<p>Full definite answers on your questions are hard be given, there are a few parameters affecting the clogging of all-metal hotends.</p>

<p>All-metal hotends are considered so-called "upgrades" for printers while in fact they usually cause more problems. For high temperature filaments, like PC and some Nylons, etc. (printing temperature above 250&nbsp;&deg;C)  you require a hotend that can withstand higher temperatures for prolonged use of the hotend. The problem is that heat creep (heat climbing up the throat/heat break) causes low temperature melting filaments to become prematurely soft and cause problems when retracted.</p>

<p>This requires the printer operator to provide enough cooling air to the coldend of the hotend assembly (usually the part where the cooling fins are) to dissipate heat creeping up the heat break and carefully tune printing temperature and retraction length.</p>

<p>Note that Ultimaker Cura uses quite large retraction values (default 6.5&nbsp;mm), which work perfectly for the UM3E. This could be closely related to the compression effect of the filament in the Bowden tube. The all-metal hotends from the UM3 are perfectly capable of printing low temperature filaments, so if dialed in correctly, such hotends are not only to be used for high temperature filaments.</p>

CC BY-SA 4.0
2019-08-26T13:57:03.193Z
+1 for "All-metal hotends are considered so-called "upgrades" for printers while in fact they usually cause more problems"
R.. GitHub STOP HELPING ICE
CC BY-SA 4.0
2019-08-26T16:11:04.250Z
How about the case of having the head too close to the bed, can the molten plastic climb up the heat break?
Mr.UNOwen
CC BY-SA 4.0
2019-08-26T18:03:55.147Z
@Mr.UNOwen It is hard to imagine what is going on inside the heatbreak. The heatbreak diameter is usually larger than the filament diameter, but also the molten filament has tack (sticks) to the wall sealing the gap. Repetitive retraction and possibly too much pressure will cause "mushrooming" resulting in the hotend to clog.
0scar
CC BY-SA 4.0
2019-08-27T05:52:43.570Z
I'm going to give it one more try with 1.5 retraction. +1* for all the help. Edit: +1 once my reputation is high enough to do so. :P
Mr.UNOwen
CC BY-SA 4.0
2019-08-29T22:40:29.707Z
So I've dropped retraction to 1.5 and tried 215c and 225c with PLA. The print slowly chokes out, with it initially flowing smoothly. When pulling out the filament, I see a spiral groove around the filament.
Mr.UNOwen
CC BY-SA 4.0
2019-08-31T11:58:25.997Z
+1. The heat propagation to the cold part is indeed the main problem of the all-metal hotends. With small temperature increase in hot part the cold part increase non proportionally higher. I found this when switched to PETG with higher temperature of the hotend. Basically measuring temperature of the cold part showed that it become too close to solidifying temperature of the filament. The fast solution for me was to use two fans in parallel on top of each other (as some HP power supplies do).
Serge Rabyking
CC BY-SA 4.0
2019-08-26T13:35:20.363Z
2019-08-26T13:35:20.363Z
0scar
<p>So my goal was to print in a variety of materials with my CR10, but all attempts up to now have failed. I've tried a variety of all-metal hot-ends (except Micro Swiss) with no success. For those with a similar Creality printer that successfully print with all metal ends, how sensitive are they? Do they only print with high temp materials? Is a head too close to the bed enough to jam it? Is a 5&nbsp;mm retraction prone to jam it? Do I need to stick to a premium brand when it comes to all metal hot ends?</p>

CC BY-SA 4.0
2019-08-26T09:00:00.113Z
A 5 mm retraction is definitely enough to clog the hot end. Usually you shouldn't use more than 2-3 mm on an all metal hotend.
If that results in clogging, either go back to a PTFE-lined hotend, or go direct drive.
towe
CC BY-SA 4.0
2019-08-26T11:18:25.503Z
If that's true then all metal hotends are unusable with bowdens, which seems unlikely and mechanically implausible.  The first 3-5 mm of retraction don't pull the filament back out of thethe hotend at all. They only relieve pressure in the bowden.
R.. GitHub STOP HELPING ICE
CC BY-SA 4.0
2019-08-26T11:21:08.533Z
While 5 mm retraction may be too much for some setups, it is not for others: e.g. the UM3 all metal hotend is capable of handling 6.5 mm of retraction (default Ultimaker Cura setting). You should also look into the cooling of the coldend/fins. It is usually heat creep that causes the clogging (which happened to my UM3 once when the cooling fan didn't rotate anymore because of debris in between the blades).
0scar
CC BY-SA 4.0
2019-08-26T11:27:00.040Z
BTW to measure how much is compression in the bowden, mark on the filament with a sharpie after it's been pressurized by extrusion (manual or under printer control), then pinch the idler lever to release it and measure how far the mark moved.
R.. GitHub STOP HELPING ICE
<hotend><creality-cr-10>
How sensitive are all-metal print heads?
Mr.UNOwen
# How sensitive are all-metal print heads?

