Jamming

Sometimes, the PLA can jam inside the extruder, and it's really not obvious how to unmount it or hack it to prevent this jams.

Unmount the extruder to clean it after it jammed

Remember: PLA and PEEK will bond extremely well, especially when hot, and the goal is to prevent any contact or gap. Also remember, hot metal and plastic is hot, use proper tools and care.

1. remove the fan assembly of the hot end
2. Set temperature to 210º
3. Once temperature reached 210º, open the 4 long M3 screws to lower the hot part
4. use a piece of wood to prevent the hot end from melting a hole into the acrylic bed, or let it hang freely in mid air
5. use larger pliers to handle or hold the hot end
6. Once lowered, you can cut the PLA filament
7. Pull the PLA filament way back into the bowden
8. use pliers to pull the PLA plug out of the PEEK
9. use a small tool to remove/scrape any molten PLA from around the brass tube and the PEEK

Optional extra steps that are not really necessary:

1. increase the heat to 240-250C
2. wait for the PLA to drip out of the nozzle (1-2 minutes max)
3. lower the heat to 200C
4. remove the nozzle carefully
5. while hot, wipe the inside of the nozzle with a cotton stick (paper or wood is preferred, make sure no cotton fibers are left behind.)
6. put it back on the brass tube for 1 turn to reheat (1 min) and repeat the previous step if necessary
7. remove some of the cotton from the Q-tip, and push it though the brass tube to clean the inside. repeat if necessary.
8. put the nozzle back on the brass tube. use the proper sealing tape if necessary. tighten carefully.

Cont. from above, before the optional steps:

1. turn off the heater
2. make sure the bowden tube extends far enough under the white retainer ring, about 8mm, a bit more is better than not enough.
3. the bowden will only move downwards, not really upwards, so shave off some bowden material if necessary, and make sure the metal teeth inside the retainer clip are clean and have good grip
4. chamfer the bowden (see below)
5. reseat the retainer blue clip
6. measure the depth of the PEEK well, and the extension of the bowden, making sure the Bowden will reach all the way inside to the brass tube (any gap between the bowden and the brass will cause a leak, which will cause the plug/jam again)
7. guide the bowden back into the PEEK, and tighten the screws accordingly (there needs to be a gap between the alu and the wood, otherwise you will not have a proper pressure seal between the bowden and the brass tube)
8. wait for the temp to drop below 50C
9. guide the filament through the bowden, and feel for any obstruction, especially at the bowden/brass interface (35mm before you hit the hard stop of the cold nozzle)
10. if you feel significant resistance, undo the 4 screws, and check where the obstruction is, and fix it.

Happy printing

Hack the bowden tube to prevent jamming

HACK While this change seems to work for some people. The most likely result is that it will make things worse. As you have more heated area contacting the bowden tube.

Found on Ultimaker Forum - http://forum.ultimaker.com/viewtopic.php?f=7&t=102 - a hack by Joergen:

There are a two things at the hot end that need to be solid and never move: one is the PFA/PTFE bowden tube inside the PEEK, and the bowden retainer ring/clip above (if the ring/clip does not support the bowden tube anymore, make sure the metal teeth inside the white clip are clean and don't forget that the bowden will only go through it one way. If that doesn't help anymore, print some reinforcement: http://www.thingiverse.com/thing:11864).

The bowden needs to make a solid flat connection to the brass tube inside the PEEK:

As you can see it is very difficult to get a perfect perpendicular cut/connection, and if the bowden isn't pressed hard enough against the brass, plastic will leak, and the problems start.

you can solve this by drilling out some of the bowden with a 4.5mm drill (by hand), not much deeper than 0.5mm (depending on how far the brass tube extends out of the PEEK):

(In this example I drilled a bit too deep, but you can shave off some of the bowden to lower the depth of the bevel.)

Now the Brass tube can slide into the bowden ever so slightly (especially if your brass tube thread is turned down a bit), making a much better seal: