I’m having trouble printing paht-cf all of a sudden. Last time I printed with it, it did fine. Stock settings with .6 nozzle. Now it is warping really bad and seems to be melting the engineering plate. My first prints this time were with high infill, just like before when I was successful. With the print in the pic, I lowered the infill to 25% gyroid & lowered the bed temp to 50deg. It didn’t seem to melt the plate this time, but still warped. Any ideas?
If I were to say “filament dryer”, would you know what I’m talking about? 
Nylon absorbs water from the air at a prodigious pace. It is more “hydrophilic” than just about any other filament, and it can soak up something like 5% of its weight in water vapor from the air.
So “suddenly my Nylon filament won’t print as well as it used to” makes me think “moisture absorption” and filament dryer.
As for the build plate, yeah I’ve seen the same thing happen with a totally different brand of filament. I just run a flat blade across the surface to scrape off the high spots. I don’t know if it’s the print attacking the build plate or just some remnant material left behind when the print is pulled off. But either way, it’s removable.
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I do understand what a filiment dryer is. I did use the x1 carbon drying option twice before using it. I did it one day 12hrs at 80deg, but i didnt have my .06 nozzle, so i dried it again the next day the same amount, then was able to print right after. Are you saying this drying method isnt good enough?
What did you do with the filament between the first and second drying? Nylon is so good at absorbing moisture, particularly in high humidity conditions, it only takes a couple of hours to erase many times more hours of drying.
I don’t think the heat-bed drying method is very good. If you’ve got nothing else, it’s better than nothing. But even with the chamber fan cranking at a jet-turbine sound level, I don’t think it distributes heat very well. The side of the spool resting on the bed gets good and hot, the opposite side does not (remember, plastic is a good insulator, and a spool full is a big wad of plastic and it’s only really getting heated from one side). You need the chamber temp to get up to >70º so the spool is heated uniformly, and the build chamber just won’t do that.
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It sat in the bag it came in with a silica gel pack inside with the bag inside the box.
The only reliable method I’ve found to be sure filament is dry is to weigh it, then dry it with heat until it stops losing weight. I’ve found a full kg of filament direct from the original vacuum bag typically loses 2 to 6 grams of weight after drying. That is 2 to 6 cc of water or up to 1¼ teaspoons for the metrically challenged. The various humidity sensors are measuring the moisture in the air, which can be quite different from the moisture in the filament.
Silica gel can slow moisture absorption, but it will not do a good job of removing moisture without a lot of time and frequently refreshed silica gel.
Using the X1C has a dryer has been effective for me, but it is slow and inconvenient. At some point I’ll probably need to invest in a dedicated dryer for long prints made with very hydrophilic filaments. I’ve not tried PAHT-CF, but dried filaments including TPU, ASA, and PC have all produced good prints.
You have no idea how well the bag was sealed. You have no idea how good the Silica gel in that package was. You don’t know what the initial conditions of the filament were before it was packaged. You don’t know what environmental conditions were when the filament was packaged. And you don’t know what conditions the filament was subjected to in storage/shipment/handling.
All you can be sure of when you take filament from a new, unopened bag is that you have a roll of filament in your hand. When it comes to how “wet” the filament is, the best assumption is to assume the worst. Other than the wait time for drying, there’s no downside to this assumption. And based on my experience of late, anyway, assuming the worst is actually the best assumption - it’s often the correct assumption.
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+1 – the roughness on the top of that part looks like wet filament to me…