Hotend turns off randomly  

Re: Hotend turns off randomly

Where did you measure the EINSY output voltage?

Re: Hotend turns off randomly

Could there be a broken wire?

Re: Hotend turns off randomly

Where did you measure the EINSY output voltage?

I stuck some jumper cables in the plug of the cables running to the hotend.

Re: Hotend turns off randomly

Could there be a broken wire?

I measured the output voltage of the Einsy to the hotend at the board, so it wouldn't be a broken wire from the board towards the hotend.

I looked at the 2 power lines coming in from the PSU and they keep providing 24 v even during the power cut

Re: Hotend turns off randomly

Where did you measure the EINSY output voltage?

I stuck some jumper cables in the plug of the cables running to the hotend.

So it's not a broken cable to the heater.
I don't understand the software or electronics, but while you are waiting for more informed members to chime in, here is what i think:

There could be at least 2 causes:
1) The electronics want to supply power, but cannot (some electronic component failure)
2) The electronic think they need to turn off power to the heater element when they should not.
3) The electronics think they should turn off the power and they actually should (safety shutdown).

For scenario 2, a broken heat sensor or sensor cable could be the cause. You can diagnose this further by watching the nozzle temperature displayed on the LCD, before and especially during the failure.

Take not of the temperature fluctuations: If they are gradual and small, going just 1-2degC above and below the target temperature, that's good.
A broken temp sensor cable will be making intermittent contact and function apparently normally, until the z-height reaches the point where the contact becomes intermittent, usually worse at some x-axis point compared to another. This will then cause rapid and obviously erratic temperature display fluctuations, e.g. the displayed temperature drops or rises at an impossible rate, 10, 20, 30 or more degC from one second to the next.
As the x-axis movement bring the cable ends temporarily together again, the actual temperature is displayed again. It may then be a few degC too high or too low, because the heater was turned on or off while wrong information was being fed to the electronics. When the x-position comes to the cable break position again, it begins to jump erratically again. Eventually the (incorrectly reported) temperature remains too low for too long, and the algorithm concludes that there is a serious problem and turns off power to the heater element.

Re: Hotend turns off randomly

So it's not a broken cable to the heater.
I don't understand the software or electronics, but while you are waiting for more informed members to chime in, here is what i think:

There could be at least 2 causes:
1) The electronics want to supply power, but cannot (some electronic component failure)
2) The electronic think they need to turn off power to the heater element when they should not.
3) The electronics think they should turn off the power and they actually should (safety shutdown).

For scenario 2, a broken heat sensor or sensor cable could be the cause. You can diagnose this further by watching the nozzle temperature displayed on the LCD, before and especially during the failure.

Take not of the temperature fluctuations: If they are gradual and small, going just 1-2degC above and below the target temperature, that's good.
A broken temp sensor cable will be making intermittent contact and function apparently normally, until the z-height reaches the point where the contact becomes intermittent, usually worse at some x-axis point compared to another. This will then cause rapid and obviously erratic temperature display fluctuations, e.g. the displayed temperature drops or rises at an impossible rate, 10, 20, 30 or more degC from one second to the next.
As the x-axis movement bring the cable ends temporarily together again, the actual temperature is displayed again. It may then be a few degC too high or too low, because the heater was turned on or off while wrong information was being fed to the electronics. When the x-position comes to the cable break position again, it begins to jump erratically again. Eventually the (incorrectly reported) temperature remains too low for too long, and the algorithm concludes that there is a serious problem and turns off power to the heater element.

Firstly, thanks for thinking with me 🙂

The heat sensor of the hotend seems to be working fine, the fluctuations are small (the problem also occurs when the printer is in preheat mode, without the motor and thus cables moving). The power coming from the Einsy shuts of first, causing the temperature to drop.

The causes that you descriped could be it indeed. I just have no clue how to test them to rule them away/confirm them.

I contacted customer support as well, they also didn't really know what the problem could be.
They are going to send me a new heating element, although I doubt that this will solve it.

Not really sure how to proceed now :/

Re: Hotend turns off randomly

A new heater element will not fix the problem.

I would probably avoid taking the entire cable bundle apart to prove that, and just plug the new heater into the Einsy and into the extruder, but leave the printer otherwise assembled. If it turns out that the new heater does fix the problem, then you have not wasted any great amount of time establishing that.

I don't think you can safely test the new heater without installing it in the extruder, but it's cable can be left loose just for the testing.

I think you will need a new Einsy.

RE:

Hey i got the same problem as you over here.. fixed all connections (The heatbed connection on the prusa mk3s+ is pretty dumb.. two different metals screwed onto each other.. had corrosion on this connection resulting in random connection issues -> resistance altering between the desired 2.8ohms and 100-ish ohms when wiggled around, despite the connection being pretty tightly screwd down. FIX:  sandpaper away the corrosion layer on the copper + added contact spray)

Then I measured the hotend connection.. same thing over there -> fixed by re-crimping the ferrules. once again measured it to be the desired 14.somewhat ohms even when wiggling around the cable.

Also flashed different firmware versions and retested everything.

(To be sure about all connections i fully disconnected and reconnected everything on the mainboard and prepped it to the side of the printer where i could have full access to the connections on the board and be sure about everything being connected the right way.

but there it goes.. Starting a print, everything is fine for a couple of minutes.. but mid-print (while measuing the voltage on the connector -> you will measure alternating mean voltages because the pid/pwm is doing its thing, while being at the desired print temperature it obviously depends on the enviormental conditions  (room temperature) and pid tuning with how much voltage it will keep up the print temperature usually somewhere around 3-6volts) but out of nowhere this voltage drops to zero, measured on the board.

I dont know what to say.. this is not my printer.. a friend of mine asked for help, i myself have a heavly modified ender 3 and i never had such a ****ton of problems at once with it. Amusingly the original problem was the power panic feature being triggered randomly which could only be resolved by disconnecting the power panic connector entirely, as soon as its connected the printer will get caugth in a "power panic loop" [you will find a lot of threads regarding this issue LOL] -> he had it sent in to prusa and the support just replaced the powersupply and returned the printer, saying they had no issues with it.. what the actual hell.

And there goes the first evening of trying to find the issue(s). I guess the mainboard is faulty, which could be fixed, but thats a job for another day. im kind of dissapointed in the prusa support. I think i will re open another thread on this problem just to be sure, that there isnt a solution i did not think of. let me know how you fixed it (i guess you got yourself a new board?)