LaserUser.com Forum (formerly RDWorksLab)

I'm in the contemplation phase of a DIY build. CO2 glass tube or RF?

I only know glass tube. Does anybody have / used to have on of each?

Pros / cons between them.

Dave Vigness wrote: Thu Jul 16, 2020 Pros / cons between them.

i've used a CO2 tube as my own laser, and a RF (trotec) in a fablab when i discovered laser. from my opinion, the RF tube has not so much advantages. it is able to output very low power, where a co2 tube has a minimum power and you can not go below.

depending on your needs, the RF has full range from 0 to 100% power, and i believe the power curve is more linear, when the co2 need to be discovered and tuned for each tube.

the price is much higher for the RF, and it will be very costly to have a high power, where you can get a 100 or even 130W tube for not so much.

the RF is supposed to have a long life, but it will still decay over years, and the tube will lose power also, but not so much if you take care of not going past the mA recommanded by the brand (obviously, the idea is to get a true branded and tested tube). you can probably use 5 or more tubes for the price of a RF.

last thing, the RF is refrigerated by air only, so it may be difficult to use them in high temperature workshop, especially in summer when the air temps is over 25°c. but you don't have to care about a chiller, water circulation, ...

Hi,

i have been using a Synrad 48-5W tube for many years as a matter of fact the tube was manufactured in 1997 and is still working to date. Unfortunately the laser plotter around the tube gave up working earlier

It is watercooled and will produce around 800W of heat load so a beefy chiller is required. It works with 30VDC and a high amperage of around 28A.
Costs as a replacement if you send in your old tube is around 12000 Euros. So you can get around 10 good quality 100W tubes from RECI for the same price.

As Sebastien already described the only real advantage is a linear power curve and a range from nearly 0% (more around 3-4%) to 100%.
Also this specific Synrad tube is actually 2 25W tubes internally combined with a beam combiner and arranged at exactly 90° from each other so you will get a perfect round dot and a beam that is only 3.5mm and a mode quality TEM00 around 95%.

Advantages:

• Beam quality

• Power adjustment

• Lifetime - Imagine a 23 year old tube still outputting around 45W at a perfectly reasonable beam quality

Disadvantages:

• Price!

• If one of the RF transistors blows up, which can happen the repair costs can go up to 1000 Euros, if you can do it yourself, the transistor alone is 150 Euros

• Bulky and heavy for 50W...lenght of a 100W glas tube and around 20kgs of weight

• Strong chiller required

So the choice is quite difficult. If you have the money to spend and are into a more safe route with electricity (no HV DC required) then invest into high quality RF tube (and that excludes anything chinese, believe me!).

If you are comfortable with HV DC and don't mind changing the tube more often and have some "negative" effects regarding power curve, buy a branded SPT or RECI or whatever tube from a known good chinese manufacturer. Safes a lot of money.

Hope it helped
Greetings
Sven

Thanks to both of you.

I have an 80W glass tube now, and I didn't see a lot of advantages in the RF unit with a big negative on price. I have some ideas for a DIY build in my head and wanted to make sure I wasn't short changing myself by not looking to far at an RF set up. With that info in hand I think I will stay with the glass tube.

My understanding [?] is that the RF tubes will fire much faster, so they can engrave at much higher speeds. Is this incorrect?