Use pipes as linear axis?

Hi

I am building myself a RepRap much like the Mendel90 but a bit bigger.
My project will eventually have a build volume (.5x.5x.5)m

To do this i need quite long linear rods, 740mm.
These was quite expensive, so i wonder if i might could use pipes instead?
I want to use 16mm pipes with 2 mm thick walls.

Is there anyone that has experience with this? will it work or will it sertantly fail?

It depends, I have found very cheap linear rods in my country, so I would first advice you to look for cheaper solid ones.

Solid rods can be hardener and made into a perfect fit where pipes cannot be produced in the same way.

The most important factors are both Hardness and Precision.

Not too sure about round pipes, but I have tried something that might be useful to you: Cheap, low vitamin count linear rail

You can get aluminium extrusions (make sure they are the anodizes versions!) from hardware stores for about max. 10€ per meter. While not as accurately made as "proper" hardened steel shafts, the straightness of these square profiles should be enough. And as long as you can adjust the glide surfaces, the aluminium extrusion can be slightly oversized or undersized.
I have tried bending 20mm square profiles; there was only very slight deflection even though I applied quite some force. So that should be enough, but if you want to make sure, you can use larger ones.
The advantage of a square profile is that you only need one rail since the carriage cannot rotate on it like on a single round rail.

use stainless steel 12 mm instead of 16 mm pipes, they are stronger.

those pipes dont have tight tolerances, stainless stell pipe is easy H9, and linear bearings are cheaper.



here is my first diy cnc machine i have used 25mm dia pipes, then switched on mangan steel bars.

here me and my girlfriend (now wife ) testing machine, 4-5 yrs ago.

i am currently making my first repstrap, but with 10 mm rods. 300x300x200-250 milimeters working area.

and ofcourse i am not satisfied with 10 mm rods, i should use 12 or 14 mm, but for first machine it will be ok

Edited 2 time(s). Last edit at 05/28/2013 09:23AM by woo.