1 Topic by adrian (edited by adrian 2013-04-29 15:02:48)

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Topic: Hottest part of the Extruder? Its not what you think! (Thermal Pics)

So one other thing I did this weekend was grab some thermal pics of the Extruder/HotEnd.

And interesting tidbit; if someone was to ask you what the hottest *exposed* part of the extruder on average was, you'd probably state the brass nozzle just below the heat core, or the heat core itself right ? well... you'd be wrong! smile

Turns out the on average hottest *exposed* part of the Solidoodle Hot End is... the Resistor Wires coming out the side of the core. Makes sense really, since they are acting as heat sinks for the resistor itself, but I still find it slightly chuckle worthy smile

These tests are similar to the heat bed ones I did over in http://www.soliforum.com/topic/2230/the … ed-setups/ , but theres not a lot to share at this stage beyond the pics. If there is interest, I'll do some similar pics on the J-Head Mk-IV and Mk-V I have, and the E3-D all-metal hot end once I receive it in the post. Would also at that stage do a set with lawsy's MkIV Extruder setup and get some prolonged-operation stepper shots.

I think I can also see where peoples PEEK problems stem from. The insulation around the heat core tends to focus the heat upwards. Lots of that heat gets soaked up into the barrel and the lower section of the PEEK insulator. During the cool-down phase, this area became the Hot Spot for the images, and it stayed much hotter for longer than the brass sections around it.

The other observation I have is - Don't skimp on the insulation on those heater wires!! Its obvious why leaded solder melts when used in a joint there as with a set point of 195°C the lead in wires got to peaks of 230°C. Lead-Free solder tends to have a higher melt point, so it might be 'better' to use, but its well into the softening stage of leaded solder thats for sure - but still short of its actual melt point so hence its not an immediate failure.

I didn't get around to removing the insulation to get detailed pics of the extruder setup - I felt it was already apparent enough viewed through the insulation, but if enough people ask for more and when I have another spare hot-end arrive I'll consider stripping it off for some more pics.

EDIT: From the other thread, this disclaimer as reminded by elmoret:
"One thing to bear in mind - the reports are more 'qualitative than quantitive'. What this means is - the comparison between temps in a pic is accurate, but the precise temps themselves can be off by a few degrees due to the vastly different 'emissivity' of the surfaces sampled. "

"Iron" colour scheme here makes it obvious where the heat is concentrated; both the lead in wires and the side of the heater block where the resistor is mounted.
http://farm9.staticflickr.com/8533/8693098652_d864ceb313.jpg
http://farm9.staticflickr.com/8119/8693098640_c08ef03fd1.jpg
You can see here the extruder tip is clearly in shot, yet the lead in wires still beat it for the hot spot in the pic:
http://farm9.staticflickr.com/8118/8693098628_7603fa04f4.jpg
And back to the more friendly 'Rainbow' colour template:
http://farm9.staticflickr.com/8536/8692721960_9166766bd3.jpg
http://farm9.staticflickr.com/8539/8692722014_f0d806c5a9.jpg
http://farm9.staticflickr.com/8114/8691604277_fd331edabf.jpg

So there you have it. As I said, if people find this of value, I'll try and do a more complete set of tests on the various hot ends I have on hand. If nothing else - IR pics are always interesting to look at wink

Adrian

2 Reply by elmoret

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Re: Hottest part of the Extruder? Its not what you think! (Thermal Pics)

One thing to note - you've got a bunch of emissivities in that shot, so the temperatures aren't 100% accurate. Still pretty neat, nonetheless.

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E3Dv6 All Metal Hotend - the premier 3D printing hotend

3 Reply by adrian (edited by adrian 2013-04-29 15:02:05)

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Re: Hottest part of the Extruder? Its not what you think! (Thermal Pics)

elmoret wrote:

One thing to note - you've got a bunch of emissivities in that shot, so the temperatures aren't 100% accurate. Still pretty neat, nonetheless.

Yeah, I put that disclaimer for exactly that reason in the other thread - but should have reiterated it here. Its qualititive rather than quantitive for sure, and no way to compensate for the huge collection of emissives smile The raw files are over in the Bed Thread if you want to adjust the emissives by hand for any particular region

4 Reply by elmoret

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Re: Hottest part of the Extruder? Its not what you think! (Thermal Pics)

adrian wrote:
elmoret wrote:

One thing to note - you've got a bunch of emissivities in that shot, so the temperatures aren't 100% accurate. Still pretty neat, nonetheless.

