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Steam Labs
(@steam-labs)
Active Member
Topic starter answered:
RE: Underextrusion

@pjr

This is the same copy and paste from chat support. I tried this twice and it didn't work for me. It's too awkward to push the heater block up, keep it in position, and tighten 3 screws. 

It works easier to take everything out of the heat sink, then push the hot end up as far as possible and tighten the screws. Then you can put the ptfe tube back in and tighten the bowden until you feel resistance. 

It makes sense to me that you want pla to stiff while in the heat break. If the heat break is hanging out of the heat sink by 10 mm the melt zone length would be longer. This is causing issues. 

If we assemble your way the heat break 'stick out' is determined by the length of the ptfe tube. My spare tube was at least 1mm longer than my installed one.

Are you saying that the stick out isn't a critical measurement and can be any random value and still work?

I hope the factory is getting this feedback and they adopt a torque spec on the grub screws. Chat support was defensive and wanted to argue about theoretical temperature values. 

...
Posted : 28/12/2019 2:09 pm
towlerg
(@towlerg)
Noble Member
RE: Underextrusion

@chris-b2

"I'm still getting a crackling sound" I read somewhere that the sound is caused by moisture in the filament.

Posted : 28/12/2019 2:16 pm
NVGG Creations
(@nvgg-creations)
Eminent Member
RE: Underextrusion

@towlerg

Remember that that the idler tension is quite often set to tight.  Try backing it off so that the head is approximately in line with its casing.

Posted : 28/12/2019 3:51 pm
NVGG Creations
(@nvgg-creations)
Eminent Member
RE: Underextrusion

@olef

Thank you for your work here.  My mini just completed its first print after days sitting doing nothing.  Although Prusa support felt the issue was somewhere in the hot end, they did not get that it was something as simple as a bad installation.  This fix and the idler tension has got my mini up and running.

Thanks again

Posted : 28/12/2019 3:54 pm
Olef
 Olef
(@olef)
Honorable Member
RE: Underextrusion
Posted by: @mark-g33

@olef

Thank you for your work here.  My mini just completed its first print after days sitting doing nothing.  Although Prusa support felt the issue was somewhere in the hot end, they did not get that it was something as simple as a bad installation.  This fix and the idler tension has got my mini up and running.

Thanks again

I'm very pleased my post helped. I was in exactly the same position and it was frustrating to say the least. I've just managed to print an almost perfect Benchy!

Posted : 28/12/2019 4:00 pm
jockspice
(@jockspice)
New Member
RE: Underextrusion

While troubleshooting, I have found that the filament will stop in the heatbreak before the hot zone; the hole is too small for 1.75mm filament. I know on the standard E3D you can get the filament all the way through and out with the nozzle off, (heatbreak diameter is 2mm at thinnest) so this may be the reason I'm not extruding and it may be the cause of the springback of filament. Can anyone else get filament through with the nozzle off? Are the tech specs for parts available?

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Posted : 28/12/2019 4:36 pm
Clive
(@clive)
Trusted Member
RE: Underextrusion
Posted by: @brad-w2

@pjr

This is the same copy and paste from chat support. I tried this twice and it didn't work for me. It's too awkward to push the heater block up, keep it in position, and tighten 3 screws. 

It works easier to take everything out of the heat sink, then push the hot end up as far as possible and tighten the screws. Then you can put the ptfe tube back in and tighten the bowden until you feel resistance. 

It makes sense to me that you want pla to stiff while in the heat break. If the heat break is hanging out of the heat sink by 10 mm the melt zone length would be longer. This is causing issues. 

If we assemble your way the heat break 'stick out' is determined by the length of the ptfe tube. My spare tube was at least 1mm longer than my installed one.

Are you saying that the stick out isn't a critical measurement and can be any random value and still work?

I hope the factory is getting this feedback and they adopt a torque spec on the grub screws. Chat support was defensive and wanted to argue about theoretical temperature values. 

I've had the same experience, if you tighten the bowden coupler with the grub screws loose you end up with the heatbreak sticking out the bottom as it gets pushed down by the ptfe tube.

My spare ptfe tube was 2mm longer than the pre installed one also. If I didn't cut it back the bowden coupler couldn't be tighten all the way.

I'm starting to think Prusa's internal assembly instructions are wrong and they haven't noticed because initial tests pass. It makes no sense to have the heatbreak sticking out of the bottom like it is when you follow the instructions pasted from chat.

...
Posted : 28/12/2019 10:35 pm
Akshay
(@akshay)
New Member
RE: Underextrusion

Surprising! Mine looks like yours but is still printing fine. 

Posted : 29/12/2019 1:09 am
M8Harry
(@m8harry)
Trusted Member
RE: Underextrusion

I FINALLY got my mini printing with 3d fillies PLA+

So after adjusting the hot end  as per the instruction on page 3 or 4, tweaking the minda and changing the ptfe tube to the 2nd bit supplied, its printing with no jams and reasonable quality off the bat.

Thanks to all for posting up what ya did.

My only issue was one of the 3 grub screws stripped when doing it up, hoepfully i can get a 1/8th allen key in there to get it out at a later date and replace it.

Otherwise all is well so far so good.

