Trouble with clogging

Hey guys,

New here but I've been looking all over and done a bunch of reading. To give you an idea I've got a chinese prusa i3 with an acrylic frame (strangely enough I don't have any stability issues I've heard horror stories about, this one has some sort of support on the front and back portions for the y axis rods). My issues come from the extruder. It printed for days without issues at .1mm ~60mm/s (maybe 50mm, I've played so much trying to get this working that I can't remember exactly what it was at) and the quality was great, then it clogged suddenly and I cleaned it using a propane torch and compressed air to blow out the molten PLA. As best I can tell is this is clogging in the throat rather than the nozzle and I was wondering if anyone has any advice, this doesn't have a threaded cold end so the throat is only held in with a set screw but there is a heatsink / fan set up for the cold end. This whole extruder assembly was pre-assembled when it arrived so I am not 100% sure if it had a PTFE tube inside the throat but I've read sooooo many varying opinions or "facts" that conflict as to whether or not PTFE lining is necessary for PLA on these styles extruders.

I've also been having issues figuring out what to call this extruder. As best I can tell it looks like the QU-BD type extruders but I've also seen the MK7 and MK8 look similar is there a name for this style extruder to look for so that I can do some more searching for information as thats kind of my most problematic thing currently.

The model I have is the HIC Tech prusa i3 on amazon, its definitely a cheap kit model but like I said while I had it working it printed amazing quality (to me and compared to a lot of pictures I seen so I can't complain) but it clogged and I've been unable to get it to print since. I believe I'm getting what I've read as Heat Creep where the PLA actually gets jammed up in the throat and not the nozzle.

I've ordered a replacement extruder setup, including throat with PTFE liner, new aluminum heat block, and new nozzle. I've also decided to see if it is heat creep whether or not those cheap heatsink washers would suffice to pull heat away and I do intend to modify the fan on the heatsink for the coldend to blow air onto the throat.

I don't have pictures currently (not home with my prints) but I was wondering if someone with more experience might have some insight or feelings towards if I'm onto the right track and could possibly guide me to knowing what type of extruder set up this is exactly as I'm kind of shooting in the dark hoping I've got my information straight.

EDIT: So I was just thinking I suppose I should have put in here what I had done to get to the point I am. I was printing at ~200C with this PLA just fine for days, like I said .1mm layer height and it was working great. Once it clogged I cleared it out and would go about trying to start the print over again. The initial layer height is .3mm and 200% (in cura) which would go down no problem, once it got to the 2nd layer it'd instantly become clogged and I could not figure out why. I've played with a number of settings from temperature to dropping it back down to 100% and .1mm initial layer height and got nothing. One thing I will note is that if I set the temperature to anywhere from 185 to 200mm I was able to manually extrude the PLA using pronterface. It extrudes exactly 100mm when I tell it to and the z height calibration was fine previously, should still be as I've gone through and made sure everything is level and the steps/mm are what they were previously. I'm basically to the point where I think the throat lacking PTFE liner is the problem causing heat creep which I'm going to be addressing but I just wanted some other peoples thoughts on the situation. My only real curiosity I can't figure out is why it seems to print fine manually doing heat to 185 or 200 (works at any range really) and extruding 100mm but as soon as I press print it doesnt, which has me questioning if somehow theres a setting in cura I've completely overlooked but I can't really think of anything that would do this. Its no longer laying down the initial layer let alone the 2nd or beyond.

Thanks.

Edited 1 time(s). Last edit at 07/01/2015 03:07AM by Humantelope.

You might want to try calibrating you Z axis again just to be sure that your moving far enough during layer changes. So for clogging repeats there may be something snagging up or maybe its trying to extrude too much. I would try checking the extruder calibration with a larger amount as well. Mark off two 100mm sections and make sure it comes out fairly close to your lines.

I have had the little brass tip of the nozzle rub on the print and cause it to reduce the nozzle diameter so I check them each time I clean them with the nozzle drill bit kit from ebay to be sure.

Edited 1 time(s). Last edit at 07/01/2015 12:12PM by AquaticsLive.

Until I switched to this $20.00 finned hotend I mounted a 40x40x20mm fan to a bracket and used the hotend attachment screws to mount it. It blew on the filament where it enters the plastic hole. This cooled the filament and eliminated heat rise and jamming. I also just doubled the size of the bearing that presses against the Hob Gear because the end of the arm was rubbing on the Hob Gear and let the filament grind and get pushed out sideways. I also added a piece of aluminum tubing through the arm to keep the filament straight as it approched the Hob Gear. Adding the fan allowed me to double my speeds. The finned hotend is definately the best solution but you will need to make an adjustable Z Endstop switch holder because the new hotend is longer. I have an STL. file of the Z endstop holder and will attach it. It's to long and needs to be shortened. I had it long but relocated it to the original position. I have many STL's for upgraded parts for this cool little printer. Good luck. Brian

Awesome thanks for both your responses. I've gone and checked the Z axis and its definitely calibrated properly still, moves 10mm when I tell it to and so on. In case I did have the hot end too close to the glass bed I've calibrated that to be two paper thicknesses off (as opposed to the one I was using ) I've got the replacement assembly in hand now but I wont be able to do any testing until tomorrow most likely. As far as the finned assembly with fan on it thanks! looks like I could almost certainly make that work or make something similar to it. appreciate the idea and knowledge. My fear with going with the finned extruders like the jhead or e3d models was finding out how to mount them or what to do w/ my z axis because its current location it'd never "bottom" out and hit it, thanks for the endstop holder!