Manufacturing in FP7 Conference

*4M2008 - Have you registered yet?*
4M2008, the 4th annual conference of the 4M Network of Excellence will be held on 9th – 11th September 2008 at the Julian Hodge, Cardiff, UK. To secure your place please register here by 13th August 2008. Full detailed programme now available.

L. Löfgren (a), B. Löfving (a), T. Pettersson (a), B. Ottosson (a), C. Rusu (a), S. Haasl (a), K. Persson (a), O. Vermesan (b), N. Pesonen (c), P. Enoksson (d)

(a) The Imego Institute, Arvid Hedvalls Backe 4, SE-400 14 Göteborg, Sweden
(b) SINTEF ICT, N-0314 Oslo, Norway
(c) VTT, Wireless sensors, FIN-02044, Espoo, Finland
(d) Chalmers University of Technology, Micro and Nanosystems group, SE-41296 Göteborg, Sweden

Wireless sensors incorporated in RFID systems are important in several industrial, consumer and logistics applications. By extending RFID tags to sensing applications, the products become smarter. Application areas for these smart tags include; health care (verification of the environmental conditions during transport or in storage of e.g. diapers, bandages, etc.), food monitoring (food quality during transport, storage and sales) and construction industry (e.g. building material).
In this paper, a small, very low power and low cost humidity sensor tailor made for passive RFID applications is presented. The sensor consists of a glass chip substrate with a sub-micron interdigitated gold electrode structure covered with a humidity sensitive polyimide layer. The humidity absorbed by the sensing layer is measured capacitively. Finite element modeling and analytic calculations were used to determine the design of the interdigitated electrodes and the optimal thickness of the polyimide layer. A read-out electronics circuit was designed and used to evaluate the sensor. Sensors were fabricated and calibrations have been made to verify their function. The sensor response was close to linear from below 20 to above 90 %RH and its response time was proven to be at least as short as that of the climate chamber, namely 0.1 %RH/s. The concept can easily be adapted to measure a range of other parameters such as temperature or the presence of certain substances.

A.Boustheen (a), F.G.A. Homburg (a), J.E. Bullema (b), A. Dietzel (a), (c)

(a) Micro and Nano Scale Engineering, Eindhoven University of Technology, The Netherlands
(b) TNO Science and Industry, Eindhoven, The Netherlands
(c) Holst Center, Eindhoven, The Netherlands

Using active microvalves liquid flow in microsystems can be precisely controlled and timed. Plastic microfluidic networks offer high flexibility in the material selection and potentially also allow for low cost mass fabrication. For selecting a suitable micro-actuation scheme, the different options are compared on the basis of actuation performance parameters. For thermal-expansion, electrostatic, electroactive, piezoelectric and shape memory actuation principles the work density is derived from basic actuator physics and literature material parameters. For the targeted actuator dimensions also frequency, stroke and force characteristics are calculated. These are compared with actuator performance targets typical for micro-fluidic networks: forces between 160μN and 16mN, stroke of 50μm, repetition frequencies ranging from 100Hz to few mHz. As a result, only electroactive polymer and thermal actuation principles remain as viable options and shall in further work be experimentally evaluated using a modular design with interchangeable actuators.

C. Brecher (a), (c), M. Weinzierl (a), A. Rashid (b), R. Schmitt (c), D. Köllmann (c)

(a) Fraunhofer Institute for Production Technology IPT, Germany
(b) System 3R Intl. AB, Sweden
(c) Werkzeugmaschinenlabor (WZL), RWTH Aachen University, Germany

The set-up of ultraprecision machining processes is characterized by manual process steps which require a lot of personal skill and experience to full fill sub-micron requirements in form accuracy. Besides the fact that these manual process steps require a lot of time, they individualize each ultraprecision machined work piece and therefore prevent ultraprecision machining processes from becoming universal and cost efficient machining processes for high precision work pieces. To overcome this deficit, automation solutions are developed within the European Integrated Project (IP) »Production4μ« which enable the realization of efficient ultraprecision process chains with a high level of accuracy. In this paper, a sub-micron referencing system is introduced, which has been developed within this IP to contribute to the
high accuracy process chains by enabling the automated and repeatable clamping of work pieces with submicrometer deviations from their original position. This does not only enable the efficient combination of different machine-tools and processes but also allows for an increase in product quality.

