All I do is have the encoder input on the IP-A jumpered across to the Enc module.

Hood

THAT explains a lot, thanks, did not know you can do that

Academic though as some of the figures I'm looking at for power required really do need all the clout i can get so wouldn't want to fit a weaker solution. It explains why she used to get warm on a busy day

Finally got the replacement Y axis screw today,

Got the table on, nice silky smooth motion

Should be able to start moving forwards again now.

Got X-axis motor plate fully fitted...

Limit switches next, Y-Axis Limits and home switches...
From the left we have Y--, Y-Home, Y++.
The home switch remains tripped once it trips so that i can home even if the switch is triggered, a home-offset value will take care of the switch position.

Then the X-axis, a bit harder this one, first idea...
From the right we have X-home then a dual-direction X-- & X++ switch. The picture is not quite right - imagine the right-hand switch is another roller type like the left one, I have one somewhere, just got to find it

The only down-side I can see is that it blocks the chances of using flood coolant again as the switches are in the way of the left drain hole.

Still thinking on this one.

Lost motion - is zero lost motion possible? never used a ball-screw machine. If i mount an indicator on the table, i can turn the Y-axis motor pulley about 1-1/2mm before the table starts to move. In terms of a Bridgeport thats really tight, the old screws had about half a turn of slop but should it be tighter?

I would have used only two switches on each axis, one for home the other limit.
You can do that if you put the switches on the moving part of the axis and have the triggers either end. You can stack the switches on top of each other so that you can have the triggers stacked.

Hood

Yes, it just seemed better on the Y axis to run 3 switches, on the X axis i do only have the two.

I hooked the rebuilt head up to my VFD today, sounds a hell of a lot better (thanks for the bits Hood) for some unknown reason it runs a bit warm around the top bearing plate though.

Its not quite right though as the vari-speed system seems to do nothing in the higher end when in back-gear, but is ok in normal gear??

Don't know how that could be, long time since I looked at a BP but the vari pulleys should be first in line after the motor whether in main or back gear so speed should vary when you move them.
Hood

Thats what i was looking at last night in the parts book, the vari-speed shaft does not move with back-gear, it's fixed so I am unsure of whats going on there, will need to mess about with it some more. I can't see any way it can be put back together wrong so that it works in high but not low - very odd indeed.

The metal came today for the X axis motor mount - once i get that cut and fitted up i can do a lash-up on the bench and get the motors powered up for a preliminary motion test

Just refreshing my mind with a study of my wiring diagrams etc and the e-stop system looked like it needs verifying

I currently have the e-stop buttons and limit switches in a loop that controls a relay that controls mains power to each of the drives and vcd's, it also supplies a signal to Mach3 via the CSMIO

Is that a good idea?

My main concern is removing power to a drive that is running may or may not be a good idea.

Or is it sufficient to simply remove the Enable signals - this does not protect from a faulty or runaway drive (busted encoder?)

Sanity check really.

Ideally you want the drive to stop before removing power, however anything that relies on AC power to power it, should not have any issues with the power being cut cleanly.

The worst that should happen, is the drive enters fault mode when it detects the internal DC bus voltage has dropped below the minimum voltage.

Power being removed while the drive is under hard deceleration would be no different to the drive still being powered. If things decelerate too fast, with too much energy being dumped back in to the internal DC supply, the drive will fault out due to the internal DC bus voltage rising too high, at which point the drive will normally fault out and let the servo freewheel to a halt. This is where external braking resistors come in, as it allows the drive to dump more energy, and avoid triggering over voltage errors.