Help with 3/4 ply

Need some help please. I make Military flags out of 1/2 material and wanted to use 3/4 material. The problem I’m having is the art work won’t fit on the material (20 x 12) in GF. I took the crumb try out, raised the bed 3/4 of an inch, placed my 3/4 inch ply on top of that, set my material thickness to (.50), set my focus height to ( .18). My flags measure (19.5 x 10.168). I can only get my flag to measure (18.609) in GF. I’m sure I’m doing something wrong in the Material thickness or focal Height setting. If anyone has suggestions, it would be much appreciated. I have 6 to do for Father’s day. Thanks

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So you have a couple of problems.

I’ll break them down one at a time, hang tight.

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First off is your width, Engraving moves side to side, and the laser head needs some space to speed up and slow down. How much width that turns into depends on how fast you’re going – just like in a car, you the laser head needs more space to “brake” when it’s going faster. That means that the maximum width of an engraving will change depending on the speed you’re using. Someone broke down maximum engraving width by speed somewhere, let me see if I can find it.

Ah, @jacobturner, among others.

OK that’s problem #1. Your design will likely need to be resized.

Problem #2 is your height, that’s coming right up.


As for the height issue, the way you’d tackle this has changed over the years. The simplest method now is the set focus feature.

Your setup sounds good, you raised your .75" material another 0.75" off the bottom of the glowforge, that should give you a total height of 1.5" from the bottom of the glowforge and that’s right in the sweet spot.

Since the crumb tray is right near 1.3" tall, that means your wood is now about 0.2" above the crumbtray height, (1.5" material height - 1.3" crumbtray height), so your material thickness and focus point should be about 0.2". Now you can get fiddly with calipers and get it dialed in exactly, or you can set your focus height in the engrave step to auto (delete it from there), and then use the set focus feature. It’ll set the material height for you.

There is one edge case where this advice should be ignored: if you are intentionally defocusing the engrave, then you’d want to continue to manually set the focus height in the engrave step. You entered material thickness of 0.5", that is essentially saying “focus about 0.3 inches above my wood”, which will give you a different result from setting the focus point directly on the surface of the wood.

(search the forum for “defocus engrave” for more info if this is news to you and you want to know more)

Most people don’t defocus wood, but that doesn’t mean you aren’t doing it intentionally here.

So, yeah that about sums it up. You were pretty close, just a couple of minor details that aren’t exactly intuitive.

Btw your next question is probably going to be about how to align exactly on a precut piece of material like your 3/4" plywood. For that I would suggest searching the forum for information on jigs. It’s a challenge with thicker materials and no crumb tray but it’s definitely possible to use jigs to get it exactly right.


The TL;DR version - you’re not doing anything wrong.

The widest image you can engrave at 1000 speed (which is the default for the draft and SD modes) is just over18". You can stretch it to about 19.2 at lower speeds, but then a full-bed engrave will take many hours.

Your solution is to reduce the size of the design and material.

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