DESIGN AND FABRICATION OF POLYVINYL CHLORIDE PIPE LABORATORY EXTRUSION MACHINE

Abstract

Mechanical engineering laboratory of Federal University of Minna, Nigeria requires extrusion machine that can be used for teaching and learning of PVC extrusion process. The teaching and learning of PVC extrusion are rarely thought using extrusion machines that help to bridge the gap between engineering graduate in industry and student learning in the university. Against this background, a need emerges for the design, and fabrication of laboratory PVC extrusion machine. The laboratory PVC extrusion machine is a machine that could be used to produce thermoplastics pipes. The PVC pipe is done by forcing the resin (PVC melt) to flow through an opening annular die. It is necessary to produce the pipe with indigenous technology to meet increasing demands of pipe usage in our homes such as, portable water sewage and electrical conduit pipes. The design of extrusion machine involves selection of specified drives, feeding and control systems. The drives used were spur gears, screw shaft, thrust bearing and electric motor. The required power for the machine was 6.93 kW with power scale up factor of 0.122 and gearing ratio of 2:1. The feeding system is cylindrical barrel of diameter 770mm and hopper with electrical control switch for control purpose. The machine is designed analytically and modelled using Pro-Engineer software before being fabricated. The compression ratio used for the design of the machine was 8:1 with extruder length being 1120 mm. The maximum shear stress for the extruder design was 17.1 kN/m^2 with extrusion pressure of 7.7 M N/m^2. The design extruder circumference speed was 1.2 m/s with plastic flow rate of 1m/s. The velocity drop at die inlet was 0.1m/s. Drag or volumetric flow rate of the PVC melt from the extruder was 0.0009 m3/s. The mass flow rate of the PVC melt was 7.9kg/s. The pipe produced by the machine is 40mm diameter. The pipe was bent in structure due to lack of automated temperature controller system in the machine and a plate to slide on to avoid deformation due to its weight. The machine efficiency is 51% and it was fabricated with locally sourced materials. The use of this machine for practising PVC extrusion process will boost student’s knowledge of extruding process.