Reference Free Part Encapsulation (RFPE) is an automatic, universal workholding process in which a block of filler material encapsulates the workpiece and provides a fixturing surface, and after each machining operation, the filler block is re-filled with material to restore it to a perfect block. We examine the effect of process parameters such as the injection temperature, and the preheating temperature on the effectiveness of the process. e show that when the temperatures are too low, or if the mold is cooled too much or too rapidly, the newly added material does not weld properly to the original encapsulation. If the temperatures are too great, then the entire encapsulation is likely to melt and lose location. We develop models to understand the effects of these parameters on process performance and design experiments to verify these predictions. Using these techniques, we determine the acceptable parameter windows for the process.