My Dibond Mendel 90 hotend started having some +-5c temp spikes that seem related to my heated bed drawing power. [SEE ATTACHMENTS]




My hotend is a newish E3Dv6, everything else is stock. Only recently started having issues. Anyone have any thoughts or suggestions?

I would measure the voltage on the power supply when the spike occurs and again at the power pins on your printer controller card.

If the voltage drops on the power supply during a spike then your power supply may be under rated.
If the voltage drops only on the controller during a spike then your power supply cables needs to be larger to supply the current to your controller.

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Computer Programmer / Electronics Technician

I am seeing a slight dip in power on the supply: 12.18 to 12.02v when the bed turns on.

Voltage on the hotend is all over the place (which I think is normal when it is maintaining a temp). The bed voltage turns on and off at about 11.3v and the hotend peaks around 11.8v when turned on from being cold.

The only recent cause I can think of is that I recently messed with my hotend to clean a clog from heat creep when my hotend heat sync fan wasn't on.

I re-set and tightened all the connections to the board, I will check the connections at the part ends next...

Thanks for the reply.

On my 3D Printer using the original power wires the voltage would drop from 12 volts to 8.3 volts this was too large of a voltage drop an as it turned out this was my problem.

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Computer Programmer / Electronics Technician

I will have to see if I can find another power supply to rule out the one I have being faulty. It is a 500w EVGA power supply.

I also re-soldered / cleaned the the connections that mount into the screw terminals and added an extra 12v wire from the power supply rails to the 12v input on the board.

And then took some new measurements:

PSU input voltage drop is the same but .02v higher. 12.2 not on load and 12.04v on load. It does not drop below 12.04v.

When heating the hot end from cold:
Without the bed header on: 12.04v at the board / 11.63v at the hot end contacts.
With the bed heater on: 11.85v at the board / 11.45 at the hot end contacts.

When heating the bed from cold:
Without the hot end on: 11.98v at the board 11.52v at the bed contacts.
With the hot end on: 11.88 at the board / 11.48v at the bed contacts.

This seemed to slightly reduce the min / max temp spikes. Please let me know if anyone has any more suggestions.

Thanks again,

Edited 1 time(s). Last edit at 05/02/2022 04:47PM by JaredTS486.

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JaredTS486
I will have to see if I can find another power supply to rule out the one I have being faulty. It is a 500w EVGA power supply.

I also re-soldered / cleaned the the connections that mount into the screw terminals and added an extra 12v wire from the power supply rails to the 12v input on the board.

This seemed to slightly reduce the min / max temp spikes. Please let me know if anyone has any more suggestions.

Thanks again,

Stranded wire clamped in a screw terminal should NEVER have solder on it. The solder cold flows under pressure from the screw, and the connection gets progressively worse and worse as time goes by. Sometimes, very little time (minutes). I'm not saying that you are doing this, but if you are, don't.

I can confirm that the power supply is not the issue. Although between everything I have tried, the power spikes have smoothed out a small amount. I might try a new heated bed next.

I don't see any real print issues other than my printer sometimes will never start after issuing the M109 command. The wait timer resets if the spikes are too large.

I don't think it is a power issue. A small change in voltage would be easily corrected by the control. Perhaps the PID tuning is off as it looks almost like a sinusoidal oscillation.

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[www.hydraraptor.blogspot.com]

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nophead
I don't think it is a power issue. A small change in voltage would be easily corrected by the control. Perhaps the PID tuning is off as it looks almost like a sinusoidal oscillation.

The oscillations only occur when the heated bed initially draws power. I have run the PID auto tuning several times with little variation in the values. Should I be running the PID auto tune while the heated bed is drawing power?

Edit: I can increase and decrease the frequency of the temp fluctuations respectively by increasing and decreasing the temp on the bed. When the bed temp is set higher it switches on and off more frequently to maintain its temp.

Edited 1 time(s). Last edit at 05/03/2022 04:13PM by JaredTS486.

Have you got PID enabled for the BED? It is better than bang-bang because the fluctuations from bang-bang bang can cause the bed to flex.

I don't see how minor voltage fluctuations can cause big changes in hot end temperature.

Are you using the original Melzi we supplied or a different one? Perhaps voltage drops in the ground traces of the PCB are causing thermistor reading variations.

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[www.hydraraptor.blogspot.com]

Quote
nophead
Have you got PID enabled for the BED? It is better than bang-bang because the fluctuations from bang-bang bang can cause the bed to flex.

