Expensive lesson learned!!

[Nancy Laird]

On Monday, I spent most of the day cutting objects from 1/8" birch ply. I had the air-assist cone on the lens, to keep the smoke residue down, but couldn't figure out why I was still getting some smoke, until I noticed that I hadn't turned on the compressor!! Later that day, I tried to engrave a couple of name tags, but the quality wasn't as usual. Yesterday, I was trying to engrave some other objects (wood) and they weren't turning out good at all. LOML checked the lens, thinking it was dirty, and it turns out that I had fried the lens. :(

Fair warning: if you have the air-assist cone on the lens, be sure to turn on the compressor (ours is on a separate switch, as I don't always use air).

New lens = $230.00!!! Ouch!!!:eek:

I've now made a great big sign for the wall above the laser, to remind me to flip that switch!!!

I'm sure that none of you have ever done this, but fair warning is fair warning.

[Frank Corker]

Ouch is the word Nancy. Easy mistake, I'm sure we've all made big ones like you have with yours, maybe not as expensive though. I'm really shocked to see that damage was caused so easily. Did the lens crack or was it just the protection burned off. If it were the latter, can't it be recoated?

[Joe Pelonio]

I wouldn't expect lack of air assist to burn a lens, especially such thin wood where you run fast at low power. I wonder if it was already close to the end of it's useful life. Mine lasted just under 3 years.

Could be worse if your machine is air cooled and you forget to turn on the exhaust fan. Mine has an outlet in the side which is computer controlled
to turn on the compressor or fan prior to and for a few seconds after running a job automatically, though I don't use it.

[Mark Winlund]

Our machine will contaminate the lens within minutes without air assist. Even with air assist on, if the nose cone is not present, the cut time before contamination is only about 5 minutes. Of course, this depends on what you are doing. Marking aluminum has no effect on the lens, air or not. A quarter inch of wood is a lot of smoke.

Mark (still on our first lens after 5 years)

[Scott Shepherd]

Just to add to Mark and Nancy's points, the ULS uses a nose cone and the beam actually goes right through the middle of the nose cone, so when you use the air assist, it's blowing air directly down into the burn rather than a wash on the top surface (they have a wash type attachment as well).

The problem, and the manual states it clearly, that if you keep the nose cone on and run it without the air, it actually causes a vacuum and sucks the residue INTO the lens. So it'll smoke it up really really quickly. Yes, I know from experience too Nancy :) Didn't break it, but sure had me sweatin' one day and it took some time to get the baked on plastic off my lens.

It also works just like Mark said, if you turn the air on without the nose cone, then it'll suck residue into the lens as well. Been there, done that too.

Sorry you had an expensive lesson Nancy, but hopefully someone with a ULS system will gain from your mistake and not have to do it themselves. Thanks for sharing your bad day with us :)

[Nancy Laird]

Ouch is the word Nancy. Easy mistake, I'm sure we've all made big ones like you have with yours, maybe not as expensive though. I'm really shocked to see that damage was caused so easily. Did the lens crack or was it just the protection burned off. If it were the latter, can't it be recoated?

Frank, I didn't ask about getting it recoated (no, it wasn't/isn't cracked). That's going to be my next project, to see if it can be, and at what cost. It would be nice to have a spare in case I have another brain freeze!!:rolleyes:


I wouldn't expect lack of air assist to burn a lens, especially such thin wood where you run fast at low power. I wonder if it was already close to the end of it's useful life. Mine lasted just under 3 years.

This was running slow at high power, slow speed, cutting parts from the 1/8" ply. See Scott's post below about how the ULS air-assist works. Apparently it just sucked all sorts of junk up onto the lens.


Our machine will contaminate the lens within minutes without air assist. Even with air assist on, if the nose cone is not present, the cut time before contamination is only about 5 minutes. Of course, this depends on what you are doing. Marking aluminum has no effect on the lens, air or not. A quarter inch of wood is a lot of smoke.

Mark (still on our first lens after 5 years)

This lens is just a little over three years old (we purchased the machine two years ago from the first owner, who had owned it for about 15 months). Our other machine, the M-20 (20W) has a 2.0 lens that is still going strong - and the machine was built in 1996!


Just to add to Mark and Nancy's points, the ULS uses a nose cone and the beam actually goes right through the middle of the nose cone, so when you use the air assist, it's blowing air directly down into the burn rather than a wash on the top surface (they have a wash type attachment as well).

