Experimental study of micromilling burrs of 304 stainless steel

Stainless steel is a well-known difficult-to-machine material with high toughness, low thermal conductivity, and high work hardening characteristics. Burrs generated in micromilling of the stainless steel seriously affect the performances of the fabricated high-accuracy miniaturized geometrical features. Aiming at reasonable control of burrs in micromilling of the 304 austenitic stainless steel, single-factor analyses, multi-factor optimization, and further post processing procedures are introduced in the paper. First, the axial depth of cut a(p), feed per tooth f(z), spindle speed n, and radial depth of cut a(e) are investigated by single-factor micromilling experiments. It shows that burrs generated in up milling are smaller than that in down milling. The minimum burr widths of 171.93 mu m can be achieved, and the overall trend of micromilling force is in accordance with the burr widths. Then, multi-factor orthogonal experiments have been carried out to optimize micromilling parameters based on the Taguchi method. It shows that the significance sequence of key parameters for burr widths from large to small is a(p), n, a(e), and f(z). The optimized minimum burr width is 83.69 mu m with micromilling parameters a(p) of 45 mu m, f(z) of 1.0 mu m/z, n of 48,000 min(-1), and a(e) of 200 mu m. To further reduce the burrs, a(p) of 0 is set for post processing experiments. It shows that the radial depth of cut affects burr sizes greatly. The optimized radial depth of cut is 500 mu m, and burr widths have been finally reduced to 14.3 mu m. The study provides an effective method to reduce burr sizes in micromilling of very ductile materials.