I love my K8400! Now that I understand all of its quirks I am printing some awesome stuff. I hope to help you with your issue. Let me know if you need some clarification.
Fan issue fix:
Replace parts or improvise.
I had this same exact problem. I burnt out my fans after mistakenly having some leftover superglue from a repair flow down to the board of the hot end. However, the fan burn-out was a blessing because I ended up improvising my set up. I purchased three mini-desktop fans and mounted them in a way so they blow towards the printing surface and the hot-end. Along with an another technique I use for printing my models come out awesome. Like $2000 machine quality awesome for a lot cheaper.
Clogged Nozzle/Cleaning:
A less messy alternative to chemical cleaning.
The reason I always had this problem is because my hot-end would overheat causing the PLA from the top of the isolator to expand just a little bit to where it would become stuck and “underfed” through the extruder. (even when I had everything functioning correctly) So first, you need to make sure your “hot end” or more specifically your isolator remains cool. This will prevent the PLA from expanding in the cold parts of the hot end and not being able to run through. To fix this problem try devising a way to have a fan blowing at the isolator to keep it cool. I’ll post a picture of my set up later if you need ideas.
The unclog a nozzle: I first heat the hot-end to my preferred PLA temperature. Then, I use a very thin wire and insert it into the nozzle while it is hot. Move it in and out to break up the carbonized bits of PLA. You should be able to pull out some melted plastic at this point. Now move to the top of the extruder and unscrew the nozzle going into the isolator guide. (I advise having a fan blowing at the general direction of the hot-end.) Cut the PLA from the isolator guide with a utility knife. Then find a hex or allen key that will fit into the isolator guide. Stick it in there and try pushing out the PLA. If it does not work keep using a wire to break up the PLA at the hot-end nozzle and repeat. You will pull out melted PLA until this process does not pull out any more melted PLA from the isolator guide. Now, screw in the PLA nozzle at the top of the isolator guide. Use repretier host controls to manually extract the PLA through the isolator guide. (do not extract too much material otherwise it will clog again.) Then when you see PLA coming through then you’re golden. So you should be good at this point.
Throughout this process you need to keep your hot-end…hot. This has to be done quickly to minimize another clog.
*please use this advice at your own risk. I had to break a lot of things to get to this method for which is the most reliable way to fix this problem in my eyes.
I’m having the exact same problem with filament getting stuck in the isolator. I came up with a solution to get the clog out. Dismount the isolator and place it in the oven at 225 degrees centigrade. After about 10-15 minutes you can pick it out and use a thin tool to remove the clog.
But I don’t really know why this is happening to me. I have made many parts before without any problems. But now I keep getting this problem. Maybe it’s more of a problem with certain parts? That withdraw filaments and jumps in different patterns that makes the filament go slower out of the nozzle?
My problem is the printer was working normally and then it started failing to feed. The Bowden slipping the filament is not getting in. I changed the nozzle and changed the heat break and the problem present also now the filament is keep dropping from the nozzle. Any suggestions?
