I wanted to know if a 3D printed gear can hold more torque than a Nema 23 stepper and which gear design and material is suitable.
So I designed this destructive test to get some understanding.

Here you can see my tests: https://youtu.be/Ik0hf_iBz6g

For me it was enough to know that the PLA and PETG gear I wanted to use can handle 9 to 12Nm of torque which is 4 to 6 times the holding torque of the strongest Nema 23 stepper I can find(2Nm). So if torque exeeds I will loose steps but not damage my gear (at least for static loads).

By the way I decided to use PETG beacuase it can handle the torque and I expect a better perfomance than PLA if friction increases the temperature.

Surprisingly the ABS Version failed quite early. I assume this is a bad quality ABS.

If you whant to test it by yourself you need:

• a hanging scale (>20kg)
• some strings
• 3x M5x50 (recomeneded DIN 603carriage bolt)
• 3x M5 nuts
• a camera

To calculate the torque:
t=0.1m weight on the scale 9.81N/kg*cos(angle of the lever relative to the ground)

The "angle of the lever relative to the ground" is a small correction. I measured it based on the camera Images. Not very accurate but the influence is only around 10% and I needed just a order of magnitude.

You can use each sample for 2 tests and don't forget to post the results as a make or comment.

Paramters of the gear:

• double helical gear
• module 1mm
• teeth 18
• pitch diameter 20.785mm
• thickness 15mm (2x7.5mm)
• designed in fusion 360 helical gear tool

Material:
PLA white Hobbyking
PETG bronze Das Filament
ABS blue Hobbyking