E3D Cartridge Reads Thermistor Lower Than Stated Temp



  • Hey Guys,

    Title pretty much says it all. I have to set the temp to 250+ to get it to extrude 50mm of filament and when I try to run it again right after it stops feeding after a few mm, presumably once the already melted pla has been extruded. My initial readings with an IR temp gun read around 190ish when its set to 250. I know IR temp guns aren't great, but all things considered, its still a strong indicator something is amis. I can find my thermocouple for my multimeter to get a more accurate reading if need be.

    I've tried a few different suggested B values for H1 including 4725 with a C value of 7.06e-8. The others were only changing the B value and leaving C alone.

    I'm not getting any faults so I'm not sure the fuse is blown but I did measure the resistance across an endstop ground and vssa on the thermistor pin and got .8 ohms and DC42 mentioned that it should be 2 ohms for a Duetwifi, so I'm not sure what that means.

    Any help would be greatly appreciated!



  • What's your T value? It's easy to miss a zero. For an E3d thermistor it should be 100000. That's 1 followed by 5 noughts.



  • Is it an E3D PT100 sensor or standard? This will help you identify https://wiki.e3d-online.com/wiki/File:PT100_vs_Thermistor.png . What does the sensor read in OHMS at room temp , disconnected from the circuit? What does it read when hot, disconnected from the circuit? 104GT column is for the standard e3d thermister

    Resistance-Temperature Tables (Unit kΩ)
    (C) 102GT 202GT 502GT 103GT 203GT 503GT 104GT 204GT 504GT 105GT
    -50 32.57 111.3 342.1 825.1 1901 4613 8743
    -40 18.48 61.34 175.4 405.3 909.0 2199 4218 8810
    -30 10.84 33.69 92.54 206.6 453.2 1100 2132 4436 12091
    -20 6.594 18.79 50.44 109.9 236.6 576.2 1127 2329 6268
    -10 4.144 10.82 28.49 60.72 128.3 315.1 620.0 1272 3372 6920
    0 2.675 6.424 16.66 34.82 72.32 178.8 353.7 720.3 1880 3833
    10 1.773 3.939 10.06 20.66 42.24 104.9 208.6 421.8 1083 2190
    20 1.203 2.489 6.264 12.64 25.47 63.52 126.8 254.6 642.3 1289
    30 0.8354 1.618 4.019 7.968 15.82 39.62 79.36 158.2 391.9 780.9
    40 0.5918 1.080 2.651 5.164 10.10 25.37 50.96 100.8 245.4 485.2
    50 0.4273 0.7390 1.792 3.436 6.620 16.64 33.49 65.85 157.5 309.0
    60 0.3141 0.5170 1.239 2.341 4.444 11.16 22.51 43.99 103.3 201.2
    70 0.2347 0.3695 0.8753 1.631 3.050 7.645 15.44 29.98 69.20 133.6
    80 0.1782 0.2693 0.6304 1.159 2.138 5.338 10.80 20.82 47.23 90.53
    90 0.1373 0.1998 0.4624 0.8391 1.527 3.795 7.686 14.71 32.84 62.49
    100 0.1072 0.1507 0.3450 0.6181 1.111 2.742 5.556 10.57 23.22 43.90
    110 0.08483 0.1154 0.2614 0.4626 0.8209 2.014 4.082 7.720 16.68 31.34
    120 0.06787 0.08973 0.2010 0.3514 0.6160 1.501 3.043 5.720 12.15 22.69
    130 0.05488 0.07068 0.1566 0.2706 0.4686 1.1133 2.298 4.296 8.976 16.65
    140 0.04483 0.05638 0.1236 0.2111 0.3613 0.8662 1.758 3.269 6.719 12.39
    150 0.03697 0.04550 0.09865 0.1666 0.2820 0.6704 1.360 2.516 5.091 9.330
    160 0.03077 0.03715 0.07967 0.1330 0.2226 0.5247 1.064 1.958 3.903 7.107
    170 0.02584 0.03065 0.06501 0.1073 0.1777 0.4149 0.8414 1.539 3.024 5.472
    180 0.02189 0.02556 0.05358 0.08741 0.1432 0.3314 0.6714 1.222 2.367 4.255
    190 0.01869 0.02151 0.04457 0.07186 0.1166 0.2673 0.5408 0.9796 1.871 3.339
    200 0.01610 0.01826 0.03741 0.05960 0.09573 0.2174 0.4393 0.7919 1.492 2.644
    210 0.03167 0.04986 0.07929 0.1784 0.3597 0.6455 1.200 2.113
    220 0.02703 0.04204 0.06620 0.1475 0.2969 0.5303 0.9726 1.702
    230 0.02324 0.03573 0.05570 0.1230 0.2468 0.4389 0.7946 1.382
    240 0.02014 0.03059 0.04722 0.1032 0.2065 0.3658 0.6539 1.131
    250 0.01759 0.02640 0.04030 0.1740 0.3068 0.5418 0.9323
    260 0.1475 0.2591 0.4519 0.7735
    270 0.1258 0.2201 0.3793 0.6459
    280 0.1079 0.1881 0.3203 0.5424
    290 0.09305 0.1616 0.2720 0.4583
    300 0.08065 0.1396 0.2323 0.3894



  • VSSA sounds fine.

