Design and Development of Mini-Maize Cob Threshing Machine

Abstract

Maize is one of the most important cereal crops in the world agricultural economy due to its significance in human and animal diets. The area under maize cultivation and production continuously increases. Traditionally, maize was dehusked-shelled manually, which is very tedious, drudgery, labor-intensive, and time-consuming. The machines available in the market for maize threshing are generally larger (in size) and more costly. But in India, over 75% of farmers belong to the small and marginal category. We developed this compact, economical ‘Mini-Maize cob Threshing Machine’ for small and marginal farmers to perform dehusking and shelling operations simultaneously. The average grain output obtained by the developed machine was 271 kg per hour with a shelling efficiency of 98.9%, and a 2 HP power source operated the machine.

Introduction

Importance of Maize:

• Maize (Zea mays L.) is a critical cereal crop globally, often called the “Queen of Cereals” and “King of Fodder.”

• It originates from Mexico and is vital for human and animal consumption.

• It accounts for 38% of global grain production, with the USA as the top producer (43%) and India ranking 7th (2.4% of global production).

• Andhra Pradesh is the largest maize-producing state in India, followed by Karnataka, Rajasthan, Maharashtra, and Bihar.

• Maize is grown in all three agricultural seasons, mainly kharif, and has a high yield with average productivity of 2.43 tons/ha in India.

2. Need for Threshing Technology:

• Threshing and dehusking are essential to separate grains from maize cobs.

• Manual shelling is laborious and yields just 9.12 kg/hour.

• Existing power-operated threshers are too large and costly for small and marginal farmers, who make up over 75% of India’s farming population.

• Most available machines require high horsepower and are suited for large-scale farming.

3. Objective of the Study:

• Design and develop a mini-maize cob threshing machine for small-scale farmers.

• Study the engineering properties of maize cobs and grains.

• Evaluate the machine's performance in terms of efficiency and throughput.

4. Literature Review Insights:

• Optimal blower air velocity for separation ranges between 1.2 m/s to 15.12 m/s.

• Concave clearance and peripheral speed should be 20–30 mm and 9–12 m/s, respectively.

• Energy consumption for threshing is 2–3 tons per kW per hour.

• Preferred hopper design is trapezoidal/rectangular with a 1.6 mm thick MS sheet.

5. Engineering Properties Measured:

• Roundness, sphericity, bulk density, true density, moisture content, angle of repose, and terminal velocity were all measured to inform design specifications.

• These values help optimize machine parts for better performance and minimal grain damage.

6. Machine Design and Construction:

Main Frame:

• Trapezoidal-shaped mild steel frame, dimensions: height 575 mm, front width 415 mm, etc.

Power Source:

• Designed to run on a 2 HP electric motor, with maximum feed rate of 750 kg/hour.

Threshing Cylinder:

• Axial flow design for longer cob retention and better shelling.

• Diameter: 154 mm including bars, effective diameter: 140 mm.

• Two circular bars (7 mm diameter) positioned at 180°, preferred over square bars to minimize grain damage.

7. Existing Machinery Comparison:

• PAU Ludhiana: Developed a 26.1 KW tractor-operated maize sheller with 15–20 quintals/hour capacity and 100% shelling efficiency.

• MPUAT Udaipur: Designed a whole-crop thresher that also chops stalks into fodder with 99% threshing and 96.4% cleaning efficiency.

8. Justification and Relevance:

• Most small farmers grow maize both for grain and fodder, hence need low-cost, compact threshers.

• Maize production in India has grown 16-fold from 1950 to 2018–19, reinforcing the need for efficient post-harvest tools.

Conclusion

1) The machine was able to perform dehusking and shelling simultaneously. 2) The developed Mini Maize Cob Threshing Machine worked reliably, and the result obtained was satisfactory. 3) It was found that at the full opening of the feed control shutter, the feed rate was 400 kg per hour and the grain output capacity was 271 kg per hour, so this machine will be suitable for small and marginal farmers. 4) The developed machine was very compact and economical. 5) This machine separates only grain with minimum disturbance to cob (body), so it was found very energy efficient (271 kg per hour of grain output obtained from 2 HP power). 6) Easy to operate and maneuverable from one place to another.

References

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Copyright

Copyright © 2025 A. R. Kinge, T. B. Bastewad , S. C. Bhangare, P. R. Sapkale , R. K. Rathod, J. K. Khurdal, S. M. Nalawade. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.