Rebuilt extruder and now having load and extrusion issues
So my weekend started off like this
I rebuilt the extruder with the following changes from my previous setup:
- Using R5 body and cover as the fin on my cover had melted
- New part fan (tired of the rattle)
- New heat break (ordered from Prusa)
- New hot end PTFE tube (ordered from Prusa)
- E3D copper heat block
- Fresh 0.4 nozzle (same size I've been using)
- Added an E3D sock.
Other than a burning wax smell when it heats up (which I have so far been chalking up to the block seasoning itself or the sock and I haven't noticed any signs of issue from it) my pre-flight checks and recalibration went fine including feeding filament through using the Move axis function.
My trouble started when I went to do my Live Z setup (I use a 75x75x0.2mm square rather than the built-in function). When I told it to load to the nozzle (my test isn't sliced for the MMU) it proceeded as normal, the idler door moved to indicate the filament made it, it made a few extruder moves and then ejected the filament. It then repeated the process in a second attempt and finally failed (after fully ejecting) and asked for attention.
My assumption was the IR sensor and as I fiddled with it I did find some adjustment to the tower was needed. The issue still persisted however. Ultimately I go through the Live Z by removing the MMU -> Extruder PTFE and festos and manually guiding the filament. It did the same "reject and try again" as described above, but on the retry it did start working. It was then able to complete the Live Z test with no further issues.
Next I reinstalled the PTFE and festos and ran a 20x20x20mm block I use to check my ghosting and the IR sensor (when I was having IR sensor issues it wouldn't make it through without help). As this is also not sliced for the MMU I had to tell it to load to the nozzle again and this time it ran fine with no issues. So my assumption was that all was now happy, but I left further testing until this morning so I would be by the printer (in the event the wax smells is not just things seasoning themselves).
This morning I kicked off a 2 color Benchy from gcode I have previously used and it appeared to load the filament fine. Nothing was laid down for the pre-print purge line and when it moved to the tower base nothing was extruded there either. I stopped the print, but it could not eject the filament. When I looked at it this after noon I found I could not pull the filament out of the extruder until I warmed it up. At that point I found notches ground both at the extruder and at the MMU ends of the filament (my assumption is the later happened when it couldn't retract).
Playing with it more this evening I found the tips look different than previously. Historically they have had a bullet shape with an occasional point, but now I am pretty consistently getting tips that look like this:
After more fiddling I gave Benchy another try and this time it looked good as it started off laying down filament in the purge line. As it got to the end of movement to the right, however, the filament stopped moving (rested my finger against it at the buffer exit). This is what the first layer of the tower ended up looking like (it should be a solid bottom):
Here is what the extruder looked like after I terminated the print and it had ejected (with no help) the filament:
Note that the wires holding the sock in place are well above the nozzle tip. They are not catching anything.
As noted above, my initial thought was that I had IR issues (which I did, but that appears fixed), but this appears to be some feed related issue. Other than taking the MMU->extruder festo off I have not made any adjustments to the MMU since it last worked before the jam that led to the first pic. The set screw on the extruder motor is tight and positioned correctly on the flat spot. Tightening and loosening the idler door seems to make a difference for load issues, but not for the failure to extrude.
Anyone have any ideas?
RE: Rebuilt extruder and now having load and extrusion issues
Smells like PTFE issues. Check the ID of the tube and make sure it's not deformed, seated correctly, and not free to wiggle. I had no end of funky unload failures when I'd accidentally grabbed some larger ID cheap tubing instead of the proper Prusa stuff.
It's also been reported that it "seasons" a little and firms up with use resulting in better shaped tips, but I can't speak to that claim.
RE: Rebuilt extruder and now having load and extrusion issues
I was afraid any answers were going to go to opening the extruder 😔 Just so annoying...
For what it's worth it is a Prusa tube. I ordered a few with the replacement heat break so I'd have some on hand.
RE: Rebuilt extruder and now having load and extrusion issues
Yeah, it should be fine but it's worth spot-checking the QC. Unfortunately your description just smells of molten plastic getting somewhere it shouldn't and causing jams.
