Replacing my 80w CO2 tube. Got any advice/tricks/warnings?

[Bob Crimmins]

My current tube appears to be under performing so I'm going to change it out for the backup tube that's been sitting unused in a box for a couple years. It's my first time installing a tube so I'm suitably anxious to get it right. All the tube replacement videos make it look uber simple; maybe it really is. But thought I'd check in with you pros before taking the plunge. Aside from dropping the tube on the concrete, anything I can do to screw the pooch on this?

Thanks,

Bob

PS. I'll be starting around 2pm PST and will check this thread before doing so.

[John Noell]

Installing mine was quite simple. Basically, make sure it is aligned so it's pointing right at the centre of the mirror (I had to mve the supports a little bit), hook up the water and get any bubbles out (I just rotated the tube a bit, back and forth), hook up the wire at each end (use a little silicone on the high voltage lead, and slide the sleeve over the end to make sure there is no arcing) and you're done.

[Dave Sheldrake]

Don't be surprised if that 2 year old tube is dead my friend :(

cheers

Dave

[Bob Crimmins]

I wondered about that. I've never got a definitive answer on tube shelf life. Does shelf time count toward it's life time duty cycle? Is it constantly off-gassing even when the machine is shut off or when it's just sitting in a padded cardboard box?

On that topic, is there a way to test the output of a laser without investing $100 in a power probe?

[Chris DeGerolamo]

There was a post with a link not too long back that described the experiment on how to measure W using water and a thermometer. I can't find it now...maybe someone else will chime in.

[Dave Sheldrake]

There was a post with a link not too long back that described the experiment on how to measure W using water and a thermometer. I can't find it now...maybe someone else will chime in.

http://imajeenyus.com/optical/20130423_measuring_laser_power_thermally/index.shtml

Dr Lindsay Wilson


I wondered about that. I've never got a definitive answer on tube shelf life. Does shelf time count toward it's life time duty cycle? Is it constantly off-gassing even when the machine is shut off or when it's just sitting in a padded cardboard box?

No real definitive answer Bob, the biggest problem comes from small amounts of Oxygen in the tube gas causing the electrodes to oxidise and contaminate the gas, other causes are gas leakage via the joints on the glued tubes. I used to keep tubes in stock till I realised I was losing 40% plus of their useful life by having them sitting on a shelf, now I just call my supplier at HPC in Halifax and have one shipped down when I need it. Having a $500 tube die before being used is one thing but when you get to the $5,000 tubes losing power on the shelf it can get expensive.

cheers

Dave

[Bob Crimmins]

Thanks for seeding that idea, Chris.

Thanks for providing the link, Dave.

[Bob Crimmins]

Yeah a $5k tube evaporating into thin air would suck a lot.

Speaking of replacing tubes, is it practical to order one-off tubes from China suppliers? I've heard that the breakage rate in transit is very high. And then there's wait. But the prices look oh so low.

Oh yeah, and what about replacing an 80w tube with a somewhat higher power tube, e.g., a 100W (provided it would fit in the machine). Is that a 'thing'?

[Bill George]

So my question does a metal CO2 tube have a longer shelf or storage life as in a un-used machine setting for a while than the same wattage glass tube?

[Dave Sheldrake]

So my question does a metal CO2 tube have a longer shelf or storage life as in a un-used machine setting for a while than the same wattage glass tube?

Usually yes Bill, the *electrodes* are external to the resonator cavity so there is no real contamination issue. They can outgas but are usually built to a far higher standard than many of the glass DC tubes with the exception of Coherants or GSI slc series units. (the SLC costs about the same as an equivalent RF unit anyhows, although the SLC, Coherant and Radion tubes can be refilled)


Oh yeah, and what about replacing an 80w tube with a somewhat higher power tube, e.g., a 100W (provided it would fit in the machine). Is that a 'thing'?

80 - 100 is a waste of money to be honest Bob, the speed gains will be minimal and the loss of low power settings for engraving can be an issue, it's not always possible to run a 100 watt tube at a low enough power to get low enough power density for a given material. If you go down the *cutting laser* route of big tubes then go BIG, 130 to 180 where possible. Be aware though, tube replacements once you get into the 150+ range are expensive :( in effect, if you are going to lose the ability to do fine engraving you may as well make it worthwhile by adding big cutting ability. Strangely enough the spot size for a given lens is smaller on the bigger tubes as the incoming beam from the tube is usually far bigger, bigger incident beam to the lens = smaller spot size = higher power density.
Even at it's lowest setting my EFR180 watt won't engrave 2mm MDF without cutting right through it :(

cheers

Dave

[John Noell]

...and what about replacing an 80w tube with a somewhat higher power tube, e.g., a 100W (provided it would fit in the machine). Is that a 'thing'? My understanding is that you also need to change the power supply to match. But Dave Sheldrake is the expert on that. And the extra length (if you are talking glass tubes) can be a big problem depending on your machine.

