Power = ( specific power )( material removal rate )
P = Ps ( mrr )
For the slab milling and surface grinding processesP = Ps ( doc )( woc )( tfr )
mrr = ( depth of cut )( width of cut )( table feed rate ).
The width of cut can be the tool width or only a part of it.
Only a part of the tool width can be used, e.g., in using only a portion of the width of a grinding wheel in surface grinding and stepping across the workpiece in a number of grinding passes.
The table feed rate is usually determined based on the desired chip load. In milling the chip load or bite per tooth is the maximum amount of material removed by each cutting edge, e.g., in mm/tooth. The concept is similar for grinding but the amount of material being removed at any instant is the average amount of material removed by a number of abrasive grains that extend above the wheel "surface" by varying amounts.
With the given milling process parameters and power, Pmilling, the unit power, Ps milling, for the milling process can be calculated.
Ps milling = Pmilling / [ ( doc )( woc )( tfr ) ]milling
Adjusting the grinding process parameters to obtain a known power, Pgrinding = Pmilling, the specific power for the grinding process can calculated.
Ps grinding = Pgrinding / [ ( doc )( woc )( tfr ) ]grinding
For the process parameter values given in terms of units of mm, mm/min and kW the specific power unit is kW / [ mm3 / min ].
The exercise and the power equation show that the process power depends linearly on all of the process parameters.