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Currently, I'm using a Creality printer to print PLA (that's what I have on hand) but I'm definitely interested in working with other materials that require higher temperatures (both much higher, and just enough higher that the stock hotend is very marginal) in the future.

I understand that all-metal hotends are less forgiving and that they particularly are not the best for printing PLA, and shouldn't be assumed to be an upgrade when only printing PLA.

What I don't understand is, how bad are they? Are they so bad that I should plan on changing back to a PTFE hotend whenever I print PLA or ABS? Or are they suitable for use on a printer that is sometimes used for printing PLA and ABS and sometimes printing high-temp filaments?

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    $\begingroup$ Simplified version (needs expansion to be an answer): due to heat creep & lacking non-stick property of PTFE for the entire path to nozzle, retracted filament can finish solidifying and jam in heatbreak/coldend. $\endgroup$ – R.. GitHub STOP HELPING ICE May 19 at 13:25
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    $\begingroup$ ABS does not suffer from heatcreep to a degree that you need to concern about it like for PLA. $\endgroup$ – Trish May 19 at 15:04
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    $\begingroup$ From close experience, I know of printer types (commercial available, I will not release the brand) that are excellent in printing ABS, but cannot produce a single print in PLA no matter the settings! Answering how bad is subjective, I'm running an Ultimaker 3 (no PTFE lining) a large CoreXY (no PTFE lining) and my own Prusa i3 design (with lining), either genuine E3D and clones, and can print PLA without a problem. So it ranges from total success to total failure. IMHO, your question cannot be answered. Cooling of cold end and tuning retraction settings is key. $\endgroup$ – 0scar May 19 at 17:51
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All-metal hotends are less forgiving

Yes

not as good for PLA

No

but how bad?

That is very subjective and totally depending on the skill of the 3D printer operator! So, that part of the question cannot be answered.

Fact is that all-metal hotends are sold as being upgrades to lined versions, this is simply not true. It is a different design that can handle higher temperatures. To operate such hotends you require a little more experience as these hotends are a little less forgiving if you do not have the right slicer settings. Key parameters are hotend temperature, cold end cooling and retraction speed and length and amount of retractions in the model.

Another fact is that e.g. the Ultimaker cores concept (we opened a 0.4 mm core to see that for ourselves) doesn't use a PTFE lining, nor do other brands. They can perfectly print PLA (even with a high retraction length). The only time if failed printing PETG (higher temp than PLA) was the result of a heat creep induced clog which was caused by a cooling fan failure (the cooling fan ingested something and seized up), so just one print of a few meters of the several kilometers 2.85 mm that got printed.

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Are they so bad I should plan on changing back to a PTFE hot end?

No, all metal hot end are not that bad, and may even be beneficial when printing at higher temperatures. You mentioned that you want to print ABS and other such materials. At temperatures this high, my understanding is that the PTFE tube in the hot end may melt, or at least become so damaged that the hot end is blocked, leading to needing to replace the tube. My first 3D printer used a PTFE ho tend, which due to the printing temperatures I was using, and lack of knowledge of the many types of hot end, the tube got damaged after about 2/5 hours, leading to me needing to replace the tube. I eventually sent the printer back, got my money back and got a printer with an all metal hot end. That has never failed me in hundreds of hours of printing.

Are not the best for printing PLA

I have never had a problem printing PLA with an all metal hot end, however if you are printing just PLA, a PTFE hot end would be just fine, although not as versatile if you wanted to try different materials in the future.

In Summary:

Provided you print fast enough (I regularly print at 60 mm/s) to ensure that no filament cools down in the hot end you should be fine.

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    $\begingroup$ Could you expand on whether this includes printing of models with lots of travel moves where you need frequent retraction to print accurately (without oozing loads of material all over the place in the wrong places), with a working amount of retraction? It's very plausible for an all-metal hotend to work fine printing vases or anything with simply-connected cross-sections, but jam badly due to heat creep under repeated retraction. And as I understand it the particular hotend and how it's installed make a lot of difference to whether that happens. $\endgroup$ – R.. GitHub STOP HELPING ICE May 20 at 0:15
  • $\begingroup$ @R..GitHubSTOPHELPINGICE Retraction typically doesn't cause me any issues. Provided you aren't retracting for hours (unsure how that is even possible), you should be fine. The hot end is still warm enough to re-melt the filament. I always just push a bit of filament through before I start my first print, just to ensure that it is all melted. also, I print 5 - 10 degrees warmer with an all metal hot end just to make sure. $\endgroup$ – LukeDunkley May 20 at 15:39
  • $\begingroup$ Concern is not duration of a single retraction but retracting roughly the same segment of filament many times, and having it get stuck because of how/where it melts/solidifies or because of non-smooth (compared to PTFE) metal surface or actual ridges. $\endgroup$ – R.. GitHub STOP HELPING ICE May 20 at 17:18
  • $\begingroup$ @R..GitHubSTOPHELPINGICE Sorry, I misunderstood. Surely if the hot-end wasn't smooth, or was so rough it was causing major issues, it would be time to get a new one? $\endgroup$ – LukeDunkley May 20 at 17:26

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