I’d say it’s moving 3mm, not all the bearings are touching the pipe. When I tighten enough to touch the pipe on all 3 points, it has significant resistance.
I am not sure you can see it in the pictures but all of my tension bolts are extremely loose, as in just holding the bearings in place. I always recommend taking the gantry all the way apart. Swapping the xyz plates and put it back together, no tension on the tension bolts, should be ideal. If not 1/8 turn each until you get where you need it. I have seen broken tension bolts parts…That should not be a thing. They are actually interference fit.
I guess we were thinking on the same lines… I reprinted the XYZ plates and spacers. Once I get the old ones taken apart and new ones installed I’ll let you know how we’re looking.
Back to the accuracy/precision testing… maybe instead of a pen, how about scratching a piece of acrylic? You could get a rather fine pointed tool on a very stiff mount that way?
I am pretty sure the ball point pen is going to have the absolute smallest amount of drag of any tool. I Think.
Well printed the new mount, turns out the old one just wasn’t on there very tight…GRRRRRRR. Stuck the new one on anyway, very tightly.
Same numbers basically just more consistent. One square was as perfect as I could measure. That lead me to believe the opposite corner had to be the issue.
Corner 4 seemed to be perfect on both the small square and that angle of the circle. Best I can tell of the two possibilities moving the X2 out about .25 should correct this as best as I can get it. Measuring as best I could from the corners to rollers seemed to point to the same thing. X2 seemed a bit too close, both Y seemed the same.
I think I had an error in the last readings the far diagonal was probably ~1mm out, not .1.
One more try and then I have to pack orders. Sorry for everyone that didn’t get their box shipped today, it was for the greater good I promise.
Okay, I’m a dummy and over complicated everything.
I have it within as close as I can measure now, so the large diagonal within ~0.5mm or so, and the small guys are probably within ~0.2mm. Honestly I have no way to get it any closer with a line on a paper.
I thought some crazy trig was going to come it and things would get magnified…nope, dummy. Give a nerd a calculator and everything is an equation.(need to get that tattooed on me for sure) So from Y1 that corner was about 1mm low…M666 Y1 BAM!!!
So easy.
Now How do I write instructions?
1-Measure the largest diagonals you can to the X1 and Y1 home positions.
2-Since you can only offset in the positive direction, offset the endstop with the short diagonal. By about the amount it is short. (technically it is probably just a hair over this amount).
PS…My offsets are both Zero…I had originally added and offset based on the corner distances…I feel real dumb right about now.
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How’s that MPTTM coming?
I think you are right, time to give it a try for real. Hmmm.
So I started to take things apart, to get at the center gantry. When I took the belts off, I gave a little tug on one of the pulleys. It fell right off. I had replaced one already, but apparently the whole batch that I got from some guy in CA had bad grub screws. Luckily when I bought the replacement, I bought 5 of them.
I replaced the other 3 pulleys, and I was able to plot great crowns!!! I wrote the kid’s name and a few other things on my whiteboard. I think this thing is ready for a spindle!!!
When it finally quits snowing and I can get out in the garage, I’ll build a table and get this thing cutting stuff… so excited!!!
I keep thinking I want to enlist my low rider to draw on a chalk board or something. I like the lack of waste of something like that.
You’d have to build some sort of a wear factor into the piece of chalk, so it’d drop the Z axis as the chalk wore…
They make chalk holders that are spring loaded. Plus, it doesnt have to be perfect.
Another thing would be angle the chalk and rotate it as you go to minimize the width of the chalk line…
Re: pen mounts, here’s what we need: https://www.youtube.com/watch?v=HciNR-tskwQ
I’d model it up, but I’d need some way to know exactly what the mating interface is. Is there an STL or something for it?
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No matter how long I stair at the instructions (here and on the duel endstop page) I don’t understand what you mean…
But there is only one diagonal that goes to x1,y1 ?
Maybe it would make things more clear if you could illustrate exactly what you mean?
I’ve attached a quick mockup of the rails and the way I see my coordinate system at the moment. I’m guessing that I’m visualizing something incorrectly.
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From your picture use the machine to draw the blue square, Measure and compare D1 vs D2.
Ryan,
I hate to be a pest but would you mind clarifying further?
So per my drawing above, which diagonal is X1 ? Why is it X1? It takes at least two points to figure which diagonal is which (technically 4)!!
I gotta tell you I’m disturbed with myself that I’m still not understanding what you mean and I know I won’t be able to let it go! Can you confirm this :
X1 rail = bottom rail, X2 rail = top rail
X1 endstop = bottom left, x2 endstop = top left
y1 rail = left rail, Y2 rail = right rail
Y1 endstop = bottom left, Y2 endstop = bottom right
In the very beginning we moved the two endstops on the bottom left corner (what I’m calling x1,y1 endstops) a hair closer to the bottom left corner, correct? The endstops at the top rail (x2) and right rail (y2) are “fixed”? M666 offsets off just the bottom left corner alone?
It’s hard to describe coordinate frames in text. This is tough without a whiteboard.
First, from Ryan’s instructions, I think his X1 and Y1 are in different corners. So when he says the X1 diagonal, he means the diagonal that starts or ends on the X1 endstop corner. Keep in mind the motor you hook up to X1 or X2 is arbitrary, so everyone’s is different.
But, your drawing is better, so let’s use that.
If D1 is shorter than D2, you can adjust it by offsetting the X2 endstop. This wil move the top side of the rectangle to the right, making D2 shorter and D1 longer.
You could also offset Y2 to move the right side up which would also make D2 shorter and D1 longer. You may be fixing square but making it less parallel to the rails, but remember that the reason you’re adjusting this is because the rails are not square. Hopefully, these are small adjustments anyway.
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Thank you Jeff, that was helpful.
I wanted to note that Configuration_adv.h states “… X_DUAL_ENDSTOP_ADJUSTMENT … is applied to the X2 motor.” Ryan’s instructions refer to setting X1,Y1 offsets. I think this also contributes to my disorientation.
And for the record I also want to clarify that I do in fact understand how to rack a rhombus back to square! I wouldn’t want y’all to think I’m that slow! 
I’m sure you do, but for every 1 person who asks, I have to imagine there are 10 that don’t. Plus, you and I probably think of things differently, so I tend to go from the basics so everyone is on the same page. (Sometimes it’s condescending or preachy, but there are costs to a text only interface).