Hot end nightmare

I really hope someone can help me here, ive been trying to fix this issue for almost a week now with no luck whatsoever. Everytime i try to print the left vertext foot of a reprappro mendel the plastic ends up sticking to the hot end at some point and the print gets dragged about the glass bed and ruined. Ive tried absolutely everything i can think of, ive cleaned the hotend to make sure there was no plastic left that may have been catching on to the print, ive tried a variety of different temperatures, ive tweaked my retraction settings, my z offset, used different methods of getting the print to stick to the bed better (which wasnt an issue at all in the first place but i thought id see if it helped). Its not even always the first layer it happens with, a few times ive monitored the print until it was at least 20 layers up, i then left the room and when i came back 5 minutes later it had happened again. One thing that ive noticed is that when the extruder turns the large gear to drive the hobbed bolt it seems to be pushing the hobbed bolt up and out of its housing, which i think may be causing an uneven amount of platic to be extruded, when this happens the small strands of plastic may be catching on to either the hot end or the plastic thats then begun to extrude normaly again, but no matter what ive tried i cant get the hobbed bolt to stay in place. Anyway i dont know what to try next so if someone could help me id be overwhelmed with gratitude.

REading the first sentence I thought the Z steps would be too small in relation to the nozzle so the extruded plastic smears along the nozzle and finally sticks to it....

but as you mentioned the extruder.... so foar I understood : do you have radial play on your extruder axis? If the hobbed bolt is in the bearing and the paearing has play you could fis it with some epoxy glue to fill the gap between the outher ring and the printed fitting...

There is quite a bit of radial play yes, I don't have any epoxy glue but I put a very small amount of tissue paper untie small gap there was between the bearing and the printed housing and it seems to be working an absolute treat, thank you very very much

It sounds like you're on the right track. I would suspect overextrusion causes the top of your layers to get bumps that the hot end catches on the next layer, which dislodges the print. It could also be cooling or adhesion issues. Insufficient cooling with PLA will cause previous layers to curl upwards. Insufficient adheson will cause ABS to warp upwards.

But judging by the issue you describe with the hobbed bolt moving, I'd say that is the main culprit, causing uneven/excessive extrusion.

Are you using a Wade's style extruder (sounds like one)?
If so, the bolt is held in place by two ball bearings. If mounted correctly it shouldn't be able to move either vertically or horizontally.

How tight is the nut on the bolt?
I tighten mine up until there is no axial play in the assembly, and maybe just loosen it a fraction of a turn so the gear/bolt turns easily. Use a nyloc nut so it won't come loose (I've found locking with two regular nuts less reliable). I shortened my bolt so I only have a few turns past where the nyloc grips. Threading a nyloc on a long bolt gets old very quickly...

If the bolt still moves when the nut is tight, there is something wrong with the bearing seats. Check them for warp or other distortion. You may be able to fix it with some filler (epoxy) unitl you can print a new extruder if that is the case.

Edit: I realize this looks silly now, I should learn to reload before i post

/Andreas

Edited 1 time(s). Last edit at 09/22/2013 05:09AM by anwe79.