[MINI] First Layer Imperfections - repetetive patterns of blobs
Hello Community,
I'd like to ask you about my first layers. I added a picture in which I have a large first layer, printing with Redline Silky White PLA but this occurs with all my filaments (I mostly testet Prusament Galaxy Black PLA and Prusament PETG).
First layer calibration is fine and I tweaked the Start G-Code for more consistend mesh bed leveling (warming up the MINDA and doing the auto leveling at the same temperature on which I performed the calibration). There are no gaps on the bottom of the prints and most of the lines are really perfect but then again there are these patterns.
In the end, most prints come out perfectly because the next layers hide this imperfection and all my top layers are fine and do not look like this at all.
I can provoke similar bad patterns if I wiggle the PTFE bowden tube so I thought it may be the bend and strech of the PTFE tube?
Details:
- happens with all my filaments
- different layer heights
- different print speeds
- changed to E3D Nozzle X V6 (great upgrade!), happened before and after upgrade
- performed unclogging procedure, fixed hotend height and replaced hotend PTFE tube with spare part
Thank you already, stay safe and have a nice day!
Ben
RE: [MINI] First Layer Imperfections - repetetive patterns of blobs
Your first layer calibration is off. The nozzle is too close to the heat bed.
RE: [MINI] First Layer Imperfections - repetetive patterns of blobs
Thanks for your reply.
I've done the first layer calibration many times and it should be fine. Going higher with Z causes the causes the filament not to stick (it will be ripped away at the 90° corners on the calibration pattern) and going lower results in a visible trail of the nozzle in the extruded line.
Your conclusion does not explain why there are many areas where the first layer is absolutely perfect and nearly glass like from above and underneath. I will print this test pattern and see how it turns out: https://www.prusaprinters.org/prints/30854-bed-level-correction-for-prusa-mini
The MINDA probe itself works as expected and I never hat a failed mesh bed leveling but I wonder if the built in Z-correction based on the 16 probing points takes place at all.
RE: [MINI] First Layer Imperfections - repetetive patterns of blobs
As a first timer I also have some trouble understanding the best first layer height. I did several tests and I managed to find a good result with good bed adhesion but i still see some patterns that I can't explain. Can someone post a picture of a good first layer?
Original Prusa Mini + Smooth PEI
Prusa Slicer 2.6.0
RE: [MINI] First Layer Imperfections - repetetive patterns of blobs
Thanks for your reply.
I've done the first layer calibration many times and it should be fine. Going higher with Z causes the causes the filament not to stick (it will be ripped away at the 90° corners on the calibration pattern) and going lower results in a visible trail of the nozzle in the extruded line.
Your conclusion does not explain why there are many areas where the first layer is absolutely perfect and nearly glass like from above and underneath. I will print this test pattern and see how it turns out: https://www.prusaprinters.org/prints/30854-bed-level-correction-for-prusa-mini
The MINDA probe itself works as expected and I never hat a failed mesh bed leveling but I wonder if the built in Z-correction based on the 16 probing points takes place at all.
Well, you wanted to know the reason, and he gave the reason. Why not accept the advice of people who have been doing this for many years?
If you have problems with adhesion, that is another question. It's pretty hard to get the first layer perfect anyway, I wouldn't worry too much about it. You can tell the MBL works because you can see the Z motor adjusting the height during the print (apart from Z hop and normal layer changes).
RE: [MINI] First Layer Imperfections - repetetive patterns of blobs
Well, you wanted to know the reason, and he gave the reason. Why not accept the advice of people who have been doing this for many years?
Of course I will follow the advice! Until I'm back at the printer I'd like to know what, given his advice, will happen to the areas that are fine right now?
I understand how moving the nozzle farer away from the bed can help with those blobs that we all can see on the picture, the bad areas. But what causes the patterns? With working mesh bed leveling I'd expect a more consistent bad or good first layer, or am I wrong?
RE: [MINI] First Layer Imperfections - repetetive patterns of blobs
Thanks for your advice, it was a low Z and I think I understand how the patterns are built: One little imperfection takes to much space so when the next line is printed it builts up these patches. Live-Z correction is working, I checked with a paperclip on the rod. Thanks again!
RE: [MINI] First Layer Imperfections - repetetive patterns of blobs
@an-prusa3d
Can you share a photo of your underside of a good first layer for reference?
Original Prusa Mini + Smooth PEI
Prusa Slicer 2.6.0
RE: [MINI] First Layer Imperfections - repetetive patterns of blobs
This is the print from my original post. The first layer looks bad but as I said: It does not feel so bad and did not affect the following layers. I tuned my settings and the disk came out great. This is Redline Silky PLA: It looks great but highlights every imperfection.
RE: [MINI] First Layer Imperfections - repetetive patterns of blobs
I've just spent the morning trying to get first layer calibration right. I'm seeing exactly what you are on the top side of the first layer. From watching how they form, I think what's happening is that the fresh track is overflowing into the previous track enough that the PLA flows out from the outer edge of the nozzle and is pulled upwards by the angled trailing edge as the nozzle moves away.
In my case I'm trying to get rid of them because I can see that they *do* cause imperfections on the downward face. Wherever a blob happens, I'm seeing that there's a break in the line. If they're concentrated enough, and near a corner, it's enough for the next layer print to warp the corner off the bed and wreck the print.
RE: [MINI] First Layer Imperfections - repetetive patterns of blobs
I have the same issue. Have been adjusting the height of the nozzle several times to check if it improves.
A few lines are going fine, then all of a sudden a line or 2 are "skipped" as no filament is extruded and then it resumes. I can clearly see a pattern of approx. 0.5-1cm. When the second layer starts, it seems the extrusion just stops and only blobs are "dropped" on the first layer. This stops entirely if I let it go to the 3rd layer.
If I adjust the z height a bit higher, the filament is no longer pressed on the bed. If I do it lower, it tends to pull or melt the previous line.
Not sure how to go about this.
See attached.
RE: [MINI] First Layer Imperfections - repetetive patterns of blobs
Hi,
you picture does not show the same issue that we discussed here. You could open a new thread, because your picture is really helpful: It shows a repetitive pattern of underextrusion every X mm of filament.
Check your extruder visually without filament. Lift Z and do some purges or use "move axis -> Extruder" from the menu and see how or if the extrusion is inconsistent.
I noticed, that the pull force on the spool side of the extruder is weak and I had some failed prints since I printed from inside an Ikea Lack enclosure, through a filament guide (top table), out of a filament dry box. The pull force gets more and more on the spool side, less material gets extruded out of the nozzle, until the spool "snaps" and gives another few centimeters of filament. This happens all over again.
It could be a clogged nozzle but your pattern is so repetetive that I think you have some other issues going on here.
Greetings