Tube Life / Air cooled 50W?

[sp1nm0nkey]

The main hangup I have on the chinese lasers is that I've heard the laser tubes don't last very long, though it's been a long time since I've checked in. Ideally I'd like to get an air cooled tube because having to provide a constant source of DI water is kind of a pain but... if I run the tube on ONLY DI water or get an air cooled tube, how long can I expect the tube to last? Also, is there a large variance in the time that the tubes will last, as in... some will last 100 hours of constant use vs. 1000 hours of constant use due to inconsistent manufacturing, or is tube life fairly consistent?

Also, are there 50W tubes that are air cooled that have a good reputation?

[zax15uk]

There is a fundamental difference between the Chinese water cooled tubes and an air cooled (metal tube) laser.

It is not unreasonable to get 1500hrs from a Chinese tube, but they can also fail at much lower hours. Early failure is usually due to over heating (poor cooling or running at 100% for extended periods), although manufacturing defects are also possible.

The air cooled tube may last 10 times longer (or more) but the cost is typically 10X also.

Another variable is that an air cooled tube will typically output more power for the same rating, so a to 25-35W air cooled tube is equivalent to a 40W Chinese tube.

An intermediate option might be a Synrad metal tube that uses water cooling, they offer a 50W (actually 2 x 25W combined) that is at least as powerful as a 60W glass tube.

Zax.

[sp1nm0nkey]

Does the difference actually have to do with the cooling? Are you talking DC vs. RF coupled lasers? Are all high power DC lasers water cooled? What kinda tubes do Epilog/VersaLaser use (looks RF coupled). I always thought the output power was measured by some kind of photodiode... so it was 50 watts or joules/sec at the photodiode or something, so the pumping technology shouldn't make a difference, right? Or am I missing something...

Anyhow, what should I expect to pay on eBay for something equivalent to the tube they use in an epilog 50W?

[Litografa]

Usually all RF tubes powered up to 100 wt are air cooled. More than 100 Wt - water cooled. Epilog, Trotec, GCC use tybes from Synrad, Coherent DEOS or Rofin Sinar (type of tube depend from power and date of laser engraver production). ULS use own tubes. Disadvantages of their tubes - ellipse dot, dot size 20% bigger than on Synrad. Advantages - cartridge type - you can buy laser with 25 Wt and when you need you can easily make upgrade to 60 Wt - just remove old tube and put new.

I agree with Zax, but in addition want say two things:
1) Not possible buy glass tube for stock as they have limited storage time.
2) When you do some calculation do not forget electricity consumption. RF laser need electricity like office printer, chinese laser's with proper cooler power consumption will be at least 3000 Wt.

[zax15uk]

Regarding power output, yes you are correct BUT the ratings put on the Chinese tubes are not measured output but theoretical or in some cases just an over estimation.

A 50W Synrad or Rofin laser will output >50W and is usually provided with a plot of the output from a certified meter.

If cost isn't a concern then an RF excited metal tube is the way to go, it will last much longer and be more consistant. If the machine is for a hobby or cost is a significant factor then the Chinese tubes are a great option, and you can replace them several times and still save money.

Zax.

[sp1nm0nkey]

I homebrewed a servo system and have some linear rails lying around... I'm sure it'll be cheaper to just build my own system around a rofin sinar/synrad/coherent laser. What should I expect to pay/should I pay for a 30W or 50W RF tube on ebay?