New Laser Tube

Hello everyone,

After talking to a few people and doing a bit of research, I found out that laser tubes do not just “burn out” instantly, like a light bulb. They gradually loose cutting power over time.

Since about December I started noticing that some of my material (including printer paper) wouldn’t consistently cut through on settings that it had easily cut through in the past. So I just kept adjusting my powers up and my speeds down. I work with wood a lot and densities vary with different pieces of the same species of wood so I thought nothing of it.

Yesterday was the first time I officially compared these specs. I had a piece of material 1/4" thick that cut completely through in the past on settings 10, 70. 68. Yesterday after planing that exact same piece down by half to 1/8", it didn’t even cut through at settings 8, 90, 90. I did check that the Z was aligned, and all other standard trouble shooting was completed, etc.

I thought I heard a few others talking about having to bump up laser power recently. Has anyone else noticed that large of a difference?

I know they have a “shelf life” which is why we haven’t ever gotten a replacement. It might be a good idea to discuss buying another laser tube soon if this one is going bad.

Elly

I think this is a fantastic idea. Maybe we can take the time while the laser tube is out to permanently fix the sight laser as well.

Is the sight laser no longer fixed? I thought the bracket was holding up pretty well??

It worked well for me earlier tonight, and I’m planning to do repetitive lasering tomorrow night with folks to finish off the hands-on part of the lasering class series.

Jim

If we get a second laser cutter, wouldn’t it make sense to wait until the first one quits or is past being useful to fix it? If we buy a spare tube, which has a shelf life, then the clock starts ticking. Does anyone know what kind of delivery delay there is for a replacement tube? I think we discussed this a month or so ago at a meeting.

if the tube is going to have a steady decline, and since that equals longer times to cut stuff, if we aren’t going to replace it until it just doesn’t work, it might be worth re-evaluating the fee structure. :slight_smile:

When I was in the other day, I simply adjusted it back towards the center and was able to cut through 1/4" acrylic with the same settings I’ve always used.

Bill

Groovey.

No, full cuts, not grooves (winks)

It would be worth developing a model of cutting speed as a function of tube age in use hours to use for billing purposes.

I think what degrades is the mirror quality, I think the main other thing which might degrade is the electrodes.

Degrading cutting quality ate up about two hours of laser time when I was doing those puzzle boxes. I know because I timed how long it took to do one when I first started, and by the time I got around to cutting the majority of them later in the design process, I had to add about 5 minutes to each one. It wasn’t a huge deal since I could pass those costs on, it just made me aware of the issue.

Just to make sure, we are checking and cleaning the optics? Besides alignment which has been discussed, Wood for example has a tendency to smoke and can dirty lenses as well as mirrors over time.

Jim shealy

Hi,

I've been lurking on this thread and I just wanted to ask if you have a laser power meter?
It looks like a chuck of black metal with a meat thermometer sticking out of it.
That is the best way to determine output. If you request 50watts and only get 40 watts then something is wrong. I'm not sure if you can access the raw beam from the tube, but if you can, than you can isolate the optics from the loss. All mirrors and lenses will have some loss, but you can track things and troubleshoot the right thing to fix.
As always, be super careful working with the beam! Wear the correct protective eyewear designed for your laser and clear the room when working with the naked beam. Be safe.

Thanks,

Bradman

I just ran a few tests on the laser. I loaded a file I used from over a year ago when I was working on the Ultra-Bot and it cut exactly the same way it did then. It appears that someone did a fantastic job realigning it as well as getting the red dot (blur) thing back into a very good alignment.

I also did a four corners test and it was perfect.

Kudos to whomever did it.

Bill

Wonderful! Maybe that was all it needed.

If we could get our hands on a laser power meter as Brad suggested (even if we borrow it from someone for a day or so, as I have heard they are pretty expensive) it would be interesting to test the output in the future. Maybe determine what part of the optics needed to be cleaned, rather than cleaning all of it.

I found a simple 100W laser power meter on Amazon for ~$100.

http://amzn.com/B00EOMTSOO

I don’t have one anymore. :frowning:
They have a fancy digital one for ~$250.

I’m not sure how much power your laser unit has, you need to match the meter for your output. (if you only have 25Watts then a 100W meter may be overkill, and visa-versa)

They all pretty much work on the same principle of heating a known amount of material for a specific time and measuring the temperature increase. The cheap one looks like a block of anodized Aluminum and a calibrated meat thermometer. This is the kind we used at work. The digital ones just have a thermocouple mounted to a block of something and some calibrated software to output power level.
You could build one yourself but you end up chasing the calibration forever, usually cheaper to just buy one for a standard then go from there.

Good luck,

Bradman