Methodical Design of a Soybean Dehuller

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1 Methodical Design of a Soybean Dehuller Rasool KHODABAKHSHIAN *, Bagher EMADI Department of Agricultural Machinery Engineering, Ferdowsi University of Mashhad, P.O. Box Mashhad-IRAN ra_kh544@stu-mail.um.ac.ir Abstract: The methodical design of a dehuller for using in soybean processing is described. The long term objective of the project was designing of a centrifugal dehulling system in soybean processing by development of a concept solution. The distinguishing feature of the described design procedure was the use of a structured design approach, which forces the designer to methodically review and compare alternative solution options, thus preventing the selection of solutions based on prejudice or belief. The unit consists of two main parts: the dehulling set and the power transmission system. The dehulling set consists of a rotating drum and a separate rotating circular base plate. These two parts rotate in opposite directions, employing two separate electrical motors. Some of the advantages of this new machine are simple mechanisms, avoiding from using any complex part, capability of automation, simple usage, simple maintenance and finally low cost of the machine. Key words: Soybean, dehulling, methodical design, centrifugal force INTRODUCTION Soybean is considered to be an important oilseed crop because of containing highly nutritious oil in large quantity (Shukla et al., 1992). Soybean contains about 40% protein and 20% oil. Soy protein is the most economical protein produced in the world. The high quality of soy-protein is illustrated by its content of all the essential amino-acids except sulphur which contains amino-acids. Supplementation of the cereal based diet with soy-protein gives an amino-acid complementation which results in increased protein quality and quantity approaching to that of animal protein (Kiber and Öztürk, 2008). Nowadays, soybean can be montioned as an important plant for agriculture, because it is one of the main food sources for human and animal nutrition. It is a food source which contains high quality protein and does not contain cholesterol and saturated fatty acids. It is used in food industry for fat products (gliserol, refined soybean oil), complete soybean products and soybean protein products (soybean flour or soybean crust). Soybean production is about tons in the world every year. The most largest soybean producer of the world is the USA. That country produces nearly 2/3 of the total world production, followed by Brazil, Argentina and China (Tas, 2003). For food uses of soybean, it is essential that its hull content which is about 10% of the weight of beans to be removed. Soybean hull is loosely attached with the cotyledons. Simple mechanism of rubbing the soybean seed/grain between two surfaces can detach the hull. Five types of dehullers have been developed for soybean in Iran. These are rotor concave type, hand grinder, manually operated, power operated and cylinder-concave. Increasing rate of soybean usage, high food value and production-exportation growth, necessitated more investigation and attention toward this product. Mechanized process of soybean production before and after harvesting has great impacts on quality, food value, competitive market and the world production of this strategic produce. On the other hand, any analytical and applicable investigation for the better production process, directly or indirectly, has pronounced effects on farmer's income (Shukla et al., 1992). While performing preliminary trials employing various dehulling methods, it was observed that the 186

2 dehulling based on the principle of centrifugal action gave better performance for this seed as compared to dehulling of soybean seeds using rubber roll sheller and under runner-sheller. Soybean seed having a flattened shape and loosely bound hull (Shukla et al., 1992) presented an inherent difficulty in dehulling of seed using rubber roll sheller and a considerable proportion of the seed escaped undecorticated and gave low dehulling efficiency. On the other hand, in under runner-sheller, abrasion forces which crushes the seed causing a high proportion of brokens; the brokens thus have generated much more nonrecoverable fraction of kernel (fines) i.e. fine kernels going as a waste in the hull during separation of dehulled seeds from the hulls. So, this paper presents the design of soybean dehuller using a methodical design method from mechanical engineering. MATERIALS and METHOD The soybean dehuller was designed using a methodical design technique described by Bakker et al. (2010). This technique belongs to a class of methods using a phase model of the product design process. These methods describe the product design as a process consisting of different phases at different levels of abstraction. The phases are (1) 'problem definition phase', (2) alternatives definition phase' and 'forming phase' (Fig. 1). The results of respective phases are a function structure, a concept solution and prototype, respectively. Objective Problem definition phase Function structure Alternative definition phase Concept solution Forming phase The problem definition phase starts with defining the objective of the design. In the problem definition phase a set of requirements are established, that can be split into fixed and variable requirements. A design that dose not satisfy the fixed requirements is rejected. Variable requirements have to be fulfilled to a certain extent. To what extent these requirements are fulfilled, determines the equality of the design. The variable requirements are also used as criteria for the evaluation of possible concept solutions. The last part of the problem definition phase consists of the definition of the function of the machine. A function is an action that has to be performed by the machine to reach e specific goal. In our case, important functions are charging, dehulling, separating and discharging. The functions are grouped in a function structure, which represents a solution on the first level of abstraction (Fig. 2). The function structure consists of several functions. Every function can be accomplished by several alternative principles. e.g. mechanical and thermal principles. Charging of hopper from soybeans Hulling stage Separating Discharging Figure 2. The function structure In the alternatives definition phase, possible alternative principles for the various functions are presented in a morphological chart (Fig 3). The left column list the functions and the raw display the alternative principles. By selecting one alternative for each function and by combining these alternatives, concept solutions are established. These concept solutions are represented by font color (red) in the morphological chart. The best concept solution is selected using a rating procedure. In the forming phase the selected concept solution is worked out into a prototype. Prototype Figure 1. The design process Application for soybean dehuller According to the ultimate research objective, formulated as design a soybean dehuller that can do dehulling, the first step in the problem definition 187

