Precision translation axis for modular 3rd hand system

I recently published a modular holder system working as a very versatile 3rd hand for any delicate task you may encounter: https://youtu.be/XsCk5LUepSI , https://www.thingiverse.com/thing:7329310

Here, you can find the files for a precision translation element. My modular holder uses 8mm tubes as the main mechanical part. This elements attaches to 3 tubes and allows to move the 3rd one with high precision.

The spacing of the fixation tubes for this design makes it compatible only with the round 16cm and the square 14cm baseplate.

The element is composed of an outer cage, designed to attach to 8mm tubes in various configurations, an inner element to translated inside the cage and attach to the mobile 8mm tube and various knobs.
Besides the printed parts, it uses 2x 80mm long, 3mm diameter metal rods as "sledges" to prevent the high friction liked with plastic on plastic contact, a 80mm long M4 screw to drive the axis and a 50mm long, 7mm outer diameter spring.
All the fixations are