Drilling of polymeric materials can be challenging when holes are produced in large scale due to the necessity of controlling the holes quality. This paper presents the effect of machining parameters on the hole quality, in terms of surface roughness and circularity error, in drilling of high density polyethylene, polyamide and polyacetale. The analysis of variance was performed in order to assess the significance of cutting parameter on the hole quality parameters. The experimental results indicate that different cutting conditions are to be employed in order to achieve the optimum surface roughness and circularity.

Sandwich panels with composite/steel skin sheets and foam core are very often used as lightweight structures in automotive, maritime and aerospace applications due to their performances like high bending stiffness and strength and also lightweight. As an alternative to classical structural reinforced panels, the sandwich structures are justifying their use in various industrial fields, making these structures less complex, by eliminating the need for secondary stiffening. In the paper are presented three models of sandwich, steel-foam-steel, composite-foam-composite or steel-foam-composite structures, of different thicknesses, with functional use in various fields depending on necessities. The mechanical characteristics of the materials used in their manufacture have been determined. The panels have been subjected to various load cases in order to determine an optimal combination of weight and strength. At the same time, the numerical models used in the finite element analysis of the sandwich structures with specific elements for layered composites or sandwich (SHELL 4L and SOLID L) are presented.

Polymeric materials are synthetic macromolecular products, of which, by mechanical or thermal processing, objects of various shapes can be obtained, with wide uses in industry and commerce. This paper deals with the roughness of surfaces obtained during drilling of three polymeric materials: polyamide - PA6, polyacetal - POM-C and high density polyamide - HDPE 1000. In the experimental research was used a EMCO MILL 55 milling machine numerical controlled and HS steel helical drills with two straight cutting edges with the diameter of �8 mm and �10 mm, respectively. Experimental determinations consisted in drilling of the polymeric materials by modifying some parameters of the cutting regime, and determining the roughness of the surface of the holes machined, using the Mitutoyo Surftest SJ-210 rough meter. The purpose of the paper is to predict the roughness of the machined surfaces as one of the important surface quality indicators by using a geometrical model and an artificial neural network (ANN) methodology.

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