how to draw parabola with focal point

I can’t think of a way of creating a parabola and it’s focal point in LB. Many years ago I did write an NC code editor/generator that has this ability though. Is this a one-off or is this something you’re going to want to do regularly?

What’s the focal length and dimensions of the parabolic curve as I should be able to generate one for you?

Thanks Marcus, I think i will draw it out in graph paper .

If you can give me the focal distance etc I can get one done for you in a few minutes.

X=150mm F=60

Just to clarify is X the diameter, radius or depth?

x=radius 60=depth

How does this look? This has a focal length (F) of 60mm with a 150mm radius. Let me know if I’ve misinterpreted what you want.

Parabola F=60, Dia.=300.lbrn2 (12.1 KB)

EDIT: BTW, the circle denotes the position of the focus.

Thank you looks good. Thanks for lightburn, really a great program

Good, don’t forget to let us know how the project turns out.

FYI: The geometry is approximated with a bunch of circular arcs.As a result the focus won’t be a single point but spread over a distance.I’ve just done some checking of the geometry and measured the spread to be 0.16mm.

Hopefully this is good enough for your purposes but if you need it more accurate I can do another with more points/arcs.

If you are up to speed on your algebra, you may find this site useful.

Just thought I’d try it in FreeCAD:

You need to convert the parabolic curve to b-spline before you export it as DXF but it seems to work and it might be more accurate than my approximation.

Here’s the DXF if you want it:

Parabola F=60, Dia=300 from FreeCAD.dxf (5.3 KB)

I hate you guys. I had to miss recesses just to learn to divide.