3rd Hot End in 4 months! (Page 1 of 2)

The SD nozzle is made of standard materials from what I understand, so clogging with that frequency means you are doing something else wrong (sorry for the accusing tone, ).  Other printers in this price category come with the same types of nozzles.

Are you letting the printer sit idle at temperature?  This will cause plastic to burn in the nozzle. 

What temps are you printing at?  Have you verified the temperature with, say, an IR thermometer?

Where are you sourcing your filament?  I have had vastly different behaviour from different filaments labelled 1.75mm ABS, and the one time I did clog a nozzle was when I switched to a filament with lower melting temp.  Make sure you calibrate for the filament before any long prints, and stop using stuff that has killed more than one nozzle.

IR thermometers can't correct for emissivity...

I'm saying IR thermometers aren't a great tool for absolute temperature measurement.

I think your problem might not be so much the filament clogging in the nozzle as it is melting up in the PEEK instead. That is a seems to be a problem that I was having with my OEM hotend. I fixed that by using the MK4 jigsaw replacement with pyrophreeks fan duct. http://www.thingiverse.com/thing:88660 It keeps the PEEK cool and shrinks the melt zone of the hotend keeping the ABS solid until it reaches the brass barrel.

I have never taken apart the whole barrel, as i can't ever move either end of it to take apart. I slowed down the filament speed draw and that seemed to help alot. I am wondering if my printer is trying to grab plastic and cannot do it fast enough. If that's the case I am not sure what the solution would be, as I don't want all of my prints super slow.

If you are still looking for an accurate way to use an ir thermometer to check the hotend you can either paint it or place masking tape on it then correct for emissivity afterwards, usually I paint my targets black(non gloss) and change emissivity to 1.0. If you have a one of the cheaper ir guns some of them let you change the emissivity value a little and some are fixed.

I can't print so its going to be tough for me to make the mark 4 extruder assembly. Would someone be able to print and ship me one?

I'm not sure which may apply in your case, but here are some possibilities off the top of my head:

1) When I got my first clog, it was because I had printed without realizing that the fan on the extruder hadn't started up, allowing the filament to eventually soften up and block the top of the peek. 

2) Then second clog occurred after I had assembled the nozzle with the barrel not fully inserted into the peek, again causing the top of the peek to be blocked up because it wasn't hot enough there.

3) If you tension isn't correct or something is keeping the idler wheel from freely turning, maybe this is causing your filament to slip mid print, and after awhile, the non-moving filament burns in the nozzle (i.e. slipped filament is causing the clog instead of vice-versa).

Hope this helps.

What are you cleaning the 0.35mm extruder orifice with? I had one clog and drilled out all of the polymer from the peek down with fine drill bits and then found (and modified) a fine gauge pin to insure that the path was completely open and free of residual polymer. No idea if this is the right way to do it or if its pertinent to your difficulties, but thought I'd share just in case

Guitar String - Nice. I actual have a spare but didn't think to use it. Ended up sanding down a slightly oversized Guage pin

Are you guys cleaning it while its hot? Or are you waiting till it cools. And I have no idea how to clean it with guitar string. How do you do that? Just slide some in while it's hot?

I have been having intermittent failure to extrude.  It'll be laying down filament and then it'll just start laying down nothing but crumbs, while meanwhile the filament's not moving and the teeth are grinding away  making dust.  I've resorted to marking filament with a sharpie to see if the mark is moving.  If, at this point, I take the filament in my fingers and push down on it, it'll often start moving again (as long as I don't push too hard and cause it to kink), and then run for a while before it stops again.  I have been able to get a few print jobs to completion this way, but only by pretty much doing nothing but standing there watching them, so I can shepherd the filament through.

Note that there's no known change since when this was working fine.  I've rechecked leveling and other calibrations.  This happens with any filament, including filament that's been working fine, and I doubt I've suddenly had a change in a half-dozen separate spools of filament simultaneously.  It started happening gradually and got worse over a week or two.

I've also tried cleaning a possible partial clog with guitar wire (nothing obvious came out), and with letting the filament cool to 160-170 and then pulling it up and out a few times (didn't get any evident debris or buildup out with it).  I haven't gone as far as acetone or blowtorch.  After all, I don't know of it's a partial clog in the first place.

Ian and 2n2r5 suggested in IRC this might be that the heat is travelling up the PEEK and getting the filament a bit too soupy up there, and that the fan mod above might help.  I was never very clear on how I could mount it on a Lawsy MK4, and I exceeded my quota of stupid questions answered before I could get a clear idea of what mounting hardware I might need, so I ordered the fans anyway, hoping when they got here I'd be able to figure it out, and it wouldn't end up depending on me having some part I don't have (like it always does).  After all, some of the mount points for the extruder are already the right distance for a 40mm fan, as shown in Ian's picture above.

Here's my extruder with the MK4 with its lower brace removed, and the 40mm x 10mm fan looking forlorn on my behalf:

If there weren't that big bump sticking out in the lower left, I think I could just swap the long M3 screws that go into the two bottom-most points with the shorter ones just above, using the extra length to mount the fan much as Ian has in his picture.  Seems like this places the fan a little too low; the bottom half is blowing on the top half of the extruder itself.  But since it can't be made to fit there anyway because of that protrusion in lower left, it's a moot point. 

Ian suggested that the solution is to have previously found, or designed, some kind of custom mount that would hold the fan onto the MK4 in the right place, and to have printed it earlier.  I suppose I could try to print it out now and hope I got really, really lucky, but I doubt that's possible.  Then to get the mounting hardware that would need as well.

Heck, maybe I should just hacksaw off that protrusion.  Though I assume that'd put the fan way too close to the PEEK and hot-end.

I also have an MK5 printed and stashed as my emergency backup.  If I could make this all fit with an MK5 without any prints I don't already have, switching over to that could be an option.

And after all this, I'm still far from sure this is even going to help.  Some of the symptoms Ian asked about (like that the problem wouldn't be there at the start of a job, but would creep in later) aren't happening for me.

Any advice for a poor little just-barely-past-newbie in over his head (again)?