UM2 with Olson block - Blobs on first layer

[3dnerd 6]

Hi,

I have problems with my 1st layer. Sometimes it creates clear extrusion paths sometimes there are blobs, as you can see in the attached images.

 

The nozzle moves exactly through the center of the blobs (see orange line):

My question now is where do these blobs come from and how to get rid of them?

 

Edited June 27, 2021 by 3dnerd

[geert_2 556]

There might be lots of reasons for blobs: overextrusion (for whatever reason); the nozzle being too close to the bed (also resulting in a sort of overextrusion-effect); a too fine STL-file with way too much polygons which slows down the printer; material accumulating on the outside of the nozzle, and then being dropped onto the print; and probably other reasons that I don't think of at this moment.

 

I would suggest that you watch very closely while printing, maybe use a magnifying glass: most of the time you will see what happens, or you can narrow down the causes.

 

[3dnerd 6]

Hi geert_2,

as one can see in the image some parts are printed clearly without any blobs and some parts not.

So I doubt that it is a problem of overextrusion since then overall there would be more filament and not only where the blobs are.
The nozzle is not too close, I recalibrated the printbed with a sheet of paper and again, since parts are printed well it could not be the nozzle too close to the printbed.
The polygons are very simple big squares and triangles almost bigger than 4 cm!

So there must be another reason for those blobs. The only appear on the first layer.

Any further ideas?

 

[Speckles 1]

I had something similar to this recently, I am not a pro, but my print bed was leveled just a fraction too close. if you turn all your leveling screws about a quarter turn looser could help. 

[geert_2 556]

Also, check in the gcode if the "long straight lines" are long lines indeed, and not chopped-up in lots of tiny segments.

 

And watch the printing through a magnifying lens, or through cheap glasses with high diopter (these work as magnifying glasses too) from the supermarket. Then you can see if the blobs gradually accumulate on the nozzle and are then deposited, or if they suddenly erupt.

 

Maybe wet filament might also cause this, due to steam generation? Although I am not sure, usually it gives little craters and bubbles, like foam. So I don't think this is going to be the (main) cause.

 

But it still looks overextruded to me, it looks like the nozzle has been wading through the melt.

 

Some time ago I did a couple of over- and under-extrusion tests.

 

This is 100% extrusion, seems quite okay:

 

Again 100% extrusion:

 

Way overextruded: 150%:

 

Same overextrusion, seen from another viewpoint, 150%:

 

Way underextruded: 50%:

 

This brim was printed at 100% extrusion, but it is slightly overextruded due to my nozzle being a bit too close to the bed (on purpose):

 

It is hard to see for sure on your photo, but your image looks closer to my 150% overextruded tests here. So that would mean that: or you have overextrusion, or your nozzle is way too close (resulting in effective overextrusion too for the first layer), or the temp is too high (melt too liquid), or wrong settings for the filament, or worn-out nozzle, or something along that line, I think. If it was my printer, I would go searching in that direction a bit further.