I purchased the 1.5x beam expander to put on my machine thinking it wouldn't be a problem with the setup I have. I am using a 100w Reci laser with 25mm mirrors and the laser head with the 25mm mirror and 20mm focus lens. The hole to enter the laser head is 14mm I believe. Anyhow I installed the beam expander right after the output of the laser about 1 inch away and by the time the beam gets to the laser head, the beam is probably 20+mm. I thought the beam out of the 100w Reci was between 7 to 8mm, which would give a maximum beam size of 12mm. The size of the table is approximately 4'x5', but i thought the beam expander would maintain the size of the beam at a maximum of 12mm??? Am I missing something???
Thanks....
1.5x beam expander question
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Re: 1.5x beam expander question
You should measure the output right after the beam expander. It should be somewhat 12mm~13mm. The reason you have 20mm most likely is caused by the mirrors not being setup right at 45' degree, so the CO2 beam diverse out.
Regards,
Marco
Regards,
Marco
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Re: 1.5x beam expander question
I'll measure the beam right after the expander and see what it is. Am I correct in assuming that the beam should remain at 12-13mm all the way to laser head?? Forgive my lack of knowledge, but how does the mirrors not being at a perfect 45 cause beam divergence?? I thought once it went through the beam expander the beam would remain fixed.
Thanks Marco.
Chris
Thanks Marco.
Chris
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Re: 1.5x beam expander question
Hello Chris:
Forget my last post as it that scenerio shouldn't happen to your case (short distance route). The only possibility now is either faulty mirror(s) or wrong beam expander received. May be the manufacturer used wrong lens setup and instead of 1.5x lens, they may use 2.0x or 2.5x.
To test it, you may want to measure the beam diameter from the beam expander closed end. Then measure it again 1ft away and 2ft away see if you could get similar beam diameter or is it diverging or stay closed to the specification. Note, you may need to remove the tube from your machine and do it outside of the case. The best is to use a laser beam pointer (5mw) so it case no harm compare to a high power CO2 laser and easy to see the spot.
I'll test my beam expander with a laser pointer see how it works
Marco
Forget my last post as it that scenerio shouldn't happen to your case (short distance route). The only possibility now is either faulty mirror(s) or wrong beam expander received. May be the manufacturer used wrong lens setup and instead of 1.5x lens, they may use 2.0x or 2.5x.
To test it, you may want to measure the beam diameter from the beam expander closed end. Then measure it again 1ft away and 2ft away see if you could get similar beam diameter or is it diverging or stay closed to the specification. Note, you may need to remove the tube from your machine and do it outside of the case. The best is to use a laser beam pointer (5mw) so it case no harm compare to a high power CO2 laser and easy to see the spot.
I'll test my beam expander with a laser pointer see how it works
Marco
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Re: 1.5x beam expander question
Marco... I have attached a picture with three different beam shots. The first is the beam directly out of the laser. Looks like 6.5mm. The second beam is through the 1.5x expander and directly after reflection off of the first mirror. The third is just before the second mirror at the other end of the table. The distance between the second and third beams is 67 inches. It looks like the tiny pin hole that you can see directly out of the laser is exponentially expanding. What do you think?? I'll try the laser pointer as well. Just don't have one here right now.
Thanks.
Chris
Thanks.
Chris
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Re: 1.5x beam expander question
Chris:
You may want to find out the beam pattern without the beam expander. I'm suspecting that the tube you have may has higher divergence than usual.
What to do: measure the beam burn mark at the same location where you did with the beam expander. Check to see if the burn mark appear bigger at the second mirror when compare to the burn mark right in front of the laser tube.
I'm thinking that may be you should install the beam expander right before the 2nd mirror as you have very long traveling distance (67").
Marco
You may want to find out the beam pattern without the beam expander. I'm suspecting that the tube you have may has higher divergence than usual.
What to do: measure the beam burn mark at the same location where you did with the beam expander. Check to see if the burn mark appear bigger at the second mirror when compare to the burn mark right in front of the laser tube.
I'm thinking that may be you should install the beam expander right before the 2nd mirror as you have very long traveling distance (67").
Marco
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Re: 1.5x beam expander question
Thanks Marco... So here is the latest set of pictures without the beam expander installed. #1 is directly after the first mirror, probably 5" from the laser source. #2 is at the same position as the previous picture (67 inches from the #1). #3 is at the laser head at the farthest point on the table approximately 117 inches from the laser source. With the setup I have now WITHOUT the beam expander, I am able to cut 1/4" acrylic at 63% and 13mm/s. Is that about where it should be with a RECI 100w tube??
Thanks.
Chris
Thanks.
Chris
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Re: 1.5x beam expander question
Chris:
I found that using paper as testing target was not easy to tell the beam diameter as paper burned very quick. I tried both paper and think cardboard (MDF kind). The difference was so obviously. I tried a Reci 100W and I got very good beam diameter from 1ft to 10ft distance. On paper, the burned mark could be as wide as 12mm from 10ft away. But if it is used on a cardboard, the mark was merely 8.0~9.0mm.
I took some pictures and I'll post it here later. I found a funny issue: the bigger beam diameter happened at 5~6ft distance than getting smaller. I think some beam power first diverse out once it pass certain distance, it was getting weaker. But that my assumption only
I may do more tests by applying water on the paper and the MDF, that way the burn won't get diffuse out. That should give me better way to find the beam diameter.
Marco
I found that using paper as testing target was not easy to tell the beam diameter as paper burned very quick. I tried both paper and think cardboard (MDF kind). The difference was so obviously. I tried a Reci 100W and I got very good beam diameter from 1ft to 10ft distance. On paper, the burned mark could be as wide as 12mm from 10ft away. But if it is used on a cardboard, the mark was merely 8.0~9.0mm.
I took some pictures and I'll post it here later. I found a funny issue: the bigger beam diameter happened at 5~6ft distance than getting smaller. I think some beam power first diverse out once it pass certain distance, it was getting weaker. But that my assumption only
I may do more tests by applying water on the paper and the MDF, that way the burn won't get diffuse out. That should give me better way to find the beam diameter.
Marco
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