Inconsistent Nylon Heat Creep Failure
Hey everybody, I've been trying to get my mk3s to print nylon for a few weeks now and I'm running out of ideas. When loading the filament and manually running the extruder motor the filament extrudes perfectly. Once I start a print, however things go bad.
Sometimes it makes it an hour into the print sometimes it doesn't print anything at all but at some point the filament jams and the print head continues on without extruding anything. Removing the filament shows that it's melting higher in the heat brake due to heat creep. Unloading, clipping, and reloading the filament can get it printing again, for a while
I read up on Prusa's Heat Creep guide and have tried the following:
-checked nozzle gap to heat block
-lowered bed temperature and kept enclosure open to help keep cooler air circulating
-dissasembled hot end to clean fan and heat sink
-replaced PFTE tube for good measure
So far none of this has helped in the slightest and I'm still getting failures, often at the very start of the print now. I'm looking for ideas of what to try next. Should I replace the hot end? Upgrade to a bi-metal heat brake? Or is this my sign to buy the Mk4. Losing my mind over here so any ideas are appreciated.
Important info:
I'm using Polymaker's Polyamide PaCf. I'm running this out of a dry box, through a Bowden tube and a hardened steel nozzle. Relevant settings are as follows.
Nozzle Temp: 290°C
Bed Temp: 35°C
Print Speed: 45mm/s
Print Cooling: Off
Retraction Distance: 3mm
Retraction Speed: 40mm/s
RE:
You don’t say the nozzle size. I gather it’s the usual 0.4mm ?. It shouldn’t matter with your issue but sometimes carbon fiber filaments are prone to clog with nozzles smaller than 0.6.
You don’t say either which printing plate and if you’re using adhesive or not. Nylon filaments tend to be troublesome regarding adhesion and warping, As you haven’t mentioned those problems, probably it doesn’t matter either and carbon fiber nylons warp much less than pure nylon, but they also like a stable and warm environment, so it doesn’t seems a good idea to open the doors of the enclosure.
Where I see a possible source of trouble is with the retraction distance. Why do you use a value as high as 3 mm.?. If it’s Polymaker’s recommended setting, it probably refers to Bowden extruders, not for the direct drive extruder of Prusa printers. Heat creep usually happens when the filament retracts too much into the heatbreak, so the melted part enters into the theoretically cold bottom of the heatbreak and it jams there. I’d try a retraction of 1 mm. or less and see if this alleviates or suppress your problem.
RE: Inconsistent Nylon Heat Creep Failure
Shoot nozzle size is the one thing I forgot to add haha. Yeah I'm using a 0.4mm nozzle. Bed adhesion hasn't been an issue I have the uncoated plate and use glue
As for the retraction, 3mm is actually what Polymaker recommends specifically for direct drive (they recommend 4mm for Bowden iirc). I'll have to try lowering the retraction distance and see if that helps though! Thanks for the input!
RE: Inconsistent Nylon Heat Creep Failure
Update: Lowering to 1mm retraction distance did not alleviate the issue :/