<p>The heat sink is there to prevent too much heat creep from the hot end up into the the cold end or bowden tube (depending on printer type). The filament in these sections needs to remain <strong>firm</strong>, so it can be driven into and through the extruder. Heat rises and spreads, even through solids, and <em>the printer will not function properly</em> if enough heat rises into those components for filament to soften.</p>
<p>So the hot end needs to be hot... but then we need a fairly quick and clean break where temperatures are back to &quot;normal&quot; again. Heat sinks (and even fans) can help with this. You'll further notice the use of a heat break in the diagram, and all the heat sink material is on the other side of the break from the heater block.</p>
<p>It's further worth noting print head mass contributes directly to issues like ringing, and has an inverse effect on both quality and speed... the lighter the print head, the better things will generally work out. Printer designers would therefore <strong>love</strong> to be able to remove heavy heat sink material from the print head, as that would also allow gains in both speed and quality... but they can't, because this really is absolutely necessary for the printer to function properly.</p>

CC BY-SA 4.0
2024-04-16T14:03:33.900Z
Well, this doesn't _really_ address my question, have you ever tried to push filament directly to the heat block? That is, remove the heat break along with the heat sink and then push filament directly through. That works just fine, you have cold firm filament transitioning very quickly to liquid, why not do that? (picture the gears pushing the filament right above the heater block where the heat break usually is)
Sujal Singh
CC BY-SA 4.0
2024-04-16T14:06:13.620Z
@SujalSingh Heat rises.
Joel Coehoorn
CC BY-SA 4.0
2024-04-16T14:15:19.560Z
Oh, you're suggesting that the plastic would conduct heat upwards and start to soften/melt outside the heater block? Hm, I can see a need for that heat sink then.
Sujal Singh
CC BY-SA 4.0
2024-04-16T14:20:00.490Z
Correct. I added a bit of text to help clarify this.
Joel Coehoorn
CC BY-SA 4.0
2024-04-16T13:41:51.080Z
2024-04-16T15:33:30.763Z
2024-04-16T15:33:30.763Z
Joel Coehoorn
<p>Flip it around - consider that if we could print &quot;upside down&quot; the heatsink may be unnecessary, because heat from the heater would move upward into the nozzle, saving power and making the printer quieter and more efficient.</p>
<p>Of course, making the print stay stuck to the bed despite motion might be a challenge in a bed slinger.   Perhaps an inverted core-XY printer could achieve this ?</p>

