Here goes...while making a 1/4" deep roughing slot pass in some 6061 aluminum using a 1" diameter tool in my '81 Kitamura Mycenter 2 (with Fanuc 6M-B control and a Fanuc 3 DC spindle motor) I actually bogged down the spindle and stopped the machine.
I was under the impression that the control looks at the difference between the commanded rpm and and actual rpm feedback and adjusts power accordingly. Is this correct? If so, is this a common situation for older DC motors especially the 3? Not knowing much about wound electric dc motors; could a winding be bad or might this issue be related to a differential feedback error? I've noticed problems slotting recently using this 1" tool in aluminum; peripheral cuts seem to be fine though.
I have checked all of the brushes and armature and all appears correct. Any ideas are welcomed and appreciated! As a note I am using true 3-phase power.