4M Knowledge base - papers

A. Herreroa, L. Uriartea, J. Esmorisa, J.A. Sánchezb, L.N. Lopez de Lacalleb
a Fundación Tekniker, Avda. Otaola 20, 20600, Eibar, Spain
b Dpto. Ing. Mecánica, ETSII, Alameda Urquijo s/n, 48013, Bilbao, Spain

Abstract

The analysis of WEDM is still nowadays an important field of research due to the difficulties to measure the process characteristics: narrow gap (~10 mm), dirty environment (oil or deionised water), high frequency (>100 kHz), etc. Nevertheless, the WEDM technology has been improved thanks to the theoretical and empirical results of different research groups that have made use of state of the art technologies to measure temperature distributions, displacements, frequencies or electrical signals for spark characterisation. The accurate measurement of machined parts has also brought light to the machining process, being this aspect critical for the improvement of the EDM technology.

In the last years, the growing tendency to miniaturisation has promoted the research of production techniques capable to produce small components with very high precision. EDM technology, due to the low processing forces, was immediately identified as one applicable technology for the production of moulds and dies. The technological research in the field has been very important, reducing the minimum wire diameter from Ø0.1 mm to Ø0.02 mm, the machine components have evolved to provide a finer control of all process parameters, specially the wire traction force, the machine feed and the spark energy. Thanks to the research in WEDM, nowadays it is known that, during the process, electrostatic, electrodynamic, electromagnetic, dielectric and wire traction forces act on the wire. Many of these forces push and pull the part from the workpiece. The result of all these forces acting on the wire is an error of the machined shape that, in normal WEDM, is of only a few microns (3~20 mm depending on part height). This error is specially important when machining flat walls and machining corners in which the feeding direction change.

Despite using lower energy values, due to the origin of the different forces acting on the wire and the low tensile strength of wires smaller than Ø0.1 mm (considered as thin wires), the errors that can be found in miniature parts and microparts are bigger than the corresponding values in conventional WEDM. The present paper analyses the errors that appear when applying thin wire EDM (Ø0.03 mm) to the machining of 3 mm height components made of tungsten carbide, it presents the difficulties that are found when trying to characterise the errors in small components. A possible error analysis approach is presented and then the errors are discussed.

R. Teti (a), L. Mattsson (b), Andrej Lebar (c), Mihael Junkar (c)

a Department of Materials and Production Engineering, University of Naples Federico II, Piazzale Tecchio 80, 80125 Naples, Italy
b Department of Production Engineering, KTH – the Royal Institute of Technology, SE-10044 Stockholm, Sweden
c Laboratory for Alternative Technologies, Faculty of Mechanical Engineering, University of Ljubljana, Askerceva 6, SI-1000 Ljubljana, Slovenia

Abstract

In this paper, the characterisation of micro-features involved in metrology applications within the scope of 4M is carried out through the use of different two-dimensional frequency analysis procedures. Firstly, the analysis methods are introduced and their basic principles are illustrated. Secondly, selected test cases, representing the issue of experimental research activities performed at the laboratory sites of the co-author’s partner organisations, are presented with reference to diverse metrology purposes in different fields of applications.