I need to flatten a piece of extrusion

[boydage]

Alloy 6061 10mm x 200mm x 620mm. The alloy is extruded, so its kind of straight but not if you know what I mean. I guess its about 0.5mm out.

I am too tight to pay someone to machine it flat and my router is not good enough. Its for a new Z axis in order to make a machine that can make things flat.

So. I am thinking a block with something like 600 grit wet and dry? I tried a stone but dont see that working.

Thoughts from a metalwork Guru? Thanks

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[NIC 77]

Please help me to understand here.....

Is this the piece that you have already modified for your Z axis from another thread? Did it bend after being bolted together?

Or was it a little bit off before that?

Or are you talking about another piece? Is this for the piece the spindle will mount to?

I assume it has a little bit of a curl to it? In which way...along the 200mm or the 600mm?

[boydage]

Yeh cool no worries. Yes its the back plate that the linear rails and hardware bolt too. Yes different section of forum I dont know who looks at what and this is not something I am familiar with tbh. So I have posted here in the manufacturing grinding section,.

Correct, its been drilled and I found it had a small curl on the 200mm. I managed to get that out today but now it has a curl on the 600mm so I cant seem to win. I guess what I can do is by the time I install the sides and linear rails it should pull straight. Its very small but I would like it to be better.

This is the diagram - piece I am working on is the green one. I have drilled out the sides every 40mm (approx) and they are straight. Its just not as flat as I would like. Darn

[NIC 77]

Yes, I see from the drawing that you've bolted your stiffeners on the sides....

rats, I should have said something. If you bolted through the plate into the stiffeners instead it should pull it flat.

[boydage]

Ha. True true! I actually milled it flat last night - very carefully, by bolting it down to a sacrificial surface already machined with the same router. Does that make sense? I also found that it was only 0.4mm out of flat - seems like a huge gap until you actually measure it.

So the final result, is, the surface that holds the rails and ballscrew has been flattened to the best I can. I then rotated it, and machined the back where the linear blocks sit to hold it to the gantry.

The sides are only 6mm so drilling into them would have been a bit tight. I have actually found its quite flat now with the machining I have done. Along with the linear rails being SBR20, drilled at 75mm intervals should end up with something quite flat and very rigid.

Thanks mate for the words