Tool wear and spring back analysis in orthogonal machining unidirectional CFRP with respect to tool geometry and fibre orientation

Abstract

Machining abrasive carbon fibre reinforced polymers (CFRP) is characterised by extensive mechanical wear. In consequence, the cutting edge micro-geometry and thus the tool/material contact situation are continuously changing, which affects process forces and machining quality. As a conclusion, a fundamental understanding of the tool wear behaviour and its influencing factors is crucial in order to improve performance and lifetime of cutting tools. This paper focuses on a fundamental tool wear analysis of uncoated tungsten carbide cutting inserts with different combinations of fibre cutting angles and tool geometries. For this purpose, orthogonal machining experiments with unidirectional CFRP material are conducted, where the wear progression of the micro-geometry is investigated by means of five wear parameters lα, lγ, γ*, α*, and bc. For detecting the actual contact zone of the cutting edge and to measure the elastic spring back of the material, the flank face is marked via short pulsed laser processing. Furthermore, the process forces and the wear rate are measured. It is shown that the material loss due to wear clearly varies along the tool’s contact region and is highly dependent on the clearance angle and the fibre cutting angle Φ, while the influence of the tested rake angles is mostly negligible. Especially in machining Φ=30° and Φ=60°, a strong elastic spring back is identified, which is more intense for smaller clearance angles. For all tested configurations, the material’s elastic spring back increases in intensity as wear progresses which, in combination with the decreasing clearance angle, is the main reason for high thrust forces.

Wear Study of Coated Mills during Circumferential Milling of Carbon Fiber-Reinforced Composites and Their Influence on the Sustainable Quality of the Machined Surface

“…Machining composite materials is different and challenging. The choice of suitable cutting tools and cutting conditions requires experience in chip machining [7,8].…”

Analytical model for predicting tool wear in orthogonal machining of unidirectional carbon fibre reinforced polymer (CFRP)

“…As the value of b c increases much faster than t c , the actual depth of cut increases as tool wear progresses, which means that previously untouched rake and flank face material of the cutting tool gradually gets in contact with the CFRP [8,36]. This is illustrated in Fig.…”

Experimental Procedure to Study the High Speed Orthogonal Cutting of Unidirectional GFRP

“…According to Panico et al [4], the machining of FRP composites present challenges due to the heterogeneity and anisotropic properties of the material, leading to the chip formation mechanisms and process force analysis dependent on the cutting angle of the fibres, as evidenced by various experimental studies [5][6][7][8][9]. In addition, the abrasive nature of the fibers causes rapid and severe wear of the tools, resulting in increased cutting forces, delamination defects, burrs, and a decrease in the quality of the machined surface, as demonstrated by Maegawa et al [10] during the milling of 2 unidirectional (UD) CFRP material.…”