mirror alignment

[phil2simmons]

Hi
We have an LS6090 at school. I came back to school yesterday after having a week off due to snow closures. I checked the machine over and cleaned/aligned the mirrors and have noticed two things.
1. When cutting thicker materials 5/6mm ply (not something we do very often), the cut is tapered inwards from top to bottom, ie not at 90 degrees to the top surface. I assume this is due to the final lens at the cone end (which I took apart to clean). How is this set up?
2. I noticed very small air bubbles (up to 1mm diameter) attached to the laser tube which will not shift. How can I get rid of these and will they damage the laser/reduce performance?
Phil

[Spooky]

Hiya Phil,

1:The nature of focal points is such that you won't get a straight beam at the cutting point, if you can imagine it being very similar to the old days of burning leaves with a magnifying glass as a child using the sun? The thicker the material the more noticable it is. Very little can be done about it on home / school laser systems. Big industrial lasers have multiple focal lenses so eliminating this problem but your talking about some very expensive kit (£100,000+++)

2:Yes they will affect the system and can in extreme circumstances kill your laser tube. Pinch the water inlet tube and release quickly, this will often cause enough of a surge to get the bubbles to move along. Bubbles of even 1mm in the mirror cooling chambers can cause a hotspot and crack the mirror in the tube.

hope that helps

best wishes

Dave

[phil2simmons]

Hi Dave

Thanks for the info. I have tried pinching the inlet tubes but the bubbles just seem to dance slightly whilst I am pinching but do not move at all when I release the tube. There are hundreds of them mainly at the lower end (400mm)of the tube.

Any other suggestions would be welcome. Can the tube be drained of water and refilled? We have only had the machine for 5-6 months, is it something I should call Chris about?

Thanks
Phil

[Spooky]

Hiya Phil,

Nope, bubble draining isn't really a call out (unless the only tool in your toolkit is a hammer)

Do you have an anti freeze in the water system? sometimes that can help (it alters the speciffic gravity of the fluid) but only add around 500ml to the entire tank.
Draining is also an option, it's pretty easy to do just make sure you refil with de-ionised water and let it have a good long run (without the actual beam on) to remove bubbles.

I'd do the anti freeze thing first and see if that helps, if no luck then go for a drain

best wishes

Dave

[phil2simmons]

Hi Dave
Thanks for the prompt response, I really appreciate it. I will try the anti freeze first and let you know how I get on. Probably wont have time to look at it until next week though.
Phil

[phil2simmons]

Hi Dave

We had 3 weeks holiday so I decided to empty the system of water and let it dry out and start afresh after the holiday. Came back today and filled up and all bubbles have gone.Thanks again.

Phil

[Spooky]

No problem Phil

Bubbles can be a pain sometimes

happy new year

Dave