Kobra Z axis support Mod - KobraThrustBearingHolder

NOTE THIS IS EXPERIMENTAL AS OF NOW CURRENTLY INSTALLING AND TESTING

Inspired by NunoFlyer's Anycubic Kobra 3 Ring for Thrust Bearing, this improves the design by adding a tighter fit, adding spots to press fit the bearing into, adding a top assembly to attach the shaft coupler to.

Why this mod?

Kobra 3 and may other printers rest the entire gantry on the motor shaft.  This is bad for the life expectancy of the motor.  This uses a small thrust bearing and a housing to get the weight of the motor.  Not only does this increase the life expectancy of the Z-axis motors, but it can also help with Z banding.  And under $1 a thrust bearing it's worth it instead of replacing a $40 motor later.

Not just for Kobra 3 or OEM parts!

Due to being created on OnShape, it is able to be modified easily for any 3D printer or non OEM parts that has this issue.  Thanks to the configuration feature all you need to do is measure and answer a few questions.  See the configurable CAD file on OnShape!

Materials

• 1-2 F8-16M 8 x16 x 5mm Miniature Thrust Axial Metal Ball Bearings depending on the count of Z-axis motors.  But any bearing you can fit in there should work if you configure it with OnShape.
• PETG, ASA, or ABS is recommended.  PLA+ will work and PLA may not last.
• Grease for the thrust bearings
  • Super Lube-21030 Synthetic Multi-Purpose Grease (Recommended)
  • Super Lube-21010 Grease with PTFE (Recommended if price is not an issue)
  • Permaxtex 80345 White Lithium Grease (Will work)

How to install?

1. File any rough edges off, especially on the bottom of the top part so the excess material does not rub against the bottom part.
2. Insert the insert the bearings into the top and bottom parts with the groves showing.
3. Place the middle part of the bearing into the bottom part while greasing it.
4. Put the top part onto the bottom part.
5. Clip the plug in.
6. Ensure the assembly rotates smoothly.
7. Follow the Kobra 3 Combo-Z-axis backlash elimination assembly replacement guide you can skip their Step 2 as we are not replacing it.  You may need to remove the anti-backlash assembly.
8. Slot the assembly onto the motor.
9. Place the shaft coupler into the top part.
10. Attach the lead screw to the shaft coupler and use an S2.5 Allen key to tighten the coupling screw
11. Realign the Z axis timing belt so that the gantry is level.
12. Unscrew the timing belt gears on top if the belt does not slip for adjustments.
13. Check the Wheels: Ensure that all the wheels are in contact with the rail. If they are spinning freely, they might not be making proper contact.
14. Adjust the Eccentric Nuts: Use an open-end wrench to adjust the eccentric nuts on the wheels. These nuts allow you to bring the wheels closer to the rail or move them away. Turn the nuts until the wheels are snug against the rail but still able to rotate without too much resistance.
15. Test the Movement: After adjusting, manually move the Z-axis up and down to ensure smooth movement without any wobble or excessive resistance.
     

Can I sell this?

As a kit, no.  With a 3D printer, yes, as long as you don't buy them and resell them like a retailer does with a markup.

Notes:

It looks like some filaments have different tolerances

• Anycubic PLA+      : 0.05mm
• Creality PETG-CR : 0.1mm

Can I use screws to close the grease holes?  No, they need to be 1.2mm long and would get lost, hence the ring.

Can I use regular bearings?  No, they just won't support the axial load well and get in the way of the lead screw.

Can I skip the grease?  You shouldn't, but you could use the grease that came with the 3D printer.

The assembly rotates and is slightly loose, is that a problem?  As long as the assembly does not interfere with the Z-axis, it should be fine.  It rotates anyway.