Faculty Advisor

Moon, Yong-Mo


The goal of our project was to design and build a prototype of a control mechanism for an automated spot welder, for use by Gillette. The previous welding system involved a laser spot welder that produced a stationary spot on the moving parts. This method caused problems because the weld was smeared over the moving parts, resulting in a weak weld with a large heat affected zone. The goal was to design a device that allowed the laser light to track the moving part, which would essentially create a static weld on the part. Six alternate designs were compared by the conceptual design evaluation method. These ideas were presented to Gillette, and one was chosen to build. The design that was chosen included a mirror and lens system that is mounted on a flexure joint. The flexure joint is moved by a CAM in a manner which redirects the focused laser light to the moving parts. The device has a long life, is cost effective, and is capable of producing 200 parts per minute (over 40 welds per second). The design process of the compliant joint in the mechanism allows us to tune the target vibration frequency to maximize the vibration robustness of the machine. A prototype was built in ProE-Wildfire to verify the design principles. This prototype of the system was then built to test the design concepts, and to determine if the application of flexure joints in a manufacturing environment is practical.


Worcester Polytechnic Institute

Date Accepted

January 2004


Mechanical Engineering

Project Type

Major Qualifying Project


Restricted-WPI community only

Advisor Department

Mechanical Engineering