Hotend temperature unstable but printing perfectly

[mikehend]

It was failing prints on me with temperature out of range errors.
I recrimped all the wires and checked continuity on the thermistor and heater core.
I then replaced the heater and thermistor and reran the PID on the hotend.
Still had some issues (maybe a bit better..., but arguably the same...)

I did some research and changed the following setting (See below) and now it doesn't fail but the temperature is still unstable (See graph of a good print).
Those dips can't be good, but the prints look good.
Not sure what else to do to make this better.
I don't even like how the heat is varied up and down. My other printer does not do this.

Any thoughts? Any advice is welcome. Thanks



[verify_heater extruder]
max_error: 480
# The maximum "cumulative temperature error" before raising an
# error. Smaller values result in stricter checking and larger
# values allow for more time before an error is reported.
# Specifically, the temperature is inspected once a second and if it
# is close to the target temperature then an internal "error
# counter" is reset; otherwise, if the temperature is below the
# target range then the counter is increased by the amount the
# reported temperature differs from that range. Should the counter
# exceed this "max_error" then an error is raised. The default is 120.

 

[informel]

It was failing prints on me with temperature out of range errors.
I recrimped all the wires and checked continuity on the thermistor and heater core.
I then replaced the heater and thermistor and reran the PID on the hotend.
Still had some issues (maybe a bit better..., but arguably the same...)

I did some research and changed the following setting (See below) and now it doesn't fail but the temperature is still unstable (See graph of a good print).
Those dips can't be good, but the prints look good.
Not sure what else to do to make this better.
I don't even like how the heat is varied up and down. My other printer does not do this.

Any thoughts? Any advice is welcome. Thanks

View attachment 5573

[verify_heater extruder]
max_error: 480
# The maximum "cumulative temperature error" before raising an
# error. Smaller values result in stricter checking and larger
# values allow for more time before an error is reported.
# Specifically, the temperature is inspected once a second and if it
# is close to the target temperature then an internal "error
# counter" is reset; otherwise, if the temperature is below the
# target range then the counter is increased by the amount the
# reported temperature differs from that range. Should the counter
# exceed this "max_error" then an error is raised. The default is 120.

The heat cannot change that fast, it is normally a bad connection on the heat sensor or broken wire on the sensor. The only other thing I can see is noise that the sensor is picking up

 

[mikehend]

The heat cannot change that fast, it is normally a bad connection on the heat sensor or broken wire on the sensor. The only other thing I can see is noise that the sensor is picking up

That is a good point, it really shouldn't be realistic to change that fast. I think I will try to wire the sensor all the way back to the main board and bypass all the breakout boards.

 

[claudermilk]

I agree, that looks like a wiring issue as the most likely root cause.

 

[AtomAvenger]

I Have been chasing this issue, recently bought and assembled a V0.2 formbot kit, printed fine for a 4 hour stint, then i was getting temp spike like this on and off, on and off, put it down to themister, bought 2 new ones, 1 for back up, put it all back together, same problems, then i found poking the umblical cable right near the thermister wires on the breakout board (on the unit between the x/y motors), i could make it spike on and off, so i put it down to the cable had dodgy wires, (previous to all this i multimetered everthing for conduct pass through) so then i made a make shift cable from indvidual strands of single square plug things (dont know there correct name) they were an extreemly tight fit like jam fit, then i was getting not only themister cut outs the cooling fans were cutting out, so then i hotglued the cables to the plug after reseating them so the cables wouldnt jiggle at all, which i though solved the problem, just then printing a benchy, i had the themister drop in and out, so im at the point im going to elimate the whole umbilical set up cuz i think from something i just found on another someone advised that u slighly bend the pins on the break out board/s so there not straight had solved ther problem, so what is more the problem is the pins in the socket are not in tollerence and causing the intemittent contact (potentally thought thermal expansion/contraction and movment)

the first graph showing me trigging the spikes of the orginal cable (supplied) by movment
my make shift cable to elimate the supplied umbilical cable
the benchy print which stopped with my makeshift (this was after running rock solid for like half hour)

im at a loss on what to do. but your advice on expanding the error threshold might help.

 

[mikehend]

I Have been chasing this issue, recently bought and assembled a V0.2 formbot kit, printed fine for a 4 hour stint, then i was getting temp spike like this on and off, on and off, put it down to themister, bought 2 new ones, 1 for back up, put it all back together, same problems, then i found poking the umblical cable right near the thermister wires on the breakout board (on the unit between the x/y motors), i could make it spike on and off, so i put it down to the cable had dodgy wires, (previous to all this i multimetered everthing for conduct pass through) so then i made a make shift cable from indvidual strands of single square plug things (dont know there correct name) they were an extreemly tight fit like jam fit, then i was getting not only themister cut outs the cooling fans were cutting out, so then i hotglued the cables to the plug after reseating them so the cables wouldnt jiggle at all, which i though solved the problem, just then printing a benchy, i had the themister drop in and out, so im at the point im going to elimate the whole umbilical set up cuz i think from something i just found on another someone advised that u slighly bend the pins on the break out board/s so there not straight had solved ther problem, so what is more the problem is the pins in the socket are not in tollerence and causing the intemittent contact (potentally thought thermal expansion/contraction and movment)

the first graph showing me trigging the spikes of the orginal cable (supplied) by movment
my make shift cable to elimate the supplied umbilical cable
the benchy print which stopped with my makeshift (this was after running rock solid for like half hour)

im at a loss on what to do. but your advice on expanding the error threshold might help.

Hello AtomAvenger.. So, what I did to work around my problem I have above (and very similar to yours) was to just bypass the breakout board altogether and just wire my thermistor directly to the main board. So, this didn't solve the stability completely, but it reduced it to the point it no longer causes any problem and my printer prints very well now. I still see some small spikes on the hotend temperature, but nothing too bad. My suspicion was that the bundle cable just was too stressed when the head moved to the extremes and the connectors maybe just lose contact for a short time and this is enough for my main board to cause the error is reading. I still think my mainboard is sensitive. I did change the thermistor just to prove to myself that was not the issue. No change. Try bypassing the unbiblical and breakout board(s). This is a cheap test and for me, works well enough I left it that way and zip tied the two wires to the unbiblical.