Mini scara printer

This is a mini SCARA printer. From the first tests I have verified that the printer works but that it is not suitable for normal use because it has poor accuracy, it is only suitable for demonstration purposes on the functioning of SCARA printers.
The project is made to be as cheap as possible. The 28byj-48 ministeppers were used because they have a large number of steps per turn (2037.8864 steps/turn) so it is possible to avoid reducers.
It is necessary to modify the 28byj-48 steppers from unipolar to bipolar, see attached photo.
The X and Y axes must be set at 16 microsteps while the Z axis at fullsteps. Therefore, if you use the A4988 drivers, jumpers MS1, MS2 and MS3 must be placed in the X and Y axes, while jumpers must not be placed in the Z axis.
The 28byj-48 5V steppers must be driven with a current of 0.11A, since on each axis there are two connected in parallel, the drivers must supply a current of 0.22A. If you are using A4988 drivers with Rsense of 0.1ohm (they are the