(Asked by: username_0 on 2019-08-26)

So my goal was to print in a variety of materials with my CR10, but all attempts up to now have failed. I've tried a variety of all-metal hot-ends (except Micro Swiss) with no success. For those with a similar Creality printer that successfully print with all metal ends, how sensitive are they? Do they only print with high temp materials? Is a head too close to the bed enough to jam it? Is a 5 mm retraction prone to jam it? Do I need to stick to a premium brand when it comes to all metal hot ends?

**Tags:** hotend, creality-cr-10
> **Comments:**
> **username_1**: A 5 mm retraction is definitely enough to clog the hot end. Usually you shouldn't use more than 2-3 mm on an all metal hotend. If that results in clogging, either go back to a PTFE-lined hotend, or go direct drive.  
> **username_2**: If that's true then all metal hotends are unusable with bowdens, which seems unlikely and mechanically implausible.  The first 3-5 mm of retraction don't pull the filament back out of thethe hotend at all. They only relieve pressure in the bowden.  
> **username_3**: While 5 mm retraction may be too much for some setups, it is not for others: e.g. the UM3 all metal hotend is capable of handling 6.5 mm of retraction (default Ultimaker Cura setting). You should also look into the cooling of the coldend/fins. It is usually heat creep that causes the clogging (which happened to my UM3 once when the cooling fan didn't rotate anymore because of debris in between the blades).  
> **username_2**: BTW to measure how much is compression in the bowden, mark on the filament with a sharpie after it's been pressurized by extrusion (manual or under printer control), then pinch the idler lever to release it and measure how far the mark moved.  

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## 1 answers

### Answer by username_3 on 2019-08-26. Score: 2

Full definite answers on your questions are hard be given, there are a few parameters affecting the clogging of all-metal hotends.

All-metal hotends are considered so-called "upgrades" for printers while in fact they usually cause more problems. For high temperature filaments, like PC and some Nylons, etc. (printing temperature above 250 °C) you require a hotend that can withstand higher temperatures for prolonged use of the hotend. The problem is that heat creep (heat climbing up the throat/heat break) causes low temperature melting filaments to become prematurely soft and cause problems when retracted.

This requires the printer operator to provide enough cooling air to the coldend of the hotend assembly (usually the part where the cooling fins are) to dissipate heat creeping up the heat break and carefully tune printing temperature and retraction length.

Note that Ultimaker Cura uses quite large retraction values (default 6.5 mm), which work perfectly for the UM3E. This could be closely related to the compression effect of the filament in the Bowden tube. The all-metal hotends from the UM3 are perfectly capable of printing low temperature filaments, so if dialed in correctly, such hotends are not only to be used for high temperature filaments.

> **Comments:**
> **username_2**: +1 for "All-metal hotends are considered so-called "upgrades" for printers while in fact they usually cause more problems"  
> **username_0**: How about the case of having the head too close to the bed, can the molten plastic climb up the heat break?  
> **username_3**: @Mr.UNOwen It is hard to imagine what is going on inside the heatbreak. The heatbreak diameter is usually larger than the filament diameter, but also the molten filament has tack (sticks) to the wall sealing the gap. Repetitive retraction and possibly too much pressure will cause "mushrooming" resulting in the hotend to clog.  
> **username_0**: I'm going to give it one more try with 1.5 retraction. +1* for all the help. Edit: +1 once my reputation is high enough to do so. :P  
> **username_0**: So I've dropped retraction to 1.5 and tried 215c and 225c with PLA. The print slowly chokes out, with it initially flowing smoothly. When pulling out the filament, I see a spiral groove around the filament.  
> **username_4**: +1. The heat propagation to the cold part is indeed the main problem of the all-metal hotends. With small temperature increase in hot part the cold part increase non proportionally higher. I found this when switched to PETG with higher temperature of the hotend. Basically measuring temperature of the cold part showed that it become too close to solidifying temperature of the filament. The fast solution for me was to use two fans in parallel on top of each other (as some HP power supplies do).  

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