Laser engraving not centering on target

I recently got some slate coasters from Amazon and thought it would be cool to engrave them. The images came out awesome with the setting I found in the community.

The only problem I am having is centering. If I place more than one coaster on the tray, the center one comes out perfect but the ones on the sides are off center to the middle of the bed. I tried 2 sets. Square and round. The first set, square ones, were placed 3x side by side. The center one was perfect. The left one was a little to the right and the right one was a little to the left. The round ones were placed square. 2x2. They all came out offset to the center of the bed. They all hit the coasters just fine with no overlap but weren’t centered.

Could this be a focus height issue? I’m new to the laser thing and am having a hard time with non Prograde items.

It’s a “fisheye effect” of the lid camera issue, and the only way around it with 100% certainty is to create a jig for placement. (Or do each individually directly underneath the lid camera, or do each individually after using Set Focus on each coaster…I guess there are several methods now.)

First thing you want to do is run the ReCalibrator if you haven’t done it - it improves overall visual alignment dramatically. Then if you want to do a bunch of coasters at one time, use Set Focus in the center of each coaster, align your design visually, then use Set Focus again on the next coaster, align that one, etc…

I find it easier to cut one jig and then drop the items in and boom, they’re all done, but if you don’t keep a lot of junk cardboard around, you can use Set Focus to do it now. :slightly_smiling_face:

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Searching for “coaster alignment” would yield this:

Search is your friend.

(It also finds a lot more)

Thank you Jules. I did run the Recalibration tool but it didn’t fix the problem, yet. I ran it after the first engrave with the square coasters and then tried the round ones. I ordered some new ones that should be arriving today or tomorrow and I’ll try again.

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Well, keep in mind, the Set Focus tool is only going to improve the alignment placement where you click it.

It works like this…where you click with the Set Focus tool, it takes a measurement at that spot and the view temporarily becomes as if that spot was right under the lid camera. So you would align the design for that coaster. But then you have to click the Set Focus tool on the next coaster to align that one. And so on. When you get them all aligned, then you run the job. But each time you click Set Focus somewhere else, the earlier views of the designs that you already aligned are going to change a little. Do not change them again, they are actually placed where they need to be.

Because of the fisheye effect of the lid camera, the designs are always going to appear to be slightly out of sync at the edges of the bed. EXCEPT immediately after you click Set Focus at that location.

To get accurate “physical” results, which is what ultimately counts, you have to be willing to accept that what you see on the screen is going to appear to be slightly off. You cannot accurately align a print at the edges of the bed without Set Focus. (Or a jig, but that’s a mechanical method that most new users are slightly nervous about. They shouldn’t be…it’s always 100% accurate and a big time saver for batch jobs.) :slightly_smiling_face:

It’s very difficult to teach folks not to believe what they see on the screen, but in fact, that’s what you need to learn to do. After a little while, it becomes second nature to think in terms of fisheye correction.

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Just a couple of possibly helpful hints - if you’ve decided a slate engrave is no good and you’re not planning to use it (or gift it or whatever), you can use the other side to test different settings. Also, you can’t sand the engrave off with very fine sandpaper and you’re back to a fresh surface you can engrave on.

Even if you’ve used shellac or poly on the coaster before engraving (to improve the contrast), you can still use the sanding trick to reuse a failed attempt.

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The other thing to keep in mind is that “set focus” is going to set the focus where you put it, but the camera correction is then going to be based on the assumptions that ALL of the material across the entire bed is the exact same height. Even a difference of a fraction of an inch (in height) can translate into a pretty significant offset between what you see in the UI and where it actually prints.

If you want reliable placement for multiple objects that are not perfectly uniform in depth, you need to use a jig.

So, can I set the focus on multiple points of the bed? For instance, can I set the focus on all the coasters on the bed individually?

Yes, but you need to understand that “individually” is the operative phrase. You can set focus on one, place your artwork there, then move and set focus on the next, set your artwork, and so on.

It won’t necessarily fix the problem entirely, but it is a hack to individually place bits of art on separate things to print at the same time. The laser will only remember the last “set focus” area, so that is the height that will be used everywhere when printing.

You can use the set focus on a coaster and print it. Then you can use the set focus on the next coaster, arrange the artwork and print. You only get one focus point per print.

Jig is really the way to do this. It allows mass production as well since it is fire and forget. For slate projects before I just used a jig (don’t even need snap marks, just use absolute size for the jig and tiles (12x20”) just note slate tiles are not precision cut and often have a little slop in them so your jig needs to be slightly looser than the tile size.

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Once calibrated, you shouldn’t be off by more than 1/4” at the corners. When I first calibrated my machine I couldn’t get better than 1/2”. I contacted support, they did a
“Remote adjustment” and now my worst case error is less than .1”.

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I guess my biggest concern with a jig is, I dont only make coasters. I can make a jig. That’s the easy part. My biggest question now is how do I use the same jig, after removing it from the GF, without having to make registration cuts everytime I replace it in the GF? Or will I have to make registration Mark’s everytime? Lining up the image is the thing.

Y’all are awesome. This community is worth the money spent on the GF.

Place a sheet of paper on the bed and do an initial print of just the cut outline of the coasters with a very light score setting. That will give you a set of lines on the paper that will correspond to the holes in your jig. Just drop the jig on your paper and line up with the scores and you’ll be good.

Make the jig large enough to just fit nicely into the recessed area of the tray at the front and sides.

Some people note their tray placement is not repeatable. I don’t have that issue, but there are simple wedge-style spacers you can use to ensure it’s placement is consistent.