[JimInWoodstock]

I purchased a chinese machine from MornTech USA. It has a 100 watt RECI tube. It came with a 1.5 in fl lens. I am not sure which chinese manufacturer made the machine. It has a black cone with an air assist on the laser head. I would like to change the lens to one of longer focal length. I can get an replacement lens on ebay in quite a few focal lengths. I would like to use at least a 2.5 in lens and possibly a 4 in fl lens. The question is how long can I go with the current metal cone? Is there limits on the focal length with the factory supplied cone, or can I just replace the lens with almost any focal length? Btw, the original lens is a GaAs type and I would replace it with the same type.

[Dean448]

Longer focus lens cause the beam to be larger as it exits the cone. That really isn't a problem unless the beam exits the cone slightly out off center. The problem is beam power is reduced. So you need to be extra careful the beam is centered on the lens.


Sent from my iPhone using Tapatalk

[thunderlaser]

Hi
I suggest that you should be buy a new laser head(don't need including the 2.5 or 4 inch lens) for suitable with the 2.5/4 inch lens.
The 2.5'' lens or 4'' lens will cause the focus length became to longer, at the same time the beam to be larger when it is inside of the cone.
Then the laser beam will may hit the edge of the cone, or the laser beam can't coming out of the cone completely.
It will lead to the power to be reduced, or no power completely.
So i suggest that you can buy a new laser head with match the 2.5'' lens or 4'' lens from the manufacturer. (or the machine agent in USA )
Good luck to you

Sincerely
Tom
Thunderlaser- leading provider of laser cutter and laser engraver from China

[Dean448]

You could also remove the cone and rig the air line to blow on the work thru a semi rigid nozzle. Just don't splatter debris back up at the lens

It's easy to check where your beam is relative to the hole in the nozzle. Just test fire into a piece of painters tape that's stuck on the end of the nozzle.


Sent from my iPhone using Tapatalk

[lasergirl.guru]

Jim:

100w with a 1.5 inch lens? Thats crazy. The different focal lengths provide different spot sizes. 1.5 - 2 inch lenses are best for super fine engraving which you wont be doing with a 100w laser tube. 2.5 inch lens is good for cutting wood and most materials. If you are looking to cut acrylic 1/2 inch or thicker, you may want a 4 or 5 inch lens. The reason for this is two fold: 1) you can focus into the center of the material to get a straighter edge and 2) to keep the debris away from your lens.

Depending on the design of your laser head and where the lens sits, you should be able to just replace the lens. It is very important to make sure the laser from the third mirror down through the tube is straight. Begin with the lens installed and make a small spot on a piece of scrap. Then remove the lens tube and fire the laser again. You should have a big spot. If the big spot is aligned to the small spot, yu are straight down. If not, move the big spot to the small one using your adjustment knobs.