I’ve become adept at extracting and disassembling the extruder due to the large number of clogs I’m experiencing. this is usually during multi-hour prints when a failure is particularly galling. by the time I get it apart, the extruder enclosure is still very hot. so clearly the filament is becoming too ductile way before it enters the melt zone. the globs are wrapped around the gear. this seems like an extruder design issue. obviously, the chamber is enclosed and heat is building up. has anyone had the same issue and come up with a strategy to keep the extruder gear path cooler for long prints?
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Which type of filament? If PLA are you leaving the door open?
Certainly laid my hands on the extruder a bunch and not even warm
I’ve printed some 8 hour prints and I just a couple of days ago swapped out the plastic extruder gear for metal throughout and I can say that the all of the stock parts were in pristine condition. Definitely no throw-away parts. The plastic drive gears were fine, as were the gears that contact the filament.
You do anything with speed settings or temperature settings?
The way the extruder is built, if it were getting hot, all the grease will liquify and pool at bottom so have you seen that?
Sometime I have to print a lot in glow PLA, which is a heat creep nightmare once you need to slow down for details or lots of retractions.
The usual ‘fixes’ won’t work for me as this time of the year I have no issues reaching 30 degrees in the house - Celsius that is.
Even on 20 degree days the heat creep happens with the door and lid wide open.
I experimented a bit with a new front housing and a larger (air) volume blower motors rather than the flimsy fan.
Worked a treat initially until I found out there isn’t enough space left when printing things all the way to the right on the plate.
Now trying to make the design smaller and with the blower fan embedded rather than mounted onto the right side.
By worked I mean I did not experience constant blocks during test prints that soften the filament too much in the past.
It still won’t address the general over-heating issue of the hotend’s upper parts.
For the new version I want the fan, just one fan, on the front of the housing module.
Sadly I am only good at basic designs and struggle badly organic shapes.
Makes it very time consuming to design matching air channels to pull in chamber air to go through the cold end and the rest of the head housing to keep things cool.
Initial checks with my little FLIR camera revealed that even with the bed at just 55 degrees it is very hard to get any real cooling going in the print head.
I came to the realisation that while PLA can be handled with a few modifications or by leaving the printer open in a cool enough room the same can’t be said for other filaments.
A lot of my issues vanished with the E3D hotend I installed by I won’t that for filled filaments as it ruins the inner coating too fast.
Hoping to get the time for it this summer I want to add another hose going into the printer.
An air line from a small airbrush compressor feeding pre-cooled air into a slim box over the hotend fan.
the remaining air is split to cool the extruder a bit as there the heat creep often means a total block right after the transport wheels.
In case it works out I will report back with plans and instructions.
I’d actually been giving this some thought. I tried doing PLA support on a PETG print and it gave me fits. The PLA would load in a printhead that had been printing PETG, in a build chamber that had been printing PETG, with predictable results.
I was thinking I could force air down the tube the filament follows to get to the print head. It wouldn’t be a lot of air, but it would be cool air, and it’d vent right into the area where the filament usually blobs-out and jams the extruder.
Something like an aquarium aerator pump would probably do the trick nicely… mated to a Y fitting right at the back of the machine.
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No chance to get any meaningful amounts of air through the same tube with the filament inside.
I was thinking in the area of a thin and very flexible fuel hose, as for law movers and such.
Only issue I encountered last night was my calculator complaining.
My little airbrush compressor has a much higher airflow than my aquarium air pumps but still only about 7% of the air volume just the side fan for the hotend delivers.
At least according to my simple fill the bag with air test…
Means that even if this air would be much cooler than the chamber air it would still not be enough to cool things.
We would need a pump, not a compressor to get a matching or better airflow 
Of course I totally ignored math, common sense and logic to try anyway 
I cut the hose in half after plugging the end so the air would go through the hotend fins from the back.
Like a crossflow to the build in fan.
To my surprise the hotend cooled down from 230 to 100 about 8 sec faster than with just the fan.
Nowhere near enough to make a dint but at least it confirms that better/more cooling helps.
Then I thought that so far my main issue was with the extruder blocking up badly while removing the filament from the hotend was childs play by comparison.
Got the glow filament out, changed to the hardened steel hotend and started a dreadful lithopane print that always failed with a blocked extruder.
This time though I wedged the hose in there so the air would go through the area after the transport wheels - more or less.
Made it further than usual but the print still failed once my hose somehow ended in the void with the filament to cause a nightmare jam LOL
Put it all back together, grabbed a beer and started thinking.
Grabbed another beer once the thinking did not come up with conclusions to then go through some pics of my old printers in action…
What’s the main difference between those that simply never jammed up and those that did?
The former were slow, had rather huge hotends by modern standards and were fully open around them, with the fan screwed right onto the cooling block.
Those sometimes struggling with certain filaments and too many retractions had either much smaller (shorter) hotends or the head with an enclosure around.
The most important difference though was or is that all the well performing ones had a teflon liner between extruder and hotend in a housing that wouldn’t allow the filament to bend away or get compressed - too tiny gaps.
IMHO we have two problems making each other worse:
An enclosed print head that gets cooled by the hot air inside the print chamber.
A too short neck on our hotends with a too inefficient heat break and heat sink sitting right over the hot extruder with no isolation.
The front fan blows into the head, same as the hotend fan, which relies on those tiny holes to breathe.
The entire design works as advertised but is not optimised for air flow and certainly no one considered that PLA isn’t the only filament out there - we can’t always leave the door and lid open…
The higher the chamber temp or the closer to the plate the head still is the more cooling issues we face.
Imagine the chamber going to over 70 degrees - how is there any cooling happening where it matters…
Since I use the E3D my PLA problems disappeared together with a lot of other issues.
But I can’t replace those costly things on a regular base to print abrasive filaments with them.
And a jam with those is a total pain and can mean having to dispose of the hotend.
Will do some more thinking and tinkering …
The tube ID is 2.5mm and the filament is only 1.75. So the tube is almost 50% bigger than the filament. Air will definitely flow. And I’m not convinced very much air is required at all.
The biggest benefit might be to the filament in the tube itself. All the time it’s slowly feeding through the tube, it’s pre-heating. The filament doesn’t jam immediately when it’s loaded, the printer has to run for a bit. The temp of the area of the “infeed” at the top of the extruder probably doesn’t change much when new filament is loaded. The filament has to get hot enough to buckle, but it doesn’t stay in this area very long. I think it might actually the “preheat” that’s the primary issue. If so, even a little airflow will remove some heat. And a few degrees of heat removal could be all it’d take…
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