3

I am looking for troubleshooting help on my printer. Recently the hot end just can muster the courage to go past about 70 °C.

The hardware - Ender 3V2 with a E3D V6 hot end. 24 volts

I changed the thermistor to a new one. Before heating, it registers an appropriate 10 °C in line with the bed temp sensor.

With the thermistor checked good, I looked at the heater element. It is reading 22 Ω. The documentation from E3D is not clear in what wattage heater I bought, but if it is a 30 W 24 V heater, it's on the high end of acceptable.

  • A 24 V 30 W heater cartridge will read between 16.7 - 22.6 Ω.
  • A 24 V 40 W heater cartridge will read between 12.3 - 15.1 Ω.

If anyone is able to confirm how to know what my heater wattage is supposed to be, LMK. Options are shown for blue wires, red wires, and yellow. I have yellow.

If the resistance is in spec, I checked if the voltage being supplied to the heater is correct. It is reading 23.6 V which seems good.

I have attempted to PID autotune in Pronterface which I had also done several times previously before the issue. If I try to target anything over 70 °C, the attempt to tune fails because it can't get hot enough. I can tune if I set the temp to 65 °C by comparison.

The temperature trace in Pronterface shows the temp rising quickly through the 30s, 40s, then plateauing and maxing out in the high 60s.

I am looking for advice on where to look next for trouble shooting. Seems odd to suddenly have such a low temperature limit capability that I can't root cause.

Greenonline
  • 5,831
  • 7
  • 30
  • 60
Will Wilson
  • 31
  • 1
  • 2
    Power to the heater is PWM. Reading voltage to the heater with a voltmeter may not give an accurate picture of what the heater driver is delivering. If available, an oscilloscope would show the output duty cycle and provide a better understanding of how much power is actually being delivered to the heater resistor. – allardjd Mar 17 '22 at 13:27
  • Your description of the heat up curve suggests that the controls are attempting to control at the lower than desired temperature for whatever reason - setting? Wrong or bad RTD? – allardjd Mar 17 '22 at 13:36
  • 1
    If the heater PWM duty cycle diminishes as temperature approaches the maximum the electronics are attempting to control at that temperature. If the duty cycle remains high the heater/power supply are insufficient to achieve a higher temperature. – allardjd Mar 17 '22 at 13:46
  • 1
    As a way to confirm the low temperature reading is accurate try to extrude some filament. If you can do so the low temperature indication is incorrect. – allardjd Mar 17 '22 at 15:54
  • 1
    @allardjd I was curious if the control to the heater was PWM to hit a set point. I got a suggestion elsewhere to power directly to 24V and see if it was capable of hitting higher temperatures. I connected the heater element directly to an extra Vout on the PSU which should be capable of 6 or 7 amps. Doing this most certainly achieved a higher temperature, but it reached a steady state of 170C and could not really go over that. It added the last 1 deg after 25 seconds of waiting at 169C. So my take away was the element is bad and I ordered a new one. We'll see the results this weekend – Will Wilson Mar 18 '22 at 14:39
  • Still a bit of a mystery here. Your experiment suggests that the heater is capable of about 170C. However it only reaches 70C under normal control. 24VDC should be equivalent to 24V PWM @ 100% duty cycle but that's not happening. Curioser and curiouser. – allardjd Mar 18 '22 at 15:48
  • @allardjd I agree with your point on 24VDC being equivalent to 24V PWM @100% duty cycle. My assumption that I can't verify with measurement is that there is an upper limit on the duty cycle for the heater. Perhaps max output is still 80% duty cycle. IDK just speculation. – Will Wilson Mar 25 '22 at 19:04
  • @allardjd in any case the element just arrived today. It is 70W this time. Powering from PSU it hit 200C before being turned off manually. Powering from the controlled pins I can only achieve 186C asymptotically. Same behavior but new limit number with higher wattage heater. IDK how to proceed with debugging. Thermistor and Element are both new. Seems problem must be on motherboard but how to isolate that and prove it? Could I swap the element to the pins for the bed heater and have marlin tell the board those are the pins for the nozzle? – Will Wilson Mar 25 '22 at 19:07
  • 2
    I have the answer. It was mechanical. The heat from the element was being dissipated by the heat sink and fan faster than it could be input. The heatbreak was screwed in to deeply to the heater block allowing the heat sink to be screwed onto the heat break far enough to make contact with the heater block itself. The heatbreak was not providing a break but a direct path for heat to radiate away. This is why heating from 2 different wattages resulted in achieving 2 maximum temps. Tore down and reassembled hot end. Works fine. @allardjd – Will Wilson Mar 27 '22 at 00:22
  • @WillWilson: For future reference, this is a data point for how helpful it would be to include photos with your question. Anyone who saw the photo could have told you that right away. Also: rather than burying it in a comment, you should write up the answer (you even said: "I have the answer"!) as an actual answer and click the check mark to accept your own answer, so that this question shows up as solved (having an accepted answer) and so that others can easily find and read your answer. – R.. GitHub STOP HELPING ICE Aug 31 '22 at 14:18

2 Answers2

0

If you're using the same RTD for both tests you can rule that out as a source of the problem. At this point I'd suggest, A) thoroughly scrubbing all the machine parameters and software settings for something that's limiting temperature or duty cycle, and, B) buying or borrowing an O'scope to see what the board is really putting out. Connecting the heater to the bed heat pins will be limited to however high the bed heat can be set so may not tell you much. I don't know if it's possible to swap hot end and bed outputs in software. If so, I don't know how.

allardjd
  • 310
  • 1
  • 1
  • 10
  • Darn - I meant that answer to be a comment. Here's another thought - if the new RTD is the wrong range or slope you may be achieving a higher temperature than indicated. It's worth trying to get an independent measurement of actual hot end temp. – allardjd Mar 25 '22 at 23:25
0

There are several points to check to trouble shooting this issue but commonly there are a loose part.

  1. The heating elements is loose, try to tight the cartridge to the aluminum block.
  2. The Sensor temperature is not touching the aluminum block or is outside of its position. Maybe the heating element is correct but the sensor is not taking the right value.

If the temperature rises too slow and downs more quickly than normal is due the temperature sensor is out of it position.

Other issues: The PWM control is over heated, so this will need to replace it or change the transistor (FET), however this is not a common problem.

The other one and more common that PWM over heated is the Power Source, as well like the PWM control the power source decreases his potencial on current supply. For me is easier replace the power source instead verify the PWM control.

Now I´ve done that for second time in 6 years of printing. How Can I deduce that the PWM is not overheated?, I have a cooling fan for all PWM controls on the RAMPS 1.4 Module.

Fernando Baltazar
  • 1,420
  • 3
  • 13
  • 21