P.J. Bolt, J.E. Bullema, R. Korbee, R. Kusters
TNO Science and Industry, Eindhoven, The Netherlands

This paper concerns the feasibility of polymer capping of RF-MEMS devices, replacing traditional silicon solutions. The advantage would be less costs and potential for both further miniaturisation and integration of electrical functions in the cap. One of the challenges is the resistance against expoxy overmoulding as part of the traditional back-end process chain. This involves temperatures of 175oC and pressures of 10MPa, which the cap has to withstand. Calculations are made and experiments carried out to investigate the feasibility of selected polymers. It is shown that nanofillers will lift the polymers mechanical properties comfortably above the minimum established demands.

S. Valkai, H. I. Kirei, L. Oroszi and P. Ormos
Institute of Biophysics, Biological Research Centre, Hungarian Academy of Sciences, H-6726 Szeged, Hungary

A fully integrated microfluidic sorter is introduced. It is able to count, characterize and sort micrometer sized articles and cells. All functions of the device are performed by light. The objects to be sorted are counted optically, they are characterized by measuring their fluorescence. Even the sorting itself, directing the particles into different channels is performed by the pressure of light. The device is built by photopolymerization, from a light cured optically clear resin upon a glass plate support. The whole structure is created in a single photolithography step. The microfluidic channels and optical waveguides that carry the illuminating, detecting and sorting light form a single integrated structure. The supporting units, like sample reservoirs, pumps, light sources, light detectors are easily connected to the device from the outside. The device is optimized for simplicity. It is a proof-of-concept instrument, it demonstrates that it is possible to build simple optically driven microfluidic systems that perform complicated functions.

A. Herrero (a), S. Azcarate (a), A. Rees (b), A. Gehringer (c), A. Schoth (c), J.A. Sanchez (d)

(a) Micro & Nano Technologies Dep., Fundacion Tekniker, Avda. Otaola 20, 20600 Eibar, Spain
(b) Manufacturing Engineering Centre, Cardiff University, Cardiff, CF24 3AA, UK
(c) IMTEK, University of Freiburg, Georges-Koehler Allee 103, EG-79110, Freiburg, Germany
(d) Dep. of Mechanical Engineering – Faculty of Engineering of Bilbao, Avda. Urquijo s/n, 48013 Bilbao, Spain

Apart from the important role that Micromachining and Ultraprecision machining has provided to the development of improved or innovative miniaturised products, these techniques have also attracted the interest of the researchers to obtain the highest accuracy and a thorough analysis of the principles governing the material removing mechanisms. The present article exposes the theoretical analysis of some aspects of the thin WEDM that drop the process accuracy in terms of minimum machinable slot or corner over/undercutting. The scaled electrode dimensions and the reduced power supply with respect to the normal process causes a different influence of the process variables and contributes to obtain complementary information about the WEDM process. The different force components contributing to the wire deformation are discussed and some of them are analyzed from a theoretical point of view presenting analytical calculations to evaluate their expected magnitude and pointing out the difficulties to obtain an experimental characterisation of each phenomena.

S. Geißdörfer (a), U. Engel (a), M. Geiger (a)
(a) Chair of Manufacturing Technology, University of Erlangen-Nuremberg, Egerlandstrasse 11, 91058 Erlangen

Continued miniaturization in many fields of forming technology implies the need for a better understanding of the effects occurring while scaling down from conventional macroscopic scale to microscale. At microscale, the material can no longer be regarded as a homogeneous continuum because of the presence of only a few grains in the deformation zone. This leads to a change in the material behaviour resulting among others in a large scatter of forming results. A correlation between the integral flow stress of the workpiece and the scatter of the process factors on the one hand and the mean grain size and its standard deviation on the other hand has been observed in experiments. Conventional FE-simulation, is not able to consider the size-effects observed when scaling down processes. Actually the reduction of the flow stress the increasing scatter of the process factors and a local material flow being different to that obtained in the case of macroparts. For that reason, a new simulation model has been developed taking into account the size-effects. The present paper deals with the theoretical background of the new mesoscopic model, its characteristics like synthetic grain structure generation and the calculation of micro material properties - based on conventional material properties. The verification of the simulation model is done by carrying out various experiments with different mean grain sizes and grain structures but the same geometrical dimensions of the workpiece.

