Design

I make an solar concentrator dish mould but I confuse in how to calculate the focal length.for that I use the parabolic calculator to find out dish focal lenght

so in hat parabolic calculator I put the values of diameter of dish is 600mm and depth 90mm and said okay then the software gives us the focal lenght is 250mm

then I open the solid works i draw one circle with 600 mm diameter and and depth 90mm

then I revolve the part it makes dish

then I extrude this part

this dish is in 3d but I want to cut mould in laser cutter so I convert this file to 2d using 123d make software