Accuracy rationing coursework

Contents

Contents

Introduction

Assembly unit description

Defining Gaps and Interference in a Smooth Cylindrical Joint

Calculation of limit gauges

Calculation and selection of joint fits with rolling bearings

Calculation of threaded joint fits

Calculation and selection of fits on splined joints with straight and involute profile

Conclusion

List of literature

Introduction

The performance of mechanisms and machines (durability, reliability, accuracy, etc.) largely depends on the correct selection of fits, tolerances of shape and location, surface roughness. In an assembled product, parts are connected to each other, and deviations in the dimensions, shape, and arrangement of axes or surfaces of one of the parts cause deviations in other parts. These deviations, summing up, affect the performance of machines and mechanisms.

The complex of deep knowledge and certain skills in the field of ensuring the specified quality of products, using advanced methods of optimizing parameters and requirements for accuracy, are a necessary integral part of the professional training of specialists in mechanical engineering, metrology, standardization and other professions.

Due to a number of reasons, the geometric shape of the parts cannot be withstood during manufacture. All these errors of shape, mutual arrangement, as well as surface roughness affect operational (wear, noise, strength, tightness, etc.) and technological (labor intensity of processing, assembly, control, cost) indicators. Therefore, surface feature and location deviations must be limited to tolerances. The main regulatory requirements for the tolerances of the shape and arrangement of surfaces are reflected in the state standards, and the instructions on the drawings are fulfilled in accordance with the ESKD requirement as per GOST 2.308.

For each tolerance type, 16 degrees of accuracy are set in the order in which the tolerance value increases.

Surface Shape Deviations

A shape deviation is a deviation of the shape of a real surface or a real profile from the shape of a nominal surface or a nominal profile.

Quantitative deviation of the shape is estimated by the largest distance A from the points of the real surface (profile) along the normal within the normalized section L.

GOST 2464381 provides for five types of shape deviations: from rectilinearity; from flatness for planar surfaces; from cylinders; from roundness; from the profile of the longitudinal section for cylindrical surfaces.

Surface Location Deviations

Surface Location Deviation - Deviates the actual location of the part feature in question from its nominal location. The nominal position of the element is determined by the nominal linear and angular dimensions between it and the bases or between the elements in question, if no bases are specified.

The standard establishes seven types of surface location deviations: from parallelism; from perpendicular; inclination; from coaxiality; from symmetry; positional; from the intersection of axes.

Conclusion

As a result of the work done, theoretical material was studied, as well as practical tasks were completed on the following topics:

Tolerances and fits of smooth cylindrical joints.

Selection of measuring instruments.

Calculation and design of limit gauges for connection control.

Normalizes the accuracy of the part included in the assembly.

As a result of completing the tasks, he learned to work with standards, mastered the methods of normalizing the accuracy of connection of various types.