Development and Evaluation of a Motorized Plantain Slicing Machine.

Transcription

1 Futo Journal Series (FUTOJNLS) e-issn : p-issn : Volume-4, Issue-1, pp Research Paper July 2018 Development and Evaluation of a Motorized Plantain Slicing Machine. * 1 Chilakpu, K. and 2 Ezeagba, A. C. 1 Agricultural and Bioresources Engineering, Federal University of Technology, Owerri, Nigeria. 2 Agricultural and Bioresources Engineering Department, University of Nigeria, Nsuka, Nigeria. Abstract *Corresponding Author s kchilakpu@yahoo.com A motorized slicing machine was developed using locally available materials for size reduction of some freshly harvested farm products. The machine consists of 520 x 400 x 580 mm size main frame. The frame is made of 30 x 30 mm mild steel materials. The feeder assembly consists of a cylindrical hopper with three feeding chutes of different diameters; 50, 47 and 45 mm for big, medium and small peeled plantain. The cutter assembly comprises of three stainless steel blade fixed at an angle of 120 degrees to each other. Below the cutter blades is an adjustable plate which serves as a restriction to prevent the plantain from dropping into the collection tray without being cut. The machine works on the rotational principle whereby the peeled plantain is fed vertically into the cutting edges of the rotating blades. The slicing machine was powered by a 0.75kw electric motor running at a speed of 360 revolutions per minutes (rpm). It has a throughput capacity and slicing efficiency of 63.23kg/hr and 95.43% respectively when used for the slicing of fresh plantain thickness of mm. Keywords: Motorized, plantain, Slicing, Development, t-distribution. 1. Introduction 1.1. Background Study. Plantain (Musa paradisiaca L.) is a crop which is generally grown in tropical and temperate region of the world, and is a good source of vitamins and dietary fiber. Plantain provides a well balanced diet compared to any fruits and satisfies the definition of good food that is which is easily digested and absorbed in our body. It contains energy 510KJ (120kcal), carbohydrates 31.9g, sugars 15g, dietary fibers 2.3g, fat 0.37g, thiamine (vitamin B1) 0.052mg (5%). A bunch consists of several fingers (several plantains attached in a single bunch), each having a length in the range of mm, and width of between mm, (CRFG, 1997). Industrially, plantain fruit serves as composite in the making of baby food, bread, biscuit and others (Ogazi, 1996; Ayeampong, 1999). Most of the methods of processing plantain pass through the slicing process. The nutritional demand for plantains and its by-products in this 135 Chilakpu et al., Development and Evaluation

2 part of the world call for serious effort aimed at developing more efficient processing machine to meet the product demand. Obeng (2004) reported a highly mechanized plantain slicing machine produced at Kwame Nkrumah University of Science and Technology Kumasi Ghana with a capacity of 100kg/hr of plantain slices. However, this machine has not been attractive to farmers because it slices plantain longitudinally inform of shreds. Bello, et.al, evaluated a plantain slicing machine produced by National centre for Agricultural Mechanization (NCAM). The NCAM slicing machine is not only limited by its low reported slicing efficiency of 63.03% it can only handle a plantain finger at a time. The developed plantain slicing machine cut the plantain fingers in transverse section with additional advantage of handling up to three different sizes of plantain in a batch Statement of Problem Locally, plantain slicing is manually done with knives by family members or hired labour. This method is slow and labour intensive as only about 35 kg of plantain pulps could be sliced by a labourer in a day. The existing plantain slicing machines do not seem to be acceptable to most farmers due to low efficiency and the shape of slices produced. This calls for the development of a more efficient machine that will cut plantain into shapes acceptable to the farmers Justification of the Study Plantain and it s by products has become a staple part of the cuisine of many families. Plantains are readily eaten in form of chips at home, cinemas and other public places as snacks. To meet the ever increasing demand for this product, there is need to mechanize the processing to overcome the drudgery associated with the manual slicing method. To ensure more acceptability in the market, there is every need to improve on the design of a transverse plantain slicing machine to meet individual and commercial requirements. 2. Materials and Methods Motorized slicing machine considering the need for hygienic processing of plantain as food, stainless steel materials were used for the part of the machine in direct contact with the product while mild steel was used for other parts such as the frame work to reduce production cost. This new machine frame is made of 50 x 50 mm mild steel angle. The frame length, breath and height are 520 x 400 x 580 mm respectively. These sections are firmly joined with arc welding. The bearings, connecting shaft, housing cover and prime mover are mounted on this frame. All these accessories were mounted with the help of fasteners. The feeder assembly consists of a cylindrical hopper with three feeding chutes of different diameters; 50, 47 and 45 mm for big, medium and small (feed tubes) were selected for round slices considerably the maximum effective width and diameter of the peeled plantain. The length of the feeding chutes (tubes) is 75 mm for providing sufficient space for feeding the plantain from the top. The cutter assembly comprises of a three cutting blades of 75mm long and 1.5mm thick. The blades are mounted at an angle of 120 degrees to each other on a disc which is fastened to a 30mm drive shaft as shown in Figs.4 and 5. Below the cutting blade arrangement is a restriction plate to prevent the plantain to be sliced from dropping into the collection tray without being cut. 136 Chilakpu et al., Development and Evaluation