3 phase was to establish the set of requirements. For this purpose, interviews were held with potential users, scientists and manufactures related to soybean processing systems. The resulting requirements are listed in Table 1. Table 1. The resulting requirments Fixed requirements Variable requirements Producible in sample Short time in processing. workhouses. Competitive with Less fraction of kernel. available machines. Competitive with Longevity of machine. available machines. Different from available Consumable power. models. Safety. - Figure 3. Morphologic chart As it can be seen, possible alternative principles for the various functions are listed in a morphological chart (Fig 3). Five experts involved in the soybean processing indicated possible concept solutions in the chart. These concept solutions were then weighted against each other in consultation based on their expert knowledge, using the variable requirements listed above. Examples of these results for dehulling stage are presented in Table

4 Value Function Table 2. Rating procedure of possible alternative principles for dehulling stage Short time in processing Less fraction of kernel Producible Longevity of machine Consumable power Total score Abrasive Rollers Bolt Type Rollers Centrifugal Force with Ragged Surface Centrifugal Force with Blade Dehulling Blades Threshing unit Annular Huller Belt Conveyor Huller Abrasive Brushes Jagged Walls Shaker The prototype machine This section describes how the concept solution is worked out in detail. A general view of machine is shown in Figure 4. Modeling and mechanical analysis of machine is performed using solidworks 2007 software and cosmos 2007 software, respectively. In order to hull soybean in this machine, centrifugal force is used. The unit consists of two main parts: the dehulling set and the power transmission system. The dehulling set consists of a rotating drum and a separate rotating circular base plate. These two parts rotate in opposite directions, employing two separate electrical motors. The power transmission system of machine is mechanically by belt and pulley, so that they convey power of 3 hp between electrical motors and dehulling set. In the discharging stage, the rotation of the drum will be stopped while rotating circular base plate will rotate and discharge gate will be opened. 189

5 Figure 4. General view of the proposed machine DISCUSSIONS and CONCLUSIONS The research dehuller was designed using a structured design method. The advantage of using this method is that it clearly structures the design process. It provides a good overview of the complete design and because of the structured sequence of design activities, it is easy to keep track of the progress of design. Another advantage of the structured design method is that it forces the designer to look at alternative solutions and this decreases the probability of heuristic bias and increases the quality of the outcome. Although the designer is forced to thoroughly judge the identified alternative solutions when selecting the final concept, the outcome is still depending on the available knowledge of the designer about the alternative solutions. So, while the method can not guarantee that the absolute best solution possible will be selected, it certainly is superior to a trial and error approach. In a research context it is easy to identify alternative subjects that are worthwhile to investigate further, while in the same time the main line of the research remains clear. As we know, soybean process is a costly operation for the producers. If these costs are reduced, not only the soybean consumption but also the competitions of producers in world scale increases. All the expenses of the whole soybean process include the followings: the costs of machineries used, production wastes, workers wages, transportation and the time consumed during the process. Among those, the first two constitute the highest portion. Consequently, performing some operations of process only in one machine seem beneficial from several aspects. First of all, the expenses for maintenance and repair of one machine are remarkably lower than a number of machines involved. Secondly, expenses due to the transportation are approximately omitted and eventually, automation of the machine for the automatically continuous fulfillment of the steps of the process increases. Regarding the simple mechanism of belt and pulley for the power transmission, easy and simple assemblage, capability of being equipped with automatic systems for the process and other predicted advantages for the machine, it can reduce a lot the total expenses. Present innovative mechanism can be used for hulling other oil seeds such as safflower seed, sunflower seed or pumpkin seed, but with some modification and adaptation in design. ACKNOWLEDGMENTS The authors would like to thank Ferdowsi University of Mashhad for providing the laboratory facilities and financial support. REFERENCES Shukla, B.D., P.K. Srivastava, R.K. Gupta, Oilseed processing technology. Bhopal, India: Central Institute of Agricultural Engineering Publications. Tas, M.T, Magical Bean: Soybean. DID Press, Ankara, Turkey Kiber, H., T. Öztürk, Physical and mechanical properties of soybean. Int. Agrophysics, 22: Bakker T., K.A. Van, J. Bontsema, J. Muller, G.S. Van, Systematic design of a autonomous platform for robotic weeding. Journal of Terramechanics, 47:

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