All over the world, additive and subtractive manufacturing are the two basic manufacturing methods used for the development of engineering goods and products. In most cases, the method adopted by the manufacturers usually depends on its cost-effectiveness. However, most of the manufacturing industries in Nigeria have little or no information on the relative advantages and disadvantages of the two methods. This had led to many industries adopting one particular method hook, line and sinker without considering the merits that would be offered by the alternative manufacturing method. This paper, therefore, compared the two methods of manufacturing by carrying out reverse engineering of worn-out helical gears (components of a juice extractor) developed using additive and subtractive manufacturing techniques. The parts of the equipment were developed using a lathe, milling and deburring machines to carry out the drilling, turning, grinding, milling and deburring for subtractive manufacturing and 3-D printing machine for additive method. Two gears A and B were developed by both subtractive and additive methods using the dimension of two old gears, which serve as the basis for determining the variation of the nomenclatures of the developed gears from the standard. The time used for product development, cost of production and the energy expended during the production of the two gears using additive and subtractive manufacturing methods were also determined using appropriate methods. The study also showed that it is less expensive to produce both gears A and B using the additive method than the subtractive method. Similarly, in term of energy used, less energy was used during fabrication of the gears using additive method than subtractive method but in general, when you want to print a whole component at once the 3D printer volume could be a major constraint. Hence, the adaptation of additive manufacturing method as a whole or part with the existing subtractive method will help to improve manufacturing industries in Nigeria.

The need to enhance the quality of fish feed produced in Nigeria was the major consideration in the design and development of a preconditioning system. The machine consists of two insulated cylindrical barrels, set of arranged paddles on a shaft, frame, hot water and feed mash inlet, discharge chute, chain and sprocket. It was powered by a three-phase 15 hp electric motor which transmits power to the machines shaft and set of paddles via chain and sprocket. The performance characteristics of the machine; mixing efficiency and throughput capacity were evaluated using Nigerian Institute for Oceanography and Marine Research (NIOMR) feed formulation at feed mash particle sizes of 900 µm, 550 µm, 520 µm and paired paddle rotating speed of the lower and upper chamber at (96.8; 145.2), (122.6; 183.2) and (174.5; 260.8) rpm respectively. The throughput capacity of the preconditioner is 650 kg/hr. The results showed increase in temperature and moisture content level of the particles as the machine speed decreases. The optimum mixing efficiency that gave best uniformity of mix was attained when Paired paddle speeds were (96.8; 145.2), (122.6; 183.2) with an average Biot numbers of 0.1.

A continuous process power driven gari fryer was designed, fabricated and tested at the Federal Institute of Industrial Research, Oshodi. (FIIRO), Lagos, to fry large quantity of cassava mash using locally available materials. The fryer which consists of major two sections; one to gelatinize cassava mash while the drying of the mash take place in the other section. The essential components of the fryer include feeder, frying troughs, rotating paddle arrangement, central shaft, coupling, top cover, gas burners, discharge sprout, main frame, insulation wall, sprocket and internal combustion engine. In operation, the rotating paddles convey the cassava mash during the gelatinization and drying process from the feeding point to the discharge sprout to obtain finished gari product. At constant speed of 8 rpm, the result showed that the time of frying ranged between 14 minutes to 17 minutes with an output of 83.2 kg/hr while the percentage yield of gari obtained ranged from 52.8% - 74.7%. Thus it is established that the capacity of the fryer is 500 kg per day as against the manual method of frying where 5 kg of gari is obtained within 30 minutes (80 kg/day) for 8 hours frying operation in local cassava processing industry in Nigeria. Hence, this makes the fryer to be suitable for gari production for small to medium scale enterprise.

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