The overall energy consumption was assessed by analyzing the
average electricity usage while drilling 500 holes. For every 500
holes, a response surface was constructed from measured values
using least-square error methods with quadratic models, and fourpoint
interpolation was carried out while drilling 2000 holes (an
industrial standard for regrinding a tool tip for reuse under the
reference conditions). The data were used to construct continuous
charts in terms of drilling hits. Fig. 6 shows the integrated electricity consumption measured while drilling 2000 holes, and a
numerical graph obtained by substituting the percentages from
Figs. 3 and 4 into Equation