Problems after nozzle change  

  RSS
samuel.zetterlund
(@samuel-zetterlund)
Active Member

Hi everyone,

I assembled my MK3S printer a couple of weeks ago and it has truly worked like a charm. All problems I've encountered have been caused by other things than the actual printer. I've printed PLA from a few different vendors and while I was waiting for a hardened nozzle I did small glow in the dark prints as well. 

 

I then ordered a nozzle x from e3d, https://e3d-online.com/nozzles-for-3d-printer/nozzlex and since then I've had issues. When I removed the prusa nozzle, there was a light cracking sound but I'm quite sure that it was not a bad sound. I then switched to the hardened nozzle and tried to print some of the models I previously printed but with glow in the dark filament instead of regular PLA. At first, the filament wouldn't stick to the PEI sheet. I then added a brim to the model and it would somehow improve it a bit. I increased the nozzle temperature from 210 degrees to 220 because I heard that the hardened nozzle might need a higher temperature due to worse thermal conductivity. Sometimes a few layers were ok but then the layers would start to warp. I tried to shut down the fan but that only resulted in a big blob. 

Since the only change I did was changing the nozzle I checked it again and it felt a bit loose so I retightened it a bit. I managed to do one small  Ninjaflex print ok and one glow in the dark PLA print ok with very low print speed.

Anyhow, this was unacceptable so I switched back to the brass nozzle thinking that I'm better off with a printer I can rely on even if it would mean that the brass nozzle would wear down eventually but now I can't seem to make good prints. This night I made one successful print but after that I can't even get the first layer right. I've cleaned the PEI sheet but that didn't help.

This is what the first layer calibration looks like. I've tried very different z heights but they all have the same characteristics. The nozzle itself looks clean enough. What has happened and why can't I get it right?

 

(The lower part of the PEI sheet is still covered with bits of tape. I came across a tip adding tape for flexible prints but now I have a hard time removing all of it...)

Posted : 13/11/2019 8:17 am
samuel.zetterlund
(@samuel-zetterlund)
Active Member

Update:

I redid all calibration steps using the wizard and after many first layer calibrations I got that one right. I also flipped the PEI sheet and cleaned that side so the sheet should be fine. But all prints fail like this...

 

Please help.

Posted : 13/11/2019 10:05 am
bobstro
(@bobstro)
Illustrious Member

Inspect the hotend above the nozzle to make sure you don't have any leakage around the top of the nozzle, or at the top of the heatbreak. Did you have everything heated up before removing the original nozzle? Did you follow the Prusa procedure for swapping nozzles?

It's possible the cracking noise was just some old filament breaking away, but I've done dozens of nozzle swaps and never hear what I'd describe as a cracking sound. It is possible to break the heatbreak if it gets twisted in this process.

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 13/11/2019 12:33 pm
samuel.zetterlund
(@samuel-zetterlund)
Active Member

Thanks for your reply @bobstro. Yeah, I heated it up to 285 degrees. I followed the procedure in this video:

I can't be completely sure but I really think the cracking sound was old filament. I'd rather try other things first before disassembling the extruder... 🙁

Difficult to answer but how hard do you tighten your nozzles? If the nozzle isn't super tight, could you get this problem? When I first swapped to the hardened nozzle and checked it after a while, it was quite loose but now it's tight but I didn't tighten it with too much force I think...

Posted : 13/11/2019 1:43 pm
bobstro
(@bobstro)
Illustrious Member
Posted by: @samuel-zetterlund

[...] Difficult to answer but how hard do you tighten your nozzles? If the nozzle isn't super tight, could you get this problem? When I first swapped to the hardened nozzle and checked it after a while, it was quite loose but now it's tight but I didn't tighten it with too much force I think...

I get good results using the "two finger" (well, thumb and index finger) final tightening at 285C. The key is the fit of the nozzle against the heatbreak. A lot of the guides make a big deal about the need for a small (<1mm) gap between the nozzle hex and heater block, but don't (IMO) stress enough that this should be the result after fully tightened against the heatbreak inside the heater block. I think more emphasis should be placed on ensuring the heatbreak extends far enough down into the heater block that it is impossible to tighten the nozzle completely against the heater block. The block is essentially just a nut holding the nozzle and heatbreak together.

By taking the time to understand what's the desired result is, I've made easily dozens of nozzle swaps over the last 18 months with only one leakage. (I did strip out a heater block, probably due to early efforts.) If you end up disassembling your hotend, be sure to get the heatbreak installed properly!

Tip: If you do end up with filament leaking due to poor fit, you can clean out the heater block threads by heating it up to temp and running the heatbreak all the way through a few times. Screw the heatbreak into the heatsink to keep your hand cool, and use pliers in the other hand to hold the hot block.

 

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 13/11/2019 2:57 pm
samuel.zetterlund
(@samuel-zetterlund)
Active Member

Thanks again @bobstro. I need to digest that information a few times... 🙂

I did however swap back to the hardened nozzle, just trying to get it correctly tightened and first of all the brass nozzle looked like this:

It seems like there has been a leakage right?

Then I swapped back to the hardned nozzle and also switched to a different filament. I directly printed this calibration cube successfully.

 

Right after that, I tried the model that had been failing many times before (the robot from le fabshop) and it failed again.

 

After this print, I lowered the z height and managed to print this batman cookie cutter with no issues.

 

Question: if I really did break the heatbreak, would it still be possible to do these successful prints? It seems like my printer has an especially hard time printing the robot. Maybe I have tightened the nozzle better this time?

Posted : 13/11/2019 6:24 pm
bobstro
(@bobstro)
Illustrious Member

Your heatbreak is probably fine. It does look like you had a small gap initially that caused the filament build-up below the nozzle threads. Your subsequent print looks good. The problem with the robot is most likely poor bed adhesion (the lifting at left) caused by getting your mitts on the PEI during all this. Give it a dunk under the kitchen sink and a scrub with Dawn dish soap (or local equivalent) and a clean plain paper towel. Dry it with another paper towel and try again. You're close! 

Those odd blueish blobs may be old filament dropping off the nozzle and/or heater block. Clean them off with a soft brass wire brush, being careful around the wires. Monitor for leaks. 

This post was modified 9 months ago by bobstro
My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 13/11/2019 6:56 pm
anricco
(@anricco)
New Member

Hello,

Thank you. Apparently here there is exactly the same problem, because after changing the brass nozzle to the hardened steel nozzle E3D V6, there seem to be adhesion problems. Their cause should be different from the nature of the materials and the print bed because before everything was working without problems and the problems remain with all materials and all conditions. In fact it probably originated in following the procedure of the same video "How to replace the extruder nozzle", that suggests to unscrew or loosen the heater block, instead of the written guide "Changing or replacing the nozzle". Unfortunately from the previous messages it is difficult to find what was the solution. After some small tinkering it seems that there is very little space if any between the nozzle and the heater block. By the way, having bought the fully assembled i3 MK3S printer and having little knowledge of how to mount the printing head if possible it would be preferable to find a minimal solution eventually avoiding disassembling the printing head, because also changing the nozzle was presented as similar to a change in the camera lens and in fact it had some difficulty. Wish you a nice continuation.

Looking forward to hearing from you, thank you and best regards.

A.R.

https://www.help.prusa3d.com/en/article/changing-or-replacing-the-nozzle_2069

Posted : 14/07/2020 11:47 am
Share:

Please Login or Register