Optimising drill performance has always been a primary goal of
drilling and blasting managers. Improving drilling rates and
utilisation will ultimately drive the cost per foot or metre
downward. Additionally, more consistent production will ensure
shovel or dragline performance goals are met and the chances of
machine idle time is minimised. Over the past 20 years, many
studies have examined rotary drilling factors and performance
issues. In most cases a common theory points to energy input
versus drilling output. Indexes such as specific energy and total
work energy have been -developed to quantify the drilling
process. As general engineering principles dictate, energy is
required to drill rock by overcoming compressive and shear
strengths. Concurrently, the greater the energy input, the faster
the penetration output. Therefore, by examining the basic drilling
energy parameters, optimisation is possible. The principles of rotary drilling are driven by five factors.
When optimised individually and as a system, drill performance
will improve. Most recent studies all agree that a performance
relationship exists between bit load, bit rotation, and hole
flushing. Additionally, proper bit selection and most of all, the
operator, can have a tremendous effect on drill productivity. By
analysing these factors and establishing the best case scenario, an
overall drilling system can be engineered to match the mining
characteristics. Furthermore, by balancing these factors, a lower
cost will be achieved through increased production rates,
maintenance costs, and effective drill utilisation.