Project Examples

Design of Experiments for Plastic Windshield Scraper Molding

Course: 22.473 - Design Theory and Constraints
Semester: Fall 2005
Instructor: Sammy Shina
Partner:Plastics Department Outreach Program

Partnership Description: The Plastic Engineering Department was interested in the application of statistical methods for improving quality and reducing cost for plastic injection molded parts. Ice-scrapers are manufactured in the plastics engineering molding lab during demonstrations for visitors and distributed as giveaways to promote the application of STEM education. A collaborative effort was made between the mechanical and plastics faculty with the goal of manufacturing plastic parts of higher quality and lower cost using statistical techniques.

Project Description: Optimization of Plastic Injection Molding Design and Manufacturing. Four students in the Design Theory and Constraints (Mech. Eng.) course used the techniques of Design of Experiments (DoE) to improve the design and manufacture of plastic injection molded parts for higher quality and tighter tolerances for the Plastics department outreach program. Concepts of world-class design and manufacturing of modern products, including the issues of Design for Quality (DFQ), cost and the customer were studied. Tools and techniques studied included Total Quality Management (TQM), statistical process control, process capability studies, six sigma quality, design efficiency ratings, design for cost, design of experiments, Analysis of Variance (ANOVA) of the mean and signal-to-noise ratio, and quality function deployment. Industrial case studies were used and student project work was required.

Learning objectives met by the S-L project:

  • Practice technical communication skills by having the students produce a final report and presentations to other students in class using Microsoft office tools (Word, Excel, PowerPoint, Project).
  • Opportunity for professional teamwork, working with other students from a different discipline (plastics), project management and using statistical techniques for improving quality and cost for design and manufacturing.
  • Apply engineering and design ethical standards in design, taking data, analysis and performing their duties as prescribed
  • Develop and exercise safe practices in making modern plastic injection molding machines work at optimum safety.
  • Learn about the multi-disciplinary issues of plastics injection molding, as well as plastics material properties and cost analysis
  • Explore codes used by industry in the design and manufacture of high technology and plastics products, as well as safety and environmental codes.

Community objectives met by the S-L project:

  • A plan for designing and conducting a set of experiments to improve the quality and lower the cost of plastic injection molding parts, as well as the software needed to analyze them
  • Assist in the advancement and interest of high school students, parents and other outside groups in Math, Science and Engineering careers and topics.

Professor Sammy Shina reported that the “students were motivated for the project and undertook several discussions with the plastics engineering department in order to understand the issues of plastic injection molding…I enjoyed working with this student team, and discussing issues outside of the mechanical engineering topics. I related my own experience in using the statistical techniques to improve plastic engineering parts, especially working with the Parker Brothers Company to design and implement the whistling “Nerf” ball.” Unfortunately, no parts actual were produced but there is still hope that the study results will be used in the future. “Poor communication” between the departments, including the defining of goals and the delegation of responsibilities, was cited as the chief barrier to be overcome. Professor Shina suggested “better initial preparation and coordination with the plastics department, and making sure to identify the responsible authority in the department to make the proper timely decisions and to coordinate all activities and access to the injection molding machines. I am prepared to do a better job next time (Fall 2006), especially with the appointment of the SLICE coordinator, Linda Barrington, and to work with her on organizing and communicating with the Plastics Engineering department personnel.”