Z Axis appraisal please

[EddyCurrent]

I'm reluctant to start a Build Log until some details are ironed out, if you think this is wrong then please let me know.

This a Z axis that tries to keep the overhang to a minimum while still using slightly modified off the shelf ballnut and ballscrew end support.
The ballscrew is supported at the top only but I can't see this being a problem.

All plate is 1/2" - is this enough ?
Ballscrew is 1605
Rails are 15mm Hiwin



Can't seem to add the sketchup file

[njhussey]

Two things jump out at me. The first is the carriages are too close together buoy need to space them out more. The second is that the ball screw will whip with no end support so speed will be severely compromised.

[EddyCurrent]

Okay re. carriages but how can the ball screw whip when the linear bearings are keeping everything firmly in place ? maybe it happens most when the Z axis is at it's highest point ?

[JAZZCNC]

Ok 12.5mm plate is too thin you need 19-20mm minimum other wise it will flex, you could get away with 12.5 on the rear plate but I wouldn't advise.

The way you have the ballnut on top of front plate means the rear plate is longer than needed really wasting money and adding weight.
The screw not being supported at both ends isn't a problem at short length(<150mm travel) but if having long travel and with you having ballnut right at top then supporting both ends would be better.

Bearings are too close together which has been said. . . . BUT .. . Also you haven't shown how it's fastening to Y axis carriages and I suspect those bottom bearings will be in the way of bolt holes.? It's a common Err and chances are you'll raise them up 20mm or so.?

I wouldn't get too carried away with trying to reduce overhang, the little you'll save won't make a big differance to cutting area but could to performance and quality of cut if taken too far.!!

[Boyan Silyavski]

The ball screw will not whip. On my small machine its exactly like this. Though if s**t happens and the screw pushes a hard stop bolt/asuming you fix one/ or table bed, everything will bend, instead of just stalling the motor. Or so it seems. At least mine bended a couple of times.

[EddyCurrent]

Thanks for taking the time to look and advise, now drawing version 2