Constant jams, and I'm stumped

I'm suddenly experiencing bad jams over and over. I've changed nozzle and heat break twice, disassembled and cleaned out the V6 hotend several times but immediately each time I try again the thing jams. I've been printing with good success for three years and many hundreds of prints, never seen anything like this.

Using CarbonX PETG, my favorite filament for mechanical components. Nozzle 0.4, 335°/70°. Fan is fine, and I've certainly never had PETG jams before, only a couple of times with PLA when the fan failed. The heat break is PTFE lined, which I have always preferred. Not sure what else to say, any guesses?

Thnx

You've checked the PTFE liner? They slowly decompose, moreso above PLA temps, and can pinch down and cause troubles.
Jams from making the replacement liner a little too short or not fully inserted are not uncommon.

Not sure about the V6, but my hot end is quite fussy about how far the heat break tube is screwed into the heater block - not far enough, and the nozzle seats against the heater block instead of the tube. One turn later, the upper end of the heat break is too close to the heater block and it's jam city. But there is a happy medium.

Thanks for the reply tray. Yes, the heat break is new right now and I've tried three. But I'll look into the other issues, though it is assembled correctly, as in nozzle not against the heater block. Also, I tried one w/o the PTFE, same problem.

Edited 3 time(s). Last edit at 02/22/2020 10:00PM by papilio.

Is this a direct drive or bowden tube? if it's bowden, have you tried a new tube?

If it's a direct nozzle (no PTFE tube) then check your retraction amount - too high and you'll pull the molten end of the filament back into the cold area, where it will set and jam the nozzle. I usually set mine to 2.5 - 3.0mm.

I just last night discovered the problem ... and as I'd suspected all along, it was indeed USER ERROR. I just couldn't nail it down, until I realized ...
When I'd ordered the new PTFE heat break from Amazon, I'd mistakenly ordered 3mm not 1.75! I guess I've taken apart and reassembled the hot end so many times over the years I just hadn't noticed.

I don't mind having a good laugh at myself when I encounter things like this!

To respond to a few issues raised above ... yes I had installed a new Bowden, and I like to keep my retractions below 2mm.

Thanks guys for all the help and suggestions!

Edited 2 time(s). Last edit at 02/27/2020 09:09AM by papilio.