As you can see on the pictures, it is always the base part of the pot. So the part where there is infill. It changes after the prints get to the wall.
I print with PLA on an A1.
What I tried so far:
Different filaments: eSUN pla, copymaster3D, Bambu lab basic
All kinds of different settings:
Inner / Outer / Inner
More or less infill
Faster and slower printing
Change bridgin speed
Downloaded OrcaSlicer and checked the “Don’t slow down on outer wall”
I even tried to print the WHOLE print on the same speed, tried this on the normal speed and on a slow speed
Even tried to print the base WITHOUT infill
Some how I keep getting the same result… I don’t know what could help anymore!
(yes I also tried printing with default settings for Bambu PLA Basic, also the same result)
Welcome the world of problems we wouldn’t have without Bambu printers !
Ok, jokes aside, let me explain the problem at hand:
The base has a certain thickness and infill.
Once the top layer of the base is done only the walls and their infill remain.
A significant drop in layer time.
In theory this should not matter and does not matter with most printers and slicers out there - at least not to this degree.
The filament heats up and the flow rate and print speed affect the time it spends in the melting chamber.
Have a glue gun and sticks ? Great !
Check what happens once the heating light goes off.
The thing is ready for use now - but using it NOW is much harder than a few minutes later.
And if you need a lot of glue you notice how the gun might struggle to heat it up fast enough.
You face the opposite problem.
From having to pump at a fixed rate the hotend has to do it now at a different speed, affecting the filament properties.
Sadly Bambu did not stop here and somehow managed to affect the actual path of the extrusion as well.
The slicer/printer can ‘compensate’ in two ways.
by slowing things down do match the flow/pressure changes so they won’t have a severe effect - not a favour for fast printers…
by slightly adjusting the extrusion path for the walls.
And that seems what Bambu is in favour of, not sure is just slicer based or in the firmware.
If you check the slicer preview you will find corresponding speed/flow rate changes in the affected layers.
In Studio 1.9.5 you can try the discontinuity feature in order to mitigate the issue a little bit.
In reality though only adjusting the speeds so the flow rate changes and layer time changes are less severe helps.
I tried to fix the issue through proper filament calibration but it is impossible to get rid of the effect for good.
On models with flat walls you can nicely observe how the affect changes from the start to the end of the extrusion line for the wall.
So really no chance to calibrate things that keep changing on the go…
We can only hope Bambu addresses this issue in a future bug fix as it is going on for a very long time now…
For me the striking part is that in many cases the defects are far too severe to be possible without a change for the actual path the nozzle takes.
I had models with a difference of over 1mm - and with clear stepping indicating the path changed to a larger or smaller circumference…
I tried lowering the bed temperature from 65 to 50, but same result. Also tried lowering it more to 40, but that also did nothing.
I calibrated the printer, came at a k factor of 0.02 for Flow dynamics which I set for the filament. And a calibrated flow ratio of 1.029 (vs default of 0.98).
But that changed nothing as well. Keep getting the same problem
My first tought it had someting to do with temperature, or under/overextrusion.
Temperature as the plastic will shrink under certain conditions. That why I also tried printing it ALL on the same speed. In the hope that would make a different.
As you say it might have to to with bambu changing the extrusion path, I will do some more experimenting. Maybe using a different slicer. Do you know if there is a bug report?
How would I see the actual nozzle path? As I seems the slicer preview does not show it correctly. Or is it just someting you can see in the actual end print?
The thing that thought it might be a “me” problem is because when I look at prints of other people most of them are fine (I saw some other posted screenshots where similar problems where seen.
Do you know where I can find the “discontinuity feature” as I can not seem to find it in Bambu studio or Orca slicer?
You find it at the bottom of the Quality settings, with the advanced tab active ay least.
There is no preview for what the firmware might do different to the slicer preview.
In severe cases though you can see that the path is off by way more than what just the extrusion would allow for.
Might be worth to do a temp check, either with probes or test prints.
If the thermal grease dried out you never get correct readings.
The heater might not be able to transfer heat properly and the sensor gives a wrong temp reading.
I don’t know exactly how it should look like, but as far as I can tell it looks good?
Only the little spikes are not completely straight.
I also tried to make a test print with straight walls instead of with overhang as in the start post. It was a little bit visible but by far not as extreme as with overhang.
It’s such a bummer because all the other print look amazing! Even with small clearing everything looks perfect. Just not for these kind of prints.
I have the issue again now that I have to print a bunch of custom bottles in vase mode.
Only at snail speed the transition from bottom to just wall is air tight.
And while swearing a lot and venting my frustration I remembered that I never had those issues on my old printer.
Then it hit me ! A feature I used so often that I did not even realise Bambu does not have it anywhere…
For my old printer it was done basically automatically.
The one before that required me to specify the amount of layers from the first one until full speed is reached.
With no easy way to this through Studio I had to cheat…
Created a print profile where the default speeds were correct at the ludicrous setting.
Started the print as went to silent speed right away.
The single wall loops started at layer 11.
At layer 9 I went to normal speed, layer 12 sport and from layer 15 onwards ludicrous.
Funny enough the bottle bottom came out air tight…
For PLA I don’t have this issue, at least not to a degree I would worry about.
PETG and ABS though …
IMHO it is related to the ‘lines on walls’ issue where a perfectly flat wall gets messed up when the layer time changes too much or there is sudden flow rate changes.
In the latest Studio version, 1.9.5.51, most print speeds are have been reduced by up to 30% compared to the defaults for the 1.9.3.
Probably in order to minimise some of those issues.
IMHO though it comes down to the calculations for ramping, PA and pathway compensation not being accurate.
Pathway compensation? What’s that ?
Take a star - the inner corners and the outer corners are significantly different in terms of how much filament has to be extruded in the corner and by how much, if any the extrusion path has to be modified.
Keep in mind that for outer walls the filament can only be pushed OUTWARDS.
Pathway compensation ensures that where is not enough room for the filament room will be made.
Like by making the inner loops for an inner corner much rounder - it gives more room for the filament when the outer loop has to get around this kink.
Feel free to check the g-code of an offending model for signs of extrusion path correction - I don’t have the time and patience.
With every new ( main) studio version we find new settings or changed settings aimed to reduce our issues.
But it is a bit like topping up the oil in your car’s engine every morning…
It does work and keeps the engine ticking…
Fixing the oil leak though would be the better solution…
