Redesigned Z-stage support for Vertex K8400 by Sverenja

Last crawled date: 3 years, 1 month ago

There are two problems with the way the original K8400 Z-stage is designed.

The whole Z-stage is resting on the coupler between the motor and the leadscrew. This coupler then acts as a spring and can be compressed by ~0.5mm just by pushing on the leadscrew with a finger. I see this a lot in 3D-printers and it's just bad practice. The coupler is just there for misalignment between the leadscrew and the motor axle, NOT to actually take any load in axial direction.

Because there are individual holders for the linear bearings, it's very easy to misalign them resulting in high friction and maybe even choppy movement with cheap bearings. This is enhanced by the springiness of the motor coupler, because if the bearing is stuck the coupler will just stretch and then jump resulting in uneven layer heights.
My solution:

I designed a new motor mount for the Z-Stage which includes a pillow bearing (for example: Miniatur Flanschlager 8mm) There is still room under the motor and three of the original mounting holes can be used. I drilled two more to have more stability. The whole Z-stage now rests on the pillow bearing which has no flex resulting in very even layer heights.

I just connected two of the original bearing clamps in vertical direction so that no misalignment is possible here. In addition I used high quality linear bearings (Misumi) as the originals are not very good.
Additional hardware needed:
1 countersunk M5x10 screw with nut (lenght not critical)
2 M5x12 screws + nuts for the pillow bearing
Pillow bearing for 8mm rods/leadscrews.
Preparing the pillow bearing:
Those cheap pillow bearings are stuck in the housing at first, but they are supposed to swivel to compensate for misalignment. You have to brake them loose by force, take them out and polish the mating surfaces by adding metal polish, pop the bearing back in and move it around. Repeat until smooth then add grease
Assembly:
Mount the motor to the motor mount
Attach it to the Vertex rear panel. The top screw on the right has to be the countersunk screw.
Add the coupler.
Pillow bearing (you will curse a lot)
Add the leadscrew.
Drink a beer