15mm ally plate

[stk2008]

hi all sorry didebt know if this Q should go in here or not but any ways.

ive just got a plate of ally its

15mm thick
1025mm long
773mm wide

its going on me cnc as the bed base i intend to fit it with 10mm bolts at both ends it will have a sheet of ply ontop as the spoil board.

my Q is i intend to have it unsupported in the middle is this a good idea? its a hefty bit of ally ive been told it holds a tolernace of 0.001" will it bend over time?.

cheers all.

[hemsworthlad]

Originally Posted by stk2008 my Q is i intend to have it unsupported in the middle is this a good idea? its a hefty bit of ally ive been told it holds a tolernace of 0.001" will it bend over time?.

Hi Stk,
I,m no expert on this but i,m sure it will bend.
The reason i say this is because I cut my gantry end plates out of a piece about the same size, so going on that i think it would bend.
I suppose a lot will depend on what you intend to put on it and what tolerances you intend to work. If it,s just wood and the load is spread then no probs i would think, but if your putting engine blocks on it the thats another story!!

Easy way to tell would be too support both ends put dial gauge on it in the middle and then load it with something a bit heavier than what you intend to cut.. . . .I think you might be surprised how much it moves.

It,s an easy fix thou, just add a brace down the centre on the underside. . . Simp-pills. . :-)

Cheers
Dean.

[jsheerin]

It won't bend over time, but it will deflect depending on how you support it and what the loading is. The math to calculate how much it will deflect is a bit involved, but here's a link if you'd like to try:
http://elib.mi.sanu.ac.rs/files/journals/publ/18/1.pdf
Otherwise, just try it and add the middle brace if necessary.

[stk2008]

ok cheers for the replys all i will just throw 3 bits of 1" box section under it one on each end and one in middle.

cheers for input all.