custom guide for 3d printer or router

[Greeny]

first i working on design to work as router and 3d printer but i have limit in money
my frame will be alumium 40*80
so i admire this diy
i think on using this instead of supported rail

Is it good !?

I don't think that's a very good design for many reasons.
If you are going to use it for a router, it's a very bad design as any debris(dust, chips,swarf etc.) would cause big problems.
Also for any use, it will be difficult to make sure your aluminium frame is straight & level.

Have you considered using vee rail?
They can be made from cheap angle iron using a hand held grinder & simple jig.
They are pretty tolerant of debris, and they can be aligned and shimmed relatively easily.
The v-bearings themselves can be hard to find at a reasonable cost though, so look in to that first if you are interested. (try https://www.aliexpress.com/wholesale...roove+bearings )

The mechmate uses v-rails on all axes and there is a TON of information about them on their forum http://www.mechmate.com/forums/index.php

Cheers