In this study, PET bottles crushing machine was designed to convert used PET bottles into shreds readily available for recycling. Preliminary tests and mechanical factors were extensively evaluated on the conceptual designs to ensure that the concept with optimal performance and efficiency is selected. Experimental test was conducted to determine the power required to overcome the shear stress of the PET bottles and it was found out that 10hp was the power required. With a set of crushing forces ranging from 1000-3000N, Finite Element Analysis (FEA) was performed for five different scenarios on the 201 Annealed Stainless Steel cutting blade to inspect the material response to stresses and corresponding deformations. The maximum von Mises stress was 2.089e+006N/m^2. The material yield strength was found to be 2.92e+008 N/m^2, and applying a force of 3000N on the cutting blade produced a maximum displacement of 2.220e-003 mm. This therefore imply that the material will not deform or fail under a force equal to or below the material yield strength value. Tests carried out on the final machine design indicated efficiency of 82.2% which is only 6% less than the efficiency of existing ones.
This study involves a comparative analysis of a designed automatic cooling power hacksaw machine and manual cooling power hacksaw machine in a local sawmill where coolant is applied manually by the operator. The automatic cooling power hacksaw machine took an average time of 40 s to cut an average mass of 5.9 kg with average Specific Mechanical Energy (SME) of 29 kj/kg and average cutting speed of 270 rpm. However, the manual cooling hacksaw machine took an average time of 53 s to cut the same average mass of 5.9 kg with average SME of 42 kj/kg and average cutting speed of 269 rpm. The basic idea behind SME was to determine the energy going into the cutting operation process per unit mass of timber in form of work from the motor. From the above stated results, the automatic cooling hacksaw machine designed in this study took less time, less SME and slightly higher cutting speed to cut the same quantity of timber than the manual cooling hacksaw machine. Compared to the manual cooling power hacksaw, the automatic cooling power hacksaw machine is obviously more efficient in terms of time and energy savings.
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