Ender 3 dual Z axis carriage , adjustable for antibacklash nut

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Ender 3 is great machine with some shortcomings. One of these is too fragile X axis gantry supported only by one Z screw. Adding second screw was logical step.

But I wanted more precision from whole Z assembly so I went for complete rebuild of way z nut and screw is adjusted. So here begins my journey. Both brackets are working fine. I will use also things from other users, with reference.

Please remember: this is not project for beginner, as you want to add precision to your printer it requires precision and patience from you. Feel free to ask for details or advice.

So mine goal is:

• dual Z axis
• using antibacklash nuts
• dual Z motor
• better motor mounts
• bearing support for Z axis
• synchronising belt for additional precision
• fully adjustable in all axis to achieve really straight path for Z nut/screw

Where am I now:
**for my notes and part list scroll down

Step 1: One ( yet another) new bracket for second Z axis designed by myself to allow adjust Z nut in such way that Z screw will be absolutely vertical. To help that I used motor mount from OneEyedDesign ( https://www.thingiverse.com/thing:2932344)
Added also bracket for stock nut ( not only antibacklash)

Step 2: same as right side rebuild on extruder side ( left), design without extruder finished, here is left side without extruder mount , for direct drive setup (https://www.thingiverse.com/thing:4188950)

Step 3: top adjustable bearing blocks for Z screws - done (https://www.thingiverse.com/thing:4214242)

Step 4: cable management adaptors ... waiting

#Hardware and assembling

For X axis bracket you will need this hardware:

• leadscrew 8mm diameter, 2mm pitch, 8mm lead ( stock screw) 370 mm length
• nut - right now it is designed only for common springloaded antibacklash nut, but this is easily changeable
• M5 x 40mm ( or longer) - 3 pieces
• two spacers 8mm outer diameter, length 8mm, hole 5mm
  ( this is not so common so it can be printed but i replaced one with two M5 nuts and one standard M5 spacer - see on last photo)
• two or six M5 nuts
• one small and one bigger spacer wit 5mm hole
• two screws M4x12mm,
• two M4 nuts

#NOTES

Leadscrew
you can use also different lead but you need change both screws and nuts. Actually my next step is changing screw to 2mm lead as it allows me to have one step at 0.01mm instad of stock 0.04mm. This is nice to have feature as you don't need to stick to 0.04 layer step on stock Ender and it is more precise
I strongly suggest you use solid coupler for attaching to motor.

Nut
nut is story itself. Stock nut is just terrible. Very short, with lot of wobbling with very fast wearing of. So on the market are so called Anti-backlash nuts. These are better and actually well made but they are only bad patch on bad solution. Their springs (when mounted in right direction) can really help but their spring constantly push against thread ( so they work) and this can really shorten theirs life. So my next step will be proper solution as seen on "big machines" with adjustable anti backlash nut without spring.

Motor
use same stepper motor as is used for main Z axis : 34mm length , 1.8deg. stepper motor.
I recommend to use board with dedicated driver for dual Z as SKR1.3 or newer because with help of Marlin 2.+ and any ABL ( automatic bed leveling any probe) you can safely adjust both sides of X axis with every homming independently , and by that effectively "traming" your printer, what from my POV is just great.
And don't forget to disable stealthchop for Z axis steppers. It helps with more precise, synchronised movement.

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