Voron 2.4 Heater extruder not heating at expected rate. Printing stopped and Error resulted.

[eugen360]

13 hours ago, smirk said:

I might be misreading but one thermistor (using the multimeter) is reading  85 kOhms and the other is at 114 kOhms at the same ambient temperature (basicly "room temperature")?

Yes, that's correct, one 85 and other 114, but both are showing in dashboard 21-22 degrees "room temp". They are exactly the same type, like the one in the above attached picture. So... if on both ports (bed and hot-end) I have the same behavior when using this combo of heater tube and NTC... what should I do next? And I repeat, I already tried 2 sets so buying another one I'm not sure solves this problem.

I'm lost...

[smirk]

I'm stumped right now as well. So to summarize (sorry it helps me):

1. The hotend heater, "heats up" far too quickly and exceeds the maximum temperature of 245C (?) before things halt with an error. The fact this happens and does so quickly prevents you running a PID calibrate to see if you can tune the performance better.
    
2. Your Printer control board is a SKR E3 mini v2.0 - which only has two thermistor ports (heated bed and hot end).
    
3. You have tried alternate physical thermistors and the issue remains. The assumption being it's therefore not the thermistor or wiring at fault (unless you have multiple faulty thermistors ).
    
4. You have swapped around the hotbed and hotend connections and set up, and the issue followed the swap which indicates the the ports on the SKR E3 are "OK" otherwise the problem would not have followed the swap.
    
5. Both hotend and hotbed thermistors are the same model (Generiic NTC 100k types); at ambient (room) temperature both read at the same level of 21-22C. This is what you'd expect and again indicates the setup operates as expected.
    
6. You have questrioned the validity of the 24v hotend heater - not 100% sure it's not really a 12v hotend heater. My view this would not be the source of the issue but, if true, could result in the heater burning out as it is running beyond it's rated capability.
    
7. "Untested" things in common across all points 1 - 6: the hot-end heater and the klipper config. I say "untested" from my point of view (I think you will have tested them).

 

Here's my thinking, perhaps I'm wrong about #6. The heater is essentially a resistor (reistance generates heat). Running a 12v heater at 24v will draw more power (given it's lower than expected internal resistance). Perhaps it is heating the heater-block up quicker than Kilipper is polling for it? You can check what sort of heater you have - again by measuring the resistance with you multi-meter:

    12V 20W -> ~ 7.2 Ω
    12V 30W -> ~ 4.8 Ω
    12V 40W -> ~ 3.6 Ω
    24V 20W -> ~ 28.8 Ω
    24V 30W -> ~ 19.2 Ω
    24V 40W -> ~ 14.4 Ω

(Some generic numbers for comparison. I'm guessing the heater would be in the 40W mark so you'd be looking at 14.4 Ohm for 24v or 3.6 Ohm for the 12v).

There are some setings in the [extruder] (or heater) section that perhaps could "help":

max_power

Granted that "max_power" option might not even appear in your [extruder] section, but you can simply add it.

By default max_power is 1.0, but perhaps reducing it to a very conservative 0.25, e.g. "max_power: 0.25", will change the heat-up time. Noting it might reduce things to a point where you never acheive the desired temp but at least you could walk it forward from there perhaps incrementally increasing it up to 0.6.

I know with the V0 if you are running a 100w heated bed they recommend running  max_power at something like 0.8 to prevent you from overheating the bed (not surprising given it's such a high-power in a small space).

[smirk]

If if it does turn out to be a 12v hotend heater, beyond apologising for leading you on a merry dance checking thermistors, I really cannot stress the need to get a proper 24v one. That "max_power" setting does not really reduce the power going into the heater, it merely reduces the amount of time that the heater is being energised in any given unit of time. Basically the board cannot reduce the level of power - the heater port is basically either on at full power (24v) or completely off. All that happens is it's turned on for a fraction of each second (say) rather than the full-second. So the heater will still burn out eventually.

[eugen360]

You are correct in almost all points!  

(at point 5) The heated bed thermistor type it is unknown for me because it is sealed in the silicone heater and on aliexpress it doesn't mention it's type ... in the config file I've set it to generic 3950 and it works Ok.

Again, I'm at work so when home again, I'll measure the heater resistance... I'm very curious about it's value! And also I'll introduce max_power because it is missing right now. I saw this option exist but didn't think about trying it, until now...

Thank you very much Smirk for your willingness to help!

[smirk]

9 minutes ago, eugen360 said:

I've set it to generic 3950 and it works Ok.

I think that's absolutely safe and valid. Even legitimate Keenovo heaters use some generic NTC100k/3950 thermistor - so if they get by on generics so too will everyone else (just cheaper ).

10 minutes ago, eugen360 said:

Thank you very much Smirk for your willingness to help!

Anytime!

[eugen360]

7 hours ago, smirk said:

    12V 20W -> ~ 7.2 Ω
    12V 30W -> ~ 4.8 Ω
    12V 40W -> ~ 3.6 Ω
    24V 20W -> ~ 28.8 Ω
    24V 30W -> ~ 19.2 Ω
    24V 40W -> ~ 14.4 Ω

 

Well... surprise! Can you guess it? Both tested tube heaters have 5.5-5.8 ohms. Unbelievable!

[smirk]

Well congratulations on being the owner of two mis-sold heaters! Clearly I'm getting old and had forgotten my basic  ellectronics. At 12V your heaters would pump out 26W (pretty poor) but over clocking them (as it were) pumps out a whole 104W. Clearly that'll make a heat-block toasty a lot fast than expected. Reducing that power setting might be a stop-gap but I  would strongly recommend getting new heaters - or even if you had a buck-converter and could step down the 24v to 12v for the hotend that would be "better".