    Could you upload your config.g file, please?



  • It's a regular 104 somethin' er other cartridge and the T value is at its default value. I could have sworn it had the proper number, but I'll check when I get home.



  • @elmoret:

    VSSA sounds fine.

    Could you upload your config.g file, please?

    Sure thing! I'll post that when I get home. Is there something in particular you're looking for? I might be able to recall what I had.

    Also, just to put it out there, it reads 24c at room temp, in case that helps?



  • Sounds like your beta value is wrong in that case, but possibly other values as well. We'll know for sure whether it is a configuration problem once config.g gets uploaded.



  • @elmoret:

    Sounds like your beta value is wrong in that case, but possibly other values as well. We'll know for sure whether it is a configuration problem once config.g gets uploaded.

    I'm guessing that it's not a simple, "I have this thermistor, therefore I use this value?"

    My current values for that are in accordance with the link below (4725), but I've also tried 4388 based on the RRF Configuration Tool. There was a third one that was not far off from what the RRFCT suggested, but I don't recall where I saw it. It's possible that the T value is off by a single 0 and/or I've input something incorrectly, but I checked it a couple times. In any case I'll post the full config when I get home to be sure.

    https://duet3d.com/wiki/Connecting_thermistors



  • It is as simple as "have this thermistor, use these values", but perhaps there's a typo.



  • Here it is. I'm reasonably certain that those values are correct, but I'm probably missing something else entirely. I'm still trying to wrap my head around all the different things you can do and what the variables mean.

    –-------------------------------------------------------------------------------------------------------------------

    ; Configuration file for Duet WiFi (firmware version 1.17)
    ; executed by the firmware on start-up
    ;
    ; generated by RepRapFirmware Configuration Tool on Fri May 05 2017 18:12:44 GMT-0700 (Pacific Daylight Time)

    ; General preferences
    M111 S0 ; Debugging off
    G21 ; Work in millimetres
    G90 ; Send absolute coordinates...
    M83 ; ...but relative extruder moves
    M555 P1 ; Set firmware compatibility to look like RepRapFirmare
    M208 X0 Y0 Z0 S1 ; Set axis minima
    M208 X1500 Y650 Z1500 S0 ; Set axis maxima

    ; Endstops
    M574 X1 Y1 E1 Z0 S1 ; Define active low and unused microswitches
    M558 P4 I1 X0 Y0 Z1 H5 F120 T6000 ; Set Z probe type to unmodulated, the axes for which it is used and the probe + travel speeds
    G31 P600 X40 Y30 Z.25 ; Set Z probe trigger value, offset and trigger height
    M557 X15:1485 Y15:595 S20 ; Define mesh grid

    ; Drives
    M569 P0 S0 ; Drive 0 goes backwards
    M569 P1 S0 ; Drive 1 goes backwards
    M569 P2 S0 ; Drive 2 goes backwards
    M569 P3 S1 ; Drive 3 goes forwards
    M569 P4 S0 ; Drive 4 goes backwards
    M569 P5 S1 ; Drive 5 goes backwards
    M569 P6 S0 ; Drive 6 goes forwards
    M584 X1 Y0:3 Z5:6 E2:4 ; Apply custom drive mapping
    M350 X32 Y32 Z32 E32:32 I1 ; Configure microstepping with interpolation
    M92 X106.76 Y107.37 Z504.54 E647.4:647.4 ; Set steps per mm
    M566 X600 Y600 Z20 E120:120 ; Set maximum instantaneous speed changes (mm/min)
    M203 X6000 Y6000 Z180 E1200:1200 ; Set maximum speeds (mm/min)
    M201 X900 Y700 Z20 E250:250 ; Set accelerations (mm/s^2)
    M906 X2200 Y2200 Z2200 E1680:1680 I30 ; Set motor currents (mA) and motor idle factor in per cent
    M84 S30 ; Set idle timeout

    ; Heaters
    M143 S280 ; Set maximum heater temperature to 260C
    M301 H0 S1.00 P10 I0.1 D200 T0.4 W180 B30 ; Use PID on bed heater (may require further tuning)
    M305 P0 T100000 B4725 C7.06e-8 R4700 ; Set thermistor + ADC parameters for heater 0
    M305 P1 T100000 B4725 C7.06e-8 R4700 ; Set thermistor + ADC parameters for heater 1
    M305 P2 T100000 B4138 C0 R4700 ; Set thermistor + ADC parameters for heater 2

    ; Tools
    M563 P0 D0 H1 ; Define tool 0
    G10 P0 X0 Y0 Z0 ; Set tool 0 axis offsets
    G10 P0 R160 S190 ; Set initial tool 0 active and standby temperatures to 0C
    M563 P1 D1 H2 ; Define tool 1
    G10 P1 X55 Y0 Z0 ; Set tool 1 axis offsets
    G10 P1 R0 S0 ; Set initial tool 1 active and standby temperatures to 0C

    ; Network
    M550 PMyDuet ; Set machine name
    M552 P192.168.1.4 S1 ; Enable network and acquire dynamic address via DHCP

    ; Fans
    M106 P0 S1 I0 F500 H1:2 T45 ; Set fan 0 value, PWM signal inversion and frequency. Thermostatic control is turned on
    M106 P1 S0.1 I0 F500 H-1 ; Set fan 1 value, PWM signal inversion and frequency. Thermostatic control is turned off
    M106 P2 S1 I0 F500 H-1 ; Set fan 2 value, PWM signal inversion and frequency. Thermostatic control is turned off

    ; Custom settings are not configured



  • I can't spot anything amiss with the thermistor settings. I'm wondering if the IR temp gun reading is a "Red Herring" and maybe the Duet displayed temperature is correct. In which case, the reason for the lack of extrusion could simply be a partial blockage in the hot end somewhere.


  • administrators

    I think your thermistor is reading correctly, and you have a different problem. An IR gun won't give accurate results because its target area will be much larger than the heater block. 250C is very high for PLA. What speed are you trying to extrude at? Most extruders can't manage more than 5mm/sec through a 0.4mm nozzle, and 5mm/sec is plenty fast enough for that size nozzle.

    0.8 ohms between VSSA and ground is OK. There are a couple of different types of VSSA fuse used on Duets, and one has higher resistance than the other.



  • I've been considering the same. I found my thermocouple and placed it between the silicone sock and nozzle and measured 200c when the set temp was 235c but I'm not sure if that difference could be attributed to the probe placment or not. I guess if that reading is suspect for that reason I can remove the nozzle and take a measurement inside the heater block.

    Regardless, before I do anything else Ill run some wire through the tip to see if its a partial blockage as you suggested. I kinda hope thats the case at least lol



  • I want to say I was extruding at 10mm/sec, so that could be a factor. Ill slow it down to see if that helps with consistent extrusion. It gets through maybe 40mm before it can't go anymore, but once I give it a few seconds it will go a little more then halt again.

    Tomorrow ill check for a jam, test extrude at 5mm/sec then measure the temp inside the heater block with the thermocouple. Hopefully that'll do it!



  • @efficientAF:

    ….............I want to say I was extruding at 10mm/sec, so that could be a factor. ..................

    Yes that would likely be it - or certainly a contributory factor. I believe the E3D volcano can melt plastic a bit faster.



  • Quick update, I went home for lunch and had time to run a small wire (smallest guitar string works well for .4mm nozzle) to clear out any partial blockages at the tip and test out extruding at 5mm/sec and seems to have helped a little, but just at the tail end of extruding 50mm it stops feeding though. I'll use some polycarbonate filament I have to do a cold pull and see if that will make a bigger difference. I could also check the tension on my idler springs, but those have been set for a while without a problem so they don't seem likely to have tightened up to me, but I could be wrong which seems to be the case as of late!

    Just so I have a better idea of what variables I could check for, in addition to the cold pull, does anyone have any suggestions for what to try? I'm using a hobb-goblin shaft and the teeth are cleared of debris and I'm pretty sure the nuts on either end have not cinched the large gear down onto the extruder body since one side is a nylock nut and the other is using some loctite on the regular nut. The drive gears move smoothly by hand without any current applied, so I think that's off the table as a possibility.

    Sorry if this has morphed from a hardware thing into a more general issue. Just goes to show that just because I'm setting up new hardware, doesn't mean that any problems I encounter are due to said hardware 🙂 The last thing I printed with my Smoothieboard before switching went well so I wasn't expecting the extruder setup to be an issue.



  • Even at 5mm/sec, that's 12mm^3/sec which is on the upper end of how fast the v6 can melt polymer.



  • @elmoret:

    Even at 5mm/sec, that's 12mm^3/sec which is on the upper end of how fast the v6 can melt polymer.

    Sorry if I wasn't explicit, but I'm primarily using PLA for testing the extruder settings, the PC I mentioned is just to do the cold pull to clear out any debris. In any case, since it seems like my issue is not a Duet related issue, I'll work the problem and search for solutions related to the reframed issue. Thanks for the help guys!



  • PLA and PC are both polymers - 12mm^3/sec is on the high end of what a v6 can do.



  • @elmoret:

    PLA and PC are both polymers - 12mm^3/sec is on the high end of what a v6 can do.

    In any case it seems to be doing fine. Is there any way to add custom values on the Paneldue for extrude speed? The lowest it will go is 5mm/sec in the interface. Would be nice to add custom values for movments too.


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