Improving Surface Finish Quality of Rapid Tooling via Surface Contact Infiltration of 3-D Printed Metal Parts

Solid freeform fabrication technology has shown a great deal of promise for the plastic injection molding industry due to its ability to produce complex geometry tooling relatively quickly. However, one shortcoming of metal-based SFF processes is that they have difficulty producing parts with acceptable surface quality. As such, secondary operations, such as machining, are frequently required thereby increasing fabrication time and cost. In addition, there is variation in the surface quality that is dependent upon the surface orientation during the build process. For example, parts produced using the metal-based 3-D printing process have vertical faces with a typical roughness 52% greater than the horizontal faces. This work investigates the effects on part surface quality resulting from the application of a contact surface "blank" to the part free surfaces during the infiltration stage of a powder metalbased rapid manufacturing process. Specifically, the effects of "blank" surface roughness and contact pressure are studied with respect to resultant surface roughness and uniformity of the infiltrated part. Application of a smooth contact surface on vertical faces resulted in R_a values at least 25% lower than that of vertical free surfaces. It was also revealed that there is a correlation between surface roughness of the blank and the surface roughness of the infiltrated part. Such blanks could be used to impart desired surface finish and texture to critical surfaces of a mold tool.