The problem, and the manual states it clearly, that if you keep the nose cone on and run it without the air, it actually causes a vacuum and sucks the residue INTO the lens. So it'll smoke it up really really quickly. Yes, I know from experience too Nancy :) Didn't break it, but sure had me sweatin' one day and it took some time to get the baked on plastic off my lens.

It also works just like Mark said, if you turn the air on without the nose cone, then it'll suck residue into the lens as well. Been there, done that too.

Sorry you had an expensive lesson Nancy, but hopefully someone with a ULS system will gain from your mistake and not have to do it themselves. Thanks for sharing your bad day with us :)

Thank you all for the words of support (sympathy?). Actually, knowing that I'm not the only _____________ (insert your own word here) in the world is pretty comforting. But the sign stays up until hubby figures out a way to have that compressor come on automatically.

[Lance Zimmerman]

I have the laser, exhaust blower, and air compressor all plugged into a surge protector so when I turn on the surge protector everything comes on.

[Mike Mackenzie]

Nancy if the lens is not cracked try using Acetone to clean it don't soak it because it will release the glue that is holding it into the bracket. Just use q-tips and gently try to clean it. We have cleaned up lens that you never would have guessed would still work.

If it can be cleaned up then you will have learned another expensive lesson and you would have a back-up.

[Rob Bosworth]

Lance, I do not know what laser system you have, but most of the manufactures recommend not using a power strip with your laser. They have caused all kinds of niggling little problems on machines of some of my customers. Most of the power strips are cheaply made, and noise (electrical strays) travels all over in the outlets. Also, you probably do not want other things attached to the circuit that your laser is on. Surges can cause problems with your laser system's electrical and electronic components.

Joe, Epilog put the outlet on their TT's so owner's would turn their exhaust systems on when the turned their machines on. That particular model did not have fans to circulate air around the laser. The design calls for air to be sucked into the system, past the laser cooling fins, then through the engraving area, and out with the effluents of the laser engraving. Great concept, except the outlet draws too much power through the system. It tends to burn out the power supplies faster than if you did not use that outlet.

[Bob Cole]

Sorry to hear about your lens Nancy. I had a similar thing happen to me a few months ago that I posted. I had the air assist on, cone on, software controlled turned on but the main setting on the laser had the incorrect setting so although I could hear the air on, the computer controlled air assist wasn't sending air to the cone. I was cutting that Eiffel tower out of wood so lens was fried before the first piece was done.

[Brian Conklin]

You said

Our machine will contaminate the lens within minutes without air assist. Even with air assist on, if the nose cone is not present, the cut time before contamination is only about 5 minutes. Of course, this depends on what you are doing. Marking aluminum has no effect on the lens, air or not. A quarter inch of wood is a lot of smoke.

My ULS doesn't even have air assist and after almost 3 years I have not had a single problem...........

I must have a great machine and exhaust?

[Tom Ravenscroft]

Looks like i may have a similar problem. I cut some plywood on my new machine that made a lot of smoke and may not have had the air on when i started cutting.

I am experienceing a loss of cutting power. My lens has a hellow tinge, is that normal or is it the smoke that has coated it?

Regards

Tom

[Dave Johnson29]

My lens has a hellow tinge, is that normal or is it the smoke that has coated it?


Hi Tom,

It is supposed to be yellow. It is Zn-Se Zinc-Selenide and is transparent to the CO2 laser wavelength. There could be smoke residue on the lens and is a good idea to check and clean regularly. Your manual should have instructions for doing so and also the materials required.

[Angus Hines]

Look like this ?

[David Fairfield]

Wow, dang. Well, $250 isn't too bad, considering its a high precision part.

On the Epilog, air assist is pretty much optional, I only use it when necessary for flame dampening. Mostly I have it off to lower the noise level. The lens stays clean for many hours of cutting on exhaust air only.

Dave

[Rob Bosworth]

Mark, I would guess you have an exhaust problem if your lens is getting crudded up in less than 5 minutes of cutting without the air assist cone on. Those big machines need a bunch of air moved to properly evacuate the effluents. Your lens should not get contaminated that quickly, unless smoke is roiling around in the cabinet too long.

