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MK4 PLA Stringing  

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luc.e
(@luc-e)
Eminent Member
RE: MK4 PLA Stringing

Thank you for this positive update and result. think we know what to do now.

Posted by: @jan-hruby

OK here are the photos. 

You can see two thermistors are different. Longer one from XL worked for me. 

 

On the stringing test. Right one is printed with XL thermistor.

 

Posted : 28/11/2023 6:52 pm
dzajonc liked
OB1
 OB1
(@ob1)
Trusted Member
RE: MK4 PLA Stringing

This is very interesting and great news.

I guess the batch of thermistors that there were shipping early on were not good.

I can't imagine the thermistor itself is different between MK4 and XL, unless Prusa bought cheaper ones or from different manufactures.... so if I wanted to order a new thermistor right now, how should I make sure it's not the junky version?

Posted : 28/11/2023 7:48 pm
Jan Hrubý
(@jan-hruby)
Active Member
RE: MK4 PLA Stringing

Well i would say buy thermistor for XL. Cables are little bit longer but you can tuck them in under cower nicely. But since Prusa did not publicly recognized this issue still i would say that safest way is to write to support and ask them. Nobody knows what will arrive you if you order mk4 thermistor. 

I also have second hotend assembly but i will wait some time before ordering another thermistor. Just to see how will this play out. 

Please if you decide to reach to support or buy new mk4 thermistor update us about progress. 

Posted : 28/11/2023 8:11 pm
OB1 liked
jandj
(@jandj)
Active Member
RE: MK4 PLA Stringing

Have talked with support via email, new thermistor on its way, crossyour fingers..

Posted : 29/11/2023 4:54 pm
Cannikin
(@cannikin)
Active Member
RE:

I'm talking to support right now, trying to see if I can get one of them XL thermistors. So far they've asked for photos of stringing, pictures of my hot end from all four sides, and to test the resistance of the thermistor with a multimeter! Any support I've ever talked to kind of assumes the customer is a complete idiot, so it's kind of nice they're acting like maybe people can do basic debugging tasks on their own. I'm currently printing so I'll have to do that when its down in an hour or so.

This post was modified 3 months ago by Cannikin
Posted : 29/11/2023 8:30 pm
Uranday
(@uranday)
Eminent Member
RE: MK4 PLA Stringing

After 2 not working thermistors, support agreed to send me an xl thermistor. 

I'll keep you all updated. 

Posted : 29/11/2023 9:55 pm
Cannikin
(@cannikin)
Active Member
RE: MK4 PLA Stringing

Support is sending me an XL thermistor! They said my resistance reading of 89 kOhms for mine was a little low, it should read right around 100 kOhms at room temperature.

They mentioned that they're in the process of unifying the thermistors between the XL and MK4, and they're gonna send me the XL with the longer leads.

Posted : 29/11/2023 10:58 pm
mixer3d
(@mixer3d)
Estimable Member
RE: MK4 PLA Stringing

Hi,

I found this topic recently, and while i'm waiting for my delivery, i asked in advance in the chat if the issue resolved, or the new printers are still affected by that.
So i get reply that the issue affected little number of thermistors and printers, and that dev's are already aware of it, so should be sorted out from now on... we'll see.

cheers

Posted : 30/11/2023 9:00 pm
razor10
(@razor10)
Member
RE: MK4 PLA Stringing

Guys, I'm glad I'm not alone on this issue, but then again I wish none of us were experiencing this issue.  I created my own string tower using 8mm section with varying temps in 5 degree steps starting with 230C at the bottom and working up to the top at 180C.  You can see in the photo (white tower) it was getting much better  at 190 - 200 range.  After talking with support and explain what we are all seeing and mentioning the fact that some of you were getting replacement thermistors (both MK4 and XL ones) they tried to brush off what we are seeing and hated more tests done.  So they sent me a string tower of there one but it only used the stock Prusa PLA filament profile which uses 220C, so you can see in the Blue Tower picture, the first 4cm from the bottom it was using 220C, but then I changed the temp from the LCD to 200C which the print was in progress and you can see that it gets much better at the lower temps.  I tried to mention that is the thermistor was reading it might account for it running the nozzle higher then what the profile intended.  Anyway he agreed to send me a new one, but he knew nothing about sending in one meant for the XL machine.  I guess I will wait and see what they send me.  By the way I've been using PLA+ from Micro Center which is mostly eSUN or Polymer filament.

 

Thanks

Razor

.

