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I was having heat creep related hot end clogs leading to skipped layers or plain old air printing (with extruder stepper skipping). Since I'd just received the all metal hot end I ordered a while back (Chinese knock-off, verified 2 mm heat break bore), I installed that and tried a print without changing settings.

Amazon Basics PLA, 200 °C at 0.4 mm nozzle, 50 mm/s (which gives walls and first layer at 25 mm/s), and 30% tri-hex infill -- and instead of clogging an hour an a half into the print, the new setup clogged after only about half an hour.

There is little retraction in this part -- every layer is continuous (that is, there are no travels between sections, only between infill lines and after layer end, it's a simple extruded shape from the first layer to the last), so I wouldn't expect excessive retraction to be a major issue.

Is this likely to be due to printing with the same settings I had for the original hot end? If so, what should I change (retraction, obviously, but temperature, print speed, etc.?).

EDIT: Reinstalling the previous (stock type) hot end after clearing filament material from the heat break has restored normal-seeming operation, at least when starting a print from cold. Parts are on the way to apply the PTFE fix.

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  • $\begingroup$ Extruder cooling fan isn't powerful enough? Have you changed your hotend fan? $\endgroup$
    – FrontENG
    Jul 19 at 13:45
  • $\begingroup$ @FrontENG Still running the stock fan for both heat sink and part cooling. $\endgroup$
    – Zeiss Ikon
    Jul 19 at 13:46
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    $\begingroup$ This kind of all metal hotend is not recommended for just PLA.It's not an "upgrade".The metal throat tube actually make it easier for heat to creep up unless you install a more powerful fan. 0scar explains this in his answer 3dprinting.stackexchange.com/a/11979/19888 $\endgroup$
    – FrontENG
    Jul 19 at 14:02
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    $\begingroup$ Maybe a Pyrex or quartz tube would work and be less expensive. $\endgroup$
    – Perry Webb
    Jul 19 at 18:56
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    $\begingroup$ @FarO As others have suggested, this might be due to the Bowden tube backing up under pressure. I haven't had a clog since reinstalling the stock type hot end, and I'll be installing the "PTFE fix" (captive high temp PTFE inside the heat break) this weekend. $\endgroup$
    – Zeiss Ikon
    Jul 22 at 15:46
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As suggested in comments, I've installed Luke Hatfield's captive PTFE tube fix using high temperature Capricorn PTFE tube inside the heat break, and this seems to have solved the problem, while accomplishing the main thing I wanted an all metal hot end for: allowing higher print temperatures for filaments that require it.

In my case, I had to modify the classic procedure a bit; careful measurement of my heat sink required printing a custom "washer" with top end diameter of 8 mm, bottom (against the heat break) diameter of 5 mm, 4 mm taper length, 1 mm thick non-tapered top extension (so the coupler could compress the washer into place); I drafted a 2.25 mm bore (after an initial prototype at 2.1 mm wouldn't pass filament with marks from the extruder teeth; there's probably some shrinkage in the printing process) and an entry cone of 3.125 mm diameter, tapering to bore diameter after the first 3 mm.

I cut a piece of Capricorn PTFE tube 1 mm longer than the heat break; assembled heat break to heat sink (to ensure it was bottomed against the shoulder in the bore), then screwed heat break into the heat block to set depth, ensuring that the nozzle would tighten against the heat break before bottoming the hex against the heat block. Hot tightening the nozzle, followed by tightening the coupler, gave about 3% compression of the captive Capricorn tube, ensuring a good seal against the nozzle.

I kept the stock, translucent PTFE for the Bowden tube, so I can see the filament (at least as a shadow) when I load it, but where it matters, I now have captive, compression sealed PTFE that's rated up to 300 °C -- and this has so far worked perfectly for a number of prints.

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