need a lens or two for the fiber

[Kev Williams]

I keep getting RFQ's for lasering much bigger area's than my current 150x150 lens will handle easily, so I'm looking looking for a lens that will sweep 8"+. The jobs will involve simple marking of anodized aluminum so power density loss isn't a big deal.

In my usual 'let's see what the cheapest I can find will get me' style, I found and F330/220x220 lens for $99 on ebay. That will get me over 8-1/2" of engraving area which I could really use right now. I've had pretty good luck cheaping out at times-- the Triumph is a good example, and while cheap $18 C02 lenses do scratch easily, they seem to work just fine for what I do.

If the new lens works okay, I'm going to give an 80x80 mm lens a go, I'm curious about the power density for deep metal engraving...

I noticed a 400x400 lens for sale, what I couldn't do with that!

[Nick Hale]

I contacted Rayfine about a new lens for me. I need a 200x200 so I can do complete pistol slides. They told me $150 plus $50 shipping. I figured I etch at .02 line distance, I can just drop it down to .01 to help with power loss. But I was curious what other ppl with fiber lasers were using lens wise. Also how did the lenses effect the settings on ezcad?

[Kev Williams]

going to a longer lens will create a larger beam spot, so, and I'm just assuming, I would think you'd want to increase the hatch distance rather than decrease, to more match the actual width of each cut to what you're used to... The main change, as I see it, to compensate for the power loss is simply to slow down the engraving speed. This is my first change so it'll be interesting

[Gary Hair]

You will also find that the focus is more critical on the extents of the max engraving area, if you don't have it spot on at dead center of the working area then you could be way off at the extents.

[John Lifer]

I've only a 20 watt, but bought a 100x100 and a 150x150 lens. I have the 150 on the machine and leave it there for past few months. I saw a perceived difference between the lenses, but I need the area most of the time so I live with it. I would expect that you might can do better with Ray Fine than ebay. I've looked at 175 just to give me a bit more, but not cheap enough. Also Alibaba.... Nick, don't know your power, but if not 30 or better, I'd be just breaking up design.

[Nick Hale]

I'm running a 30w.

[Kev Williams]

You will also find that the focus is more critical on the extents of the max engraving area, if you don't have it spot on at dead center of the working area then you could be way off at the extents.

I had that problem with mine, the lowest 1/4" I tried to avoid because the power noticeably dropped off there. But once I changed my scanhead, the problem went away- after a bit of experimenting I figured out the problem; the beam was running out of mirror! The new scanhead is just different enough, either in mirror geometry or just how it mounts maybe...

I also spent a couple of hours one day aligning the red light so it hit both mirrors dead-center
while running the largest circle path possible:
redmirror2.jpgredmirror1.jpg
I took these pics at slow speed with the aperture shut down, so I could get the full sweep of the led on the mirrors...
You can see the faint dot on mirror one is centered across the mirror's width,
and the full sweep on mirror two is centered both vertically and horizontally.
The 2 pics show the second mirror pretty close to full-tilt left and full-tilt right position, but the 1st mirror is in nearly the same position
in both pics. They don't move all that much!

What I need to figure out how to do now, is to align the laser to match the LED! I haven't actually tried much, just for lack of free time, but if I CAN get the laser lined up pretty close to the LED then that should optimize the focus and maximize the working area. But the way these machines are set up, in actual use you have to align the LED to match the laser. And my laser's beam spot is a good 2mm down and left of the LED beam spot. One of these days I'll break into it and see if there's some shimming I can do to get it closer. It'll be a lot of trial & error, because with a fiber, test firing to tape on the mirrors won't work!

[Gary Hair]

What I need to figure out how to do now, is to align the laser to match the LED! I haven't actually tried much, just for lack of free time, but if I CAN get the laser lined up pretty close to the LED then that should optimize the focus and maximize the working area. But the way these machines are set up, in actual use you have to align the LED to match the laser. And my laser's beam spot is a good 2mm down and left of the LED beam spot. One of these days I'll break into it and see if there's some shimming I can do to get it closer. It'll be a lot of trial & error, because with a fiber, test firing to tape on the mirrors won't work!

