4M Knowledge base - papers

S. Geißdörfer, U. Engel, M. Geiger
Chair of Manufacturing Technology, University of Erlangen-Nuremberg, 91058 Erlangen, Egerlandstr. 11, Germany

Abstract

At microscale, the large ratio between mean grain size of the material and specimen dimension cause an increasing influence of single grain forming behaviour on the overall forming process. Thus the forming behaviour of these parts can no longer be regarded as to be homogeneous. This leads to a change in the material behaviour resulting in a large scatter of forming results, e.g. varying cup height in a cup backward extrusion process or varying spring-back angles in a micro bending process. Moreover, some 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 detected in experiments. Conventional FE-simulation which is by its nature size independent, is not able to consider these effects observed when scaling down processes, in particular represented by a reduction of the flow stress, an increasing scatter of the process factors and a local material flow being different to that obtained in the case of macro parts. Therefore, a new simulation model is being developed in order to take into account the identified effects and to determine the scatter of the process factors. The so-called mesoscopic model provides the discretisation of the simulated material into individual objects which represents the grain structure of the real material. To each object an individual flow curve is assigned, calculated on the basis of metal physics given by Hall-Petch and Ashby’s theory. The computational grain structure generation is based on the theory of a Monte Carlo Potts growth law.

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.

A De Grave, T. Eriksson, H.N. Hansen
Department of Manufacturing Engineering and Management, Technical University of Denmark, 2800 Kgs., Lyngby, Denmark

Abstract

Demoulding micro structured surfaces and micro parts is an important issue in replication of micro technology based components. In this paper a state of the art on ways to improve demoulding of microstructured parts both in polymer moudling and metal injection moulding is presented. The approach is described and simulation methods are shown in relation to previously existing studies. The approach chosen is the investigation of the influence of the demoulding angle on the demouldability of polymer mouldings. The design is based on a number of micro sized cones with different slope angle placed on a flat metal surface. A mould design is proposed and simulated. The design is based on a number of micro sized cones with different slope angle placed on a flat metal surface. A method for characterization of the mould using Laser Scanning Confocal Microscopy (LSCM) and Atomic Force Microscopy (AFM) to verify the slope angle and the straightness quality of the slope is discussed. Initial mould filling simulations using a 2½ D mesh show that a real 3D simulation were performed.

W. Michaeli, T. Kamps
Institute of Plastics Processing at RWTH Aachen University, 52056 Aachen, Germany
A De Grave, T. Eriksson, H.N. Hansen
Department of Manufacturing Engineering and Management, Technical University of Denmark, 2800 Kgs., Lyngby, Denmark

Abstract

Demoulding micro structured surfaces and micro parts is an important issue in replication of micro technology based components. In this paper a state of the art on ways to improve demoulding of microstructured parts both in polymer moudling and metal injection moulding is presented. The approach is described and simulation methods are shown in relation to previously existing studies. The approach chosen is the investigation of the influence of the demoulding angle on the demouldability of polymer mouldings. The design is based on a number of micro sized cones with different slope angle placed on a flat metal surface. A mould design is proposed and simulated. The design is based on a number of micro sized cones with different slope angle placed on a flat metal surface. A method for characterization of the mould using Laser Scanning Confocal Microscopy (LSCM) and Atomic Force Microscopy (AFM) to verify the slope angle and the straightness quality of the slope is discussed. Initial mould filling simulations using a 2½ D mesh show that a real 3D simulation were performed.

Micro products made of thermosetting polymers enable innovative applications since thermoplastics do not always yield the desired properties: thermosetting moulding grades offer advantages in thermal durability and chemical resistance in comparison to thermoplastic resins. Processing smallest quantities of polymeric material for applications in micro system technology require high process accuracies, e.g. in the volume of plasticised material and injection dynamics. Alternative machine concepts especially designed for micro injection moulding meet these requirements by means of special constructive setups mostly by using a plunger for injection. An appropriate micro injection moulding machine prototype is available at IKV Aachen. A new design of the plasticising and injection unit specially designed for thermosetting moulding materials is presented in this paper.

Chantal Khan Maleka, Gaël Thuilliera, Roland Duffaitb , Laurent Guyoutc
a Laboratoire FEMTO-ST, CNRS UMR 6174, Département LPMO, 32 Avenue de l’Observatoire, 25044 Besançon Cedex, France.
b Centre de Transfert des Micro et Nanotechnologies (CTMN), 39 Avenue de l’Observatoire, BP 1445-25007 Besançon Cedex 3, France.
c Department of Applied Mechanical Engineering, University of Franche Comté, 16 Route de Gray, 25030 Besançon Cedex, France.

Abstract

Our approach uses a two-step replication process for hot embossing and a rigid polymeric intermediate mould. This process overcomes some geometrical limitations in microstructured mould fabrication, enables positive-tone imprinting, prolongs the lifetime of the master, and lowers the overall cost of the replication process.

T. Brenner, C. Müller, H. Reinecke, R. Zengerle, and J. Ducrée
IMTEK – University of Freiburg, Georges-Koehler-Allee 106, D-79110 Freiburg, Germany

Abstract

We established an integrated prototyping chain for rapid fabrication of microfluidic chips in polymers comprising fabrication of masters made from elastomers, replication into polymers by soft embossing, surface modification and thermal sealing. Our techniques enable rapid and precise fabrication of fully functionalized microfluidic chips featuring typical minimum lateral dimensions of 50 μm and aspect ratios smaller than one.