Design, Development and Performance Evaluation of Turmeric Polishing Machine

Abstract

Turmeric (Curcuma longa Linn), locally known as ‘Ird’, is the dried rhizome of herbaceous plant grown extensively in tropical and subtropical parts of Ethiopia. It is widely grown in most parts of the country, such as Jimma, Metu, Tepi, Bebeka, Wonago, Awasa, Mugi, Bako, Sheka, Benchmaji, and Kefa. It has a rough, dull outer surface with scales and root crumb, which needs to be polished for higher quality and price. Manual and/or mechanical polishing improves its appearance, resulting in relatively smooth, bright and yellow surfaces. However, the manual processing challenges and the demand for high-quality final products have created a need for the development of turmeric polishing machines. Therefore, this research focused on the design, development and performance evaluation of an engine operated turmeric polishing machine suitable for small holder farmer and small-scale enterprises. The designed machine consists of several components such as engine as power source, speed reducing system, power transmission component parts, octagonal drum as polishing unit and collector. The physical properties of turmeric rhizome used to design and select component parts of the machine were studied with samples procured from farmers. The performance evaluation of the machine was carried out on three levels drum speeds (70, 85, 95 rpm), polishing time (15, 20, 25 min) and three different moisture content (6, 9, 11%) for fixed capacity of 200 kg turmeric in the drum. The results showed that the machine had a polishing capacity of 364 kg/hr. The linear regression analysis was used to determine if the predictor variables could influence the polishing percentage, damage, and fuel consumption during polishing. The likelihood function analysis of linear regression depicted that damage of product during test of turmeric was influenced by all independent variables with R 2=0.893 and DWC of 0.367 at significance level of p<0.001. Furthermore, the analysis showed that all predictor variables significantly influenced polishing percentage at significance level of P<0.001. The polishing percentage increased with increasing speed, longer polishing time and higher moisture content. However, further analysis showed that a slight decline in polishing percentage when the drum speed exceeded 85 rpm, likely due to centrifugation effects within the drum. Additionally, the performance evaluation demonstrated that fuel consumption was directly affected by predictor variables, except for moisture content, with an R2 value of 0.993 and a DWC of 2.530. Based on the performance results, the machine was deemed acceptable and suitable for use by smallholder farmers and small-scale enterprises.