Big laser work

Dave and I spent a few hours on the Big Laser tonight. It was having some issues with the beam getting clipped and some shifting of the beam.
I enlarged the beam nozzle exit hole to provide some more clearance and we replaced the lens with a new one (we should order a few spares, they are cheap).
The beam seems mostly centered now and should work fine.
If the system gets wonky, or gets crashed, please let us know at

Good times,


Replacement lenses are $12 to $21 depending on supplier. I’ll add a couple to the wardens buy list for August.

I wonder if we could make a “crashed the laser” button that just sends an email saying “The head got crashed. May or may not be fine.” then mount it on wall or laser cart.

Put a 3 axis accelerometer on the head, don’t even need a button, just have it monitor for a crash and report it when detected!

I would assume it would be difficult to detect a crash vs, a raster line end, etc. plus it wouldn’t detect the times when the head is driven into something slowly and forcefully.

There are two issues both having to do with alignment / cleanliness of the mirrors and lenses.

First the basic alignment of the laser mirror is critical. Alignment must be square to the frame and dead center to the mirrors. Miss either of these by a fraction of a minute of angle or millimeter from the center and the power delivered at the focal point is reduced. Alignment is also a problem as the beam must exit the laser head air orifice. Misalignment means the beam is eclipsed by the edge of the air orifice.

Crashing doesn’t seem to be the problem so much as alignment.

The problems we chased last night lead to this:

  1. We replaced the lens, because the old one hand a flaw in the coating. During z-axis alignment testing we saw a donut hole in the middle of an unfocused burn. Who knows how the flaked coating happened. That seems to have eliminated the donut hole and improved focus. That new lens had a different focal length which is now baked into the laser config file.

  2. Brad enlarged the air orifice hole which makes alignment less critical.

  3. We found the laser head assembly, basically the tube under the third mirror wiggles. This means that a good alignment can fairly easily go wrong. Just the acceleration of the head could make it move. The lens holder wiggles. The air nozzle wiggles. There was no quick fix last night. We need to think carefully about either solving the wiggle or replacing the head assembly. The problem is that the replacement might have the same design flaw. More wise discussion is required.

  4. We aligned the beam to the center of the air orifice to the best of our ability.

The best answer we have for now is QUIT MESSING AROUND WITH THE ORIFiCE. Don’t take it off. Taking it off is messing it up more.

Report problems with as much detail as possible.

Dave Velzy