I've been having problems with my extruder jamming up halfway through a print.

I’ve been having problems with my extruder jamming up halfway through a print. When I pull the filament out to clear it, this is what it looks like. 1.75mm PLA extruding at 200C, with a 60mm fan mounted and going full blast. Thoughts?

200 is quite a lot for PLA. I extrude at 175. Also put a little spoon over the filament to automagically clen it from dust. That was the trick that made my jamming go away.

So is it bending after the feed motor before the nozzle? If so I would add a support tube to the nozzle. @Jan_Wildeboer also has a point about keeping the filament clean. Have you checked the nozzle for debris?

@David_H , yep, after the hobbed bolt, before the nozzle. Any suggestions for what material to use as a support tube? I’m using a Printrbot Jr. with a 1.75mm Ubis hot end. Haven’t checked the nozzle yet, will do that tonight. Is is safe to clean the nozzle with rubbing alcohol?

Something similar to this should do the trick: http://store.makerbot.com/machined-core-tube-for-mk6-1-75-mm.html

I am not sure about cleaning the nozzle, I haven’t used PLA at this time. @Jan_Wildeboer or @Nils_Hitze might know.

Anyone from @Printrbot know if @David_H 's suggestion would do the trick? I’m willing to spend the $15, but I don’t want to be sitting with a useless piece of $15 plastic if it for sure won’t work.

200C is a lot for PLA, I’d normally not expect this to cause that, but looking at the resulting filament, it looks like your cool end is very short. You need to get the temps down.

I had two reasons for something similar

  1. The extruder got to warm and the filament became soft
  2. The distance between the hobbed bolt and the entry to the nozzle was to long.

@Bracken_Dawson and @Bjorn_Marl , I guess I was looking at this the wrong way: I had been extruding at 195 when this happened initially, bumped it up to 200C because I thought the fan was cooling the nozzle down too much and causing it to jam. Never considered it was actually making the filament too soft and further aggravating the issue.

How I clean my nozzle: Heat up from cold to 70 degrees. After it has reached 70, I pull out the filament. Dead simple. That typically catches everything. You could clean with some alcohol afterwards but this is typically enough.

So your conclusion? That you were just running a little hot?

@Brook_Drumm , I’ll need to test tonight to confirm, at work right now. While I have you here, do you think that Makerbot piece would also help? http://store.makerbot.com/machined-core-tube-for-mk6-1-75-mm.html

I run PLA from 190 to 210 it depends on the purity of the material. I put a small piece of foam before the filament meets the extruded. I would make sure the nozzle is clean and there isn’t anything force the filament to bend. Make sure that everything is aligned misalignment can cause the filament not to flow properly.

@John_Schneider The makerbot piece is not going to work for you. It already has a ptfe liner on the cold side. Two things Ive noticed is that the laser cut extruder does seem to have a little too much space after the hobbed bolt so there is room for the filament to buckle. Also the new cartridge heater is mounted vertically which increases the height of the melt chamber. (Ideally the hot zone is as small as possible to sneak up on the unsuspecting filament.) Im curious to see how these changes affect things but 190C for PLA is too hot… try lowering this to 185 and then 5 degrees after that (Ive seen as low as 165 sometimes work) and see what happens. I suspect the heat is rising up the hot end and is softening the PLA causing the jam.

Thanks @Brian_Evans , you just saved me $15 + shipping :slight_smile: I agree about the space on the laser cut extruder, and after taking a closer look at it, my hobbed bolt is about 1-2mm off center from it. It’s impossible for me to get it more centered - I physically cannot get the bolt to be any further over without cutting one of the laser cut layers in the extruder.

@John_Schneider check for something comparable at McMaster Carr supply. Every type of high temp high strength plastics available. Make your own and maybe something there for the nozzle. Being a machinist…I make my own parts. A lot cheaper than a manufactured part. Remember…we’re designer/engineers. We can make and fix anything!

@John_Schneider I had to add 2 washers between the large gear and the 608zz bearing to get the hobbed teeth to line up with extruder. Those were not in the kit and had to be picked up along with a bunch of other missing hardware. Although Im using different gears than the stock cast gears so they might have different spacing. If the path from the hobbed teeth to the hole in the cold side of the extruder is not perfectly lined up then that will create a kink in the filament and could cause some of the issue. I think its a combination of things but most likely poor alignment and being too hot.

@Brian_Evans , I’m misaligned in the opposite direction. I’d have to somehow remove something to make mine align. And you’re right, it’s definitely not just one thing, but multiple things that must be causing the issue.

Ok, this also appears to be filament-dependent. That blue stuff is Matterhackers, and even when i dropped the temp down to 185 from 205, it still would get jammed up horribly about halfway through my second layer. Switched back to the natural filament that came with my Printrbot Jr, and that’s working just fine without jamming.

@John_Schneider IC now. I didnt even look at the black cast gear. That sucks about the Matter Hackers filament. I have some sitting in a shopping cart at the moment that Ive been thinking about. You might even try dropping the temp to 175 and see what happens. As I was putting one of these together I mounted the hotend to the extruder and pointed the tip at a bright light to see that the nozzle lined up with the hobbed teeth. Its kinda hard for you to do that now without cleaning out the tip. Not sure what else to say but go back over the extruder and make sure everything is supper tight and lined up and keep experimenting.