[eugen360]

I don't want to use buck converters or any other "workaround" ...  this morning, having again a hunch, I've ordered a new set of heater tube and thermistor but both, other types than those I have. Also sent a letter to the seller letting him know about the error he made. These parts are really not expensive but the fact that I have to disassemble the hot-end, take off the braided cable management, with hot-shrinking tube on both ends and all the other things to change the heater and it's wires....

Well, I really hope this new heater will solve at least this problem and my little Voron will be able to print some day soon... I'll keep you posted!

[smirk]

1 hour ago, eugen360 said:

I don't want to use buck converters or any other "workaround"

I can totally respect that, I'd take the same approach. This kind of thing becomes less of an issue once you collect enough spares (you can replace anything at hand). Still doesn't take away the hassle of having to strip stuff down and re-run the cabling.

At the risk of cursing things, the heater is probably the solution. You've really eliminated other aspects of cabling; physical thermistors; MCU ports and configuration. The heater was about the only bit left. If I were a physicist (i.e. knew better) then it's possible to calculate the heat up rate for the block (you know the power, you know the material and dimensions of the block). I say that like it's an easy back-of-a-fag-packet calculation (it's not). Like I say I'm no physicist. It'll be good to see the outcome.

[smirk]

On 11/8/2022 at 12:43 PM, eugen360 said:

100 in like 5-6 seconds.

I'm not a phycisict but I can use google I found a web page that provided the formula for calculating heat up times for objects. Making some sensible assumptions about the size of a (aluminium) heater block; and the known facts about your 12v heater running at 24v (to produce 104W of power) and remarkably according to the formulas it would take 6.230769231seconds to heat up the heater block from 20C to 100C.

So that kinda makes me feel more confident to say "yup" it was your missold heater that was the cause of the rapid temperature fluctuations.

[eugen360]

Thanks for the link Smirk! It's always good to accumulate more and more knowledge!

One question still remain for me: I understand the rapid temp fluctuation caused by the wrong hardware but why can not be stopped by the firmware? You set the temp to stop let's say at 50 and it goes up to 100. So the thermistor in "working" and it's telling the software "hey I'm way beyond the 50"  Why did not stop at 50 or 55?

[smirk]

The control algorithms will allow for hysteresis so you always get "some" overshoot or undershoot. Without digging into the code I suspect the issue is the rate of change - it's too great for the PID controller to keep up. The PID algorithm will only sample the temperature every so often (possibly fractions of a second) with the implcit assumption that the rate of change is going to be "sensible". Along with the sample rate, the algorithm would only be able to make so many corrections in any given unit of time as well so I suspect the temperature was changing too quickly (by too much) for the algorithm to be able to correct in the time available to it. After-all the cool-down rate for the block would remain "normal" as that's not a function of the heater it's a function of other physics effects/properties (radiation, conduction, etc) which I no longer remember now.

I imagine if you'd ever managed to get to the stage of running a PID calibrate it would have eventually failed/given up as it woud not have fundamentally being able to get the temperature stable and under control.

Granted that's just a theory - I would need to peruse the klipper internals to understand the time.

One of the interesting things (again noting I'd need to peruse the code) is I imagine all the safety mechanisms are expecting a failure (say the heater falling out of the block) to look like the temperature not increasing fast enough. I guess it doesn't make too many assumptions about a faster rate of increase (as there are genuinely different powered heaters) so you've probably "only" got some maximum temperature setting as a back-stop. So you possibly found a failure mode that others had not considered (or could not figure out how to reasonably protect against).

[smirk]

Ho ho, found a reference in the klipper documentation relating to verifying the heaters (setting the temperature to 50C) they say it should reach temperature "(within about 30 seconds or so)". Given that''s only a 30 degree difference from ambient and they think it might take roughly 30 seconds which (with your set up) you would achieve in about 2 seconds we can kinda see the problem with their assumption

I'll stil go and have a dig further.

[claudermilk]

Glad you figured out what the issue is. That is certainly not something obvious.

[eugen360]

Well friends... I have some news!

Installed the new heater cartridge (NTC also) and bells and whistles... successfully did a PID calibration of the hot-end! Yaaay! Funny thing, first try was an error reported by Klipper "Heater extruder not heating at expected rate... printer shutdown". I thought I'll have a stroke or heart attack but then I remembered that I was "playing" yesterday in the config file trying different things... corrected those and all was just fine...

Thank you very much for your precious help Smirk! I wish you all the best!

[smirk]

Huzzah! So glad it's working now.

51 minutes ago, eugen360 said:

then I remembered that I was "playing" yesterday in the config file trying different things...

Yup, i've fallen into that trap many times and it certainly won't be the last time either.

[rasolmarzban]

My problem is that when I try to increase the temperature of the extruder to 190, the temperature of the extruder increases very slowly and temp rate after temp=100 the rate= 0.0 until 110 temp rate. After that it gives the error verify_heater! What should I do?

[mvdveer]

10 hours ago, rasolmarzban said:

My problem is that when I try to increase the temperature of the extruder to 190, the temperature of the extruder increases very slowly and temp rate after temp=100 the rate= 0.0 until 110 temp rate. After that it gives the error verify_heater! What should I do?

The problem could be one of two things initially:

1. Ensure you have the correct thermistor type in your printer.cfg file under [extruder]

2. Ensure you have a good connection from your thermistor to your controller board.

If these are good, then you may have a faulty heater/thermistor and this should be replaced.