Manufacturing of testing specimens from tough HDPE-100 pipe: Turning parameters optimization

Abstract

Numerous machining operations are required in order to manufacture standard and non-standard specimens for mechanical testing of polymers. The present work focuses on the machinability of HDPE-100 pipe to prepare the utmost regular filaments with specified thickness and width. The study is set to establish mathematical correlations between surface quality (total roughness; Rt), cutting temperature (T°), filament uniformity (L) and corresponding cutting conditions. The latter include Vc (cutting speed), f (feed rate) and ap (depth of cut), combined with tool geometry (i.e., rake angle: γ and cutting-edge angle: κr). A mixed Taguchi L18 plan is adopted to organize and process the experimental runs. ANOVA and RSM (Response Surface Methodology) are employed to construct prediction models and optimize subsequent machining results. It is found that T (cutting temperature) and surface roughness criteria (Ra, Rt) are strongly affected by f and Vc. In addition, ANOVA results related to the height of filament bends (L) are likewise studied as a function of tool angles γ and κr. It is noted that cutting process is influenced by κr as it explains ~19% contributions of the total variation of parameter L, while γ, Vc and f show a little influence. It is deduced that optimum input parameters, represented by Vc, f, ap, γ and κr, are respectively 160 m/min, 0.5 mm/rev, 4 mm, (-6°) and 90° when turning tough HDPE material.