I got a new lens for the laser cutter, 18x22mm focal length. I wanted to try something with a smaller spot diameter for higher power density. With the short focal length there was no way to make use of the nozzles I had bought for the other lens I was using (3" FL) so I made a new lens holder/nozzle for it last night.
I found an adapter of some sort lying around. It went from a 25mm thread to a 20mmx.7 internal thread. The 25mm thread was close enought to a 1" c mount where it screwed together just fine, the thread pitches were virtually identical. To back up the lens in the adapter I took some hollow aluminum and made some threaded rings with the 20mm thread in the adapter.
For the nozzle I needed something light. I didnt have any more solid 1" aluminum bar, but I did have some 1" titanium lying around. I cut the 20mm threads on the end (Ti threads very nice) and made a 18.1mm recess for the lens. I drilled down with a #7 drill and finally drilled the final orifice hole with a #60 drill. I opened up the area next to the lens with a 15/32 drill as well. I had just tapered the outside of the nozzle 45 up to about a 1/4" diameter area around the orifice but I was having an issue with the air flow causing the material to pull up against the nozzle, I cant remember what this effect is called, but I see it in plasma cutters a lot. To resolve this I made the outside of the nozzle more round.
After turning I put it on the mill and spot faced a land for the 10-32 gas fitting.
It works pretty well, I do need to space back the lens a but, the focal point is a bit further out than I would like. Nothing an o-ring cant fix.IMG_3110
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, on Flickr