Date of Award


Degree Name

Master of Science


Industrial and Entrepreneurial Engineering and Engineering Management


Industrial and Manufacturing Engineering

First Advisor

Dr. Paul Engelmann

Second Advisor

Mike Monfore

Third Advisor

Dr. David Lyth

Fourth Advisor

Dr. Mitchel Keil

Access Setting

Masters Thesis-Open Access


A mounting demand for high quality, low cost plastic injection molded products brings with it goals such as low or even zero defects. In order to achieve these types of "world class" expectations, resources are used to monitor and control variable data such as cycle time, part weight or dimensions. Despite this emphasis on variable data, parts are often rejected based on attribute molding defects such as sink marks or splay that are measured by subjective criteria and therefore difficult to control. Appearance of a part once considered acceptable may no longer be, due to changing expectations or subjective interpretation of an agreed upon standard.

Sink marks on each part were measured using a coordinate measurement machine (CMM) and quantified using statistical software. Experimentation was conducted to identify the level at which a majority of human observers were not able to visually perceive the sink marks. This threshold could be used to develop an acceptance standard for the part used in the experimentation. Quantifying an attribute defect is not intended to be a substitute for preventing defect formation via robust part design, mold design, choice of polymer, or selection of processing conditions.