Laser tube size

Hi all , looking for some words of wisdom. I have a K40 which works great at the minute and I am starting to make me some money on ebay. I am currently building a bigger laser inspired by further fabrication on Youtube. I intend to cut mostly 3mm MDF.

My Question.

I was thinking of buying a decent 40 watt tube for the new laser that would ultimately be replaced for an 80 watt when the coffers get recharged. I could use the new 40 watt as a spare for the K40. Is this a mad idea should I go straight for an 80 watt tube for the new laser and forget the K40. Thanks in advance. Alan Downpatrick NI

Things to consider for your upgrade

80watt CO2 glass laser tube substantially larger in size then 40watt
Will your current case accommodate the larger tube…? pretty sure not
If it does you will need a cover to protect the part of the glass tube that sticks out
You will need a new power supply

A Reci 80w tube and power supply will cost more then your current machine.
Maybe you want to look at a whole new machine that you dont have to tinker with and save money and time in the process.

Do you really need 80 watts to cut 3mm. I think it’s overkill but that’s just my opinion

Good Luck


Most of the time over kill is better than under kill. An 80 watt laser cutting 3mm MDF would probably last for decades, plus eventually you may want to do other things that a 40 watt can’t do.

Why stop at 80w ho for 100w while you are at it. I agree with @olddogTim if you can go as big as you can afford


I had a Chinese 40 watt and gave it to a friend ( did not cut my leather ) so I got a Samger 80 watt ( Chinese) and I was pleasantly surprised what a difference. My only complaint is the 12mm focus lens. Not much choice in that size.

Wow not used to seeing that size

Yeah I know neither do the companies that sell lenses !

Maybe this helps you @olddogTim

TEN-HIGH Diameter 12mm Focal Lens for CO2 Laser Cutting Engraving Machine, FL: 1" (1"/25.4mm)

Cheers :beers:


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Thanks everyone, for the comments, I will do some pondering :slightly_smiling_face:

The bigger and more powerful the tube - the better?
Not really so. for cutting hard stuff faster?, - Maybe. for engraving soft materials - not so.
you would need to lower the power to just above the tube’s threshold which is high(er) as it is and raise the speed accordingly and that alone will introduce many unwanted artifacts. chose the right machine and configuration for the job.

Archeologists :heart: artifacts… JK. Turning up the speed on the head to compensate to a stronger laser substantially decreases the quality of the engraving.

For engraving the less power in the laser the better. To be convinced of that fact just look at some of the amazing photo engravings our very own @Bulldog achieved with his diode laser on tile.

So bigger and stronger more powerful is not always better.



I got 12mm (dia) focus lens in 1 inch 1.5, 2 (stock) 3, and 4 inch. Currently using a 12mm dia 4 inch FL lens in the II-VI material.

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can you get a, ll-Vl 12mm meniscus lens? If so where?

I will contact the folks I got mine from and ask. From my understanding, the meniscus lens should provide a smaller dot.

Regarding laser size / power: don’t forget to account for what you want to do with the laser most. If only worrying about cutting than sure, all the above applies. But if you want to do fine detail engraving, smaller is actually better. I used to have a 120W laser and it was basically useless for engraving because the minimum power it would fire at was ~20% - which is typical for most CO2 tubes. But 20% of 120W is still 24W (I know, it’s not linear in reality - just an example). But 20% of 40W is only 8W. The way the commercial lasers get around this problem is to just move really fast which high precision control systems. But unless you are going super high end on your custom built laser and using closed loop servo-steppers and such, that’s not an option.

I have a W6 Reci rated around 140 watts and in no way is it useless for engraving. I do agree you need to move faster, and that is the goal (faster production). I also have decent Yako 3 phase steppers and drivers.

You can also effectively reduce power for slower and finer detail through optical techniques (reduction of air assist, lenses with less light transmission,less fume extraction). But generally, it is speed and the reliability of very quickly accelerating and negatively accelerating without skipped steps or backlash.

I think the ( ll-VI ) is the name of the company the material is ZnSe. I can get plano convex , but not II-VI meniscus in 12mm