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
If that’s the right math, I’ll tag along as I’d love to be able to do it… However, I’d like to see it actually done somewhere, besides your example… Usually if it’s possible somebody is doing it…
We know when you heat glass unevenly, it will crack or shatter because of the stresses of expansion.
The math looks like you are just heating it. Where does the math take into account the stresses involved in the heating of a small area and it’s expansion relative to the nearby unheated glass? Where is it going to expand to before it melts?
With an led, you can’t heat the glass directly, depend on the heat being transferred to the to the glass.
The Study.com site says “The boiling point for silica glass is 2230°C and the melting point is 1710°C”. You should be able to about vaporize it… ?
I can’t even imagine these numbers for heat…
I don’t think the problem is heating it so much as doing so in a way that doesn’t cause it to expand and crack the surrounding ‘cooler’ glass… before it melts.
Just skeptical…
Brings up why can’t I just melt the glass with my co2, instead of shattering it? I can think of lots of lovely artwork that would be neat if I could just melt it instead of shattering it.
Encouraged by the math, I’m looking forward for you to suggest a way for me to apply this to my co2…
Glass obviously has significant thermal expansion properties. Heated area expands, colder stretches. Simple, everybody knows that.
Glass is also elastic, both ways, compressible and stretchable. If tensile strength of main mass of the glass is bigger than compression cause by expansion of heated line - glass will not fracture. If expanding body section is small enough (like really sharp laser line) - it may expand without fracturing. This is obviously very dynamic, not sustainable state as heat flux will tend to spread through the body of the glass. So if such local heating is really small cross-section and really short in time - it is probably possible.
In my burn, glass is tiny fraction of overall glass mass. As long as weight of compression does not overcome tensile strength of the rest of the glass mass - this local melting will be fine without shattering whole glass sheet.
Even with that - that barb wire effect on my pictures is clear indication that some stress is produced at the boundary.
With that understanding, If you like to exercise you creative power over glass, to draw with glass locally liquefied by laser - you may do so on glass preheated to upper annealing point (~350C), where glass is much more elastic than at room temperature and will not shatter from internal thermal stress. I thought that it also need light dissipation media, like black paint, but apparently CO2 laser can hit clear glass without any additional coating, so running laser over heated glass should not be a problem.
Then you need to anneal it properly by cooling slowly.
I’m thinking of flat hot plate. Probably can be fitted over honeycomb of K40 and then controlled to drop temperature slowly. So here is the idea for you: hot plate in you CO2 laser machine.
(Above is purely theoretical thoughts, I have no idea if it is possible for real. I guess somebody need to try and tell us? )
As we talked about quality of included in this machine laser, backup would be nice.
Amazon has price dropped on one that is pretty good fit for this machine. I got couple. It focuses very nicely at max distance (meaning depth of focus is also good), has matching holes and generally very similar in performance to original when brand new, and probably a tad more power.
All it need is pigtail adapter, but this is pretty much for any alternative laser option for this machine.
I run it for a while at 100% and it is cold, not a hint of heating up. Fan is also almost silent.
I’m happy with it as low power backup for JL1 machine.
Just a FYI… I’ve got my original $79 Centoz machine ready to deliver to my friend. The original JL1 controller was successfully flashed to GRBL 1.1f using just a Windows computer and @LsrSal’s original firmware download (w/ updater.exe and ROM.bin). I added a printed Z-lift mechanism and modded it to use a couple of different lasers. I’ve used it in this thread to show its capabilities on a number of different materials and even demonstrated its use with Xtool’s RA2 rotary accessory.
This morning, I unboxed the second of these $79 laser engravers (the one I’ll keep…) and have successfully flashed GRBL 1.1f using the exact same procedure as before. My plan is to replicate my friend’s machine and so far I’m still impressed. I wish it didn’t require any “loving touch”/“sweat equity” to make it really useful but if a person is willing – and a little bit “handy” – it can be a very fun, educational, and satisfying project for not too much $$$.
It’ll be interesting to see how long those 11 machines last out on Amazon…
Laser on listing image appeared different than one I got on my JL1 branded machine that I got for $69 in July. It is specified as 3W .anybody know if this is optical or electrical power?
No laser pointer anymore? On video it is still have pointer, now on the left.
do I need third one those? Why not!?!
David, I encourage you to try my latest firmware with properly working homing. I think at this time it is worth it.
I do not see that. I see " 3000mw". Otherwise : 3000mAx12V = 36W!!! electrical. Then it actually puts it above the range of 3W optical. I don’t think so.
Video in the listing has changed. If that speed is real - it might be 3W optical! Then this would be noticeable bump in the specs.
Maybe David can tell us. Is this the same laser as previous lot? Or I’m messed because I have even earlier JL1.
It appeared to me on the listing images that roller plates and legs now acrylic. My old JL1 is all metal.
Hey, Sal! I didn’t see the listing for the $69 machine back in July… but this new listing appears to be the same one I bought from and began this thread with. That said, the lasers on both my machines are physically smaller than the one shown in the listing… the one shown is bigger-bodied and mounts with the outer holes on the carriage plate. The included laser on both my machines are physically no larger (and no more powerful) than my little 2.3W Banggood laser… and are not as good quality. But I had planned on swapping out the laser anyway… so I didn’t let it bother me. I also just removed the pointer laser and put it in my junkbox as I don’t want or need it. Here’s what both of mine have looked like…
Sal, while I wouldn’t mind using your latest firmware, I don’t have the programming device or knowledge to program it. Though I hate Windows, the original procedure couldn’t be simpler (I’ve successfully used it twice now!) and the JL3 GRBL firmware seems to work just fine for me. I don’t need or use homing anyway, so I just disable it in the GRBL settings.
David,
I got your reasons. No problem.
Just for reference, here is the link to listing I got in July.
Looking at it again - same big laser and I would say that roller plates appeared glossy like acrylic. they are actually anodized aluminum.
It got the same tiny laser like on your image. I took it apart to make pigtail adapter.
I have an idea to try to flash it with original utility but my BIN file. Worst case I can recover with STLink.
Jack can try it too.
Trying your BIN file with the original Windows exe was my first thought as well… and I’d hoped someone would ask specifically if that would work. I was too wimpy though and afraid I’d brick it and wind up in the mess Jack was in at one time… and the original worked “well enough”
I really don’t know if it was operator error or some other issue that cause it to be such a problem.
Others have had it work. I was unaware of the ‘button’ that needed to be pushed, but it seemed to work anyway. Then I couldn’t connect. Didn’t have lightburn on that machine so didn’t try it with the drivers on the Windows box, where I had run the upgrade. That may have been my mistake…
It doesn’t help I don’t know the the controller like I do for other processors.
Lightburn was nice enough to let me have a third license for the wifes laptop that helped make it easier to debug…
Don’t know how well you can see the original module… the Neje is a 30W A40630.
Funny thing: quantity available is increasing! after 5 , one hour ago was 8, now 13!
They playing us!
There is probably shipping contained being unloaded as we speak.
JL2 also went up, from 11 to 18!
Midnight Eastern: 14+19. Still increasing! Fascinating!
)
do I need third one those? Why not!?!
