Parts

• 1x Dual Z plate sold by Two Six Engineering (https://twosixengineering.com/gtr-shop/ols/products/ender-5-dual-z-axis)
• 2x endstops sold by TriangleLab (https://www.aliexpress.com/item/32852113543.html), the wires provided should be long enough
• Upgraded board – Instruction provided will be for RepRapFirmware 3 on an SKR1.3
• 4x M3 T-nuts
• 8x M3x8mm

How to install RepRapFirmware 3

• LPC1768/1769 boards (SKR1.3, 1.4, 1.4 Turbo): https://reprap.org/forum/read.php?147,874661
• STM32F4 boards (SKR Pro 1.1, 1.2 or GTR v1.0): https://reprap.org/forum/read.php?147,876357

Note: I have also a BL Touch but it works very well without.

Files to print:

• 2x optical support v3.stl - Support for the optical Endstop
• 2x Ender 5 - Endstop trigger v1 15mm.stl - Parts to trigger the optical endstop 15mm should be the one you need but I included a shorter one just in case
• 1x Ender 5 - Dual Z cable relieve v4.stl – prevent to damage the soldered connections on the heated bed.
  The endstop triggers can be glued directly on the plate as there is no contact or constraint applied on them.

Wiring

• Back stepper motor connected on Driver 2
• Front stepper motor connected on Driver 4
• Extruder connected on Driver 3
• Back Optical Endstop connected on Z Stop Max
• Front Optical Endstop connected on X Stop Min
• Optional: BL Touch connected on Z Stop Min

RepRapFirmware 3 modifications

M569 P2 S1 ; physical drive 2
M569 P3 S0 ; physical drive 3
M569 P4 S1 ; physical drive 4
S0/S1 is a parameter used to reverse the stepper motor if needed.

The Z axis needs to be split in Z and U for homing purpose

M584 X0 Y1 Z2:4 U:4 E3 P3

Driver U must be added in M92, M566, M203, M201 and M906 (same values as Z), this is what I used on my Ender 5:

M350 X16 Y16 Z16 E16 I1 ; configure microstepping with interpolation
M92 X80.00 Y80.00 Z800.00 U800.00 E92.6 ; set steps per mm
M566 X900.00 Y900.00 Z12.00 U12.00 E120.00 ; set maximum instantaneous speed changes (mm/min)
M203 X6000.00 Y6000.00 Z180.00 U180.00 E1200.00 ; set maximum speeds (mm/min)
M201 X500.00 Y500.00 Z20.00 U20.00 E250.00 ; set accelerations (mm/s^2)
M906 X800 Y800 Z1200 U1200 E800 I30 ; set motor currents (mA) and motor idle factor in per cent
You MUST used values that are correct for your Ender 5, for example I have .9degree stepper motor on Z et U which means the step are doubled and the currents must be higher.

Endstops for the Dual Z

M574 Z1 S1 P"zstopmax" ; configure active-high endstop for low end on Z via pin zstop
M574 U1 S1 P"xstop" ; configure active-high endstop for low end on Z via pin zstop

Optional - BL Touch – Example, must be adjusted specifically for your printer

M950 S0 C"servo0" ; create servo pin 0 for BLTouch
M558 P9 C"^zstop" H5 F120 T6000 ; set Z probe type to bltouch and the dive height + speeds
G31 P500 X-38.2 Y-12.35 Z1.35 ; set Z probe trigger value, offset and trigger height
M557 X30:190 Y30:190 S20 ; define mesh grid

Example of files used for homing – These files may need to be adjusted for your printer

homez.g

; homez.g
; called to home the Z axis
M913 X100 Y100 Z100
; split Z motor control to Z and U
; for it to work we have to show U (param P4) in the UI
M584 Z2 U4 P4
; Move Z and U down until the switches triggers
G1 H1 Z-405 U-405 F1500
; back to combined axes and hidden U
M584 Z2:4 P3
G1 Z10 F3000
; Back to absolute positioning
G90

homeall.g

; homeall.g
; called to home all axes
M913 X100 Y100 Z100
G91 ; relative positioning
G1 H2 Z5 F6000 ; lift Z relative to current position
G1 H1 X235 Y235 F1800 ; move quickly to X and Y axis endstops and stop there (first pass)
G1 H2 X-5 Y-5 F6000 ; go back a few mm
G1 H1 X235 Y235 F360 ; move slowly to X and Y axis endstops once more (second pass)
G90 ; absolute positioning

; split Z motor control to Z and U
; for it to work we have to show U (param P4) in the UI
M584 Z2 U4 P4
; Move Z and U down until the switches triggers
G1 H1 Z-405 U-405 F1500

; back to combined axes and hidden U
M584 Z2:4 P3
G92 Z7
G1 Z10 F3000

; Back to absolute positioning
G90
G1 X100 Y100 F6000 ; go to first bed probe point and home Z
G30 ; home Z by probing the bed
; Uncomment the following lines to lift Z after probing
;G91 ; relative positioning
;G1 Z5 F100 ; lift Z relative to current position
;G90 ; absolute positioning