# 3D850 stuck in the nozzle

I am trying to use a 3D850 PLA filament which is supposed to work without any issues with any PLA printer. As a printer, I use Dagoma NEVA which is supposed to work with any PLA filament. I can print with the filament without any issue, but I encounter a problem when I need to swap the filament. Somehow 3D850 sticks within the nozzle and even when it's heated I have to push really hard with another filament to push the current filament out (usually when the nozzle is heated up I can just easily push a filament inside for it to come out of the nozzle).

Is there any special behavior of 3D850 that may cause it to stick inside of the nozzle?

• Consider overheating the head to further decrease the viscosity of the residual material in the nozzle. Then, of course, return to design temperature before printing. – Carl Witthoft Feb 21 '18 at 13:43
• @CarlWitthoft the max temperature for Neva is 220º C (according to 3dprinting.com/pricewatch/3d-printer/dagoma-neva) and this is what their "nozzle cleaning mode" uses. I am wondering in general if I'm doing something wrong because print temperature for 3D850 is 190-230ºC and I printed it at 210º. I can try printing it on 220º but I don't understand why I cant remove the filament easily. So far my other experience was only with Verbatim PLA. The recommendation for it is 200-220º and it perfectly worked at 210º – Uko Feb 21 '18 at 15:27

My guess is that particular brand of PLA is changing state inside the nozzle as it cools. Quoting from the manufacturer's page,

Materio3D PLA uses the NatureWorks Ingeo 3D850 polymer, specially engineered for 3D printing. It is tougher and stronger than standard PLA and can be annealed for improved heat resistance and toughness!

If the residual material in the nozzle cools slowly enough (at the end of a print) to anneal, then by design it won't re-melt at the same temperature as the raw filament material. I would recommend changing your gcode so that the extruder hotend is held at temperature after a print completes, and making sure to clear the nozzle with an alternate type of filament before allowing the nozzle to cool.

quoting from another page,

To achieve a heat treat on a printed part, submerge in water (or bake in oven) at 200F for up to 30 minutes.

notice that's Fahrenheit, well below extruder temperatures.

• I'm totally fascinated by this explanation, +1, but it has to be noted that all PLA can be annealed, so to a certain degree, all filaments should manifest this behaviour. Also: holding the hotend hot indefinitively without extruding is likely to cause clogging the first time you forget about it, I would suggest instead that the OP use G4 or equivalent code to delay the shutdown of an amount of time sufficient to purge the nozzle. – mac Feb 21 '18 at 21:03
• @mac I suspect all PLAs do show this -- Whenever I restart, and do a "push-through," the initial glob is definitely stiffer to push out than when I'm feeding fresh filament by hand. – Carl Witthoft Feb 21 '18 at 21:05
• Annealing affects the structure, and maybe the behaviour around the glass transition, not so much the fluid transition. There could still be some baking/polymerisation or loss of solvent though. – Sean Houlihane Feb 27 '18 at 16:27