I am using a P1S 0.4mm nozzle with Bambu matt PLA filament. My holes need to “pierce” the first layer and extend all the way through the bottom surface (think watering can sprinkler head) Every time I try to do this the first layer appears to print fine, but when the second layer prints it almost always “fills in” my holes about 50% of the time. I have tried slowing everything down by 50% but it makes no difference (0.75mm is slightly better but I really want 0.5mm). I have only tried PLA because that is all I have. If a better material is the recommended solution please tell me what material I should try. I do have a 0.2mm nozzle that I will try but I haven’t taken the time to switch out nozzles yet. Again if that is the solution, just tell me to stop procrastinating 
a couple quick things to try before swapping to the .2mm:
-arachne walls
-swap inner/outer wall order
-reduce line width for outer and inner walls
-use a modifier to set only 1 wall loop for hole
or try whole print with 1 wall
you should be able to zoom into the sliced model in studio and kinda see whats going on. If I try standard print settings and zoom in, it almost looks like the seam protrudes inward, possibly causing the issue
goodluck!
If there is room between the holes you could try making the diameter of the internal part of the holes a little larger.
Plus you could try a slightly different shape for the internal parts of the holes (plus maybe the outer parts too).
A 0.2mm nozzle would help -but it would multiply print time by at about 4x
Maybe instead of making a circle with parallel walls, make a very mildly conical shape that is .5mm at Z=0, the build plate, but tapers to .55mm at Z= 1".
In my experience with very tiny items I probably make 3 - 4 preliminary prints of only a few mm thickness until I find a happy setting.
Separate from that, but a problem, is where the writer of the code has set in a fixed minimum value that is larger than the number I want to define.
The first layer likely works due to the elephant foot compensation (default set to 0.15), which effectively enlarges hole diameters on that layer. Try setting the elephant foot compensation to 0, and then adjust the “X/Y hole compensation” setting until the holes have the desired diameter.
For small holes, I wouldn’t use a circle. Instead I’d make an octagon and add a triangle to one face. Small holes print like an octagon anyways. The extra space in the triangle gives the z seam a place to go and be out of the way. I had to change my z seam location to BACK because ALIGNED didn’t put it there for some reason. That could be an issue depending on where you want the z seam in the larger model.
I would also put an asymmetrical chamfer on the bottom of the hole of .2mm by .8mm so that it tapers up through at least 3 layers to account for the squish of the bottom layer (which can telegraph up to 3 layers).
Edit: Just did a test print. I didn’t use any compensation features in the slicer. I made a test piece with 4 holes. The hole with a diameter of .85mm allowed the .4mm nozzle cleaner that came with my printer to pass through. This was on the A1 mini. The diameter is something you’ll have to experiment with.
Wow, thanks for all the tips. Arachne walls, number of walls and reduced line width didn’t have any impact that I could notice. However, switching inner/outer made a big difference. From another comment I also played with the elephant foot settings but while that helped a bit, I found it too finnicky to get right. However, that tip helped me figure out my final solution.
What I ended up doing was:
- Swapping inner/outer – thanks superLight
- Making the hole slightly larger – thanks Ukdavewood
- I changed the design to add a 0.25mm fillet to the bottom side (inspired by the elephant’s foot suggestion from Uhl and the fillet idea from Wsquared58).
- Setting small perimeters to 20% speed
- Globally I turned off reduce infill retraction
Doing this, a 1 mm hole results in a 0.6 mm hole that is clear all the way through a 1.5 mm thick panel which is close enough for my application. I also tried this same approach on a sample with even smaller holes and while I didn’t measure them accurately, I would guess they are as small as 0.25-0.3 mm and clear through.
While I feel that the octagon solution (thanks zentenro) is an excellent idea I did not try it due to the sheer number of holes I have (100+).
As a side note I wish you could set the inner/outer setting using a modifier because switching this setting on the entire model gave me a different problem where the outer wall of the object (which has a 2.5 mm fillet) failed on the overhanging edge, so I sliced the outer “wall” off my object in Fusion and just printed them as separate pieces aligned together. That way I can have outer/inner for the holes and inner/outer for the slight overhang on the object’s outer edge.
Did you check the Precise wall box under Quality tab in Bambu Studio? I have always wonder if that works but haven’t had a need to use it so far.
I once ran into a situation that I wished for the ability to set wall order usig a modifier, but forgot to make a feature request. Since you now also ran into the need, I would let you have the honor 
of making a feature request for it.
yall need to turn on polyholes, too.
Saw your request for the feature and added my support.
In the meantime I wonder if using a modifier around the hole and check the ‘Precise wall’ box in the modifier will help to avoid the need to split your model into two pieces.
Normally walls are printed slightly overlapped to ensure a strong bond among them. The side effect is that the wall that’s printed later in the printing sequence can be affected and be less accurate.
Enabling the Precise wall option is supposed to have the walls printed cleanly of each other and thus more accurate, even though the bond among the walls can be less strong. The printing order of walls should matter less when this option is turned on.
Maybe I’m missing something but I do not see a Precise wall option. This leads to another feature request I plan to make - searchable settings!
There is that little magnifying glass to the right of the profile selection in the “Process” section of the prepare tab. It does exactly that.
EnoTheThracian, do you mean this magnifying glass? It only searches your parts for a named part. I want to search for a setting like Spiral vase (I know that is a setting but I have zero clue which settings tab it is on)
“I think you need to be in Global, rather than objects to see it”
Yeah that appears to the the case. That is really really silly!
However, now that I know about this “limited” search it does mean that I was correct there is no Precise wall option.
Thanks for the tip with the part/object search when in object mode 
I wasn’t aware of that.
As for the print setting option, there is precise wall:
Is this perhaps an X1 feature. I cannot find it at all on my P1S
There should not be any differences. But you may need to try to scroll up using the mouse wheel. It is just above the Precise Z height. Or shorten your search term to “Pre”.
Nope, definitely not there. This is all I get under Precision
For reference, I’m using Version 2.1.1.52
Did you enable developer mode in the preferences? Since that is all I use, I sometimes forget about there not being all settings available without it.
Edit: Not to be confused with the printer developer mode. Point 5 under improvements since 1.7
https://wiki.bambulab.com/en/software/bambu-studio/release/release-note-1-7