I’m enjoying it, for real. If I would blow that money on one machine - would not be fun. And then I went way farther than really needed. But I’m in control of it.
And I’m trying to help others to save.
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Supply and demand!
I thought folks will be curious to see:
First time I’ve tried glass with generic flat black spray paint.
I did not expect that!
This is 4W optical at full power and 400mm/min.
Raster is 20 lines/mm.
Vector pass is just melted/fused glass at much wider area than spot width is. I guess it is way above glass transition temperature and heat spill wider. It has swirls like good metal welding.
The raster is also interesting: source has smooth gradient. Glass appeared to have two tone (though not far apart) + melted at the most saturated spots.
Apparently it does not takes a lot of power to engrave glass!
As Dave saying: " this should be good for something…".
(on the image paint is not removed yet)
I’ve never worked with glass. Does engraving like this leave the glass more vulnerable to shattering? How does tempered vs non-tempered glass factor in?
I though you have one?!? What did you flash with my firmware then? Or you want to buy second one?
Right now there is nothing else even close to that price range.
The good news is that Ali still have some similar stuff, but it is always a risk to buy from there.
Or we can try to put BOM together from components that still available on Amazon. Original laser is to be replaced anyway. With that - It might be possible to put similar machine together for about the same amount.
- Profiles $20
- Rollers $10
- Plates $15
- Chains $10 (optional)
- Timing belts and pulleys $10
- MIsc hardware $15 (screws, wires)
- Controller board $15-$30 (can be made for $10: Blue Pill, 4988x2, Proto board)
Well, still pushing $100. Maybe $138 is not a horrible price for such kit with starter laser?
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Need to quantify:
Qualitatively - yes, this introduces non-uniformity and stress that will weaken the glass. Practically - this is still extremely thin layer, weight in overall strength is negligible. Added stress, if any, will dissipate over time as glass is amorphous.
Practically - I think this is perfectly safe for any application.
Thanks. I was curious as my experience with glass outside of lasers is that even slight micro scratches can create stress points that lead to unexpected breakage. Typically when stressed from thermal expansion/contraction. Of course I was working with some very cheap glass at that time…
I guess I should have posted this earlier… now that we’re into engraving glass. From some previous work I’d done, you can get a different effect on glass simply with the paint you choose to coat the glass with before lasering… flat-white paint (with high TiO2 content) gives BLACK marking while dark paint/backing gives a “frosted”/ablated marking (note the lizards…).
Earlier today in post #259 I shared a portrait using flat-white paint on transparent glass
So, later I did a "frosted’ image using just a dark backing (tempera paint or matt-black works as well) to ablate the image on transparent glass… same 2.3W laser, same speed/power settings as for ceramic, resized image to fit scrap piece of glass. Here I’ve simply placed the glass on a clean piece of cereal-box cardboard (chipboard) and lasered through the glass with a negative image, focused on the chipboard surface…
Glass and backing separated to show lasered images on both…
Glass simply washed in dish water to remove soot and edge-lighted…
Contrasting the two images on appropriate background…
Using the two laser processes together and with careful registration… you can do two-“color” engravings…
Fun stuff!
– David
David,
I’m doing exactly that, inspired by your reports of dual color glass engraving. Not like I need it but it is fun stuff never the less.
I got sample of glass painted half flat white (Starbucks anyone 
) Rustoleum and the other half - flat black nitro paint.
After paint removed here is more interesting stuff:
My gray scale raster was all in the paint, most washed off without a trace. Only melted glass stayed. With that I see faults.That stuff that looks like barbs. These are faults. Dithered it would look like frosted. Black paint easily removed. Now I’m really wondering if these fault may grow. This maybe specific to the glass I have.
Also noted that raster filling where glass melted - there is no faults, only uneven swirls of molten glass\ (also frosted glass effect).
White paint is different. I see black globules. Some barely sticking and some are completely fused with glass, impossible to remove. I guess this is magically converted to ore kind of physical form TiO2. But because of spherical shape - I doubt it is crystalline. Probably also amorphous, just like a glass.
I did not optimize anything. This is first shot. It is probably possible to improve desired effect by dialing power/exposure.
