Precise Z-Axis Endstop mechanism for optical sensor

Description

Primarily designed for my old-school MendelMax frame, but it will work on any other 3D printer that has an 8mm steel rod on the Z-Axis.

Prerequisites

You need an LM8UU bearing, a 5mm hexagonal head screw, a 5mm nut, and a spring to fit the 8mm steel rod or one to fit on the 5mm screw.

Goals

Precision – the sole role of the plastic parts is to connect the metal parts, which makes it both durable and precise.

Consistency – It takes advantage of the properties a linear bearing like LM8UU has to glide precisely on the Z-Axis and to remain in the same position relative to the printing bed, each time, between prints.

Adjustable – The 5mm screw elevates the bearing with 1mm per revolution. You can easily adjust the distance with 0.1 mm precision by turning the knob 36 degrees.

Configurable – The part that drives the bearing connects with the optical sensor via a small part, called Delimiter. This part is useful to configure the bearing part to be closer or farther away from the sensor. Useful if you have a taller extruder (with Volcano nozzle for example) or if you just want to use a shorter 5mm screw.

How to build it?

Print it with a 0.4mm nozzle and 0.25 layer height. Use 40% or 50% infill to and 3 wall line count to ensure durability of the parts.

Regarding the material, PETG is recommended to be used, but PLA should also work.

If the metal parts don’t fit right away, don’ panic. Make sure you clean the holes with a paper-knife or screwdriver and if they still don’t work, heat up the metal parts before inserting them into the plastic parts.