Statistical tolerance analysis is useful for high-volume production where a small percentage of scrap is acceptable, as long as the majority of parts fall within the allowable tolerance range. There are a number of different statistical tolerance analysis methods, such as the Monte Carlo method and root sum square (RSS). This combines all the probabilities of the different dimensions - meaning the likelihood of each dimension being above or below its ideal value by a given amount- to determine the part’s chances of failure or success. Worst-case tolerance analysis should be used when mating parts are absolutely critical and there is little chance for rework or design modification once production has started. Then, compare the total tolerance to the part’s performance limits in order to ensure proper design.
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Both the upper and lower limits should be evaluated to provide a full picture of the allowable tolerance range. When performing worst-case tolerance analysis, you should set each tolerance to either the largest or smallest value in its range. This involves adding up all of the individual tolerances of a part or assembly to find the total sum. There are two main kinds of tolerance stack analysis: Worst-case tolerance analysis Calculating tolerance stack-up can also save you money by helping you understand your tolerances in context, so you can optimize for cost and manufacturability. This prevents you from having to go back to the design process after moving to the prototyping or production stages, which can save time, money, and resources. Proper tolerance stack analysis also enables you to predict how your final component will look, function, and interact with other components - this is particularly important when it comes to manufacturing mating parts.Īccounting for tolerance stack-up helps ensure tolerances can be manufactured before manufacturing even begins. This tells you the total amount a part can differ from specified dimensions. Final results from a tolerance stack are compared to tolerancing standards, regulations, and other limits in order to ensure the part design will produce high-quality components. Tolerance stack-up is the process of adding tolerances together before manufacturing in order to understand their cumulative effect on part production.