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May 02, 2018, 04:33 PM
Registered User
ccpdx's Avatar
Discussion

Diode laser cutter for foamboard


I bought a 15w 100cm x 100cm ebay laser engraver / laser cutter in the hopes of cutting as much as 1/8" plywood and DTFB / Adams Readi-Board.

It's exceeded my minimum expectation for plywood, but not so much for the foam board...

Based on various videos and online postings I saw before I bought it, I THOUGHT the problem I would have to dial in is how to cut the foam board delicately enough without causing the foam to shrink away too much from the cut line. But that's not the problem I'm having at all! The real problem is that violet light refracts and spreads out rather than cutting the foam. Go too slowly and it's easy to catch it on fire (on the bottom side).

Does anybody know of a good TTL laser module that will actually cut through foam board? Will 808nm 500mw work? I'm a little wary of going towards IR, especially with an open frame setup. But if it would actually WORK, it might be worth a try, being careful about safety.

Otherwise I've been figuring out what else I can do:
So far I've figured out how to export drawings from Inkscape in g-code that (crucially) the engraving software is happy with. There was a g-code "fixing" utility that it came with, but that crashed each time (at least the version that I tried.) The solution was an Inkscape plug-in by a different brand of laser engraver. Anyway, in about 15 passes at 400mm / min I can cut through some 5mm or so dense scrap plywood I had laying around. It could probably go deeper. I'm new to this and still experimenting in the little time I get to play with it.

Charles
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May 02, 2018, 09:17 PM
Retired CAD guy
birdofplay's Avatar
You are where I am at.

But I only have a 5.5W and it won't cut white foam at all !!!

So I will be watching what the discussion is here as well.
May 02, 2018, 11:19 PM
Registered User
ccpdx's Avatar
Thanks for responding. I've read a number of your posts before, but I was mis remembering. I had it in my mind that you did a lot of laser foam board cutting, but as I discovered earlier today, it's actually milling that you've mostly done....

So far I've chased the initial cut with a fine tipped Sharpie with the idea of giving the laser a target to hit. I need to try that again, but so far it doesn't look super promising. I do end up doing a lot of "cutting" with she Sharpie tip by the way.

I've also thought about using a syringe to wick black ink into the channel left by the laser. I haven't tried that yet, and I don't know how well that'll go where I want versus into the paper. It doesn't seem that promising anyway.

Worst case I at least have an easy way to make templates, or not even have to use templates. I'll probably peeling one side of the DTFB and laser cutting the remaining paper, and chasing it with a hobby knife, but that's the part I was hoping to avoid.

Charles
May 03, 2018, 04:18 AM
Registered User
From a quick search on line, your problem is that white just reflects most light too much.

Quote:
Mostly Harmless
New member
Sep 6, 2016
#7
AkimboGlueGuns said:
The white paper reflects a lot of light ....
This is true at visible wavelengths. However, at the wavelength that CO2 lasers operate (in the mid-IR range, or about 10.6 microns), pretty much every material (non-metallic) appears "black." White foamboard -- and even clear plexiglass are only appear that way in the visible spectrum our eyes detect. In the mid IR, they will absorb just as much of the laser's power as the darker foamboard.
So it looks like an IR laser is what you may need, from reading you will still get the foam retreating from the paper at the edges, but aslong as you dial down the power low enough its not enough to cause problems. FT speed build kits come like this
May 03, 2018, 09:55 AM
Registered User
ccpdx's Avatar
Unfortunately before my purchase I saw so much online about the foam shrinking away from the cut line that I missed the bit about not working in the shorter wavelengths. I know that now....

Your reference is from here:
https://forum.flitetest.com/index.ph...m-board.29698/

Here's one of the videos that gave me the impression that would be no problem with the diode laser I purchased. The machine actually looks similar to mine, even the laser color, but at a smaller scale and power. He cuts some kind of light colored foam board. Now I wonder what kind of foam board he has.:
DIY LASER CUTTER/ENGRAVING MACHINE KIT (4 min 0 sec)


Maybe he's cutting something like the Office Depot foam board as described here (but that's a lot more expensive than DTFB):
https://jtechphotonics.com/?p=918


Another one of the videos that stuck in my memory (yes this one looks like a CO2 laser):
Laser Cutting 1/4" Foam Core (0 min 35 sec)


I haven't been able to find any cheaply priced 10.6 micron diode lasers. Here are some expensive ones, and that's just the unmounted diode:
https://www.thorlabs.com/newgrouppag...tgroup_id=4737 https://www.thorlabs.com/thorproduct...ber=L1060P200J

It's easy to find 808nm lasers on ebay for really cheap ($21usd, plus twice that price for the safety glasses). For more money, 980nm lasers can be found there as well. I'm going to go ahead and see what 808nm can do. Note: I plan to avoid looking at the cutting area directly while it's cutting. I have the laser head and mounting components to obscure the view, plus safety glasses.

Charles
May 03, 2018, 11:47 AM
Registered User
ccpdx's Avatar
This guy says he turned a green diode laser into an IR laser by removing a part. Interesting if true. It begs the question, if this is so easy to do, why are 10.6 micron IR lasers so expensive?

