Solved Extruder Thermistor Fail (née: Heated Bed Failure)

I got the silicon boot off, but still looks like the thermistor is buried under a bunch of plastic. Off to tech support to see if they can get me working again.

 

Looks like your hot end was leaking filament out the top. That's crazy how perfectly it formed

Its possible to heat it up enough to remove the plastic but that's difficult to do safely without a working thermistor. I'd just request a new replacement hot end

 

Thanks Mike. That was my take too.

I really appreciate your patience walking me thru the troubleshooting.

 

Sure no problem. This stuff comes naturally to me and I just want to see people happily enjoying their printers

 

Tech Support acknowledged the issue, and says they're sending a new hex assembly. When they get those parts in.

In the meantime, I decided to try to pull the assembly apart and see if I can get after what happened and learn a bit (and maybe recover this one for a spare.)

I dunked the block in boiling water, which softened up the plastic enough to bet it off the exterior.

I disassembled the heat sink, block, and nozzle. The extruder thermistor is still reading 410 kiloohms, same as before.

Here's the top of the heat block; you can see where the melted blue material was coming up around the threads of the heat sink



On the bottom, the nozzle came out cleanly, but you can see that the threads are really mangled. I think the thread tapping (or nozzle installation) wasn't done correctly.



When the thermistor failed, the nozzle cooled and blocked the PLA, but the extruder kept pushing filament in and it was hot enough to come up around the heat sink threads.

----------------

I watched this video about assembling hexagon hot ends, and it looks like roughly the same model I have



However, the thermistor seems VERY tight in the block. If I was to try to pull it out, I think I'd break the wires and leave the glass bead behind. If I wanted to replace the thermistor in this block, any suggestions? Can I just rip it out and re-drill the hole where it was? Is that worth the trouble?

 

Thanks to tech support, I got a new hex hot end and am in business again tonight.

Here's my first print: a PLA oiler




thanks all for the assists!

 

PS: new thermistor read about 100 kiloohm resistance out of the box, as it was supposed to. Once I put it back together with the new hot end, all was well.

 

I am having this same issue, I left a large print (5+ hrs) alone. when I came back the filament had clogged up and started coming out the top of the hot end.
I've got it mostly cleaned up and it will start printing but it won't keep up the extruder temperature for more than a couple minutes before falling.

 

I did pull the boot off while cleaning (That's as technical as I got) dis-connected and re-connected the thermistor cables, and gotten the boot back on with the thermistor inside touching the hot end.
What does "sanity check" mean, as well, where is the heater core and how do I check that?

*Edit - I'm guessing the heater core is powered by the real thickly red-insulated wires coming off the extruder. I dis-connected and re-connected those and I'm trying another test print.

*Edit - Ok, test print made it about 5-10 minutes, which is an improvement, then the extruder temperature fell and it stopped.

 

Nothing I have been able to see has looked broken, and all the connections are solid. The thermistor still has a bit of plastic stuck to it from the overflow of PLA but that is minimal.
To be sure, the thermistor is the small glass bead-deal slid into the side of the boot, like so?

 

Is the communications log the GCode Terminal under Configuration? If so I sent M999 to it (from the first page of this thread) and this is what I got:
<-okstart
<-echo: External Reset
<-Marlin1.0.0
<-echo: Last Updated: Oct 11 2014 15:33:46 | Author: (RoBo 3D, R1 Single Extruder)
<-Compiled: Oct 11 2014
<-echo: Free Memory: 3757 PlannerBufferBytes: 1232
<-echo:Hardcoded Default Settings Loaded
<-echo:Steps per unit:
<-echo: M92 X80.00 Y80.00 Z2267.72 E723.38
<-echo:Maximum feedrates (mm/s):
->M105

