0.4 Nozzle changed has made my printer poor...  

RE: 0.4 Nozzle changed has made my printer poor...

Just something from my experience. I bought an old MK2.5S. 
Had to do some adjustments, and then it printed rather well. 
So I keep going for bigger objects. 
And then simular happened, After 1-2 hours (maybe 50, maybe 100, etc layers (so not always at same height or time). It stopped printing. 
I don't know what you mean by "crashed"? Mine did just stopped printing and sometimes started short time later in air creating a log spaghetti 🙂 

It was a long search, then I found out that there was problems with the PTFE-tube.  When I completely disambled the extruder I saw two abnormal things: 
- the downside (near the nozzle) was not cut nicely, but rough. Maybe not wel done, by first owner, or maybe damaged by cold-pulls. 
- The collet what held the PFTE-tube was loose and there was no clip on the collet, so the lightest touch could push the collet down again. 
As I understand the effect of these things were that: 
- After longer time the hot filament came into the cool part of the extruder. This caused clots, pushing the PFTE-further up (remeber there is a lot of movement, because the filament is retracted and pushed back in x times per minute). And beng complete clot. No filament anymore. 

Eef

RE: 0.4 Nozzle changed has made my printer poor...

Thanks Eef.  As it happens after a number of failed prints I did strip down the hot end.  The PTFE was good and I made sure to push the collet down.  Sadly none of that strip down has appeared to help as yet.  I did manage to get a complete print out of it yesterday, but the quality was not super so I am making progress.

RE: 0.4 Nozzle changed has made my printer poor...

Posted by: @tre4b

push the collet down.   

I hope you mean up cq outwards 🙂 
Curious what you will find as root cause of the failed prints. 

Regards. Eef 

RE: 0.4 Nozzle changed has made my printer poor...

Well I took it apart again at the weekend.  I remembered when I put it together not being quite sure whether the heatbreak was bent or not, so I decided to replace that (real bastard to undo somehow had got really wedged in!).  Managed to maul the ptfe while doing that though so had to replace it.   Double checked that the lock ring was out and the ptfe could not move.  Put it all back together and did a print which seemed to go fine so I left it to finish.  Unfortunately there was a huge layer shift during the last 10mm, plus the quality lower down was not good at all.

Not sure if this was another crash though as I was not present when it happened so it was probably a crash and resume, but am now running it again while I am working so hopefully if it crashes I will hear it and can check.

RE: 0.4 Nozzle changed has made my printer poor...

Pretty sure the extrusion is the problem here.  Will check it out again tonight after work make sure it is not leaking at the top and do a cold pull.

RE: 0.4 Nozzle changed has made my printer poor...

And now I know why the extrusion was bad, sometime when I put the 0.4 nozzle in, I actually picked up the 0.6.  So I was trying to extrude for a 0.4 nozzle through a 0.6 one!   Hopefully this will be the solution to the whole problem and once back together it will be back to its normal reliable self.

RE: 0.4 Nozzle changed has made my printer poor...

I had layer shifting and blob problems after replacing a nozzle which caused crashes after printing for a while due to oozing filament.  The fix was found by accident on a youtube video and does not match the Prusa instructions, but worked great.   Here is what i did (start from all the parts cleaned and disassemble):

1. Disassemble the print head and remove the full hotend from the plastic printed parts.  Remove the PEI tubing and set aside.
2. Heat the hotend to 250 deg and carefully clean any filament from the hot end.
   1. While heated, carefully disassemble the nozzle, heater block, heatbreak and heatsink, and place them on a heat safe surface and allow it all to cool.  If parts appear to be damaged or too old to reuse, replacing them now is a good idea.
3. Now to reassemble.
   1. Apply thermal paste to the heat break (long thread is the only place the thermal paste is used) and screw it into the heatsink finger tight until it stops.  No paste should be applied to the end that screws into the heater block.
   2. Screw the nozzle into the heat block until it stops, then back it out 1/2 turn (allowing a small gap between nozzle base and heater block
   3. Screw together both heater block and heatsink part, hand tighten until it won't move, but not so tight as to break the heat break (thin metal so can bend or break of over-torqued)
   4. Install the thermistor and heater cartridge (if you removed them) and tighten screws to hold them in place (some people add thermal paste to both of these, but seems like a waste)
   5. Plug the thermistor and heater cartridge into your printer and power it up.
   6. Grab a good wrench or pair of locking pliers, a nozzle wrench and heat proof rag for the next steps
      1. Set hotend/nozzle temp to 250 degrees and wait 60 seconds after the temperature is reached for the temp to stabilize.
         1. Now you will remove the gap between the heatsink assembly and the nozzle assembly. Using the pliers;
            1. Tighten the heatsink - hold the heater block firmly (being careful not to crush the thermistor or heater cartridge wires) and using a rag around the heatsink, tighten the heatsink assembly by hand until it won't move.  Be careful not to overtighten or break the heat break
            2. Now move to the nozzle end - again, hold the heater block and using a nozzle wrench, tighten the nozzle until it won't move.  Again, be careful not to over-tighten or strip the brass nozzle
            3. The gap is no longer there which is what you want; this prevents the possibility of oozing between the two metal parts.  And the thermal paste will prevent temperature loss theoretically which provides more even heating of the filament as it passes through the heat zone
            4. Some people allow the hot end to cool, then heat to 250 deg and repeat the tightening process again; haven't needed it yet but something to keep in your pocket if needed in the future.
   7. Turn off the printer and allow the hot end to cool completely before reassembling the extruder assembly
      1. If your hotend uses the PEI tubing, insert the tube into the top of the heatsink until it stops, pull up on the collet and press the PEI tube down again, then insert the retainer clip to lock it in place
4. Now reassemble the printer and do a first layer calibration again to make sure your first layer is perfect.

Enjoy printing blob and crash free.  Worked perfectly for me, hopefully it does for you too.