We take a look at how one scientist in Singapore made a breakthrough in technology. By Joson Ng
In the film industry, there are the Oscars and the Golden Globe. In innovative technologies, there is the R&D 100 Awards, an international competition that recognises the 100 most technologically-significant products introduced into the marketplace over the past year. In late 2014, the Singapore Institute of Manufacturing Technology or SIMTech, a research institute of the Agency for Science, Technology and Research, A*STAR, announced that one of their locally-developed innovations has won an ‘Oscar’.
A Flexure-Based Electromagnetic Linear Actuator (FELA) was accorded the award as it successfully broke through the millimetres travel range, a limit encountered by other nano-positioning actuators. In addition, it is applicable to an array of precision instruments and equipment because it is able to deliver nano-positioning capability with the flexibility to configure the output resolution at an affordable price, all contained within a single package.
APMEN sat down with the brain behind FELA, Dr Daniel Tat Joo Teo, scientist (Mechatronics) at SIMTech to talk about his thoughts on winning the award as well as the trials and tribulations in developing the actuator.
“The whole division knew (first) as I was at a conference in France. I woke up one morning and received a lot of messages. I am not sure if I was extremely happy or not but my only feeling back then was: 10 years of hard work has finally been recognised in some form,” said Dr Teo.
Ten years ago, he was pursuing his PhD and back then, he had to build everything from scratch.
“It is not just about inventing an actuator. It is actually a process that took me through science, design, engineering and manufacturing,” he said. For instance, for his initial design, he used SolidWorks to cross check the stresses and strains on the elastic bending for the supports.
Back in 2003, Dr Teo was involved in the development of high precision stages. It was by no means a new field but he felt there were certain gaps that needed addressing. He said the stages were driven by piezoelectric effect, which is a technology commonly used. Even as high precision is achievable for nano range positioning, the travel range was limited.
In the end, he decided to build the nano-positioning actuators by adopting electromagnetic actuation with elastic joint members (flexure joints). In doing so, FELA can deliver nanometric resolution over millimeter stroke range and has the flexibility in reconfiguring the positioning sensitivity.
He was however immediately faced with a challenge. “We have this constraint. Although electromagnetic force has been used in the industry, the merit of using electromagnetic force is that it is frictionless. However, to harness the frictionless nature, the support must also be frictionless,” he said.
In order to build frictionless supports, Dr Teo studied the fundamentals of elastic bending and came out with new formulations to provide a longer range. Approximately a year after he embarked on this journey, a prototype was finally ready.
“We built the first in 2005. That was just the initial phase, to see if it is workable. In doing so, we also set a milestone in terms of Technology Readiness Level for industry (TRL, a SIMTech bench mark). The next thing is to see how we can push (the product) to the mass market,” he said.
With help from MicroSteel Precision, a manufacturer of precision components, Dr Teo’s product took its first big step towards industry adoption. It is at this critical juncture that he had to make a significant change to FELA in order to satisfy industry demand. The earlier version of FELA was rectangular in shape. The industry version however, is circular and smaller in size.
“When it is in a rectangular form, everything is more predictable, including the formulation. We are now pushing for a smaller size. When we start to push towards another extreme, we have to change shape, we have to go from rectangular to circular,” he said.
This change has brought about challenges in predicting the behaviour of the device as well as a profound change in the machining process.
Wire cut EDM process was used to manufacture the flexure joints of the FELA. Although the machining work seems straight forward enough, there was significant effort put into it because tolerances are tight and any violations in any part would render the whole assembly process further downstream impossible. Coupling the tolerance issue with the change in shape and size, a difficult task for the machinists just got harder.
“In the past, we were talking about a rectangular shaped FELA of size 80 to 100 mm. Now (circular version), we are touching 50 mm in diameter, (roughly) half the size. The assembly work is also difficult because you have magnets inside it that are repelling each other,” he said.
Another challenge in the manufacturing and assembly processes is that a coil is moving between two magnets (for electromagnetic effect), and the spacing between the coil and the magnet is about 0.1 mm. Taking these factors in mind, Dr Teo had to tighten his designs dimensionally and this made the EDM process a particularly challenging one.
“The tolerance is so high that the manufacturing process needs to be controlled, especially when we are manufacturing the circular (version of FELA) because concentricity now comes into play,” he said, before adding that he had numerous meetings with the machining team in order to understand their manufacturing limitations. One of those limitations was the diameter of the wire that the EDM machine uses. The smallest diameter they could get hold of was about 0.2 mm.
For Dr Teo, the other challenges faced during the wire cut EDM phase are the gap in cutting certain radius and thicknesses. According to him, the radius is already limited to 0.1 mm due to the 0.2 mm wire diameter. There is no alternate solution. The only way is to constantly think about these limitations when designing every piece of components that forms FELA.
“There are limitations in what existing EDM technology can achieve. For example, if I want to achieve a thickness of 80 µm (thickness of the elastic beam supports), we have to send it to Switzerland,” he said.
Finally, he ended up using a pre-fabricated metal shim plate instead. He added that these shims are generally used in precision levelling purposes and therefore, they have high dimensional tolerance, eg: ±0.01 mm.
Ultimately, problem-solving is all about communication, he said.
“These are the type of things I need to sit down and work out with the machinist. We need to find out what kind of wires is available. What is the best tolerance or surface roughness we can achieve,” he said.
According to SIMTech, the development of the FELA is useful for the next generation of high-precision systems such as the nano-imprint lithography systems, micro-/nano-scale positioning systems, micro-/nano-metrology systems, micro-/nano-machining systems, micro-/nano-manipulation systems, and bio-medical instruments.
Its high energy-efficiency and simplicity of construction, coupled with its maintenance-free and low cost bearings help make it a cost effective solution in a wide range of high-precision systems.
Interestingly enough, Dr Teo did not plan for the device to have that many applications when he first started out. Back then, FELA was meant to realise ultra-high precision layer-over-layer fabrication in the nano-imprinting process.
He said: “FELA was not meant to replace any technology. It was meant to bridge a technology gap that has been absent for the last 50 years. We are just trying to bridge the nano world and meso world.”
Like FELA, which is taking on more applications as it becomes more popular in the industry, Dr Teo is looking to take on more projects and break new frontiers. He told APMEN that he hopes to “break another new barrier” by using anti-gravity technology to achieve better resolution and range in his next actuator.