Lens Problems

[bob pfohler]

I seem to be going through a lens about every 6 months, seems a little too often for only using it a couple of times a week. The lens gets a brown mark in the middle.

I keep the lens clean and I use air assist for vector cutting (not rastering) and the pressure is set low on the air assist as to not get what I've read here to be the venturi effect. The air assist on a Universal is a cone type and the end of the cone gets gummed up sometimes after engraving just one sheet of plastic so I'm wondering if I should use air assist even when rastering.
I see the air assist on the Epilog is a tube that blows the air from the side rather that straight through the cone like the Universal, seems like a better set up.

Any suggestions from someone who may have had similar experiences?

[Frank Corker]

Well a lens that is getting used up every 6 months is ridiculous. It's totally unacceptable. Bob are you sure that your compressor is pumping out enough air? I have one of those small Gast compressors that pushes around 30psi which is okay (wouldn't blow out a cigarette) and I have it outside of my cabin in a waterproof box outside. It was working ok until I put my finger underneath the air nozzle and found out the was diddly squat coming out, on checking I found the air intake was heavily clogged up. I understand your concerns about the venturi effect, but have you thought about just pushing the air pressure up and seeing if the brown mark appears after use? You shouldn't need to use air assist when rastering but the air needs to be extracted to prevent fumes rising.

[bob pfohler]

I have the compressor set at 40psi and then down to 15psi at the laser, I can definately tell it's working when vector cutting. If they weren't $230 I would try installing the backsweep option to the laser which direct the air at an angle.
I've put a lot on money in repairs into my PLS in the last year and that's dissapointing for a $20k + machine but that's another thread. The lens problem is just the final straw.

Well a lens that is getting used up every 6 months is ridiculous. It's totally unacceptable. Bob are you sure that your compressor is pumping out enough air? I have one of those small Gast compressors that pushes around 30psi which is okay (wouldn't blow out a cigarette) and I have it outside of my cabin in a waterproof box outside. It was working ok until I put my finger underneath the air nozzle and found out the was diddly squat coming out, on checking I found the air intake was heavily clogged up. I understand your concerns about the venturi effect, but have you thought about just pushing the air pressure up and seeing if the brown mark appears after use? You shouldn't need to use air assist when rastering but the air needs to be extracted to prevent fumes rising.

[Mike Lassiter]

How well is your exhaust blower working? Possibly it is not pulling smoke out of cabinet very well and the air assist is actually aggravating problem by pulling smoke into lens housing and blowing it on your lens. My cone will develop a buildup on the small end over time that I have noticed will start closing the opening up the air blows out if not cleaned off. Seems to me this is more so when cutting wood if memory serves right.

[Mike Null]

Bob

In 15 years of full time operation I've never had to replace a lens. I think you should be cleaning them twice a day or more until you identify the cause of the problem. I suspect that it has to do with air being misdirected during your cutting process.

Have you talked with ULS tech support?

[George M. Perzel]

Bob;
Don't throw those old lenses with brown marks away-most probably heavily burnt on debris which cannot be removed with normal lens cleaner. Try this- get a can of Oven Cleaner and flood the lens with it-keep it wet for at least an hour then rinse with water or lens cleaner-should be clean.
Good Luck
Best Regards,
George
Laserarts

[bob pfohler]

Nice tip, I'll give it a try.

Bob;
Don't throw those old lenses with brown marks away-most probably heavily burnt on debris which cannot be removed with normal lens cleaner. Try this- get a can of Oven Cleaner and flood the lens with it-keep it wet for at least an hour then rinse with water or lens cleaner-should be clean.
Good Luck
Best Regards,
George
Laserarts

[Rodne Gold]

You sure your air is oil-less and dry? I'm sure there would be a raft of complaints of the same nature if the ULS air assist was at fault.

[bob pfohler]

George's tip was on the mark, even though I had cleaned the lens before every use some of the residue still remained on the lens. A little oven cleaner (never would have thought of that) a soft q-tip and 2 beers later I had a new looking lens. Thanks to all who replied.

[Gary Hair]

and 2 beers later

I find that the solution to most problems... it either fixes the problem or I no longer care.

Gary

[Frank Corker]

Well done George and good news Bob. Love it!

[Mike Mackenzie]

Bob,

Remove the cone and run the air see if you get the same mark. You may have a leak in the air line somewhere that causes the cone to pull in the air instead of blowing it through the cone.

You may also want to check to see if the cone is clipping the beam. Run a raster file directly on the surface of the table (no Material) let it run for a couple of minutes then feel the cone if it is HOT your beam is hitting the cone and needs to be adjusted. I have noticed that the hole in the cone is small and can get clogged quickly what I have done is to drill out the center of the cone to a larger diameter.

Also while it may clean the spot on the lens I do not recommend using Oven Cleaner and water on your lens. Every lens has a hygroscopic coating and will absorb water. This will degrade the coatings and the lens will fail. If you have a stubborn spot try using a little Acetone to clean it.