Hi All - Back to the config face off. I added a conventional lifting arm config to the block models. Doing this made me realise that the worse case arrangement for this config is different to the worse case of the others. In the C column config the most compliant position is at the top of the column. These models have Z=250mm with a 100mm nose clearance to the table. The last model had the spindles down so they represented the longest loadpath, which is usually the most compliant. So in this case I lowered the moving column and the gantry so it had the same set up height as the std column design. I also did not include bearings on the column or the XY table so I expect it will be more compliant again then this modelling accounts for.. Envelope please:

1) X dirn - std column 4um mov column 7um and gantry 6um
2) Y dirn - 4um 4um 1um
3) Z dirn - 5um 7um 2um

So if we say the std column is a bit overstiff then the gantry wins again in this cofig.... Peter

some notes -
1) I made the arm on the moving column model 100mm wider vs the last round
2) The std column model weighs 1187 but does not have the XY bearings, saddle etc. The moving column model weighs 1330kg and the gantry weighs 1305kg. Al parts are solid steel...