Hot end jam repeatedly 20 or so minutes into the print.

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Lasivian
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Hot end jam repeatedly 20 or so minutes into the print.

Post by Lasivian »

Ok, starting over in a new thread.

I'm using a V1 Rostock Max with the default nozzle. SeemeCNC Black PLA (also happened with white) with the temp someplace between 190 and 220. (Been trying everything to figure this out)

About 20 minutes into the print the extruder skips repeatedly. (click, click, click) when I disconnect the bowden tube from the hot end the clicking stops. Indicating something is jamming in the hot end. After it fails I can start a new print and it runs up to that point just fine. I can also force extrude from Repetier and it extrudes fine.

This kind of jam repeats itself on every print lasting a similar amount of time regardless of slicing. Also the temp looks fine in repetier but it's acting just as if it was losing temperature.

I disassembled the extruder looking for an issue there and could not definitively find out.

I disassembled the hot end and found 8mm or so of melted PLA in the PTFE tube, melted PLA on the outside of the ptfe tube and on the outside of the upper part of the nozzle. Is this normal?

The last time I pulled the hot end apart it worked fine without this issue for awhile then started again.

Any ideas would be helpful. Thanks
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Re: Hot end jam repeatedly 20 or so minutes into the print.

Post by Polygonhell »

Are you running a fan over the PEEK section of the hotend? V1 Max's didn't ship with them, but they are still needed to print PLA.

Assuming you are running with a PEEK fan, the next thing to do it wait until it jams, stop the printer, pop the bowden tube off at the hotend and try manually feeding filament, manually verify that the issue is back pressure at the hotend rather than something like variation in filament width, and get some idea how much force is required to extrude at the requested temperature. FWIW my experience with SeeMeCNC PLA wasn't very positive, but that was a long time ago and they may have improved the quality.

It's also worth using a thermocouple to verify your hot end is reading the correct temperature, I've seen one thermistor that read 20+C high, i.e. 220 was infact 200C.
Lasivian
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Re: Hot end jam repeatedly 20 or so minutes into the print.

Post by Lasivian »

Yes, there is a fan blowing over the PEEK section of the hotend.

I can push the filament into the hot end by hand, but the PTFE tube shoves itself out, so I can;t get a good idea if i'm just not shoving hard enough or if it's a temperature issue.

I set the printer back to 185 and the extruder started clicking almost immediately so it stands to reason that is too low.

I put a grilling thermometer probe into the back of the hotend and i'm getting reading about 15c lower than repetier is telling me.
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Re: Hot end jam repeatedly 20 or so minutes into the print.

Post by 0110-m-p »

What are your retraction settings? If you retract PLA too far it can jam on restart.
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techstorage
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Re: Hot end jam repeatedly 20 or so minutes into the print.

Post by techstorage »

I have had luck dialing down the feed rate on the LCD under printer options when this would happen to me with PLA. I would start with 80% then go down from there till the back feed skipping stops. I am trying to calibrate my slicer programs to find the best settings.

I haven't seen my hot end jam like you stated, just the extruder back skip with PLA
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Re: Hot end jam repeatedly 20 or so minutes into the print.

Post by Lasivian »

0110-m-p wrote:What are your retraction settings? If you retract PLA too far it can jam on restart.
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Lasivian
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Re: Hot end jam repeatedly 20 or so minutes into the print.

Post by Lasivian »

techstorage wrote:I have had luck dialing down the feed rate on the LCD under printer options when this would happen to me with PLA.
I do not see such an option. I see a speed setting for the extruder in Repetier and it's at 130mm/mind right now. The EEPROM shows

Extr. 1 max. feedrate 40 mm/s
Extr. 1 start feedrate 10 mm/s
Extr. 1acceleration 3500 mm/s^2

Thanks
Lasivian
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Re: Hot end jam repeatedly 20 or so minutes into the print.

Post by Lasivian »

Ran into Johnoly99 in #reprap that said it might be the PTFE tubing inside the hotend. Ordered some replacement, we'll see if that helps.
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Re: Hot end jam repeatedly 20 or so minutes into the print.

Post by Mac The Knife »

try changing your retraction length to 3 mm.
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Re: Hot end jam repeatedly 20 or so minutes into the print.

Post by Lasivian »

Mac The Knife wrote:try changing your retraction length to 3 mm.
Testing that. I believe I increased it because I was getting a LOT of stringing as the head moved between locations.
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Re: Hot end jam repeatedly 20 or so minutes into the print.

Post by Mac The Knife »

That's what I hate about pla,,,, but if your retracts are to long, it creeps up the heat break and solidifies.
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Re: Hot end jam repeatedly 20 or so minutes into the print.

Post by Lasivian »

Mac The Knife wrote:That's what I hate about pla,,,, but if your retracts are to long, it creeps up the heat break and solidifies.
Yes, but I was also getting this while printing a single-wall vase form. So the retraction can't be my only issue since I believe that never retracts.
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Re: Hot end jam repeatedly 20 or so minutes into the print.

Post by Lasivian »

Printing the fan shroud part has helped immensely. I'm guessing the heat was creeping up the hotend. I still have the retraction high but it has not jammed recently. Also I ordered more PTFE tubing to replace the piece in the hot end for a better internal seal.

(Mainly posted for the next person that has this problem)

Thanks
Lasivian
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Re: Hot end jam repeatedly 20 or so minutes into the print.

Post by Lasivian »

It also helped to replace the tube inside the hot end.
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