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Anyone knows what are these small corner blobs and how to get rid of them?

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Image-1.thumb.jpg.22d65539910c68105cb795e5654e7a9c.jpg

This is a standard 20 x 20 mm calibration cube (from thingiverse) but scaled height to 60 mm in Cura 2.6.2.

Vase mode. PLA @ 0.2 mm. 70 mm/s

Printed to test different temperatures. The problem occurs even with stable temperature as the shortest cube shows (that one was printed at 215 C)

Retraction was ticked on at 25 mm/s. But I don't think it retracts in vase mode anyways, right?

The problem gets better with more height as the cubes show (bases on right, tops on left of image).

Image-1.thumb.jpg.22d65539910c68105cb795e5654e7a9c.jpg

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There are many kind of blops and sources for it IMO

- Temperature too low, increases the pressure of the filament on the hotend, so when a stationary movement occurs, the filament slips out making a blob. Because on it's semiliquid state it tries to find places to go. The fix for this is to print even cooler, or print slower. Printing too low will allow the filament to not be able to drip, since will be less viscous. Printing slower will decrease the pressure on the hotend making less pressure that can 'slip out'.

- If you have too much pressure, a fix is to wipenozzle while retracting, so the pressure blob it's part of the print, instead of a stationary blob. This I think is possible on Cura 2.6 (don't I don't use it so). On S3D is quite easy to activate and control.

- If there's a stationary retraction, something that UM2 with ultigcode does quite a lot because it uses a separate gcode to retract-recover (so it can't do retraction+move unless you use reprap flavor), you need to change the settings to allow combing for example so the end of a loop the motor isn't extruding and the blop becomes part of the end of a loop (pressure becomes part of the print instead of a blop).

All this adjustments are filament-brand based, and sometimes change from color to color (even same brands have different viscosity). So you will have to adjust accordingly.

The easy fix, the no brainer fix, is to print cooler + slower. There's always a 'neat' spot where both work great. @ultiarjan has a nice test for that, I never used it since I do it by eye, but I think is one of the best tests out there. Is at:

https://www.youmagine.com/designs/quick-temperature-fillament-test

Oh wow even Ultimaker made a video out of it:

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I think it is a temp problem, try to print a temps starting from 205 and go up to 215.

This would also explain why it gets better the higher it goes, it gets influenced less and less by the heat of the printbed.

Kind regards,

Job van Gennip

 

Thanks for your reply.

I did initially think it was a temperature problem, but it appears to be present regardless of the temperature of the nozzle.

The tallest cube on the right is temperature graded (z height is 60 mm in total, it was printed with an increase in 5 degrees every 10 mm, as marked). The one on the middle has its base at 215 then at 10 mm 195 degrees, then increasing by 5 degrees every 10 mm.

Then the short one in the left was printed on a fixed temperature of 215 degrees.

The artefact is present in all of them.

To note, i have laid them in the same printing orientation; their build plate side is on the right side of the photo.

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What printer are you using?

What's your print speed?

Do you hear a constant clicking sound as its printing?

 

Thanks for your reply.

An Ultimaker 3 Extended.

they were printed at 70 mm/s.

If you mean the filament clicking sound then no. This is a fresh spool of filament and the same problem occurs with other spools. I think it's not the filament.

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What printer are you using?

What's your print speed?

Do you hear a constant clicking sound as its printing?

 

Thanks for your reply.

An Ultimaker 3 Extended.

they were printed at 70 mm/s.

If you mean the filament clicking sound then no. This is a fresh spool of filament and the same problem occurs with other spools. I think it's not the filament.

 

No the constant clicking I meant is from the z axis when in vase mode.

But yeah, as Gr5 says 70mm/s is quite fast. So lowering your speed can help.

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What printer are you using?

What's your print speed?

Do you hear a constant clicking sound as its printing?

 

Thanks for your reply.

An Ultimaker 3 Extended.

they were printed at 70 mm/s.

