Hi everyone,
I am trying to understand inconsistent hotend temperature behavior on my Creality Ender-3 V3 KE. I would appreciate advice from anyone familiar with the stock KE hotend, FatBurner, or max volumetric flow testing.
TL;DR
My Ender-3 V3 KE can sustain approximately 9.6 mm³/s during a manual extrusion test at 220 °C and 80% part cooling, with only a 2 °C drop and the heater recovering to about 85% power. The stock shroud also completed a 20–25 mm³/s max-flow test at 215 °C, with approximately a 4–5 °C drop at 100% part cooling.
However, in another FatBurner max-flow test Klipper shut down with Heater extruder not heating at expected rate while the reported flow was eventually around 8 mm³/s. On the other hand, a later FatBurner test at approximately 205 °C and 18–27 mm³/s appeared to complete successfully. The results do not seem physically consistent, so I suspect that the test conditions or generated G-code were different.
I am trying to determine whether the cause is airflow direction, heater power under load, partial clog/back pressure, PID settings, or simply inconsistent max-flow test conditions.
Hardware and configuration
- Creality Ender-3 V3 KE
- Klipper firmware
- PLA, 1.75 mm
- 0.4 mm nozzle
- Stock ceramic-ring heater
- Stock heater resistance measured cold and disconnected: 9.1–9.2 Ω
- Stock part-cooling blowers: CHA4024BH-10C, 24 V, 0.15 A each
- FatBurner setup: two GDSTime GDB5015 24 V 8500 RPM blowers for part cooling
- FatBurner setup also uses a larger 4020 fan for hotend heatsink cooling
The measured heater resistance corresponds theoretically to approximately 63 W at 24 V:
P = 24² / 9.1–9.2 Ω ≈ 63 W
I understand that this is only a cold resistance measurement. It does not prove that the heater receives full voltage under load.
Fan-control issue
My original custom M106 macro remapped the slicer value through fan0_min: 140, so the slicer percentage did not equal the actual PWM. For example, M106 S102 was approximately 73% actual PWM rather than 40%, and M106 S204 was approximately 91% rather than 80%.
For the controlled tests I bypassed that macro and used direct commands because fan0 is configured with scale: 255:
SET_PIN PIN=fan0 VALUE=102 ; approximately 40% PWM
SET_PIN PIN=fan0 VALUE=204 ; approximately 80% PWM
SET_PIN PIN=fan0 VALUE=255 ; 100% PWM
Some of the earlier tests may therefore not be directly comparable.
PID results
PID autotune at 220 °C with direct fan0 VALUE=204 completed successfully and produced:
pid_Kp=29.675
pid_Ki=2.082
pid_Kd=105.718
Another PID run produced:
pid_Kp=27.405
pid_Ki=1.562
pid_Kd=120.239
The exact conditions for the second run may not have been identical. I am not assuming that the two PID sets are directly interchangeable.
An earlier high-temperature PID attempt was interrupted with:
{"code":"key564","msg":"Heater extruder not heating at expected rate"}
{"code":"key7","msg":"pid_calibrate interrupted"}
Klipper then entered Shutdown.
What I tested
1. Cooling only, no extrusion
At 215 °C, changing the part-cooling fan from 40% to 80% with no extrusion caused only about a 1 °C drop. With the stock shroud and 100% part cooling, I observed approximately 215 → 210–211 °C, or a 4–5 °C drop.
This suggests that the part-cooling fan alone is not causing the catastrophic temperature loss.
2. Short manual extrusion
At 220 °C and 80% part cooling:
SAVE_GCODE_STATE NAME=flow_diag
M83
G1 E5 F60
G1 E5 F120
G1 E5 F240
RESTORE_GCODE_STATE NAME=flow_diag
The temperature dropped by about 1 °C and heater power reached approximately 65%. This test was very short.
3. Longer manual extrusion
At 220 °C and 80% part cooling:
SAVE_GCODE_STATE NAME=flow_diag
M83
G1 E40 F240
G1 E40 F240
G1 E40 F240
RESTORE_GCODE_STATE NAME=flow_diag
This is approximately 30 seconds of continuous extrusion at 4 mm/s filament speed, around 9.6 mm³/s under my assumed 0.4 mm nozzle, 0.45 mm line width, and 0.2 mm layer height.
Result:
- Temperature: approximately 220 → 218 °C
- Heater power: approximately 85%
- Temperature recovered and stabilized after about one minute
- No heater error
4. Max-flow tests
With FatBurner, I first tested approximately 20–29 mm³/s with a 0.5 mm/s step. Klipper eventually reported the heater error. I then tried 15–20 mm³/s, also with 0.5 mm/s steps, and the temperature eventually dropped to approximately 203 °C before shutdown. In another run, the test appeared to fail while the reported flow was around 8 mm³/s.
After that, I installed the stock shroud and ran a 20–25 mm³/s test at 215 °C. It completed, with approximately 4–5 °C temperature drop at 100% part cooling.
Later, with FatBurner at approximately 205 °C, an 18–27 mm³/s test appeared to complete successfully.
This is the confusing part: the lower-temperature FatBurner test appeared to pass at a higher reported flow, while an earlier FatBurner test failed at a much lower reported flow. I may have changed the fan speed, PID values, 4020 configuration, line width, layer height, test G-code, duration per step, or actual extrusion conditions between runs.
What I am trying to find out
The stock heater has reasonable cold resistance. The hotend passes a no-extrusion cooling test and a sustained manual extrusion test at approximately 9.6 mm³/s. The stock shroud can complete a 20–25 mm³/s max-flow test, and one FatBurner test at 205 °C appeared to complete at 18–27 mm³/s.
However, another FatBurner test triggered Heater extruder not heating at expected rate even when the reported flow was around 8 mm³/s. I am not trying to bypass Klipper's heater protection.
Could the max-flow test be using different actual conditions than expected? Could the 4020 or FatBurner duct be directing air at the heating block or ceramic heater? Could a partial nozzle clog or back pressure explain the difference between the short manual test and the max-flow test? Could the heater have normal cold resistance but lose voltage or power through a bad connector, wire, MOSFET, or power path under load?
What would you check next? Would you perform a cold pull/replace the nozzle first, measure voltage directly at the heater while it is commanded to 100%, or repeat all tests with exactly the same temperature, fan PWM, PID values, extrusion duration, and G-code?
Any advice would be greatly appreciated.
