Issues with Focal Distance for Fiber laser

LightBurn Hardware Compatibility Galvo
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I have an 30W Integrated Fiber Laser Engraver, and according to the manual, I need to raise the scanning head until the two red dot guides merge into one to get the optimal focal distance.
The problem I have is the red dots are so bright that I cannot appreciate the right moment when the two dots merge into one (around 245mm). The lens included with the engraver is # 210D30135 and it shows “f= 210 mm”. I know that 210mm is not the focal distance as the two red dots are far from each other at that distance., but then what is f=210mm?

BTW, I am not even sure is the lens is 150x150 mm (the manual s says that) because Lightburn detected it as 110x110 mm.

Since I am experiencing some issues when engraving objects (using 245mm), I wonder if the focal distance is indeed not the optimal because some engravings have areas with different colors at the ends, one side dark and the other side white. If I try to cut a small circle out of a 0.2 mm business cards, only half of the circle is completely cut.

Is there a way to find out the optimal focal distance with just the model # (210D30135)?

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I googled this and didn’t find anything that I thought matched, maybe a Monport? We usually look into your profile (click on name) and identify your laser. However you profile doesn’t show anything but grbl.

Nice to have a link to the machine we’re talking about, even if it’s just to look …

I quit using these because

  1. too bright
  2. I have to adjust them to another lens when I change to another lens.
    a. way too difficult to adjust them to long lenses.

This is focal length notation, but it must be an F210mm, so the focal length is 210mm. An F notation means it’s a flat focus lens or F-Theta scanning lenses.

I marked my column, first with a label maker, then cut out arrows out of copper for approximate location for each lens.

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The best way to focus, is to set it up to engrave, low speed, fill, low frequency and lower q-pulse width, use a piece of scrap.

When you move it up and down around the approximate focus point, it makes the most noise when in focus.

This works well for short lenses with a small depth of focus (dof). An F420mm (300x300mm coverage) has a dof of about 13mm takes a little more hunting.

The measuring sticks I use are on the fibers table, cut out of acrylic… You could cut them out of something else with your grbl machine…

Might want to try this video by Laser Everything about how to focus your machine and dump those stupid led things…

They also have settings for different materials… on their .net site.

Lightburn can’t tell which lens you have mounted, neither can the controller. If it’s figuring it out, it via the device settings, I would think.

Have any issues, sing out

Good luck

:smile_cat:

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Thank you Jack,

I found out the right focus distance and I am just making a measuring stick out of acrylic so I will not use use the red dots anymore

I also found out the lens I have: 150

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Glad you got it straightened out…

It would be nice for others if you explained how you fixed it. I know I gave a a list.

Have fun :tada:

:smile_cat:

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