The design, fabrication and evaluation of a waste plastics crushing machine for the company's raw materials accessibility

Abstract

A low-cost variable-speed waste plastic crushing machine was designed, constructed, and tested to evaluate its efficiency and throughput. The machine consists of a hopper, a pulley, a crushing compartment with knives, and a 3 HP variable-speed electric motor. This work aimed to construct a machine that shreds waste plastic into smaller sizes at different working speeds for recycling. Also, the machine was constructed from locally available materials; therefore, its cost is very low and affordable. The machine's throughput at 900rpm, 750rpm and 600rpm was 30.57 kg/hr, 23.37 kg/hr and 21.37 kg/hr, respectively, for PVC-type waste plastic. The Specific energy consumption of the machine at 900rpm, 750rpm and 600rpm was 134.88 kJ/kg, 176.37 kJ/kg and 192.89 kJ/kg, respectively, for PVC-type waste plastic. The average particle size of the machine products at 900rpm, 750rpm and 600rpm was 2.54mm, 2.42mm and 2.21mm, respectively, for PVC waste plastic. The machine's efficiency at 900rpm, 750rpm and 600rpm was 87.45%, 88.95% and 90.24%, respectively, for PVC waste plastic. The optimal operating speed depended on the parameter considered paramount; the best crushed waste plastic, based on average size and crushing percentage, was obtained at 600rpm. Considering the throughput, the optimal result was obtained at an operating speed of 900 rpm. Also, considering the Specific energy consumption, the optimal result was obtained at an operating speed of 900rpm. The cost of fabricating the machine was 126,850 NGN.