Gantry Size

[lab auto man]

Hi.

I have looked at many different builds on this forum and want to start building a large CNC router.  I would like some comments on how to determine the size of the material for the gantry.
For example if the gantry is 5 feet long and I use a 6 inch square tube of aluminum or steel how thick should the walls be?  I am not a mechanical engineer and am looking for some practical input.

Thanks.
Todd

[Tweakie.CNC]

Hi Todd,

The MechMate is probably the most substantial of the large scale home build machines and there is some constructional details which should give you an idea of material sizes here http://www.machsupport.com/forum/index.php/topic,15663.0.html
There is also much information on the MechMate forum (you may have to register to access).

Tweakie.

[RICH]

Todd,
You could use another machine as a quide as Tweakie replied. To do the sizing of the members one needs to look at the total gantry and how it will be framed and anchored. The gantry top frame should be sized to address static loading,deflection, running loads, and also address vibration.  The analysis is somewhat subjective since mass  and desired rigidity come into play. What one accepts as adequate would be not be acceptable for another. For any machine additional mass is desirable.  Since you are buiding the machine you are not restricted to cost restraints and can provide for an improved design.

So you would say that i have not answered the basic question and that is true. There is more to this than just the one member and info you have supplied.

RICH