Jig help for thick material?


I’ll do my best to clearly explain my question, so bear with me!

I have an aluminum project enclosure (box) that is about 1.2" thick (height) that is powder coated. I know the laser can handle removal of the powder coat with excellent results. My problem is that the enclosure is too tall to sit on the crumb tray, and I need a pretty exact location to be engraved. Any thoughts on a work around to get exact placement based on a test burn/jig set up?

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Just the one or several?



Ideally I could use the jig/setup again to print the same precise location multiple times, but if the method is easy, I can redo it each time.



You can remove the crumb tray and then add shim your 1.2 inch box off the bottom of the Glowforge to the proper cutting height.

There are a couple of threads that will explain how to get the exact height of your crumb tray so that you shim the part into the proper position.

I’m actually using a cardboard jig right now to cut some items too big to fit on the crumb tray :slight_smile:



For quck and dirty you just need to claculate your totoal hight using the calculator found here:


cover your box with masking, do a very light engrave or score, so light that it just marks the mask, adjust your position, crank up the power and go.

for a longer term jig, you will need to find someplace on the machine to physically align a jig, cut it out and then install it.

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I think the problem @changemakers is having here is a similar one @takitus had brought up? You want to make a jig for exact placement, but the material itself is too thick for a standard type jig, where you just cut a hole and put your item in, without something totally elaborate.

Here’s how we worked around it… Takitus was working with a bit skinnier material, but it should still work.

First, you’ll need something at least .20” to prop it up and get it into focal range. Without the crumb tray, the material needs to be about 1.37-1.38” above the floor of the machine. The links above can help you figure out the math.

You can make an outline of the material shape in your design software and then align the engrave to the material outline. You’ll want to score the outline of the material onto a piece of material that will show you where to place your item.

Normally, the Glowforge will complain about this because the material surface you want to score the outline on is below the focal range of the beam.

To get around this, you’ll need to specify the material height, and then set a manual focal height that is different than the material height - say .001”. This should bypass the material height error and run the score. The beam will be out of focus when it hits the jig/outline material, so it will need more power to mark.

After that, place your item inside of the scored outline, make sure the focal height is correct for the engrave, and run the job.

Basically, I would arrange it like this if it were me:
Put a .25” spacer on the bottom (I have some standoffs that I use)

Put a piece of .08” chipboard on the standoffs.

Run my score outline for box placement.

Put my box on top of the chipboard and set the focal height for the engrave to 0.16” (total stack height of 1.53” minus crumbtray height of 1.37”)




Ahh! Thank you! Gonna try this asap. I was thinking that due to the material height being below the focal range it would cause the outline to be inaccurately placed. Thanks again.



This is a neat idea. Have any engrave/score settings that have worked for you?



It won’t be nearly as fine of a line as it would be in focus, but it shouldn’t be horrible/unusable either. I haven’t gone that far down out of focus though, either. Let us know! You can always prop the material up higher to get the outline piece a bit closer to the focal point.

The key though is the manual focus height to override the auto focus warning.



Cool. I’ll do some napkin math to get the distances optimal. I’ll report back on Monday if I get a chance to run some tests. I’ll keep an eye out for the override.

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When I say very low I mean very low. You can usually get the mask to mark at a power of 1 or 2. We’re not looking to heat anything up much and definitely don’t want to cut through it. I’ve done this on a lot of wood projects with the tray out. It is important to measure your part and your spacer with calipers as a little mistake can make you way off! Get the numbers right and put the piece right under the camera and you should have a first try that is less than a 1/16th" off.
You may want to start another low power pass after adjusting to make sure before you open the flood gates.



Jbmanning5’s method is solid. If you want to really back it up against a bulletproof jig, you might want to try my rat skull method:



I made a jig for this purpose. It uses risers to get a sheet of cardboard up to the same height as if it was on the tray. I cut out the shape (slightly oversized) of what I’m engraving in the cardboard, and then sit the object in the hole against the back left corner.

I have jigs of different heights (at .25” intervals).


Align material without bed