FRP GRINDER GUARDDESIGN PROJECT

Abstract

Carfair Composite is a division of New Flyer Industries Group Inc. and manufacturer of Fiber-Reinforced Plastics (FRP) and composites. Operators at Carfair are using an AP10-4 Diatrim 4-inch fiberglass grinder from Applifast suppliers to trim the manufactured parts to the correct final dimensions which are marked by scribe lines on the fiberglass parts. The hand grinders are supplied with a guard to protect the operator from the fast-moving diamond cutting blade. The guards provided are bulky and opaque which greatly reduces the operators’ visibility when making cuts and inhibits them from trimming the parts to the allowable tolerance of 0.03inches.To circumvent this issue, the operators have removed the grinder guards throughout Carfair’s facilities, resulting in high cut accuracy but introducing safety hazards. The project objective was to design a custom guard for the 4-inchpneumatic hand grinders to protect the operator from the cutting blade while allowing them to maintain a high cut accuracy to the specified tolerance. Six preliminary concept guard designs were generated and presented to the client. The client opted to move forward with the Retractable Guard design, which reflected the team’s concept selection analysis. The Retractable Guard design assembly consists of 11 custom parts and 15 different types or hardware supplied by McMaster-Carr. The design of the guard consists of a two-piece main guard body and two three-piece pivot guard assemblies. The design allows the guard to open and close, exposing approximately 40% of the cutting edge of the blade when open, which reduces to 25% in the closed resting position. The motion of the pivot guards is restricted by arc slots on the main body of the guard. Furthermore, torsional springs apply a torque to the pivot guards, ensuring that the guard remains closed when a cut is not being made. The pivot guards house scribe line guides which protrude in front of the blade when the guard is in its resting position. The guides have a fine tip, 0.03 inches thick, which fits into the scribe lines which are approximately 0.06 inches wide. When the grinder is pushed against the work piece, the two pivot...