【求助】DA XIA, DA XIA.......how do this precise cutting?

my computer has not chinese software, sorry
  
1. I bought a metal block, measured dimension are 10.067mm x 5.455mm x 3.213 mm.
  
2. Now I use CATIA to get 3D model of this block according to above demension.
  
3. I want to use Laser precise cutting machine to cut the block to dimension 10.007mm x 5.405mm x 3.213 mm.  the precision of our machine is enough.
  
4. But after i put the block on the worktable , i can not catch the start point on the block precisely. ( the precision of the optic lense of the laser machine is good, but how do i control the trace of the laser beam along the profile of the block
  
Do you have some advice or instrument ? DA XIA