retrofit on EMCO PC turn 55

The original Emco 55's hardware includes hall sensors on the x and z shafts, firing once per roation. How do you think these were used in the original configuration, and should I try to use them?

The original Emco 55's hardware includes hall sensors on the x and z shafts, firing once per roation. How do you think these were used in the original configuration, and should I try to use them?

A very good question that I pondered for a while. I figured they were probably used to rotate the lead screw to a specific position after detecting the home switch. I chose to ignore them for the time being but I wonder if they could be used to improve homing accuracy. I suspect someone good with classic ladder programming could figure out how to do this and maybe I would investigate someday but that day has not come yet.

Wow, that looks like a perfect fit. I removed the sensors but I could put them back in. How much do you think it would improve the accuracy of the homing sequence? I have hardly used this machine since I did the conversion but my initial tests indicate the switches alone have a couple thou variation. I work around it by touching off tool 1 on the turret and all the other tools follow based on the tool table.

Perhaps the easiest solution is to wire the home switch and the proximity (index) sensor in series. Both home switches on the Emco are roller switches and the actuator is a ramp so they can over travel quite a bit. As you eluded to, if you over run the index pulse, things will go haywire. I think the home search speed is slow enough this would not happen though.

cs

I got the lathe! Unfortunately, it was dropped along the way, but it seems like $100 will cure what at first seemed like terrible damage. The carraige had become detached. However, getting this re-attached amounts to just replacing $30 worth of retaining strips.

It turns out my motors are different from Chuck's. They are 3 phase NEMA 23 motors, VRDM 366/60, which are probably driven sinusiodally. I should be able to swap them right out, except for needing to drill a hole in the shaft for a retaining pin.

I spent about an hour trying to work through the stepper board. I didn't make much headway--it seems like every trace has at least one through hole. There's a 16-pin connector that somehow translates into up to 3 axes but is configured with 2 motor power boards, each with 6 transistors. This would probably yield its secrets in a few hours if I were disciplined about tracing it through and writing eveything down.