Welcome to the SeeMeCNC Community

I have attached a picture of the temperature profile of my hotend. It seems to be quite jumpy. I am not moving the hotend around and the thermoresistor is properly seated. If I continue to heat the hot end while this is happening it starts smoking like crazy and it never settles at the desired temp. I have replaced the thermoresistor and that did not seem to help.

Any suggestions on how to fix this issue Ia m having,

I would be suspicious of bad heating resistors or bad connection shorting somewhere.
Is it a stock hotend

i think the -20 value is a sign of a short....

the -20 is because I disconnect the hotend to recheck the wires. It is a e3d hot end.

so0o0ooo...it reaches temp then jumps around? maybe a PID issue... have you tried re calibrating your coefficients?

Do you have a spare heater cartridge to try? Bubba is right too, did you you re-tune PID after the thermistor change? As I understand it, you can't reach operating temp without smoke correct? This "jumpiness" happens as soon as you turn on the hotend?

Did you just transition from a stock hot-end to the E3D one? If so, you need to change which thermistor table is used in the firmware. The default for the SeeMeCnc hot-end (I got my in August) was 97. The line in configuration.h looks like this:

#define EXT0_TEMPSENSOR_TYPE 97

You'll need to change it to "1" instead of "97".

I have been using the e3d for months now with no issues. The problem start does not correspond with any mod/changes I made to the printer. The current setup has been previously tuned and calibrated.

I have not switched out the heater. It just seems like the issue was with the therimocouple and not the heater. The instability in the temp seems more pronounced during actual printing.

Absolutely stinks of a loose wire!

Keep the printer stationary, and go along all your wires flexing and shaking them. Connectors too. You'll find one area or connector that causes the sudden temp reading change. There's your break!

Let me know how you get on. If you're still having issues make a support ticket with us on our site under contact us and I'll try and help you out.

Cheers,
Sanjay

From the log message in your picture, it looks clear that it is a loose connection on your nozzle thermister. It says the temperature had a reading of 0, which is the reading you get when you have no thermister attached. When the firmware catches a 0 reading at any time, even if it is for a split second, safety mechanisms kick in and put you into dry (no heat/extrusion) mode.

Take a look at the connection plug near your nozzle on your thermister wires and double check that both metal prongs do indeed make a solid/stable connection with eachother. Most often what happens is that one of the metal prongs that are supposed to be snapped into the plug piece is no longer locked in place and can be easily pulled right out.

I know this is old, however, update?

I posted a thread about how to make vibration-resistant crimps. If it's suddenly going sideways and you haven't changed anything, that's where I'd look.

I'd also consider using an external temperature probe (the kind that looks like a multimeter) to verify that the temperature is close to what the thermistor is reporting. They do fail sometimes (especially the crappy Honeywell one they ship with the Budaschnozzle) and when this happens you'll see the temperature curve dipping to zero for short periods of time. However, the temp curve in the screenshot DOES NOT look like that!