Straightness of steel/alumunium box section

[daveshorts]

Something to be aware of, I was using 6mm wall Al box section from Aluminiumwarehouse.co.uk. It was pretty straight, but slightly twisted. so that in 1m, on a 50mm box one side was about 0.5mm off the supported round rail. At the moment I have just built the thing, which I will probably regret later, though it is not the worst issue with the machine.

[Jonathan]

Something to be aware of, I was using 6mm wall Al box section from Aluminiumwarehouse.co.uk. It was pretty straight, but slightly twisted. so that in 1m, on a 50mm box one side was about 0.5mm off the supported round rail. At the moment I have just built the thing, which I will probably regret later, though it is not the worst issue with the machine.

Thanks for that - definitely something to keep in mind. I'm currently intending to use 80mm, 3mm wall, box section. Maybe that's not the best of ideas.

Thinking about it if the box section is twisted then with a rail on either side they will still be the same distance apart so should run smoothly. In an extreme case I suppose it would mean the Z axis wouldn't remain perpendicular to the bed and would get slightly translated at the cutter tip - pretty negligible for 0.5mm though I think?

The number of times I change my mind on this because of all the advica I get/ ideas I have is getting ridiculous!