Design and fabrication of a manual tamarind powdering machine.

Abstract

Value addition in agricultural products is essential for the development of the sector in Uganda (MAAIF, 2011). The study was aimed at achieving this through powdering tamarind flesh. The fruits when ripe contain rust coloured pulp (flesh) which was of major interest in the study. The fruits were deseeded and the flesh dried till crisp for easy grinding. Size reduction by attrition was employed in order to achieve powdering of the dried tamarind flesh. The major objective of the study was to develop a manually operated tamarind powdering machine which would enhance cheap powdering of the fruit pulp. The powder can be stored easily, has low logistic expenses, more hygienic in preparation, easy to use, convenient as there is no need to bother about disposal of residue as is the case when dry tamarind is soaked in water; and above all has a much stable and longer shelf life because of the lowered moisture content of about 3.5-8.8 0/0 (Singh et al, 2007). Implementation of this project was carried out within a period of four months. Design of the various parts was done by analysing forces acting on them so that components would not fail during operation. Several methods were used in fabricating the different machine components. The methods included cutting, welding, threading, grinding, drilling, chiseling, machining, etc., Components like bearings, shaft, and grinding plates were selected from those available in the market- The machine components were assembled into one unit after they were fabricated- Testing of the prototype revealed the machine's grinding efficiency as 55.6% for a product size of 1,000 — 2,000 um, capacity as 0.8 kg/hr at inter-plate clearance of 5mm. Total production cost of the machine was 873,000 UGX ($250). It also revealed that the grinding efficiency greatly depends on the moisture content of the feed (dried tamarind pulp), and desired product Size of the user which is influenced by the inter-grinding plate clearance. The study also showed that the dried tamarind flesh and powder exhibit hygroscopic properties and therefore need to be kept in air tight containers free from atmospheric moisture content.