Datum-Hierarchy Tree Method for Tolerance Analysis of Plating and Heat Treatment Operations

This paper presents a new method for the tolerance analysis of plating and heat treatment operations. It is suitable for both manual and computerised tolerance analysis. The new method uses a datum-hierarchy tree to identify tolerance stacks and a stock removal set matrix to calculate the positions of surfaces created during the manufacturing sequence. A tolerance chart is used to associate stock removal sets with the geometry of the workpiece, to show the manufacturing sequence, and to record the operation data and the tolerance analysis results. Plating and heat treatment operations are represented as edges in the tree, so that for each operation (edge) the input and output nodes represent consecutive surfaces in a stock removal set. Rules are given for calculating the tolerance stackups and the positions of the surfaces in the stock removal sets. The method is illustrated with an example.