hotend temperature jumps!

Hi forum,

I have a problem with my makemendel rapidbot 2.0, hopfuly someone can help me solve it!

Im using it since some years already. but now that i canged to another filament i have problems keeping the hotendtemperature consistend.

At around 202°C the Temperature seems to jump up and down some degrees!

here is the temperature graph at 202°C:
at the set Temperature the reading jumps up and down. Giving me a print temperature from 197C jumping to nearly 208C

anyone has some thoughts about it?

Thanks,
flo

These are the termistortables i use in malin:

#if (THERMISTORHEATER_0 == 6) || (THERMISTORHEATER_1 == 6) || (THERMISTORHEATER_2 == 6) || (THERMISTORBED == 6) // 100k Epcos thermistor
const short temptable_6[][2] PROGMEM = {
{28*OVERSAMPLENR, 250},
{31*OVERSAMPLENR, 245},
{35*OVERSAMPLENR, 240},
{39*OVERSAMPLENR, 235},
{42*OVERSAMPLENR, 230},
{44*OVERSAMPLENR, 225},
{49*OVERSAMPLENR, 220},
{53*OVERSAMPLENR, 215},
{62*OVERSAMPLENR, 210},
{73*OVERSAMPLENR, 205},
{72*OVERSAMPLENR, 200},
{94*OVERSAMPLENR, 190},
{102*OVERSAMPLENR, 185},
{116*OVERSAMPLENR, 170},
{143*OVERSAMPLENR, 160},
{183*OVERSAMPLENR, 150},
{223*OVERSAMPLENR, 140},
{270*OVERSAMPLENR, 130},
{318*OVERSAMPLENR, 120},
{383*OVERSAMPLENR, 110},
{413*OVERSAMPLENR, 105},
{439*OVERSAMPLENR, 100},
{484*OVERSAMPLENR, 95},
{513*OVERSAMPLENR, 90},
{607*OVERSAMPLENR, 80},
{664*OVERSAMPLENR, 70},
{781*OVERSAMPLENR, 60},
{810*OVERSAMPLENR, 55},
{849*OVERSAMPLENR, 50},
{914*OVERSAMPLENR, 45},
{914*OVERSAMPLENR, 40},
{935*OVERSAMPLENR, 35},
{954*OVERSAMPLENR, 30},
{970*OVERSAMPLENR, 25},
{978*OVERSAMPLENR, 22},
{1008*OVERSAMPLENR, 3}
};
#endif

Have you run PID autotune?

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Prusa i3 Rework - Ramps 1.4 - E3d Lite6 - Full Graphic LCD Controller

Loose thermistor?

Broken (or near-broken) wires to the heater or thermistor?

Does this jumping around happen when the head is still? Or only when it is moving?

up

I agree that you need to be looking in the direction of measurement error likely caused by faulty thermistor or wiring.

Hey guys,

Thanks for the help.

Im currently not able to run the PID autotune, because i fried my hotend thermistor. After fixing that i'll update you on how that went.


For the wiring problem. Unfortunately this always happens at the exact same Temperature for the exact same amount of degrees. I tripple checked the wiring already, but with constant resistance of somewhere about 98kOhm i think the thermistor wiring shoul be okay.

Also nothing changes when i bend it or when the printer is running.

Thanks for the support.
I'll let you know how the PID was going after christmas

Happy holidays,
Flo

Hi. Im having the same issue with my prusa I3. Temperature sometime jumps from 330, down to 220 1 1 second and up to 235/240 in the next second!
Wiring is ok, double checked. The only thing it worries me is that is somehow loose inside the hole of the heater block since the hole is bigger than the termistor. So the question would be: what is the best way to solve this loose problem? How can I make the thermistor fit tigher into the hole? Can that thermal grease used for computer processors be used in this situation?

I think your thermistor table has an error in it. The temps and ADC values must be in order. Yours are not in order. ADC 72 and 73 are not in sequence. You also have 914 in twice although 40 degrees is not an area where you are interested.
The temperatures are in order so its not a case of changing the order of the rows there is an error in the ADC value verses the temperature. Not sure if 72 should be 82.
You should be able to look up a correct table on the web.
Tinchus - I suggest you have a look at yours as well.
I have the same symptoms on my tables but its not in my operating area for ABS so I can live with it.

Seems like erroneous tables are growing phenomena.