Motors not running smoothly
April 11, 2014 02:35PM
Hi everyone.

I have just finished building my first Prusa Mendel (i2) and finally want to go ahead and try my first print.
Unfortunately, my motors think otherwise. I am using the RAMPS 1.4 board (with the Arduino MEGA) and have uploaded the latest version of Marlin.
So after everything working nicely up to this point, whenever I try to move my x and y motors through pronterface (or the LCD screen) the motors seem to work fairly ok at 1mm increments (although somewhat with spasms), but at 10mm increments they move again the same (as the 1mm increments) or not at all.
I have adjusted the pots as best as I can to achieve this but have not reached to a satisfactory conclusion.

Can anyone help out with what might be the issue and what should I look for?

thanks in advance.


--- so long and thanks for all the fish...---
Re: Motors not running smoothly
April 11, 2014 08:15PM
Have you put the 3 jumpers (for microstepping) under each Pololu chip carrier? And what voltage have you set them to?

Waitaki 3D Printer
Re: Motors not running smoothly
April 13, 2014 06:30AM
Hi waitaki,

I have not added the jumpers! I totally missed that while connecting the electronics.
I guess this must be the issue. I will try them with the jumpers (hoping that I have not done much damage to the motors so far) and get back to you.
About the voltage, that you are asking, I am not sure. My RAMPS is connected to 12V if that is what you are asking..
Re: Motors not running smoothly
April 13, 2014 07:02AM
No, not the 12v rail. On the pololu chip board is a tiny potentiometer to adjust the voltage to the motors - generally, these are set to 0.4v or so on all of them. You put 1 meter lead on the negative terminal of the 12v power connector and the other lead on the pot' itself (the pot is a shortcut to the v-ref pin). Adjust the pot in small increments to achieve the target voltage.

Waitaki 3D Printer
Re: Motors not running smoothly
April 14, 2014 06:27PM

Also, be careful about the step per millimeters you set in the firmware. If not well configured, you might ask your steppers to turn much faster than then can; then they will vibrate or turn randomly in any direction. Without the jumpers, you don't have micro-stepping, the printer will work but the steps per millimeter setting should be 16 times smaller, you get the same issue: motor turn 16 times faster than what they are supposed to.

There is a handy tool in order to calculate this setting for each axis: []
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