Strange layer peeling : underextrusion ?  

RE: Strange layer peeling : underextrusion ?

Bed adhesion (layer one plastic peeling up) is common when there are oils on the bed. For the PEI sheet, soap and water are best. For Powder Coated sheets Prusa recommends using only alcohol as a cleaner. 

A clean PEI sheet will result in PLA sticking down very well, and requiring effort to remove. Thin layers of PLA should pull off similar to what masking tape feel like lifting off clean glass. 

And rule #1, do not touch the PEI print surface with your fingers ... that's the best way to cause problems.

And last: did you follow the E3D-V6 nozzle change instructions?  If not, look them up and repeat the nozzle install.

RE: Strange layer peeling : underextrusion ?

also the .25 nozzles are a lot more critical in setting your live z as are thinner layers

RE: Strange layer peeling : underextrusion ?

Hello and thank you for your answers ! 

Tim I followed theses instructions for the Nozzle but do you think it might have moved due to print vibrations ? 
I have printed for about thirty hours with .25 nozzle before having these underextrusion issues. 

And the "no-layer scratchy texture" never happens on the first layer. My first layers seems always good...

David, do you think it might be the nozzle too close to bed ?
I have made some tests yesterday with live z, but nothing changed so far.

RE: Strange layer peeling : underextrusion ?

It might also help if you let folk know what the "correct settings for you 0.25 nozzle" you are using.  Maybe they aren't as correct as needed.  But a plug while printing the first layer hints at either a idler tension issue, or something from the last plug still rattling around in the nozzle, or an assembly issue.  Did you do a cold pull, replace the nozzle, or other cleaning?  Did you follow the E3D-V6 procedure for removing and replacing the nozzle? Improper set of the nozzle can cause what looks like a jam. Are you using an enclosure?  Are room temps around 25c? 

RE: Strange layer peeling : underextrusion ?

My firsts layers are the only one always clean ! 🙂
About correct settings : my bad, I meant default settings of the last version of Slic3r for my nozzle, printer and detail level (0.07 here).

I did a cold pull and an overheat of 280° for 5 minutes to melt an eventual clog.
For the Nozzle replacement I followed this :

I don't use enclosure and the room where I print is quite hot these days : about 30 degrees, but firsts issues happend when it was about 27. 

RE: Strange layer peeling : underextrusion ?

I removed and replace the Nozzle with E3D-V6 procedure and cleaned bed again tonight but no changes.
I observed that the wrong behavior always happens exactly at the same moment of my test print, therefore exactly at the same place of the piece.

RE: Strange layer peeling : underextrusion ?

First layer for a 0.25 nozzle will look the same as a first layer with a 0.4 nozzle; just has smaller tracks.   Is the 0.25 nozzle brass? Or something exotic like hardened steel?  Brass has good heat transfer, other materials less so and often need more heat...

Does the extruder click when this is happening?  Is the extruder fan running?  Does the jam happened about the time the print fan comes on?  Do you see any unusual variation in nozzle temp while printing?

If a certain print fails same place multiple times, I'd also look carefully at the part.  It's also possible something in your slice settings isn't working and leads to underextrusion.  

By any chance did you keep the filament that broke? The part that was stuck in the extruder? Or a photo of it?

RE: Strange layer peeling : underextrusion ?

The Nozzle I'm using is this one (in 0.25mm):
https://shop.prusa3d.com/en/i3-accessories-mk3s-mk25s-etc/89-e3d-v6-nozzle.html?search_query=nozzle&results=13#

The extruder is indeed clicking when this happens !
I remade a test and the fan is on, no wierdness observed in temperature.

I didn't kept the filament, but I clearly remembered it was dented, like chewed by the extruder.

I also noticed something strange :
Yesterday I worked upon Z Live adjust and found a setting of -660 to be good. I made a first layer calibration test and launched my failed print without a problem with first layer.
Today I tried to launch a print but no filament was extruding and nozzle was clicking before I made any change. I updated Z Live setting from -660 to -640 and I could launch my test anew, with extrusion for first layer.
I turned the printer off, then later turn it in again for another test and same situation : the nozzle were now too low to extrude. It doesn't look like it had moved, like heatbreak unscrewing or something...

It's like my nozzle height isn't stable. I hunt for loose screws but found none.

RE: Strange layer peeling : underextrusion ?