J-F. Charmeux (a), R. Minev (a), S. Dimov (a), E. Minev (a)
(a)Manufacturing Engineering Center, Cardiff University, Cardiff, CF24 3AA, UK

Producing micro-castings trough vacuum investment casting is known to be associated with high cooling rates due to small scale of the castings. High cooling rates together with alloy composition might be the main factors affecting the final metallographic structure of castings’ alloys during the solidification process. When using Al-Si-Mg casting alloys, the size of the dendritic structure can be used for a non-destructive test to assess the mechanical properties and overall quality of the castings. Also the ability of the alloys to be structured by different mechanical and energy assisted processes is highly dependant on their metallographic structure. Based on earlier experimental results, this paper proposes an empirical model describing the degree of dendrite cell refinement in cast microfeatures as a function of their AR and mould pouring temperature. Additionally, the paper reports the strong correlation between the DCS refinement and the changes in the mechanical properties of the castings through MHV measurements following a Hall-Petch equation type.

J.L. Ocaña, M. Morales, C. Molpeceres, O. García, J.A. Porro, J.J. García-Ballesteros
Centro Láser UPM. Ctra. de Valencia, km. 7,3. 28031 Madrid. Spain

Continuous and long-pulse lasers have been extensively used for the forming of metal sheets for macroscopic mechanical applications. However, for the manufacturing of micro-mechanical systems (MMS), the applicability of such type of lasers is limited by the long relaxation time of the thermal fields responsible for the forming phenomena. As a consequence, the final sheet deformation state is attained only after a certain time, what makes the generated internal residual stress fields more dependent on ambient conditions and might difficult the subsequent assembly process. The use of short pulse (ns) lasers provides a suitable parameter matching for the laser forming of an important range of sheet components used in MMS. The short interaction time scale required for the predominantly mechanic (shock) induction of deformation residual stresses allows the successful processing of components in a medium range of miniaturization (particularly important according to its frequent use in such systems). In the present paper, a discussion is presented on the specific features of laser interaction in the timescale and intensity range needed for thin sheet micro-forming with ns-pulse lasers along with relevant modelling and experimental results and a primary delimitation of the parametric space of the considered class of lasers for the referred processes.

D. S. Trifonov (a), Y.E. Toshev (b)

(a) Institute of information Technology, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
(b) Institute of Mechanics and Biomechanics, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria

The present paper offers 3D CAD models of the gate system of an optical disc mould that are developed. The type of the gate system is known as a “Krauss Maffei” system, in which the central hole of the polymer substrate is formed by breaking off the circle gate from the polymer substrate. The gate depth and the gate position are defined as variable parameters and combined with different variants of the processing conditions in mould filling simulation. A range of improved variants of all the variable parameters is obtained with the help of iterative steps within the frame of the simulation code. A modified gate system is proposed in the process of research, which allows a gate with a larger depth parameter to be used. The modified system allows also alteration of the gate position with respect to the central hole. The best results are achieved, using the proposed modified gate system in the case, when a gate with a larger depth is used and the gate position is located symmetrically towards the central hole.

D. Dantchev, K. Kostadinov
Institute of Mechanics, Bulgarian Academy of Sciences, Acad. G. Bonchev St. Bl. 4, 1113 Sofia, Bulgaria

We analyse, as a function on the temperature T and the chemical potentialμ , the total force ( , , ) tot F Tμ L between two metallic plates of a gripper separated at a distance L from each other and immersed in a nonpolar fluid which can be liquid, or gas. In our approach we take into account the direct substrate-substrate van der Waals interaction, the van der Waals interactions between the molecules of the fluid with the other molecules of the fluid as well as with the constituent elements of the substrate, and the interaction between the plates generated by the fluctuations of the density of the fluid (i.e., the Casimir force). We suppose that both plates are equal and strongly prefer the liquid phase of the fluid. Under such boundary conditions both the direct plate-plate van der Waals interaction, as well as the Casimir force, are forces of attraction of the plates toward each other. In the phase space (temperature, chemical potential), we identify the regions where the net interaction force is the strongest. It turns out that these regions are close to the bulk critical point of the fluid ( = ,μ=μ) c c T T , and near the so-called capillary condensation regime

J. Fleischer, M. Deuchert, C. Kühlewein, C. Ruhs
Institute of Production Science (wbk), Universität Karlsruhe (TH), Kaiserstrasse 12, 76131 Karlsruhe, Germany

