Tolerance Stack-Up Analysis

This course is designed for engineers and others who need to understand stack calculations for piece parts and/or assemblies. Participants will learn a methodical approach to performing stacks that avoids many common mistakes. The course focuses on the main steps involved in calculating a stack: identify the problem, determine the stack path, transfer the dimensions to a spreadsheet, and calculate the answer. While the first several examples exclusively use traditional plus/minus examples, most of the course shows stacks using GD&T on prints. Many practice exercises using the worst-case approach will be done to reinforce the concepts. The course concludes with an overview of several statistical approaches to stacks.

Class Details

Class Name:
Tolerance Stack-Up Analysis
Intended for product designers, product engineers, manufacturing engineers and others who create or assess designs. Ideally, participants should already have familiarity with the rules and concepts of GD&T per the ASME Y14.5 standard.
2 Day Course

Learning Objectives

  • Calculate virtual condition and resultant condition for simple stacks of clearance and wall thickness.
  • Identify the stack path (or loop) for a given stack problem in a single part or in an assembly.
  • Correctly transfer dimensions and tolerances to a spreadsheet for calculation.
  • Calculate worst-case maximum and minimum for a given stack problem.
  • Explain which geometric tolerances need to be factored into a stack.
  • Correctly enter GD&T information into the spreadsheet.
  • Determine how to include bonus and shift tolerance in a stack.
  • Describe two statistical methods that may be employed when calculating a stack, and the necessary prerequisites for these methods to be useful.

Outline At-a-Glance

  • Why stacks are important
  • How tolerance values may be determined
  • Review of geometric dimensioning and tolerancing
  • Calculating virtual condition and resultant condition
  • The importance of datums
  • The four basic steps in calculating a stack
  • Overview of the stack spreadsheet
  • Stack-up example on a single part, using coordinate tolerances
  • Stack-up example on assemblies, using coordinate tolerances
  • How to factor in concentricity, runout, and position
  • Profile tolerances in a stack (bilateral and unilateral)
  • Form and orientation tolerances in a stack
  • Advanced topic: stacks that include "bonus" and "shift" tolerances
  • Statistical stacks: root-sum-square, the Bender formula, and Monte Carlo simulation

Job Roles