4M Knowledge base - papers

S. T. Chen(a), Y. S. Liao(b)
a: Department of Mechatronic Technology, NTNU, No. 162, He-ping East Rd., Sec. 1, Taipei, 106, Republic of China
b: Department of Mechanical Engineering, NTU, No. 1, Roosevelt Rd., Sec. 4, Taipei, 106, Republic of China

Abstract

The paper proposed a novel approach of effective production of mass micro holes. A set of micro w-EDM mechanism is designed and mounted on the developed tabletop precision machine tool. The tension of micro wire is precisely controlled by magnetic force. In addition, the micro vibrations of the wire during discharging are effectively suppressed by the developed vibration suppression system. In order to fabricate the mass micro holes, the microstructure array of the high aspect ratio 10×10 micro squared electrodes with the width and the height of 21μm and 700μm, respectively for each electrode, and the spacing between two electrodes of 24μm is fabricated first by the proposed “reverse w-EDM” machining strategy. This micro electrodes array is employed directly to machine the mass micro holes on the same machine via the modified micro EDM peck drilling. By sequentially positioning the micro electrodes array after one drilling through process, the 900 same size micro through-holes array is successfully obtained on the stainless steel board of 0.1mm thickness. The results show satisfactory hole geometry, dimensional accuracy and surface roughness. More, it is verified that the mass micro holes can be fabricated efficiently by the proposed approach.

G. Tosello(a), B. Fillon(b), S. Azcarate(c), A. Schoth(d), L. Mattsson(e), C. Griffiths(f), L. Staemmler(g), P.J. Bolt(h)
a: Technical University of Denmark (DTU), Department of Manufacturing Engineering and Management (IPL), 2800 Kgs. Lyngby, Denmark
b: French Atomic Energy Commission (CEA), Laboratory of Innovation for New Energy Technologies and Nanomaterials (LITEN), 38054 Grenoble, France
c: Tekniker Technological Center, 20600 Eibar, Spain
d: University of Freiburg, Institute of Microsystem Technology (IMTEK), 79110 Freiburg, Germany
e: School of Industrial Technology and Management (KTH), Department of Production Engineering, 100 44 Stockholm, Sweden
f: Cardiff University, Manufacturing Engineering Center (MEC), Cardiff CF 24 3AA, UK
g: Hahn-Schickard-Gesellschaft, Institute for Micro Assembly Technology (HSG-IMAT), 70174 Stuttgart, Germany
h: TNO Science & Industry, 5600 HE Eindhoven, The Nederlands

Abstract

This paper is based on the Division 4 “Processing of Polymers” activities within the 4M NoE “Multi-Material Micro Manufacturing”. To overpass limitations of the current existing micro tooling capabilities, a new generation of micro hybrid tooling technologies for micro replication was developed. A metrological approach was applied to standardize the employed tooling processes (μ-milling, μ-EDM, laser μ-machining, electrochemical μ-milling). The micro tools were then tested with different polymers. The paper provides a comparison of these technologies concerning obtainable feature sizes, surface finishing, and aspect ratios of both micro tools and micro moulded parts.

A. Herrero(a), J. Esmoris(a), S. Azcarate(a), S. Geissdoerfer(b), U. Engel(b)
a: Department of Micro & Nano Technologies, Tekniker, Avda. Otaola 20, 20600 Eibar, Spain
b: Universität Erlangen-Nürnberg, Egerlandstrasse 11, 91058 Erlangen, Germany

Abstract

The mass production of micro and meso scale products made of polymers or metals is intimately related to the production of high quality microtooling in stable materials capable to provide an accurate and repetitive performance throughout the whole demanded production. As it is widely known, the WEDM process provides high accuracy but is conceptually limited to the production of ruled features. The SEDM process can be a complement to this aspect but the electrodes must be manufactured by other technologies like WEDM, micromilling, turning, etc. Given the importance of several parameters like dimensional accuracy, tooling material for the different replication processes or tooling production technology, the present paper introduces some tests performed by the 4M Metals Workgroup. The analysis of some components manufactured by members of the group is presented discussing the influence of the EDM process on the machined tooling components and the consequent influence on the replication process.

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.

C. P-Withen (a), J. R. Marstrand (a), M. Arentoft (b), N. A. Paldan (b)
a Department of Manufacturing Engineering and Management, Technical University of Denmark, Produktionstorvet, Building 427, DK- 2800 Kgs. Lyngby, Denmark
b Institute for Product Development, Produktionstorvet, Building 425, DK- 2800 Kgs. Lyngby, Denmark

Abstract

The advantages of cold forging micro-components are the same as for conventional cold forging, namely the high production rate and the low material waste. To achieve this, a flexible tool system for cold forging of micro-components has been developed. When transferring the technique of cold forging from macro- to micro-scale, size effect and change in friction are conditions that have to be considered. Furthermore the precision of the tool system is crucial owing to the low tolerances on the dimensions of micro-components.

The tool system is designed for the eight basic cold forging processes with some replaceable process dependent parts. Furthermore it is possible to replace critical parts to reduce expenses if tool breakdown occurs. The system is tested by forging of an industrial component. The tool system is produced by micro-EDM and high precision machining.

The test of the final tool system shows that it can be used to cold forge micro-components. An Ø0.8mm rod is extruded 0.9mm to Ø0.3mm in an Ag97Cu3 alloy. The geometry of the cold forged component is close to the specified geometry. This indicates that the component can be cold forged with a few adjustments of the die and punch geometries. The ejection of the cold forged component proved difficult and a slight bend of the extruded part occurred.