Proper size of Z axis rods?

[simmonsk]

Hi,
I am seeing a lot of 1/2 inch rods 12 inches in length Thomson with pacific linear bearings. Is this stout enough to build a 6 inch travel Z axis with a laminate trimmer power head? I intend to cut copper and wood mostly.
Thanks, Ken

[simmonsk]

Hi,
A bit more detail. I plan on 4 pacific hardened linear bearings. 1/2" acme with dumpster nut, aluminum plate for the structure.
Thanks...Ken

[andy_ck87028]

For me this is also an interesting question. I am using 10mm hardened rods and have yet to discover whether it will work as I am currently building.

I recognise that I run the risk of having flex and have therefore designed around it as much as possible. I also realise that supported rods would be better than unsupported rods but budget has forced me down the unsupported rod path.

To minimise the problem, I am using three 10mm rods and an acme thread.

I have placed the 3 rods in a triangle formation; one behind the router next to the acme thread and one each either side of the router.

I have also got 4 linear bearings (2 each side) placed as far apart as practical and mounted on the router backplate and one long linear bearing mounted on the slide assembly. Conversely, two rods are mounted on the slide assembly and one rod mounted on the router backplate.

Once I have it finished, I will know if I have a problem.

The way I have designed it, I will only have a problem when fully extended which means fully extended will be used for lightweight material where flex is less of an issue.

Conversely, when not fully extended, I will be able to use it for heavyweight cutting.

I am able to do this because I have incorporated a variable height table into
the design.

I'm expecting this approach to work but the bottom line is "I don't know".

If it doesn't work, I'll go to supported rods and hang the expense.

Good luck

Andy