Yeah, I put that disclaimer for exactly that reason in the other thread - but should have reiterated it here. Its qualititive rather than quantitive for sure, and no way to compensate for the huge collection of emissives smile The raw files are over in the Bed Thread if you want to adjust the emissives by hand for any particular region

Didn't see that, sorry! Great work all around.

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E3Dv6 All Metal Hotend - the premier 3D printing hotend

5 Reply by lawsy

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Re: Hottest part of the Extruder? Its not what you think! (Thermal Pics)

Again, great work!

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6 Reply by adrian

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Re: Hottest part of the Extruder? Its not what you think! (Thermal Pics)

elmoret wrote:

Didn't see that, sorry! Great work all around.

lawsy wrote:

Again, great work!

Cheers guys! smile
I'll wait till my E3-D hot end turns up and then do a '3rd party hot-ends shootout' smile

7 Reply by Zarni

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Re: Hottest part of the Extruder? Its not what you think! (Thermal Pics)

Another cracking post,
Interesting to see the heat transfer to the extruder carriage.
Although obvious now you've got the photo evidence, the heat transfer up the wires is something I never considered.


Errrr, any chance of some images of the extruder stepper with and without the fan on.
Mine makes a racket and I wonder if it is actaully doing much as the heatsink on the back should help a bit. From you images the thermal break going up to the hobbed bolt is plenty good enough so I assume they are just concerned with the motor getting hot after prolonged use, but as it is fairly slow is this going to be a problem?

Can't wait for the shootout. smile

8 Reply by danny

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Re: Hottest part of the Extruder? Its not what you think! (Thermal Pics)

I'm not at all surprised, the lead wires are directly attached to the nichrome,
the nichrome (based on it's gauge) heats to around 1400 degrees centigrade. this picture makes it painfully obvious why so many soldered nichrome hotends break...

(so if you're rebuilding a nichrome hotend, use a linesman splice as well as solder.)

9 Reply by adrian

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Re: Hottest part of the Extruder? Its not what you think! (Thermal Pics)

Zarni wrote:

Errrr, any chance of some images of the extruder stepper with and without the fan on.
Mine makes a racket and I wonder if it is actaully doing much as the heatsink on the back should help a bit. From you images the thermal break going up to the hobbed bolt is plenty good enough so I assume they are just concerned with the motor getting hot after prolonged use, but as it is fairly slow is this going to be a problem?

Its to do more with stopping heat from the stepper softening the filament as well as ensuring it doesn't miss steps - it does actually work quite a bit at reasonable torque levels... Anyway, rather than guessing, in a few weeks I'll see what I can do comparison wise - I'm actually building an entire new stepper/extruder setup at the moment so can happily use that to test it, but will gather it all up again before I drag the thermal camera over again smile

danny wrote:

I'm not at all surprised, the lead wires are directly attached to the nichrome,
the nichrome (based on it's gauge) heats to around 1400 degrees centigrade. this picture makes it painfully obvious why so many soldered nichrome hotends break...

(so if you're rebuilding a nichrome hotend, use a linesman splice as well as solder.)

Hotend pictured is a resistor based one, not nichrome, but your hypothesis more or less is valid just rather the package and presentation different smile

10 Reply by IanJohnson

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Re: Hottest part of the Extruder? Its not what you think! (Thermal Pics)

A Home Depot near me has a Flir i7 in its tool rental department,  I'll have to give that a try one weekend.   I have my printer set up with an enclosure with a vent to blow in air from a space heater so I can do some tests with those variables as well.

11 Reply by op7ical

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Re: Hottest part of the Extruder? Its not what you think! (Thermal Pics)

The other observation I have is - Don't skimp on the insulation on those heater wires!!

I am not sure about this part.  It seems to me that the method of heat flow through the resistor wires is most likely by conduction from the resistor through the wire itself, rather than by radiation (since the hotend metal itself is lower temperature, according to the pictures). 

So by my logic, adding insulation actually makes the heat migration up the wire easier, since it cannot radiate its heat into the air or space around it.  However, if the resistor were just covered with a thin electrical insulator instead, it could more easily dissipate its heat and thus reduce the risk of failure for joints.

I could be wrong, but I'd like to get others opinions on this small point.  Also, it seems clear that the heat is mostly dissipated anyway within a short distance, so it probably won't matter for most people.

12 Reply by ronsii

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Re: Hottest part of the Extruder? Its not what you think! (Thermal Pics)

Here are a couple of pics from an I7, I had it out doing some other work and remembered Ian mentioning trying one and thought I would let you see how it compares with the cam Adrian used. Same here I didn't do anything about emissivity normally I would but this was an off the cuff thing wink

http://i.imgur.com/qLI79bd.jpg

http://i.imgur.com/iF6P7Td.jpg