Summing Z axis on bridgeport

Hi all,
I have a interact1 with the quill under linuxcnc control, but more often of late, I'm hitting travel issues because the workpiece is larger than my travel with different tool lengths. So I'm considering putting the knee crank itself under linux cnc control for more travel rather than cranking it about manually and trying to fiddle everything in between touchoff's.
I'd like to if possible specify somehow that the quill is to be used in preference if the Z move is inside the limits, but move the knee for the extra component of the travel when the quill travel limits are to be exceeded. My quill has a ballscrew feed on it already and the knee is still the original handcrank one so wont be a ballscrew like the quill though it has gravity to reduce backlash... I have a spare axis driver hardware already in my cabinet (I was building a trunnion table but I've just bought a fixer upper full size vmc so it'll be going in that instead) and enough psu to run a extra 1700oz/inch stepper so I hope that's sufficient overhead with appropriate (to be worked out) gearing.

Can anyone point me at further reading on this subject? I've searched around but my google fu has failed me it seems.

Thanks
Phil

hi welcome
are you sure the connection of the motor wirer are Right
your description let me think you messed up on A+A- B+ B-
and ofcause did you use a low Microstepping
1/2 is best(400) 1/4 is good(800) and then it starts to loose Torque on speed

I think it is common when you have automation of both the knee and quill to control one as the Z axis and the other as the W. If you set the knee as the W, then you can adjust and control them separately as you wish. If you try to do it fully automatically with kinematics or something else, you risk it potentially doing something you might not want it to at some point in time.

Thanks for your response Todd, actually getting my cam toolchain and post to understand that Z is split into Z and W fills me with more dread than tinkering round with linuxcnc...
I may just keep the machine as is and just use it and focus my attention on the vmc as it will have a single means to move the head.

Depending on what you are doing the cam may not even need to know about it. If your cutting depth is typically within the range of the quill's stroke. You should only need to make up the difference between tools and cutting area with machine work coordinates and tool offsets with W on the knee.

It should be possible to fit an encoder to the knee and leave it hand-cranked such that LinuxCNC would move the quill up and down as you moved the table.
Soft-limits would be the only difficult part of this setup.