Utilizing Measurement Tools to Develop a Shrink Rule for the 3-D Printing Process

Rapid prototyping, in particular 3-D printing, has quickly grown to be a critical part of the design, inspect, and evaluate process involved in product design. Parts of moderate size may be 3-D printed using various plastic materials like Acrylonitrile Butadiene Styrene (ABS) and nylon, which have quickly replaced the powder-based 3-D printers. These plastic processes utilize relatively inexpensive printers and materials and their popularity has soared as a result. The Purdue Polytechnic campus in Columbus, Indiana, now employs five 3-D printers to supplement its mechanical design, inspection, and validation instruction by also using the tools and resources of an environmentally-controlled metrology lab. The objective of this study is to design, print, and measure various part geometries to determine how closely the 3D printed part dimensions are to the original design. 3D printed parts do shrink as they cool following the printing process. In essence, this is very similar to shrinkage that occurs during the metal casting process and so the goal is identify and create a "shrink rule" for 3D printed plastic parts. There are multiple variables involved in the process including material, nozzle speed of the 3D printer, resolution of the printer, and size of the part among others. These different variables are explored in this study to determine the optimal process for accurate and repeatable 3D printing. A Zeiss Duramax coordinate measuring machine is utilized to perform the dimensional measurements of the parts. Various part orientations on the CMM are also investigated to determine any sensitivity to the measurement process. Results will demonstrate that parts need to be scaled up by 1.1% to 1.3% to accurately account for shrinkage of the material.