Some of you pros give me hand here checking my logic today.:
After getting some strange scaling issues with cutouts I decided to redo calibration project by RobertA_Rieke.
I got some terrible results but error was consistent across all the cuts so obvious choice was trying to adjust 100 and 101 value that I have previously set to just below 40mm.
But during the process something started to bother me as I keep remembering that the belt has manufacturer specified tension. I would imagine that the value of 2mm between teeth of the belt would be determined at this specific manufacturer specified tension. That triggered my idea to actually try calibration other way around.
What I did I reset both 100 and 101 to default 40mm and I took a scale and I made sure that both Y belts were on equal tension using luggage scale (similar to recommended on forums fish scale). Than I started to cut squares in MDF using 1/8 bit 40mm with 2mm depth and measuring them. They both as expected came up bit small. What I did than I took measuring tape and started tightening belts measuring length of screw sticking out of the x carve tension clips. I would measure square after every cut and keep adjusting belts accordingly. To my surprise I actually got 40mm square to be perfect with 40.00mm with repeatable results. Than I started to cutting 80mm squares and I managed to get X to be 80.00mm by adjusting screw by 1 spin at the time and I got y to 79.88mm This is way beyond precision I was expecting with my Monster Carve (remember my Y is 2.8 meters long).
I will try tomorrow some larger shapes but would anyone by so kind and try to verify if I’m on to something here?
Did I just get lucky or is there some merit to my logic ?
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Now that is very interesting… I don’t see any reason your logic would be flawed, you are removing spring from the belt, which is not wanted for precision… Also, balancing both belts on the Y exactly seems important, now that I think of it!
I like your idea and understand your reasoning, but I see a couple potential problems in it:
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$100 and $101 will vary slightly between steppers due to manufacturing.
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The belt manufacturer’s specified tension may be higher than the steppers can easily handle. The V-wheel bearings and rail aren’t frictionless, so applying downward force may increase the V-wheel friction to the point where the steppers have to apply a higher current. That would show up as a loss of steps, especially microsteps.
I’m really curious what your new belt tension is using this method, as well as the roundness of small circles. If you’re losing steps on both axis evenly, the circles would turn out more like diamonds. If you’re losing steps on only one axis, the circle would be oblong.
Keep us updated! 
Nothing new to report guys. I did few cuts and everything appears to work very well. Worth nothing is the fact that belts are much less tight than they were before I made this experiment. I will keep monitoring and report any issues.
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I just read where your Y is 2.8m long, I’d have to run through some calculations to see what my 3.5# at 1" is equivalent to for your length. What force has it been taking to lift them 1" so far?
If the belts loosened up during the test, you may want to make sure they didn’t slip past the belt clips at the end.
Robert,
Sorry I had no time to measure till tonight.
What I did is I moved both my x and y to 40 inches clip to first idler wheel, I believe this should give you readings similar to what 1 meter carve should have. Keep in mind I have 9mm belts, idlers and I made second layer of clips to fit wider belt and sandwiched both together (no chance anything is slipping)
I got following readings for you at 1"
Center of 40 inch:
Y 1.8 lb
X 1.6 lb
Whole length of belts from clip to idler:
Y 1.0 (106 inch)
X 1.2 (56 inch)
I’m still very happy with results. I cut some clothes hanger 6 feet tall and joints had perfect fit even with crappy 30$ Home Depot sanded ply.
I will see if I can find some time this week to make some precis alu cuts for tests.
