An Investigation of the Optimal Cutting Conditions in Coconut Wood and Palmyra Palm Wood Turning Process Using Design of Experiment

Abstract

The purpose of this research is to investigate the effect of factors on the surface roughness in the coconut wood and palmyra palm wood turning process for manufacturing furniture parts using carbide cutting tools. The main factors, namely, cutting speed, feed rate and depth of cut were investigated for the optimum surface roughness in furniture manufacturing process. Normally, an acceptable surface roughness is between 3.0 - 9.0 µm before the sanding process. The result of preliminary trial shows that the depth of cut had no effect on surface roughness. Moreover, it was found from the experiment that the factors affecting surface roughness were cutting speed and feed rate, with a tendency for reduction of roughness value at lower feed rate and greater cutting speed. Therefore, in the turning process of coconut wood, it was possible to determine a cutting condition by means of the equation R_a = 3.90 - 0.00375 Cutting Speed+7.93 Feed Rate, This equation can be best used with a limitation of cutting speed at 170 - 353 m/min, feed rate at 0.05 - 0.16 mm/rev and depth of cut at 1 mm. In the turning process of palmyra palm wood, equation R_a = 3.38 - 0.00164 Cutting Speed+10.8 Feed Rate, This equation can be best used with a limitation of cutting speed at 188 - 392 m/min, feed rate at 0.05 - 0.12 mm/rev and maximum depth of cut at 1 mm. To confirm the experiment result, a comparison between the equation value and an actual value by estimating a prediction error value was calculated with the surface roughness and margin of error not over 10 %. The result from the experiment of mean absolute percentage error of the equation of surface roughness is 4.28 % for coconut wood and 3.47 % for palmyra palm wood, which is less than the predicted error value and is acceptable.