Selection of Parameters and Strategies to Reduce Energy Consumption and Improve Surface Quality in EN-AW 7075 Molds Machining

The machining of cavities for blow molding is a long and costly process, with the objective of obtaining an excellent surface finish with the minimal possible electrical energy consumption (EEC). This work has studied which combination of cutting parameters and cutting strategies to use to achieve an optimum surface finish on the mold using the minimal associated EEC: in roughing operation, tool path strategy and axial depth of cut were studied; in finishing operation, tool path strategy, spindle-speed, feed-rate, and step-over were evaluated. Thirty-two molds were machined in blocks of aluminium alloy EN-AW 7075 T6 in a machining center of a three-axis, following an orthogonal design of experiments. The analysis of results demonstrates that: a roughing strategy has influence on the surface roughness on the bottom of the mold; a finishing strategy is an influential factor on the surface roughness on the walls of the mold; certain parameters have no relevance on the surface roughness but have an influence on the EEC; an adequate selection of cutting strategies and cutting parameters permit an improvement of surface roughness of up to 70%, and a reduction of 40% in EEC, compared to the less favorable tests.