of similarity, which are shape tolerances and position tolerances, referred to as "shape and position tolerances".
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Understand 14 geometric tolerances in one article, it is the password to crack the machine
When designing, the shape and position tolerance of the parts must be marked on the drawing in accordance with the prescribed standard symbols to convey information.
Standardization of form and position tolerances
With the development of globalization, the international division of labor and cooperation in the field of production continues to deepen. However, there are difficulties in interconnection between countries and different production habits. How to solve the problem of improving production accuracy and ensuring interchangeability to reduce costs? The international standards for form and position tolerances urgently need to be unified.
1950: Industrialized countries put forward the "ABC Proposal" to the ISO organization to unify the concept of form and position tolerance and the method of text representation.
1969: The ISO organization officially released the form and position tolerance standard ISO/R1101-Ⅰ:
1969: "Shape and Position Tolerance Part I: Introduction, Symbols, and Graphic Representation."
1978~1980: The ISO organization recommended the principle and method of shape and position tolerance testing; China formally rejoined the ISO organization and promulgated the basic standard of shape and position tolerance in 1980.
1996: The ISO organization established a special ISO/TC213 "Geometric Technical Specification for Products (GPS)" Technical Committee, responsible for the international unification of geometric tolerances and drawing symbols.
After the long-term joint efforts of many countries, we finally have this international unified 14-item tolerance symbol. Here, it is the following table, hurry up and collect it~
Shape tolerance
01 Straightness
Straightness, which is commonly referred to as the degree of straightness, indicates that the actual shape of the linear elements on the part maintains an ideal straight line. Straightness tolerance is the maximum amount of variation allowed by the actual line to the ideal straight line.
▲Pattern example 1: In a given plane, the tolerance zone must be in the area between two parallel straight lines with a distance of 0.1mm.
▲Pattern example 2: Add the mark φ before the tolerance value, the tolerance zone must be within the area of the cylindrical surface with a diameter of 0.08mm.
02 Flatness
Flatness, which is commonly referred to as the degree of flatness, represents the actual shape of the flat elements of the part and maintains an ideal flat surface. The flatness tolerance is the maximum allowable variation of the actual surface from the ideal plane.
▲Pattern example: The tolerance zone is the area between two parallel planes with a distance of 0.08mm.
03 roundness
Roundness, which is commonly referred to as the degree of roundness, indicates that the actual shape of the circle element on the part is kept equidistant from its center. The roundness tolerance is the maximum variation allowed by the actual circle to the ideal circle on the same section.
▲Pattern example: The tolerance zone must be on the same cross-section, and the radius difference is the area between two concentric circles with a tolerance value of 0.03mm.
04 Cylindricity
Cylindricity refers to the points on the contour of the cylindrical surface of the part, and its axis is kept equidistant. The cylindricity tolerance is the maximum allowable variation of the actual cylindrical surface to the ideal cylindrical surface.
▲Pattern example: The tolerance zone is the area between two coaxial cylindrical surfaces with a radius difference of 0.1mm.
Outline tolerance
05 Line profile
Line profile is the condition that a curve of any shape on a given plane of a part maintains its ideal shape. Line profile tolerance refers to the allowable variation of the actual contour line of a non-circular curve.
▲Pattern example: the tolerance zone is the area between two envelopes that envelop a series of circles with a tolerance of 0.04mm in diameter. The centers of the circles are located on a line with a theoretically correct geometric shape.
06 Face profile
The surface profile is the condition that the curved surface of any shape on the part maintains its ideal shape. Surface profile tolerance refers to the actual contour line of the non-circular curved surface, and the allowable amount of change to the ideal contour surface.
▲Pattern example: The tolerance zone is between two envelopes that envelop a series of balls with a diameter of 0.02mm. The center of the balls should theoretically be located on the surface of the theoretically correct geometric shape.
Orientation tolerance
07 Parallelism
Parallelism, which is commonly referred to as the degree of parallelism, indicates that the actual elements of the part being measured are kept equidistant from the reference. Parallelism tolerance is the maximum amount of variation allowed between the actual direction of the measured element and the ideal direction parallel to the reference.
