Improving the Machined Surface of AISI H11 Tool Steel in Milling Process

Several challenges are faced by manufacturers producing the best surface finish, especially for the mold and die applications. Most of the mold and die materials are made from hardened steel (~40-60 HRC). The high strength of these materials reduced the capability of the conventional machining technique. High tool wear rate and poor machined surface are among the problems associated with traditional machining. To overcome these problems, this study proposed a hybrid machining process by adding axial ultrasonic vibration to the regular tooling system, namely ultrasonic vibration-assisted milling. Experimental work consisted of comparing ultrasonic vibration-assisted milling and conventional milling for different parameters, namely cutting speed, feed rate, and a milling depth of cut, to validate the proposed technique’s effectiveness in enhancing the value of machined surface roughness for hardened AISI H11 tool steel. The milling tests revealed that axial ultrasonic-assisted vibration significantly improved the machined surface roughness with up to 89.7% reduction in Ra value than the conventional milling process with the same cutting conditions. The macroscopic observation of the machined surface showed that the surface produced from ultrasonic milling was uniform with a consistent peak to peak value which improved the surface finish.