Focus distance of the laser


#1

I know the focal length of the laser is 1/2 inch for best cutting scenario. But when the warranty is up, and i decide to remove the bottom of the case, will it I be able to set it on a larger piece of material and etch on it? IE wood or glass or acrylic? I am wanting to use it to make designs and personalize custom furniture.


#2

No one knows how easy the bottom will be to modify. Other than that… If you get the top of the material within that 1/2" focus, then sure. Same is true when you remove the tray on the basic model. The top of the material needs to be in the same 1/2" focus as if the tray was still installed.


#3

So essentially anything past 1/2" away from laser will not be able to be etched or cut? I was hoping 1/2" was optimal but you would still be able to etch at a longer distance. Not a huge deal was just trying to decide best way to use my glowforge. Thanks for the help!


#4

I guessing if you were to remove the bottom you would have to have some kind of heigh adjustment mechanism to move the material up and down to get it to the 1/2" range. Its fully possible (I mean I don’t know if there bottom can even be removed)

@elsman18 what kind of furniture are you thinking of?


#5

That’s what is advertised. Anything beyond that has a defocused spot. Power drops off very, very fast. Also need to point out that it is not necessarily 1/2" below the laser head, but within a specific fixed factory set focus range.


#6

This next statement is pure speculation.

Since the glowforge as ‘active optics’ (as in you can software control the focus)
There maybe a possibility that it may go beyond the 1.5" (Now, I don’t know if the 1.5" is a mechanical max for the optics or some other safety buffer)

Since none of us (aside from the GF staff) have no idea what the chassis assembly looks like.
It’s hard to armchair quarterback what is or is not possible. i.e. Me designing a rotary axis. I can only guess and speculate what the gantry position is. I maybe wasting my time doing so?

But hey, It’s fun talking about possible addons, hacks and mods.


#7

Coat racks, headboards, hope chests…stuff like that. Thought it would be nicer to use the glowforge to personalize them with more of a custom one off look instead of router and guides.


#8

Cutting is about power density. The 1/2" focal adjustment range means there is a 1/2" space in which you can be at THE focal point. Many things can cut at considerably less than full power minimal speed. So you would still be able to cut them outside of the focal range, but would need to increase the power, decrease the speed, and suffer a much larger kerf.

The beam doesn’t spread too quickly after the focal point either. My 60W tube was able to burn a hole in a 2x4 at four feet with no issue (zero lensing between tube and target). I was curious about post-focal beam dispersion, so we removed our cutting surface and let the laser fire through the focal lens (75mm focus) at the ground about 3 feet down. It did not burn to immediate flame like the non-lensed beam, but it very quickly charred the wood, with a spot size about the same as the non-lensed beam.

So, still quite possible to effect things beyond the focus range. But it will work differently than you are accustomed to. In some cases that is an amazing new capability, in other cases it is a limitation.

Having lived with a laser which has no enclosure for a few months now, I will say that you should think very carefully before you break open the case on your Glowforge. If you absolutely must play with larger objects, consider buying a cheap chinese laser system to play around with instead. The primary complaint about those is the frustration in figuring out how to use them (and the interface, which really is the same issue IMO). With the experience and understanding from using the GlowForge, you can be more capable with the cheap-O-matic laser. And of course you only have to deal with that annoying laser system for those few projects the forge cannot handle for some reason.


#9

I think for the Epilog laser, you can purchase a different set of lens that changes the focal length of the laser. This may be an option for modifying your GF to cut a different depths.


#10

sounds cool. Looking forward to seeing what you do. You can also “trick” the software and use magnets to activate the door latch. I think you’ll be able to engrave the ends of longer material this way.


#11

Thanks everyone for your help, I might go ahead and order the cheap unit and go that route if the glowforge is hard to remove the bottom on. Wanting a routed out look more than anything, with fancier fonts then my arrangement of forms allow. Larger kerf in that instance wouldn’t be a huge deal but I have plenty of time to figure everything out. Thanks again for everyone’s help


#12

Hmm. My experience (mostly with a 25W Universal) is that outside the focal length it burns a much wider swath. You can turn up the power but you can’t get precise cuts. Mostly I know this because have, on occasion, failed to properly focus.

Also, on the Universal the bottom of a deep cut is wider than the top so that what should be a straight cut is actually a little undercut. Perhaps there’s something about the Universal lens that does this…


#13

I’ve been thinking about the “active optics.” This should mean that you can etch a flat piece that’s not lying flat. The affect of this would be (I think) that when you look at the result straight on, the holes have a direction to them.

That is, if you take a piece of wood and prop one edge up a bit (less than 1/2 an inch, presumably) and then etch it, the laser will focus correctly across the entire piece. But when you look at it straight on, all the cuts will be on an angle from the side. So in the proper lighting you would get shadows where you wouldn’t with a traditional laser cut.

I have only the vaguest idea about what one might do with this but i think it’s an interesting idea.


#14

Yes, that is what you should see, and what I am trying to describe. But the beam doesn’t spread nearly as fast as I had assumed it would. I thought it would be back to non-lens width and power once you had reached double the focal distance, and after that quickly expand so much as to be harmless.

But at well over 6 times the focal distance, I was still getting a concentration of power on a relatively narrow area, with enough power to be immediately apparent that damage was being done to wood.


#15

Some folks were talking about doing this to simulate a beveled edge in this thread.


#16

That’s similar but they’re making cuts and I’m etching the whole piece with an image that, I hope, will look different in different lighting.

You can actually bevel edges with a normal laser (the piece is the same height all along the cut so you don’t need active focusing).

Thanks for the link; I’ll go see if they have solved the Big Problem with bevel cuts.


#17

Some tidbits for would-be modders…

Beam width is about 5mm. The focal length of the lens is 50mm. 0.5" is the distance it can move. You can do some math and figure out how fast it diverges once it’s out of range.

If you remove structure from your Glowforge, it loses strength. This can have dire repercussions in repeat-ability and accuracy, not to mention safety.


What the kerf?!
Photons per sec at 100 percent power
#18

Thanks for the warning - the plastic enclosure is not just a passive ‘shell’ but a critical part of the structure.


#19

Interesting. So the glowforge chassis is a unibody. Not a structure with a shell?


#20

Probably a hybrid …~80% rigidity achieved with the inner chassis, ~20% from the enclosure (making those numbers up).

So if you’re hell-bent on cutting open the bottom, the whole system will need to be fixed to another equally rigid ‘structure’ to make up for the loss of the integrity from cutting open the bottom… and yes, there would be that safety issue that needs to be addressed.