Print issues, Please help

I just started a 11 hour print for the first time today with my Prusa i3, I started it just before I went to work. I came back home to the print mostly complete but the results have some strange issues I cannot put my finger on. I have going at it for months now trying to get the best quality prints I can out of this sunhokey prusa. The first issue I have is this strange little towers and strings all of the print, the second one is for some reason mid way through the print the print shifted completely, I cant be certain someone did not come in my room and bump it or do something but it seems really odd that it would do this on its own. Any help would be great. If you look at the second picture the columns are suppose to be straight but there is an offset.

Edited 1 time(s). Last edit at 06/07/2015 01:54AM by tythebuilder.

It looks, like your retraction settings aren´t sufficient. Fromt the pictures it seems to be some j-head /E3D hotend. I don´t know the best retraction settings for them..

I also found, that the "G0"-speed that moves the head without extruding should be as fast as possible.
It´s like working with a glue gun: If you want to avoid the glue to plaster strings all over the place, you have to make a fast move to rip the string apart. ( max. speed and acceleration are important here)

The skipping stepper can be a result of too much filament, where it shouldn´t be ( towers from retraction failure) and the nozzle running into such an obstacle.

-Olaf

Other things that may cause the little towers: lifting the nozzle before a move, high temperature.

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o_lampe
The skipping stepper can be a result of too much filament, where it shouldn´t be ( towers from retraction failure) and the nozzle running into such an obstacle.

True, it may be also caused by a slight warp of the piece or by some deflection of the structure during fast moves if the printer is not very robust. I usually avoid this problem by slowing moves and/or lifting the nozzle before a move, which is exactly what one should not do to avoid those little towers.

@○cristioan,
you don´t lift the nozzle at all? I´ve checked my gcode, and it retracts the extruder, then lifts z for 0.075mm.
You say, this lift could cause those towers? I´ll try next time to keep z down and see...
-Olaf

Quote
o_lampe
@○cristioan,
you don´t lift the nozzle at all? I´ve checked my gcode, and it retracts the extruder, then lifts z for 0.075mm.
You say, this lift could cause those towers? I´ll try next time to keep z down and see...
-Olaf

I do lift the nozzle and considerably more than you do, because my printer is not very solid nor very orthogonal. Lifting Z adds some delay before the move, and any such delay will increase the oozing, if present. However the delay introduced by lifting 0.075mm may be negligible.

I never had an oozing nozzle, because I retract fast. That causes the molten filament to get sucked back into the nozzle. ( Well at least in my imagination )
-Olaf

Quote
o_lampe
I never had an oozing nozzle, because I retract fast. That causes the molten filament to get sucked back into the nozzle. ( Well at least in my imagination )
-Olaf

It should work that way indeed. I guess you are not only retracting fast: after retracting and lifting, you are doing fast moves and you print at reasonably low temperatures.

I usually have a lot of ooze because I print at high temperature to get pieces as solid as possible with the cheap ESUN filaments I use.

I just printed the same thing again today, this time no shift in the peace (because I changed to a different fan duct) but the little towers are still everywhere >< I changed my retraction amount to 2mm instead of one and it retracts at 30mm/s.

I'm printing at .2 layer height at 50mm/s and using bowden extruder

In my opinion 2mm with a Bowden is not enough, try maybe 4 or 5.

I recently bumped my retraction setting from 2mm to 3mm and then to 3.2mm, very happy with the improvements. However I am running a Rostock Mini delta based printer, so the retraction settings might need to be different. Running 80mm/sec on the speed if that helps.

I think the retraction issue has gotten better with 4mm and quicker travel speed, But I think I found the main reason my printer is not printing too well. There is a fan that cools the nozzle heat sink, it has be only half on because if I turn it on and have my other fan that cools the print on then the nozzle wont reach 200 degrees. But if i dont cool my print heat the print underneath does not harden fully and gets pushed around by the print head hence why I have a lot of trouble printing smaller things, they always seem to just blob up. Would it be best for me to get a new printhead, maybe e3d. but even if i did i would still need to find a way to cool the print enough so it hardens but not too much that the print head cant heat up :/

Does the head fan have a duct, only allowing it to cool the head? If not, make one . . . then it shouldn't affect warmup time or the part . . .

- Tim

Here is the way it is setup now, I have a fan with a small ducts facing the bottom on the head right on the piece and a 40mm fan blowing on the heatsink. when the heat sink fan is on by itself the hot end can head up normally, but when i have both on it slowly drops fro 200 to around 180. I need both fans on so the layers dont get to hot, I feel like the big circular heat acts like a heater and does not let the layers cool ><

Are you using your heated bed when printing PLA? It might be set to high and is keeping the PLA from cooling appropriately. Perhaps try turning off the heated bed and the ducted fan while printing, with just the fan pointed at the fins of the heat sink turned on (full power ideally).

If you still think the print needs additional cooling, you can try a room fan pointed at the printer (not to strong) just to keep blow away any excess heat.

I have never used a heated bed myself, but I am hoping be taking it out of the equation, you can start feeding the filament successfully. Then you can slowly add the heated bed and the print cooling fan back in.

You might also consider printing duct work for the hot end fan at some point to focus it on the fins.

How much of the air from that duct hits the hot end? It should just cool the part, not the heater block . . . I can't tell, since the open side of the duct is not visible. You might also try slowing that fan down . . .

- Tim

There is around a 3mm slit on the inside that lets air out, if i slow down the fan I don't get enough cooling. I don't have enough as it is, when I print small thinks like a bolt the side without the fan tends to sag a bit. I've tried using this [www.thingiverse.com] with some luck but my fan does not have enough power to really get air all the way around. at this point I feel like its a crappy print head to begin with.

There is no insulation around the hotend? I can only see kapton tape.
Try to put a piece of cardboard between the orange fan duct and the hotend to guide the air away from the hotend.

You can print small pieces with slow print-speed and lower filament temp. Also you have to set the minimum time for a complete layer to 10-20 sec. ( Cura has such setting )
When I try to print small things, I print many of them to extend the time for cooling. A few part may fail anyway, so you´ll have plenty of spares...

If your nozzle touches the parts and even push them from the table, something fundamental is wrong with your setup. No fan in the world will keep the pieces on the bed then...
-Olaf