But I can confirm: Black paint - bright haze. White paint- darker shadow.
Sal,
I don’t have a microscope (that I can find after my last move) but I know that the end effect of using the different paints is different… white paint leaves a slightly-raised dark image and the dark paint leaves an slightly_recessed image.
It doesn’t take much laser power at all to “engrave” glass. I do a NWT test grid to determine “best black” for the flat-white process… finding the optimal speed/power can be really hit-or-miss without it.
The flat-black process is far more forgiving… a broad range of speed/power will ablate the glass…
That said, I don’'t do grayscale on glass… only dithered images. Also, you have a more powerful 4W laser and are running 400 mm/min and 100% IIRC… I’m using 2.3W and running 1000 mm/min and 100% to get the effects I’m getting.
Not real scientific… but using my mind’s “microscope”, I’m picturing small chips of glass being popped out under each constant-power “dot/dash” of a dithered image. With grayscale, I’m picturing a “river bed” of more-or-less “molten” glass that results in boulders and voids (stress risers?) as the power varies.
That said, using a NWT test tile with flat-white paint like the one above, done for my 2.3W laser… it appears you could possibly get a reasonable grayscale image at 1250 mm/min?
– David
IMHO, working with glass a lot, I don’t think you can ‘melt’ a small area…
My co2 has substantially more power than an led and it only shatters the glass. You would have to raise the temperature of the TiO2 to that of molten glass and it to transfer the heat to the glass to accomplish melting the glass. I think it would shatter long before there was enough heat to melt the glass.
I’ve never seen any application with a laser that could ‘melt’ glass… it always shatters…
I think you’re seeing something else here, maybe a product of the coating you’re using… ?
It would be nice to be able to melt it instead of shatter it… a totally different result.
@LsrSal Yes I have one, running your firmware… I thought… This is the site/machine I purchased for $79, Amazon has tracking on what I purchased …
Even with the headaches of getting it to work, it’s still a good deal. Drug out the old 30 watt Neje that’s mounted on it now… Having a good time with it…
The boss told me I could order another one… I’d like to for $79, but not real hot on the $140…
I really like the idea of someone (other than me… I have concentration/malaise issues 
) putting together a BOM for a “near-clone” of this machine. I took the “risk” of buying this machine in the first place… thinking the parts alone “must” be worth the $79 asking price, even if it was otherwise junk. It wasn’t junk however… but a pleasant surprise, once a few “love taps” were applied.
But with the lack of availability now many are missing out. I think we now know what we’d like to see in a little machine like this… better laser, GRBL controller, LB-compatibility, simple Z-adjust, etc. Could we make this “near-clone” into the perfect little starter/dedicated machine?
– David
forgive my ignorance, but Is this not a GRBL controller with the lsrsal reprogramming?
Mine got bricked when I tried to load the original ‘upgrade’ from the vendor. I was never, to my knowledge, able to load it and make it work. If I knew it’s starting address that might help as I can write new flash to it without the usb port.
@LsrSal sent me a re-compiled version for the machine that I’ve been using.
Haven’t tried to home it, and when I stop a job, the controller goes out to ‘la-la land’ and I have to reset the usb port and controller…
I just appreciate how it’s working now, compared to a paperweight, so I appreciate @LsrSal work to get this working as well as it does. If you don’t interrupt it it seems to work fine.
I assume you used the upgrade program on yours or ?
It is a Grbl controller now… but it didn’t come that way. However, if we’re building/buying/specifying a “new”/near-clone machine, we’d want Grbl-control included up-front rather than the crappy firmware this machine came with. – David
Jack and Dave,
I’m very confident that what I see is locally melted glass.
I did not expect this result either. Just like Dave explained his expectation, I thought little chips flying or evaporating from laser hit and creating something more like sand blasted surface.
This is the exiting part that micro reality is different to common understanding and expectations and even what our eyes can see!
There is also a probability that different balance of power/spot size/dwell time/glass type/paint type/etc… can create very different results. But I absolutely did not expect to see what I see.
Better understanding of physics may yield better results. This is my fun.
