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Problem with HotEnd?

Posted by academicdave 
Problem with HotEnd?
March 04, 2014 02:20PM
After a couple of weeks of successful printing, really cranking out stuff all the time I have developed a problem that I think is related to the Hotend, and not sure if I need to take apart the extruder and clean it.

When printing after the first few layers the plastic stops flowing from the hotend. I have to stop the print and then retract the plastic, wherein the end is totally mangled, it looks like to me that the bolt is pushing but not enough plastic gets out, so that a jam occurs. If I clear it out and then load new plastic in, it will work, but the plastic coming out isn't smooth. By this I mean that if I extrude at anything but the slowest speeds the plastic coming out vibrates/wobbles back and forth and when you look at it isn't a round shape, but rather groved, it has tiny ridges up and down the plastic. I can try and take a picture of it, but I don't think it will come out. I am guessing (and just guessing here) that something is preventing the plastic from flowing smoothly out of the hotend. Thoughts?
Re: Problem with HotEnd?
March 04, 2014 02:43PM
Yes it sounds like something is blocking the nozzle. If it is PLA you should be able to pull it out at 80C and bring any contaminants with it.

Re: Problem with HotEnd?
March 04, 2014 02:45PM

You mean heat it to 80C and put filament in then pull it back out? (Saw this method discussed elsewhere, just making sure this is what you mean)
It's PLA haven't been willing to brave ABS yet, still trying to get the PLA down before leveling up to ABS.
Re: Problem with HotEnd?
March 04, 2014 03:06PM
Yep that's what he means. I do it manually by lowering the carriage and then turning off the motors so I can turn the big gear to reverse the filament. I also set it to 85C if the filament feels really stuck.
Re: Problem with HotEnd?
March 04, 2014 03:13PM
Thanks will give a try
Re: Problem with HotEnd?
March 04, 2014 03:34PM
Just a tip: If there's no filament in the extruder at this point, you should load the extruder with some filament first and heat it to the extrusion temperature and let it cool to 80C from there. Otherwise I don't think this trick will work. But correct me if I'm wrong here though.

Edited 3 time(s). Last edit at 03/04/2014 04:14PM by Nilez.
Re: Problem with HotEnd?
March 04, 2014 08:21PM
Yes repeat pushing it in at extrusion temp and then cooling to just above Tg and pulling it out. At 80C it is like rubber, so pulling it will stretch it so it shrinks away from the walls and then comes out in one piece.

It doesn't work as well with ABS because that is more like chewing gum above Tg, but it can still pull out crap.

Re: Problem with HotEnd?
March 04, 2014 09:42PM
Well, that didn't work, spent probably two hours repeating the above technique a dozen times or so and to no avail. What else could I try another technique? or am I looking at needing a new hotend?

It is clear to me that the flow isn't even, and the gear will skip a few times.

Edited 1 time(s). Last edit at 03/04/2014 09:58PM by academicdave.
Re: Problem with HotEnd?
March 05, 2014 03:49AM
Seems like there must be something very solid jammed in it then.

I use a long 3mm drill to rake out plastic while the hot end is hot. I remove it from the extruder and hold the cold end in one hand and twist the drill with my fingers.

I unblock nozzles with a 0.4mm drill, also while hot, again twisting by hand with a pin vice. It is easy to break the drill and leave a bit in the nozzle. You then yet two spiral steams of plastic!

Don't use a drill on a cold hot end because PLA is very hard so it tends to make the drill wander into the brass or the PTFE liner and damage it.

Re: Problem with HotEnd?
March 05, 2014 10:47PM
I tried both of the above steps and it made things much better, but the end still isn't working perfect, it's like maybe 95% or so. I feel like maybe I actually damaged it trying to clean it. Suggestions at this point? Is there a place I can buy a replacement hotend, the same one that comes in the kit?
Re: Problem with HotEnd?
March 06, 2014 01:48AM
I had similar problems and got an E3D hotend which I've found very reliable. It is a bit longer so you lose 2cm of Z height for printing. The nozzle is quite easy to remove and several sizes are available for hot swapping.
[e3d-online.com] .
Re: Problem with HotEnd?
March 06, 2014 08:04AM
Can you just put in the E3D hotened? Is the only disadvantage losing 2cm of height? That is would I have to print a new x carriage or anything?
Re: Problem with HotEnd?
March 06, 2014 11:46AM
I printed a new x-carriage as I put a different fan with it than the one supplied. If you use the supplied fan and shroud then you don't need anything that isn't supplied. I don't use the print cooling fan that came with the kit from nophead - there might be a problem with fitting that. Here's mine with links to parts I added: [forum.e3d-online.com]
Re: Problem with HotEnd?
March 06, 2014 12:17PM
Wow, that's pretty slick. I like. Right now I haven't printed with ABS so would be nervous about trying to print a new x-carriage. Maybe I'll get the e3d hotend, use it with the supplied fan and shroud (i have the kit) and then later change it out for what you did there.
Re: Problem with HotEnd?
March 06, 2014 02:05PM
I printed the x-carriage in PLA, no problems.
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