PT1000 high-temp question  

Update

Just to check that there isn't something else happening that I'm missing, I re-sliced the file and changed the temp to 298C. This time it behaved as expected, printing beautifully until it warped off the bed and I had to cancel the print. In these images, the top pieces were printed at 300C and the bottom at 298C (though, clearly the 300C print was far higher at the end... basically producing a smooth pool of melted plastic on the topmost surfaces).

These were printed about an hour apart using the same spool, same PrusaSlicer settings, everything the same except the temperature.

Hi Rusty. 
standard Mk3 series printers do not use PT100 sensors. 
Are you sure you have a PT100? these normally need an amplifier/interface board to work with the Mk3, and I believe they require modified firmware!

As far as I understand 300C is the limit for a Semitec 104 gt-2 thermistor, which is usually used on a prusa mk3 printer. 

I believe Slice engineering offer a high temperature thermistor, to replace the standard Prusa thermistor, and to the best of my knowledge, this also needs revised firmware. 

regards Joan

Thank you! To clarify, it is a PT1000, not a PT100. It does not require an amplifier but it does require modifications to the firmware. What I'm asking is whether anyone else has encountered similar issues when making this switch. I believe I updated what was needed in the firmware correctly but due to this odd 300C behavior I'm guessing I missed something Prusa-specific.

More background I should have included: I've just upgraded from the stock V6 setup to a Slice Mosquito hotend using the Slice 50W heater and the Slice PT1000. They did not have the high-temperature thermistor in stock and the PT1000 is supposed to work with just some minor firmware updates as described in my first post. Here is Slice's documentation on updating the firmware:

https://support.sliceengineering.com/portal/en/kb/articles/how-do-i-update-my-firmware-to-be-compatible-with-the-rtd-pt1000

does your thermistor table have entries for temperatures above 300C (Appropriate for the PT1000)

regards Joan

Ah - thanks, you may be right. Here are the relevant sections from thermistortables.h in the 3.10.0 firmware. It does look like it stops at 300. I'll add a 350 row and see if that solves it. For anyone else reading this at a later date, a separate file called Configuration_adv.h defines "thermistorheater_0" as "temp_sensor_0". So the change in the Configuration.h file to modify temp_sensor_0 from 5 to 1047 changes the relevant lookup table in thermistortables.h from 5 to 1047.

// Pt1000 and Pt100 handling

//

// Rt=R0*(1+a*T+b*T*T) [for T>0]// a=3.9083E-3, b=-5.775E-7

#define PtA 3.9083E-3

#define PtB -5.775E-7

#define PtC -4.183E-12

#define PtRt(T,R0) ((R0)*(1.0+(PtA)*(T)+(PtB)*(T)*(T)))

#define PtRtNew(T,R0) ((R0)*(1.0+(PtA)*(T)+(PtB)*(T)*(T) + (T-100)*PtC*(T)*(T)*(T)))

#define PtAdVal(T,R0,Rup) (short)(1024/(Rup/PtRt(T,R0)+1))

#define PtLine(T,R0,Rup) { PtAdVal(T,R0,Rup)*OVERSAMPLENR, T },

#if (THERMISTORHEATER_0 == 1047) || (THERMISTORHEATER_1 == 1047) || (THERMISTORHEATER_2 == 1047) || (THERMISTORBED == 1047) // Pt1000 with 4k7 pullup

const short temptable_1047[][2] PROGMEM = {

// only few values are needed as the curve is very flat

PtLine(0,1000,4700)

PtLine(50,1000,4700)

PtLine(100,1000,4700)

PtLine(150,1000,4700)

PtLine(200,1000,4700)

PtLine(250,1000,4700)

PtLine(300,1000,4700)

};

#endif

Has that worked for you?

regards Joan

It appears to have worked, though I haven't printed anything yet. I just set the nozzle temp to 305, then 310 yesterday and each time it stabilized and read temperatures greater than 300 with some +/- fluctuations as I'd expect. I will have time to actually print again this weekend. Thank you for your help with this!

RE: PT1000 high-temp question

Rusty, I would be willing to pay you for your help and knowledge on helping me alter the firmware for my Caribou 320 (Prusa clone company). I cannot get an SE high temp thermistor either, and need this machine to run ASAP. Any help would be greatly appreciated.

Thank you for your time and this article. I got a little ways but I cannot get the firmware to validate without error.

RE: PT1000 high-temp question

Sorry Seldon, I'm probably the last person you want helping you with this. I fumbled around with the Arduino software a few times until I got my printer working, but I am by no means an expert or even proficient. I would start with the following link. It was extremely helpful the few times I had to update my firmware for the Bear frame upgrade, E3D Volcano, and then Mosquito.

https://github.com/prusa3d/Prusa-Firmware

RE:

Really interesting.  With E3d launching their high temp REVO models, I’m looking to do something like this- and probably a lot of other people will too. Thanks

Did you do anything to the bed to get it to go hotter?  Will the standard sheets from Prusa survive 350 or 400C materials?

RE: PT1000 high-temp question

Sorry if I am performing a bit of necromancy here but although I believe the Arduino toolchain is now deprecated you could follow some of the steps in this article by Slice Engineering.

Updating my Prusa firmware for the Slice Engineering RTD Pt1000