I have a commarker 20w laser been running the 110mm lens works great in focus marks and engraves great, So today I wanted to try the 200mm lens setup the 200mm files just as I did with 110 lens but I not able to mark or engrave with it its like it lost power, Trier different setting from power to speed to freq still not marking on metal so I put the 110mm lens back on and it worked fine again.. Any suggestions would much Appreciated
Rick
It’s likely out of focus… there isn’t anything else to fail or be set wrong, assuming you took off the lens cap. 
So I’d double check it’s focus.
Is this an F200mm lens or an F290mm for a 200x200mm coverage lens?
Depending on the lens, you can appear to loose power.
If you have an F100mm lens, with a spot size of 16uM then switch to an F245mm the spot size is 31uM or about twice the size…
If the spot size is doubled, then it’s power is distributed over 4 times the area, so it would appear to be 1/4 of the power. Same power over different size area.
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Thank you so much you was right out of focus, I when back out to the shop and messed with didn’t realize that it had to go that high up to focus but got it up and working.
Thanks again
Rick
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yep. the energy density at best focus goes down to 30.25% of the 110x110 lens, and focus needs to go up 133mm.
i have the two converging red dot pointers for setting focus. they’re useless when adjusted for another lens. and too much work to readjust for a lens change and then adjust back later
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Unless you have a single lens, these are useless. It’s a pia to adjust, with a lens change.
I have a switch on the focus leds, I’ve had mine turned off not long after I received it.
I use a measuring stick and sound to ensure focus.
I wouldn’t mind adding an autofocus rangefinder. I know the autofocus machines use some form of one.
What puzzles me is how wide the rangefinder’s spot will be. If I’m trying to range to a small coin in a jig, and the rangefinder’s probably invisible IR. If part of the rangefinder spot hits the jig at a different height that the coin, it will not be accurate.
And, how does this work, really? See, the rangefinder is going to have to be mounted off-axis, right? It can’t physically be in the center of the lens, the beam would hit it. It’s mounted on the side of the head, let’s say we put it on the right and angled it so it hits the center at 163mm for an F163 110x110 lens. But that mean when it’s below the correct Z, the rangefinder spot is going to miss the jig and hit a a spot further to the right. When Z is too high, it hits something to the left.
And when I change the lens, the rangefinder’s not going to automatically change its angle. If I put in a longer focal length lens, the rangefinder spot hits something to the left, even when at the correct focal height that beam will be hitting to the left
All of these I’ve seen measure perpendicular to the bed.
And I think this means you’re measuring the hypotenuse, not the vertical distance. Those that are not mechanical use use electronics modules like LIDAR, used in the P2. Lidar depends on reflection off the material.
What might work well for a co2, likely won’t work well with a fiber. At least how I use them. most of it is relatively small areas <200x200mm.
Just a thought.
That wouldn’t work for most things I do personally. The work will be directly under the laser head, often small. A rangefinder on the side of the head pointing straight down will probably miss the stock.
I could move the jig under the rangefinder then move it back and bolt it down again, but that seems like a net loss for convenience over finding the focus in-place
Where I want it to measure is at the depth of the engraving, not the surface… moving Z down as the engraving proceeded. So even using this technology, there is no way to measure such small areas.