DESIGN AND PERFORMANCE EVALUATION OF AN EJECTION MECHANISM FOR CEMENT-STABILISED BLOCKS IN AN IMPACT MOULDING MACHINE

Cement-stabilised blocks, when compacted using an impact-type moulding machine, are often difficult to eject due to high adhesive resistance between the block and the mould walls. This study presents the design and performance evaluation of a manually operated ejection mechanism for cement-stabilised blocks in an impact moulding machine. The mechanism employs a compound gear train, comprising 2:1 bevel gears followed by 3:1 spur gears, to drive a power screw capable of overcoming the 84.7 kN adhesive interface force. Ergonomic considerations were incorporated by adopting a maximum manual input force of 200 N, consistent with recommended sustained human effort, and a crank length of 0.37 m, derived from anthropometric data of Nigerian male workers. A removable breaker bar of 0.6 m radius was introduced to keep short-burst forces within safe two-hand operation limits during block–mould separation. With these provisions, the required 1737 Nm breakaway torque at the screw is achieved using 289.5 Nm input torque in short bursts and 74 Nm during sustained ejection. The system delivers an average ejection speed of 51.62 mm/min, with a total ejection time of 15.8 minutes per block. While safe and manufacturable for small-scale or off-grid use, mechanisation is recommended to improve throughput.