Z Endstop for Elegoo Neptune 4 and 4 Pro

I created this Z endstop for my Neptune 4 Pro. This should be compatible with the non-pro, however, due to the nonexistent off-bed range of the X axis on the Plus and Max a different solution will need to be designed.

Limitations

• If the nozzle is dirty, your offset is not going to be accurate.
• It may be difficult to clean the nozzle without homing first.
• You cannot use bed corners on the same side as the offset endstop.

Additional Parts

• Cable Endstop Mechanical Limit Optical Switch Connection Wire 
  Note: 1M is too long, if you can find even a third of that length it would work.
• X/Y/Z Axis End Stop Limit Switch
• 4x15mm Dowel Pins
• 0406 Sleeve Bearings
• 2 - M3*6 button head screws
• 1 - M4*20 hex head bolt with nut (poor man's t-nut)

Installation Pictures

The -Z pin PC3  

I had to remove the top and both of the bottom panels to route the wire through, but there is plenty of clearance.  

There is a clearance issue that needs to be resolved. In my case, there is no pressure from the arm so the rubbing is minimal.

On and Off the Plate

• 0.2 layer height
• Any filament is OK
• Brim Type: Mouse ear
• I used supports: Normal with Snug   
• Yes, the cover is upside down.

Assembly

I hope you can visualize how the parts come together by looking at the picture.
 

I would place the dowel pin in last as it could mess with the switch arm while tightening the cover.
 

Right Side

Left

The arm spacer removes any question of where the dowel should reside in relation to the nozzle along the Y axis. If for some reason your nozzle tip is not landing near the center along the Y axis you can scale this part accordingly in Orca (probably take +-0.5mm)

The same goes for the base plate (the one without the keepers). However, I would not make it any thinner as the rear of the arm will run into the stepper mount. If you go thicker keep in mind how much clearance you have between the bearing and the build plate.

How the switch is positioned

When you depress the dowel pin, do it slowly. Do not bottom it out. You will hear the switch ‘click’ which is where the tool head will stop, so you should too. The motion should be smooth and not wiggle. The dowel should return as easily as you depressed it. If there is friction check the surfaces of the bearing and the dowel, maybe add a pin tip of grease (I did not find this necessary).

G-Code

When reading this configs keep in mind that the Pro has a bed size of 235x235 so the center would be 117.5,117.5. 

We need to tell the z stepper which mainboard pin PC3 we are using for the endstop note the ^ and !. This is not the place to break speed records for the fastest homing, 8/5/3 are “nice”.

[stepper_z]
...
endstop_pin: ^!PC3
homing_speed: 8
homing_retract_dist: 5
second_homing_speed: 3

Note how my X is -5. The X endstop should be at -8.

[safe_z_home]
...
home_xy_position: -5,117.5

I discovered that I needed this parameter by reading the comments in one of the videos. I was getting wildly inconsistent offsets without it.

[bed_mesh]
...
zero_reference_position: 117.5,117.5

This macro is not required. I use this tool if I ever need to recalibrate where the endstop is located. Once it's dialed in, leave it.

[gcode_macro Z_ENDSTOP_CALIBRATE]
rename_existing: Z_ENDSTOP_CALIBRATE_RAW
gcode: 
  BED_MESH_CLEAR
  G28
  G90 # Abs positioning
  G1 X117.5 Y117.5 F6000  
  Z_ENDSTOP_CALIBRATE_RAW {rawparams}

Homing

One of my first videos of this in action from Nov 2, 2024. A week into using v0.1 (the prototype) 

References

I highly recommend watching and reading these. You need to understand how Klipper is going to work its magic.

• https://www.youtube.com/watch?v=Q2uBK5XzX4I Note: this video fails to mention what the zero_reference_position does.
• https://www.klipper3d.org/G-Codes.html?h=z_offset_app#z_endstop_calibrate
• https://www.klipper3d.org/G-Codes.html?h=z_offset_app#z_offset_apply_endstop
• https://www.klipper3d.org/Endstop_Phase.html
• https://www.klipper3d.org/Bed_Mesh.html?h=zero_reference_position#configuring-the-zero-reference-position

Some Questions You Might Have…

Q: Why measure from the nozzle and not the arm or other easier to get at location?
A: I have about 3 nozzles I like to use for different functions. They all are slightly different heights. If I measured from the arm or another static location then I would need to recalibrate the offset when I change the nozzle because the overall height has changed. The nozzle is the variable part here. This way the measurement is always from the “tip of the nozzle” and the “top of the bed”

Q: Hot or cold?
A: As per the docs always calibrate your z with a cold bed and nozzle. This is different from screw twist which is done hot.

Q: Paper or feeler?
A: I use a 0.1mm feeler now, but if you like paper go for it.

Q: Do you adjust for the first layer squish?
A: I only did this once and I haven't needed to adjust it since. Prior to this modification I used to run through the setting the squish every time I changed the type of filament, but I haven't needed to mess with it for some time now. YMMV.

Q: Why not use a T-bolt?
A: I am lazy. I don't want to mess with removing my gantry. One day I may.

Q: In your pictures, you have a different color mounted, is it special?
A: It's the proto-type. Version 0.1. I don't feel the need to swap it out.

Q: You Eddy? I Eddy! Which config should I use?
A: I no longer use the BTT Eddy as an endstop. I do use it for my bed meshing. As for which config I use, it's the sample-bigtreetech-eddy.cfg