Multi-objective optimization of turning process parameters and wood sawdust contents using response surface methodology for the minimized surface roughness of recycled plastic/wood sawdust composites

The objective of this work was to investigate the effect and optimization of turning parameters such as spindle speed, feed rate, and depth of cut as well as wood sawdust content on the roughness quality of wood-plastic composites (WPCs). The Box–Behnken design and response surface methodology were used in experiments. Three roughness parameters, namely average roughness (Ra), root mean square average of roughness (Rq), and average maximum height (Rz) were employed to evaluate the surface quality of WPC samples. Based on the findings of the experiments, the Ra, Rq, and Rz values reduced with increasing spindle speed in a range of 430 to 1030 rpm, whereas the values increased when increasing the feed rate in a range of 0.05 to 0.15 mm/min. Also, an increase in depth of cut ranging from 1 to 3 mm and WPCs with a higher amount of wood sawdust in a range of 30 to 50 wt% raised their surface roughness. Finally, optimal conditions for the turning of the WPCs were determined to comprise a spindle speed of 781 rpm, a feed rate of 0.05 mm/min, a depth of cut of 2.8 mm, and wood sawdust content of 30 wt% with the highest desirability score of 1.000. Under such conditions, the sample had Ra, Rq, and Rz values of 1.8, 2.2, and 11.3 µm, respectively. The optimal conditions for turning can be used to effectively process different WPC products into various shapes.