Reference Free Part Encapsulation (RFPE): An investigation of material properties and the role of RFPE in a taxonomy of fixturing systems

Abstract The Reference Free Part Encapsulation (RFPE) method is a workholding system designed to “free up” the design space and greatly expand the possible range of parts that can be designed and then machined. Despite the increased capability of the RFPE technique, part warpage and debonding during RFPE have not yet been sufficiently documented. To address these problems, a set of experiments was conducted. The first test was designed to find a RFPE fixturing material with preferred thermomechanical properties for a given workpiece. Three different groups of materials were tested: (1) fusible alloys such as BiSn and BiSnZn, (2) thermoplastic polymers called Rigidax®, and (3) fixturing waxes. In the second test, the effect of preheating the workpiece for better interfacial shear strength and the effect of adding aluminum powders to the WI-Green Rigidax were examined. These processing conditions and composite materials allow manufacturing engineers to design, process plan, and fixture parts of complex geometrical shapes. A taxonomy of various fixturing systems is presented in this paper to describe the characteristics of RFPE relative to other fixturing methods.