Ok, I will try to explain with my perfect english... and if you do it, so do it at your own risk.
Like most of Anycubic owners, I had problems with extrusion and print quality which has getting worst with time, ending with extruder jumps,hotend leakings, oozing etc...
Problem with hotend is there are more than one problem. It is nozzle, PTFE tube, nozzle-heatbrake-PTFE connection, heatbrake poor design, thermistor and heater poor connection with heatblock and thermistor poor quality.
Solution is very simple, you only need some skills with tools and some CPU thermal paste and time. You can use thermal glue but if you need to disassemble again in future, you will have a problem. Thermal paste is cheap, stable and easy to remove if you need it with polyalcohol and similar...
I have used Thermal Grizzly Kryonaut while it is certified to +350°C, works great.
First of all, you need new good quality PTFE tube, price is ~5e for good quality tube on Amazon in EU. Stock tube is catastrophe...
Same with nozzle, buy new ones, it is cheap, stock is very, very low quality. My nozzle was "dead" after one week.
When you get new parts, you need to completely disassemble hotend from effector, (fan's, housing, everything) take down stock PTFE tube (from hotend and extruder) and trow away (before that take lenght measure for new one) only PTFE tube, you will need coupling with new PTFE.
Prepare new PTFE, you have to almost perfectly to cut 90° on one end of PTFE (that goes in hotend-you can print PTFE cutter or so before this action, in emergency you can use coupler as cutting guide) mount it on extruder and just prepare it for hotend,leave hotend coupler aside.
You have to disassemble the hotend. Take nozzle down (pliars and wrench) and heatbrake from heatblock (heatbrake stays together with heatsink), on heatblock you will find 2 small holes where are inbus/allen screws for heater and thermistor and you have to unscrew them, take thermistor and heater out.
On heatsink you will find 2 small holes where are 2 inbus/allen screws, unscrew and heatbrake is free from heatsink, like on Pic 2.
And there you will see design problem with heatbrake. There is no threads on heatbrake on heatsink side,it is simple cylinder and tolerance is too big so heat dispersion is very poor.
Now take new nozzle and heatbrake and put it together on heatblock. I recommend to watch some yt videos how to do it, it is a very important step, i.e. https://www.youtube.com/watch?v=FNXYL-3UdOA
Put thin layer thermal paste on cylinder and inside walls on heatsink (I mean very thin layer), put it together and tighten the screws on heatsink.
At this point, half job is done.
Now take thermistor and you will see very small cylinder with wires in it at end. 99,9% cylinder is not fixed on wires and that is big problem, because you are getting wrong temperature readings because thermal "connection" is very poor, while efector is moving due printing, thermistor wires are moving inside heatblock. That is one of reasons why your hotend temperature readings are jumping 10°C up and down and you see temperature change traces on your prints.
Take small pliers and try very gently to press cylinder until it is fixed on wires.
Be aware, if you press too hard, you can permanently damage your thermistor. When it is done,put some thermal paste in thermistor hole on heatblock and thin layer on thermistor end, put it back in heatblock and tighten the screw.
Be aware, tightening screw has to press cylinder in hole (that is cylinder function). If you miss cylinder, you can permanently damage thermistror wires...again...
Now take heater, put thin thermal paste on heater and in heater walls inside heatblock,put it together and tighten it with screw.
At this point, your heatend is finished and you can assemble the hotend on effector.
When you are finished with mounting, last but not least important step is PTFE tube "housing" inside hotend.
And here is why is so important to cut the end of PTFE to 90°, because PTFE tube goes all the way down trough heatsink and heatbrake to the nozzle. If you have some bigger tolerance beetween them, you risk blob of death and similar problems.
Now comes tricky part, do it carefully, if you dont want something like on my stock PTFE, big mistake from Anycubic aka improper handling on Pic 3
Put PTFE coupler on heatsink and screw it gently till you can with your fingers, without tools,dont force to maximum tightening with fingers, you need some tolerance for later. Push PTFE tube trought coupler till end, you can use a little more force for that, just to be sure. You will notice PTFE tube goes only in one way, in nozzle direction, secure ring does not allow moving in opposite direction, it suppose to work so if everything is ok.
Now take wrench and tighten coupler with normal tightening force. Secure ring will catch PTFE tube and push it to nozzle while you tightenint the coupler with wrench.
And if everything is ok, you will get extra stable temperatures, no more oozing and realy good prints. Since I did this, I have no issues with my prints.
Pics 4,5,6,7,8 are some examples of printing, I print everything in 0,2mm.
Thats it folks :-)
Thanks for sharing this information. I have two Anycubic Kossel and one of them was experiencing wild temperature swing. We talking about 30 C-degree swings. The temperature instability is so bad that the print would be interrupted due to a thermal run-away alert. After following the steps you listed, the temperature is now rock solid!! thanks!!
Since I already have type 44 Thermal compound on hand, I used that and it works great. I was able to remove both heating element and the thermistor without removing the entire hot-end from the printer. I smother both the heating element and the thermistor in the thermal compound and stick them back into the hole. Wipe off the excess and all is well.
Thanks for taking the time to share the information.
Very interesting tutorial :-) Thanks man !
Wow, that is a detailed How To. Beautiful printquality too.! Thanks.