Which grade aluminium?

[jonbabbz]

Hi all. I'm starting building my machine this week and am starting with my z axis. But Im not sure which grade aluminium would best be suited to my needs. I'm buying a large plate from aluminium warehouse which i will be cncing into various parts. I just wanted to be sure before I wax £150 on the wrong stuff. Is the 6082 stuff sufficient or will I have to go for ecocast? I know ecocast will be easier to machine but it's so much more expensive.

[JAZZCNC]

For most stuff the 6082T6 Flat bar is ok but it's NOT flat so if you need perfectly flat then be prepared to surface both faces and obviously lose some thickness.

What I do is buy the 6082T6 for none critical parts like gantry sides, motor mounts etc then buy the Ecocast for things like Z axis and bearing mounting plates etc.
Doing it this way saves me a load of time because I don't have to machine any critical areas like bearing mounts flat and basicly can bolt straight to surface.

The 6082T6 flat bar in wide pieces it's seldom flat and has a slight cup to it and in critical areas like bearing mounts then chances are you will get some binding in the bearings. . You can get round this and keep some thickness by machining just the bearing mounting areas, which is what I used to do but it's time consuming. The ecocast is much quicker and more accurate better looking.

I recently got some of the 5083 series cut plate from them and that was resonably flat and a bit cheaper than ecocast, it cuts ok as well. Ecocast would still be my prefered choice for the Z axis thou.!!

Edit: Ecocast is no easier to machine it's exactly the same to work with as 6082T6 it's just precision ground flat.!!

[Jonathan]

Flat aluminium bar is nowhere near flat, but if you get standard 6082-T6 flat plate I've found that to be very close. If you're using supported round rails it will be sufficient, but with profile rails greater flatness is required to stop them binding so I'd go for milling pockets in the flat plate or if you've not got a milling machine get the eco-cast.

For example:

6109


Edit: Ecocast is no easier to machine it's exactly the same to work with as 6082T6 it's just precision ground flat.!!

Surely it's milled not ground, not that is really concerns us.

[JAZZCNC]

Surely it's milled not ground, not that is really concerns us.

So why bother saying it Numb nuts.!!! . . . .

The stuff I've got here certainly looks ground or they must have 8ft fly cutter looking at the radius of the machine lines.?? But I won't argue if somebody who knows better says other wise.!!. . . All I do know it's very very very flat.

[Jonathan]

Fair enough, it is surface ground:

http://bbs.homeshopmachinist.net/showpost.php?p=337171&postcount=10

I wasn't aware that grinding aluminium was realistic, so assumed it was done with something like a fly-cutter as the finish does look like it.

Learn something every day...

[jonbabbz]

Ecocast it is then, cheers!