Hot end suddenly shuts off mid-print?

I have a printer that has been running reliably for a really long time. Haven't changed anything, but suddenly started getting a lot of stripping problems in the middle of a print. Today I checked the temperature graph and was shocked to see that the extruder temperature suddenly goes downhill mid-print! Any ideas what to check? I already ran through the Gcode and found nothing strange (no strange extruder temperature commands).

My machine is a Mendel Max variant using a Sanguinololu board/motor drivers, running Marlin. I'm using Repetier as my front end and Slic3r as the slicing engine. All driven on USB from a PC (no SD card or anything).

I had the same problem, that even the temperature drops so low that it stops extruding but keeps on moving, because of prevention of cold extrusion.

My problem was that the thermistor inside the nozzle was loose and was measuring temperature in mid air. This has a much lower temperature then when the thermistor is stuck against the metal of the nozzle.

I will check my machine, but I doubt that's the cause. I am using a Lulzbot Budaschnozzle so the thermistor and resistor were both pre-assembled and I haven't seen any movement of either part. Also, if the thermistor was reading low, wouldn't that tell the PID loop to increase the power to bring the temp back up to the setpoint?

Like I said, I will check but I don't think that's my problem. Thanks for the suggestion!

-CH

Kirschner3D Wrote:
-------------------------------------------------------
> I had the same problem, that even the temperature
> drops so low that it stops extruding but keeps on
> moving, because of prevention of cold extrusion.
>
> My problem was that the thermistor inside the
> nozzle was loose and was measuring temperature in
> mid air. This has a much lower temperature then
> when the thermistor is stuck against the metal of
> the nozzle.

Don't know if Repetier is the problem, but when we used RepetierHost it did things we didn't want it to do.
Maybe try Pronterface and see if this changes anything for you.

Repetier shouldn't be the problem. I have been using it very reliably for a year, and have not done any updates in the last month or so (the printing trouble doesn't coincide with an update).

Right now I'm suspecting a simple bad connection somewhere in the wiring, but I've been to busy to check it. Probably in the next couple of days I'll get to it.

What kind of things was Repetier doing that you didn't want it to do?

Definitely a connection issue! Ran a print, paused when the temperature started to drop, then flexed my main cable to the hot end in a few places. Power came back on! Now I just need to figure out exactly where the break is so I can stop it from happening again. Not sure if it was my solder joint (going to guess not likely) or if it was fatigue of the resistor wire (going to guess this was it, since Lulzbot used solid core wire). Will post again once I know for sure!

Good to know you almost found the cause of the problem

I have read that solder melts between 180-190 degrees.
[en.wikipedia.org]

So i don;t know if you did it yourself or bought it already set up.

Definitely fatigue in the solid core wire! Just look at the pic and you can see "one of these things is not like the other". E-mailed Lulzbot and they said it "rarely happens", although there is a service bulletin about not zip tying wire to the Z-carriage on their machine. I built mine from scratch and did not apply any zip ties. The wire fatigued right inside the wooden guide. It doesn't deflect far in there, but fatigue eventually will kill most things!

I just had this same problem, with my printrbot though. BUT I am also using the BUDDASCHNOZZLE from Lulzbot.

The temp dropped down the a reading of 165 degrees C, so it said it was too cold to extrude.

What did you end up doing?

Swapping out wires?

I hope to hear from you soon!

Thanks

Sorry it took me so long to reply! I ended up just cutting the ba wire below the flex and soldering in some new wire. Then I carefully took stock of where the flex happens and zip tied the wires to my motor (it does not get hot at all). Hopefully I won't have the same problem again, but if I do I will pull the connectors off the resistor an thermistor and replace all the solid core wires with stranded ones. Probably what I should have done in the first place but it was late at night and I was being lazy.

Thanks man! I will try some new wires and see if this works!

i had a similar issue but it wasn't just the hot end it was the bed and all the motors. I figured out that it was the PTC fuses on the ramps board overheating ... Not due to excessive current though. Just put a fan on the ramps board and everything sorted out.