Three Dimensional Accuracy Control Variation Merging Equations

摘要

The use of variation merging equations is an established method for predicting the final variation in specific critical dimensions of a ship's hull block. To predict over-all rework requirements at a block interface, however, it is necessary first to write a set of merging equations for each edge at the interface, and then to evaluate the total effect produced by the combined interaction of all the edge variations within a 3-dimensional framework. Writing a full set of merging equations for an interface begins with choosing a datum to serve as a common origin for the equations. It is also necessary to recognize when variations occur independently and when the variation of certain edges is, to some degree, related. These and other factors influence the correct composition of the equations. The complex interaction of all the edge's random variations at the block interface gives rise to a unique rework probability distribution. The probability distribution is evaluated by means of a computer simulation program, which provides estimates of the average rework anticipated, the shape of the distribution curve, and other parameters. In addition to predicting rework levels, the simulation program can be a useful tool for reducing those levels.