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Machining of head for prill manufacture

A Prill Head is a domed sheet of metal 800mm in diameter with 2895 precisely drilled holes in it (rather like a large watering can rose). It used by our customer to manufacture 'prills' (pellets).
Due to the customers process the size, shape and position of the holes in the Prill Head are very tightly defined with high engineering tolerances. We start with a flat sheet of steel which is spun into the domed shape, before carrying out the drilling. However, after spinning the domed plate is no longer concentric or of even thickness.

 In order to meet the customer's requirements, we modified one of our large milling machines, adding a 4th axis to the machine to give it the flexibility to move the plate to exactly the right position for drilling.
We made further modifications to the milling machine to enable it to determine how to drill, ream and countersink the 2,895 holes so that each individual hole has exactly the right dimensions and geometry.

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