Sovol Zero Oldham Flange Bearing Block

Fair Warning! This mod is not plug and play. It involves sourcing multiple parts, having additional standard hardware, partially disassembling your printer (a not insignificant amount of disassembling at that), and and either drilling two holes in the aluminum extrusion supporting the Z linear rails or disassembling the printer even further to use slide in t nuts. Only attempt if you are having z banding quality issues related to a bent lead screw and Sovol is unwilling to address those issues by sending you repair parts or if their fixes still fail to deliver your expected level of quality.

So why go through all this on a 152mm printer? Well, I had significant Z Banding issues with my Sovol Zero. After going back and forth with support, we fixed some issue related to a missing spacer and some washers/bolts at the lead screw pulleys, but the Z Banding wasn't improved enough for me and they weren't willing to send me a replacement leadscrew for the one I claimed was bent.

I printed the published latest version using an earlier prototype and you can see how much even the prototype cleaned up the z banding. 

On to what you need to know to do this yourself.

Parts:

2 sets of Oldhams (https://www.amazon.com/dp/B0BQMWC1VG) Make sure they're the type with the flat sides and not full circles.

2x MF128-2RS Flanged Bearings (https://www.amazon.com/dp/B085DCRSWY)

Optional: I replaced the plastic pom nuts that came with the printer with just the pom nuts from these: (https://www.amazon.com/dp/B092ZMRMNF). These were the only 2 start 4mm pitch brass pom nuts I could find on Amazon. I didn't spend too much time browsing Aliexpress, so there might be a better option there. 

You also need either:

Less disassembly, but involved drilling the frame:

2x M3x25 or M3x30 bolts

2x M3x8 bolts

2x M3 Nuts

1x 3mm drill bit

Small drill chuck (https://www.amazon.com/dp/B0CZ3M1L2Q)

Right angle drill adapter (https://www.amazon.com/dp/B07NQS465R)

Drill

-----OR-----

Less specialty parts, no drilling, but more disassembly, potentially messing up the square of your frame and rails.

4x M3x6 or M3x8

4x M3 T-nuts 

The part prints in the model orientation, but needs supports under the bearing area and in the flange cut out. You can see where I painted supports below. Grid supports work better than snug here because snug doesn't get into the flange cut out. I used a 0.1mm top interface gap, a base pattern spacing of 1mm, and forced 100% fan speed for the interface layers and 80% fan on the horizontal overhangs.

Layer height: 0.2mm first layer, 0.1 mm layers. This improves the ~30 degree overhang but providing more material underneath. 

Line thickness: Walls at 0.4mm. Gives a nice round number of walls in the area around the bearing hole.

Walls: I used 6. Seems overkill, but this part is so small that it will basically be printed solid anyway and this allows walls to meet inside the print and improve strength. Like so…

Four bottom layers and 5 top layers (because bottom layer is twice at thick).

10-20% infill, I used gyroid, but doesn't really mater much since the part is mostly solid walls.

I slowed down outer walls significantly to improve the 30 degree overhang while maintaining a consistent finish.

If you print with the door close, I recommend that you use ABS since this will be inside the printer.

The hole for the bearing is very tight. So tight that the z seam will interfere. Post process the part by very carefully shaving down the z seam/inside wall and test fitting the bearing until it fits very snugly.

Two assembly options:

Option 1 (Recommended):

Remove the glass door. Remove the lead screws. You may need to use heat or a solvent to deal with thread adhesive on the setscrews on the toothed pulleys, but if you're looking at this, you may have already dealt with this. Mount the pom nut to the oldham and the oldham to the bed. Half of this assembly will sit off to the side until we're ready to reinstall the lead screws. Removing the side panels now will make the following steps easier. Remove the top bolt from each z linear rail. Remove the camera module. Fit the finished print into the printer above the z axis linear rails and press down until the part bottoms out against the top of the linear rail. Make sure it is fully pressed into the aluminum extrusion. Use your 3mm drill bit to make a mark on the inside of the track in the aluminum extrusion. Remove the print and use the 3mm drill bit in the small chuck in the right angle adapter to make a through hole where you marked. Clean out the shavings. Replace the top M3 bolt of the linear rail with a shorter M3x8 bolt. It's easiest to install the bearing block now before reattaching the sides. Pass a bolt through the print, through the aluminum extrusion, and into a bolt slotted into the print on the far side. Tighten, but not enough to damage the printed part. Reinstall the side panels and camera. Basically, fix everything you took apart. Reinstall the leadscrews. You will need to do some eyeballing to the the two sides level and then run the bed mesh once you have everything back together. Use the bed mesh to adjust the sides one belt tooth at a time until it is mostly leveled.

Option 2 (Not Recommended):

Disassemble your printer until you can remove the aluminum extrusions that the z rails are mounted on. This is long and involved and I leave it as an exercise to the reader. Slide a M3 T-nut into the slots on the front and back of the extrusion and begin reassembling paying careful attention to the square of the frame and rails and all other components you disassembled. Position your bearing block and thread a M3x6 or M3x8 bold through it into the T-nuts. Tighten, but not enough to damage the printed part. Basically, fix everything you took apart. Reinstall the leadscrews. You will need to do some eyeballing to the the two sides level and then run the bed mesh once you have everything back together. Use the bed mesh to adjust the sides one belt tooth at a time until it is mostly leveled.

This is a long post, and I am sure that I missed something in these instructions, so if you see an issue or have a question, please let me know and I'll address it. Step file is included for easier remixing, but I'll gladly provide the .f3d if someone wants even easier remixing or wants to tweak things like the bearing diameters.