new build opinions required

[Boyan Silyavski]

George,
To avoid chicken egg problem, why not start from the Z. Usually the weakest spot on any machine. THEN this will command the gantry design. Or you have it clear there?

[george uk]

Hi

To avoid chicken egg problem, why not start from the Z. Usually the weakest spot on any machine. THEN this will command the gantry design. Or you have it clear there?

i started with the plan that the z should be able to handle different spindles+additions, without differing what forces it can handle in both +-xy. most of the moving gantry designs, like the one you linked to, favour one direction down X, and rely on weight of the garntry to offset the stability looses you get by having to mount the spindle forword of the Y, on the drawing you link to, every mm forword the z mech is away from Y, the force you can apply at the bit tip drops substantialy, and would be different X+ than X-.

so, the problem/limit for z, when considering deflections , is all in the Y, when you factor in a 4th axis, again the differing forces between X+ and X-, start loosing accuracy , the longer the jobs running, the worse it gets, the bigger the job is down the x axis, the faster this will happen. .

but, if you have 2 of them Y axis you linked to, facing each other, and the Z in the center, Zs force is equal on X+- and Y+-. the forces Y can take, could be ajusted by spacing th 2 bearings per rail further apart

then, Z drop, is the next place you start looking at, will try and get it in sckechup tomorrow, failing that, i will take a photo of my drawings and post that