If you mean the filament clicking sound then no. This is a fresh spool of filament and the same problem occurs with other spools. I think it's not the filament.

 

No the constant clicking I meant is from the z axis when in vase mode.

But yeah, as Gr5 says 70mm/s is quite fast. So lowering your speed can help.

 

Yes I do hear constant clicking. Never associated it with vase before but now I can't un-hear it :p

What does that indicate?

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Generally the z axis only moves when it changes layers. It will go down to the specified layer height then start the next layer.

But when in vase mode the z actually constantly moves downward so you end up with more of spiralling layers. This gives the clicking sound as the z is making tiny movements downward.

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I've seen those blobs quite a bit. Just lower the speed - that's the easy way to get rid of them.  Try 30mm/sec.

 

Unfortunately that didn't help.

I'm starting to think the problem is in the stl itself.. could you kindly give it a try when you can? Here is a link https://www.thingiverse.com/thing:953162

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Generally the z axis only moves when it changes layers. It will go down to the specified layer height then start the next layer.

But when in vase mode the z actually constantly moves downward so you end up with more of spiralling layers. This gives the clicking sound as the z is making tiny movements downward.

 

But the clicking i'm hearing is about once every second (printing at 30mm/s to test gr5's suggestion). Wouldn't a constant move give a much higher frequency (multiple per second) clicks?

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Well it's interesting that it only happens on the corners. I think maybe it is overextruding and only on the corners does the filament leak out.

Ah!! I have a new theory I like. This is spiralize?

Spiralize is weird. In non-spiralize mode if nozzle is .4mm and shell is .8mm it will make two passes. But in spiralize mode it will try to do it in one pass. So it will doubly extrude to get the .8mm shell and that's a LOT of pressure.

That would make sense as to why it sometimes is just too much pressure and it occasionally leaks out suddenly and makes a bump.

1) What printer is this?

2) What filament size does your printer use (1.75 or 2.85)?

3) What is your nozzle size set to in cura and does that match your machine?

4) What is the shell width in cura?

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Well it's interesting that it only happens on the corners.  I think maybe it is overextruding and only on the corners does the filament leak out.  

Ah!!  I have a new theory I like.  This is spiralize?

Spiralize is weird.  In non-spiralize mode if nozzle is .4mm and shell is .8mm it will make two passes.  But in spiralize mode it will try to do it in one pass.  So it will doubly extrude to get the .8mm shell and that's a LOT of pressure.

That would make sense as to why it sometimes is just too much pressure and it occasionally leaks out suddenly and makes a bump.

1) What printer is this?

2) What filament size does your printer use (1.75 or 2.85)?

3) What is your nozzle size set to in cura and does that match your machine?

4) What is the shell width in cura?

1 & 2 )Ultimaker 3 Extended, default 2.85 mm

3) nozzle size set to 0.4 (in print core setting), line width 0.35 (default profile)

4) I believe that's the wall thickness under "Shell"? Its 1 mm.

One other thing, it seems this problem is appearing in other non vase mode prints as well. Here's a dual extrusion benchy i did yesterday in 0.2mm layer height, innofill pro (black) @ 215 C and generic PLA (golden) @ 205 C. I have decreased printing speed to 45 mm/s. Enabled prime tower and ooze shield took a little more than 5 hours. Not the best benchy.. but for the sake of this thread, it also has two of those blebs in a corner (front hull): Image-1.thumb.jpg.f3af8fe96f027dbd047b32f7029f9b92.jpg

I'll print the cube in non vase mode and see if it makes a difference.

Thanks for your kind assistance.

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Ah! That's almost certainly it then. It's trying to print a 1mm line width out of a .4mm nozzle. Spiralize is weird that way. I would put a larger nozzle on there. You can get a .8mm core from ultimaker or you can get a 3rd party version from shop3d.ca that lets you change nozzles.