Tips to maximize your exhaust system.
Minimize any constrictions in the exhaust venting system: smooth bore exhaust ducting. The larger the diameter of the vent ducting the better. Minimize number of elbows, T's in the system.
Most of the exhaust blowers we use have more suck than push built into them. Place the exhaust blower towards the outside vent rather than closer to the laser. This will increase the efficiency of the exhaust system.
Periodic cleaning of the exhaust system. You wouldn't believe how quickly crud builds up in an exhaust system. If your exhaust ducting has some kind of cap or screen to keep the critters out, check to make sure that filter or screen is clean to allow maximum air flow. If you find that your exhaust blower has a lot of build up on the vanes, this will reduce air flow. (I will take the exhaust blower outside, then very carefully throw in some cracked dry corn into the intake side of the blower. Be careful, cause it makes a terrible racket, and shoots corn and "stuff" all over the place. Also, don't use too much "abrasive" corn, you don't want to break the vanes on your exhaust blower. I use corn because it is readily available and pretty hard.)

[Rob Bosworth]

Mark, I would guess you have an exhaust problem if your lens is getting crudded up in less than 5 minutes of cutting without the air assist cone on. Those big machines need a bunch of air moved to properly evacuate the effluents. Your lens should not get contaminated that quickly, unless smoke is roiling around in the cabinet too long.

Tips to maximize your exhaust system.
Minimize any constrictions in the exhaust venting system: smooth bore exhaust ducting. The larger the diameter of the vent ducting the better. Minimize number of elbows, T's in the system.
Most of the exhaust blowers we use have more suck than push built into them. Place the exhaust blower towards the outside vent rather than closer to the laser. This will increase the efficiency of the exhaust system.
Periodic cleaning of the exhaust system. You wouldn't believe how quickly crud builds up in an exhaust system. If your exhaust ducting has some kind of cap or screen to keep the critters out, check to make sure that filter or screen is clean to allow maximum air flow. If you find that your exhaust blower has a lot of build up on the vanes, this will reduce air flow. (I will take the exhaust blower outside, then very carefully throw in some cracked dry corn into the intake side of the blower. Be careful, cause it makes a terrible racket, and shoots corn and "stuff" all over the place. Also, don't use too much "abrasive" corn, you don't want to break the vanes on your exhaust blower. I use corn because it is readily available and pretty hard.)
Run a flexible metal strip down through your exhaust manifold to knock out build up in the machine itself. Some systems allow you to remove the exhaust manifold on the machine. If your machine does not allow you to remove that exhaust manifold, then stick your shop vac into the exhaust port, then run a flexible strip of metal up and down through your exhaust manifold to knock out as much of the junk as possible.
Remember, a clean, efficient exhaust system makes for a happy laser system. A clean laser system tends to run better and much more reliable than one that is dirty.

[Benedict Roussos]

well dear friends,
either I am lucky or I have the gratest laser ever made.
I have several times forgot to open the air with the cone and the only damage was a dirty lens. For 4 years now I had the water trap of the air in a wrong place. Many times I saw moisture on the lens and on my work , but that was all. ULS has great lasers!!!!

[Mark Winlund]

Mark, I would guess you have an exhaust problem if your lens is getting crudded up in less than 5 minutes of cutting without the air assist cone on. Those big machines need a bunch of air moved to properly evacuate the effluents. Your lens should not get contaminated that quickly, unless smoke is roiling around in the cabinet too long.



Rob... actually, I am pretty fincky about how clean the lens is... I don't like to see any trace of dirt on it. If I wanted, I could probably let it run three times as long without damage. It's when the dirt gets thick enough, then the energy from the laser starts heating the dirt, which then ruins the lens. At $500 a pop, I don't want to get anywhere near that situation!

More than likely, the air assist system was designed to operate properly only with the nose cone on. I suspect there are some flow and turbulence problems without it.

Generally speaking, I can do quite a bit of engraving or cutting on wood with the exhaust turned up (I have a 3 hp high pressure blower with a VFD on it. At maximum speed, it actually distorts the lexan cover on the machine.)

I use the honeycomb table almost exclusively, and as you know, the HT has it's own air ports into the exhaust system. Just above these ports are another set of ports to draw air across the top of the table and out. These ports can be blocked off either partly or all together, delivering less or more "suction" to the HT. I use the HT table mostly to keep things flat, so there is a compromise between flattening and air exhaust! Thus the problem.

I have designed and built (but not tested yet) a vacuum table system that is independent of the air exhaust system to try to address these problems. Some of the veneers I work with look like a potatoe chip and have to be kept quite flat to get the precision I need. (Photo attached)

Mark