CC BY-SA 4.0
2024-04-16T09:34:37.927Z
There definitely exist inverted core-xy printers, for example there's one named positron, but I didn't really understand why printing upside down removes the need for a heat sink? You suggest that the heat would move upwards, but it would just as well conduct downwards, right? So what changed?
Sujal Singh
CC BY-SA 4.0
2024-04-16T13:44:34.470Z
@SujalSingh Heat rises
Joel Coehoorn
CC BY-SA 4.0
2024-04-16T13:58:24.947Z
@JoelCoehoorn I do not think that applies to solids.
Sujal Singh
CC BY-SA 4.0
2024-04-16T14:06:33.953Z
@SujalSingh it definitely still applies to solids.
Joel Coehoorn
CC BY-SA 4.0
2024-04-16T14:12:31.257Z
Am I misinterpreting or are you suggesting that a solid would selectively pick the "upwards" direction to conduct heat but not the downwards direction? If so, shouldn't it conduct heat in every direction it can? If that is true, I don't see how inverting the printer would change anything.
Sujal Singh
CC BY-SA 4.0
2024-04-16T23:29:54.367Z
@SujalSingh yes - heat rises.  Thats why hot-air balloons go up despite having a hole at the bottom.      Gravity doesn't measurably affect heat.   SO if the entire print head was upside down, the heat won't travel up into the new filament as much, possibly removing the need for a heatsink.
Criggie
CC BY-SA 4.0
2024-04-16T23:30:20.350Z
@SujalSingh Perhaps you could try your own experiment - remove the heatsink from your printer and see how it works without one.
Criggie
CC BY-SA 4.0
2024-04-17T01:27:56.340Z
Yes, I have tried pushing filament through directly to the heated block (i.e., with the heat break and the heat sink removed) and it does extrude just fine, but I have never kept the filament stationary long enough to check the thermal conductivity of the filament so maybe it will start to soften outside after a while as @JoeCoohorn's answer suggests, I will try to check that today.
Sujal Singh
CC BY-SA 4.0
2024-04-17T01:39:13.543Z
Maybe I'm missing something here but the hot air example you've provided is for fluids, where hot air would expand which reduces its density and thus creates an upwards buoyant force on the balloon. However, in solids, the particles aren't free to move to form such convection currents, and heat is conducted in all directions equally. What am I missing!?
Sujal Singh
CC BY-SA 4.0
2024-04-17T02:01:52.700Z
@SujalSingh  heat does not move in all directions equally.  Try it yourself - put a hand below a burning candle. then put the same hand above the candle.  Which is hotter ?    Same thing happens inside solids, just harder to detect.   Anything further needs to be in [chat]
Criggie
CC BY-SA 4.0
2024-04-17T02:53:51.993Z
I did not know this phenomenon existed in solids, I'll have to study up a bit about this, thanks!
Sujal Singh
CC BY-SA 4.0
2024-05-11T01:53:13.440Z
@JoelCoehoorn: No, heat does not rise. Warm air rises, because of changes in density. Heat always moves toward cold, trying to equalize the difference and find a balance. Thermodynamics. :-) This is one of my pet peeves, along with 24/7/365 (it's either 24/7, or 24/365, unless you actually mean *24 hours a day, 7 days a week, for 365 weeks*).
Ken White
CC BY-SA 4.0
2024-04-16T03:01:11.753Z
2024-04-16T03:01:11.753Z
Criggie
<p><img src="https://i.sstatic.net/oTLf48LA.png" alt="e3D v6 Hotend" /></p>
<p>I do not understand what purpose the entire heat sink area serves. Obviously, it is to prevent the heat from the heater block from creeping up and melting the filament inside of the heat sink and causing a jam. But what is conducting the heat up? The heat sink! It seems to be creating the problem it solves!? The only reason I can think of why it would be needed is for mounting purposes to a plastic part that would melt otherwise, a problem which I think can be solved with passive cooling by changing the geometry of the part such that the filament is no longer involved in the transitional area.</p>

CC BY-SA 4.0
2024-04-14T15:32:49.917Z
Do you really think after over 12 years of engineering the heat sink is only needed for mounting? You can read more about the hot end theory [here](https://reprap.org/wiki/Hot_End_Design_Theory). There is an overview [here](https://reprap.org/wiki/Hot_End_Comparison); there have been heatsink-less designs, but these have not survived the test of time and development progress...
0scar
CC BY-SA 4.0
2024-04-15T12:54:55.930Z
Old Polytetrafluoroethylene tubes, even w/heat sinks are discolored from heating. Likely, sticking the Polytetrafluoroethylene tube right into the hot end will shorten their life even more.
st2000
<hotend><heat-management><e3d><heat-creep><heat-break>
Why do hotends have heat sinks?
Sujal Singh
# Why do hotends have heat sinks?

(Asked by: username_0 on 2024-04-14)

![e3D v6 Hotend](https://i.sstatic.net/oTLf48LA.png)

I do not understand what purpose the entire heat sink area serves. Obviously, it is to prevent the heat from the heater block from creeping up and melting the filament inside of the heat sink and causing a jam. But what is conducting the heat up? The heat sink! It seems to be creating the problem it solves!? The only reason I can think of why it would be needed is for mounting purposes to a plastic part that would melt otherwise, a problem which I think can be solved with passive cooling by changing the geometry of the part such that the filament is no longer involved in the transitional area.

**Tags:** hotend, heat-management, e3d, heat-creep, heat-break

> **Comments:**
> **username_1**: Do you really think after over 12 years of engineering the heat sink is only needed for mounting? You can read more about the hot end theory [here](https://reprap.org/wiki/Hot_End_Design_Theory). There is an overview [here](https://reprap.org/wiki/Hot_End_Comparison); there have been heatsink-less designs, but these have not survived the test of time and development progress...  
> **username_2**: Old Polytetrafluoroethylene tubes, even w/heat sinks are discolored from heating. Likely, sticking the Polytetrafluoroethylene tube right into the hot end will shorten their life even more.  

