Strange Y Axis issue, A602 Prusa I3

I am relatively new to 3D printing and put together a new Prusa I3 a few weeks ago. To make a long story short first prints were really great and uniform.


This Issue:
When I put on the Y-axis belt I made a mistake it worked for the time being but I decided to get a new belt, also the threaded rods on the Y-axis frame were a bit too short.
I replaced both the rods and the belts and now I am printing Ovals instead of Circles


What I Tried:
Check everything to check it tight, bearings seem to be sliding well.
I used calipers to measure 120mm of travel and calibrated the steps to mm until it was a perfect as possible.


Testing:
Tried a test print again in the center of the bed. 10mm by 10mm by 3mm. The X is great about 10.03mm the Y is about 11mm and visually a rectangle not a square. The layer alignment is spot on so I don't think its slipping.
Then I double checked the Y axis travel still good over 120mm

Then I moved the bed 10mm at a time and measured each step on the Y axis I got a pattern like this (Rounded to whole numbers obviously), ran the test twice
10
10
10
10
10
10
11
9
10
10

Both times the 11mm anomaly happened at the same location which is roughly where I was printing.


Belt:
So I measured the new belt vs the old belt, over approximately 130mm the new belt has 1 extra tooth. The sprocket on the stepper is 16 tooth. I am not sure if its the new belt but I am going to see if I can manage to put the old belt back on tonight. Problem is I need a new belt. I don't if the printer came with some bizarre belt and sprocket pitch or the new belt is the culprit and not standard.


So what I am asking is, what should I try next, is the 1 tooth difference the big deal or might it be something else? If it is should I order new belts and sprockets so I am know they match? Thanks.

I went ahead and ordered new pulley's and belts, but if anyone has any other suggestions please let me know thanks.

The toothcount on the Pullys is critical, but not on the Belt itself.
Do you have different Pullys for X and Y? (If not maybe the Calibration of one Axis is off)
If you use the same Pullys for both axis, and the Calibration Values in the Firmware are identical
you should get nice round prints.

If this will get rid of the "11mm Anomaly" i don't know.

Hope that helps.

I wonder if you have a GT2 belt mismatched with a T2.5 pulley, or perhaps the other way around. If they are mismatched, they would eventually skip at some point during travel and cause what you're seeing.

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Same pulleys on both axis, in the firmware I ran the numbers and it should be a GT2 belt but there is definitely something off unless the new belt I bought is just bad. I switched back to the old belt and everything runs ok. When I get the new belt and pulleys I will try them with both belts because I will know for sure that the new pulleys are GT2.

Thanks your both of your in puts I appreciate it.

Lay the belts side by side and align them so the teeth match at one end, then look at them from the side to see if they are the same (space apart). If not then you have mismatched the belt type.

Quote
tmorris9
Lay the belts side by side and align them so the teeth match at one end, then look at them from the side to see if they are the same (space apart). If not then you have mismatched the belt type.

You can also put them together with the teeth on the inside. First the teeth might fit into each other, but eventually one might pop out. If the belts are the same, you should be able to fit them into each others teeth.

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