I own a P1S for a few weeks now. For the first printed parts I used the green sample PLA shipped with the printer. The parts look good so far. To get more into the topic I bought some inexpensive white Sunlu PLA+. The results also look good after determining correct PA, flow rate and temperature.
Now I have a black PETG spool from Extrudr. As before, I did the Flow Dynamic test to get a correct k value and then printed a 1-wall calibration cube, that I use to measure the wall thickness using a micrometer and calculated the correct flow rate. Now, a second cube looks perfect from a measurement perspective.
However, I noticed some tiny zits or holes (cannot really tell, because they are so small) on both black cubes.
I cannot see that issue on my calibration cube for the white PLA+. However, the black PETG has a more shiny look than the more matte white PLA+. Maybe I have the same issue there but cannot see it.
Is this normal? Is this an issue with the filament or even the printer? What can I try to fix this?
I already put the PETG for 4h in the oven to dry it (although it is new and was vacuum-packed). Nothing changed.
I also used the needle to try to „clean“ the nozzle. Again, nothing changed.
BTW, I printed the cube in „spiral vase“ mode, so what we see cannot be seams. I use the 0.2mm Standard profile.
It is recommended to try and dry the filament for a longer period. It seems like the small dots might be related to some remaining moisture in the filament.
It is recommended to try and dry the filament for a longer period.
What is a good drying time?
Extrudr itself write on their website, that their PETG should be dried at 60°C for 4-6 hours. However, they wrote me via eMail that no drying is necessary, if I use the filament right after unpacking it … which is what I did in the first place.
Today I put the filament in a Sunlu S2 dryer at 60°C for 6 hours (keeping the dryer slightly open using some wedge to let the wet air escape). I then printed a new cube directly from the dryer while the S2 was continuing the drying process.
That is a very wide open question and there unfortunately isn’t a simple answer. Drying time has a huge dependence on ambient humidity. And then there is the question of knowing when drying is done - how do you know?
There aren’t many solid answers. The one you see in most directions is to dry for X hours at Y temperature which hate to say it is pretty useless. You can get pretty close to specifying a water content by saying what humidity to dry to at what temperature. That does specify a water content for the air in a filament dryer which given enough time also says a lot about water content in a filament that has been in that environment for a while.
But it’s a very imprecise thing as it is now. There’s work being done to address this, though.
Now I dried it for 19 hours in my Sunlu S2 @65°C. I weighed the spool before and after drying. Before drying it had 1191,6g. After drying: 1191,6g. So no measurable loss here. And the next test-print did look the same.
Do you still think it is wet filament? What else can cause this?
I found something similar here and here a more extreme example. Unfortuntately, without any real solution mentioned.
I have had the same issue with my PETG. Purchased from Bambu labs, and others. Seems to happen more on the horizontal surfaces too. Walls look very clean.
