Fire Safety

this is kinda being talked about in another thread, but in the situation where the material on the bed is starting to catch on fire (or is on fire), if the lid is raised to try and snuff out that fire before it gets too large, wouldn’t the head and gantry of the laser be in the way of putting out that fire? If the head doesn’t move out of the way when the lid is opened, there is a potential that the GF itself would be preventing the fire from being put out and causing more harm to the laser head.

Correct. That’s why we want the head to quickly return to 0,0 on lid-opening. I infer the “yet” to mean “Tom, that’s a great idea. Wish we’d thought of that. We’re going to try and do that but it definitely won’t work that way at launch. If possible, by Q4, 2017.”

To put it in terms @dan 's turtles would undertand:
PU
SETPOS [0 0]

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I’m not sure I want the head automatically moving as soon as I open the lid. It sounds useful for some situations, but for others it could cause crunching.

Willing to go with the clearance between the lens and the material to get in there in case of fire. (Hmm, do we know just what that clearance is?)

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@paulw, can you define what the term “crunching” means?

As far as the clearance is concerned, I think it is a 1/2 inch focal range. So that means that the material should be within 1/2 inch from the tip where the laser leaves the head.

open lid > open front flap > yank honeycomb with materials and fire out of Glowforge > look around desperately for metal trash can > drop on floor

(note: I have a concrete floor.)

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By “crunching” I mean that something tries to occupy the same space as the head/gantry as it’s moving. Might be a piece of wood/plastic/whatever that’s warped upward while being cut. Might be somebody’s hand or face. Either would be bad, which is why I think an auto-to-zero could cause trouble.

Meanwhile, I see from this thread that the focal length of the final lens is 50mm, or about 2". Which means that even with head and window there should be more than an inch of clearance, probably more like 1-1/2". Which makes me feel better about reaching in/under.

2" is the height of the material that can fit in the GF. I’m pretty sure the “cutting area” (focal length) is only .5"

I’ll have to look to find where Dan talked about it.

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I think I found something that will work.

@rpegg responded to someone with this explanation:

There is some distance above the 1/2" focus range before you interfere
with the laser head. Not sure how high but the focal length of the
lens is 50mm (~2"). Normally that would mean that the focus point is
2" below the lens which would be near the bottom of the head, but with
the variable focus I’m not sure how that translates. I’m guessing about
an inch by the videos we’ve seen.

and @dan responded to him with this:

I was going to answer here but @rpegg is absolutely correct. I don’t know the clearance offhand either.

These are both in the discussion of “How low can the GF cut/engrave”

looks like we are potentially talking about two different things, focal length vs focal range. my .5" was referring to the focal range (distance from lens for ideal cutting and engraving of a piece) where your 2" was potentially referring to focal length (distance from the lens to the bottom of the enclosure)

your material can be up to 2" thick, but the surface to be cut/engraved needs to be within the .5" focal range of the laser head.

I wish it didn’t cancel the print. For the Epilog, I thought that it just shut down the laser. The laser head just keeps moving. Opening the lid to temporarily shut off the laser is a good way to deal with small flare-ups. If you open the lid and it cancels the print, you could lose a lot of time and material. This would be a big deal on a large print.

I guess we’ll find out in the manual how to deal with minor flare-ups without canceling the entire print job.

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kinda not sure what I feel on this one.

In the instance of a “minor flare up” most of the options I’ve seen for putting out the flame (including blowing it out) have the potential to move the material, even slightly. In those instances I can see why cancelling the job would be worth it since the material in the bed has been moved (unless the auto registration can pick up the existing portion of the design and flawlessly continue from that point.

But if you were to open the lid because there was a fuzzy on the macro camera lens wouldn’t make sense to stop the job.

not sure what behavior I would prefer in the GF

I think if you’ve lit your piece on fire, you’re very likely going to want to start with a fresh piece of material.

I, for one, would very much prefer the cost of replacing a small piece of material to having a flame destroy my multi-thousand-dollar laser. To me, the answer is simple… lid lifts, laser disengages and quickly moves to 0,0. It saves everybody/everything.

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I think we’ll be able to do both - pause it for non-flame up situations and resume later, or kill the print by opening the lid.

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my above reply wasn’t clear which issue I was referring to. I was specifically referring to whether the print job should either pause or cancel.

I agree that in the case of a fire, or most anytime I open the lid, having the head and gantry move out of the way will be more helpful.

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When i’ve used a laser, sometimes just having the laser shutoff for a instant is enough for the flare-up to stop right away. I’ve spent hours cutting plywood and never had fires that needed more than a temporary shutoff of the laser.

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