Posted : 01/12/2023 7:29 am
Whuazu
(@whuazu)
Active Member
RE: MK4 PLA Stringing

New thermistor. Problem solved

Posted : 01/12/2023 6:25 pm
Whuazu
(@whuazu)
Active Member
RE: MK4 PLA Stringing

Got this thermistor. I don‘t think it‘s from the XL. Neither is the one posted by jan. If you have a look at the help page on how to change the thermistor, there is also a picture of the longer version.

Posted : 01/12/2023 6:47 pm
OB1
 OB1
(@ob1)
Trusted Member
RE: MK4 PLA Stringing

Yes. I cannot find the “working” thermistor on the prusa websites, so I haven’t ordered yet. They probably want to sell what they have first

Posted by: @whuazu

Got this thermistor. I don‘t think it‘s from the XL. Neither is the one posted by jan. If you have a look at the help page on how to change the thermistor, there is also a picture of the longer version.

 

Posted : 01/12/2023 6:52 pm
Jan Hrubý
(@jan-hruby)
Active Member
RE: MK4 PLA Stringing

Well thermistor that came to me is XL thermistor based on markings from packaging. 

I can find it under XL spare parts. 

https://www.prusa3d.com/cs/produkt/termistor-ntc-100k-115-mm/

This is exactly the one that came to me

Posted : 01/12/2023 7:05 pm
Whuazu
(@whuazu)
Active Member
RE:

Are you sure? I got the same that you got (orange in the middle), which is exactly the one from prusa help article from the Mk4. The XL thermistor looks different on the pictures

This post was modified 3 months ago by Whuazu
Posted : 01/12/2023 7:19 pm
Jan Hrubý
(@jan-hruby)
Active Member
RE: MK4 PLA Stringing

Well you are right. XL on the shop doesnt have orange shielding in middle. 

But markings on package are the same. Also same lenght. 

I think we are left for guessing until Prusa release some official statement or shop is updated. Until then this looks like they have multiple version of thermistors. 

What we know now is that black wired one is not working correctly for some users. And new one from support is same lenght as XL thermistor. Maybe i will try to order XL thermistor and we will see what will arrive. 

Posted : 01/12/2023 7:28 pm
mixer3d
(@mixer3d)
Estimable Member
RE: MK4 PLA Stringing

this part extended part in the middle looks just like a heat shrinkable connector, so could be that it was the same thermistor, but for XL they just had to extend the cable, and apparently part of them was broken... both of them according to spec are 100k

Posted : 01/12/2023 8:24 pm
dzajonc
(@dzajonc)
Member
RE: MK4 PLA Stringing

Prusa support has sent me a new thermistor (delivery note from DHL came 1 day after contacting support, pretty nice).

I have not mentioned anything about the XL thermistor. So I was expecting the same black wired thermistor I already had. 

Today a thermistor with blue wires arrived. 

Tested Prusament Galaxy Black PLA with standard PrusaSlicer temperature settings. There is basically no stringing. Guess for me the problem is solved. 

Btw. I have tried to optimize the retraction settings, back then with the old thermistor:

lift height: 0.1mm

retraction length: 0.9mm

retraction speed: 45mm/s

deretraction speed: 25mm/s

wipe while retracting: on

It helped me with the old thermistor with reduced temperatures by 15 degrees. If you want try these, maybe they help. 

Posted : 01/12/2023 9:37 pm
neale
(@neale-2)
Active Member
RE:

I've pretty much solved my stringing issue with the following steps:

  • E-step calibration (it was off by almost 10%)
  • Calibrated the extrusion multiplier (article)
  • Adjust retraction in my filament to 0.8mm

I feel like I should mention this in the thread, since I was pretty sure I had a thermistor problem. Actually, I just needed to do some calibration on the extruder and filament.

Good luck, everybody.

This post was modified 3 months ago by neale
Posted : 01/12/2023 10:31 pm
JHenley01
(@jhenley01)
Active Member
RE: MK4 PLA Stringing

I can confirm that the XL thermistor that support sent has resolved the issue for me. It has longer blue wires with some orange shielding in the middle as some others have noted.

Posted : 02/12/2023 2:45 am
OB1
 OB1
(@ob1)
Trusted Member
RE: MK4 PLA Stringing

 

Posted by: @cannikin

Support is sending me an XL thermistor! They said my resistance reading of 89 kOhms for mine was a little low, it should read right around 100 kOhms at room temperature.

They mentioned that they're in the process of unifying the thermistors between the XL and MK4, and they're gonna send me the XL with the longer leads.

I checked the resistance of my current thermister and it's reading 78KOhms at room temperature. Seems like it's junk.

I'll try chatting with support tomorrow and see if they will send me a new one.

Posted : 02/12/2023 5:32 am
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