I'm in the process of converting my Bridgeport to CNC, servo's, CSMIO etc.

If I had a motor on the knee-lift screw as well could it be tied into the Z axis DRO in Mach3 as well as the normal Z axis ??

Only one would be moving at a time.

Just a thought.

Don't think you would get away with that, could cause all sorts of issues.
Might be better setting as an A, B or C axis and using it solely for tool length offsets.

Hood

Good point, just a thought.

Probably just fit a normal power-lift to it.

Power lift is good, the Beaver NC5 I have has it as standard and it saves the old arms
Only advantage having a servo would be it would be automatic.
If there was a tool changer then servo would be the way I go but as it doesn't then probably not worth the expense.

Regarding the power lift, a lot of people have just made up an end to fit in a cordless drill and use that, a  friend has done it and he says it works great, here is his mill.
http://www.machsupport.com/forum/index.php/topic,29886.0.html
Hood

Thanks Hood, that Avon looks to have a bigger set of balls than the Bridgeport

Nice enclosure too.

I have a feeling that there is a gap about as big as the Cheddar Gorge between my current experience level and that of just being able to close the door and press cycle start

I want a little better than the drill lift idea, I have a geared motor that will do the job, its a bit big but it's free, VFD drive too

Yes, the Avon is about the same size as the Beaver NC5 I have and he did make a great job of the enclosure.

If you have all the stuff there then yes a drill doesn't make much sense, a geared motor is the way to go
Hood

Reflecting off the OP, would it be possibule to write G00 script which would use the knee as rapid Z and the quill as "feed" Z ?

Guess you would have to invert the -+ movement in the script depending on "which Z" is moving. But in the end, the tip of the tool will always be correct with the DRO.

Hummm

Reflecting off the OP, would it be possibule to write G00 script which would use the knee as rapid Z and the quill as "feed" Z ?

Guess you would have to invert the -+ movement in the script depending on "which Z" is moving. But in the end, the tip of the tool will always be correct with the DRO.

Hummm

Not sure if that could be made to work but it is certainly a very interesting idea.

Tweakie.

The main issue would be the CSMIO/IP-A is closed loop and updates the DROs in Mach from encoder position.
 If wanting to update the Z Dro from both knee and quill you would have to feed both motors encoders to the same encoder inputs.
 I think that would cause a lot of issues with the IP-A and it would forever throwing  PID errors.
Hood