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Hey everyone,
I am currently recalibrating my printer after.not using it for a while. When doing a flow test I noticed these blobs forming in the middle of the circles.
AFAIK these are often caused by moistures in the filament. I already dried the filament at 50°C for a couple hours in the oven and the problem persists. So I guess I should simply get rid of the filament and open a new pack?
What's your assessment?
I doubt a few hours is long enough if the filament is really wet. It probably needs like 24+ hours. I would just switch to the new filament to test if that is really the problem. Then decide if it's worth trying to save the old filament.
I'm pretty sure that's caused by a 3D printer.
Now seriously, what printer is it?
You have over AND under extrusion.
Stock hotend?
If you have a PTFE lined hotend, this kind of blobbing can also be caused by bowden gap IIRC. Might be easier to provide suggestions and ideas if you added some information about what printer you have, what filament it is, and what your other slicer settings are.
Maybe something is wrong with the script generating these test prints, if you don't have any similar problems with normal prints?
In addition to the blobs in the middle of the circles, I think it looks overextruded/blobby every time it changes direction. E.g. if you look at the -20 sample, it looks generally underextruded as one would expect. Though it's also blobby around the edges, where the lines make a U-turn. Since the printer usually slows down at turns (unless your acceleration is set insanely high) this could be an indication that you're exceeding your hotends melting capacity, i.e. either temp is too low or speed is too high, so it would be interesting to know what you calibrated those values to. I don't think this is usually associated with random blobbing in the middle of the print, but could be worth checking just in case.
https://feddit.org/comment/9064639
Since people are asking all sort of things, and it's difficult to keep up with posting everything to every reply, I am simply going to add the info to a "main thread".
Might just be an effect of the circular infill pattern, esp. if done outside in. Try again with monotonic?
The calibration pattern appears to have a hardcoded top layer. Changing it in the slicer does nothing.
The calibration page lists some examples which look a lot cleaner. Also, I tried another opened filament that was stored in a closed plastic bag and the blobs are less pronounced. So the third test is going to be a fresh filament.
Wild guess here:
Maybe your hotend thermistor is failing, but not dead, cutting out intermittently, which could cause the hot end temperature to be fluctuating, thus alternatively under or over extruding.
To see if your filament is humid, raise your Z, and with a magnifying glass look closely at the extruded stream while you extrude. If wet it will be uneven and/or have bubbles.
Update:
The printer is a Prusa MK4S with stock parts.
The filament is by recyclingfabric.
I have run through all relevant calibrations in Orca Slicer and the blobs still happen but only when using these circular patterns. I've printer the bracket I designed. Need to further tune the edges but overall it seems good to me:
I did another test with a simple cube and the same top shell pattern as the test and got similar results.
I am printing at 200°C based on the following temp tower.
As for speed, I am using the Orca Slicer preset "0.20mm SPEED @MK4S 0.4":
Additionally based on the calibration test I came up with 18 mm/s for max volumetric speed. (Test result below)
