What VarTran Does

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What VarTran Does
VarTranŽ is both a tolerance analysis package and a robust design package that can be used on both products and processes. It can be used to set targets and tolerances on the inputs that ensure the outputs meet their specifications at the lowest possible cost. This is accomplished in two steps. First, starting with the low cost tolerances on the inputs, the optimal targets for the inputs are identified. The effects of the input's targets on both the output's average and variation are considered when finding the optimal targets. This reduces the variation of the outputs resulting in what Taguchi calls a robust design. The second step is to tighten the input's tolerances to achieve the desired performance. The trick is to only tighten those tolerances necessary and only to the degree necessary to meet the customer requirements. The result is high quality and low cost.
In order to set targets and tolerances for the inputs, you first have to identify the output variables that you want to control. Next, you need to identify the input variables that affect these outputs. Finally, you must gather the following information about these variables:
(1) The target and specification limits for the output variables. These represent the customer requirements.
(2) An initial target and tolerances for each of the input variables. These can be obtained by performing capability studies on the inputs. This information describes how the inputs behave.
(3) Equations describing the effects of the inputs on the outputs. In some cases these equations might be derived or might be readily available in books or articles. However, in other cases, designed experiments will be necessary to empirically fit equations. This information describes how the inputs affect the outputs.
Knowing how the inputs behave and how the inputs affect the outputs allows one to predict how the outputs will behave. One method of predicting the behavior of the outputs is to perform a simulation. While VarTran can perform such simulations, it is also capable of much more powerful analytic methods. Analytic methods allow alternate designs to be quickly evaluated and the optimal design selected. Simulation is generally limited to evaluating the current design only.
For further information, see Getting Started and VarTran's Capabilities.