Comments and corrections for the machining economics optimization article by Duffuaa, Shuaib and Alam

The article by Duffuaa, Shuaib, and Alam (1993) basically compares 4 nonlinear programming methods in solving the classical machining economics problem which always contain nonlinear terms both in the objective function and in some of the constraints. To do so, 5 problems from the previous literature are resolved. It is assumed that these models were accurately reproduced from the original sources. Researchers must realize that optimal cutting speed is meaningless when it comes to actual production. The lathe or drill has no control knob which says cutting speed. Instead, it is the revolutions per minute or the spindle speed which can be set on all machine tools including the mills. Details are provided.