Question Between motors temperature gradient

[VECDESIGN]

Printer Model

VORON 2.4

Extruder Type

Galileo

Cooling Type

Stealthburner

Hi. I am building a 2.4 with MANTA MP8 V2.0 and TMC2240 having the reading of the temperature of the steppers. I have seen that driving the Z motors at the same current there is a gradual change in temperature. I understand the driving current is not properly distributed with some internal V or A drop in between. With X Y motors the same happens but smaller difference since only two motors.
Anyone experienced that and knows the root of the issue?
Belts are properly balanced and I am providing readings with motors in standby.
The actual steppers config as follows:

[stepper_z]
step_pin: PB8
dir_pin: PB7
enable_pin: !PE0
microsteps: 16
rotation_distance: 40
gear_ratio: 80:16
endstop_pin: probe:z_virtual_endstop
position_max: 340
position_min: -5.0
homing_speed: 10
second_homing_speed: 3
homing_retract_dist: 3
#--------------------------------------------------------------------
[tmc2240 stepper_z]
cs_pin: PB9
spi_software_sclk_pin: PG8
spi_software_mosi_pin: PG6
spi_software_miso_pin: PG7
driver_TPFD: 0
run_current: 1.0
interpolate: True
#--------------------------------------------------------------------#
## Z1-axis on MOTOR3(left rear)
[stepper_z1]
step_pin: PB4
dir_pin: !PB3
enable_pin: !PB6
rotation_distance: 40 # Active pulley circumference mm (2GT-20T pulley 40, 2GT-16T pulley 32)
gear_ratio: 80:16 # reduction ratio
microsteps: 16 # microsteps
#--------------------------------------------------------------------
[tmc2240 stepper_z1] # TMC2209
cs_pin: PB5
spi_software_sclk_pin: PG8
spi_software_mosi_pin: PG6
spi_software_miso_pin: PG7
driver_TPFD: 0
run_current: 1.0
interpolate: True

#--------------------------------------------------------------------
## Z2-axis on MOTOR4(right-rear)
[stepper_z2]
step_pin: PG13
dir_pin: PG12
enable_pin: !PG15
rotation_distance: 40 # Active pulley circumference mm (2GT-20T pulley 40, 2GT-16T pulley 32)
gear_ratio: 80:16 # reduction ratio
microsteps: 16 # microsteps
#--------------------------------------------------------------------
[tmc2240 stepper_z2]
cs_pin: PG14
spi_software_sclk_pin: PG8
spi_software_mosi_pin: PG6
spi_software_miso_pin: PG7
driver_TPFD: 0
run_current: 1.0
interpolate: True

#--------------------------------------------------------------------#
## Z3-axis on MOTOR5(right-front)
[stepper_z3]
step_pin: PG9
dir_pin: !PD7
enable_pin: !PG11
rotation_distance: 40 # Active pulley circumference mm (2GT-20T pulley 40, 2GT-16T pulley 32)
gear_ratio: 80:16 # reduction ratio
microsteps: 16 # microsteps
#--------------------------------------------------------------------
[tmc2240 stepper_z3]
cs_pin: PG10
spi_software_sclk_pin: PG8
spi_software_mosi_pin: PG6
spi_software_miso_pin: PG7
driver_TPFD: 0
run_current: 1.0
interpolate: True

Thanks so much.

 

[NoGuru]

Some things I can think of is Z3 is getting some fan wind and same with Z2 but less flow.
Z and Z1 might have longer wires and more resistance.

 

[VECDESIGN]

Thanks for your reply. It was the first thing I thought but it is not the case.
The temperatures are not really for the motors but for the drivers. I was confused because they name as motor temperature.
There must be some issue with the power distribution in the board. I asked BTT to investigate that and they are working on it.
As a content solution I have added active fan cooling with oversized flow. I will keep you posted with the final conclusions, I hope I can get them.

 

[NoGuru]

Ahh yes, the 2240's are the driver temps. One thing you may want to do is add some active cooling right across the drivers.
I have something like this model but not this one specific to help when I run higher current https://www.printables.com/model/676837-btt-octopus-stepper-driver-40mm-cooling-duct

 

[VECDESIGN]

Thanks, For the cooling I just fixed, as a content action, with the next cooling duct and extra fan which is easily fixed to the VORON 2.4 DIN rails and aligned with the drivers heat-sink. I HOPE IT HELPS SOMEONE ELSE or even with other drivers. 3D CAD attached.