What is the y offset value? – Is it the rotational radius?
The Y offset is the vertical distance the motors are above to top of the work area.
The rotation radius is the distance between the chain “0” point and the bit, typically dictated by your linkage kit.
Yes, we reset that value – Playing with the y offset doesn’t seem to affect the vertical calibration, just move the whole grid up or down – Anyone come up with a measurement after drilling holes 900mm apart on the vertical axis?
I’ve tried the PR#547 that @rjon17469 has written, and the discussion is here. If you’re comfortable with development-grade software, you could download the .zip of the PR here and try it. If you do try it, post your comments to the comments of the PR so your findings can help polish it.
The latest versions have many, many improvements, so update!
If you change the Y offset value after calibration, it will just move the grid
up and down.
But if you change it before calibration, you will end up with a different
rotation radius.
The new calibration routine will calculate the yoffset value as well as the
rotation radius.
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Is the new calibration routine you refer to part of the 1.02 upgrade?
Not yet, it will be in 1.03.
No, the new calibration is currently only a PR to be added (PR #547)
It’s being tested by people applying it manually for the moment, and if it works
well, it will probably be integrated this week or next week.
I finally got my linkage kit set up! I wasn’t able to run the calibration procedure because my current stock doesn’t extend to 10" of the edge of the work space (I guess I’ll need to get a new sheet of plywood for that!).
I did flip the “triangular kinematics” switch and set the rotation radius to 260. I then set out to cut a 4" square. Horizontal was okay- 3" 15/16, but vertical came out just over 3" 3/4. I am still running the temporary frame (still awaiting the new stock frame instructions). Other than build a new frame and run calibration, anything else I should check to increase accuracy?
Running the triangular calibration routine does a great job of of automating the calibration process. It’s definitely worth getting a sheet of crap plywood to have around for calibration. I have some 3/4" CDX I’ve been using for the triangular linkage comparisons that is relatively cheap (~$30) that would be well suited for the routine. Someone correct me if I’m wrong, but the routine also determines the chain sag correction value automatically, which is hard to determine manually. It’s fairly high-level math.
If you really want to do it manually, use the simulator to see how to adjust your calibration to get it dialed in. You can then run a couple iterations of your 4" square until both X and Y are within tolerance. I think you’ll need to increase the rotation radius, it should be somewhere around 270 if I remember correctly. My machine came up with 267mm for the 45 degree linkages.
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Even if you’re using the temp frame, attaching a 2x4 between the motor mount arms would help lessen error from arms flexing
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One suggestion on the calibration cuts. Probably a stupid one but, maybe provide the option to offset the whole pattern left or right an inch or two. That way you can run the calibration routine a couple times on the same sheet without having to reposition the sheet. Or in my case the spoilboard 
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unfortunantly, the math for the calibration cuts only works if they are exactly
symmetrical around the center (things get MUCH more complex when the left and
right aren’t mirrors of each other)
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Got it. I thought that would be the answer. I shall purchase a calibration peice.
You can always get a cheap sheet of plywood or osb for calibration. It doesn’t need to be anything expensive (or nice). I use 3/4" CDX sheathing myself, but that’s because I have a ton of it from demoing a “finished” basement in my parent’s last home.
Oh for sure. I simply have the issue of transport. I usually borrow trucks when I buy plywood so it requires planning. A silly problem to have for a person who owns a 4x8 sheet CNC machine 
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As someone with a Subaru Impreza sedan, I can entirely relate. I’ve tried strapping sheets to roof racks before, but I get a bit sketched out by having a sail on my roof. My brother has an F250, so I usually borrow his truck, when it’s available.
While you’d think most people with a full-size CNC would have a truck/van, but I have a feeling the Maslow might be a special case because the cost to entry is lower than a typical CNC it’s size.
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I have a 5x8 Tractor Supply trailer for our Vibe and Outback. Both cars and the trailer together are less than a tricked out truck, and no arguments about who gets to take it
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I wish my car could pull a trailer. Then I’d just hitch our 4x9 open-topped utility up every time I need to go to the lumber yard. Next time I buy a car…