WARNING

I just printed the model with LM16UU bearings and noticed the carriage does not fit with the default "side plates", so I made my own (out of aluminium)

The flex that those 16mm bars have is still quite a bit, so I guess if you really want a sturdy machine you might have a better time using completely different linear guides.

I will add a LM12UU and LM14UU variant for the X linear guides soon.

UPDATE

I recreated the model using the (free) OpenSCAD (http://www.openscad.org) modeler.
This new model incorporates some improvements that I felt were necessary after printing the original design that I made in Fusion 360.

• I used LM16UU bearings for the X-Axis, a lot of a play is actually coming from the 10mm standard bending under pressure.
• I deepened the T8 nut holes so the carriages can move over the connector between the stepper motor and the spindles, increasing the range of the X and Z axis a bit.
• I added a "cage" for mounting an anti backlash T8 spindle on the Y axis as well.
• It is now written in OpenSCAD, so changing parameters should work better than before.

I re-exported the STL files from the OpenSCAD file and made a LM10UU and LM16UU version for the X carriage, and a LM8UU and LM10UU version for the Z carriage.

CNC 3018 (Pro) Z AXIS UPGRADE

I wanted a more sturdy Z-Axis for the 3018 Pro so I designed a better one.

The main problems with the original design are the cheap LM8UU and LM10UU bearings and bad quality T8 spindles, I also found the 2x 10mm linear guides for the X axis will bend easily, all of this together gives the machine a lot of play by default, making cutting harder materials very slow.

I printed the parts on my Ender 3, but had to make the holes in the design a bit bigger to make all parts fit correctly, so WATCH OUT, the STL's that are uploaded have +0.5mm on the vertical holes and +0.4mm on the horizontal ones!
If you can print your holes perfect, go set the VerticalHoleDiameterAdjust and HorizontalHoleDiameterAdjust "variables" / "parameters" to 0 in the OpenSCAD drawing and export new STL files.

I used PLA with 20% infill and a 2.5mm wall thickness.

I designed the Spindle mount separate from the Z Carriage so it can be replaced with other kinds of mounts.

PARTS NEEDED

These parts are needed for all variants of this modification

• 8x Screw to fasten the spindle nut, I used pretty small wood screws.
• 6x Screws to fasten the spindle mount to the z carriage (sorry, didn't measure the length, see drawing for now)
• 1x skateboard bearing (will have to measure it / provide the exact type here soon)

Parts for LM16UU linear guides X axis upgrade (recommended)

These parts are ONLY needed if you want to upgrade the X axis linear guides to 16mm bars

• 2x 16mm rod with a length of 360mm
• 4x LM16UU bearings
• 1x T8 Anti backlash spindle 400mm

Parts for LM10UU linear guides X axis upgrade

These parts are needed if you only want to upgrade the X axis's bearings and spindle

• 4x LM10UU bearings
• 1x T8 Anti backlash spindle 400mm

Parts for LM10UU linear guides Z axis upgrade

These parts are ONLY needed if you want to upgrade the Z axis linear guides to 10mm bars

• 2x rod with a diameter of 10mm and cut to length (123mm)
• 8x LM10UU note that I doubled the amount of bearings in the Z Carriage
• 1x T8 Anti backlash spindle 123mm

Parts for LM8UU linear guides Z axis upgrade

These parts are needed if you only want to upgrade the Z axis's bearings and spindle

• 8x LM8UU note that I doubled the amount of bearings in the Z Carriage
• 1x T8 Anti backlash spindle 123mm

Happy to answer any questions!