I actually worked on beta testing what was, around eight years ago, the most precise waterjet in production. It did indeed use very fine sand that seemed to get

I actually worked on beta testing what was, around eight years ago, the most precise waterjet in production. It did indeed use very fine sand that seemed to get into everything. Keeping it from caking was the main challenge. Edge quality on an OMAX is a software setting (I love their software and use it for everything 2D and vector). Basically, the numbered quality settings allow you to prioritize what kind of edge quality you want. 1 gets you the bare minimum needed to get the parts to separate. 2 is fine, but a bit rough on the bottom. Picture that the waterjet pierces the material and then moves slowly, grinding the interior edge of the cut along the path. If you corner quickly, it flares out in the opposite direction. I think of it as being like cutting with a paintbrush. 3 is optimized for dimensional accuracy on the top of the cut. Despite the fact that the water stream spreads out as it goes, the top of the cut is wider than the bottom. This is due to ejecta cutting on the way back out of the cut, and the velocity being higher near the nozzle. Higher numbers are for reducing the taper of the cut, but generally reduce dimensional accuracy. There are also settings for cutting without abrasive, which are generally only worthwhile for something soft or edible, and settings for etching, which I found too loud and messy to mess with. There are also nozzles that will tilt as they cut, which allows you to move and corner quickly by countering the taper with tilt. I do have experience with cutting precious metals with a laser. CO2 and fiber lasers may both be infrared, but it's a big spectrum. CO2 is a wavelength better suited for cutting organics, and doesn't have the fine focus or energy density available in fiber. I've used a 70 watt picosecond fiber laser for cutting silver and it actually cuts very nicely, but the problem is getting up to the initial threshold to affect it at all. Titanium, with it's low reflectance to infrared, low thermal conductivity, and high melting point, will cut with a power setting that won't leave a visible mark on silver with its opposite set of properties.