Laser thickness issue

[wickedboysap]

I have a chinese 80 watts laser machine which is having an issue with the output of laser thickness from the laser tube. At the point of out put the laser thickness is about 6mm and as it travels along the mirrors at the last mirror it is almost 2cms, does anyone know why this is happening and whats the solution to this problem.

Thanks

[Laserman FLE]

That is normal and is called divergence of light.

Are you running a poalizer or beam expander?

[wickedboysap]

Nope there is no poalizer or beam expander and surely it is not normal the size of the beam is bigger then the mirror itself I am sure that is not normal.

[bpoulin]

How big is your machine, I don't think they realized the size difference because of the way you worded it. 6mm to 20mm. At first I thought you were saying 6mm to 2mm and I was wondering what the problem was lol. I had to read it again.

[keebler303]

It is normal for a Chinese laser tube. The "good" quality laser tubes (Synrad, Coherent, etc.) all spec very low beam divergence, you see why its important now. It could also be that one of your mirrors sucks (not flat) and it is causing the beam to diverge but its probably just because of the poor quality tube. There is good reason why an American tube is $20,000 and a Chinese tube is $1,000.

Matt

[bpoulin]

Originally Posted by keebler303 It is normal for a Chinese laser tube. The "good" quality laser tubes (Synrad, Coherent, etc.) all spec very low beam divergence, you see why its important now. It could also be that one of your mirrors sucks (not flat) and it is causing the beam to diverge but its probably just because of the poor quality tube. There is good reason why an American tube is $20,000 and a Chinese tube is $1,000. Matt

I STRONGLY disagree with this statement about the tubes, I have a 1200x800 machine with an 80w "chinese" tube and my divergence is less than .5mm. Now as far as a bad mirror that is a good thing to check, and cheap too.

[Laserman FLE]

Now that I think about it that sounds about right if you are working on a large table. My 100W Universal with a 6x beam expander is about that size entering the cutting lens. My table is 48 x 48

What is the problem? Are you not able to cut?

[keebler303]

Originally Posted by bpoulin I STRONGLY disagree with this statement about the tubes, I have a 1200x800 machine with an 80w "chinese" tube and my divergence is less than .5mm. Now as far as a bad mirror that is a good thing to check, and cheap too.

:

Not sure where you get .5mm from or how you can even measure it on your machine but I doubt it. A top of the line Synrad laser has 4mR full angle beam divergence. Over 1200 mm, the beam grows by nearly 5mm. So you are telling me your $1,000 laser tube has 1/10 the divergence of a $20,000 tube? If thats true why don't all the high end laser cutter manufacturers use these tubes? Why do they spend extra money on beam expanders and collimators if they don't need them?

Regardless of that, I'm not saying that none of them are good, its more about quality control. It seems to be the luck of the draw on whether or not you'll have something worthwhile when it arrives.

Matt

[keebler303]

Originally Posted by Laserman FLE Now that I think about it that sounds about right if you are working on a large table. My 100W Universal with a 6x beam expander is about that size entering the cutting lens. My table is 48 x 48 What is the problem? Are you not able to cut?

Its not so much about the size of the beam, but its divergence. Your beam is big but its the same along the entire beam path. If the beam is 6mm on one end of your gantry and 20mm on the other, your focused beam will vary greatly over the distance. Engravings will be deeper on one side, cuts will get funky, etc. It is a big problem, thats why decent lasers (like Universal) use a beam expander to get a consistant beam width (and therefore consistent cut)over the entire work surface.

Matt

[Laserman FLE]

What most people don't understand is what the beam expanded does. We design our universal based cutting systems with the 6 x and 2 " mirrors and 1.5" dia lenses. Our synrad 100 w uses a smaller x expanded and smaller mirrors due to its better beam quality and divergence. This is why I have to charge 30k for a 100w 48 x 48 system and the chineese can charge 8

[Litografa]

All your posts about divergency are right ) but I think wickedboysap have something REALLY wrong with tube/optics as 6 mm at output clearly show this
Do you have another tube to compare results?