This paper presents experimental studied results about surface roughness during end milling SKD11 steel under room temperature and work-piece preheated condition. Conventional samples were first performed. The samples which are same technical parameters were then performed at elevated temperatures to evaluate effective of heating process on the surface roughness. Orthogonal array Taguchi method was used to experimental design. The results showed that the surface quality of product was significantly improved under thermal - assisted milling. The surface roughness model during machining at room and elevated temperatures were evaluated and showed a good agreement with result of experiments.

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