I don't see how minor voltage fluctuations can cause big changes in hot end temperature.

Are you using the original Melzi we supplied or a different one? Perhaps voltage drops in the ground traces of the PCB are causing thermistor reading variations.

I am fairly sure my version of Marlin does not have the bed PID tuning. Trying to get that updated as you know.

The Melzi I am using is the stock version that came with the dibond kit.

In my firmware I have the temp sensor for the head set to "5 is 100K thermistor - ATC Semitec 104GT-2 (Used in ParCan & J-Head) (4.7k pullup)" The thermistor is a 104NT-2 and the E3D site's wiki on the V6 hotend directs to set it to 5.

I have 2 chamber fans and LED lights hooked up to a mossfet switch board connected to the analog pins that I control with M42 commands. I might try disconnecting everything but the hotend / bed from the board to see if it helps.

I am not currently running my printer but if I remember correctly I also get a slight variation in the hot end temperature during printing.I am using the stock printer except for Neil's version of Marlin, a Panelolu2, Octoprint and an E3Dv6 hot end. As the print quality does not appear to suffer from the slight variations I do not worry about it.

I have more problems trying to release PETG prints from my Kapton Taped Mirror Tile bed without damaging them!

So I upgraded my firmware to nophead's https://github.com/nophead/Marlin and my temp fluctuations are at a minimum now... However...

I noticed an issue with my hotend that seems related to this: https://github.com/MarlinFirmware/Marlin/issues/21661

The hotend stops heating just before the set temp. Sometimes it recovers, other times the printer errors and resets.



From what I read it looks related to the PID tuning kicking in and behaving incorrectly which could be caused by noise on the thermistor reading and the quick fix is to increase PID_FUNCTIONAL_RANGE value.

I guess I will get a new thermistor and see if it helps.

When using an E3D hot end I did need to increase the PID functional range to 20 when using it to print polycarbonate at 275C. I also changed THERMAL_PROTECTION_HYSTERESIS to 10.

Marlin temperature control is a nightmare of complexity. On my old machines with my own firmware I simply used bang-bang and it works just as well, no tuning. It doesn't work on Marlin because it doesn't sample fast enough. I sample probably somewhere around 1Khz, when the temperature is close to the set point noise in the readings causes PWM like control.

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[www.hydraraptor.blogspot.com]

Yes PETG is very sticky. I think people print it on glue or similar 3D printing bed adhesion sprays, not to get it to stick, but to get it to release, when cold.

I have never succeeded with it because it sticks to the nozzle so won't bridge because it rips up adjacent bridge lines it has just made.

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[www.hydraraptor.blogspot.com]

Quote
nophead
When using an E3D hot end I did need to increase the PID functional range to 20 when using it to print polycarbonate at 275C. I also changed THERMAL_PROTECTION_HYSTERESIS to 10.

Marlin temperature control is a nightmare of complexity. On my old machines with my own firmware I simply used bang-bang and it works just as well, no tuning. It doesn't work on Marlin because it doesn't sample fast enough. I sample probably somewhere around 1Khz, when the temperature is close to the set point noise in the readings causes PWM like control.

Thanks that helped! I have an Overture Gold PLA filament that has bad layer adhesion and is super brittle at usual temps. 250c seems to be the sweet spot. ¯\_(ツ)_/¯

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nophead
When using an E3D hot end I did need to increase the PID functional range to 20 when using it to print polycarbonate at 275C. I also changed THERMAL_PROTECTION_HYSTERESIS to 10.

Marlin temperature control is a nightmare of complexity. On my old machines with my own firmware I simply used bang-bang and it works just as well, no tuning. It doesn't work on Marlin because it doesn't sample fast enough. I sample probably somewhere around 1Khz, when the temperature is close to the set point noise in the readings causes PWM like control.

The recent Marlin bugfix includes a temperature control called MPC (Model Prediction Control) that replaces PID for the hotend. It is enabled in configuration.h, and is calibrated using a new g-code, M306 T.

It works very, very well for me.

Yes I saw that but haven't tried it.

Note on my Github I also configured the bugfix branch for Mendel90 and it can be selected as Mendel90_bugfix. It also supports long file names on the SD card but Octoprint doesn't support that properly yet. I raised a couple of issues on the OctoPrint github.

Odd that the "bugfix" branch isn't just the release with bugs fixed. It has new features and some configuration options have different names.

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[www.hydraraptor.blogspot.com]