The wavelength is not different. The wavelength would only change if it went through a medium (which is not happening in this case). But the wavelength does not change from traveling the distance that is .5" from the laser head to 2" from the laser head. I never said that the wavelength changes. Instead of inquiring about what I meant in a statement, you made your own interpretation and assumption.
Ah, I see where you might have made assumptions from my statement. I agree that I sometimes phrase things a little oddly and can see how it can cause confusion. I always am happy to clarify what I mean when I say things. Never hesitate to ask 
So for one of my glowforges I decided to have it cut out a 10x18 grid and I used a sharpie pen to mark where I need to line it up at when on the base. Sharpies come off the base with magic erasers and so I am fine with this way of doing a grid at the base. I think there are many other creative options out there though.
Hmm you could make a vinyl or mylar stencil and align it on your base, then use sharpie to mark the inside of your GF with a semipermanent grid, then remove your stencilā¦ Added benefit: zero height, so it wonāt interfere with the crumb tray in any way.
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I looked more closely at your grid picture, and Iām more concerned about these spots:
Is that an artifact in the picture or do you have little jaggies there? If itās not in the original artwork your GF shouldnāt be doing that. Itās almost like the GF is skipping or something, maybe a problem with the stepper motors, wheels or rails?
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Interesting, I hadnāt noticed that. I will do some tests with it. The grid was made on the glowforge I got in last month and so it is brand new so I certainly will look into that. Thanks!
I like the way you think! I was thinking to just use a ruler to draw lines but making a stencil to use will be much more efficient.
(Late to this party) There are sheet plastics with the word vinyl in them that are not actual vinyl and advertise them as ālaser safeā but you need to treat them like something sold as a scarlet snake that you really want to make sure is not a coral snake as the difference is similar. There have been photos as has been noted before.
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I bought a few things from them, There was an Android tablet that had two phone lines built in. The phones never worked but it was my go-to tablet for quite a while. and might work still if the charging port worked.
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Check out this wicked previously:
From prerelease days!
Wow even earlier from 2015, the 76th topic!
This discussion is #93,667 by contrast.
Hereās the original support ticket for that guy who repaired his pvc damage:
Anyway, I was looking for a post that I remember where a user cut PVC on their very first job and destroyed the machine. Canāt seem to find it, anyone else remember it?
That might have been meā¦
I had my GF for less than two weeks when I cut the PVC.
I cut, engraved and designed a really cool laptop bag out of alligator molded PVC from Jo-Ann Fabrics.
Spewed HCL all over the inside on my machine.
Dead within the first two weeks it arrived at my doorā¦
Believe meā¦I WAS VERY UPSETā¦first at GFā¦but then at myself for not doing the proper researchā¦
When given a choice of spending another $2000 to get it repaired or tossing the GF in the dumpsterā¦youād be surprised at what you can accomplish when your willing to throw away a $6000 machine that youāve had for less than two weeksā¦
Thusā¦RECOVERING FROM PVC CUTS was born lol
And here we are today. Full circle. Stop.
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Alsoā¦looking back at the threadā¦
Was the user that made the mistake of cutting PVC on their first jobā¦
That may be the owner youāre thinking ofā¦