US EPA

2066267 

Technical Report 

Aluminum Extrusion Sawing Noise Reduction 

Stewart, JS 

1984 

NIOSH/00178266 

I 

3-5 

Noise reduction in aluminum extrusion sawing was studied. The three most important noise sources of the circular saw were aerodynamic noise, blade vibration noise, and vibration of the workpiece. The results of frequency analysis showed that extrusion vibration noise was the most important source during sawing, followed by blade vibration noise. The primary variables in the study were blade tip speed and chip thickness. Forty five different blades of various diameters with 36 to 120 teeth of various designs were tested. Major differences in noise level existed between various blade designs. Relative noise level increased with chip thickness. Analysis of tip impact characteristics was performed on a pendulum impact tester. Tip designs with positive side and top clearance angles and a positive hook angle showed reductions in peak acceleration. A substantial reduction in acceleration response was observed for tip designs which produced initial point contact. The only blade design factors that substantially affected noise levels were those associated with overall tip sharpness and tooth geometry. The designs which initially contacted the extrusion at a point appeared to produce substantially less extrusion vibration. Wave propagation along the structure was impeded by attaching flexible transparent vinyl shields to the sides of the frame, allowing the clamp to also function as a partial acoustical enclosure. The author concludes that significant aluminum extrusion sawing noise reduction is achieved with improved blade design, by the application of blade vibration damping collars, and with the use of workpiece clamp and enclosure systems.