Performance Characteristics of a Coconut Dehusking Machine

A coconut dehusking machine was developed and evaluated in terms of dehusking performance. The model consists of different component assembly parts such as speed reduction, transmission, coconut base, dehusking blade, frame, and control system. It is powered by a 7.5 hp gasoline engine and with an average output capacity of 240 coconut per hour. Its salient features which give it an edge over other existing machines in attaining effective dehusking are as follows: 1) a dehusking blade with cutting tooth and blade side face angle, 2) movable coconut base assembly, 3) ability to remove husks starting at the basal portion, which is the softest part of the coconut, and 4) operable by a single person. The cutting tooth initiates the initial penetration of the blades while the side face angle can assist better piercing or shearing action on the coconut husks. The coconut base can be moved upward or downward and can accommodate different coconut sizes. The effects of different factors which include the machine's crankshaft speed, coconut size, and blade side angle on the response variables were investigated. Response Surface Regression (RSReg) and Response Surface Methodology (RSM) were used to determine the effect of the treatment factors and optimum performance of the machine; respectively. Fifteen (15) experimental runs using Box and Behnken design with three level-incomplete factorial designs were conducted. The different dependent variables studied consisted of force and power requirement, dehusking time, dehusking capacity, percent coconut shell damage, and dehusking efficiency. Results revealed that variation on the levels of treatment factors significantly affect the response variables except percent coconut shell damage. Data obtained from the response variables mostly fit the linear, cross product, and quadratic regression models. The superimposed contour plots of different factors generated an optimum region and yielded a dehusking performance with force requirement of 109.59 N, power consumption of 6.41kW, dehusking time of 3.34 minutes, dehusking rate of 4 nuts per minute and dehusking efficiency of 85.23 %. Moreover, results of the verification tests indicated that the actual values of responses were relatively close to the predicted values.