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. 

RISPONDI: MK4 PLA Stringing

I resume this post to confirm the issue with the hotend thermistor with black wires: my MK4 (now upgraded to MK4S) had very bad stringing; after various tests I found that lowering temperature by 20° on the default profiles fixed the problem. Then found this topic. I've bought a hotend thermistor replacement having contact with Prusa live chat to assure they send me the blue wired thermistor. They say all thermistors are equivalent so they cannot sell a thermistor by color, but when my shipmet arrived the new thermistor had blue wires. I've changed my black wired thermistor with the new blue wired one and now my printer prints perfectly with standard profile temperatures. I suppose Prusa had a stock of faulty hotend thermistors; since a new thermistor is only 12 € and is very easy and quick to change, I suggest everyone with bad stringing to buy a new one. At the end problem solved, now my printer is perfect.