Need help cleaning my hotend (2nd attempt)
Second post - this time with the right image link.
=====
I'm in the middle of an upgrade of my trusted MK3 to MK3S/MMU2 - which means I'm rebuilding the extruder, the hotend gets a longer PTFE tube in it. As with most 3D printer folks, I have had my accidents/bad prints, including those where the hot-end gets a lot of plastic accumulated on it. So the result is a lot of old burned plastic on the hotend. When it was off I heated it up and removed as much of the easy to get to plastic with a small screwdriver and this is where I am right now:
I need to replace the nozzle - the current one has printed A LOT and I can see issues indicating that my 0.4 nozzle is a "bit bigger" now. Note, it printed just fine even full of plastic - except you could see some layer marks due to the nozzle.
I've tried several things, but I cannot get the hotend taken apart. I would very much like to get the screw that holds the heating element and sensor loosened and dip the hotend in acetone to get it all clean up. I hope that will allow me to remove the nozzle - which so far I've had little success with. Pretty sure it's stuck on plastic holding it in place. So I'm looking for ideas on how to get this cleaned up and getting the nozzle removed so I can replace it.
RE: Need help cleaning my hotend (2nd attempt)
Fist of all you need to get the whole hotend HOT to at least 230-250 centigrade.This is the only way you are going to get that nozzle out. It won't come out cold especially if it has been used, too much plastic around it. Should have done that before you took it all apart. You can get those screws loose also when it is hot. It is best to do it before you take it apart.
RE: Need help cleaning my hotend (2nd attempt)
That's what I did - I powered it on my work bench. Trust me, not easy to do this when it's mounted - it was 2-3 times as bad before I removed what I could without risking damaging anything. But the screws are not going to work - they don't bite the hex wrench. I can and probably will try to heat it again, but the more I do that the more I risk destroying the cable or making bigger marks in the block than I already have.
Fist of all you need to get the whole hotend HOT to at least 230-250 centigrade.This is the only way you are going to get that nozzle out. It won't come out cold especially if it has been used, too much plastic around it. Should have done that before you took it all apart. You can get those screws loose also when it is hot. It is best to do it before you take it apart.
RE: Need help cleaning my hotend (2nd attempt)
Quick update - got the nozzle and the cooling element removed, just needed bigger tools to get the nozzle loose - and I got the screw holding the heating element in out by heating the element up to operational temperature - I guess that made what-ever was blocking the hex-wrench before fluent enough to get out of the way. The pressures I had to apply definitely could not be done while this unit was in the printer.
The heating element and the temp-probe are both still stuck in there, but there's progress on the other fronts.
RE: Need help cleaning my hotend (2nd attempt)
I've had good luck cleaning filament residue from the heat block by getting it good and hot with a bench supply and then scraping with a razor scraper.
Then (when cool, of course) finish it up with a soft wire brush and/or a sanding sponge.
RE:
Razor blades? Not sure I can find those; what I have is something that could look like that but it's plastic. I use that to clear off prints (particularly failed prints) off the bed. Seems a bit too large for the hot part. Note, I think I got it clean enough to be functional - not looking pretty but should be just fine.
I've had good luck cleaning filament residue from the heat block by getting it good and hot with a bench supply and then scraping with a razor scraper.
Then (when cool, of course) finish it up with a soft wire brush and/or a sanding sponge.
RE: Need help cleaning my hotend (2nd attempt)
What I'm referring to as a 'razor scraper' is one of those scrapers that are commonly available at hardware stores for such things as removing paint splatter and overspray from glass. They use single-edge razor blades and are stocked at Home Depot and about any other place that carries paint and tools.
When the heat block is heated well above the melting temperature of filaments, the filament residue gunk will simply scrape off. You will need to hold the heat block with something (I used a hemostat) because it will be very dangerous to touch.