The geometry of micro milling tools currently in use have been adopted from macro tools, assuming that chip formation and process kinematics are analogical in both types of tools [1]. Experience has proved that micro tools respond to influences in a very different way than macro tools [2]. Oftentimes, structural details such as the rake angle and the twist angle impede further miniaturization and are impossible to achieve with conventional manufacturing techniques. Therefore it is necessary to get a comprehensive understanding of the entire process by taking a structure mechanical and cutting technological approach to micro milling tools in order to be able to optimize them. Another objective consists in the production of these miniaturized milling tools by means of force-free procedures such as laser ablation and electrical discharge machining.
The present state of research already puts the deficits of the currently available tools on display. Insufficient manufacturing tolerances of ±10 μm, constitute a substantial change of cutting conditions for the commonly used lateral infeed or feed per tooth of a few micrometers. Sometimes, only one cutting edge is engaged, which results in increased wear and, therefore, reduced durability, increased cutting forces, minor surface quality and a higher probability of milling cutter breakage. For that reason, a single-edged geometry has been proposed. It guarantees clear adjustment of the process parameters feed per edge and lateral infeed. For that purpose, stability analyses of simple stylus geometries have been conducted by means of FEM simulations. The resulting tool with a diameter down to 30 μm was machined on the EDM-machine at the wbk (Sarix SX 100). First tests have been carried out that prove the ability of these tools to cut steel.

G. Tosello (a), A. Schoth (b), H.N. Hansen (a)

(a) Technical University of Denmark (DTU), Department of Mechanical Engineering, Produktionstorvet, Building 427S, DK-2800 Kgs. Lyngby, Denmark
(b) Laboratory for Process Technology, Department of Microsystems Engineering (IMTEK), University of Freiburg, George-Koehler-Allee 103,79110 Freiburg, Germany

In polymer micro manufacturing technology, software simulation tools adapted from conventional injection moulding can provide useful assistance for the optimization of moulding tools, mould inserts, micro component design, and process parameters. Conventional implementation methods of simulation are not suitable for micro injection (μIM) application and are limiting the possibility to extend the use of existing packages for the modelling and the simulation of polymer micro parts. Different strategies optimized for the set-up the simulation of a miniaturized part with micro features are presented. Model design and mesh issues are discussed, as well as dynamic implementation of the flow constrains for the creation of an effective interface between the machine and the polymer flow in the simulation software. The results of the different methods are evaluated by means of a quantitative study which compares the simulated results and the actual micro injection moulding experiments.

C.A. Griffiths, S.S. Dimov, E. B. Brousseau and M. S. Packianather
Manufacturing Engineering Centre, Cardiff University, Cardiff CF24 3AA, UK

Micro injection moulding as a replication method is one of the key technologies for micro manufacture. The understanding of process constraints for a selected production route is essential at both the design stage and during mass production. In this research, an existing Finite Element Analysis (FEA) system is used to study the effects of four process parameters, namely melt and mould temperature, injection speed and part thickness. A special attention is paid to the melt flow sensitivity when filling micro channels, particularly the factors affecting shear rate and flow front temperature. The results obtained from two different simulation models are presented for two polymer materials, PP and ABS and conclusions are made about the important factors affecting part quality.

G. Lalev (1), P. Petkov (1), N. Sykes (2), V. Velkova (1), S. Dimov (1), D. Barrow (2)

(1) Manufacturing Engineering Centre, Cardiff University, Newport Road,Cardiff, CF24 3AA, UK
(2) metaFAB, Cardiff University, Newport Road, Cardiff, CF24 3AA, UK

A cost effective methodology for pattering of Nano Imprint Lithography (NIL) templates with different length scale features is proposed. The approach relies on selecting the optimum processing window of different technologies for cost effective micro and nano patterning. Very promising results were obtained when first fused silica templates were structured by F2 laser ablation at 157 nm without inducing phase transformation of the material. It was demonstrated that nanoscale features and complex 3D microscale features could be machined with a Focused Ion Beam (FIB) over the existing topography produced by laser ablation. Thus, a large area (up to several square centimetres) of the NIL templates is easily patterned with micro- and even meso-scale features by laser ablation while nano- and micro-scale features could be introduced by FIB machining.

K. Alexandrova (a), I. Markov (a) – Deneva (b), A. Gigova (a), I. Dragieva (a)

(a) Institute of Electrochemistry and Energy Systems, Bulgarian Academy of Sciences, Sofia, Bulgaria,
(b) University of Chemical Technology and Metallurgy, 1756 Sofia, 8 Kl. Ohridski Blvd., Bulgaria,

Fe-Co-Cr-B(N,C,O,H) nanoparticles were synthesized by chemical reduction in aqueous solutions of cobalt precursor complexes such as (ethylenediamine)dichloro cobalt chloride [Co(en)2.Cl2]Cl and aqua solutions of FeCl2.4H2O and CrCl3.6H2O with sodium borohydride as reducing agent. During the synthesis a reactor insuring hydrodynamic conditions of ideal mixing for solutions at a room temperature and atmospheric pressure was used. Transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Fourier transformation infra red spectroscopy (FT-IR) investigations of nanoparticles obtained were carried out. The influence of the applied d. c. magnetic field during the synthesis on their properties were established. It is visible that a d. c. magnetic field induces a chain arrangement of nanoparticles with higher hydroxide content, possessing higher coercive force and lower transmittance determined by FT-IR.

W. Michaeli (a), F. Klaiber (a), S. Scholz (b)

(a) Institute of Plastics Processing, RWTH Aachen University, Aachen, Germany
(b) The Manufacturing Engineering Centre, Cardiff University, Cardiff, CF24 3AA, UK

Telecommunication, information and medical industries have a high growth potential. A key technology for those industries is the replication of microstructures. Precise microstructured parts with functional surfaces can be produced economically by injection moulding. The whole process chain (thermal mould condition, moulding, demoulding, measurement and analysis) must be analysed carefully to ensure the highest precision and reliability. To enable the precise production of such structures fundamental studies were conducted at the Institute of Plastics Processing (IKV). The studies considered several polymers (PMMA, POM) on the one side and various test structures on the other side. In addition an innovative external inductive heating unit was analysed and implemented into the process to heat the cavity surface efficiently. Using this technique cavity surface temperature increase rates of up to 60 K/s have been achieved. A pyrometer was implemented for contact less instant temperature measurement, and controller was used to realise preset cavity temperatures by regulating the inductor power. With the dynamic inductive heating system the moulding accuracy of the microstructures could be increased drastically. The final step of the process chain comprises of the measurement and analysis of the microstructured moulded parts. To analyse the microscopic deviation between the mould cavity and the surface of the moulded part scanning electron microscopy (SEM) and white light interferometry (WLI) was used.

P V Petkov, S Scholz and S Dimov
Manufacturing Engineering Centre, Cardiff University, Queen's Buildings, The Parade, Newport Road, Cardiff, CF24 3AA, UK

Laser milling with microsecond pulses is a thermal material removal process usually associated with detrimental effects such as heat affected zones (HAZ), a recast layer and debris. Process optimisation can lead to considerable reduction of the above mentioned negative effects. In this context, the research investigates the effects of tool path optimisation and material removal strategies on the resultant surface quality and edge definition. The conducted experimental study shows clearly that the applied milling strategies have a significant effect on the resulting surface topography and the edge definition. Also, the research demonstrates that by optimising the laser path and material removal strategies it is possible to reduce significantly the thermal load when milling micro features, and thus to minimise HAZ and other secondary effects.

C.A. Griffiths (1), S. S. Dimov (1), E.B. Brousseau (1), C. Chouquet (2), J. Gavillet (2), S. Bigot (1)

(1) Manufacturing Engineering Centre, Cardiff University, Cardiff CF24 3AA, UK
(2) French Atomic Energy Commission (CEA), Laboratory of Innovation for New Energy Technologies and Nanomaterials (LITEN), 38054 Grenoble, France

Micro injection moulding as a replication method is one of the key technologies for micro manufacture. The understanding of process constraints for a selected production route is essential at both the design stage and during mass production. In this research a tool surface treatment is used to study the effects of demoulding a part with micro features. In particular a tool coated with diamond like carbon (DLC) will be compared to an identical tool without coating. Through a range of experimental trials the effects of four process parameters, namely melt and mould temperature, and cooling and ejection time will be used to evaluate the demoulding process. Using two polymer materials PP and ABS, a special attention is paid to the forces present in demoulding and conclusions are made about the influence of DLC surface treatments and the factors affecting demoulding.