---

## 2 answers

### Answer by username_3 on 2024-04-16. Score: 3 | Accepted answer

The heat sink is there to prevent too much heat creep from the hot end up into the the cold end or bowden tube (depending on printer type). The filament in these sections needs to remain **firm**, so it can be driven into and through the extruder. Heat rises and spreads, even through solids, and *the printer will not function properly* if enough heat rises into those components for filament to soften.

So the hot end needs to be hot... but then we need a fairly quick and clean break where temperatures are back to "normal" again. Heat sinks (and even fans) can help with this. You'll further notice the use of a heat break in the diagram, and all the heat sink material is on the other side of the break from the heater block.

It's further worth noting print head mass contributes directly to issues like ringing, and has an inverse effect on both quality and speed... the lighter the print head, the better things will generally work out. Printer designers would therefore **love** to be able to remove heavy heat sink material from the print head, as that would also allow gains in both speed and quality... but they can't, because this really is absolutely necessary for the printer to function properly.

> **Comments:**
> **username_0**: Well, this doesn't _really_ address my question, have you ever tried to push filament directly to the heat block? That is, remove the heat break along with the heat sink and then push filament directly through. That works just fine, you have cold firm filament transitioning very quickly to liquid, why not do that? (picture the gears pushing the filament right above the heater block where the heat break usually is)  
> **username_3**: @username_0 Heat rises.  
> **username_0**: Oh, you're suggesting that the plastic would conduct heat upwards and start to soften/melt outside the heater block? Hm, I can see a need for that heat sink then.  
> **username_3**: Correct. I added a bit of text to help clarify this.  

---

### Answer by username_4 on 2024-04-16. Score: 0

Flip it around - consider that if we could print "upside down" the heatsink may be unnecessary, because heat from the heater would move upward into the nozzle, saving power and making the printer quieter and more efficient.

Of course, making the print stay stuck to the bed despite motion might be a challenge in a bed slinger. Perhaps an inverted core-XY printer could achieve this ?

> **Comments:**
> **username_0**: There definitely exist inverted core-xy printers, for example there's one named positron, but I didn't really understand why printing upside down removes the need for a heat sink? You suggest that the heat would move upwards, but it would just as well conduct downwards, right? So what changed?  
> **username_3**: @username_0 Heat rises  
> **username_0**: @username_3 I do not think that applies to solids.  
> **username_3**: @username_0 it definitely still applies to solids.  
> **username_0**: Am I misinterpreting or are you suggesting that a solid would selectively pick the "upwards" direction to conduct heat but not the downwards direction? If so, shouldn't it conduct heat in every direction it can? If that is true, I don't see how inverting the printer would change anything.  
> **username_4**: @username_0 yes - heat rises.  Thats why hot-air balloons go up despite having a hole at the bottom.      Gravity doesn't measurably affect heat.   SO if the entire print head was upside down, the heat won't travel up into the new filament as much, possibly removing the need for a heatsink.  
> **username_4**: @username_0 Perhaps you could try your own experiment - remove the heatsink from your printer and see how it works without one.  
> **username_0**: Yes, I have tried pushing filament through directly to the heated block (i.e., with the heat break and the heat sink removed) and it does extrude just fine, but I have never kept the filament stationary long enough to check the thermal conductivity of the filament so maybe it will start to soften outside after a while as @JoeCoohorn's answer suggests, I will try to check that today.  
> **username_0**: Maybe I'm missing something here but the hot air example you've provided is for fluids, where hot air would expand which reduces its density and thus creates an upwards buoyant force on the balloon. However, in solids, the particles aren't free to move to form such convection currents, and heat is conducted in all directions equally. What am I missing!?  
> **username_4**: @username_0  heat does not move in all directions equally.  Try it yourself - put a hand below a burning candle. then put the same hand above the candle.  Which is hotter ?    Same thing happens inside solids, just harder to detect.   Anything further needs to be in [chat]  
> **username_0**: I did not know this phenomenon existed in solids, I'll have to study up a bit about this, thanks!  
> **username_5**: @username_3: No, heat does not rise. Warm air rises, because of changes in density. Heat always moves toward cold, trying to equalize the difference and find a balance. Thermodynamics. :-) This is one of my pet peeves, along with 24/7/365 (it's either 24/7, or 24/365, unless you actually mean *24 hours a day, 7 days a week, for 365 weeks*).  

---

