Printer keeps crashing

Hey there, I'm not sure where my problem lies so I'm not quite sure where to post it but here's what I've got:

Okay so I've got a Prusa all built and it communicates just fine with Pronterface. However, it keeps crashing. When I tell it to move up and down in the z, it moves to where it needs to be and then the motors turn off until their next instruction. When I tell it to extrude or move in the x or y, the motors move but then stay on once they're still again. When I say they're "on" I just mean they're stationary but still making a mechanical whining noise as if they're moving. If two are more motors are in this state, the voltage from my power supply drops from 12v to about 6v and the gen6 electronics turn off. Consequently, Pronterface is no longer able to communicate with it. Is the problem with Pronterface, my power supply, or something else? Thanks in advance and let me know if there's any other helpful info I can post.

How big is the power supply? Is it an old PSU hack mod? If so, do you have a dummy load on the 5v rail?

---

Josh

//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//Prusa / RAMPS_1.4 & ATMega_2560 / Slic3r > Pronterface > Marlin / Luck
//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

The Z motors generally turn off between instructions (that can be set in firmmware) the X & Y stay on. If your supply drops to 6 V the I suspect that your pwer supply can not supply the current required. If you are going to use a heated bed you will need a supply to give you about 15 A.

I used a PC power supply 550W with a 5 ohm restistor on the 5 V rail

Also check that you do not have too much current on your drives.

Yep. It was the power supply. I was using one I borrowed from a friend that I thought had enough power. I ended up making one out of an old desktop and it works like a charm. Thanks for the help!

Okay but now I'm having problems extruding. The extruded filament curls up towards the nozzle. I posted a video of it here:
[vimeo.com]
Should I be concerned with the fact that a small bit of filament comes out after the extruder motor has stopped turning?

Extruded filament does tend to curl up and stick to the nozzle, until the weight of the extruded filament pulls it down. It shouldn't really matter, because it won't do it when actually printing. But perhaps yours is doing it a little more than normal; you might want to check your nozzle isn't partially blocked.

The filament coming out after extruding could be a couple of things. Using too high a temperature is the most common. Has your PLA been sitting around for a while? PLA is hygroscopic, and absorbs moisture if kept in a humid environment. When heated up, the moisture turns to steam and expands, messing up your calibration. It can be dried out easily enough. I have noticed that if you have an extruder with a large melt chamber, you tend to get more oozing.