Replacing focussing lens?

[aiello]

I got some smoke on the focussing lens of a blue laser engraving module, and despite cleaning it now has a lot more stray light than before.

Any tips for getting it perfectly clear again? I suspect it is better to replace it, but even though new lenses are inexpensive, I don't know how to get it out... The lens is threaded into the focussing ring and no screwdriver seems to fit.

A complete new focussing ring is available for a NEJE module but it may not fit mine.

 

[skijohn]

If the diode is powerful enough any contamination that may have been on the lens could burn and heat up the lens enough to burn or crack the glass of the lens, replacement may be the only option...

 

[gazer101]

With acrylic lenses, once you get smoke on them with a higher-powered laser they're toast
Glass is the way to go, just buy an extra fat screwdriver to unthread the old lens

 

[aiello]

It is a glass lens. Tried isopropanol and cotton swabs but it is still smeared. Slots for screwdriver are too narrow (spanner-type bit?)

May have to destroy old lens to get it out, hopefully without damaging the focus ring...

 

[skijohn]

I had to custom grind the tip of a screwdriver to fit perfectly in the thin slots of lens holders in order to be able to adjust and remove lenses...

 

[aiello]

Good idea! Or maybe there's a suitably sized chisel...

 

[aiello]

Found a knife sharpener and tried sharpening a screwdriver - worked! Got lens out... Thanks

Ordered some cheap replacement glass lenses, they are all M9 thread but slightly different in length/shape. Will it matter?

 

[aiello]

Update: just got 2 glass lenses which fit ok but turned out to be held in a plastic thread! It did focus the 5W blue (not quite to a line like the original) but started melting right away...

Does anyone know which lenses to get (also some have different mrad values)?

 

[Encap]

Not the cheapest but have a look here: https://optlasers.com/collimators/collimator-445-nm

and at DTRs site , maybe his DTR-3E_B would work for your purpose see: https://sites.google.com/site/dtrslasershop/home/glass-lenses