ZeroG Mercury One.1 modified stepper assemblies

Warning!

If you use these parts, you will need the rest of the mods that go with it, you will change the geometry of your printer motion system and you will need to make sure that the edges of the bed, the end stops, the belt tension, and everything else is double checked. I am not responsible for any damages to your printer, or any of the parts. If you don't know how to do this, this mod may not be for you!

Using this mod, and all the mods that go with it will also flip the X axis so the linear rail will now be forward, instead of on top. This is also in line with the Voron line of printers, for instance, but different from the original ZeroG Mercury One design. So you will need to select another toolhead and X carriage mount for that toolhead. There will be recommendations further in these instructions.

Introduction

My very first 'serious' (-ish) printer was a Sovol SV05 which soon after I purchased it, was upgraded to a ZeroG Mercury One. Absolute mad props to the ZeroG team, it was a huge improvement over the original. Then I enclosed it using my own design. At that time the ZeroG Nebula enclosure was rumoured, but not yet made public, so I simply designed what I thought made sense. Funny enough, my enclosure and the Nebula are similar, but NOT the same. Keep this in mind if you have a Nebula enclosure and want to use my mods. Later I added ZeroG Hydra as well.

As I used this quite heavily modded printer regularly I started to have some wishes, and ran into some issues:

• I wanted to use a similar toolhead as I had on my Vorons, ideally the same (the one I use is the Dragonburner). This assumes the linear rail is at the front though.

• I wanted to use a Cartographer sensor. That also puts demands on the carriage, which are easily addressed with commonly available carriages for the Dragon Burner. The one I use both on my Voron 2.4 and on the Merc now can be found at chirpy2605's 'alternative voron mounts' github.

• My belts had a habit of riding up and down the bearing stacks of the stepper mounts. This caused excessive wear. This was partly due to 'builder fault' (ie: me being a dunce), but even when I was 100% sure things were assembled perfectly, they kept moving all over the place.

• I suspected the front idler mounts were bending towards the rear of the printer due to belt tension and the torque of the steppers. In the original design, the front idler mounts are only attached with a single M5 bolt.

• I suspected the stepper mounts, in turn, were being bent forward, because they are only attached to the frame with 2 M5 bolts, nearly in a straight line left-to-right, so with very little resistance to any force perpendicular to that.

• I wanted to have a bit more travel for the front idlers to tension the belts. Though you shouldn't need all that much if you do your belts right, I am a bit lazy, so... more is better ;)

Looking at the Voron 2.4 that sits right next to my Mercury I quickly realized that it did not suffer from the issues, and already had the attributes I was looking for. So, I basically wanted to 'Voron-ize' my Mercury One! The models here only cover the stepper mounts. You will need the other parts in the set too for a fully functioning set.

Suitability and fit

This mod assumes there is a frame outside of the original 'Ender 5' style frame, and that the extrusion that sat in the front, left to right, at the top, is removed. As you can see in the photo, besides being fastened to the Y extrusion, it is also screwed into the 2040 extrusion (vertically) and into the frame to the side, horizontally.

The added third mounting point for the Y extrusion will stick out 75mm to the rear of the printer, beyond the left to right extrusion it will be bolted to. On a non-enclosed Mercury you will have that space, but no extrusion to mount it to since the extrusions stop square with the left-to-right extrusions in the rear, so the Y extrusion won't stick out. If you do have a Nebula enclosure (or home-brew, like mine), make sure you have enough space for the stepper mount. So the stepper mount should generally fit on a non-enclosed Merc, but you will have to double check if it fits on a Nebula or otherwise enclosed Merc.

Inspiration

These stepper mounts are a direct mod of the standard ZeroG Mercury One.1 stepper mounts.

Disclaimer

Another one?! Yes, another one. The solution I came up with for modifying the 'running gear' is by using the Voron layout of bearing stacks: washer-bearing-bearing-washer. With the right bearings, this means that there is a 6mm track between the flanges of the bearings that the GT2 belt sits in. The manufacturer of the GT2 belts, Gates, says that should be 7mm. The Voron team went with 6. The ZeroG team decided to go with the manufacturers recommendation. I would generally agree with the ZeroG team and the manufacturer, they should know best. But I also know there are thousands of Vorons out there with that same bearing stack layout, functioning just fine. So.... YMMV. If you don't feel comfortable with this..... This is not the mod for you!

Also, if you adopt one of the components of my mods, you will either need to use all of them, or design or find the other parts to complete the whole set, to suit the same belt spacing.

Bill of materials

• Dowel, ø5x30mm, 4x

• Washer, M5x1x10, 4x (outer diameter can actually be between 7 and 12mm or so)

• F965 bearing, 4x

• SHCS M5x50, 6x

• SHCS M3x20, 6x

• M5 Slide in, hammer nut, or anything similar, 6x

Printing

You will need all to print all parts. The for the left are different from the right, not just mirrored Use the default print settings recommended by the ZeroG team. Use decent quality ABS or ASA. It is not recommended to use filaments with any kinds of fillers (glass or carbon fiber) since the layer adhesion is usually much worse than without, and may cause the parts to fail. White filament is also often (but probably not always) weaker. YMMV, blah, the usual caveats. PETG and PLA are not heat resistant enough and will fail.

Print the stepper mount parts 'on their back'. No supports needed.

Assembly

Print as directed above. The assembly is exactly the same as for the standard stepper mounts, except where the ZeroG instructions tell you to insert a washer in between the two bearings (washer-bearing-washer-bearing-washer), you skip the one in the middle (so washer-bearing-bearing-washer instead). See the drawings for how they should be.

Also note that you will have to adjust the position of the GT2 pulleys on the stepper motors slightly. I did not create a tool for this, you will have to 'eyeball' it. The positive side is that due to the narrower 'channel' that the belt will sit in, you now have 2mm play instead of just 1mm. But also note that while you have more clearance to play with, the actual placement is more critical! Make sure you get the actual height correct to avoid wear on the belt!

The other parts you need

You will also need:

• My modified XY carriages for ZeroG Mercury One.1 with Voron belt spacing.

• My modified front idlers for ZeroG Mercury One.1 with Voron belt spacing.

Versioning

• 2026-09-30. No change to model (yet). Added remark about criticality of the actual placement of the pulley on the motor to avoid wear on the belt due to belt creep.