TBH this is why I like the skelestruder; it's got some major serviceability/QoL improvements.
RE: Rebuilt extruder and now having load and extrusion issues
I suspect you're on to something. I just tested the 2 spares I have and while both appear to have a 1.8mm bore, they are both very difficult to push filament through.
When they are cold I simply can't get the filament through. After holding and fiddling with them for a few minutes I can get the filament through, but if the curvature of the filament doesn't match up with the remaining slight curvature of the tube it is still difficult (though possible) to slide the filament all the way through.
I pulled the tower and idler door and was relatively (about what I'm used to) push filament through and make it extrude.
So it seems like the tubes are right on the edge where if the dimensions of the filament is at all off things might be binding up.
RE: Rebuilt extruder and now having load and extrusion issues
So I've been futzing with it and having no success. Until today I could manually push filament through with the steppers off or advance filament with the Move Axis function from the menu and it would extrude just fine. Point it back at Benchy and the example above is what a better try looks like.
This morning I took the extruder apart again (or enough to get the hot end out). The PTFE is clear, was inserted correctly and fully, and is actually the most cooperative of the 3 tubes I have on hand when feeding filament through it.
With the radiator off I ran the temp up to 250 and was able to run a needle all the way through both directions and there was no sign of any blockage.
Put it all back together and now it's back to not loading to nozzle. By manually advancing the extruder as well as measuring it afterwards I found that it's loading just over 75mm from the point the gears will grab the filament to the point it won't move any further. I can't manually force it through either.
I can't be sure without taking things apart again and measuring, but by eyeballing it, it appears that 75mm takes it roughly to where the heatbreak and nozzle meet. Does that sound right?
RE: Rebuilt extruder and now having load and extrusion issues
If you can examine the end of the filament, is there any chance of it having the 2.2 mm stub? Or even a stringy end that is folding back creating a 2.2 mm total diameter? That is, 1.75 filament plus a 0.5 mm thread? This doubled over thread would make it down to the heat break step, then jam.
Or if something has melted and is lodged in the lower end of the heat break, like this shard that came off a PolyCarb filament, it could stay in the heat break forever ... or until manually removed:
RE: Rebuilt extruder and now having load and extrusion issues
Sounds about right for position. Maybe check for a) PTFE shards as well, and that there's no junk between the heat break and nozzle. The former can obviously clog stuff and who knows, maybe you've got a bit of galled metal or something else stopping the filament from entering fully.
Can you push filament through if you remove the nozzle entirely?
As an aside, for MMU I made a useful discovery; I'm using PC4-M6 fittings between the MMU and extruder; specifically the non-passthrough ones. I've found these are narrow enough they will jam on problematic filament heads with strands/junk, thereby stopping the junk from making it to the gears/PTFE and jamming in there instead, causing MMU layer skips - since it sees the filament never makes it to the gears. But good tips will pass through just fine. So there's something to be wary of opening yourself up to if you do things like passthrough fittings and wider PTFEs between MMU and extruder.
RE: Rebuilt extruder and now having load and extrusion issues
If you can examine the end of the filament, is there any chance of it having the 2.2 mm stub? Or even a stringy end that is folding back creating a 2.2 mm total diameter? That is, 1.75 filament plus a 0.5 mm thread? This doubled over thread would make it down to the heat break step, then jam.
Or if something has melted and is lodged in the lower end of the heat break, like this shard that came off a PolyCarb filament, it could stay in the heat break forever ... or until manually removed:
Nope. You can see an example of the tips in the first post. If anything it is uncharacteristically smooth/narrow compared to what I was used to before the rebuild.
As far as anything being stuck the PTFE, heat break, block, and nozzle are all brand new and the only thing they've seen so far is PLA. I certainly could have missing something, but I checked the PTFE before inserting it and there was no debris I could see. Similarly in my work on it today I did not see any sign of debris or a clog while I had things apart (though I did not remove the nozzle or heat break from the block).
RE: Rebuilt extruder and now having load and extrusion issues
Something something when you've eliminated the obvious, all that remains is the improbable...
