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I'm using the Beta value of 4267 as recommended by E3D on my Duet running RRF. My problem is that when I've got my target temp set (and reading) 245C, thermocouple readings at the nozzle never go past about 205.

Since I don't have a 1%, 100k resistor handy, can someone let me know what the proper Beta value is supposed to be for the E3D Volcano?

tnx!

g.

You really need two resistors (if you ohm out the thermistor at your room temperature it can be one) to set the ADC compensation values.

Although the nominal B value for the thermistor supplied by E3D is 4267, if you look at the datasheet then for temperatures around 220C a more accurate value is 4388. It makes around 7C difference AFAIR.

It's quite difficult to get good thermal contact between a thermocouple and the heater block, so the thermocouple is likely to under-read. Some people suggest feeding the thermocouple into the hot end in place of filament for a more accurate reading.

I've been running it at 260C and it appears to print ok. I've got a funky layer offset issue at the moment...

g.

Every E3D I own has been off by 20 degrees reading high at 220+ compared to a thermocouple, they use the data sheets nominal Beta value, but that's designed to have it read accurately at room temperature, not towards the edges of it's range.
I just fiddle with mine to match the thermocouple, I can't remember what it's currently set to, but it works across all their supplied thermistors (of which I probably have 5), so it's not a manufacturing variance issue.
The odds are the thermocouple is reading low because it's difficult to get good contact, mine won't fit down the barrel of the hotend, so I use the interface between the nozzle and the heater block as the point I measure.

At some level it not reading accurately doesn't really matter except when exchanging settings with other people, I just tune to the thermocouple because I know relative to that tuning what temperatures to use for various plastics and I tend to swap hotends regularly.

I'm using the same sampling location you are.

My issue right now is that BOTH of my Duet based machines have now decided to do a diagonally offset layer shift.
Blue MAX does it after getting roughly 1/3rd in to the model - it's a weird one. Red Sonja did it on a pair of Vive controller hangers about 10% up. No clue as to why. I'll start a new thread on it...

g.