Predicting the reference length of polymer parts with micrometer uncertainty measured under non-reference conditions

Today, dimensional validation of polymer parts with micrometer level accuracy is performed long time after production because the part needs time to “settle” (which for some polymer materials takes weeks). However, manufacturing industry requires the measurements to be performed before part stabilization, to reduce the waiting time for quality control without compromising the level of accuracy. This work proposes an analytical solution for predicting the reference length of a classical 32 mm polymer part with an uncertainty of less than 10 μm when measured at non-reference conditions. Creep, moisture uptake and temperature are here the main issues to consider for polymer parts. The present study focuses on the dimensional changes governed by moisture uptake and creep with model parameters separately obtained by experimental studies combined with numerical simulations. Finally, the obtained analytical solution is used to predict the reference length of stabilized and non-stabilized polymer parts measured continuously over two months. The prediction shows good agreement with the reference values for settled parts at reference conditions.