Hotend losing heat just as print starts

Basic Information:

Printer Model: Wanhao Duplicator i3 V2.1
MCU / Printerboard: Stock
Host / SBC: mainsail
klippy.log:
klippy.log (205.1 KB)

Hi!

I’ve had this problem recently, that whenever I start a print at a “lower” temperature (say 180c), the printer will pre-heat, hold, and then drop much too low just as it starts to actually print.

image

I can see that in the klippy log that the target temp doesn’t change but the hotend just seems to suddenly lose heat as the print starts?

Stats 290484.7: gcodein=0  mcu: mcu_awake=0.011 mcu_task_avg=0.000097 mcu_task_stddev=0.000072 bytes_write=58075 bytes_read=69987 bytes_retransmit=0 bytes_invalid=0 send_seq=3492 receive_seq=3492 retransmit_seq=0 srtt=0.003 rttvar=0.000 rto=0.025 ready_bytes=10 upcoming_bytes=0 freq=16003704 sd_pos=34146 heater_bed: target=60 temp=60.2 pwm=0.081 sysload=0.03 cputime=13.862 memavail=674412 print_time=11706.939 buffer_time=0.000 print_stall=0 extruder: target=180 temp=181.5 pwm=0.206
Stats 290485.7: gcodein=0  mcu: mcu_awake=0.011 mcu_task_avg=0.000097 mcu_task_stddev=0.000072 bytes_write=58166 bytes_read=70126 bytes_retransmit=0 bytes_invalid=0 send_seq=3498 receive_seq=3498 retransmit_seq=0 srtt=0.004 rttvar=0.000 rto=0.025 ready_bytes=0 upcoming_bytes=0 freq=16003704 sd_pos=34146 heater_bed: target=60 temp=60.1 pwm=0.256 sysload=0.03 cputime=13.892 memavail=674412 print_time=11707.941 buffer_time=0.000 print_stall=0 extruder: target=180 temp=181.2 pwm=0.270
Stats 290486.7: gcodein=0  mcu: mcu_awake=0.011 mcu_task_avg=0.000097 mcu_task_stddev=0.000072 bytes_write=58247 bytes_read=70251 bytes_retransmit=0 bytes_invalid=0 send_seq=3504 receive_seq=3504 retransmit_seq=0 srtt=0.004 rttvar=0.000 rto=0.025 ready_bytes=0 upcoming_bytes=0 freq=16003704 sd_pos=34146 heater_bed: target=60 temp=60.1 pwm=0.381 sysload=0.03 cputime=13.922 memavail=674412 print_time=11708.942 buffer_time=0.000 print_stall=0 extruder: target=180 temp=180.6 pwm=0.577
Stats 290487.7: gcodein=0  mcu: mcu_awake=0.011 mcu_task_avg=0.000097 mcu_task_stddev=0.000072 bytes_write=58311 bytes_read=70385 bytes_retransmit=0 bytes_invalid=0 send_seq=3509 receive_seq=3509 retransmit_seq=0 srtt=0.003 rttvar=0.001 rto=0.025 ready_bytes=0 upcoming_bytes=0 freq=16003704 sd_pos=34146 heater_bed: target=60 temp=60.2 pwm=0.000 sysload=0.03 cputime=13.951 memavail=674412 print_time=11709.943 buffer_time=0.000 print_stall=0 extruder: target=180 temp=180.6 pwm=0.247
Stats 290488.7: gcodein=0  mcu: mcu_awake=0.011 mcu_task_avg=0.000097 mcu_task_stddev=0.000072 bytes_write=58362 bytes_read=70514 bytes_retransmit=0 bytes_invalid=0 send_seq=3513 receive_seq=3513 retransmit_seq=0 srtt=0.003 rttvar=0.000 rto=0.025 ready_bytes=0 upcoming_bytes=0 freq=16003704 sd_pos=34146 heater_bed: target=60 temp=60.1 pwm=0.246 sysload=0.03 cputime=13.980 memavail=674412 print_time=11710.944 buffer_time=0.000 print_stall=0 extruder: target=180 temp=180.5 pwm=0.247
Stats 290489.7: gcodein=0  mcu: mcu_awake=0.011 mcu_task_avg=0.000097 mcu_task_stddev=0.000072 bytes_write=59880 bytes_read=70739 bytes_retransmit=0 bytes_invalid=0 send_seq=3539 receive_seq=3539 retransmit_seq=0 srtt=0.004 rttvar=0.000 rto=0.025 ready_bytes=37 upcoming_bytes=0 freq=16003704 sd_pos=34641 heater_bed: target=60 temp=60.1 pwm=0.190 sysload=0.03 cputime=14.041 memavail=674412 print_time=11714.646 buffer_time=2.079 print_stall=0 extruder: target=180 temp=180.4 pwm=0.247
Stats 290490.7: gcodein=0  mcu: mcu_awake=0.023 mcu_task_avg=0.000146 mcu_task_stddev=0.000163 bytes_write=60252 bytes_read=70908 bytes_retransmit=0 bytes_invalid=0 send_seq=3548 receive_seq=3548 retransmit_seq=0 srtt=0.003 rttvar=0.001 rto=0.025 ready_bytes=24 upcoming_bytes=0 freq=16003705 sd_pos=34785 heater_bed: target=60 temp=60.1 pwm=0.226 sysload=0.03 cputime=14.083 memavail=674416 print_time=11716.816 buffer_time=3.248 print_stall=0 extruder: target=180 temp=179.9 pwm=0.564
Stats 290491.7: gcodein=0  mcu: mcu_awake=0.023 mcu_task_avg=0.000146 mcu_task_stddev=0.000163 bytes_write=60347 bytes_read=71047 bytes_retransmit=0 bytes_invalid=0 send_seq=3554 receive_seq=3554 retransmit_seq=0 srtt=0.004 rttvar=0.000 rto=0.025 ready_bytes=0 upcoming_bytes=0 freq=16003704 sd_pos=34785 heater_bed: target=60 temp=60.1 pwm=0.377 sysload=0.03 cputime=14.112 memavail=674416 print_time=11716.816 buffer_time=2.246 print_stall=0 extruder: target=180 temp=177.2 pwm=0.978
Stats 290492.7: gcodein=0  mcu: mcu_awake=0.023 mcu_task_avg=0.000146 mcu_task_stddev=0.000163 bytes_write=61001 bytes_read=71202 bytes_retransmit=0 bytes_invalid=0 send_seq=3566 receive_seq=3566 retransmit_seq=0 srtt=0.004 rttvar=0.000 rto=0.025 ready_bytes=42 upcoming_bytes=0 freq=16003705 sd_pos=35156 heater_bed: target=60 temp=60.1 pwm=0.182 sysload=0.03 cputime=14.158 memavail=674416 print_time=11717.587 buffer_time=2.016 print_stall=0 extruder: target=180 temp=175.1 pwm=0.978
Stats 290493.7: gcodein=0  mcu: mcu_awake=0.023 mcu_task_avg=0.000146 mcu_task_stddev=0.000163 bytes_write=61368 bytes_read=71351 bytes_retransmit=0 bytes_invalid=0 send_seq=3575 receive_seq=3574 retransmit_seq=0 srtt=0.004 rttvar=0.000 rto=0.025 ready_bytes=0 upcoming_bytes=0 freq=16003705 sd_pos=35156 heater_bed: target=60 temp=60.2 pwm=0.112 sysload=0.03 cputime=14.196 memavail=674416 print_time=11719.126 buffer_time=2.553 print_stall=0 extruder: target=180 temp=173.1 pwm=0.978
Stats 290494.7: gcodein=0  mcu: mcu_awake=0.023 mcu_task_avg=0.000146 mcu_task_stddev=0.000163 bytes_write=61482 bytes_read=71485 bytes_retransmit=0 bytes_invalid=0 send_seq=3579 receive_seq=3579 retransmit_seq=0 srtt=0.004 rttvar=0.000 rto=0.025 ready_bytes=0 upcoming_bytes=0 freq=16003705 sd_pos=35156 heater_bed: target=60 temp=60.1 pwm=0.210 sysload=0.11 cputime=14.228 memavail=674416 print_time=11719.751 buffer_time=2.177 print_stall=0 extruder: target=180 temp=170.6 pwm=0.978
Stats 290495.7: gcodein=0  mcu: mcu_awake=0.022 mcu_task_avg=0.000162 mcu_task_stddev=0.000168 bytes_write=61605 bytes_read=71615 bytes_retransmit=0 bytes_invalid=0 send_seq=3583 receive_seq=3583 retransmit_seq=0 srtt=0.004 rttvar=0.000 rto=0.025 ready_bytes=0 upcoming_bytes=0 freq=16003704 sd_pos=35156 heater_bed: target=60 temp=60.1 pwm=0.307 sysload=0.11 cputime=14.260 memavail=674416 print_time=11720.584 buffer_time=2.008 print_stall=0 extruder: target=180 temp=169.4 pwm=1.000