<-echo: M203 X500.00 Y500.00 Z5.00 E25.00
<-echo:Maximum Acceleration (mm/s2):
<-echo: M201 X9000 Y9000 Z100 E10000
<-echo:Acceleration: S=acceleration, T=retract acceleration
<-echo: M204 S1300.00 T3000.00
<-echo:Advanced variables: S=Min feedrate (mm/s), T=Min travel feedrate (mm/s), B=minimum segment time (ms), X=maximum XY jerk (mm/s), Z=maximum Z jerk (mm/s), E=maximum E jerk (mm/s)
<-echo: M205 S0.00 T0.00 B20000 X17.00 Z0.40 E5.00
<-echo:Home offset (mm):
<-echo: M206 X0.00 Y0.00 Z0.00
<-echoID settings:
<-echo: M301 P22.20 I1.08 D114.00
<-echo:SD card ok
<-ok T:0.0 /0.0 B:0.0 /0.0 T0:0.0 /0.0 @:0 B@:0
->M115

<-FIRMWARE_NAME:Marlin V1; Sprinter/grbl mashup for gen6 FIRMWARE_URL:https://github.com/ErikZalm/Marlin/ PROTOCOL_VERSION:1.0 MACHINE_TYPE:ROBO3DR1V2 EXTRUDER_COUNT:1 UUID:00000000-0000-0000-0000-000000000000
<-ok
->M105

<-ok T:28.6 /0.0 B:28.6 /0.0 T0:28.6 /0.0 @:0 B@:0
->M105

<-ok T:28.6 /0.0 B:28.6 /0.0 T0:28.6 /0.0 @:0 B@:0
->M105

<-ok T:28.6 /0.0 B:28.6 /0.0 T0:28.6 /0.0 @:0 B@:0
->M105

...Repeat above two lines over and over.


*Edit - Starting another test print and watching the terminal

 

Alright, test print did the same thing. I'm not seeing any errors in the terminal but at about 4 minutes it said it was done:
<-ok [0.000]

->M23 gimbal~1.gco [0.000]

<-echo:Now fresh file: gimbal~1.gco [0.000]

<-File opened: gimbal~1.gco Size: 1039099 [0.000]

<-File selected [0.000]

<-ok [0.000]

->M24 [0.000]

<-ok [0.000]

<-echo:Active Extruder: 0 [0.000]

->M105 [0.000]

<-T:196.3 E:0 W:? [0.000]

<-T:196.2 E:0 W:? [0.000]

<-T:196.1 E:0 W:? [0.000]

<-T:196.2 E:0 W:? [0.000]

<-T:196.3 E:0 W:? [0.000]


..... more of this


<-SD printing byte 968450/1039099 [0.000]

<-ok [0.000]

->M105 [0.000]

<-ok T:156.8 /0.0 B:47.4 /0.0 T0:156.8 /0.0 @:0 B@:0 [0.000]

->M27 [0.000]

<-SD printing byte 1009282/1039099 [0.000]

<-ok [0.000]

<-Done printing file [0.000]

<-echo:0 hours 4 minutes
<-echo:enqueing "M84 X Y Z E"
->M84


...oh, found it!

<-ok T:200.1 /210.0 B:49.7 /50.0 T0:200.1 /210.0 @:127 B@:127 [0.000]

->M27 [0.000]

<-Error:Extruder switched off. Temperature fell too much during print! [0.000]

<-Errorrinter stopped due to errors. Fix the error and use M999 to restart. (Temperature is reset. Set it after restarting) [0.000]

<-SD printing byte 108972/1039099 [0.000]

<-ok [0.000]

 

Temp fall error. Probably a loose thermistor in the hole or a loose connection somewhere

 

Ah, and how do I go about checking that, more so than dis-connecting them and reconnecting them at the slots by the hot end?

And it looks like I have a firmware update, doing that now.

 

I would hit Robo for a new Hex head unit complete with thermistor and heater if it is still in guarantee. If not Printed Solid and Amazon have whole kits. The original Hex heads furnished by Robo do Have a tendency to leak. I know, I went down that road. Frank