Professor Mustafizur Rahman

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Design of development of machine tools for micro/nano machining

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Figure 1: High aspect ratio (of up to 200) micro shaft manufactured by micro turning.

Figure 1: High aspect ratio (of up to 200) micro shaft manufactured by micro turning.

Figure 2: Micro structure manufactured by micro wire-EDM process.

Figure 2: Micro structure manufactured by micro wire-EDM process.

Under the leadership of Professor M Rahman, the Micro and Nano Machining Research Group at the Department of Mechanical Engineering, NUS, has developed a miniature machine tool for multiple types of micro machining in one set-up. The set-up, which is equipped with an in-situ measuring system, is capable of carrying out micro turning, micro milling, micro electro-discharge machining (EDM), micro wire-cut EDM and their combination. The developed on-machine measuring device ensures high dimensional accuracy of the machined micro-structures. The figures below show a high aspect ratio shaft (80 µm in diameter and 15000 µm in length) and a micro structure produced by the set-up. Micro shafts of 15 μm in diameter, micro lenses on BK7 glass, micro holes (30 μm in diameter) in silicon, and other complex micro components have been successfully manufactured using this machine. Patents are currently being filed for the miniature multiple micro machining system as well as the in-situ measuring unit.

 

In the area of nano precision machining, the group has achieved a 2 nm surface finish on electroless nickel plated die materials, 4 nm surface roughness on glass and 200 km machining length for diamond tools, using the ductile mode machining and/or the electrolytic in-process dressing (ELID) grinding techniques.
In addition to fundamental research, the group is also active in working with industries and has received international recognition by collaborating and/or providing pertinent micro and nano machining services to the world’s technology leaders, including companies like Boeing, Airbus, Hitachi and Corning Cables.

 

6.5μm hole machined on 50μm stainless steel plate, probably the world’s smallest hole with highest aspect ratio

6.5μm hole machined on 50μm stainless steel plate,
probably the world’s smallest hole with highest aspect ratio

 

 

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The DT-110 Hybrid μEDM machine.Technology invented by Prof Rahman and his team. Currently, patented and licensed to NUS spin-off company named “Mikrotools Pte Ltd.” which specializes in the manufacture of ultra precision machine tools.

When it comes to machining micro-sized parts and features, especially ones that are less than 100um, there is a limited selection of feasible manufacturing processes. Micro-EDM is a process that allows you to machine micro-sized parts accurately and precisely. However, micro-EDM is not just about using smaller sized electrodes on machines used to fabricate larger parts. For a successful micro-EDM process, machines require the necessary accuracy and precision.

The DT-110 Hybrid μEDM machine has been engineered from day one to excel at micro-machining. What is unique about the DT-110 machine is the ability to perform multiple micro- machining processes on the same machine, allowing the machine to excel at hybrid μEDM.

Hybrid μEDM is the utilization of two or more processes including EDM on the same machine to achieve highest levels of accuracy, precision and throughput.

For example, with its patented hybrid μEDM technology, micro-sized electrodes can be fabricated directly on the DT-110 machine accurately and precisely using the micro-turning process.

Other micro-EDM machines utilize Electrical Discharge Grinding (EDG) to fabricate micro-sized electrodes directly on the machine, which usually takes more than an hour. In contrast, with micro-turning, it will only take about a minute.

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