Another off idea...

[mbele]

Hah, back to the drawing board...

1. Z axis travel is too short, I use following calculation:
(max tool stickout - min tool stickout) + max stock height + clamping height + safety
minimum: (35-10) + 25 + 10 + 5 = 65mm

2. To implement apron type chip guard, I need to extend Z axis overhang, and since arrangement was optimised to make tooltip as close as possible to the linear components, arrangement does not make sense any more - Y overhang needs to be extended for 60mm and axis travel is only 100mm

3. rigidity of X axis ballscrew shaft is 7x less than Z axis ballscrew, so there's no point in beefing up Y and Z if the percentage of their impact on the whole system rigidity is small. X axis rigidity can be improved by increasing shaft dia, but that raises inertia, so 2.7Nm/840gcm^2 stepper would work better than 400W/360gcm^2 AC servo, but that puts me in the no-feedback scenario, so there's no point in using servos on other axes...

[dazp1976]

Hah, back to the drawing board...

1. Z axis travel is too short, I use following calculation:
(max tool stickout - min tool stickout) + max stock height + clamping height + safety
minimum: (35-10) + 25 + 10 + 5 = 65mm

2. To implement apron type chip guard, I need to extend Z axis overhang, and since arrangement was optimised to make tooltip as close as possible to the linear components, arrangement does not make sense any more - Y overhang needs to be extended for 60mm and axis travel is only 100mm

3. rigidity of X axis ballscrew shaft is 7x less than Z axis ballscrew, so there's no point in beefing up Y and Z if the percentage of their impact on the whole system rigidity is small. X axis rigidity can be improved by increasing shaft dia, but that raises inertia, so 2.7Nm/840gcm^2 stepper would work better than 400W/360gcm^2 AC servo, but that puts me in the no-feedback scenario, so there's no point in using servos on other axes...

1 thing I'd say is use Angular Contact bearings if you are going to use Chinese DFU nuts & screws.
I used thrust bearings on my first small benchtop mill and on my second I've gone with Angular contact.
I would NEVER go back to thrust. They don't sit on the end of the ballscrew correctly and this causes a wobble you can't get rid of. Rigidity was crap no matter how tight all the axis were set up.

The new on with the AC's is rock solid and all the axis are set as 'light touch'. It really is chalk and cheese just because of a difference in bearing types used. I did however have to make my own bearing housings from scratch because of the sizes of AC bearings available.