That’s a valid question, I could be wrong, but as long as the beam path is not more or less than what it would normally be, the focus should stay fairly close. It’s been a few years since my college physics labs and I have been retire almost 10 years. Maybe @eflyguy could weigh in.
I’ve been absent for a while due to non-covid health reasons, and have since decided to make my design freely available to the community. If you find it useful, and would like to make a monetary contribution, you may do so via PayPal, using my email address: taylor.a.jenkins@gmail.com. Thanks, and I would love to see any improvements you make.
Materials needed are 1 sheet of proofgrade medium draftboard, or any other similarly sized material, and two M8x1.25 socket head cap screws of 10 or 15 mm length.
Right click the thumbnail image below to download the svg.
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I hate to hear that you have been ill, I hope you are feeling better. Thank you so much for sharing and all the work you put into it.
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Thank You for share. It is a very interesting project to play with.
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Genius, pure Genius. So simple yet elusive. Thank you for thinking outside the box to come up with a genius solution. Kudos…
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I’ve been really stoked to jump into this. I’m down to my last 6 plaques of a big order, then I’m playing with this file.
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Thank you very much @taylor.a.jenkins for your contribution. I look forward to making it and trying it out. Regards.
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are there assembly instructions anywhere? I see a bunch of finger joint pieces but I don’t have a clue how it’s supposed to work. 
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Take a look at the photos and videos above. That will show you how the pieces fit together. When gluing the pieces together, be sure to not leave excessive residue buildup in the corners, to ensure the guides will fit snugly and flush against the internal surfaces. The two small pieces with the hole in them screw to the sides of the gantry and allow the slots in the ends to ride up and down for adjusting the height of the work piece. I placed boards underneath the fixture (see video) to position smaller work pieces in the right focus range.
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Hello! I am so interested in this, but I am having trouble fitting this all onto a piece of draftboard. When I upload the file, I have to scale it down to fit into the printable area, and then it is not long enough to reach the edges of the machine when I put it together. Any advice?
It just barely fits within the cut window on my Pro machine. What machine do you have? Rather than scaling it, just give it a slight nudge left or right, up or down. Let me know if that still doesn’t work.
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Thanks. I have the basic machine. Just can’t wiggle it on there. I downsized and Shimmed the length by 3/4 inch. Putting it together now
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I just finished an updated version that will fit more easily within the cut window.
I also added two additional screw holes to the guide tabs that will offset the centerline of the fixture forward or backward a 1/4 inch from the focal point. This will help to handle slightly larger objects. When attaching the guide tabs, ensure orientation is such that the screw is at the top of the tab. To shift the fixture forward for larger items, orient the tab such that the the two offset holes are at the top, and place the screw through the hole closest to the back of the machine.
You will need to modify the width of the slots in the positioning guides to match the rolling diameter of your object, using the formula in the design file.
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Continuous improvement and a nice updated share. 
Thanks for doing that.
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Thank you for sharing so generously.
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I’m just as impressed today as I was the first time you posted about this 
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This is a really impressive bit of engineering/ingenuity.
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Any chance you could repost the videos? Would love to see this in action.
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Totally missed this! So clever.
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I was wondering when someone else would figure this out. well done.
I made one of these a few years back that was similar, and was hoping to publish it in the catalog, but it never arrived before I got a bigger laser.
There are retaining bolt holes used to hold the gantry in place during shipping that you can attach to your carriage, which it looks like was done here. I personally used two pieces of acrylic down the sides with rubber rollers that spanned the distance between the two that would hold the object to be engraved, that were height and gap adjustable. It helped prevent the object from skidding on the bottom and ensured rotation.
This is cool. Im glad to see someone else putting this idea out there.
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