Cutting Without the Crumb Tray - The NO MATH Edition

Thanks for this! It made me feel better about taking the crumb tray out.

I did this with a 4/4 board that was surfaced to about .840 and when I was adding material to push it up into the correct range I stumbled upon a height of .130 which is where I find a lot of the medium PG hardwood coming in. Then I just used the PG settings and didn’t have to worry about settings for the engraving I was doing. I suspect this would work if you got material into the range of the thick PG materials too.

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A picture is worth a 1000 words, thanks so much for sharing. Math was never my best subject, so really appreciate the help!

I wonder if you can tell me if I made a mistake on this method? I did the no math method, zeroing the calipers at 1.3885 (approx GF tray, etc measurement) and then I measured my material to engrave with the added risers and came up with a measurement of 0.1630, so put 0.17 as the focus height. The actual material thickness is .6", but when I try and input that number, the GF software automatically changes it to .5" The end result is that when I go to print, the laser is not reaching the material. I have rebooted computer and GF, in case it was a calibration issue, but that did not help. I have actually already previously engraved this same material a couple of weeks ago without any issues, so I’m not sure what I need to change. I would appreciate any suggestions you might have.

No. The crumbtray height is always the zero point for the GF. When you remove it the zero point would be, in your case, 1.3885" above the bare floor of the GF because that is how tall the crumbtray was. So, since you have stacked a total height of 1.630" off of the bare floor you just need to determine how much higher that is above the original crumbtray height. Pretty simple. 1.630" minus 1.3885" which equals 0.241". That is 0.241" above where the top of the crumbtray would have been. So, 0.241" is what should be entered in the material height selection. Don’t enter anything in the focus height. Adjusting focus height is an advanced technique that you will discover much later.

Also, keep in mind that no material height entry may be higher than 0.5" above the original crumbtray top, or lower than 0.01" So if you end up with a number that is lower than 0.01" or larger than 0.5" you will need to adjust your risers to fall within that range.

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Thank you so much for your reply! That’s why I don’t do math. lol.

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Great instructional. I do the same technique also but you took the time to make a super clear tutorial on this. Good job! sharing is caring :stuck_out_tongue:

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I can see that this has helped a lot of people and I tried my hardest to follow along, but somehow ended up more confused than when I started. It’s strange to not understand something that is listed out in steps.

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It can be hard to wrap your head around. :slight_smile: This visual really helped me “get” it:

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Think of it this way: The laser only “sees” a half-inch slice of space – located from the surface of the crumb tray to 1/2" above it. Anything sticking up higher than that will be run into by the air assist, and anything below that is too low for the laser to reach.

So if you want to put something thicker than 1/2" in there to laser on, you have to take out the tray, but make sure the part to be lasered is sticking into that 1/2" space. That means that 1) you have to figure out how much stuff you need to stick under it to get it up high enough, and 2) you have to figure out how far into the 1/2" space it extends, so you can “lie” to the glowforge about how thick it is, by telling it just the amount of the item that exists within that space.

Hopefully with that explanation, and the picture, you can go back to the instructions @Jules wrote and they’ll make more sense. :wink:

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This! This makes crystal clear sense to me. Thank you so much. I could instantly visualize what I need to do to make it work out. Seriously, you are a true gem of a human.

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Nah, I’m just more of a kinesthetic learner, and you probably are too, so we share the same “explaining” language. :wink: I had to go through @Jules’ steps a bunch of times before I finally realized what was going on, and then it just clicked. :slight_smile:

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You have said a mouth full right there! This does not happen to me often but when it does I wonder out loud if I’ve just had a stroke! :crazy_face:

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Quick set up jig.

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I like that gauge a lot. I wonder if rule marks between the min and max would be accurate enough to measure directly off the gauge.

I know this post is a year old - but just in case you never found it again: Tray Removed - Calculator - Updated

I just hit this thread today - I haven’t done anything without the tray yet, but it’s coming soon :slight_smile:

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That is a great idea!

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I take a different approach.

Place your calipers against the side of your cutting head, depth gauge pointing down, starting flush with the bottom edge of the black plastic (nearest to crumb tray).

Now, extend the depth gauge until it touches the crumb tray (you may need to move the head or calipers slightly to get the two small metal bits aligned to make contact). At this point, zero out your calipers.

Now, to measure the height of any object, you just put the digital calipers back up against the print head and extend the depth gauge once again. As long as your reading is negative, you just enter that (as a positive value) exact measurement as your material height. If you do get a positive value, then you need to add some material underneath whatever you are working on, and what you add should be at least as thick as the positive value showing on the calipers.

This works for even finding the material height of things when you ARE using the crumb tray, but forgot to measure in advance of putting it in the machine (I am frequently guilty of this one).

Of course you could do this with the calipers pointing the other direction, extending the head instead of the depth gauge. That would make it easier to hit the crumb tray regardless of positioning. Not sure why I do it upside down…

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Thanks so much! Great info here!

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Thank you so much for this. The other tutorial with all the math made my brain hurt. I can handle this one :slight_smile:

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This works like a charm!!! Thank you thank you thank you!!

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