MK4 PLA Stringing  

RE: MK4 PLA Stringing

Hi, how do you manage to mesure the temp of the hotend? What kind of a thermometer are you using?

tku

RE: MK4 PLA Stringing

Having the same issue with printing with the upgrade kit PETG, hotend temp way too high with the defaults. Prusa is sending me a new thermistor. For now lowering the hotend temp by 40 degrees resolves the issue.

RE: MK4 PLA Stringing

Those cheap multimeters start to drift as they run out of battery, you might just need to put in a new battery. 

RE: MK4 PLA Stringing

I haven't binned the old one yet but I don't have a 9V battery handy to swap in. The new one I've got is more capable and came with a type K thermocouple, so I might take some temperature measurements and see if the fault actually lies with the temps independent of the thermistor.

RE: MK4 PLA Stringing

Oh guys, next time I will search first before opening a new thread (This one)

My Miniature prints looks better with 195°C. And now I will try to get even below 170°C to get evidence that my thermistor might be affected as well. I keep you informed...

RE: MK4 PLA Stringing

So I got this kit, put it together and decided to test it out by printing a figurine.  Came out looking like it got in a fight with a spider.   So I lowered the temperature and print speed, same thing.  Lowered the temperature further, still bad.   

This is the first printer I've ever had so I have no idea if it is something I'm doing wrong or if I put the thing together improperly, or if I have the 'thermistor' problem many here have noted.

Any advice would be appreciated, at this point I've got a useless tool.  Thanks!

RE: MK4 PLA Stringing

Hi, what temperature have you lowered to?

I have been as low as 170C with one bad roll of PLA

I had to reset the low temperature extrusion value, to 140C   (From 170C on a mk3) so that the extruder would actually work at such a low temperature. 

regards Joan 

RE: MK4 PLA Stringing

Mine has been nowhere near that bad - I did a temperature tower down to 170 and the extruder started skipping at the bottom end. I'm starting to think that it might just be the filament I use rather than any issue with my printer (purchased November 23).

With Overture and eSun matte PLA I get an acceptable level of stringing.

RE: MK4 PLA Stringing

Bonjour,

Moi c'est catastrophe je sais plus quoi faire.....

RE: MK4 PLA Stringing

Posted by: @grillon

Bonjour,

Moi c'est catastrophe je sais plus quoi faire.....

Nous ne le savons pas non plus...Sinon, l'anglais est parlé et écrit ici...

RE:

Posted by: @joantabb

Hi, what temperature have you lowered to?

I have been as low as 170C with one bad roll of PLA

I had to reset the low temperature extrusion value, to 140C   (From 170C on a mk3) so that the extruder would actually work at such a low temperature. 

regards Joan 

Thanks for the response, I did go all the way down to 170, and I think it may have helped a little but there is still a lot of stringing.  I also changed the Retraction length to 3.2, speed of 40, I played with layers from .05 to 1.2, nothing really makes any difference as far as I can tell.  I'm using eSun+ fyi.

I'm a noob at this, so all the changes I've listed having done above were swiped from hours of googling this issue 😀  Suffice it to say that any guidance would be appreciated!

RE:

Hey folks, I thought I'd share my before-and-after temp tower print after installing the Prusa XL thermistor. I'm using Prusament PETG and the default .4mm nozzle. The resistance I measured between both was the same at room temp (about 120kΩ). This seems to have improved things significantly for me.

RE: MK4 PLA Stringing

John, that photo was challenging to view on windows... I converted it to jpg for reference:

RE: MK4 PLA Stringing

I recently received a cheap chinese MK4 thermistor replacement, I'm going to give it a try and see if it helps.  Threw it into an aliexpress order on a whim for under $2.  I'll try to check it against the stock thermistor at a few temperatures. 

RE:

I've been researching a bit trying to figure out the exact thermistor being used for the MK4 hot end. Using the small resistance/temperature table given by Prusa support that was posted previously on here, I looked through the prusa buddy firmware source code a bit.  There are a ton of thermistors listed, but this one seemed to have a pretty closely matching calibration table to the one support listed:

ATC Semitec 104GT-2/104NT-4-R025H42G

https://www.bondtech.se/downloads/104NT-4-R025H42G_RT_table.pdf

Temperature, Prusa MK4 Resistance, ATC 104G Thermistor Resistance

• 15°C, 161.7 kOhm, 162.1 kOhm
• 20°C, 126.8 kOhm, 126.9 kOhm
• 25°C, 100 kOhm, 100 kOhm
• 30°C, 79.3 kOhm, 79.33 kOhm
• 60°C, 22.5 kOhm, 22.48 kOhm
• 100°C, 5.5 kOhm, 5.569 kOhm

I also checked the Chinese MK4 thermistor replacements from Trianglelab and BCZAMD and they list a similar model number thermistor that seems to have the same calibration I listed above:

ATC Semitec 104NT-4-R025H42G

So Prusa is pretty likely using one of these two thermistors for the MK4 hot end.  I might try to set up a high temperature calibration to compare the thermistors I have with their listed calibration curves.