I have a multiple head machine - Shoda.
The machine has 4 main spindles (Colet type) and 4 piggyback spindles that are mounted on each of the mains.
The 4 main spindles are positioned on the Z-axis carriage with manually adjusted spacing on the Y-axis. The piggybacks are attached to the mains and have a fixed X-axis shift relative to the mains.
The mains are selected as T1 - T4 and the piggybacks as T11-T14. No M6 is required to effect a spindle selection. An M3 lowers the spindle to a manually preset position via a pneumatically controlled slide.
The control is a Fanuc 21iM-A.
Do you recommend using type-C tool offsets in the X, Y and Z axises or setting a work coordinate system for each of the spindles ?