ZeroG Hydra Add-On

[neon girder]

Finally it’s time for step 2/3, upgrading the stock dual Z to Hydra

Current situation:

• Fabreeko MIC6 bed on the stock Z-Frame
• BTT SKR Mini main MCU
• Raspberry Pi 3B+
• BTT U2C CAN bus for the toolhead
• EBB42 toolhead board on CAN bus
• Cartographer EDM scanner on CAN bus

[lofty solar]

what is step 3/3?

[neon girder]

Buying a Bambulab 😂

[neon girder]

Enclosure

[lofty solar]

ah thats what I though

is that the ender 5 plus

[neon girder]

Yes

[lofty solar]

oh nice if you need help with the hydra settings just say I have mine ready

I have to say one thing your gonna be happy that you never have to do screw tilt adjust anymore

[neon girder]

Step 1, Sourcing
Because I have a CAN bus already and the SKR Mini doesnt have enough stepper drivers, I decided to buy a cheap ERCF board which connects to CAN and gives me 4 additional stepper drivers for 30 €

BTT MMB CAN
https://aliexpress.com/item/1005005969840733.html
FYSETC Hydra Kit
https://aliexpress.com/item/1005007530725071.html
Lead Screws T8x2
https://aliexpress.com/item/1005002027934606.html
MGN12H Linear Rails
https://aliexpress.com/item/1005006184354973.html

Printed all parts in ASA

It always takes longer than anticipated but I finally have all parts ready to go

Step 2, Disassembly
First, learn from painful 🌩️ mistakes and unplug the power 👀

removed bed first, then braces and electronic covers, then the rest of the z-assembly. Shedding way more stuff than anticipated 😃

[lofty solar]

what bed are you going to use?

[neon girder]

I had a 377x370 MIC6 bed already on the stock Z movement

[lofty solar]

oo I thought that was the stock

[neon girder]

good point, I need to heat it up to remove the screws under the magnetic sheet

reminder to myself, we're plugged in again 😄

My assistants

[lofty solar]

lol he is already a printer fan

[neon girder]

Maybe you can help me. How exactly does the bed plate connect to the mini tanks? Do I have to turn it around?

[lofty solar]

no

I have it like this

[neon girder]

That’s those + a m5 screw?

[lofty solar]

let me look

I'm not sure its m5 or m4

[neon girder]

ok but how do the screws hold the bed? there are no threads in this zylinders or the bed plate itself

[neon girder]

I'll launch Fusion and check the model, I hope I have all parts. For some reason I never throught about this detail

[regal marlin]

Screws into the kossel ball no?

[lofty solar]

the screw goes inside the kossel ball

[neon girder]

yeah makes sense - and the cylinder creates some space for maneuvering

thanks ❤️

[lofty solar]

yep but but lock the kossel ball when screw in the bed or else the kossel will turn

when is your bed is screwed in loosened this screw this screw also locks the kossel ball

[neon girder]

magnetic foil really doesnt like to be bent at all, even when heated to 120 degrees

[lofty solar]

thats why I made holes in my magnet

[neon girder]

I have to remove the screws for the stock frame, they are deeper inside :/

[neon girder]

**Step 3, assembling the center axis. **

Used centering blocks from the merc build and prepared + fastened the linear rail the same way. Only 8 M3 roll-in nuts per 500mm rail, it's less than on the Y-Axis but I guess that's enough.
used O - X X - O pattern which of course ended up non-symmetrical, my OCD forced me to move all so it's O X X O XX O XX O X O XX O XX O XX O, symmetry is king ^^

I didn't fasten the extrusion all the way yet, will do once I know the exact position I need (center I guess?)

To be honest, I am pretty sure that 450mm rail would have been completely sufficient to have the full range of motion that makes sense - will report once I am done with the build

[neon girder]

I decided to use the springy motor couplers because the motors are now mounted to printed parts and having them perfectly aligned vertically will be unlikely.

@thin anvil pointed me at the ball bearing hack which I've ordered 7mm ball bearings (https://aliexpress.com/item/1005005656499702.html) for.

#hydra-chat message

https://www.youtube.com/watch?v=zn7iMHKw0Z0&t=159s

When removing the screws under the magnetic foil for the mic6 bed, I basically ruined the foil, its pretty brittle. Found a similar foil here (German store) https://princore.de/products/magnetplatte

[neon girder]

Oh come on. I hate gravity

[regal marlin]

https://tenor.com/view/yes-no-gif-18692714

[neon girder]

life gave me gravity, but also magnetism 😄

[neon girder]

I've powered through and just made pics on the way, will share them once I'm through the canbus config

with some remarks. holy moly I need to clean up my electronics box 😄

[neon girder]

Bigtreetech MMB sample config https://github.com/bigtreetech/MMB/blob/master/Firmware/sample-bigtreetech-mmb-canbus.cfg

[neon girder]

Some things I've learned along the way:

1. The frame becomes a bit less stable without the stock Z-rods and when you want to have the hydra covers for the electronics box, there's also no way to attach braces to the bottom.

Designed a chain guide for the Hydra chain and this adds a lot of stability, too

2. 450mm linear rails are perfectly sufficient to have the full range of Z-motion on an Ender 5 plus, I am a bit annoyed by this because the extra 50mm cost way more,

I had a similar outcome with the 6m required belt length for the mercury where I had to spent twice the amount to get the extra 1m and in the end it actually only requires less than 5 meters of belt

3. Perform a 4-point Z-tilt adjustment, even if it seems logical to measure only over the tilt points.

On a large bed, even when the front left-to-right axis falls within spec (e.g., 0.05mm tolerance), the back left-to-right axis might be out of spec. Measuring and adjusting at all four edges ensures greater overall precision.

I've been working on optimizing bed leveling for Hydra, but so far, both my custom plugin and Klipper's stock leveling achieve the same result within the same number of iterations (2 rescans to reach a tolerance of ±0.025 mm). One more idea I had was to use a bed mesh scan from a fast Eddy probe to align the imperfect bed surface to a plane that minimizes the required mesh adjustments during printing.

I've added 7mm steel balls that sit below the lead screws in the coupling to allow horizontal but not vertical motion.
I am considering to add thrust bearings which remove the weight of the bed from the small 34mm motors, I've re-used the stock Z-motors

[regal marlin]

Yeah I've been thinking of doing the same, using thrust bearings to relieve the motors