Development of a hand operated maize sheller

INTRODUCTION

Maize (Zea mays) is one of the most important cereal crop grown in the world, it belongs to a grass family (Gramineae) and originated from Mexico and South America. In Nigeria, it is the most important cereal crop after sorghum and millet[1>] and this crop is grown as one of the efficient species domesticated by man.[2>] The period between planting and harvesting of maize depends on variety, but in general, the crop physiologically mature 7–8 weeks after flowering, at that time the kernel contains 35–40% moisture and has maximum content of dry matter.[3>] Table 1 below shows some physical parameters of maize processed corn is used in manufacturing of many products ranging from breakfast foods, corn meal flower and grits, starch, corn syrup, corn-oil, spirits, acetone, chemical, absorbent, seed, and silage. The demand in maize in Nigeria is been fuelled by the continuous grown been witnessed in the poultry and beverage sectors where they are used as raw materials, as animal feeds and human consumption.[4>] Maize is a stable food crop for most very sub-saharan Africans of which Nigeria is inclusive with per capital kg year of 40.[4>] A large quantity of maize is needed to meet the need of the agro-allied industries in providing the afore-stated items for the use and survival of humanity. It is because of the importance of maize that it is processing and preservation to an optimum level must be analyzed. The major step involved in the processing of maize includes harvesting, drying, dehusking, shelling, storing, and milling. For rural farmer to minimize their profit from their maize, appropriate technology that suites their need must be used. The processing of agricultural product like maize into quality form not only prolongs the useful life these but also increases the net profit of the farmers make from mechanization technologies.

Table 1: zPhysical parameters of maize grain

Maize Shelling

Maize shelling is the separation of maize grain from the cobs by initial impact or rubbing against a material. The difficulty of the process depends on the varieties grown, the moisture content, and the degree of maturity of the crop.[4>] Maize shelling is difficult at a moisture level above 25% with the moisture content, grain stripping efficiency is very poor with the high operational energy and causing mechanical damage to the seed. The high cost of tractor operated maize sheller has made it unbearable for the use of peasant farmer for their maize processing, instead, traditional methods were used with time consuming and high energy requiring demand.

Maize is shelled traditionally by hand; this is done by rubbing the maize against each other until the grains are removed from the cob. However, this traditional method of shelling is highly tedious, inefficient, and time consuming with low productivity as workers can only shell view kilometer per hour.[4>] However, the modern way of shelling is by the use of mechanical means,[5>] observed that manual shelled maize is time consuming and tedious and few existing mechanized sheller are imported and out of reach to small peasant farmers that are characterized by low income and small farm holding.

METHODOLOGY

Design Consideration

The design considerations include the design criteria and the functional requirement of the machine:

Design criteria

The design criteria consist of the following;

Functional requirement

The functional requirements of the machine include:

Description and Design of Machine Parts

The machine was designed to work on the principle of friction between the maize and the steel due to the sudden push from the weight of a falling shaft on the shelling cone. It is made up of six (6) major units as in Figure 1 below namely:

Figure 1: Assembly of developed machine

Mode of Operation

The machine is a simple design that requires little or no knowledge of engineering for utilization, the respective components and materials are shown in Table 2 below. To operate this machine, unshelled maize is placed carefully in the shelling cone. The operator takes hold of the pressing shaft and applies a downward pressure or force. This pushes the shelling shaft which also bears the shelling cap to press on the maize in the shelling cone. The force been applied pushes the maize cob into the cone, but the grains are shelled away. The shelled grains fall into the shelling unit where they are conveyed towards the outlet for collection.

Table 2: Summary of materials for respective components of the machine

Performance Test

A performance test was carried out on the hand operated machine and compared with hand shelling (HS) method; men and women that weighed 60–70 kg were given a known weight of unshelled cobs with <10% moisture content. The developed machine was used for shelling for 1 h, and the not well shelled cobs were weighed. This was replicated five (5) times. The same procedure was run through, using HS method and results were recorded.

Evaluation Parameters

This includes shelling speed, shelling force, required shelling power, throughput capacity, and the efficiency of the machine.

RESULTS AND DISCUSSION

Maximum Shelling Speed

V = d/t = 0.26/1 = 0.26 m/s

Maximum Shelling Force

Maximum Shelling Power

P = f×v = 0.09×0.26 = 0.002NMS^-1

Table 3 gives the efficiency and throughput capacity of the developed maize sheller, while Figure 2 is the graphical illustration of the same. The highest throughput value was obtained at the second replicate and had an overall average throughput value of 163 kg/h. The overall mean efficiency was 97.4%.

Table 3: Performance of hand operated maize sheller

Figure 2: A graph of efficiency and throughout capacity of the developed maize sheller

Table 4 gives the efficiency and throughput capacity of HS method. The highest throughput value was at the third and fifth replicates, while the overall mean throughput value was 35.05 kg/h. This method had a mean efficiency of 98.6%.

Table 4: Performance of hand shelling method

Figure 3 shows the comparison of the throughput values of both shelling methods. The result suggests that the developed maize sheller with a means throughput capacity of 163 kg/h performs approximately 5 times faster than HS with a mean throughput capacity of 35.05 kg/h.

Figure 3: A graph showing comparison of throughout values

Figure 4 is the graphical illustration of the efficiency of the developed hand operated maize sheller and HS method. It shows that their efficiencies were relatively close; the former had a mean efficiency of 97.4% while the latter had a mean efficiency of 98.6%.

Figure 4: A graph showing the efficiencies of the two methods

CONCLUSION

The developed hand operated shelling machine was tested for performance and evaluated; the result was compared to a HS method. It had an overall mean throughput value of 163 kg/h, while the hand method had a mean throughput capacity of 35.05 kg/h. This suggests that the developed sheller is 5 times faster than hand method. They have a relatively close efficiency values of 97.4% and 98.6%; this suggests that they both would reduce losses.