Experimental testing of a tubular linear permanent magnetic machine for percussion drilling in hard rocks
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A Tubular Linear Permanent Magnetic Machine (TLPMM) performing percussion drilling, with percussion rates ranging from 20-71 Hz has been studied experimentally. It produces an oscillating motion when electrical power is supplied. This energy canbe used as a hammering force in a tool for percussive drilling. A rig where the TLPMM has been implemented was made so that test drilling couldbe conducted under controlled circumstances. Experiments were performed to determine the effect of increased percussion rate vs.rate of penetration, as well as finding the optimum operation point where highest possible ROP is achieved at lowest possible specific energy. Maximum penetration rate was achieved at 71Hz frequency with bit size 6mm,drilling 65mm/min. The lowest specific energy achieved was for drilling at 40Hz at 6,4J/mm3 and 33mm/min penetration. The rate of penetration increases when percussion rate is increased, but a clear linear correlation has not been found for the percussion rates within the 20-71Hz range.