Fiber laser spot size from 4w qswitch to 100w mopa

Community Laser Talk
1

Just sanity checking.

Trying to engrave coated cards on my new 100w JPT mopa. I could achieve 0.06 spot size on 4w qswitch raycus (175mm lens) but only 0.09 on 100w MOPA (200mm lens) i recently bought.

I believe i do have focus right (by spark/noise test), but all card results are way blown out and lacking any detail. I do tweak alpha/brightness, etc, but i get very chunky dots on same cards i ran on 4w raycus. Interval tests suggest scanline overlap of 0.09.

I’m pretty sure it may have to do more with pulse/frequency than power.

Anyone here run black coated cards (not anodised) on 60/100w mopa ? Could you share your settings for photo engraving on those ? No matter what i tried i cant get the detail of 4w raycus on 100w mopa….. help…

Pic: Left (100w JPT mopa 1500spd, 25%pwr, 80frq, 200q, 0.0852lpi), right M-Triangel PG-OneS (4w raycus qswitch, 1000spd, 95%pwr, 20frq, 0.05lpi)

image
image1201×901 361 KB

2

Have you got your timing settings dialed in? I’d also try speeding it up significantly to around 4000mm/s, and lowering the q pulse, then hunting for settings round there. I think the current settings are significantly ablating the surface, you may be able to tell by touch that it feels rougher/deeper.

3

Yeah, timing’s the next thing i will be dialling in.

I was wondering if timing scaled with different speeds as it does for gantry lasers.
If, say, i dial in for 4000mmps, will it be way off at 300mmps.

4

This question has been discussed extensively here on the forum, but I haven’t reached a final conclusion about the possible benefits.

You can find the posts with the keywords “Galvo Overscan.”
Careful, it’s quite the rabbit hole! :slight_smile:

I can still recommend MakrTheory’s video for Timing Calibration for the “easy mode”.

5

Yep, that’s exactly the video i’ll be following today (watched it couple of days ago). Already got the files. I was just wondering if the timing scales as aggressively on galvo as it does on gantry, considering very wide range of speeds used on galvos (from 100s to 1000s). On gantry you have to effectively recalibrate for every 50-100mmps or so, if i remember correctly. That’d be insane for fiber range.

6

It does seem plausible to me that it makes a difference.
Certainly not as much as with a heavy gantry, though. That’s where the physics really starts to matter.

I rather think that, with fiber sources, we are adjusting a constant: how long it takes for the laser source to actually fire after a pulse is commanded.

And how quickly the galvo mirrors get up to speed. (Yes, different speeds certainly have an influence here, but the mirrors are enormously lighter than a gantry.)

7

Spot size is the same computations for a fiber/co2/led or any other laser that uses this medium, in that the lens determines this.

depth-of-focus
depth-of-focus1281×720 82.7 KB

There are multiple calculators on the Internet you can use to get an idea of where you spot size should be.

What will change is beam diameter at lens and the beam quality, along with the frequency, usually in meters. Frequency is already determined for most fiber machines.

This uses the 8mm beam diameter that JPT states is the output of my fiber, if I remember correctly, but it can vary as the sources change. The other is beam quality, or how well it fits with the Gaussian power curve.

image
image602×468 41.8 KB

The spot size is 60.2 microns (0.0602mm) with an F254mm lens, and with an F100mm it’s about 593 microns or basically 600 microns.

image
image602×468 41.5 KB

Keep in mind if you cut the spot size diameter in half, the area is reduced 4 times, so it appears 4 times more powerful. It’s the same watts in less area.

You can find the source manuals, it should give you beam size and quality values for both sources.

Have fun.

:grinning_cat: