X axis belt shim to correct the belt path and improve accuracy for ELEGOO Neptune 2

This is an X-axis belt shim for ELEGOO Neptune 2 series 3D printers.
It makes the X belt parallel to the X axis (gantry) and equalizes the nozzle travel scale over the all position on the axis.
Therefore, the accuracy of the printing is improved.

Installing

You can print two shims and install on the toolhead, one is stepper side clamp the other is idler side clamp, under the gantry.

Stepper side	Idler side

The theory

If the belt is NOT parallel to the axis: ⊿Xin ≠ ⊿X1 and ⊿X2 < ⊿X1.
Therefore, the nozzle travel scale is changed related to the position on the axis.

Correct belt parallel to the axis: ⊿Xin = ⊿X3 and ⊿X4 = ⊿X3.
Therefore, the nozzle travel scale is equalized to all positions on the axis.

Neptune 2 series stock belt path

The stock X belt path of ELEGOO Neptune 2 series is NOT parallel to the X axis.

At left end of the gantry, belt inside the gantry	At left clamp on the toolhead, belt outside the gantry

Correcting belt path of Neptune 2 series

It is 5mm off at the stepper side and is 3.8mm off at the idler side.

CAD file

You can find the cad file on the project GitHub repository.