Quote Originally Posted by routercnc View Post
Steel is 3 times stiffer than aluminium like-for-like. It is also 3 times more dense, so 3 times more heavy. But this is no bad thing for a cnc machine.
If you want to get the aluminium stiffness shortfall back up to steel levels you can increase the wall thickness and/or section size, but except for some unusual cases (all members in pure tension or compression, so not practical on cnc machine), you end up back at the same mass as steel if you want to match the stiffness. But you will have much thicker walls or section sizes than the steel equivalent.
2 for steel and no contest so far, hmmmmm im shocked... any Aluminium takers then???