[DLDude]

Hello!

We have an 80W rabbit laser. Bought it last year and have use it a fair amount. Has maybe 3-500 hours on it. Our biggest problem has always been cutting through 1/4" MDF. In the past few months it has become nearly impossible to do in 1 cut. We have slowed it down to 3% speed and 100 power setting and it still has a hard time in certain parts of our table. I've been reading through this site and I can't seem to find what it could be.

I guess my question is this: Is there a good checklist of things that slowly go wrong over months and months? I have heard if the tube goes bad it is a BIG difference. I have also heard that mirrors wear out slowly, and so does the lens. We have cleaned both many times to no affect. The mirrors look very clean and nice, so how do we know when they are on their last legs? Any ideas?

[RossMosh]

It's most likely not the mirrors. It's far more likely that the tube is just on its way out. These tubes aren't exactly made well and they are constantly leaking CO2. These tubes also don't love being run at full power. Maybe Rabbit already limited the power for you to save the tube but it's typically suggested to run about 5-10% under max power if you can.

[DLDude]

Is there any way physical way to tell the condition of the tube itself?

We haven't run it at 100% power for the whole year, maybe just the last 50 hours or so.

There also seems to be a gunk on the inside of the laser tube exit.



Signs are pointing towards a laser tube problem.

[Melody-gweike]

If you have a AMmeter on the machine, it's much easy to see whether a laser tube becomes weaker or not.

Check the laser way and clean the mirrors & lens, if all make no difference, i suggest you to change a tube.

[Exsecratio]

Ummm where is the lens protector from the end of the tube?

Melody, an ampmeter will often give a false reading as not only the tube can cause low amps but also a failing power supply. The only way to check a tube is with a laser power meter and even then it could also be a psu failing or running underpower.

Dude, 50 hours at 100% can seriously shorten the life of a tube, I tend to agree, it may be tube replacement time 100% on a chinese power supply can sadly often mean up to 110% of the tubes maximum working load. Chinese PSU's aren't known for giving stable amperages and can often run over their stated maximums meaning at a machine setting of 100% the tube is being driven at up to 110% of its rated maximum.
Most of the tme slow degredation of power means the tube is dying.

best wishes

Dave

[DLDude]

I appreciate all the help. Kind of stinks because it still cuts out our 1/8" Birch great, but is useless if it can't cut the 1/4" MDF.

As far as tubes go, I noticed there are two types these days. One has 2k hrs and one has around 8k hours (RECI). Is it worth getting the longer-life one? Is the quality increased?

[Andrea1951]

I have to disagree! Typically Fast drop in power (one to two days) is tube. Slow (weeks ansd months) drop is mirrors and lens. It sounds like you need to check the 90 degree mirror at output of the tube, and/or the lens in the isolution tube that goes through the back wall of the table chamber. If your not suppling enough suction in table chamber, you may be loosing laser penitration because the smoke raising from the cut, filters the beam. That too would slowly clog up and appear to reduce laser power.

[Exsecratio]

Hi Andrea,

There is a little more to it usually,following is just a small sample,

Instant loss of power without any arcing:

Power Supply Failure (Fuze, voltage regulator etc)
Flow control meter
Door interlock

Power instant loss with Arcing:

Dead tube with volts taking path of least resistance to earth.

Power reduction over time:

Hours:

Water temperature

Days:

Dirty mirrors
Dirty lens
Dirty tube beam coupler

Weeks:

Slow degradation of tube due to age, gas permeation of the walls, electrode erosion inside tube.
Slow failing of power supply high voltage side.

Sadly it's usually impossible to say with certainty what is causing any given change unless a number of variables are taken into account.

Dude,

At risk of upsetting a few RECI diehards the tubes are indeed very good but do tend to suffer from a honeymoon period where they punch well above their weight, yes it's true they can last 10,000 hours but over that time you will find your 150 watt tube will slowly end up performing like an 80 watt tube. A good quality 100 watt will often outperform a RECI over time, sure on spot test the RECI will come out top but that isn't always the best or most accurate view of them.
I'd rather have an 80 watt tube that gives me 70 to 80 watts over 2 years than a tube that starts at 130 watts and after 3 months is down to 75 watts. It means changing files and cutting speeds and all that takes time,time costs so saving money by having a life of 10,000 hours may not actually be the best economy after all once you add in all the fiddling with speeds and feeds as the tube degrades.
Also note a bubble in the mirror chamber of the tube will have no more respect for a RECI than it will a Yingpong Ltd cheapo tube that costs 50 bucks.It will still kill both of them equally well
For reliability RF excited systems are the way to go IF you can stand the running costs of regas or replacement.

best wishes

Dave

[DLDude]

Where would be a good place to purchase a high-quality 80W laser tube that would fit our Rabbit? I'm not sure we're quite ready for RF, but we do value quality if it will reduce headaches over time.

[Exsecratio]

I'd be looking at one of the 3000 hr tubes in all honesty, they are a little better quality but don't have the niggles of the very cheap stuff. The 1000 - 1500 hr tubes are really the basic Chinese junk so you need a make that sits around the 3000 advertised hours and a different make to the el chepos.
Its a really hard call, sometimes you will find tubes that are 1500's sold at 3000's at inflated prices.
The coletech tubes seem to be good and last up to 3 to 4000 hours if you don't cook them. (Ebay)
Go for a full length tube though, part of the problem with Reci's is they gain power through volume and not length when laser generation is really a product of the length of the tube and not so much the gas capacity.
Full length tubes tend to give smoother power delivery whereas stubbys tend to go for grunt rather than finesse
Remember though many tubes are produced by the same companies and just rebadged for distributors, check out the claims and look for a seller with reliable feedback on the model you want. Cole CNC in China seem pretty good and thus far I've had no problem with their stuff. (a LOT cheaper than branded RECI's as well)
I'm sure there will be 10 or so distros running amok here telling you their tube is the best but as I don't work for a tube maker or distributor I have nothing to gain whatever tube you buy

best wishes

Dave

[Greolt]

We have slowed it down to 3% speed and 100 power setting and it still has a hard time in certain parts of our table.

Everybody seems to have missed this important clue. ......on certain parts of the table.

Classic symptom of alignment issues. Clean your mirrors and check alignment.

Greolt

[clayne]

I have a rabbit 60watt. I noticed that after realigning the mirrors, good cleaning, I could cut stuff like hot butter for first 3 days. Now it's back to same old slow cutting. Thinking of "realigning" the mirrors again. Hey, it worked before... who knows. I really don't think or have any idea why the mirrors would change, I don't move the machine at all. It does however get alot of vibration from the gantry during large etching.
I will note however that I rarely if ever crank the tube to 100% regardless. I try to keep the power below 80 on most stuff, even if speed is slow as a turtle. Just my paranoid thinking I guess.

[lrob]

MDF, that may be your problem and not the tube. Mdf can vary greatly in its makeup and the lasers ability to cut it.

I always try and look for the light colored stuff which has less glue and is much easier to cut. I cut it at speed of 9 and 100% power with a 80 watt chinese unit. I always cut everything with 100% power. Have had my laser for about 1-1/2 years.

[Exsecratio]

You really should use Medite, Medite is MDF that uses a water based glue, other types can contain formaldehyde and give off some pretty nasty fumes.Laser MDF uses water based glues and will give a much better finish.

Running a tube at 100% can also cause issues, the Chinese power supplies spike and don't hold the most stable of voltages, if they are peaking at over the requirement they can cause early failure of tubes. Running at 90% is a safer bet than running at 100% all the time.

best wishes

Dave