Abstract
The market demand for machining and cutting of various plastics parts is in continuous in- crease. The aim of this study is to extract prediction laws for surface roughness, cutting forces and tem- peratures evolution during the machining of two polyethylene pipes grades (HDPE-100) and (HDPE-80). It was found that feed rate is the most prevailing factor on roughness criteria and that better surfaces are obtained during the machining of the harder HDPE-80 resin. Also, cutting speed improved surface quality for speeds up to 200 m.min −1 but the rising interface temperature caused surface damage and material rapid softening. Also, feed exponents, in mathematical models, were found to be 3 to 4 times higher than those of cutting speed and depth of cut. An increase in the cutting speed led to a gradual reduction for the 3 cutting forces components (Fr, Fa and Fv ) with a dominance of the tangential force (Fv ). As ex- pected, the value of the depth of cut had a large influence on the temperature within the cutting zone. This temperature is slightly higher during the machining of HDPE-80 compared to that of HDPE-100 most probably because of hardness differences. The analysis of variance (ANOVA) was performed to check the adequacy of the mathematical models relating cutting parameters with roughness, cutting forces and global cutting zone temperature.
Highlights
The machining of polymeric materials, by chips removal, must take into account manufacturing conditions, material characteristics, applied stresses and the usage environment, as well as the interactions between these various criteria especially in terms of heat generation
Roughness profiles obtained for different values of feed rate (Fig. 2) show a regular periodicity for feed rate above 0.14 mm.rev−1, while for 0.14 mm.rev−1, surface grooves are so small compared to material wrenching; so that profiles lose their periodicity and become rather random
Similar results are found by Xiao and Zhang for High density polyethylene (HDPE) and LDPE as surface roughness decreased with the cutting speed and the increase in shear stress indicates that a greater mechanical strength usually results in a better surface finish when cutting very soft polymers having high molecular segments mobility [9]
Summary
The machining of polymeric materials, by chips removal, must take into account manufacturing conditions, material characteristics, applied stresses and the usage environment, as well as the interactions between these various criteria especially in terms of heat generation. In 1993, Carr and Feger presented an exhaustive study of the effect of material properties on the surface roughness of several polymers with different Tg values and molecular weights, when subjected to single-point diamond machining [6]. They analyzed the relationship between the minimum polymer roughness and the tool speed based on the time–temperature superposition principle, and found that the surface roughness would decrease initially when the tool speed is increased because of a limited transition towards a ductile fracture mechanism. An analysis of variance (ANOVA) is performed to check the adequacy of the mathematical correlation models
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