Focusing Laserbeam with Lightburn

I am having an issue with focusing the Laserbeam while using Lightburn.

The Lightburn “Fire” button has a power setting option. Using a G2 lens, I have set the power to various values: 2%, 1%, 0.5%, and as low as 0.01% which seems to be the lowest setting Lightburn will accept.

All of these values burn the wood about the same amount even with a quick on-off action. Since the focus actions burn the wood, it is difficult to make out the size for the beam. I have yet to be able to focus the beam real tightly.

Any ideas?

By the way, I intend to use Lightburn with he Laserbeam because it’s a sweet product that can drive the Longmill directly. No offense to UGS or gSender aficionados.



@ronboklein Ron: If using lightburn, be sure to set $32=1 and $30=1000. Then, in LB, set Smax to 1000 also. You can set $30 to another value, if you like. Some use 255. If you do that, be sure to set SMax to 255 also.

@gwilki - Grant, how high it your Z. If I remember correctly yours was about 1.75". I had mine set to 2.75". Both able to focus to a very small dot. @ronboklein - Ron, where is your Z set? What Grant said is your primary concern though. Also I don’t know what Sienci recommended.

The trick to focus the laser is to set the dip switch to the lowest setting then adjust power to 1 or 2%. This will make it visible but won’t burn. At the higher output setting even with the power at 2% it will burn making it impossible to focus.

One thing I have noticed at least with the G7 lens it is barely threaded into the laser for proper focus. Would be nice if the threaded portion of the lens was longer. Also, I noticed the gage to set distance does not have the same length legs. I always set it with the G7 leg down.

@Heyward43 The laser that I am using now has a best focal length between 2.125 and 2.5". I think that I am about in middle. I have block that I put on the top of the material. I lower the Z until the bottom of my mounting bracket touches the block. It seems to be working well.

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Just one point I am wondering: why trying to set the focal length to the top of the material to cut? I dont know much about laser cutting, but shouldn’t the focus of the beam be located in the middle of the material, or respectively one half of the cutting depth below the surface? Or is this not remarkable?

I focus my laser using a black anodized aluminum business card blank. You place the blank on your work surface and turn on the laser at a very low setting and slowly lower the z axis while watching the laser beam where it hits the blank (with laser safety glasses on). As the laser comes into focus the dot of light will get smaller and, on my blank at least, the beam at the blank will start to change color. As you continue to lower Z, and I’m talking very very small steps, you will start hearing a singing noise (very faint). When you hear this the laser is in focus. It’s pretty simple and is probably more accurate than some sort of gauge.

Regarding @JHahn s question, Lightburn does have the ability to drop the laser on consecutive passes. I’ve cut 1/8" BB plywood, in 2 to 3 passes, without having to do this.

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@paullarson I use the same method as Paul. Now that I’ve found that “perfect” height, I have a block that I use. I place it on the material and lower the Z by hand until my laser mounting bracket touches the block. This if the focus height.


@paullarson @gwilki
Thanks for the input guys.
I see an issue if you use a wooden block, the plastic gauges that Sienci provides or any other fixed measuring device. If you only use one lens, in this case the G2, that’s fine. As soon as you change to another lens, the new lens has to be screwed in to the laser head and focused accordingly.
If you go back to the G2 you need to refocus it.
Does the position of a particular lens in the head have to be turned to the same position every time in order to focus it or is the distance to the focusing ring the important part?

@ronboklein I think you are correct. To be honest, I just leave the G7 lens in my non Scienci laser all the time because I like the long focal length and its efficiency (i.e., power loss) is very close to the G2. So, if you never change your lens a gauge should work.

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@ronboklein Once again, I’m in a position similar to Paul. I only have the three element lens that came with the laser that I have. So, I only need one set up block.

I focused mine once at exactly 2 inces from bottom of the laser block . Then I simply use a 2 inch block on the surface of what ever I want to burn ,and bring the laser to the block . No more trying to focus I know it’s in focus.


I agree about the g7 lens, it is barely threaded to get the smallest focal dot. For me you can actually touch the adjuster ring and it’ll move the lens so I do not know if this will work real well or not as the lens could go in and out of focus with the cnc movement. Any thoughts on this?