Update: I think I figured it out! See below.
Can anyone help with my blobing issue?
For a while now I’ve been trying to figure out why I keep getting these blobs on my prints and I finally figured out the reason behind it but I’m not quite sure how to fix is. Basically the printer primes, moves and prints, stops, retracts and then moves again, like it should. However, between the stop and retract parts, that’s where the blob comes in. It prints just fine but in the split second after it stops and before it retracts, it’s leaving behind these little blobs. I have already turned coasting on and the problem still persists. I’m using PLA+ material. The manufacturer suggests 205c-215c for printing but I’m currently running at 200c (according to the printer). Any other ideas on how to fix this? Is there an option (I use Cura) to make the coasting start sooner? Will running it too cold cause this issue? It seems to print fine other than these blobing issues. Any help is appreciated.
This happens when a layer ends and it moves to a new layer. From what I understand it’s not possible to fix/remove by FDM design.
However I read that S3D propose to align them all at a specific place.
Actually with Slic3r you can change the “Seam position” in “Layers and perimeters”.
And in Cura you can play with the “Z Seam alignment” and “Seam Corner Preference”.
@Julien_Dodokal yeah but on a round object, there aren’t any corners to hide the blobs in. This was printed on “random”. Maybe I’ll try a different setting and see if it’s any different.
@Dave_Benson increasing retraction probably won’t help as it’s blobing BEFORE it retracts. And no, it’s not accumulating anything on the nozzel. I don’t think it’s over extruding but that’s a possibility. Maybe there is just too much pressure at the nozzel. I’ve also wondered that maybe it’s happening because the temp is too low. If it’s creating too much pressure in there it could be because it’s too hard to push the plastic out. Maybe raising the temp could help.
never been able to work out why i get it too… and i have spent ages on this.
This definitely looks like a retraction issue, you can test this by keeping the starting point the same and printing a cube, if you see a straight line of blobs, then it is doing the blobs consistently, i.e. when it performs a move in the z-axis. (which should rule out over-extruding, and temp too high.
Then knowing it’s oozing during the Z axis move, it is a matter of playing with retraction speed, distance, and coasting.
@Dave_Benson because I sat with my face just a few inches away and watched it. Regardless, I think I corrected my issue. See below.
@Kevin_Danger_Powers how much did you increased it?
Ok so I think I figured out my issue! I increased the temperature. Why? Because the filament was still oozing out even though coasting was on. This led me to believe that there was too much pressure in the nozzel when it stopped printing. I had an idea that increasing the temperature would soften the plastic slightly and allow it to flow more freely. Once I combined having less pressure with the coasting feature, it sure cleared up!
https://lh3.googleusercontent.com/jRX2suLnbFR2lxBP1xZlKrEOxtmN1DyvvodNEFqqICakWGBLVqvkPlMSC0dRRH5P0cSZcNKFNgo
@Cristian_Nicola I increased it to 205c instead of the 200c I had it at. I tried 210 but it was getting a little droopy.
Edit: Looks like you already tried it and posted your reply while i was writing this. Keeping the comment as it could help others as it did for me. </end edit>.
If you’re using Cura there are a few settings you could look at. Coasting for example (experimental feature, you have to add it in settings)
It stops the extruder a just before the end of the layer and relies on the build up pressure in the hotend to extrude the very last part of the layer. Minimizes the “squirt” you get t the end of the layer due to the build up pressure.
You could also test retraction on layer change (although it seems you already have?)
@PrintinAddiction well like I said above, the blob is happening BEFORE it’s retracting. There was a brief period of time after the move and before it retracts where the blob was coming from. Retracting more wasn’t fixing the issue and I already tried that.
@Kevin_Danger_Powers So you are getting the blob while it’s moving in the X or Y? That is surprising that your building up that much pressure and retraction doesn’t help. But it seems like you found the culprit, and fixed it. Didn’t mean to reiterate what was already did, but sometimes I find that I thought I had checked something thoroughly but missed a small part or step.
How old is the PLA you are using? Do you keep a dry container?
Plastics absorb moisture, this moisture becomes steam in the molding of plastics and causes unregulated flow.
I keep it in a plastic fastener box (food container) with silica gel absorbing material (Aliexpress).
@Jakab_Gipsz it’s about a week old. It’s in good shape.
@PrintinAddiction no, not while it’s moving. It’s between printing and retracting. So it prints a line, stops, retracts and then moves. There is a brief pause between stopping and retracting. THAT’S when I was getting the blob. Apparently there is a very short delay after it stops and before it retracts. Because it sits there for fractions of a second before retracting, it was still under pressure and would leave a blob.
It’s stops but is not performing a Z-Axis move??? Then why does it stop? To retract? I think your eyes are deceiving you, but hey, you fixed it so all is well.
Usually on most printers, the head doesn’t stop moving in the X&Y unless it is performing a Z move, or some custom G-Code, filament swap, head swap, etc…
I started having similar to these but randomly spaced blobs after adding the part fan. The head temp fluctuations lead to underheating periods followed by heated squirts from the pressure buildup. Also fixed that rising temp for 8 deg (amplitude of fluctuations). Need to recalibrate with the fan, but obviously the effect will depend on the part’s geometry (scattering the blown in air differently).