I'd start there nozzle/HB disassembly sucks but for all we know there's a dent or some other defect/junk you can't see that's keeping filament from passing through normally.
RE: Rebuilt extruder and now having load and extrusion issues
Sounds about right for position. Maybe check for a) PTFE shards as well, and that there's no junk between the heat break and nozzle. The former can obviously clog stuff and who knows, maybe you've got a bit of galled metal or something else stopping the filament from entering fully.
Can you push filament through if you remove the nozzle entirely?
I haven't tried yet. I was able to push it through with the nozzle in place prior to this morning's work even though printing wasn't working. I can no longer do that right now.
As an aside, for MMU I made a useful discovery; I'm using PC4-M6 fittings between the MMU and extruder; specifically the non-passthrough ones. I've found these are narrow enough they will jam on problematic filament heads with strands/junk, thereby stopping the junk from making it to the gears/PTFE and jamming in there instead, causing MMU layer skips - since it sees the filament never makes it to the gears. But good tips will pass through just fine. So there's something to be wary of opening yourself up to if you do things like passthrough fittings and wider PTFEs between MMU and extruder.
In this case it's choking on fresh cut ends, so it's not a tip issue going in and coming out it always has that oddly flat and nearly filament width tip.
RE: Rebuilt extruder and now having load and extrusion issues
It's a blue sky out thought - that end shown in the first set of images, looks almost like it broke then fed into the melt zone. Most filament ends unloaded are rounded and a bit of stringy - I have never seen a broken piece of filament upon unload. So either it broke in a really odd way, or there is something hard in the melt zone blocking the filament, that leaves a sharp impression on the filament that you are trying to load.
Are you absolutely positive that nozzle has never been used with anything, or didn't have debris dropped in during assembly by you or someone else? A stray bit of Teflon, some PETG or ABS, or? Might be worth cranking the nozzle up to 300c and try extruding. It probably won't push out Teflon, but if it's anything else remotely like filament...
This is also out in blue sky territory, but the heater cartridge wires are not insulated as they leave the cartridge ceramic filler. The wire wrap job holding the sock on seems to pass pretty close to where I'd expect those heater wires to be exposed. Worth a look under a magnifier, just to be confident there isn't some odd thing going on there.
RE: Rebuilt extruder and now having load and extrusion issues
It's a blue sky out thought - that end shown in the first set of images, looks almost like it broke then fed into the melt zone. Most filament ends unloaded are rounded and a bit of stringy - I have never seen a broken piece of filament upon unload.
I agree that is what it looks like. Though based on the physical action I'm seeing I think it's simply that it stops and the "broken" end is simply the end that I fed in, just barely melted.
Hmmm... I wonder if that might not be it actually... Maybe the heat brake isn't getting hot enough and the obstruction I'm running into is the interior step? The heater core and thermoresistor appear to be working as expected (normal-ish time to temp, no weird fluctuations, etc..). It would be weird for the core to be broken and not heating to the desired temp and the thermoresistor to be broken and reading high, but I guess we are getting to the realm of the weird...
Are you absolutely positive that nozzle has never been used with anything, or didn't have debris dropped in during assembly by you or someone else? A stray bit of Teflon, some PETG or ABS, or? Might be worth cranking the nozzle up to 300c and try extruding. It probably won't push out Teflon, but if it's anything else remotely like filament...
Anything is possible, but it's a fresh nozzle that hasn't been used for anything other than PLA. I was careful to check everything before assembly, but anything is possible. Hopefully I'll get some time to pull the nozzle today take a look.
This is also out in blue sky territory, but the heater cartridge wires are not insulated as they leave the cartridge ceramic filler. The wire wrap job holding the sock on seems to pass pretty close to where I'd expect those heater wires to be exposed.
What you can't see well from that pic is that the wires that come down and wrap under are at an angle. I put them on after the entire hotend was assembled and before it was installed in the extruder. The wires are angled specifically to avoid touch the heater or thermo.
