Strange Jamb

[CalifDan]

Maybe someone can help me with this. I have certainly had a history of jambs with the printer, but this is a new one. I switched the i3v over to 3mm and have not had any jamb problems since. Until yesterday.

I am printing a fairly large part. It is a replacement for the extruder support to allow the installation of a Bulldog extruder and incorporate auto bed leveling. Once I get the work all done and working, I will share the effort.

I prototyped the part about a week ago. No problems with that print. Yesterday I tried to print the part again as adjusted from the prototype. I used the same print settings and the same filament. About half way through it quit feeding filament. The filament was eroded by the extruder wheel and stopped feeding. This happened twice and not in the same spot. Simply resetting the feed allowed me to start over. There was no jamb in the extruder itself. I could easily feed filament through by hand.

I tried several prints today and the same problem, except that today, several of the attempts did not seem to be related to the extruder wheel. The wear when the jamb occurred did not seem deep enough to dissuade the feed. However, on the last one, tightening the extruder idler wheel did allow the filament to restart feeding.

I have tried changing temperature. I did the original prototype starting at 200 first layer and 190 after. It turned out a great looking part. I have adjusted the temps up as high as 210 and I have adjusted the feed rate down thinking that maybe it was trying to push too much through.

I also have the retract set to 3mm and it is set to retract when crossing perimeters. I wonder if that back and forth is causing enough wear to cause the problem. I have tried looser and tighter on the idler.

I took the extruder apart and made sure it was clear. Frankly, each one of these "jambs" has not prevented me from extruding a nice stream through the tip by hand without any changes other than stopping the print, releasing the servos and opening the extruder and pushing the filament.

I am open to any ideas.

CalifDan

[AbuMaia]

How easily does the filament feed off the spool? Could it be getting tangled and snagged there, and the extruder can't pull it?

[CalifDan]

How easily does the filament feed off the spool? Could it be getting tangled and snagged there, and the extruder can't pull it?

I will look at that. I have not noticed that as a problem with this filament, but it might not take much to cause the problem.

Edit: Did the print and it appears that the feed is the problem. I need to make some changes to how that works. Thanks AbiMaia!!

[CalifDan]

I want to throw this back up to the top. I do not think this is a filament problem caused by tension from the spool.

These failures, when they occur are at areas of a part that are small. I have retraction set to retract 3mm and I am printing PLA through a .4 head (Hexagon) at 190C. The failure occurs at the feed bolt and it wears into the filament enough to stall the feed.

I am wondering if the problem is associated with the back and forth of the retraction? Maybe in conjunction with a lot of filament (3mm) feeding down to a very small print area. This does not allow the filament to advance much and any wear would be exaggerated with multiple retractions and advances.

What I am wondering is how to solve the problem without messing up the prints. Turning retraction on greatly improved the quality of the prints. I am curious what the community thinks. Would turning the temperature up reduce the back pressure enough to prevent the retraction - extension process from wearing into the filament? I am going to experiment, but sure would like to solve this issue.

[RAMTechRob]

I would bet you are running too cold. I run PLA at 202 and it runs great, even at fast speed. It starts to click and jam around 195 if my heater can;t keep up during 60mm/s runs.

[CalifDan]

Thanks. Changing the temperature is something I will try. My concern is that the lower temperature has been working fine from a quality standpoint. I get less stringing and the layers seem to look better, particularly at the joined perimeter spot. Maybe the next question is should the higher temperature also include a speed increase? And if so, how does that reduce the back pressure which I think is the issue. Or, should I be reducing the flow rate?

Like I said, all ideas welcome. I will have three days to mess with it starting on Tuesday, so hope I can figure out a solution that prevents the erosion of the feed bolt and keeps the quality up.

[printbus]

What did you end up using for a slicer? What testing was done to conclude you needed 3mm of retraction?

[CalifDan]

Printbus,

I have used slicer .9 and 1.6. The part I am having trouble with is using .9 version as recommended by Makerfarm. I was using 4mm of retraction, but varied it a bit based thinking that it did not need to go that far. The point of retraction is to eliminate the ooze when moving between print areas (at least that is what I understand). Frankly, mine stops oozing as soon as the retraction starts, so I thought it would save print time to bring it down a bit. I think that you recommended a retraction rate of 10mm/sec and that is what I am using.

Like I said, I think the wearing and ultimate failure of the filament at the feed bolt is because of the back and forth of the retraction process when working on very small areas (frequent retractions). I think I need a way or combination of settings which will allow the retraction or eliminate the need for it and still maintain quality in the print and perimeter areas.

I also have tried tighter and looser on the feed tension idler. I can't yet consistently tell if that is making much difference.

[AbuMaia]

Like I said, I think the wearing and ultimate failure of the filament at the feed bolt is because of the back and forth of the retraction process when working on very small areas (frequent retractions). I think I need a way or combination of settings which will allow the retraction or eliminate the need for it and still maintain quality in the print and perimeter areas. I also have tried tighter and looser on the feed tension idler. I can't yet consistently tell if that is making much difference.

I have heard of others having this same problem. I think it was fixed (or at least mitigated) by easing up on the idler tension, and by increasing retraction distance so you're not running the same small bit of filament over the bolt, but a larger area.

[CalifDan]

AbuMaia,

I will give that a try. Thanks.