By Tim Shinbara, Technical Director
I’m Tim Shinbara and this month I had the opportunity to tour the OMAX Corporation facility in Kent, Wash., and better understand abrasive water jet technology and also learn about the next-generation micro abrasive water jet technologies that could better enable micromachining of multi-materials accommodating multi-hardened states.
Abrasive water jet (AWJ) technology is not a brand new technology, however some of the recent developments in micro abrasive water jet (µAWJ) technologies have brought to my attention the value in micromachining in today’s manufacturing environment, as well as the challenges. This month I wanted to focus on µAWJ and some of the industrial research and development that is ongoing to further enable affordable and viable micromachining techniques. In late July I (along with the Technology Issues Committee) spent some time with Dr. John Olsen, Vice President of Operations, and Dr. Peter Liu, Senior Scientist, of OMAX Corporation in Kent, Wash. While Dr. Olsen literally walked us through the technology, Dr. Liu provided more insight on the ongoing Small Business Innovative Research (SBIR) efforts along with his thoughts of the future developments of µAWJ.
As you may know, the primary benefits of traditional water jet are things like the ability to machine materials of varying hardness significantly faster than - and without tool wear of - traditional contact CNC techniques and manufacturing features like square holes without creating thermal damage on the workpiece itself as sometimes realized in other non-traditional processes. What µAWJ brings to market is scale … where smaller is better. One of the highest potential benefits are being found in mass customization (much like additive technologies) whether supporting patient-specific products for biomedical or enabling more efficient designs for microelectronics. Before µAWJ, the smallest feature generally fabricated by AWJ was approximately 200 µm. Recently, µAWJ has demonstrated part features at or below 100 µm, which provides the opportunity to better machine intricate, detailed features needed in such industries as biomedical, aerospace / defense and energy.
This seems very attractive … so what are the challenges with µAWJ? Ultimately, micromachining with µAWJ has similar challenges as with traditional AWJ. The same key considerations to maintain kerf width (cut width) and reduce water jet taper on the macro scale are still relevant at the micro scale. However, there are some newly introduced phenomena at the micro scale that differentiates from traditional AWJ challenges. At the micro scale there are newly introduced capillary-dominated flow regimes creating a meniscus effect that if left unattended would fill the entire bore of the mixing tube with water; with the tendency of the finer abrasives to adhere to the side walls of the mixer. There is also the challenge of gravity feeding finer and finer abrasive materials as they tend to coagulate. Water jet taper though similar in some aspects is another feature that seems to increase in difficulty at the micro level and counter-intuitively even more challenging on thinner materials.1
To help in overcoming such micro-scale challenges, recent µAWJ research and development has produced even smaller tilting nozzle heads to mitigate taper and produce more consistent micro-scale kerf widths. Further developments in software capabilities and multi-axis system controls have been demonstrated to improve 3-D capabilities for machining complex geometries. There is now a better understanding of the micro-fluidic characteristics of finer abrasives that may suggest the potential to promote cleaner cuts and the potential option to recycle the abrasive media.
As µAWJ continues maturing, more applications will present themselves. I have found similarity between µAWJ and additive technologies in their transition and acceptance in the market place. One of the most glaring resemblances is the challenge of informing the industry of their current readiness level and potential place in a manufacturing suite of solutions. Hopefully, AMT is providing such a venue for our members to become more aware of such technologies and have a place for questions to be asked; all in order for members to make more informed decisions about their manufacturing technology purchases and potential applications.