The hotend can consistently hold 180c if told to heat and hold manually, so I’m assuming something is being sent to tell it to stop heating.

Does anybody have any ideas on what could be happening here?

Thanks! :slight_smile:

Hello @dyerat !

I can’t find a dedicated start macro in the log.

Please upload the START_GCODE script of your slicer or a gcode file.

I’m using one within prusaslicer, the temps commented out is deliberate since I’m letting prusa emit them

SET_PRINT_STATS_INFO TOTAL_LAYER=[total_layer_count]
G29 ; Auto bed-level (BL-Touch)
G92 E0 ; Reset Extruder
;M140 S60 ; Set Bed Temp
;M104 S{first_layer_temperature[initial_tool]}; Set Extruder temperature
G1 X1.1 Y20 Z0.3 F5000.0 ; Move to start position
;M190 S60 ; Wait for bed temp
;M109 S{first_layer_temperature[initial_tool]}; Wait for Extruder temperature
G1 X1.1 Y180.0 Z0.3 F1500.0 E15 ; Draw the first line
G1 X1.4 Y180.0 Z0.3 F5000.0 ; Move to side a little
G1 X1.4 Y20 Z0.3 F1500.0 E30 ; Draw the second line
G92 E0 ; Reset Extruder
G1 Z2.0 F3000 ; Move Z Axis up little to prevent scratching of Heat Bed

The only temperature setting command with the klippy.log is M109 in the Resume macro.

Are you sure that macro isn’t called during the start process?

Please upload a small gcode file.

Hey again, here is the gcode that I’m trying to print:

gcodes-2024510-18442.zip (1.2 MB)

Also noticed that what is reporting on the graph as a spike to 200c (at the 75% mark on the diagram) isn’t really showing at all in the log, and happens when the PWM is 0

Check your power supply voltage for a drops when your temp drops, if it does then your PS is failing or heater problems.

1 Like

As in my printers PSU or that of the Pi?
If printer, is this something I’m gonna need a probe for?

Multimeter connected to the power supply output. I would advise against a cheap one. It may not react fast enough for you to see the drop.

If you have another printer of the same model, I would check the heater core resistance without it connected to anything but the wires and compare the two printers.