CNC FIXED HANG / SLIDING HEAD MACHINE in Taiwan

I went to a friend’s manufactures in Changhua / Taiwan. They are making the KNURLING MOLD DESIGN / PRODECE

WHAT’S DIFFERENT BETWEEN FIXED HEAD MACHINE & SLIDING HEAD MACHINE?
  >   SLIDING HEAD MACHINE IS MAKING THE BIG ITEMS ( THE DIAMETER IS 20mm +) NORMALLY.
  >   FIXED HEAD MACHINE IS MAKING THE SMALL ITEMS ( THE DIAMETER IS 35MM-) NORMALLY.

click   http://www.aecnc.com.tw/   to see more about them.