Respect the fact everyone is entitled to have an opinion, you dont have to like it or hate it, just accept its theirs and not yours and you will be ok!...
Posted : 29/12/2019 10:13 am
Steam Labs
(@steam-labs)
Active Member
Topic starter answered:
RE: Underextrusion

I made a video describing how to fix your hotend if your are having underextrusion and jamming issues.

 

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Posted : 30/12/2019 4:07 am
MikaM, Jakub K., Gabriel S and 1 people liked
Gabriel S
(@gabriel-s)
Trusted Member
RE: Underextrusion

@brad-w2

Great video! I did everything in it before you posted it, but it will be very helpful for those affected. The only thing I'd add to it is that you should not put the PINDA probe too high (or even that high at all). I made the mistake of putting it about 1 1/2 cm above the extruder nozzle or so, ran calibrate, and quickly made a good circular dent in my steel sheet. 

Posted : 30/12/2019 5:14 am
NVGG Creations
(@nvgg-creations)
Eminent Member
RE: Underextrusion

@g-j-sieben

I think the way to set the PINDA probe is to power off the printer, raise the PINDA probe and then manually lower the hot end until the nozzle just touches the bed.  Then re-set your probe height using credit card/cable tie

Posted : 30/12/2019 8:33 am
prusa3-10
(@prusa3-10)
New Member
RE: Underextrusion

My hot end looks to be a bit low.  Is this necessarily a problem?  I am seeing a little bit of an under extrusion problem, but nothing like what people are discussing on this thread.

Should the underside of a print be smooth?  I printed the sample Prusa logo file and it makes a good bit of noise when I run my fingernail over the bottom perpendicular to the layer lines.

Posted : 01/01/2020 5:03 am
NVGG Creations
(@nvgg-creations)
Eminent Member
RE: Underextrusion

@prusa3-10

I'll answer your second question first.  Yes it should be smooth underneath your print.  Incredibly smooth actually if you are using the flat PEI sheet or smooth with a pleasing texture if using the textured sheet.  Sounds like you need to do your live z adjust again.

With regard to your hot end. That does look low and I am willing to bet that if you don't have much of a problem now, you will have soon, especially with some of the more interesting filaments.  I would recommend raising your hotend.  Just for the record, I didn't actually remove the PTFE tube as recommended in this thread, I just removed the grub screws and pushed the hotend firmly up while holding the heat sink firmly.  Cured all my problems.  If you do do this, you MUST re-set your PINDA probe.  With the printer off, raise the probe so that it higher than the nozzle and then manually lower the nozzle by turning the Z axis screw until the nozzle just touches the bed.  Then adjust the probe to be about a credit card width above the bed.  Then run your calibration wizard again.

Posted : 01/01/2020 9:27 am
Lichtjaeger
(@lichtjaeger)
Noble Member
RE: Underextrusion
Posted by: @jameswilddev

Mine has now very suddenly started doing this with all filaments I have after tens of hours of flawless prints. 

That's a first layer issue. Your Nozzle is way too deep. Add distance in your first layer calibration (turn the wheel in plus direction).

Posted : 01/01/2020 4:45 pm
Lichtjaeger
(@lichtjaeger)
Noble Member
RE: Underextrusion
Posted by: @prusa3-10

My hot end looks to be a bit low.  Is this necessarily a problem?  I am seeing a little bit of an under extrusion problem, but nothing like what people are discussing on this thread.

My heat break looked exactly like yours. Because of all these posts and that video I tried to raise it, even I had no problems and a beautiful print quality. Now I have all those blocking issues and hope to get it back to where it was. Do not mess with the grub screws or the heat break. It is good as it is.

If you see a little gap between the heat block and the hex part of the nozzle, then the position of the heat block on the heat break is also right.

Your hot end looks all right to me.

Posted : 01/01/2020 4:59 pm
shinwachi
(@shinwachi)
Active Member
RE: Underextrusion

@lichtjaeger

I'm having issue post heat break modification now ( https://forum.prusaprinters.org/forum/hardware-firmware-and-software-help/jams-in-heatbreak-any-way-to-boost-voltage-to-fans/#post-182693 ), with filament melting at top of heat sink.  I'm pretty sure the previous issue *was* melted PLA in the pfte tube gap near the throat (I saw a ring of PLA in the gap), but now the problem has crawled up.

As cool as it looks (pun intended), I think there is an issue with the new heat sink design. I'm going to look for ways to boost fan speed to compensate.

Posted : 02/01/2020 10:08 pm
bennydesign
(@bennydesign)
New Member
RE: Underextrusion

I just wanted to say THANK YOU SO MUCH!!! My printer started to mess up prints after about 6 hours of use.  After going thru all the steps you mentioned I had adjusted the nozzle by about .6 mm.  That fixed it - hopefully forever. 

You guys just made my 2020!

Regards

Benjamin

Posted : 03/01/2020 8:36 am
jockspice liked
MikaM
(@mikam)
Active Member
RE: Underextrusion

My Mini printed 1 print perfectly.. second mediocore and the third is very badly underextruded.. nothing that I do helps. Also there seems to be odd noises from the extruder motor or somewhere... Is this printer really this messed up compared to MK3..

Posted : 03/01/2020 4:11 pm
NVGG Creations
(@nvgg-creations)
Eminent Member
RE: Underextrusion

@mika-m

These are exactly the symptoms I had until I raised the hot end and loosened the idler as this thread describes.  Have you tried these?

Posted : 03/01/2020 9:02 pm
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