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Moving from PLA to PETG - Inconsistent results  

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rwillett
(@rwillett)
Trusted Member
Moving from PLA to PETG - Inconsistent results

Hi,

I've had my MKSs+ for around 10 months and been very, very happy with it and PLA. Very few problems and a great upgrade from my Ender 3 Pro.

I've moved to PETG and am struggling with a load of issues that I get over. So moved to a Satin bed, got the temperatures higher, but I;m getting inconsistent results with Overture White PETG.

I've done the First level calibration and it looks great, I've done the large square as an additional calibration layer and that looks great. Nice squashed printing.

I'm trying to print a simple block with two holes in. I've done far, far more complex stuff than this, but for some reason I canot get this to print.

I'm getting extra PETG laid down almost immediately I start. It looks like bubble gum. See picture. I can't see how I'm getting it, I do a first layer calibaration, works fine, print this and it's a mess.

 

It looks extra filament but can't see how or why. I use prusaslicer and its simply a block with two holes in. Tried at different fill levels and just the same.

Any and all suggestions welcomed.

Thanks

Rob

Best Answer by Neophyl:

The nozzle shouldn't come loose.  In over 4 years of printing with my mk3 I have never had one do that.  It suggests a deeper issue.  If the heatbreak isn't sufficiently far down into the heatblock thread then the nozzle wont meet and seal inside the heatblock.  That in itself causes extrusion issue (inconsistencies)  but if its not against the heatbreak then the nozzle isn't locked in so I suppose it could work its way loose.

Make absolutely sure that its tight against the break and NOT the block.

If you don't then filament works its way both upward as and downwards through the threads.  There it sits and pools until it drips off.  The stuff on top of the heat block and cook and that's what the brown tint to your filament leak appears to be.  Unless of course you were printing with brown before you swapped to the white ?

 

Respondido : 13/10/2022 6:56 am
cwbullet
(@cwbullet)
Miembro
RE: Moving from PLA to PETG - Inconsistent results

It sure looks like over-extrusion or a leak in your hotend.  Where is the extra material coming from?

--------------------
Chuck H
3D Printer Review Blog

Respondido : 13/10/2022 9:12 am
rwillett
(@rwillett)
Trusted Member
Topic starter answered:
RE: Moving from PLA to PETG - Inconsistent results

Thanks for the prompt reply.

I do keep looking under the hot end to try and work out what is happending and can't see a leak. My problem is that the Prusa has been so good and pretty much faultless to now, that I haven't learnt enough about when things go wrong 🙂

I've just checked the nozzle and it was loose, so I've tightened that up and am trying again.

Appreciate the help

Rob

Respondido : 13/10/2022 9:26 am
rwillett
(@rwillett)
Trusted Member
Topic starter answered:
RE:

I've taken the nozzle out, cleaned the hotend, cleaned the nozzle, tightened it up again, I seem to recall somebody somewhere quoting a torque setting, 2NM or something, but can't find it now, so tight but not stupidly so, done a first layer calibration, done the large flat square calibration. All looks good, but what do I know 🙂

I am now printing again so lets see how this one goes.

I didn't realise a nozzle could become loose, so thats news to me.

Thanks

Rob

Respondido : 13/10/2022 12:13 pm
Neophyl
(@neophyl)
Illustrious Member
RE: Moving from PLA to PETG - Inconsistent results

The nozzle shouldn't come loose.  In over 4 years of printing with my mk3 I have never had one do that.  It suggests a deeper issue.  If the heatbreak isn't sufficiently far down into the heatblock thread then the nozzle wont meet and seal inside the heatblock.  That in itself causes extrusion issue (inconsistencies)  but if its not against the heatbreak then the nozzle isn't locked in so I suppose it could work its way loose.

Make absolutely sure that its tight against the break and NOT the block.

If you don't then filament works its way both upward as and downwards through the threads.  There it sits and pools until it drips off.  The stuff on top of the heat block and cook and that's what the brown tint to your filament leak appears to be.  Unless of course you were printing with brown before you swapped to the white ?

 

Respondido : 13/10/2022 12:35 pm
rwillett
(@rwillett)
Trusted Member
Topic starter answered:
RE: Moving from PLA to PETG - Inconsistent results

I did change the nozzle a week or so ago and I think I didn't seat the nozzle correctly. Thank your for the explanation. I haven't printed anything in brown 🙂

Just done some test prints and they are looking OK, thankfully. No leakage of filament. Simply tightened up the nozzle a little more. I will try and find out the torque settings and buy a little torque wrench to do this going forward.

Thank you for the help, I think this is now resolved.

best wishes all,

Respondido : 13/10/2022 1:26 pm
pjvenda me gusta
cwbullet
(@cwbullet)
Miembro
RE: Moving from PLA to PETG - Inconsistent results

I am glad you found the answer.  The leak makes sense based on the results.  

--------------------
Chuck H
3D Printer Review Blog

Respondido : 13/10/2022 2:26 pm
jsw
 jsw
(@jsw)
Famed Member
RE: Moving from PLA to PETG - Inconsistent results

I think a lot of folks underestimate the degree of pressure that occurs in the hot end as the molten filament is forced out a fractional-millimeter orifice in the nozzle.

If anything is loose or the heatbreak-nozzle interface is contaminated with crud, there will be some openings, although small, and the molten filament under pressure will find it.

When I change a nozzle, I've gotten into the habit of inspecting the heatblock and the lower end of the heatbreak with a dental mirror, as any debris in there, such as scorched filament residue, can prevent a good seal of the nozzle and cause a leak.

Respondido : 14/10/2022 7:45 am
rwillett
(@rwillett)
Trusted Member
Topic starter answered:
RE: Moving from PLA to PETG - Inconsistent results

@jsw

I didn't underestimate the degree of pressure as I can honestly say I never even thought about it 🙂 As the Prusa has been so reliable, I haven't learnt about these things.

Your idea of a dental mirror is an excellent idea, will pick one up now.

Thanks

Rob

Respondido : 14/10/2022 8:29 am
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