Tolerance Stack-up Analysis

A stack-up analysis is an engineering method used to verify the dimensions presented in an engineering drawing. Due to limitations of manufacturing processes, engineers need to set allowable tolerances that will allow the product to function properly, regardless of worst-case scenario part manufacturing.

Importance
A stack-up analysis estimates a component's dimensions during a statistical worst-case scenario. Take, for example, a shaft and its corresponding hole. If the tolerances are set incorrectly, then there could be a scenario where the shaft diameter will be larger than the hole diameter, and the two components will not be able to be assembled. On the other side of the spectrum, there could be a scenario where the shaft has too much clearance inside the hole, and the component may not function correctly.

Methodology
Add up the extremes of each tolerance and determine whether or not the targeted component can still function properly under worst case scenario. See the video to the right of this page for a demonstration.