RE: Rebuilt extruder and now having load and extrusion issues
Hmmm... I wonder if that might not be it actually... Maybe the heat brake isn't getting hot enough and the obstruction I'm running into is the interior step?
If that's the case you might be able to get it to soften enough by just blocking the hot end fan briefly to let the heatsink/heatbreak warm up a bit.
RE: Rebuilt extruder and now having load and extrusion issues
Based on everything you've tried, and trying to imagine what might be happening, some unmeltable thing packed into the upward end of the nozzle fits the problem pretty well. A stray piece of PETG, ABS or polycarbonate that was rattling around in all the MMU teflon tubing and then somehow made it to the extruder? Did any parts in the MMU need tapping or were self tapping screws used in places where debris may have gotten into the works?
In the end, pushing melted plastic out a nozzle is pretty simple: you need heat and pressure. If you have heat, and the Bondtech is pushing... or trying to push: either something is pinching or holding the filament above the Bondtech, or something below the Bondtech is pinching or holding the filament, or some foreign object is blocking the melt from exiting the nozzle.
As much as I am sure you don't want to do this: pulling the nozzle and ensuring the filament can be driven out the hot end under extruder power will at least eliminate the MMU and Bowden tubes from being the problem. It also gives you access to the back side of the nozzle. Heck, I once took apart a carburetor and found an ANT plugging the main jet. Strange things do happen.
RE: Rebuilt extruder and now having load and extrusion issues
As much as I am sure you don't want to do this: pulling the nozzle and ensuring the filament can be driven out the hot end under extruder power will at least eliminate the MMU and Bowden tubes from being the problem.
The MMU is definitely not at issue here. It was working fine before the jam that led me to bending the heat break (and that jam was self inflicted) and other than removing the festo from the selector it has not been touched. Additionally I know the IR sensor is seeing the filament and engaging the extruder as expected. The 75mm I measured above was done with the festo on the extruder removed and feeding directly into it.
It is certainly possible, however, that during setting up the filament into the MMU that something could have gotten into the bowden and pushed through to the nozzle. The next step is definitely removing the nozzle and then we'll see what we see at that point.
RE: Rebuilt extruder and now having load and extrusion issues
I'm not trying to blame the MMU, except that is a large mechanism that a small piece of debris can hide in, and eventually make it's way to the nozzle..
RE: Rebuilt extruder and now having load and extrusion issues
I get it. Just responding with relative to what I did or didn't do regarding it.
Just had the bright idea to warm it up and stick my multimeter's thermoresistor on it and see what it says, but having never actually needed that probe before I have no idea what I've done with it and it's not in the places I would expect to have left it. More annoyingly is that I know there are at least 2 and possibly a 3rd running around somewhere. So much for an easy check I could make while waiting on time to remove the nozzle 🙄
RE: Rebuilt extruder and now having load and extrusion issues
Gah. If it's not one thing...
Since I had it heated up I thought I'd play with it a bit anyway. At the normal 215 I noticed when I pushed the filament in as far as it would go (~75mm) and left it for 10 second or so and then quickly pulled it out, the filament wasn't even warm to the touch. Maybe a few degrees above nominal, but nothing to suggest it was anywhere near melting.
I ran the temp up to 230 and then was able to manually extrude filament, though it was not smooth as if suggesting that it was still on the cold side. When I pulled the filament out the tip is not formed correctly at all. Kinda similar to what you might see from a cold pull if you didn't let it cool enough before pulling.
I went to try Move Axis to advance the filament, but I think the bad tip left something behind to jam the top of the PTFE as I now can't get filament further than the bottom of the gears 🙄
I think these findings definitely point towards things not heating as they should. I really need to find that thermo probe...
RE: Rebuilt extruder and now having load and extrusion issues
At least it was an easy jam to clear (would be nice if we didn't have to remove the door...).
At 230 I could extrude with no issues using the Move Axis function. Is there a way to change the temp for a print while it's running or do I need to re-slice for the higher temp? As I was seeing a difference between manual extrusion and extruding during a print I'd like to see how it prints at this issue for comparison.
Really need to find that thermocouple to get a better idea about where the issue might be.