3 A number of researchers that include; O Dogherty, (1981); Persson, (1987); Balasubramanian, Sreenarayaanan and Visvanathan, (1993); Kachru, Balasubranian and Kotwaliwale, (1996) and Akande and Onifade, (2015) in their studies reported that cutting of agricultural materials are influenced by the cutting velocity, shear force of cut and the power available to the cutting tool Force Required for Shearing the Raw Plantain According to the work of Odekunle (1986), the force required to shear the raw plantain was given by equation 1; = Force required for shearing the raw plantain (Newton) = Area under shear (m 2 ) = Shear stress of the raw plantain (N/m) D = Diameter of raw plantain 2.2. Cutting Power Requirement The power required by the cutter to slice the raw plantain may be obtained from the expression by Saeed, (2001)as shown in equation 3; = Power required by the cutter (watt) = Linear velocity of the cutting blade The linear velocity was given by equation 4; = Angular velocity of rotating disc r = Radius of cutting disc (on which the blades are mounted) 2.3. Torque Requirement The torque acting on the shaft was calculated for the cylindrical shaft using equation 5; P = Power to be transmitted by shaft = 0.75KW (electric motor). T = Allowable torque on shaft (N/m 2 ) N = Rotating speed of shaft (rpm) 2.4. Determination of Pulley Speed and Size The electric motor transmit power through the pulleys to the shaft carrying the cutting blades. The diameters of the pulleys were calculated as shown in equation 6 according to the work reported by Kachru (1996). 137 Chilakpu et al., Development and Evaluation

4 where, N 1 = Speed of the pulley on the motor (rpm) N 2 = Speed of the pulley on the shaft (rpm) D 1 = Diameter of the pulley on the motor (mm) D 2 = Diameter of the pulley on the shaft (mm) 2.5. Shaft Design In designing the driving shaft, a combination of twisting moment and bending moment were considered as the major forces acting on it as shown in Figure 1. According to the work of Khurmi and Gupta (2010), by limiting the maximum shear stress ( max) equal to the allowable shear stress ( ) for the material, the equivalent twisting moment was calculated using equation 7. where; T q = Equivalent twisting moment (Nmm) m = Bending moment (Nmm) T = Twisting moment (or torque) acting upon the shaft (Nmm) = Shear stress induced due to twisting moment/allowable shear stress (N/mm 2 ) d = Diameter of shaft (mm) Figure 1: Load, Shear Force and Bending Moment Diagram. The orthographic diagram of the developed machine and the cutting blade arrangement are as shown on Fig.2 and 3 respectively. 138 Chilakpu et al., Development and Evaluation

5 Figure 2 Orthographic Projection of New Machine Figure 3 Plan View of the Cutting blade Arrangment The shaft blade arrangement and the Isometric view without the outside cover of the developed machine is as shown on fig.4 and fig.5 respectively Figure 4 The shaft blade arrangement. Figure 5 Isometric view without the outside cover of the developed machine The plate of the fabricated machine with the outer cover showing the three feeding holes for various sizes of materials and the product out let is as presented on plate 1. Plate 1. Photograph of developed machine 139 Chilakpu et al., Development and Evaluation

6 3. Operational Principle of the Developed Machine The developed machine works on shear cutting principle as presented by Clarke (1987). The machine has three stainless blades mounted on upper end of the power shaft rotating at a speed of 360 rpm slicing of the products. The peeled plantains were manually fed vertically through the feeding hole to the rotary blades. A stainless steel base with an adjustable height is placed below the cutting blades to prevent the products from passing through without being cut, and also to ensure uniform thickness of the sliced products Performance Evaluation To evaluate the performance of the machine, the approach recommended by Kachru, Balasubranian and Kotwaliwale (1996) was adopted for its simplicity. One hundred fingers of plantain was used for this experiments. The clearance between the cutting blades and the restriction base which determines the thickness of the plantain slice was varied between 6.0, 6.5, 7, 7.5 and 8.0 mm in line with the thickness of the manually cut slices in the open market which has an average of about 7 mm. The plantain fingers were peeled manually, weighed and sorted according to the feeding holes sizes. They were manually fed into the matching feed hole while the machine was running; the time taken to completely slice each plantain finger was recorded. This experiment was repeated five times for each slice thickness at different speed range of 250, 360, 460 and 500 rpm and the average results recorded Operating/Slicing Efficiency of the Machine (Es) This was obtained by feeding some plantain into the machine and after each operation the products (slices) are weighed irrespective of damaged slices per unit operation. The damaged or products with uneven cut thickness were manually picked out of each trial operation and weighed separately. Five independent trials were carried out at each speed level and their average weights recorded. The operating/slicing efficiency of the machine was determined using equation Throughput Capacity, (T c ) The quantity of material that the machine can handle in a given time was determined using equation 9; 9 4. Variation of Slicing Force of Plantain For Days of Storage It was observed in the course of evaluating the performance of the developed machine that the ripeness or length of storage of a feedstock affects the amount of force required for the slicing of a given product as shown in Fig Chilakpu et al., Development and Evaluation

