Z axis is one of the most crucial parts of your CNC. As it works in a sort of a cantilever fashion it is very important that it does not give away in any form else the cuts won’t be clean.

Before I proceed I want to justify my choice of material I used for the plates on here.

I know acrylic is comparatively weak and very brittle as compared to aluminium but as stated above I wasn’t able to source any aluminium plates so I needed an alternative. The only materials in sheet form I could find locally were acrylic, plywood, pvc, MDF & steel.

PVC sheets weren’t any thicker than 10mm so that was a no go.

Plywood and MDF had some room for flex and didn’t seem like a good choice to put them over a machine made of metal.

Steel could have been a choice of material here but I wanted the keep the load on the gantry at a minimal and adding steel seemed like a lot of unnecessary load.

Acrylic like other materials can be very weak when thinner sheets are used. I used 15mm acrylic although I recommend 20mm and would probably replace the 15mm with the latter in the future. Such thick sheets can be quite tough. I tried my best to bend it or break it manually but failed. It is mostly the impact force that could crack an acrylic which I won’t think would be a problem on a CNC machine. As far as bending is concerned the amount of force required to bend and break this thick acrylic sheet is way more than what a DIY CNC machine is capable of putting. There are other things that will probably fail before this happens (eg. Bits breaking or spindle stalling etc.).

Also there are a few advantages of using acrylic. It could be easily and accurately laser cut. I got mine laser cut. Also its very easy to make threads in acrylic with a regular tap. I have used no nuts on the z axis. All the bolts are held by threads tapped in the acrylic plates. These threads hold the bolts very tightly and securely and not one has come loose since my few months of using this machine. Apart from everything else it looks super cool.

Now that all the plates were cut and tapped it was just a matter of time to screw all the parts for the z axis together. I used a small piece of steel C channel to join the top bearing blocks to the z axis plates which in turn were directly screwed on to the lower bearing blocks. Then I was able to mount the final gearbox on these plates which would drive the Z carriage.