Development and Performance Evaluation of a Single Screw Extruder for the Production of Floating Fish Feed

An extruding machine for the production of floating fish feed was designed and fabricated. Performance evaluation of the fabricated floating fish feed extruding machine was done. The design of the hopper; shaft, barrel, screw and die of the machine were done using standard equations. Effect of extrusion parameters which are moisture content (20% 25%, 30%, 35%, and 40%) die size (2 mm, 4 mm, 6 mm, 8 mm and 10 mm) and screw speed (150 rpm; 200 rpm, 250 rpm, 300 rpm and 350 rpm) on expansion ratio, floatability, specific mechanical energy and efficiency were evaluated. The result shows that moisture content has significant effect on all the variables, as highest expansion ratio of 32% was obtained at 30% moisture content and 6 mm die size. Highest feed floatability was 97% at 30% moisture content and 6 mm die size. The highest specific mechanical energy of the machine was 30 kJ/kg at 40% moisture content and 4 mm die size. Die size variation also shows high impact on the machine performance, showing highest efficiency of 83% at 10 mm die size and 250 rpm while the floatation rate was 98% at 6mm die size. Screw speed has significant effect on efficiency having the highest as 85% at 150 rpm and floatability of 93% at 150 rpm while the specific mechanical energy of 29 kJ/kg was the highest at 350 rpm. Operation condition was at its best at 30% moisture content; 6 mm die size and 150 rpm of screw speed. The feed moisture content, machine die size and screw speed have significant effect on the performance of the machine. Careful selection and combination of these factors will give optimum performance of the machine during extrusion of resin.