4M Knowledge base - papers
Kornel F. Ehmann(a)(b)(c)(d)
a: Department of Mechanical Engineering, Northwestern University, Evanston IL, USA
b: Department of Mechanical Science and Engineering, University of Illinois at Urbana/Champaign, USA
c: Department of Mechanical Engineering, Indian Institute of Technology – Kanpur, India
d: Department of Mechanical Engineering, Chung Yuan Christian University, Chung Li, Taiwan
Micro-manufacturing in the context of this presentation is defined as the manufacture of components and products in the sub-millimeter to a few-millimeter range with micron size feature characteristics of high accuracy and precision in a wide range of engineering materials by non-lithography based processes. The paper addresses three topics. First, the findings of a worldwide study on micro-manufacturing, conducted by the World Technology Evaluation Center, Inc. (WTEC) will be summarized. This summary will compare U.S. efforts to those in a number of Asian and European countries. Second, a précis of selected ongoing work conducted at U.S. universities with leading programs in the field will be given. Topics to be discussed include the development of miniaturized machine tools for cutting, forming and manipulation as well as the modeling of micro-manufacturing processes. An account of the growing industrial activities related to the development of micro-manufacturing equipment will also be included. Third, emerging directions and challenges in the development of micro-manufacturing technologies will be reflected upon.
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.
S. Geißdörfer, U. Engel, M. Geiger
Chair of Manufacturing Technology, University of Erlangen-Nuremberg, 91058 Erlangen, Egerlandstr. 11, Germany
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.
An analysis of the effects of nanolayered nitride coatings on the lifetimes and wear of tungsten carbide micromilling tools
D. Zdebski (a), D.M. Allen (a), D.J.Stephenson (a), J. Hedge (a), C. Ducros (b) and F. Sanchette (b)
(a) Precision Engineering Centre, Cranfield University, Bedford MK43 0AL, UK
(b) CEA Grenoble, Labatoire des Technologies des Surfaces, 17 rue des Martyrs 38054 Grenoble CEDEX, France
Micromilling is becoming increasingly important for a wide range of manufacturing tasks in the general field of microengineering, such as milling small channels in micromoulds designed for the fabrication of microfluidic devices by microinjection moulding of polymers. However, micromilling tools, often less than 1mm in diameter, are rather delicate, fracturing when forces become excessive and, consequently, micromilling can become an expensive process. In an attempt to increase tool lifetimes and reduce costs, micromilling forces have been measured with a microdynamometer and the effects of chromium nitride/titanium nitride and titanium aluminium nitride/titanium nitride coatings have been evaluated as an aid to decreasing tool wear and extending the lifetime of tungsten carbide micromilling tools. The surface finish of the milled workpiece has also been measured to monitor how tool wear affects the resultant milled surface.
An Approach for Predicting the Correct Geometry and Parameters of the Sprue System of an Optical Disc Mould by us use a CAD...
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
3D CAD models of different variants of the sprue system design of an experimental optical disc mould are developed. The main purpose of the present work is to be predicted the correct geometry shape and parameters of the sprue system before these elements to be produced. The 3D CAD models are built as a combination of the polymer substrate and the sprue system, considered as one object. This approach allows achieving a precise design of the sprue system, before to import the 3D CAD model in the computer simulation program. Different variants of the sprue system design are defined and three parameters are chosen as variables: the gate length and depth and the sprue draft. By means of iterative steps in the frame of the mould filling simulation software, correct variants of the gate geometry and parameters and the processing conditions are achieved. The best results are obtained using the new proposed sprue system with symmetrical melt distribution area.
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