From his description:
"... the wavelength changes from 532nm (green) to 1064 nm (Infra Red) after the removal of the frequency doubling potassium titanyl phosphate crystal ..."

Homemade infrared laser engraver (3 min 0 sec)
Last edited by ccpdx; May 03, 2018 at 11:54 AM.
May 03, 2018, 05:49 PM
Ken's CAD Models
dz1sfb's Avatar
I wonder how it would do on straight foam. No paper covering. You could run at lower power and not get as much burn away.

Ken
Latest blog entry: Mini H Quad Project
May 03, 2018, 07:15 PM
Retired CAD guy
birdofplay's Avatar
A lot of these Cheap Diode laser are NOT well colimated
which kida flys in face of what a LASER is supposed to be.

Then add to that the insult of a Lens for focusing and it's barely a laser beam any longer.

I cut several plane kits from the Old Black/grey depron.

However, Black./grey depron was ALWAYS 2nd rate
as it came with many flaws. Blisters, Open gaps and smears.

Pink ~1/4" insulation foam with no backing or paper was cuttable but NOT quickly.
I.E. multiple passes and green foam form Lowes was similar.

Poor diode beam, Lowered avg cutting speeds and additional prep and handling work just
has me throwing in the towel.

But I am still hopeful and lurking ;>}

Bob @ Hoosier Cutout Service

ps

Jtec has good driver but their diode are still all blue.

Thors' web page is very slow and jerky no joy there
alibaba has nothing I can find at this time
Last edited by birdofplay; May 03, 2018 at 08:30 PM.
May 03, 2018, 10:19 PM
Registered User
ccpdx's Avatar
Ken, the paper is actually the easy part. It's easy to get a clean cut. On white paper, it's possible for the laser to skip spots if you go too fast. It's kind of like it needs to keep the blackening of the burnt line "primed." But the solution to that is easy. Go slower and/or do multiple passes. Or maybe just go for higher beam density with the focus or height adjustment. Getting the foam to absorb the light, that's being the hard part.


Bob, you cut a lot. What kind of cutting speed are you used to running at? In the end I do have the option of adding a third axis.

Meanwhile I'm waiting for that 808nm diode.

Charles
May 04, 2018, 03:42 AM
Registered User
Theres an instructs le on how to build a lazier cutter that does both wood and foamboard however it is priceu 1900 euros. Still not as pricey as a commercial unit
May 04, 2018, 11:14 AM
Registered User
ccpdx's Avatar
Do you have a link?


I'm looking more seriously at the possibility of adding a z-axis and making a needle cutter: https://www.rcgroups.com/forums/show...ighlight=mpcnc I'd read about it before, but kind of forgot about it because I didn't realize at the time what a big problem it solves for would-be diode laser users. If I do it, I might cut mine out of plywood though because I don't have a 3d printer

Meanwhile my searches have found more people asking about 808nm lasers, one person even demonstrating it "drilling" into pink foam, and claiming it doesn't cut on white, but otherwise not a lot of "I tried this and it failed, see here's what it looked like." I'm still going to try it, see if it does any better at all compared to the blue/violet light and post the results.

The real issue for me is that this whole thing is a distraction from what's supposed to be my main project in my very limited time before a vacation this summer: DESIGNING AND MAKING AN AIRPLANE!
May 05, 2018, 08:46 AM
Retired CAD guy
birdofplay's Avatar
I typically cut at ~ .5 ips and 1.5 ips wiht router speed~ 10K

The Needle cutter is a terrific idea.
My attempts left 1. very low width kerf and 2. surprisingly smooth edges.
However , it required a slower cutting speed because the higher forward speeds
required higher plunge rate and it just WORE OUT or Flew apart.
The thread chronicles several of my experiments at increasing cutting speed.
If you are NOT in a hurry Needled cutting is a Great way to go and VERY inexpensive.

I have several ideas for making an IMPROVED needle cutter
but LIFE gets in the way and I don't HAVE to have it.

I did get a 3d Printer since the Needle cutter experiments.
However, a 3dPrinter is one serious TIME SINK for many many reasons.
Last edited by birdofplay; May 05, 2018 at 08:54 AM.
May 05, 2018, 09:42 AM
Registered User
Lawn Dart Flyer's Avatar
Here is a very extensive thread on needle cutting if you want to go that avenue. https://forum.flitetest.com/index.ph...-needle.24251/
May 12, 2018, 12:38 AM
Registered User
ccpdx's Avatar

808nm laser arrived - no luck with TTL so far


The $21 808nm laser arrived. I've had no luck getting it to go yet though. As far as I can tell it's not turning on.

There are four connections on the driver board. All of them use the same JST-XH 2-pin male connector:
1) Incoming power, 12v and apparently AC is OK as well as DC.
2) Outgoing power to the fan.
3) Outgoing power to the laser diode.
4) And TTL.

The TTL connector is the only one that came without something plugged into it. From online listing photos, I can see which side has the red wire but I don't fully trust that those photos are correct. And so far I haven't found any other reference. So I made my best two guesses and made a harness.

Charles
Last edited by ccpdx; May 12, 2018 at 12:46 AM.


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