Straightness of steel/alumunium box section

[Ross77]

The machine I got from ebay has, from memory, 90mm Rhs, a 9mm wall and its welded (erw) and that has been milled for the rail mounting surface (I guess thats why they used 9mm to allow for the removed steel) this has only been done on one face so internal stress wouldnt have been a problem.

Ali is also lighter, dosnt rust (not like steel anyway) and dosnt need painting


Are you using the rails back to back on the y axis to counter the uneven load distribution? (ie 25% reduction at the open side) if so have you looked at doing the same with the zaxis? if you mounted them on a c channel (or box with a slot cut out, then you would have space for the Drive screw as well)

Just a thought and is some thing I was looking at a while ago for an Ali box and supported round rail machine. Not enough hours in the day..........

[Jonathan]

Ali is also lighter, dosnt rust (not like steel anyway) and dosnt need painting

True, but it's not as strong and more easily transmits vibrations since it's less dense...

Are you using the rails back to back on the y axis to counter the uneven load distribution? (ie 25% reduction at the open side)

Exactly.

if so have you looked at doing the same with the zaxis? if you mounted them on a c channel (or box with a slot cut out, then you would have space for the Drive screw as well)

I looked at it, but didn't think of using C-channel which would make it quite simple.
The place near me has some 3"x1"x0.25" aluminium angle. There's also U, 2" x 3" x 2" ... only 3/16" thick though. Time for some more drawing / calculation!