Sunday, October 24, 2010

A little more on Jetting - surgery, art and diesel replacement

Being somewhat jet lagged today, after returning from Austria last night, I won't attempt anything that requires any great mental dexterity today, but rather continue on the theme about developments that are going on in my field that are likely not to be known to the more general public. One of the things that has been fascinating has been the way in which waterjets are being developed for use in the medical field. There was another illustration of this in a paper by Biskup et al, at Leibniz University in Hannover. When surgeons repair torn ligaments in the knee (an Anterior Cruciate Ligament Reconstruction) they use screws to hold the transplanted piece in place. Use of different materials for these screws has shown to have some long-term problems when they are made of metal. Recent work has shown that if these screws are themselves, however, made of bone, then, over time, the screw is integrated into the surrounding structure and becomes more stable. However it is hard to machine bone conventionally because if it gets heated, then the bone dies. If, however, it is shaped using an abrasive waterjet, to cut the thread, and the internal channel, which is also used to turn the screw, then temperatures can be controlled so that the bone is still viable. (Though it needs some chemical treatment to remove prions).

Back in 2006 the conference was held in Gdansk, and one of the interesting papers was on some work being done by Przemyslaw Borkowski at Koszalin University of Technology, in transferring photographs into inscribed pictures cut into metal. We took that idea and have moved it into a surface textural change that creates the picture as a 3-tone image in metal and rock (hence the "art") but there has been another development that has moved this into commercial availability. Nathan Webers and Carl Olsen of Omax Corporation, has modified the software on their cutting tables so that a controlled depth image can be inserted into a surface from an image. This, for example, is a lizard etched into aluminum.

The image was about 6 inches across and maybe half-an-inch deep.

It may make life a lot easier for those who have to carve images into stone, though removing a little of the artistic license with which sculptors apply their craft.

Incidentally Przemyslaw gave a talk at this conference on the use of waterjets in crushing coal. If you can take coal down to about 5 microns and mix it with water at 50% (roughly) GE have shown - by running a locomotive for more than 700 hours on the track - that it can replace diesel fuel. Looking at different available coals, it appears that brown coal is a little easier to break to the required size range than bituminous, which were the two varieties that he looked at. Using waterjets to do the crushing can make the process technically simpler and less energy intensive than other methods of getting the coal down to the required size.

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