Extruder completely clogges after only seconds of use

Hey there,

I use the Duet 2 Wifi on my custom made printer but I have run into a massive problem with the extruder completely clogging after only seconds of use.
The extruder that I use is an original E3D v6 all-metal hotend in a bowden configuration.
After disassembling it and removing all the plastic out of the nozzle, heatbreak and sometimes even the heat sink I then run the printer and let it print in the air to test it.
But after a few seconds of extruding PLA plastic it gets clogged again.

What I have tested:
I have tried the above at these temperatures: 180, 190, 200, 210, 220, 230.
I have tested whether the thermistor is outputting the correct temperature using an IR Thermometer and concludes that the thermistor output is correct.
My old printer (a broken down Chinese flsun cube that caught fire) had a v6 hotend clone and I have used that one but it results in the exact same problem but only messier.
I use a bmg dual drive to move the fillament and I have used it in the bowden and direct drive configuration but this did not result in any noteworthy difference.
I have both brass and hardened steel nozzles used but that made no difference.

Does anyone know what is causing the complete clogging of the hotend and possibly how to fix this?

Sounds like insufficient cooling of the heatsink. It should always have a fan on it. If you wish to be particularly fancy you can leave the fan off when its under 50c...

I'll try to do something about the cooling and come back later.

I used the normal E3D shroud with fan at first but this time I used a 40x40x10 fan and later even a second one by designing a special shroud.
Despite the heavy increase and probably overkill cooling it did not change the result.

a picture of your cooling and hotend mount would help

Using a 3mm hot end with 1.75 filament ?
No PTFE insert fitted ? but its an all metal so no PTFE required.

I have had several things cause nozzle clogs:
1) Just plain bad nozzle. E3D is NOT immune to this. I replaced a new $18 E3D .4mm 1.75mm nozzle with a Chinese knock off $1 each nozzle and fixed it.
2) Bad cooling of the heat break. Make sure your air space is not occluded and the shroud is installed so the fan sits at the very bottom of the heatsink.
3) Contaminates in my filament. Yeah, it happens. Make sure you have fully cleared the nozzle of any prior filament type, especially if it had a higher melt range.
4) Pushing the filament through too fast. Your print speed is dependent upon your nozzle orifice, filament temperature and heat block. They all have to "agree".
5) Too many retracts, too close together. This happens often with tiny parts and lots of pointy details. Set a minimum travel distance for your retracts.

They may be others, but the list above handles 99% of the frustration that I have experienced.

DLC

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Kits: Folgertech Kossel 2020 upgraded E3Dv6, Anet A8 upgraded E3Dv6, Tevo Tarantula enhanced parts and dual-head, TronXY X5SA Pro(E3DHemera).
Scratch: Large bed Cartesian, exchangeable heads, Linear slide Delta, Maker-Beam XL Micro Delta, 220x220CoreXY.

The E3D v6 doesn't like big retracts - I set mine to 2.5mm @ 40mm/sec. Any longer and you risk pulling the hot and soft filament into the cold area, where it sets.

I started having problems with my E3D and tried new thermistors, new fans, new filament, you name it I tried it. I finally made a water cooling jacket and all my problems stopped. Haven’t had a problem since then.