Redesign of a Single Screw Extruder Project Number: SYS 0088 A Major Qualifying Project Report Submitted to the Faculty of the WORCESTER POLYTECHNIC INSTITUTE in partial fulfillment of the requirements for the Degree of Bachelor of Science In Mechanical Engineering By John Kreso Stephen Jenkinson Date: April 25, 2012 Approved: 1. extruder redesign Professor Satya Shivkumar, Major Advisor 2. plastic 3. single screw This report represents work of WPI undergraduate students submitted to the faculty as evidence of a degree requirement. WPI routinely publishes these reports on its web site without editorial or peer review. For more information about the projects program at WPI, see http://www.wpi.edu/Academics/Project ABSTRACT This project involved the redesign of a two decade old single screw plastic extruder. Diagnostics and troubleshooting revealed a malfunction in the motor controller resulting in motor failure. The specifications for a new motor controller were developed that can make the machine fully operational. Design and construction of a cooling system was also needed to maintain the structure of the extruded molten plastic as it exits the die. i Table of Contents ABSTRACT ................................................................................................................................................... i Table of Figures ........................................................................................................................................... iv Introduction ................................................................................................................................................... 1 Background ................................................................................................................................................... 3 History ...................................................................................................................................................... 3 Types of Extrusion .................................................................................................................................... 3 Types of Extruders .................................................................................................................................... 4 Types of screws......................................................................................................................................... 5 Basic screw design: ............................................................................................................................... 5 Barrier Screws: ...................................................................................................................................... 6 Mixing Screws: ..................................................................................................................................... 6 Objectives ..................................................................................................................................................... 7 Overall Methodology .................................................................................................................................... 8 Methodology ............................................................................................................................................... 11 Power ...................................................................................................................................................... 11 Motor Not Turning .................................................................................................................................. 11 Screw Removal ....................................................................................................................................... 13 Cleaning the Screw ................................................................................................................................. 14 High Torque Levels/Blown Fuse ............................................................................................................ 15 Missing Parts ........................................................................................................................................... 16 Problems with Screw Key ....................................................................................................................... 18 Necessity for Water Bath ........................................................................................................................ 19 Technical Appointments ............................................................................................................................. 20 New England Plastics ............................................................................................................................. 20 University of Massachusetts Lowell ....................................................................................................... 21 Design of Cooling System .......................................................................................................................... 28 Background ............................................................................................................................................. 28 Initial Design ........................................................................................................................................... 29 Prototype ................................................................................................................................................. 29 Future and Complete Design .................................................................................................................. 31 Summary ..................................................................................................................................................... 33 References ................................................................................................................................................... 34 ii Appendices .................................................................................................................................................. 35 Appendix A ............................................................................................................................................. 35 Appendix B ............................................................................................................................................. 41 iii Table of Figures Figure 1 Single Screw Figure 2 Twin Screw........................................................................................... 4 Figure 3 Typical Screw ................................................................................................................................. 5 Figure 4 Conventional Barrier Screw ........................................................................................................... 6 Figure 5 Gear Box ......................................................................................................................................... 8 Figure 6 New Outlet ...................................................................................................................................... 9 Figure 7 220 Volt 30 Amp Power Plug ....................................................................................................... 11 Figure 8 Unattached Motor ......................................................................................................................... 12 Figure 9 Screw Removed ............................................................................................................................ 13 Figure 10 Dirty Screw ................................................................................................................................. 14 Figure 11 Clean Screw ................................................................................................................................ 14 Figure 12 Motor Controller ......................................................................................................................... 16 Figure 14 Bung Attached to Barrel ............................................................................................................. 17 Figure 13 Thermocouple Bung ................................................................................................................... 17 Figure 15 Nonfunctional Speed Gage Figure 16 Missing Gasket for Speed Gage ................................. 18 Figure 17 Screw Key .................................................................................................................................. 18 Figure 18 Sagging Molten Plastic From Die .............................................................................................. 19 Figure 19 Close-up of Die ........................................................................................................................... 20 Figure 20 Removed Die from Die Plate ...................................................................................................... 23 Figure 21 Pressure Transducer .................................................................................................................... 24 Figure 22 Our Manual Adjustable Temperature Figure 23 Umass Digital Adjustable Temperature .... 25 Figure 24 Resin Close up Figure 25 Bag of Polypropylene Received .................................................