▲Pattern example: If the mark φ is added before the tolerance value, the tolerance zone is the reference parallel inside a cylindrical surface with a diameter of φ0.03mm.
08 Verticality
Perpendicularity, that is, the degree of orthogonality between the two elements that is commonly referred to, indicates that the measured element on the part maintains the correct 90° angle with respect to the reference element. Perpendicularity tolerance is the maximum amount of variation allowed between the actual direction of the measured element and the ideal direction perpendicular to the reference.
▲Explanation of legend: Add the mark φ before the tolerance zone, and the tolerance zone is perpendicular to the cylindrical surface with the reference surface diameter of 0.1mm.
▲Legend description: The tolerance zone must be located between two parallel planes with a distance of 0.08mm and perpendicular to the reference line.
09 Inclination
Inclination is the correct condition that the relative direction of two elements on the part maintains any given angle. The inclination tolerance is the maximum amount of variation allowed between the actual direction of the measured element and the ideal direction at any given angle to the datum.
▲Legend explanation: The tolerance zone of the measured axis is the area between two parallel planes with a distance of 0.08mm and a theoretical angle of 60° with the reference plane A.
▲Explanation of legend: Add the mark φ before the tolerance value, and the tolerance zone must be located in a cylindrical surface with a diameter of 0.1mm. The tolerance zone should be parallel to the plane B perpendicular to the datum A, and at a theoretically correct angle of 60° to the datum A.
Positioning tolerance
10 degree of position
The position degree indicates the accuracy of the points, lines, areas and other elements on the part relative to their ideal positions. The position tolerance is the maximum allowable variation of the actual position of the measured element relative to the ideal position.
▲Explanation of legend: When the mark Sφ is added in front of the tolerance zone, the tolerance zone is the area within the ball with a diameter of 0.3mm. The position of the center point of the ball tolerance zone is the theoretically correct size relative to the reference A, B and C.
11 Coaxial (concentric) degrees
Coaxiality, which is commonly referred to as the degree of coaxiality, indicates the condition that the measured axis of the part is kept on the same straight line with respect to the reference axis. Coaxiality tolerance is the allowable variation of the measured actual axis relative to the reference axis.
▲Legend of coaxiality tolerance: When the tolerance value is marked, the tolerance zone is the area between cylinders with a diameter of 0.08mm. The axis of the circular tolerance zone is consistent with the datum.
12 Symmetry
Symmetry refers to the state that the two symmetrical central elements on the part remain in the same central plane. Symmetry tolerance is the allowable variation of the symmetry center plane (or center line, axis) of the actual element to the ideal symmetry plane.
▲Legend description: The tolerance zone is the area between two parallel planes or straight lines that are 0.08mm apart and symmetrically arranged with respect to the reference center plane or center line.
Jumping tolerance
13 circle beat
Circular runout means that the revolving surface on the part maintains a fixed position relative to the reference axis within a defined measurement plane. The circle runout tolerance is the maximum amount of variation allowed within the limited measurement range when the actual element to be measured rotates a full circle around the reference axis without axial movement.
▲Legend explanation 1: The tolerance zone is the area between two concentric circles perpendicular to any measurement plane, with a radius difference of 0.1mm, and the center of the circle on the same reference axis.
▲Legend explanation 2: The tolerance zone is the area between two circles with a distance of 0.1mm on the measuring cylinder at any radial position coaxial with the reference.
14 Full beat
Full runout refers to the amount of runout along the entire measured surface when the part rotates continuously around the reference axis. The total runout tolerance is the maximum runout allowed when the measured actual element rotates continuously around the reference axis while the indicator moves relative to its ideal contour.
▲Legend description 1: Tolerance zone is the area between two cylindrical surfaces whose distance is 0.1mm in radius difference and is coaxial with the reference.
▲Legend description 2: Tolerance zone is the area between two parallel planes with a distance of 0.1mm in radius difference and perpendicular to the reference.
