Ender 3D Pro extruder stepper motor shaft length

Question

My stock extruder motor feed mechanism had started to shave the filament but not feed correctly. I order a REDREX Tech dual gear all-metal extruder to fix the problem. I ordered a hobby gear puller, removed the press-fit brass gear, and now have yet another problem. The shaft on the Ender 3D Pro is not long enough on the stepper motor to ensure the grub screw engages at the proper height with the idler gear. I'm anticipating having to shave a flat spot on the shaft (with a Dremel Tool) to ensure the grub screw does not hinder the 360-degree rotation of either of the two gears but now need to know how to order a motor with a shaft long enough to do this.

The literature that accompanied the REDREX Tech showed a 22 mm shaft height. I checked this with my digital micrometer and found I only have 13.5 mm of the shaft on this Creality-provided OEM stepper motor. So how or where may I order a replacement stepper motor with the shaft longer by about 10-12 mm? Does the stepper motor 42-40 need to be a 42-50 where the second set of digits is the required extra 10 mm length of the shaft?

Answer 1

Steppers are sized by the dedicated standards, for a NEMA 17 stepper (most frequently used in 3D printers) the width and depth are 42 mm. This is the 42 from the designated naming found by Creality steppers (42-40, 42-50, 42-60, etc.).

The second set of digits in the naming relates to the stepper body height (in the image below, this is the L dimension), not the overall height! The shaft has its own dimensions, usually these are about 22 mm, but Creality has ordered custom made steppers with shorter shafts with press fitted filament extruder gears (see Problems with stock gear with no screw on Ender 3 pro).

Does the stepper motor 42-40 need to be a 42-50 where the second set of digits is the required extra 10 mm length of the shaft?

No, the second set of digits doesn't relate to the overall height of the stepper.

Do note that the naming is short for the model number which is usually much longer, e.g. JK42HS40-1004AC-01F, you see the width/depth and length back in the model name. Note that generally speaking, larger length steppers create more torque, the longer the motor the higher the torque (exceptions apply when different gauge wiring in the stepper is used).

The following image gives an overview of the steppers used by Creality models. As can be seen, they do not always use the typical D-shaft steppers, but also steppers with round shafts, this makes it more difficult to attach pulleys with grub screw without creating a flat spot on the shaft. Note that double shafts means that there is a shaft on both sides of the stepper motor, this is convenient for attaching a knob for manual positioning.