whenever i use a m30 in a program that has a sub program loop cycle in the beginning it always stops at the m30 and doesn't rewind the program to the beginning. if it is a normal program it will rewind itself. any ideas why ?

Can you attach your program file to a Post and I can try running it through my Haas lathe simulator.

M30 ends the program and resets the machine. You need to use M99 to get the subroutine to loop. Hope this helps.

try this code

G00 220. Z150. ;
M05 ;
M30 :

as it turns out,i spent time one night trying to figure it out. it has something to do with the m code to open and close the chuck. anyways, i found that if i put a m01 before the m30 it would reset the program now.

go figure.:)