# Double sided cut

Only if it tells you which way to flip it. If you have a 6x6 perfectly square piece of MDF it won’t know if you flipped it sideways or vertical.

Also, I mentioned the clip in the case where you were cutting through a perfect circle of material. It would have no alignment reference once you flipped it over. Thats gonna be tricky. Odd shapes will be easy

More symmetries = more difficult

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Yeah, understood. I was answering the same questions on two different threads and got confused which one I was in. Yes, the two sided cut capability, according to Dan, assumes that the material is only flipped on the longitudinal axis. The image is then aligned mirrored and the cut continues.

edit: In reality half of my answers aren’t directed to the person I am replying. Some are just clarity for others that may be new. Both you and I understand how it probably works given all of Dan’s posts, but there is still that 1% possibility that it will function differently.

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Always flip it sideways. That is what the software will assume.

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How would that work with a perfect circle?

Dan last posted an hour ago so may be done for the night.

I think your question was part of the original point posted way above. You don’t.

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Flip very carefully!

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Tbh I’d think you’d want to engrave and cut one side, then flip. You’d be able to immediately return it to the exact same position since you just cut a big hole out.

Though I suppose you run the risk of rotating it slightly.

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I don’t get that @dan . Bad example but, what if I want a 1/2" circular coaster? How would I flip in order to cut the additional 1/4"?

• Tom
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You can’t. Cut the coaster shape last. See generic explanation below.

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Can’t quite grasp what people are confused about. It’s really very simple for the user.

1. Take a piece of thick blank material from which you want to cut a pattern. It doesn’t matter whether you want to cut a circle, rectangle, snowflake or even a very complex shape like a tree.
2. The original material from which you will cut your pattern must be something with well defined edges and/or corners. A rectangle is easiest but other shapes with edges/corners may be fine. I’ll explain further below.
3. Cut the pattern of your choice at least halfway through the blank material. The example given by the company is cutting 1/4" deep into a 1/2" thick piece of material.
4. After the initial cut, flip the material by hand in the longitudinal direction like you were turning a page. You are now looking at the back blank side of the material.

Here’s the explanation. The pattern you just cut is now a mirror image, facing down, where you can’t see it. The camera can’t see the cut either because the material is opaque. But the Glowforge knows what the edges of the original material looked like. And so through sophisticated cloud S/W, can re-register the new material with the pattern to be cut from the back side. It accounts for any slight error in position and rotation you introduced when hand flipping the material. (you will introduce significant error no matter how carefully you flip the material) But the Glowforge S/W very precisely aligns and mirrors the pattern to be cut with the new material position, and hopefully, the original cut.

THE BIG IF. If, for example, your original material was a circle (a coaster) the S/W can not determine how much of an error was introduced when you flipped the material. It might be 0.1 degrees off, it might be 4 degrees. A circle looks the same from all sides. There is absolutely no way for any S/W to determine rotational position if the original material is a circle. Can’t be done. Other shapes may give the Glowforge S/W similar problems so it might be smarter to start with a simple material shape like a rectangle. This is not a Glowforge limitation.

Lastly, Press the button and finish the cut.

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Or you do, if you’re very careful!

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If the S/W can’t re-register the material properly because of the ambiguous shape then you wouldn’t be able to benefit from the double sided cut capability. Manual registration could be done on any laser including the Glowforge.

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Seems exactly as I’d expect. Maybe I was just tired when I read the above, but it didn’t completely lock in for me.

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Explanation wasn’t directed at you. Can’t count the number of times I have misunderstood the questions. Seemed that there were a lot of the same questions, so clearly my original attempt at answering wasn’t making it.

Only the material is thick, not the questions.

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A lot of things already pre-cut into circles. For those some thin tape with registration marks wrapped around the edge could fix orientation issues.

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It would be interesting for you to try using your K-40, a position jig and registration marks whether you could cut a thru pattern in a circle from both sides with acceptable precision. Maybe a 5 point star as a test pattern. I’m guessing it would be pretty darn tough but I can’t get to a laser to try.

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How about tape or maybe something thin but more rigid extending out from the edge to give positive physical registration? You’d have to work with the design, but it would likely be worth it. (I would have a hard time trusting optical marks unless they were really well set up so that there wouldn’t be parallax reading them. and even then.

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It would be interesting. If it was something I had to do repeatedly I would just cut a jig out of acrylic for it. A circle that ran around the outside with a singular arm sticking out. Kind of like the letter Q. Then I could flip and make sure the arm is back in he same slot and know that I have everything lined up.

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Oh, now you’re making me giggle. Is it not a feature if other lasers can do it?

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