4M Knowledge base - papers

A Novel Approach for Batch Production of Micro Holes by Micro EDM

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.

Submitted on November 12, 2007 - 16:23.

A Simple Bonding Process of SU-8 to Glass to Seal a Microfluidic Device

S. G. Serra(a), A. Schneider(a), K. Malecki(b), S. E. Huq(a), W. Brenner(b)
a: Science and Technology Facilities Council, Rutherford Appleton Laboratory,Technology – Central Microstructure Facility, Harwell Science and Innovation Campus, Didcot, OX11 0QX, UK
b: Institute of Sensor and Actuator Systems Vienna University of Technology, Floragasse Str./E366 MST, Vienna 1040, Austria

Abstract

This paper describes a simple process of adhesive bonding between a glass lid and a SU-8 microfluidic device. The bonding is made by applying pressure, between 1.24 MPa – 3.72 MPa, and heat, above the SU-8 glass transition temperature (Tg). The advantages of this process are low cost, simplicity and no need of extra adhesive material, which could block microchannels and inlets. The SU-8 microchannels are fabricated on a glass substrate by UV photolithography. The resist thickness is 30 μm and the smallest channels are 5 μm in width. The bonding process was performed using a simple uniaxial press, a torque wrench and a convection oven as an alternative to the complex and expensive bonding machines with a vacuum chamber and alignment tools. To identify a suitable bonding temperature, a Tg of 175°C for the patterned SU-8 was obtained by Dynamic Mechanical Analysis (DMA). The bonding strength was 1.15MPa, measured by a pull-out test, and a bonding area of 90% was achieved, which was observed by visual inspection. It was also investigated the effect of an O2 plasma cleaning process on the bonding quality.

Submitted on November 12, 2007 - 16:23.

A simulation model for crater formation in laser milling

T Dobrev, D T Pham and S S Dimov
Manufacturing Engineering Centre, Cardiff University, Cardiff, CF24 3AA

Abstract

In pulsed laser material removal systems, it is very important to understand the physical phenomena that take place during the laser ablation process. A two-dimensional theoretical model is developed to investigate the crater formation on a metal target by a microsecond laser pulse. The model takes into account the absorption of the laser light, and heating and vaporisation of the target, including an adjustment to compensate for the change of state. A simple numerical technique is employed to describe the major physical processes taking part in the laser milling process. The temperature distribution in the target material during the pulse duration is analysed. The effect of the laser fluence on the resulting crater is investigated in detail. The proposed simulation model was validated experimentally for laser material interactions between a microsecond Nd:YAG laser (λ= 1064 nm) and a stainless steel workpiece. The measured crater depths are in agreement with the model. Such a study is very important for understanding the mechanisms of micro-structuring when laser milling is employed. The results of this research will be used in improving the micro-machining capabilities of the process.

Submitted on May 19, 2008 - 15:12.

A Soft Lithography Process for Manufacture of Alumina Micro-Components

Zhigang Zhu, Xueyong Wei and Kyle Jiang
Centre for MicroEngineering and NanoTechnology, School of Engineering, The University of Birmingham, B15 2TT, UK

Abstract

This paper presents a soft lithography technique to fabricate alumina microcomponents. The process uses elastomer polydimethysiloxane (PDMS) and makes the green patterns in tact after demoulding. The five steps of the soft lithography process are: (I) fabricating thick SU-8 moulds using UV photolithography; (II) producing PDMS soft mould from the SU-8 masters; (III) making aqueous high solids loading alumina suspension; (IV) filling patterned PDMS moulds with the aqueous alumina suspension; (V) demoulding and sintering. The rheological properties (Zeta potential and viscosity) of aqueous alumina suspensions was characterized in relation with varying pH values and concentration of dispersant (D-3005). The optimal parameters of the alumina suspension for the mould filling have been achieved as pH value = 11; concentration of dispersant (D-3005) = 0.05 g/ml; amount of binder (B-1000+ B-1007) = 0.75%, the highest solid loading = 70 wt.%. After pressurised mould filling, the complete, dense and freestanding microcomponents have been achieved by using 70wt.% alumina suspension and optimum fabrication technique, while the overall shrinkage is found as ca. 22%.

Submitted on November 12, 2007 - 16:23.

categories

ceramics | elastomers

A study of factors affecting the performance of micro square endmills in milling of hardened tool steels

P. Li (a), P. Aristimuno (b), P. Arrazola (b), A.M. Hoogstrate (c), J.A.J. Oosterling (c), H.H. Langen (a), R.H. Munnig Schmidt (a)

(a) Department of Precision and Microsystems Engineering, Delft University of Technology, Delft, the Netherlands
(b) Manufacturing Department, Faculty of Engineering, Mondragon University, Spain
(c) APPE Precision Manufacturing, TNO Science and Industry, Eindhoven, the Netherlands

Abstract

Proper setting of cutting conditions is critical for the performance of micro endmills in micro milling of hardened tool steels. In this paper, the influence of the cutting parameters on the wear behaviour of micro square endmills is presented. The selected parameters are cutting speed, depth of cut, and feed per tooth; Central Composite experimental Design (CCD) was used for a statistical analysis of the influence of these parameters. A quadratic model was fitted to describe the performance of the tool wear; the ANOVA analysis shows that the quadratic model gives a good prediction of the experimental results. On considering the magnitudes of the coefficients it is seen that the feed per tooth has a greater influence on the tool wear than cutting speed and depth of cut within the tested process window. By applying this method, the micromilling process can be planned to achieve an optimum tool wear performance for a tool-workpiece combination.

Submitted on August 4, 2008 - 13:16.

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