[fastbike]

This is a supplementary thread to the others detailing the conversion of my Emco F3 mill, in which I will detail the changes to the electronics and some considerations for selecting a controller.
The original electronics are switch gear that are typical of the period: good quality equipment but very 1980's in execution. The power supply is 3 phase 400V AC, and interesting has no neutral wire, read on. Power to the main motor is controlled via a two speed dahlander switch which allows the motor windings to be connected as delta or star to vary the speed.
Supply to the existing X Axis power feed (the only one originally fitted) is via a transformer and the variable speed is handled by some crusty looking electronics on a board in the control box.
The coolant pump is a 3 phase motor and has a simple 3 pole switch.
The DRO is an obscure brand (Aurki) and requires 230VAC. This is supplied by one phase and connecting the DRO's neutral wire to the mill's protective earth - thus relying on the tie between the neutral and earth at the building's electrical installation to carry the return current. IMO, this is not a particularly safe way of doing it but I'll be ditching the DRO once I have the CNC conversion completed so it stays at this point in time.

The manual controls are placed on a sloped panel facing the operator - this panel sits atop the control box which is a fabricated steel cabinet bolted to the rear of the machine column. Dimensions are roughly 500H x 250W x 190 D, with the control panel protruding another 195mm.


The slightly later F3B model changed the shape of the control box - it does not slope back under the operator panel - and I think a design similar to this could provide additional internal capacity for the gear that needs to be installed.

There is sufficient room to make the box 50mm wider (although I'd like to reuse the door), or make it deeper.