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Precision Engineering / Micromachining / Metrology


New Micro and NanoManufacturing

 Precision Turning

Precision machining and micromachining aims the production of advanced components with high dimensional accuracy and acceptable surface integrity. Fiber reinforced composites are widely employed in various fields of engineering, such as aircraft, automobile, robots and machines due to their good properties. This work aims the better understanding of the machinability of PA 66 polyamide without and with 30% glass fiber reinforcing, when  precision turning at different feed rates, cutting speeds and using various tools materials. The performance of PCD, CVD diamond coated, K15-KF and K15 carbide cutting tools and the influence of feed rate and cutting speed on cutting forces, surface roughness and micro-chip formation were investigated for polyamide composites, whereas, performance P25  and K15 carbide cutting tools were investigated for AISI D2, AISI 4140 and AISI 1045 steels. The findings for polyamide composites indicated that the radial force component presented highest values, followed by the cutting and feed forces. The PCD tool gave the lowest force values associated with best surface finish, followed by the ISO grade K15 uncoated carbide tool without chip breaker. Continuous coiled micro-chips were produced, irrespectively of the cutting parameters and tool material employed. The addition of 30% glass fiber reinforcing significantly affected the performance of the tooling used in comparison with the material without reinforcing. The results for steels  indicated that, in general, the turning force components increased as feed rate is elevated and the specific cutting force decreases strongly with feed rate when cutting AISI D2 steel, however, for the  machining of AISI 4140 and AISI 1045 steels the specific cutting force decreases slightly or remains unaltered as feed rate is elevated. Finally, the surface roughness produced by the two cutting tools was significantly affected by feed rate within the range tested. Best surface finish was obtained when turning the AISI D2 steel followed by AISI 4140 steel.

Figure 1 - Effect of feed rate on cutting force when machining PA66-GF30 composite at vc = 70 m/min and ap=150 mm with CVDD, PCD, K15 and K15-KF tools.

Figure 2 - Effect of feed rate on cutting force when machining AISI D2; AISI 4140 and AISI 1045 steels at vc = 100 m/min and ap = 100 mm using uncoated (K15) cemented carbide tool.


The demand for miniaturized devices with high aspect ratios and superior surfaces has been rapidly increasing in aerospace, automotive, biomedical, optical, military and micro-electronics packaging industries. There is a growing need for fast, direct, and mass manufacturing of miniaturized functional products from metals, polymers, composites and ceramics. In the present work, the machining of micro surfaces on aluminum alloy is made, using conventional machines and commercially available miniature tools. With the aid of CAD (Computer Aided Design) software, several micro surfaces were designed to test their machinability on a conventional CNC (Computer Numerically Controlled) machining centre using sub millimeter tools. In order to perform a comprehensive study on the quality of the machined surfaces (roughness, accuracy and burrs), machining parameters such as feed rate were varied. Also, a variety of machining strategies was performed in order to study the quality of the machined surfaces. Hence, the thesis’ main goal is to determine up to which extent conventional machines and micro tools can be used to achieve quality micro surfaces. In Fig. 3 one can see the photograph of a micro-milled surface on aluminium stock using a 0.8 mm diameter end mill.

Figure 3 - Photograph of micro-milled aluminium surface using a 0,8 mmm end mill compared to a0,5 mm pencil lead

After the design of the different surfaces using 3D modelling software, the experimental work took place. Several cases of study were conducted for each designed surface, varying the feed rate and machining strategy. The analysis of the finished surface consisted in measuring its roughness with a profilometer and measuring the minimum wall thickness achieved without burrs.


MACTRIB - Department of Mechanical Engineering , University of Aveiro

Campus Universitário de Santiago, 3810-193 AVEIRO, PORTUGAL

Tel: + 351 370 830, Fax: +351 234 370 953