Filament ooze on MK3s hotend solved
This is a copy of previous post a put in for a topic about problem with E3D V6 hotend.
I recently changed my nozzle on my MK3s and had filament ooze problems. I torqued up the nozzle to 2.5NM as recommended. What actually happened was that the heatsink rotated in the extruder body until the nozzle tightened up against the heat block. The actual tension between the heatbreak and the nozzle was only the friction of the heatsink had with the extruder body. I did hold the heatblock with a custom made spanner to stop it rotating.
I subsequently removed the hotend and while heating the heatblock with a hotair gun I tightened the nozzle to 2.5NM as recommended in the manual (actually 3NM was in the manual) and promptly stripped the thread in the heat block as the recommend torque is way too high.
The following is a modification I made which solved the problem.
I have got a new heat block and after having removed the hotend from the extruder I used superglue to glue a 5mm strip of 120 grit wet and dry sandpaper to the neck of the hotend heatsink. I then fitted the new heat block to the heatsink and screwed the nozzle to the heatblock (cold) until it was firm and the sandpaper was to the front of the extruder with the heat block in its correct position. I also made sure that there was sufficient gap between the heatblock and the nozzle rim. After reinstalling the hotend I heated the hotend to 280deg C I held the heatblock with a wrench ( I made a custom one out of 3mm steel plate) and firmly tightened the nozzle with a 6 inch ring spanner. I folded up a small piece of paper and stuck it into the heatsink fins to ensure that it did not rotate. It seems that the sandpaper gave sufficient grip to ensure the heatsink did not rotate with a firm tightening of the nozzle.
I have since used the printer and have no filament ooze. It would seem that firm tightening of the nozzle is all that is require to ensure a leak free hotend. On no account should a torque wrench be used with the recommend 3NM of torque.
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This sounds rather long-winded. I just use 17mm and 7mm bicycle spanners. Did you try the recommended procedure, paying particular attention to the diagrams at the bottom of this page:
https://help.prusa3d.com/en/article/changing-or-replacing-the-nozzle-mk2-5s-mk3s-mk3s_2069
Cheerio,
RE: Filament ooze on MK3s hotend solved
Let's face it. MK3S nozzle changing is a bear. One of the best things about the MK4 is the combined nozzle and heatbreak which allows for room temperature nozzle changing and no chance of oozing.
I had oozing issues with my MK3S and had to come up with a modified procedure to minimize the oozing. It wasn't as elaborate as what @willo47 is doing, but if it works I think that's great.
RE:
A tiny dab of loctite (or similar) thread locker will help keep it in place?
But just noticed you heated the nozzle up with a heat gun - don't do that, you won't get it to the right temperature to a hot enough temperature. Prusa recommends heating up to around 285C and then tightening. If you do that you should have no problem.
Same the other way around too - once you have correctly heated up to 285c before tightening to the correct torque, you'll need to heat to the same to loosen it again.