Quote Originally Posted by johnsattuk View Post
IMO I don't see a problem driving two or more motors from one output, providing the output is capable of providing the milliamps required, I have done this several times without any problems.
Did you ever bother to put scope on them and check the timings.? Most that are using the setup just presume it's working correctly because cycle times are relatively short and they don't see any obvious error but that doesn't mean it's not there. Try this with large 3D job that runs for 20+hrs and these tiny timing errors start to show.

Quote Originally Posted by johnsattuk View Post
I see videos of multiple headed machines carving many identical models simultaneously, it would not surprise me if they were driven from common outputs.
Most of these don't have independent heads they are just one large Z axis and often numatics come into play as well. Those that do will have dedicated outputs, or at least those I've seen have had.
I look after large Italian stone profiling/polishing machine used for counter tops which has 8 heads. 4 each side running on there own dedicated outputs. Each running on servos with Bespoke controller with built in PLC for controlling 86 I/O used for numatic claps etc.

While it can do different job each side mostly it Basicly just mirrors the other and would be perfect candicate for the sharing approach but they don't.! . . . . Sure if sharing outputs didn't have any affect they would take this approach.