by Mary Scianna
R&D in micromachining could provide leading edge to precision manufacturers in Canada
Promising research in micromachining may hold one key to helping Canada’s ultra precision manufacturing industry become more competitive.
Researchers at McMaster Manufacturing Research Institute’s Micro Manufacturing Laboratory (MML) and at the National Research Council’s (NRC) automotive research division are working on machining optical and high aspect-ratio micro structures (e.g. micro-lens, pins and thin wall pillars) with optical surface quality below ~20 nm that don’t lose their dimensional form accuracy.
“The trend of miniaturization in consumer and industrial products today require microscopic features,” says Stephen Veldhuis, director of the McMaster Manufacturing Research Institute and the Micro Manufacturing Laboratory, and associate professor the university’s Mechanical Engineering department, Hamilton, ON. “Cell phones, cameras, biomedical devices, diagnostic devices, micro-sized devices that go inside body and microfluidic devices all require fabrication with good surface quality.”
To date, machining micro features on complex 3D geometries that have high aspect-ratio structures (e.g. researchers at NRC created thin walled structures with widths of 25 microns, approximately a quarter width of human hair in diameter, with a height of 7 mm, translating into a 1:280 aspect ratio) and optical surface quality below ~20 nm has been limited by physics. You can achieve the high optic or mirror-like surface, but you compromise the accuracy of form during manual polishing operations.
“Now we can produce very complex geometries with optical surface quality using five axis cutting motions,” says Evgueni Bordatchev, senior researcher with the automotive portfolio at NRC-Automotive in London, ON. “With automotive lighting, for example, at least 40 per cent of the cost of tooling goes into polishing, which is typically a manual process. By creating an optical surface, it eliminates the polishing step and helps to reduce the tooling cost of this process.”
Bordatchev and his research team have created demo parts with complex 3D geometries to demonstrate the capabilities of this micromachining process.
“In my work at NRC of Canada in micro machining I’m working with three processes: micromilling, laser micromachining and fly cutting, which is cutting with a single point diamond tool typically used for machining flat surfaces with optical quality.”
The significance as a researcher, says Bordatchev, is that it’s an accomplishment to overcome the challenge of machining at such micro sized ranges because you have to have the knowledge about the cutting process on micro and nano-scales, optimization of parameters to avoid deflection of the cutting tool and thin structures, for example. Second, “such high aspect-ratio structures (e.g. 1:280) can’t be fabricated by any other process; only micromilling is a most suitable and cost effective technology for such types of tooling and EDM electrodes.”
Creating parts such as very thin wall structures or arrays of very slender pins with an accuracy of one micro meter range is challenging for EDM technologies but is “state-of-the-art in advanced machining technologies,” adds Bordatchev.
The aim for both Bordatchev and Veldhuis is to create knowledge-based advanced micromachining technologies that can then be taken into the field by engineers and designers to create more innovative products not easy to replicate by potential competitors, a very real threat in competitive high-tech industries, such as photonics, automotive, aerospace and biomedical.
“Manufacturers are always looking for new technologies they can take advantage of to give their products a unique look,” says Veldhuis, citing LED technology used on Audi front headlights as an example. “Each automotive company would like a technology their designer can leverage into a unique feature. With the work we do, which focuses more on the physics of cutting in the machining process, and the work that NRC does, which is more focused on the demonstration of unique capabilities by creating complex geometries and how they can be used in industry, it’s a coming together of design, physics and unique capabilities that manufacturers could leverage to create innovative products no one else can replicate.”
Bordatchev adds that in the automotive industry, the ability to create micro structures with optical quality is called a “game-changer,” adding “several years ago it was five axis machining and now micromachining is the technology that they view as the one that will distinguish them among global competition because knoweledge-based micromachining technologies have the potential to create innovative value-added products, efficiently and cost effectively.” SMT
