After casting, a die trimming operation cuts the gates off and removes flash from the bolt holes and the periphery. 

This produces four heat sink blocks.  No additional machining is necessary. 

The quality assurance procedure consists of four measurements. (Linear measurements are made with a coordinate measuring machine.)

 -- the thickness of the block

-- the flatness and surface finish of the mating face

-- the true position of the bolt holes 

-- Internal porosity is evaluated by weight checks against a standard weight.