7 Transverse and Longitudinal Cutting Force (N) y = x R² = y = x R² = Number of Storage Days TRANSVERSE CUTTING FORCE (N) LONGITUDINAL CUTTING FORCE (N) Linear (TRANSVERSE CUTTING FORCE (N)) Linear (LONGITUDINAL CUTTING FORCE (N)) Figure. 6 Slicing force required for transverse and longitudinal plantain cutting against days of Storage Discussion The developed slicing machine was powered by a 0.75kw electric motor, various ranges of machine speed (250,360,460 and 500rpm) were used to determine the optimum operational speed for plantain slicing. The optimum results were obtained at a machine speed of 360 revolutions per minutes and a throughput capacity and slicing efficiency of 63.23kg/hr and 95.43% respectively when used for the slicing of fresh plantain thickness of mm. The machine was quite stable (not wobbling) in operation and took an average of 5 seconds to complete each slicing batch. It was observed in the course of evaluating the performance of the developed machine that the ripeness or length of storage of a feedstock (plantain) affects the amount of force required for the slicing. Fig 6 gave a graphical presentation of the effect of storage on the cutting force requirement of plantain. The trend of graphs for transverse and longitudinal force requirement indicated that the slicing force decreases as days in storage increases. This could be as a result metabolic activities and deterioration going on within the product. A linear regression equation was developed for transverse cutting force and longitudinal cutting force as shown in equation Equation 10 gave the R 2 for transverse cutting force while eqn. 11 gave the R 2 for longitudinal cutting force. The developed linear regression equations for transverse and longitudinal cutting force are as presented by equation 12 and 13 respectively. = Number of days. = Transverse cutting force = Longitudinal cutting force The implication is that when the number of days of storing plantain is known, equations 12 and 13 could be used to determine the required cutting force in the transverse or longitudinal 141 Chilakpu et al., Development and Evaluation

8 sections. The result of this work has buttressed the point that it requires higher cutting force to slice plantain in the longitudinal section than the transverse section Conclusion A motorized slicing machine was developed with locally available materials for the slicing of freshly harvested farm products (plantains). The develop machine in addition to slicing peeled and unpeeled plantain can also be adjusted to slice other agricultural products such as; banana, cucumber, carrot among others. Based on the results of the test obtained, the machine proved to be a better design than the existing in that the slicing time of plantain is reduced from minutes to 5-6 minutes. In addition, the use of stainless materials in area in direct contact with the product ensured that there was no discoloration of the sliced chips produced.. References Akande, F.B & Onifade, T. B. (2015). Modification of a plantain slicing machine. Innovative Systems Design and Engineering, 6 (10), Ayeampong, E. (1999). Plantain production, marketing and consumption in West and Central Africa. Proc. International symposium on Banana and Food Security. Douala, Cameroon 10-14, November Balasubramania, V.M., Sreenarayaanan, V. V. & Visvanathan, R. (1993). Design, development and evaluation of cassava chipper. Agric Mechanisation in Asia, Africa and Latin America, 24(1), Clarke, B. (1987). Post-harvest Crop Processing: Some Tools for Agriculture. London: Intermediate technology Publications. CRFG (1997). Banana fruit fact. Accessed 10 April Kachru, R.P., Balasubranian, D. & Kotwaliwale, N. (1996): Design, development and evaluation of rotary slice for raw banana chips. Agric Mechanisation in Asia, Africa and Latin America, 27(4), Khurmi, R.S. & Gupta J.K. (2004). A text book of machine design. Nagar, New Dehil: Eyrasia Publishing House Ltd. Ram, Odekunle, O.I. (1986): Design and construction of a mechanical yam slicer. Unpublished B.Sc (Hons) Project. Department of Agricultural Engineering, University of Ibadan. O Dogherty, M.J. (1981). A Review of research on forage chopping. Journal of Agricultural Engineering Research, 27(2), Obeng, G.Y. (2004). Development of mechanized plantain slicer. Journal of Science and Technology, 24(2). Ogazi, P.O. (1996). Plantain: Production, Processing and Utilization. Uku-Okigwe: Paman and Associates Limited. Persson, S. (1987). Mechanics of Cutting Plant material. Michigan: ASAE, St. Joseph, MI, USA. Prasad. J. & C.P. Gupta (1975). Mechanical properties of maize stalk as related to harvesting. Journal of Agricultural Engineering Research, 20(2), Saheed, O.A. (2001). Design and construction of rotary plantain slicer, Unpublished B.Tech Hons) project. Department of Food Engineering, Ladoke Akintola University of Technology, Ogbomoso. 142 Chilakpu et al., Development and Evaluation