How to fix non round shapes?

that has to do directly with the stepper motors. One of two things I can think of wither the power is too low or too high that drives it or the steps per mm need to be adjusted.

Try printing the 15 mm cube make it solid and then some how mark which side is X and which is Y and then measure them they should be 15.0mm or very very close.

This will help in getting the right numbers if this is the problem


The power issues is a bit more complex the first things to do is to feel the motors they should be just above room temp or slightly warm.


A very inaccurate test:
Too much power and they get hot and this is not a good thing.
If they are just barely warm then the power is probably set correctly.

More accurate is to measure the voltage of the controllers which is a process in itself.

If a motor gets to how it skip steps and if it not powered enough it may not be able to hold position accurately. Both situations can cause slippage to occur, but due to the fact the image does not show jumps but a steady print (edges don't appear to be angled) I think it may be the step size.

 

by looking a that print I would guess it is the steps per mm the reason I say so is this you can obviously seeextra linear motion along x by that straight section but the y is also affected or else the remaining parts would be more circular along the y axis but there are being stretched out as well.

This is what I would first upload some pics of your settings from repetier so we can see them then using teh following gcode to print this cube using gcode directly bypasses you repetier settings but not your firmware settings it seems to smooth to be a motor voltage issue but check that at some point as well.

After the cube is done mark the sides so you can remember the axis and then measure it and let us know what the measurements are that is a firmware setting so if it is off then you have to get a copy of the firmware from the forum and make the change and upload it to the Ramps card.

I actually put three in there 2 versions of the cube one from cura and one from repetier and the 5 step calibrate pyramid

 

Possible, although I would think it would be less consistent.
Still, if it is loose tighten it up. That is an easy fix (if it works).

 

Mark is right a loose belt would be seen by more jumps but what what you see is a smooth transition I really think it is the stepper motor step size

 

I would try the step size first it is easy and it is something you will probably have to learn how to do sometime

The adjustment for the pololu is not that hard to do but it helps if you have a third hand sometimes. The contact points you have to adjust and make measurements from are on the smaller side and to me it was a bit of a pain but then my thumb pretty much covers the whole pololu board LOL not the most dainty, you could find it much easier.

Check with Mike he may be able to walk you through it if has the time he's pretty sharp. His links are always good.

 

Get a 2 or three layer circle pattern to play with and you can adjust/test-print/adjust easier.

 

well that is an easy check as the non circular is the x axis and not the y so that set screw is easily available