Replacing elderly Anilam 1100 control system on vertical mill

[JAZZCNC]

Something else I think should be pointed out for sake of clarity and might also explain why G28 sometimes doesn't work as expected is better explination of the intermediate move and how it works. The intermediate move is NON optional for both G28 and G30 and it must be included along with an Axis definition for it to work. But this is what can make it appear to work strangely.?
The G28/G30 commands is exclusively a move to MACHINE Zero Position, however, there's a sting in it's tail which is what bites people, so lets say you command:
G90 G28 X0 Y0 Z0 what do you think will happen.?
You'd assume X0,Y0,Z0 would mean move the axis to Machine Zero. . . .But it won't.!
Remember the intermediate move MUST happen, so in this case X0,Y0,Z0 are the intermediate move coordinates but in what Coordinates system.? Machine or Work.?? . . Yep the intermediate moves are in WORK coords, so in this case it would go to the WORK ZERO, then to the MACHINE ZERO. And you can imagine the carnage that could happen if the tool was located at the other end of the machine and all 3 axis set off going for WORK ZERO together before heading to MACHINE ZERO.!!

So this is why G90/G91 become so important when using G28/30. Often G28 will be proceeded with G91 to put into incremental mode to make it easier with the intermediate move then straight after the G28 move the next line will be G90 to put back into Absolute mode which is safer to work in.

Little differences BIG end results if get it wrong.!