For example, that black conversion of TiO2, looks to me like amorphous phase of it:
" Amorphous TiO2 thin films can be deposited at temperatures as low as 100*–150°*C"
So here we go, controlling temperature may yield better black. While counter intuitive - fuzzier focus may yield better uniformity of temperature and resulting better black. I recall in original Dave’s experiments, picture with tooo much power, where dots are black only on periphery of the spot. This correlates!
I would love Dave to look at his work under microscope. I understand he lost his. So I’ve pulled another Chinese Gem - USB Microscope, just to check what i can see with it. I pay $20 on eBay for it. While no stereo Nikon - it is quite potent tool.
Below a few more images to prove my point that glass is actually locally melted. It is obvious to me in stereo. Melted glass shine is consistent with liquid phase of glass, and rough spots where probably some paint inclusions caused melted glass surface tension and resulting bumps after cooling.
I’ve also tried clear glass - nothing noticeable on the glass. White paint - results are very similar to black, only addition of black inclusions.
Here is my representation of what happened, cross section, then couple images, one through good microscope and another through $20 USB one.
USB Microscope with its own light:
and with additional illumination (LED flash light):
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Way over my head… but appreciated!
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Glass melts at around 1500 C (2600 F) or about the same temperature TiO2 vaporizes. That’s also about 10 times the heat you need for the TiO2 reaction, if your post is correct.
I know of no way to heat a small part of a glass object and reach a temperature high enough to melt it, without the stress fracturing occuring. It has to reach melting temperature to melt, the surrounding glass won’t take that type of temperature differential.
Even Pyrex glass shatters when lased, it’s the heat and it’s not even near it’s melting point.
If it’s an led, you are not even ‘lasing’ the glass with an led, you are depending on the TiO2 to transfer the heat for indirect application to the material.
The numbers with the temperatures and how they are applied along with working with glass a lot, suggest to me you’re looking at something else that appear to you as melted glass. I would be doing this if possible.
If you could make this work I think there would be many industrial applications for connecting glass.
I don’t know of any industrial applications that use a co2/led type laser to do anything to glass but cause small fractures for engraving. They are not used for cutting, as would be possible if you could melt it without it fracturing… The majority of the engraved glass I’ve seen comes from diamond tip tooled milling type machines.
I do think you are inline to adjust the power, how you would do that ? Even measuring it would be tough nut.
Just don’t want you to make an assumption that may not be valid…
Jack,
I challenge you!
Let’s do some math, or physics, or whatever it called… If anybody find defect in my calculations - please comment.
Let calculate if there is enough energy to raise glass temperature to melting point. If it is close - we will throw some corrections. If it is much larger - will assume it is possible to melt the glass with laser diode.
Glass specific heat: 800 J/kg°C
Glass density: 2500 kg per m3
My laser optical power: 4W
Speed in this experiment: 400mm/min
glass melting point: 1.5K°C
my laser spot is about 0.1mmx0.1mm (larger spot will give longer dwell time, so more energy. this is conservative). Per my measurement - melted trace is 0.3mm so most of the beam is integrated.
I assume conservatively that heat spill symmetrically, therefore length is also 0.3mm and volume of the spot is 0.3x0.3x0.15mm deep.
Also assumption is that glass is very poor heat conductor and in 15mSec heat does not flow far, pretty much most heat staying in the spot.
spot glass volume: 0.3mmx0.3mmx0.15mm = 0.0135 mm3
spot mass: 2500 kg per m3 x 0.0135 mm3 = 2.5ug/mm3 * 0.0135 mm3 = 3.375e-8 kg
heat capacity of spot volume = 3.375e-8 kg * 800 J/kg°C = 27uJ per °C
laser spot dwell time = speed/spot length = 0.1/(400/60) = 15mSec
total energy absorbed by the spot : 4W*15mSec = 60mJ
temperature rise = 60mJ/27uJ per C = 2,222°C (we are in the ballpark!)
Add coefficient for absorption/reflectivity/heat flux into surrounding glass. Still, that 1,5K°C melting point is achievable.
After calculation I’m even more certain in what I see.