random motor movement / extruder help

Hello,
I have been using a Prusa i3 for almost a year now, and I have noticed that sometimes during a print, either the X or Y will randomly move towards its home position (sometimes all the way to home, and sometimes not), and then resume printing again. I didn't really mind, because it almost always went back to the right spot and continued printing without problems.

However, I just recently noticed that the extruder is doing that now. And more frequently. It will run backwards (retract) for several seconds. It's enough to cause problems with the print. If it goes too far, the filament actually gets stuck on the entry of the drive rollers and will not start feeding. So If I don't catch it, the print is ruined. Also, it just recently started to stop extruding shortly after the print starts. When this happens, I can manually push the filament through, but it is much harder (so the drive rollers are slipping). When I pull the filament out, it seems all 'gooey'.

So I simulated what I think the problem is. I manually push the filament through until I get a nice flow out of the nozzle. Then I pull it out (not all the way, just 10 to 15 mm or so), then push it back in, and it is noticeably tight, and hard to push through. I think the motor retracts, (pulling melted filament up with it) then tries to extrude again, and now it's all tight because of all the melted plastic in the 'cold end'.

I hope this all makes since. Is there a way to get it to stop randomly retracing so much? Maybe a newer version of Marlin I can reload to the RAMPS, or a newer version of software to load to the Arduino? Any ideas at all?

Thanks,
Scott

If you print from SD card get a new one, if via USB be sure your computer is set to never sleep and no screen saver is active or other programs are running in background mode, try a different slicer and pay attention in which layer happens and open the gcode and see if anything abnormal happens.

I am using an SD card. I have checked the g code before and didn't see anything. And if I reprint the same file, it happens at different time, if it even happens again. It seems completely random. I assumed that since it wasn't in the g code, then the slicer wasn't the issue. Is this a safe assumption?

I will try a new SD card first and see if that helps.

Thanks for the advice,

I think it's a safe bet that it should not be doing that. It's hard to imagine what on earth could cause it to happen with out the prints failing in a catastrophic way every time, so I don't know what to suggest other than replacing the electronics piece by piece until the demons have been exorcised.

If all of the above fails, flash a newer version of marlin to the mega and if continue replace the mega board.

Quote
koenejet
Maybe a newer version of Marlin I can reload to the RAMPS, or a newer version of software to load to the Arduino? Any ideas at all?

Firstly, to clarify; Marlin *is* the software loaded to the Arduino. There is no software/firmware on the RAMPS... RAMPS is purely hardware. So what you're suggesting is reloading Marlin onto the Arduino.

Secondly, when things go crazy, it's probably the brain at fault. When only one limb misbehaves, it's probably that limb. So I think possibly it is a firmware problem. However, it is unusual for a software problem to get worse; typically it either works properly all the time, or it doesn't work, all of the time. Things changing is usually a mechanical/physical issue. The first thing I'd look at in your case would be the power supply... if that is weak, it may work OK for a while until all the heaters and steppers are on at once, overloading it. Then weird things can happen: if the CPU doesn't get enough power, it may go slightly wonky for a short time, or if one or other stepper doesn't get enough power it may skip.

That's what I originally thought (about the RAMPS not having any software/firmware loaded), but I thought I read recently somewhere that it did. Oh well, makes more since now. I will try a new SD card first and let everyone know how it goes. After that I think I will replace the arduino and the RAMPS and load the latest and greatest software/firmware. I want to stay away from the clones. The 'arduino' that's on it now is actually a clone. But I'm not sure the best place to buy the best RAMPS. Any suggestions?

At the moment, the SD card being an issue makes sense to me. And it's the easiest thing to try first.

Thanks again,

So I replaced the SD card. I didn't notice anymore random movements, but the extruder still jams.

I started a new post because I don't think my original post is the issue now. The new post is just about e3d v6 jamming.

Somehow melted plastic is oozing up into the cold end jamming it up. And I have no idea how this could happen or how to fix it.