Tolerance Analysis

It is impossible to produce parts conforming precisely to the nominal (ideal) dimensions. A variety of physical limitations on manufacturing processes (such like cutting conditions, skills of machine operators, hardware accuracy, etc.), as well as material properties, contribute to limiting the precision with which we can manufacture parts. To account for this variability of dimensions, we assign a tolerance at the design phase or a range of acceptable values to needed (not every dimension needs a tolerance) dimension of the part. If a part size and shape are not within the minimum and maximum dimensional limits defined by the part tolerances, the part is not acceptable. The assignment of real values to the tolerance limits has a major effect on the overall cost and quality of an assembly or a product. If the tolerances are too small (tight), the individual parts shall cost more to manufacture. If the tolerances are too wide (loose), a large percentage of assemblies might be scrapped (rejected) or would require rework.

Objectives

After studying this unit, you should be able to

• Understand the different types of tolerances,
• Use the concept tolerance and cost relation while designing a product,
• Apply the concept of tolerances,
• Know the importance of tolerance analysis.