Hi there,
anyone knows why this happens ? And get rid of it ?
There is always a layer line exactly between the bottom of the box and the wall…
It does not matter which stl I use.As soon as I have an object like a box there is a layer line “offset”, as seen in the attached image.
P1S
esun PLA matte
0.16 resolution
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I have exactly the same issue…
i hope anyone has a soulition for it
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Try turning on the advanced settings on the Process line, then selecting
I’d guess this should form the exterior surface before the interior can affect it. Just a guess, though, since I’ve not had this particular problem.
Hi Ikraus,
this sounds good and makes sense.
I will try it out and let you know.
Thanks for your comment !
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Did the problem go away after changing order of walls? I have this issue and still can’t find any solution for this.
I’ve got the same issue, doing the outside walls first had little better but it was still there.
Hi,
unfortunately no. But I found an article that Prusa Slicer had the same issue and solved this a year ago.
So I opened a ticket at Bambu Lab. This is clearly a bug in the slicer.
Did you upgrade firmware for the printer before this happened? Did it use to print well before without wall bulge before? Mine used to print OK before the latest two firmware upgrades. For slicer, I did uninstall and use the very old version of it but it’s still there 
Also, is the ironing on or off? I did try Only one wall on top surface OFF, the bulge disappeared but ofc not enough good surface. So I turned the ironing on and the wall bulge is back.
I am talking to Rick from Bambulab support as well. It seems not much they can do but they’re looking into it.
Hi,
I have this issue from the very beginning of the printer purchase. This was Okt. 23.
Not sure which firmware I had, but I immediately upgraded to the latest one.
I tried ironing ON and OFF, does not make a differenz for the bulge.
BUT: I managed to get rid of the bulge, almost. You can only see it if you have a very close look at direct light. So hardly visible.
I would post my settings as a file, but its not possible here. So let me make some more tests and I will share my settings as screenshots afterwards
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Hi sidnsmurf,
Thank you. Please share the settings with us. I’d appreciate it. I’ve been struggling with this issue and tried many ways but haven’t figured the solution yet.
Hi,
sure will share it tomorrow. Need some testings on a P1P from my colleague.
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Hi all,
I did some more research on this issue and played with different settings for the bulge.
Important: I did this with the Orca Slicer V.1.9.0
I get the best results with these simple changes.
All done from the stock profile 0.20 and the Bambu Matte filament, as seen in the 1. image.
The first Image gives you an overview which filament I use and the seam settings (has nothing todo with the bulge itself. Just for reference)
The second image shows you the settings for the bulge issue. Especially the"Walls printing order".
The ironing is just for an almost perfect surface, not only on the topmost one but also on the bottom surface.(All top surfaces). This works great for me.
I also played with many more settings in Orca Slicer, but at the end of the day, these simple ones did the trick…for me.
Hopefully, someone can still benefit from it.
Btw: I had issues with warping on the edges for objects like this one.
Orca Slicer provides a really great option (Mouse Ear).
This is the new printed object without any bulge. Very clean, finally 
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Thank you for sharing sidnsmurf!
Did you try to use something other than 0.20mm. profile? (like 0.12 mm. ,0.08 mm.)
Not yet,but I can test it tomorrow and share my results, with the same settings I provided before.
From what I’ve gathered, it’s caused by the shrinkage of the top surface layers pulling the walls in. If you look at it from the side, you can see that the base layers are in line with the layers above the bulge and the layers between the bulge and base layers are kind of angling inwards. I have no idea how to mitigate the shrinking top surfaces from pulling the walls in yet.
i agree with qjo, i have the same issue and have noticed that my first layer looked to be wider then due it has shinkage and leaves the line. im trying outer/inner to see if that helps.
do you guys run aux fan off? also you open the full enclosure or close it off keeping the heat in?
So many threads about this issue LOL
I print in two variations; Quick and dirty / as perfect as possible.
No need for a prototype to be perfect or very strong…
With my old printer the issue of wall differences when the layer time or just walls changed was somewhat of a pain.
Possible to reduce or in some cases fully eliminate - but at a cost.
Our Bambu machines shine through speed and most people having one won’t even know that not that long ago we could dream about going faster than around 60 to 75mm per second.
So let me start with what is actually causing these nightmares - PHYSICS
Assume a large, rectangular box.
The bottom requires not just a lot of infill but also TIME.
This results in those outer walls having a lot of time to cool down.
The heated bed helps with the adhesion but won’t able to keep the top layer at temp if the layer time changes!
Lets say every bottom layer takes 60 seconds to print but the walls above only 10 to 12 seconds.
The cooling fan for the part can only do so much at the speed the head is wuzzing around…
Means your walls and infill will have a HIGHER temperature than those filled bottom layers
The result of all this is that the plastic extruded won’t cool down as fast while the layer below is also still rather soft.
