Design and Development of a Livestock Feed Mixer with Spring-Controlled Packaging Unit

Abstract

A vertical livestock feed mixer with spring-controlled packaging unit was designed, constructed and tested. This design had in focus a weighing and gauging mechanism which made possible a semi-automatic packaging in conjunction with feed mixing and discharge operations. The main components of the machine included a double-wall cylindrical mixing chamber consisting of recycling gate, discharge gate, evacuating gate, window and a screw conveyor inside an inner cylinder. The packaging mechanism is attached to the discharge gate and the base of the frame with the frame serving as the structural support for the machine and its contents. The main design parameters included screw conveyor features such as helix angle, fill ratio, normal pressure due to bulk load on screw shaft, axial force per pitch, total screw torque, capacity and power requirements of the screw conveyor. The design concept of the packaging mechanism involved determination of free length of spring, total active length, pitch of spring, spring index, stiffness of spring, maximum shear stress and total spring rate. In a hitch-free operation, the machine was designed to package 25 kg of mixed feed ingredients at a time. In operation, the feed ingredients are scooped and moved upward by the rotary movement of the screw conveyor and then sprayed back into the smaller cylinder without passing through the internal tube. A preliminary testing was carried out on the machine to determine the actual discharge rate and hence the performance of the packaging mechanism. Results revealed that an average discharge rate of 0.356 kg/s was obtained. Powered by a 2 hp single phase electric motor, the machine has a mixing capacity of 4.124 m3/h with a production cost of $470.