[Dave Sheldrake]

Bejing EFR:

http://en.bjefr.com/

ZN Series

ZN-1250:
Length: 1250mm +/- 20mm
Diameter: 80mm +/- 2mm
Rated Power Output: 80 Watts
Maximum Power Output: 95 Watts
Working Current: 26 Ma

ZN-1450:
Length: 1450mm +/- 20mm
Diameter: 80mm +/- 2mm
Rated Power Output: 100 Watts
Maximum Power Output: 120 Watts
Working Current: 28 Ma

ZN-1650:
Length: 1650mm +/- 20mm
Diameter: 80mm +/- 2mm
Rated Power Output: 130 Watts
Maximum Power Output: 150 Watts
Working Current: 30 Ma

ZN-1850:
Length: 1850mm +/- 20mm
Diameter: 80mm +/- 2mm
Rated Power Output: 150 Watts
Maximum Power Output: 180 Watts
Working Current: 30 Ma

F Series:

F2:
Length: 1250mm +/- 20mm
Diameter: 80mm +/- 2mm
Rated Power Output: 80 Watts
Maximum Power Output: 95 Watts
Working Current: 28 Ma

F4:
Length: 1450mm +/- 20mm
Diameter: 80mm +/- 2mm
Rated Power Output: 100 Watts
Maximum Power Output: 120 Watts
Working Current: 30 Ma

F6:
Length: 1650mm +/- 20mm
Diameter: 80mm +/- 2mm
Rated Power Output: 130 Watts
Maximum Power Output: 150 Watts
Working Current: 30 Ma

F8:
Length: 1850mm +/- 20mm
Diameter: 80mm +/- 2mm
Rated Power Output: 150 Watts
Maximum Power Output: 170 Watts
Working Current: 30 Ma

F10:
Length: 2050mm +/- 20mm
Diameter: 80mm +/- 2mm
Rated Power Output: 180 Watts
Maximum Power Output: 195 Watts
Working Current: 30 Ma

RECI:

http://www.recilaser.com/en/products.htm

W Series:

W2:
Length: 1120mm +/- 20mm
Diameter: 80mm +/- 2mm
Rated Power Output: 80 Watts
Maximum Power Output: 85 Watts
Working Current: 27 Ma

W4:
Length: 1400mm +/- 20mm
Diameter: 80mm +/- 2mm
Rated Power Output: 100 Watts
Maximum Power Output: 120 Watts
Working Current: 28 Ma

W6:
Length: 1650mm +/- 20mm
Diameter: 80mm +/- 2mm
Rated Power Output: 130 Watts
Maximum Power Output: 150 Watts
Working Current: 30 Ma

W8:
Length: 1850mm +/- 20mm
Diameter: 80mm +/- 2mm
Rated Power Output: 150 Watts
Maximum Power Output: 180 Watts
Working Current: <30 Ma

Yup pretty much,

[Bob Crimmins]

Big news (well, for me anyway.)

As I reported earlier, the flame up cause by cutting 9mm acrylic at 2mm/sec. melted my drive belt and torched my focal lens. Replacing the belt was straight forward but a HUGE pain because of the terrible design of the belt fastening system. With that done, I then changed out the lens with one of the spares I had (50mm). Voila! I'm now cutting 9mm acrylic at 17mm/sec., not even a whisper of a flame up. It feels like I just tripled my laser power... without having to install that new tube! So this what I've been missing all along.

[Rich Harman]

Voila! I'm now cutting 9mm acrylic at 17mm/sec.

I can't cut that fast even with 130W. You sure about those numbers?

[Dave Sheldrake]

I'm with Rich, even a 150 watt DC tube won't cut 9mm acrylic at that speed run at a safe operating current, I'd check the PSU output it sounds like you are cooking the tube at that speed.

the standard speed for a 180 watt on 9mm acrylic is 16mm per second

cheers

Dave

[Bob Crimmins]

Ok guys, that was my bad. You are, of course, right that 17mm/sec. through 9mm would be pretty freaky for an 80w. I was testing a bunch of different materials and thickness so that I could reset my settings notes, and typo'd the settings I reported in my previous message. The 17mm/sec. time actually went with the 2.3mm acrylic. Since I was previously cutting that at 6mm/sec that was pretty frickin' cool. The 9mm acrylic time was 7mm/sec. (and that was smack dab in the middle of my previous "dead spot"... which is now gone.) As I said before, I previously had to crank way down to 2mm/sec to get through that. So getting that to 7mm/sec was an amazing 3.5x improvement. Rich, since that's still 2x the 4.5mm/sec. time you reported for 9mm w/ your 80w I was duly incredulous. This is my first and only laser and so I'm not a good judge of what "good" performance. But here's a the documentary evidence of the performance I'm getting.

As an aside, has anyone ever seen a chart of typical cut times for various material and laser powers?

302756


http://youtu.be/s2ipGFQ1Yqw

[Rich Harman]

Mine can probably cut at 7mm/sec at the far left hand corner, especially if I switched to a shorter lens. I cut at 4.5 so that the pieces will drop out, even the ones cut at the near right corner - which is furthest from the laser tube.

At any rate, 7mm/sec is really good. What can you do if the piece is at the near right corner of the table?