All lasers use focusing lenses. That determines marking area size and height above the workpiece. Some have autofocus, others need to be focused manually. The nicest one I tested was from Keyence. It had a neat way of focusing the optics. There was a pilot laser (very low power, almost like a laser pointer) that created a 3 mm box and a point of light. Raise or lower the laser head until the point converges inside the box and you are ready to mark. Keyence lasers started at about 45K and in my opinion were worth every penny. We had one as a test unit for a couple of weeks, very nice. The Trumpf's I use right now have to be precisely measured in height above the workpiece. Lasers are somewhat forgiving on marking height depending on results needed, plus or minus a couple of millimeters. It is true that you can mark anodized metal with a CO2 because you are only burning away the anodizing, not the metal itself. But, that lessens the possibilities. There are other types besides YAG lasers, all pretty much doing the same thing. There are also lamp pumped and diode pumped lasers, diode pumped being less maintenance. YAG lasers and such are not that much more expensive than CO2, the cost being in the table or machine base it comes in and what kind of parts handling equipment you are looking for. We buy OEM heads and do our own automation. We mark everything now with lasers including tooling, fixturing, you name it. It is one of those machine that once you buy one, you realize all the things you could have been doing with one all that time you didn't have one.
Paul
