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Stringing after partial hot end replacement  

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tom.otvos
(@tom-otvos)
New Member
Stringing after partial hot end replacement

My MK3S has been a real workhorse since I assembled it last year. I had it working very smoothly. Twice now my print has lifted from the heat bed and made a bit of a mess. The first time, I was able to remove the filament blob with only damage to the fan shroud, which I could reprint. This last time, however, the blob was all over the hot end and wires and I could not remove it without eventually damaging the thermistor wires.

So I ordered a new thermistor and, while at it, a new heater block because the grub screw was hopelessly gummed up. Since my nozzle was also pretty messy, I decided to get a shiny new one.

As I was assembling things, I over-torqued the nozzle because I did not have a torque wrench and it sheared in the block. Additionally, the heat break was now really in there and I could not get it out and it, too, eventually sheared. So with new respect to torquing, I got another heater block, nozzle and, now heat break. The heat sink and PTFE tube were perfectly unscathed. I managed to get everything together and I was back in business.

Except that now, all my prints are stringing. I am using Prusament PLA and PETG, and both string a lot. Attached is a photo of the PLA Temp Tower. Both PLA and PETG were printing fine a week ago, so it is not the filament. So I am looking for suggestions on how to debug this further. There is no filament leaking anywhere, it just seems to be running "hot". So is there some kind of thermistor calibration I needed to do? Or redo something with the PINDA since it would be miraculous if the relative offset between it and the nozzle was the same?

Any advice on how to proceed would be welcome.

This topic was modified 5 months ago by tom.otvos
Posted : 28/06/2021 11:49 pm
cwbullet
(@cwbullet)
Illustrious Member
RE: Stringing after partial hot end replacement

Did you recalibrate your PID?  If you changed parts to an off-brand, they might be an issue.  

--------------------
Chuck H
3D Printer Review Blog...
Posted : 29/06/2021 12:57 am
tom.otvos
(@tom-otvos)
New Member
Topic starter answered:
RE: Stringing after partial hot end replacement

@cwbullet

That is the kind of think I am looking for! No, I have not done that. I did not buy my parts from Prusa but the thermistor (which I would suspect if the machine behaves like it is running "hot") is an "Official E3D Prusa Specific Thermistor PT100". 

Although if I am recalibrating the PINDA then is the issue more that the PINDA distance is now slightly different and therefore it needs to recalibrate so that it knows the distance from the heat bed? Honestly it was so long ago...is this calibration done when the printer is first set up?

Posted : 29/06/2021 1:45 am
tom.otvos
(@tom-otvos)
New Member
Topic starter answered:
RE: Stringing after partial hot end replacement

@cwbullet

Unfortunately, neither the Temp or PID calibrations had any effect. I am going to take apart the extruder and ensure the filament feed is properly lined up. Maybe there is something going on with retraction?

Posted : 29/06/2021 12:55 pm
Diem
 Diem
(@diem)
Noble Member
RE: Stringing after partial hot end replacement

Both PLA and PETG were printing fine a week ago, so it is not the filament.

A week is enough in humid weather.  Stringing is one of the early symptoms of damp filament - are there any popping and creaking sounds from the extruder..?

Try drying the filament before anything else - it's the cheaest and one of the easiest fixes if it works...

Cheerio,

Posted : 29/06/2021 2:33 pm
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