Steel frame for 8' * 4' cnc bed ?

[Jonathan]

So whats the formula to get Mach to stop loosen the rails eliminate binding and tighten back down.??? . . . Your talking tosh and again

I think you're missing the point I'm making. I said in my last post that obviously it's better to get it right to start with and that software compensation helps if and only if it is a *small* error. I didn't think I needed to state that by small I don't mean binding or tight rails as you'd be foolish to try and run a machine like that for obvious reasons.

Software compensation and formulas etc are last ditch work around

Exactly ... which are better than nothing. If the machine is running smoothly then I see no reason not to use maths to improve it.

No matter how well you build the machine you will never get all axis perfectly true and perpendicular. The best you can get is the error being negligible compared to the tool deflection. If it's only just over negligible then the machine may well run smoothly and if so you can use the formulas to compensate.

Much more helpfull to give sound advice encouraging good accurate build quality than saying just build it and don't worrie because software will compensate

I thought I did say that in my previous posts ('it is better to get it right to start with') on this thread. If not I'll not bother.