Problems with Prusa Mendel i2 electronics [videos included]

Hi All,

I've just finished assembling my Prusa Mendel I2, but the stepper motors are acting weird!

At first, when I fire it up, all seems fine and I can move the different stepper motors with Pronterface.
But then when I've played around with it for a little while, the motors begins to "lag".

Actually I don't know how to describe it, so I recorded it instead.

Here I am trying to extrude. As you'll see the first 40mm went fint, the second 40mm almost fine and the third time it lags a lot.
[www.youtube.com]

Here I've just pushed to X-home button, and as you see it reacts fine half the way, but then it begins to lag:
[www.youtube.com]

Here it is trying to actually print, and it still does that "lagging" thing:
[www.youtube.com]

I am really at the bare bottom here, so any help at all would be very much appreciated!!

Edited 1 time(s). Last edit at 09/11/2014 12:51PM by Texton.

Sounds like your drivers are over heating. Do you have heatsinks and active cooling on you board?

Sounds possible,

I use a RAMPS board: [www.dropbox.com]

But as you see - without cooling. Do you think that it is that necessary?

Additionally, the Z-axis (with two motors) is the only axis that doesn't lag.

You dont have heatsinks on your stepper drivers and you dont have a fan on them...
Im guessing overheating.

Edited 1 time(s). Last edit at 09/11/2014 01:59PM by Floyd.

It makes sense!

Do you think a PC-fan would do the job, or are heatsinks a must?

What power supply are you using and what is it's max amperage on the 12v rail? Are these issues present from start-up or do they happen after a few minutes of testing/printing?

I have no cooling on my RAMPS and have completed a 5hr print without any issue. Yes, I will be adding a fan to it. Actually printing out the brackets for a 80mm at the moment. MOAB

It starts almost immediately after startup. ~100mm on the extruder for example, then it starts. The power-supply is 17A, and it happens even then I shutdown the heated bed and nozzle (which should be the primary power consumers?).

I doubt it's heat related then. Have you properly adjusted the current for the steppers? Overcurrent will cause similar issues. What type of stepper drivers are you using?

Edit- If you have a graphic controller connected, try move the axis with that and leave the USB disconnected.

Edited 1 time(s). Last edit at 09/12/2014 05:24AM by multitronic.