Why are my Circles still ovals? Ive ruled out backlash.

Hey guys! I have a prusa mendel running marlin on a ramps 1.4. Im using gt2 belts with 20 tooth pulleys on xl belt on Y with an 11 tooth pulley. There is no measureable backlash on x or y when measured with a .001" indicator.

my circles are still coming out as ovals though and its driving me nuts. The x axis seems to be the issue though, the long axis of the ellipse traverses the y axis. I am beginning to think that this is due to my acceleration values. I am using the default values in Marlin, but I am using 1500 on profiles and 3000 on infill in slic3r.

Do you guys have any ideas?

Thanks

here are some examples of what I mean.

First - what happens when you print something square? The issue could easily be X / Y calibration values.

If it's acceleration, printing slowly should eliminate the issue. That's pretty easy to do as a debug tool.

It doesn't matter which axis is longer, but which axis is incorrect. You have an expected diameter, which one is correct. Your error found be on the y axis.

Another thing to consider is whether or not you have your micro stepping jumpers properly installed.

It looks to be a calibration issue. This is the 25mm hollow calibration cube. As you can see the x axis is pretty much dead on, or as close as I trust digital calipers to measure, and y is off quite a bit. I swore I had this all straightened out. Ill mess with my step settings tonight and get back to you guys.

Thanks alot!

You can print a lower, but wider cube to do this sort of calibration. Printing a 5 or 10 mm tall cube goes a lot faster than one that's 20 or 30 mm tall.... One that is 50 x 50 or 100 x 100 helps take out the "rough edge" errors. It may also give you more confidance in your calipers.

Hey Guys. Looks like it was a calibration issue. I swear everytime I use the reprap calculator it gives me a different value haha. But its pretty dead on now. Within .2-.3mm which Im pretty happy with on a prusa. Thanks for the help everyone. I appreciate it!