Basic Fresnel lens with Fusion360

By | 19/02/2017

Fusion 360 is free, and handy if you want to make engineering objects. Proved to be really difficult for other things.

  1. First, we need the radius of a simplex thin lens of f=4cm. The refraction index of the clear resin is close to 1.5. There is a handy calculator in Hyperphysics for the Lens-Maker’s formula here.
    The formula reads:

    (1)   \begin{equation*}  P_{lens}=\frac{(n_{lens}-n_0)}{n_0}\left(\frac{1}{R_1}-\frac{1}{R_2}\right) \end{equation*}

    I set n_0=1 n_{lens}=1.5 R_1=\infty and for a f=4 cm, the R_2= 2 cm.

  2. In Fusion 360 sketch, I draw a hemisphere of R_2= 2 cm.
  3. I place equally spaced lines from the bottom until it connects with the hemisphere
  4. I sketch over arcs tracing the hemisphere between the segments.
  5. I remove the hemisphere and the lines
  6. For each segment of the arc, I remove the coincidence with the next
  7. I move the segment down to the lower plane with point-to-point move tool, and create perpendicular lines
  8. The final sketch looks like this:
  9. I revolve the sketch to obtain the 3D printable part

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