Hi vitalsparks,
Have been reading your interesting post and did the same test as you did when reading the temperature inside the nozzle using chromel alumel thermo couple. I did this because it was convenient, as I did a check of the hot end after some 2o hour printing with nylon first time at 256 deg. Celsius.
Here is the result from my setup:
Set Temp. UM2 Nozzle Temp. UM2 Measured temp ext. instrument.
deg. C deg. C deg. C
30 30 31
50 49 50
100 100 100
150 150 151
200 200 200
230 231 231
250 249 249
255 254 254
I was kind of surprised after this good/excellent result, however, this is actually confirming my experience with those sensors. The Platinum PT100 is used "mostly" in the aviation as an absolute temperature reference among a few others.
Here is some pictures of my setup and most important values:
The hot end with the thermo couple inserted into nozzle tip.
The adjusted temp is 100 deg. Celsius.
The adjusted temp is 200 deg. Celsius.
The adjusted temp is 230 deg. Celsius.
The adjusted temp is 250 deg. Celsius.
The adjusted temp is 255 deg. Celsius.
Why this difference?
When I built my printer, I was using copper paste in between the heat shell and the heat block. I've also used copper paste between the PT100 shell and the heat block.
As there's a little space (for expansion) between the mounting hole's for the heat shell and the PT100 temp sensor it is a good practice to fill up the space (clearance) with copper pasta.
Copper pasta have excellent properties for this use as:
Good thermal conductivity (air pocket is a very poor heat conductor).
Good electrical conductivity
Corrosion resistance
Copper paste also prevent corrosion and burning of parts, but you still will need to preheat the nozzle for change or removing hot end from the attachment frame.
IF YOU ARE GOING TO USE COPPER PASTE FOR THE FIRST TIME, DO NOT INSTALL THE TWO COOLING FAN SHROUD. WHEN YOU HEAT UP THE NOZZLE FIRST TIME AFTER THIS TREATMENT, THERE WILL BE A LITTLE SMOKE (SO MAKE SURE YOU HAVE VENTED AREA), ALSO THERE MIGHT BE A LITTLE DRIPPING OF EXCESS COPPER PASTE, SO HAVE A COTTON RAG OR PAPER TOWEL FOR KITCHEN USE, WHENREADY TO CLEAN OF THIS EXCESS SPILL.
Metal device: Relative Conduction:
Copper 394
Silver 418
Aluminum 238 (The cold junction frame attachment and cooling frame)
Stainless steel 13 (The nut holding the heat block and housing the TFM coupler).
PS. I'm also using copper paste in between the nozzle tread and in between the steel nut tread mounted onto top of heat block. NB; Be careful here to avoid copper paste into the filament area/side.. Note Well..
Just for the record; I'm still using a 24 W heat element, even printing with nylon at 256 deg. C!
This is just because my setup is far more efficient, due to much better heat conduction!
(To check the calibration of the PT100 sensor, put the sensor into clean water with ice cubes that's need to be stirred to keep this mixture at zero deg. Celsius. Your Ultimaker nozzle temp should read 0 deg, C. (A precision resistor with 100 Ohm should read zero deg. C as well. 0.5% tolerance or better is needed).
Do the same with boiling water, will show 100 deg. C here.. )
Maybe this little modification might be something for you, unless you have something else in error.
Thanks
Regards
Torgeir
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vitalsparks 8
That's what my measurements showed, but it is reassuring for me to know exactly what that temperature is, especially when I occasionally change to a different material like T-Glase or PolyFlex. With ABS, and various other materials, carbonation turns the material into a hard crust that lines the inside surface of the hot-end and, when eventually minute particles break away, this is what can clog the nozzle. In my experience, an early warning sign is the slipping of the feed motor as the carbon builds up, increasing the pressure required to force the filament through the hot-end - due to increased friction against the walls I would guess.
With my favourite ABS (ABS-X from 3DFilaprint) I set the temperature to 235deg (actual 255deg) and a bed temperature of 80deg. I get excellent layer adhesion, and no evidence of warping (an attribute of ABS-X). I rarely turn on the fan, except when printing very small objects.
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