Help! Ender 3 Resume print after changing filament WAY off.

[Roberts_Clif]

This is one of the reasons when changing form the original, 1.25mm X 8mm all-thread lead screw decided on a T8-2 lead screw.
The lead screws were turning simply because of vibrations, this would have been alright if they turned at the same rate.
But this was not the case they would turn at different rates making the Z-Axis off calibration every time I wanted to Print.

The T8-2 lead screw will not easily move when doing simple filament changes.

To Start I was having problems with the Z-Axis Dual Stepper motors, seemed they needed Z-Axis calibration every print.
The Lead screws on 2nd Printer were T8-8 Trapezoidal lead screws, doing some research discovered that they make several Trapezoidal lead screws. 2mm pitch, 4mm pitch an a 8mm pitch Trapezoidal lead screws. Started with a simple test of gravity shown in the video.

T8-8 Lead-screw Will Drop with Gravity



This was when the decision was made to use the 2 mm pitch lead-screws shown below is a photo. The Lead-screw nuts are turned exactly one revolution.

Lead Screws.jpg

I have not experienced the T8-2 dual stepper lead-screws being out of calibration, or changing positions during filaments changes.
This changed my Z-Axis from 400 steps per unit to 1600 steps per unit in Marlin's Configuration.h

#define DEFAULT_AXIS_STEPS_PER_UNIT { 80, 80, 1600, 94.4962144 }