Design and fabrication of a flour and sugar mixing machine

Abstract

Mixing food is one of the key processes in the food industries. Currently, Iowa State University Uganda Program in Kamuli district rely entirely on traditional hand mixing methods. Flour and sugar are laid on a tarpaulin and mixed using hands. The method produces few substrates that are not evenly mixed and takes a lot of time and effort. Moreso, flour is exposed to the environment increasing the risk of contamination by dust and growth of micro-organisms which pose a threat to the final consumers. Therefore, a sugar and flour mixing machine was developed and tested to facilitate mixing at the facility. The machine is driven by a 1.5 kW (2 HP) single phase motor. It comprised of a mixing trough, helical blades mounted on a shaft, a bushing through which a shaft passes, and discharge cute at the bottom of the trough. The motor transfers power to the transmission system (pulleys and belts) which in turn transfer it to the shaft and helical blades. The helical blades bring about circumferential and axial flow that lead to efficient mixing. Detailed design of the components was done using Solid works software. This was followed by fabrication of the designed components and assembling of the machine. The values of maximum tangential force, normal force in the shaft, the equivalent maximum bending moment, torque, and permissible stress are 189.21N, 109.24N, 25.55KNm, 56.76KNm and 207MPa respectively. Performance evaluation results of the machine at no load test showed that, the machine can run freely without too much noise and there were no visual breakdowns. The machine was tested using a feed component divided into 3.5 kg for sugar, and 25 kg for millet flour replicated thrice at four mixing durations of 5, 10, 15 and 20 min. The average coefficient of variation was 13% which shows a significant reduction in feed components for the samples tested. The average machine capacity was found to be approximately 300 kg/hr with a mixing efficiency of 87% and mixing time of 12.5 minutes. The machine is affordable to the organization (ISU-UP) and can be fabricated from any workshop since it is made up of readily available and locally sourced materials.