There's  a nasty "issue" with the MK3 and MK3 S PINDA that it is temperature sensitive.   Run a PID calibration of the PINDA.  It's in the calibration menus.

Then, add these lines in the Printer Settings custom G-code STARTUP in slicer  (replace the existing G80 command): 

; soak PINDA then level
G0 X50 Y50 Z0.15 F3000; this is a good PINDA heating position
M860 S35 ; wait until PINDA is >= 35C
G80 N7 R5; mesh bed leveling

RE: Strange layer peeling : underextrusion ?

Posted by: Tim

[...] G0 X50 Y50 Z0.15 F3000; this is a good PINDA heating position

Just be aware of the nozzle temp if you're going to hover near the PEI print surface. I only pre-heat my nozzle to 160C, but still make a point of moving it away from the print area after I noticed small divots forming under the nozzle while heated.

RE: Strange layer peeling : underextrusion ?

Yes, I only move to that location when my nozzle is at 185c.

RE: Strange layer peeling : underextrusion ?

Thank you for your advices but I'm beginning to despair...
I tried PINDA calibration and code.
The day I did this, I tried an impression and had the usual failure but the nozzle was high enough to print first layers at least. And I could adjust my Live Z precisely for first layers before that.

I shut down my printer and when I tried another print the day after : again the nozzle was touching bed when bed levelling and way too low to extrude after.
I can't figure out why it acts like it was lowering by itself ?!

RE: Strange layer peeling : underextrusion ?

One last idea: have you done a First Layer Calibration using the menus?  The zig-zag pattern that ends in a small coupon?    Doesn't matter how good the result is, just that you ran it to completion.

And the PINDA thermistor cal is now called Temp calibration (I think).  Be sure you have run it.

RE: Strange layer peeling : underextrusion ?

Hello,

Thank you for your answers !

I have done First Layer calibration many times to find the right Live-Z and did the Temp Calibration two times to be sure.

I have changed the nozzle from 0.25 back to 0.4 but encounter the same under extrusion issues.
Fans are on, temp is consistant, I tried prints with Slic3r profiles from 0.15 to 0.05 of serveral different models, but still : clicking and underextrusion...

It looks like it happens most of the time when printing an horizontal flat zone of the object, like a flat base.

RE: Strange layer peeling : underextrusion ?

An option to try to confirm if the issue is only related to filament flow is to go to the filament settings in slicer and set the extrusion multiplier to a higher value (i used 1.1 and had success after under extrusion issues, but this was just me setting it to the highest recommended setting to see if it achieved anything). i have an open thread here, and in firmware to see if there is any feedback - was planning to contact support if i don't hear much from those threads.

RE: Strange layer peeling : underextrusion ?

The first time I changed my nozzle, I did the auto-home and then Z calibration and the nozzle was too low and scraped the bed.  I realized that at some point the PINDA sensor had shifted higher and was just too far from the bed, and once that was fixed it all worked great  Since then, each time I change the nozzle I've checked that first before running the auto-home and Z calibration.  I lower the nozzle to just touch a piece of paper on the bed, then adjust the height of the PINDA sensor so it just fits the middle of a zip tie under it (see the pre-flight check in the MK3S installation process for details).  Each and every time, the PINDA sensor has been significantly too high - I've no idea why, but it's been consistent and it is easy enough to fix.

RE: Strange layer peeling : underextrusion ?

I tried to increase the extrusion multiplier to 1.1 and it actually helped !
I could print a little longer before the happening of underextrusion :

I double checked PINDA sensor but it didn't move, still a "zip tie height" above bed. 🙂

I also noticed something :
Each time I cancel a print because of the underextrusion, no extrusion at all is possible when I try another print later. The filament doesn't goes out. I always need to unload filament first and load it again to be able to begin a new print.

Here is the look of filament when I unload it :

Thank you for your help !

RE: Strange layer peeling : underextrusion ?

it looks like you are printing small objects with a fair amount of detail. I bet there are lots of retractions and Zlifts in the program. you may want to try reducing the retraction amount and see if that helps. lotd of retractions over a short time can pull molten plastic up above the melting zone and cause jams

RE: Strange layer peeling : underextrusion ?

I had the problem with simplier models, like the one in the first picture of this thread 🙁
Nevertheless I tried without any retractations at all but I met underextrusion and clogged nozzle all the same.
I tried to print again the base Benchy with .15 profile and it worked, but I was able to print with more details before...