When you look at the temperature and power characteristics shown in the previous post here:
you will see that there is clearly no issue with the PID control loop except it is slightly noisy, but not excessively so. So the PID constants are fine.
I am pretty certain that this is the “Makerbase Issue” that I referenced before. @Neroythd I would suggest the following steps for troubleshooting to attempt to isolate the root cause:
Home the printer and then park the print head approximately in the middle of the print volume.
Disable the steppers and make sure the parts fan is not running.
Bring the hot end to temperature and let it stabilize for a few minutes, make sure that you watch both the temperature graph and the power. Also make sure that Klipper does not time out, you may wish to extend the default timeout time to more than 10 minutes
Manually command 100% parts cooling fan. Watch the hot end temperature and power and wait till it stabilizes. Then command parts cooling fan back down to 0% and watch the hot end temperature and power again. This will isolate purely the response of your hot end temperature to the cooling fan, but note that it will be a bit different (less pronounced) than it would be with the nozzle almost touching the bed due to the aerodynamic differences.
Heat the bed to a reasonable temperature above ambient and let it stabilize. Watch the hot end temperature and power. After some time set the bed temperature back to zero. This will isolate purely the response of your hot end temperature to the large changes in the power supply load (the bed heater).
Home the printer. Watch the hot end temperature and power. This will isolate purely the response of your hot end temperature to the higher frequency moderate load changes and EMI caused by the XYZ stepper motor function. If required, you can manually command the print head to move around or simulate a print pattern with no extrusion.
Home the printer and then again park the print head approximately in the middle of the print volume.
With hot end still at temperature, manually extrude some plastic at different speeds. This will isolate purely the response of your hot end temperature to the higher frequency moderate load changes and EMI caused by the extruder stepper motor function. The extruder motor wires typically run a long distance along the thermistor wires and couple noise into the thermistor input of the ADC.
Please report once done. You may wish to take screen shots of the temperature and power display at the above steps to illustrate your findings.
EDIT: Actually looking again at the same plot that I referenced, it in itself potentially confirms my “Makerbase Issue” theory. Note that around the time the hot end PWM comes on, the bed temperature does a strange step change followed by a slow return. This is not normal and is indicative of ADC implementation issues IMHO. The strange thing is that the bed temperature change happens before the hot end power comes on. In any case, I would recommend that you complete the steps I listed above as it will clearly demonstrate the issue.
The problems with the heating bed I have mostly fixed by the original PID values. Now the bed fluctuates at most 0.1-0.2. With the values of the PID tuning, it was 1-2 degrees.
In this picture you can see that at 18:59 o’clock the fans are switched on to 100% and at 19:05 o’clock the fans are switched off.
At 19:06 I then turn on the heating bed with a target temperature of 75 degrees and at 19:11 I turn it off again.
In the last picture, at 19:18, I start to home the printer and make random movements. From 19:21 I start extruding PETG in different lengths and speeds.
During the extrusion, you can see that the temperature starts to fluctuate. In some cases, up to 1.5 degrees. In the other tests, the temperature also fluctuates somewhat, but usually by ± 0.2 degrees when it has stabilized.
To be honest this does not look abnormal at all to me, although the temperature variation is a bit on the high side. Even in very well tuned printers you are going to see small temperature variations when there is a sudden heat flux change, like fan switching on or off or the extrusion rate changing rapidly.
Your results do not seem to indicate that the “Makerbase Issue” is there, at least not to a significant degree. How is the heater and thermistor installed on your printer? Perhaps there are some thermal conductivity issues?
Otherwise I concur with what @Sineos already mentioned - you can probably benefit from a refinement in PID tuning. Have a go at the experimental branch that he highlighted, or if you are brave you could try a manual PID derivation. You can possibly also benefit from adding smooth_time: 1.0 or perhaps even smooth_time: 1.5 to your [extruder] configuration block.
I am also curious why your heater is 50W - did you change it? Normally 40W is more than enough for “standard” printers…
For reference, +/- 0.2 deg.C fluctuation on bed is what I would consider “normal” and +/- 0.5 deg.C hot end temperature fluctuation. My printer has (meticulously) manually tuned PID parameters and the bed temperature always stays well within +/- 0.1 deg.C while the hot end (Dragon SF) will flustuate +/- 0.2 degrees during printing and +/- 0.7 degrees when doing “silly” tests like switching fan 0% to 100% etc.
To help you recalibrate your expectations, here is a snapshot from one of my printers on which, as I said before, the PID constants were manually tuned:
The first “blip” in temperature is when I selected the part cooling fan from 0% to 100%, just before 16:18. Just before 16:19 I switched the cooling fan back from 100% to 0%.
The second blip in temperature is when I commanded extrusion of 50 mm of ABS at 5 mm/s via G1 E50 F300 in relative extrusion mode. You can see that the hot end temperature dropped by about 1 degree C due to heat transfer into the melting filament. You can also see the level of random noise on the PWM commanded power - about +/-10%.
Again, I would consider this an EXTREMELY well tuned PID control loop.
An finally: Is this accuracy really needed? I don’t think so. We all print PETG with 235 deg using completely different printers… But my heat tower indicated, that something from 230 to 245 would also be ok… It’s a little bit like catching shadows…
It does not matter if you print PETG with 230, 235 or 240 °C. But it should be consistent.
If it gets hotter, the material gets more viscous and that can effect the print quality.
So you need a well tuned PID loop to keep the temperature where it belongs.
Thin ice!
I am not convinced, that it takes 1 deg± do decide if the print is good or not. And viscosity will not jump around in a 2deg range. In areas of small change in temp, viscosity can be assumed as linear. So 1 deg of 235 deg = 0,4%… I am even not convinced, that it needs a PID controle… (so I am a 3D printer heretic)
I do not want to start religious discussions: I think all is ok and the case is more or less closed. Let’s print something!!!
It all depends on what your goals are. Fundamentally, if you have the ability to calibrate your tools properly you always should. It is a small amount of effort required to reap continuous long term rewards.
For example, I personally either use PT1000 RTDs or thermistors that have been calibrated against a known, good reference such as PT100 or PT1000. Many people in 3D printing “don’t care” how accurate their hot end is in absolute terms because they pick an “optimal” temperature based on some extrusion test of each filament they use. But it matters when you use several different printers, once you realize that a typical thermistor can have in excess of 10 or even 15 deg.C error at printing temperatures. When I set 255 to print ABS on my Voron or on my heavily modified CR-10S Pro I know that they will both be within +/-1 deg.C.
The same philosophy applies to maintaining the nozzle temperature, as @EddyMI3D pointed out earlier. You will be able to produce good prints even if your nozzle temperature fluctuates +/- 10 deg.C. But the extrusion quality will suffer and even more importantly the part strength and consistency will be severely impacted. Some people don’t care, but others do.
This is one of the aspects of 3D printing that allows companies like Stratasys to certify their overall printing processes front-to-back for critical applications like aerospace: from 3D model to 3D printed part the outcome consistency and repeatability is guaranteed, and it involves hundreds of individual steps that combine to form a qualified process.
I have now done another 5 hour print with PETG and have noticed at most ± 0.7 degree fluctuations. I do not know why, but the larger fluctuations have disappeared. My biggest problem was not the fluctuation itself, but that due to the temperature fluctuation I got the error message “verify heater” and the pressure was canceled.
And sorry for the late feedback, had a lot to do the last few days.
It seems to me though that you may have another dormant issue lurking in the background, like perhaps a loose pin or a questionable crimp in the thermistor loop. The “verify heater” faults would be a consequence of substantially more severe temperature anomalies.
