500C thermistor table now in Marlin

[gr...@gregtan.com]

Hi Pico users,

I thought I'd tell you that I submitted a pull request for the Marlin formware (https://github.com/ErikZalm/Marlin/pull/955) adding the 500C thermistor table has just been merged. It is thermistor number 70 in the Marlin firmware.

Greg

[alex...@gmail.com]

Hi Greg,

How did you build this table?? Using a thermocouple??

Cheers.

Alex.

[gr...@gregtan.com]

Hi Alex,

Nothing so advanced I'm afraid. I just used B3's supplied thermistor table and put it int he Marlin codebase.

It was just a cenvenience so others wouldn't have to modify their firmware to support the Pico.

Greg

[alex...@gmail.com]

That's great Greg,

I just received my Pico. As soon as I get it working, I'm gonna build a table based on thermocouple and merge it into marlin official branch.

Cheers.

Alex.

[B3]

This is great guys... Thank you for your contributions! We will update literature to make installation even easier! - Will

[cfe...@ualberta.ca]

Thanks, I just replaced the thermistortables.h file and defined the temp as 70. Hope that works.

[pneil...@gmail.com]

I just grabbed the tables. This is the first time I have looked at thermistor tables. Out of curiosity, the table only appears to go up to 350 (which I assume is 350 degrees C ?). Is that a bad assumption? If its correct, then how does it behave when going up towards 500 degrees C? Thanks

[cfe...@ualberta.ca]

I noticed and am curious about this as well. Does the software linearly extrapolate beyond this?

[B3]

All,

The firmware does extrapolate beyond 350C, but if its linear, I am not sure. That's a good question for the firmware developers. If anyone is up to creating a temp table before we do, beyond our 350C for solid data, let us know. We would like to provide a reward for the people who help contribute.

Thanks,

Mike

The B3 Team

[alex...@gmail.com]

Well, a reward always motivates me ;-)

Just kidding..

Bellow you have the 500C thermistor table calibrated with a Fluke Thermocouple.
I build the table up to "only" 400C; that is the safe limit of my thermocouple probe. Actually I don't know any filament demanding more than 400C.

I will integrate this table in Marlin official branch soon.

Cheers.

Alex.

#if (THERMISTORHEATER_0 == 70) || (THERMISTORHEATER_1 == 70) || (THERMISTORHEATER_2 == 70) || (THERMISTORBED == 70) // 500C thermistor for Pico hot end
const short temptable_70[][2] PROGMEM = {
{ 1*OVERSAMPLENR , 500 },
{ 49*OVERSAMPLENR , 400 }, //Thermocouple calibrated
{ 59*OVERSAMPLENR , 384 }, //Thermocouple calibrated
{ 74*OVERSAMPLENR , 367 }, //Thermocouple calibrated
{ 88*OVERSAMPLENR , 353 }, //Thermocouple calibrated
{ 103*OVERSAMPLENR , 342 }, //Thermocouple calibrated
{ 126*OVERSAMPLENR , 327 }, //Thermocouple calibrated
{ 164*OVERSAMPLENR , 308 }, //Thermocouple calibrated
{ 215*OVERSAMPLENR , 288 }, //Thermocouple calibrated
{ 279*OVERSAMPLENR , 269 }, //Thermocouple calibrated
{ 360*OVERSAMPLENR , 250 }, //Thermocouple calibrated
{ 459*OVERSAMPLENR , 230 }, //Thermocouple calibrated
{ 512*OVERSAMPLENR , 220 }, //Thermocouple calibrated
{ 568*OVERSAMPLENR , 210 }, //Thermocouple calibrated
{ 623*OVERSAMPLENR , 201 }, //Thermocouple calibrated
{ 678*OVERSAMPLENR , 192 }, //Thermocouple calibrated
{ 732*OVERSAMPLENR , 182 }, //Thermocouple calibrated
{ 781*OVERSAMPLENR , 172 }, //Thermocouple calibrated
{ 928*OVERSAMPLENR , 134 }, //Thermocouple calibrated
{ 995*OVERSAMPLENR , 97 }, //Thermocouple calibrated
{ 1019*OVERSAMPLENR , 51 }, //Thermocouple calibrated
{ 1023*OVERSAMPLENR , 25 },
};
#endif

[Kris T]

I've looked in the Marlin config and thermistortables and I'm not seeing any #70 option ? In addition to v1, I've checked all the other branches on Github.

https://github.com/ErikZalm/Marlin/blob/Marlin_v1/Marlin/thermistortables.h

https://github.com/ErikZalm/Marlin/blob/Marlin_v1/Marlin/Configuration.h

Is there a more up-to-date version of Marlin ? I'm having other issues with setting up ~4 extruders that makes me think v1 is a bit outdated.

[B3]

Kris, it seems #70 has been removed. If you go to the 'Thermistortables_H' tab in Arduino you can over write any table you don't need with the following data: 500°C Temp Table ver 1.1 

Let us know if you need more assistance! Good luck — Will

[Kris T]

I'm noticing the table is pretty sparsely populated at the higher temperatures and doesn't go above 350C; does this mean that the thermistor is not a good choice for measuring/maintaining temps nearer to 400C ? Are there other limitations with the Pico extruder that will prevent me from printing near those temps (like with Ultem, PPSU/PPSF, PEEK, etc) ?

[B3]

Kris,

The 500C thermistor is still a great choice for going up to temps of 500C. The curve from the table gets extrapolated for readings above 350C. Infact, we have been testing with FEP filament at 375C and it is extruding well (its not sticking to the bed as we need a better surface, but its extruding). We are working on getting a more complete table near the high end but for now it works great.

The 500C Pico is very capable and will not prevent you from reaching high temperatures, all though we do not recommend constantly printing at 500C but only reaching 500C in short periods of time. We have not tried printing the filaments you listed other than FEP, but we encourage safely experimenting with other filaments such as those and if possible, sharing the results with everyone.

Let us know if you have any questions,

[Jay]

Do you have a recommended source for FEP filament?

Thanks,

Jay

[B3]

http://www.plastic2print.com/eu/ is where we got our spool a few months back