The problem on benchy is similar: overextrusion or not viscous enough (too hot). The pressure builds up and sometimes it just squirts out and makes a blob. There are many causes - not just spiralize. It could be that you are just printing too fast and pressure builds up too much. Or maybe too hot - cooler filament is less likely to spurt out the side of the crack along the nozzle. Or at least it only spurts out a tiny bit. I've never used innofil but 215C sounds too hot for the UM3 if it's PLA. The UM3 nozzle temp should typically be 10C cooler than that of UM2 or other printers.

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Ah!  That's almost certainly it then.  It's trying to print a 1mm line width out of a .4mm nozzle.  Spiralize is weird that way.  I would put a larger nozzle on there.  You can get a .8mm core from ultimaker or you can get a 3rd party version from shop3d.ca that lets you change nozzles.

The problem on benchy is similar: overextrusion or not viscous enough (too hot).  The pressure builds up and sometimes it just squirts out and makes a blob.  There are many causes - not just spiralize.  It could be that you are just printing too fast and pressure builds up too much.  Or maybe too hot - cooler filament is less likely to spurt out the side of the crack along the nozzle.  Or at least it only spurts out a tiny bit.  I've never used innofil but 215C sounds too hot for the UM3 if it's PLA.  The UM3 nozzle temp should typically be 10C cooler than that of UM2 or other printers.

Ok, I think we are getting closer to the answer here..

I just printed this test cube with the following settings:

Image-1.thumb.jpg.81d1e9fbe569c6f617599d5439843ba1.jpg

Generic PLA @185, 35 mm/s

Z Seam Alignment (shortest) This is new this time and i think its the key here..

LAyer height 0.2 mm, wall thickness this time 0.4mm

Decreased travel speed, print acceleration and print jerk (not sure if they affect anything in vase mode?)

Enabled retraction and retract at layer change. Ret distance = 6.5 mm, ret speed 25 mm/s, retr min travel 0.7 mm

Also minimum layer time was 0.

It seems to me that the Z Seam Alignment is causing the blobs to concentrate on top of each other for a couple of layers, then in the next couple of layers they move to another corner (the other corners get clean, only one has blobs) then the location of the lumps of blobs change to a different corner and so on..

I'll try to specify a location for the z seam alignment and update you.

Thanks.

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There are many kind of blops and sources for it IMO

- Temperature too low, increases the pressure of the filament on the hotend, so when a stationary movement occurs, the filament slips out making a blob. Because on it's  semiliquid state it tries to find places to go. The fix for this is to print even cooler, or print slower. Printing too low will allow the filament to not be able to drip, since will be less viscous. Printing slower will decrease the pressure on the hotend making less pressure that can 'slip out'.

- If you have too much pressure, a fix is to wipenozzle while retracting, so the pressure blob it's part of the print, instead of a stationary blob. This I think is possible on Cura 2.6 (don't I don't use it so). On S3D is quite easy to activate and control.

- If there's a stationary retraction, something that UM2 with ultigcode does quite a lot because it uses a separate gcode to retract-recover (so it can't do retraction+move unless you use reprap flavor), you need to change the settings to allow combing for example so the end of a loop the motor isn't extruding and the blop becomes part of the end of a loop (pressure becomes part of the print instead of a blop).

All this adjustments are filament-brand based, and sometimes change from color to color (even same brands have different viscosity). So you will have to adjust accordingly.

The easy fix, the no brainer fix, is to print cooler + slower. There's always a 'neat' spot where both work great. @ultiarjan has a nice test for that, I never used it since I do it by eye, but I think is one of the best tests out there. Is at:

https://www.youmagine.com/designs/quick-temperature-fillament-test

Oh wow even Ultimaker made a video out of it:

Thanks for your informative reply.

I'm leaning more for it being a z seam. as the blobs become align on top of each other when I click the Z seam alignment to shortest. not sure why it shows sometimes and sometimes don't..

they are there when printing at low speed and low temperature. I dont think its that in my case..

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