Failed prints

OK, so I’m having trouble re-printing a part. I printed this part a few weeks ago, and it was by far the best large print that I’ve done. Since then, I’ve tried 5 or 6 times, and it’s always failed as it makes the transition from the large horizontal bottom to the vertical sides. The failure that I see is that the filament stops feeding. The hobbed bolt then grinds away the filament, and nothing else is extruded until I cut off the filament and re-feed.

When I correct the problem, I pull the filament out, cut off the last couple of inches, then push it back into the extruder by hand. I’ve never seen any blockages in the nozzle, so I’m not sure what’s causing the problem. I’ve taken a picture of the part, and attached the stl file and gcode. Anybody have any thoughts on what else I can try?
HVAC Cover.gcode (1.52 MB)
HVAC Cover.stl (61 KB)

PLA? If so, try pointing a small fan at the printer. If that corrects the problem, you probably have a faulty hot end cooling fan. I have had massive problems with those small stock fans.

I suspect the print fails when you move to the side walls because the amount of plastic extruded in a given time is reduced allowing more heat to creep up the filament and cause a jam.

Yes, Push Plastic brand PLA, in red.

That’s about what my guess was as well, so I’ve been moving to faster print speeds and thicker layer heights to try to combat the problem. What do you mean by a small fan? I’ve got some 40mm fans sitting around, or some 4" desk fans (I’m guessing that the 20" floor fans would be too much?)

Try tightening the idler. A few turns on each screw.

The four inch desk fan should do it. You just want a gentle breeze.

If they are loose, this will help. If it is a heat creep problem, it will still strip. :angry: Those small hot end fans are junk in my opinion.

Well, it looks like the desk fan solved the problem. My cover managed to print this weekend, so I’ve fired up another print this morning. Time lapse of the print is at:

I am glad you found the problem.

Those small squirrel cage fans are pure crap in my experience. I have switched to 40 mm 12 volt fans for the Hexagon hotends I am still running. I power them directly from a wall wart. I tried using a 5 volt 40 mm fan but it didn’t produce enough flow and the heat creep persisted.

I have this fan on two hexagon hotends and one e3d hotend. Ive never had an issue.

You are lucky.

Well, it looks like my resolution was premature. It worked well for a couple of weeks, then started failing nearly every print. So, over the weekend I printed a new shroud, and installed a new fan Monday morning.

Alas, even with the new fan and shroud, I’m still running into problems with prints failing. I’m most definitely seeing the swelling of the PLA, and the filament being “stuck” when I try to pull it out after a jam. I’ve got 20kg of PLA here that I’d like to use up, or I might just switch to ABS. I’ve spent a few hours reading all of the various threads here about this issue. The best of them seemed to be but even that one got a little confusing after a while, and I’m not sure what their final conclusion was.

Does PLA expand more with temperature changes if it has absorbed water? I’m really out of ideas for things to try next.