Combining variation simulation with thermal expansion for geometry assurance

In every set of assembled products there are geometrical variation and deviations from nominal dimensions. This can lead to products that are difficult to assemble or products not fulfilling functional or aesthetical requirements. In several industries variation simulation is used to predict assembly variation in the development phase. This analysis is usually done under the condition of room temperature only. However, for some materials, such as plastics, the thermal expansion can be significant in the intended environmental span of the product. In an assembly, this can lead to thermal stresses and parts that will deform. To avoid this problem, locating schemes need to be designed to allow for the right behavior while exposed to varying temperatures. In this work the effect of thermal expansion is studied in the context of variation simulation. A virtual tool for this end is also presented. An example from the automotive industry is used where the combined effect of th ermal expansion and assembly variation is analyzed. It is shown that it may not be sufficient to simply add the result from thermal analysis to assembly variation. Hence, to assure the geometrical and functional quality of assembled products, during its use, variation simulations need to be combined with thermal stresses