Thin sheet embossing tool design

• Main Author: Ang, Nicholas Swee Hong
• Other Authors: Sathyan Subbiah
• Format: Final Year Project
• Language: English
• Published: 2011
• Subjects: DRNTU::Engineering::Mechanical engineering::Machine shop and drawings
• Online Access: http://hdl.handle.net/10356/45947
• Institution: Nanyang Technological University

Microfluidic devices have been gaining wide use in the area of biological diagnostics applications in recent years. It operates as a single usage, disposable chip to avoid degradation and cross-contamination of samples. To lower the manufacturing costs and improve the production of these microfluidic devices, the hot roller embossing method is investigated. This project focuses on the development of embossing thin sheet tool design which is fabricated as an individual mould and then placed on the hot roller equipment. This reduces the manufacturing costs significantly as replacement of the hot roller equipment is not required. Two different materials, copper and aluminium, are selected as both materials exhibit good machining characteristics. A comparison of both materials as to their suitability to be fabricated as a mould for hot roller embossing is performed. To further the comparison, each material is tested as different thicknesses of between 0.26 mm and 2.5 mm. The Mikrotools end-milling machine used for this project has a very high speed cutting spindle which turns in excess of 40,000 rpm. A carbide tool is used to mill the sample materials to the required depth and design. A diamond tool is then used to perform the finishing cut on the profile wall to minimize the burr and improve the surface roughness of the wall. Analysis is then carried out using Scanning Electron Microscopy (SEM). This is to inspect the mould of any undesirable bond failure, defects, cracks or fracture. In order to develop a microfluidic device of quality, a smooth and even surface is essential. Further to this, the Talyscan and Confocal equipments are used to test the surface roughness of the mould. Results indicate that the finishing of the profile wall, in terms of smoothness and burr height, is greatly improved using the diamond tool as compared carbide. Aluminium exhibits highly desirable characteristics for use as a mould material as burr formation is greatly reduced; however 0.26mm thin aluminium is malleable and is slightly deformed (concave surface) after machining. Final experiment, 0.5mm thickness aluminium mould is used on conventional hot embossing to create a PMMA microfluidic device and it result is used as a control with 0.26mm thin aluminium mould which will be attached on hot roller embossing. The final embossed results on PMMA show that conventional hot embossing method is slightly better than hot roller embossing.