You can adjust this in software. I forget where, and I'm not in the office, but it's fairly easy to do.

[Kev Williams]

You can adjust the beam's output shapes and sizes and placement easy enough within the F3 parameters, but I'm pretty sure these are 'dynamic' adjustments done by the mirrors in relation to the beam's 'static' 0 position, and best I can tell, to move the static position requires physically adjusting the 'snout' at it's clamps...

As of now my LED is hitting the mirrors perfectly, and where the LED points and where the beam points on the table isn't even close. In use I'm sure it's close enough as is, but I would like to get the fiber and LED to match up closer, then I'll at least know the fiber beam is hitting all-mirror

[Dave Sheldrake]

I have the 300x300,400x400 and 250x250's Kev, they never get used really, the beam quality at the edges is pretty poor on a 100 watt, surprisingly better on the YAG but still not great, best fix I did make though was changing the alignment lasers for greens, stand out a lot better and a smaller spot size

[Tim Bateson]

I have both 110 & 160 lens on my 50w. I know technically there is a power difference. However, It's so minimal I generally use the same Power/Speed/KHz settings. I swap lens & adjust Work Area, Aspect Parameters & go. For larger areas, I use my Gentry style fiber. Not very efficient, but it works.

[Kev Williams]

My 150 lens, one day I spent a good amount of time mapping my fiber's absolute max working area,
this is a screenshot of the largest rectangle (too large actually) and largest circle I could draw,
with my notes (drawing area is 150x150)...
maxarea.jpg
I get well over 160mm of reach even though this is supposedly a 150 lens-
I did this because I have a couple of jobs where once the part I'm engraving is against the machine, the laser will just ever so barely reach the extreme bottom of the engraving- I use this map to make sure I'm within the machine's boundaries. And I use this map quite a bit, which is why I'm getting a longer lens!

And for what it's worth, deep machining notwithstanding, the engraving quality I get at the extreme edges is no worse than what I get straight down...

[Neville Stewart]

I have the 300x300,400x400 and 250x250's Kev, they never get used really, the beam quality at the edges is pretty poor on a 100 watt, surprisingly better on the YAG but still not great, best fix I did make though was changing the alignment lasers for greens, stand out a lot better and a smaller spot size

Green laser eh! Never thought of that and I even know the green laser on a pistol I have is better in daylight. I always have trouble lining upon really reflective jewelry items. I’ll have to check that out.

[Dave Sheldrake]

532nm is the exact middle of the visible spectrum Nev hence why the eye picks it up so well.

[Floyd Siegal]

This is the method I recommend to our customers who like to change out their F-theta lenses. You have to re-adjust the many F3 settings.

1. Figure out your F-theta lens working area… Divide the lens f # (f=200, 250, 300…) by the square root of 2 (1.414213562373095). For example an f=290 F-theta lens would calculate out to a 205mm x 205mm working area. (290 / 1.414213562373095 = 205mm)
2. Enter this number into your EzCad F3 parameter – Field tab – Aspect – Field size
3. Draw a 205mm square on the EzCad screen and put to origin. Focus and engrave onto a metal plate or photo paper.

Field size.png
4) Now press the double arrow button of Galvo 2 to open up the Calculate scale screen. Enter your desired marking range of 205 and measure the actual marking size (X – Horizontal measurement) that you engraved.Marking size.png
5)Repeat the same steps for Galvo 1
6)Re-mark the plate or photo paper again and measure it. If the actual mark is correct you are done. If it is still not correct then enter in your new actual mark size and keep repeating this procedure until your actual mark matches your desired mark.
7) If your square is not measuring out as a perfect square, use these settings to make slight adjustments to the shape.

Galvo shape.png
8) Click on the Other tab and make adjustments to your red light. Press F1 after you’ve engraved your square and verify the red light is aligning correctly.Red light adj.png
Hope this is helpful!
Floyd / askaphotonics.com