So this happened. Opened the PETG (Overture brand) last night and got a few good prints. Then set this to go this morning and checked it after an hour. I have it in my AMS with a spool weight full of dessicant in it. I have so much dessicant in my AMS the humidity in it is 11% vs 42% for the room the printer is in. Do I need to put my PETG in a dryer? How does one use PETG in the AMS and not have this happen?
I’m using the 0.4 standard nozzle, 0.20 standard profile, generic PETG filament profile. I have been meaning to swap out the nozzle and extruder gear for hardened ones so I can print glow in the dark filaments so maybe that will help with PETG?
It is always a good idea to dry filament before inserting it in the AMS. The filament could very well be saturated even from a fresh bag. The AMS can only slow water uptake, not remove water from filament.
It could also very well be a partial clog.
Finally, there’s speed. I have not tryed a .2 nozzle with PETG personally, but I am frequently reducing speed and acceleration for PETG with a .4 nozzle. For complex geometries with overhangs, I reduce these down to 1/4. I only use standard settings for simple shapes.
If you have an X1C you can you use the built in drying function. If using a P1S or enclosed P1 you can achieve the same results by following this table from the Bambu Lab Wiki
Of course, you could also use an oven, but temp control is usually much more difficult and you run the risk of filament strands sticking together slightly. Found out the hard way a couple of years back Also, you may not appreciate the smell in the same place as a major cooking appliance If you go for a convection oven (for example to dry many rolls at once), make sure that you put a precise thermometer in with it.
If you go for the easy method and use your printers heat bed with the bottom of the cardboard box as a lid, make sure to have a few holes in it so that humidity can escape easily. You could also place a bag of (dry) desiccant in with it. It’ll actually also work with open printers as long as they have a heated bed and you use a lid but may be less efficient.
Also note that the Bambu recommendations on drying time play it fairly safe. So following those should get you a sufficiently dry filament.
Saying that, your original problem may not be due to moisture uptake. But at least you can rule that out by drying.
Drying is a good first step to fix the problem, and removes moisture as a possible source of the problem. It is pretty common for new spools to retain some moisture from the manufacturing process.
Desiccant lowers the humidity of the air, and can help keep dry filaments dry. Desiccant is not so good at removing moisture. It takes a very long time for the moisture in the filament to reach equilibrium with the moisture in the air, and might require several desiccant changes. You really need to dry with heat.
I had similarly bad results from my first use of PETG. Printing a temperature tower showed me that I needed a higher temperature to get the filament to stick to itself. In fact, that filament need a higher temperature than either the Bambu Generic PETG profile or the manufacturers recommendation.
With the cold pull, there are several methods in the wiki for the X1C but I imagine they also apply to the P1.
For me, only the Allen key method actually worked reliably. It is a bit daunting if you have have not done that before, but, taking care not to burn yourself, it is actually a rather quick fix.
That could free up the printer quickly but I agree with @lkraus: If in doubt, dry it out
It is only a question of time as to when filament moisture ruins a print if not dried.
And another good point from @lkraus
There’s a thread somewhere here on Bambu’s Blue PETG needing higher temps. May be linked to the pigmentation and hence could also apply to the print in your pic’s.
The nozzle wasn’t clogged. I replaced it and the extruder though with hardened versions. I upped the extrusion temp from 255 to 270 and the bed temp to 70. The first print looks good again.
Also, you may not appreciate the smell in the same place as a major cooking appliance 