<p>While heat creep as you describe it <em>is</em> a concern, The more pressing reason to let a hotend cool off first is <strong>safety</strong>.</p>
<p>A hotend at printing temperature can be &gt;200°C, with little to no airflow it may STAY at a dangerous temperature for a significant amount of time.</p>
<p>Not only can it burn you if it touches, It may be dangerous if the hotend starts moving <em>after</em> the printer turns off (In systems that cannot passively maintain Z especially)</p>
<p>Aswell, the remaining thermal energy may be enough to &quot;cook&quot; the residual polymers <em>inside</em> the nozzle or hot-zone, which can cause future clogging and extrusion issues.</p>

CC BY-SA 4.0
2023-02-09T14:14:15.723Z
not necessarily cook, but at least make a present clog worse..
Trish
CC BY-SA 4.0
2023-01-06T04:28:09.437Z
2023-01-06T04:28:09.437Z
craftxbox
<p>If there is nothing out of plastic place nearby or inside, it should be fine. It won't take more than a couple of minutes to go down to 100 °C or so, so plastic leftover inside won't cook. Plastic outside from the mount may soften and weaken the assembly, so I would wait until the hotend is at 100 °C or so. With a fan on, it should happen in a minute or so.</p>

CC BY-SA 4.0
2023-01-06T09:43:24.073Z
2023-01-06T09:43:24.073Z
FarO
<p>With a fan cooled, all metal hotend, is there any reason to wait for the hotend to cool, before shutting down power, if the filament has been unloaded?</p>
<p>When leaving the filament on the machine after a print, I’m normally in the habit of waiting until the hotend has cooled down below the filament’s glass temperature before turning the printer off, because without the hotend fan running and the heat block hot, the filament can get softened up in cold end and potentially jam next time. But if there is no filament, would it stand to reason there isn’t enough remaining plastic in the hotend to get heat creep? And it doesn’t matter if the cold end gets hot?</p>

<all-metal-hotend>
Ok to shutdown printer after unloading filament, with no cool down?
ChinchillaWafers
# Ok to shutdown printer after unloading filament, with no cool down?

(Asked by: username_0 on 2022-08-11)

With a fan cooled, all metal hotend, is there any reason to wait for the hotend to cool, before shutting down power, if the filament has been unloaded?

When leaving the filament on the machine after a print, I’m normally in the habit of waiting until the hotend has cooled down below the filament’s glass temperature before turning the printer off, because without the hotend fan running and the heat block hot, the filament can get softened up in cold end and potentially jam next time. But if there is no filament, would it stand to reason there isn’t enough remaining plastic in the hotend to get heat creep? And it doesn’t matter if the cold end gets hot?

**Tags:** all-metal-hotend

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## 2 answers

### Answer by username_1 on 2023-01-06. Score: 1

While heat creep as you describe it *is* a concern, The more pressing reason to let a hotend cool off first is **safety**.

A hotend at printing temperature can be >200°C, with little to no airflow it may STAY at a dangerous temperature for a significant amount of time.

Not only can it burn you if it touches, It may be dangerous if the hotend starts moving *after* the printer turns off (In systems that cannot passively maintain Z especially)

Aswell, the remaining thermal energy may be enough to "cook" the residual polymers *inside* the nozzle or hot-zone, which can cause future clogging and extrusion issues.

> **Comments:**
> **username_2**: not necessarily cook, but at least make a present clog worse..  

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### Answer by username_3 on 2023-01-06. Score: 0

If there is nothing out of plastic place nearby or inside, it should be fine. It won't take more than a couple of minutes to go down to 100 °C or so, so plastic leftover inside won't cook. Plastic outside from the mount may soften and weaken the assembly, so I would wait until the hotend is at 100 °C or so. With a fan on, it should happen in a minute or so.


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