Combined this means the actual extrusion widths INCREASES.
There is no way around physics that I know of…
So how can we mitigate this or maybe even eliminate the issue?
- Try, if the model actually allows for it, to print the outer most wall first.
This will provide the least possible surface distortion from different plastic temps hitting it as there is nothing either side stopping it. - Find a better matching overall speed.
Sounds counter-productive, I know…
Reason for this is that is you, for example, reduce the speed for walls quite a bit the squishing effect is minimised/equalised a bit. - Match your extrusion temp to the ACTUAL performance of the filament and your set print speed
With those three measures I was able to get near perfect prints on my old printer.
The main key here is the extrusion temp - you want is as low as possible to check how much this issue shows up.
By low I mean just above loosing a good layer bond.
Then print the tiny cube again but at 5 degrees hotter.
Keep going like this and keep the prints lined up for comparison, mark them for Justin…
You will find that a certain temp things turn either very awful, that the plastic is overcooked and brittle OR that this wall difference minimises/maximises.
Depends on the type of filament really.
The temp where thing turn out best is the one to hone in to.
Why ?
Because at this temp the extruded plastic shows the best flow properties.
That can be being rather soft OR just hot enough to be printed - only checking gives you the answer.
On my P1S however I found a rather interesting way to cheat this problem away (almost fully even on otherwise impossible prints).
In order to try this out you first have to forget everything you ever learned about calibrating your filament…
As we established the culprit is the extruded plastic, time and temp.
What IF we could make the plastic print without any excessive squeezing ?
I know… Then we find that our walls and infill struggle between the bond between the horizontal lines is too weak…
After all, there is a reason we won’t print 0.5mm layers with a 0.4mm nozzle…
Ok, you forgot everything already but have a backup stored in the back of your mind, let’s get going…
Set all filament parameters to their defaults, preferably by starting a new profile for this test…
Print some test cubes or a small temp tower to find the best print temp that still provides a good layer bond - then increase this value by 8 degrees.
Do a case mode cube, measure the wall and note the result somewhere.
Do the math to calculate the correct flow rate in order to match the printed wall to what is set in the print profile.
Usually this value will be quite a bit higher than the default 0.98.
Now print a small test cube, 15 to 20mm is plenty here and 5mm high shall do fine for a 0.4mm nozzle…
Use 100% rectilinear infill, no top layers, one wall and no infill combination please.
You will most likely see a cube coming out that has a really messy top…
We all know how to fix this but we forgot…
So now we go and adjust our flow rate until this cube comes out with a PERFECT top surface, smooth, no build up, no saw tooth ends…
Check using a magnifying glass or you phone’s camera!
Go lower on the flow rate until you see a very gap between the infill lines appearing.
You can do this in 0.1 steps from the vase mode value you established.
Now that you have this tiny gap increase the flow rate in tiny increments, like 0.05 or 0.02 once you get really close to solid.
With this value established print the cube again but now set 4 wall loops and 4 top layers.
The surface should come out smooth and with no visible gaps between the lines.
YES, you will see the difference between the lines but this ‘line’ should neither be a gap nor a ridge.
You now established TWO totally different flow rates that are both equally perfect and equally bad.
The vase mode value is a keeper for when we want to print in vase mode.
The second could be a keeper if you mostly print fully solid prints…
BUT: We can make it a keeper for almost all prints we encounter
How ?
We now have a profile that produces a clean infill and clean walls but where our extrusion rate could be seen as way too low.
Try it
The model should still be strong, should still perform…
But the dimensional accuracy might be off - a bit too low.
Big question is HOW off are we here ???
Take you failed box with the enlarged walls…
Assuming the flow rate was set ‘correctly’ you have a certain difference.
If the bottom is 12cm the walls might be 12.1 or even 12.18mm wide.
Since you created a new profile print two test cubes or large enough size so the wall problem is clearly visible.
Measure both and note the values.
The one with the original flow rate setting will have the larger values.
Subtract the values from the other cube with the settings we just established to get the difference.
Now print a really large box, like 15 by 15cm and 1cm high- no infill, no solid layers but make it at least 3 walls, better 4.
You end up with a flimsy thing, so take the plate out while still warm and measure the dimensions.
If you only have small calipers print the thing small enough please
Three values now, from the two small cubes and this big one, none will be a perfect match.
Adjust the multiplier for the XZ compensation so the huge 4 wall print will come out with a really close fit - using the new profile with the low flow rate.
Print a small one of 10 or 15mm and check if it is still a good enough match.
Last but not least: Do the same for the hole settings.
You might be surprised how clean your models come out and how easy supports can be removed now
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