Replicator 2x "air printing" stops extruding after 20 - 40 min

[Alvin Gozali]

The replicator 2x in my university stops extruding after about 20 - 40 minutes constantly. The printer is quite old.

I am printing ABS (makerbot brand) at 230c with the heatbed at 110c (kapton) with the door and top cover closed.

I have tried changing the nozzle, printing at 240c and 250c, slowing print speed to 20mm/s, nothing seemed to work.

The machine is not modified in any way (stock firmware, and lever arm extruder)

The machine runs again after i unload and loads the filament again, and I noticed that the drive gear have chewed up the filament.

The whole machine also seemed to be very hot, the extruder motor is so hot i can't touch it. The aluminium bar is also hot to the touch. (metal frame was very warm)

What is wrong with the machine? Is there any way to fix this? Thanks.

[adam paul]

Is the fan blowing into the heatsink operating?

[Rich Webb]

Classic cold end jam. The filament melt zone is creeping up from the hot block into the cooling bar towards the extruder gear assembly. At some point you're transitioning from pushing a cold, stiff piece of ABS into trying to push a softened noodle of plastic that is jamming against the wall of the extruder tube.

As Adam mentions, one contributor to this is inadequate air flow from the fan blowing over the heat sink. The air should be blowing onto the heatsink (label side faces the heatsink fins) and the fins should be mostly clean of dust/cat hair/etc. The fan/heat sink assembly should be tight against the cooling bar.

Also, since this has been happening have you cleaned the ridges on the feed gear? If it's grinding into the filament then the gear teeth may be filled with plastic, making it less effective and less able to push filament into the hot end.

Printing hotter and slower just exacerbates the problem. One of the things which helps to keep the melt zone down where it belongs is the entry of cold (relatively) filament from above. When you print really slowly there's more time for the heat to creep up from the melt pool into the the feed tube thermal barrier.

[Jetguy]

Also, of note, there are a few known fault modes on the 2x series.

#1 is that even the slightest overload on the extruder cooling fan can blow the MOSFET on the mainboard. Something as simple as the fan getting stopped one time while spinning or a bearing that needs some oil and the fan draws more power and the MOSFET controlling it fails. When that MOSFET fails, it's generally stuck in the on state, meaning that if you turn on the machine from a cold start (extruder is at room temp) the fan turns on the instant power turns on. The fan should be thermally controlled only turning on when the extruder is above 50C. But also, the "stuck on" state is not 100% on and degrade with further usage making the fan spin  slower and slower and have this type of fail.

#2 is, I know for a fact the many users of the 2X experienced wear and failure of the Filament feeder section that grips the filament. The lever arm system could warp, crack, or just generally wear out. The spring was also subject to some question due to coil collapse. You mentioned grinding and that is a clear failure of the feeder section. The first troubleshooting extrusion failure rule is before you ever try to print, run the load filament script on the LCD, and when it tries to feed the filament, take your fingers and grip the cold filament above the extruder going into it prevent it from going in while the motor is pulling. The motor MUST skips steps in this state and never grind the filament. Grip must be stronger than the motor. If you fail this test, your feeder setup has failed or is worn and needs upgraded or replaced.

[Alvin Gozali]

Both fans are working normally, turns on at 52c and is pointing at the heatsink. I have cleaned the drive gear of any filament and it still stopped extruding mid print.

The extruder stepper skips steps when i grip the filament, so that's not an issue. (but the left extruder has a cracked arm piece tho, right extruder is fine) What would you recomend for the extruder upgrade?

So both fans are oriented at the right way, is spinning, heatsink is clean, and the cooling bar is still hot.

[Gian Pablo]

Try printing faster at lower resolution, and with the top hood off. If that works then likely is a cold end jam as Ryan describes. It is also possible that the fan may be running slower due to a failed MOSFET.

[DHeadrick]

I hope you have fixed your problem.  If you haven't though, the heat at which you are printing may be wreaking havoc with the stock feeder.  You mention that the drive gear chews up the filament which is a sign that the feeder mechanism is not up to the task required of it.  Many 2X owners have upgraded to the 3in1 Extruder feeder with much success (271 owners to be exact).

http://www.devilsinthedetails.ca/locations.phtml

It might be something you would be interested in so that you can regain full use of your printer again.

Dave