Hello,

how can I construct a defined circular arc in Lightburn?

For example:

Height = 8cm

Length = 20cm

Thank you, greetings Jan

Hello,

how can I construct a defined circular arc in Lightburn?

For example:

Height = 8cm

Length = 20cm

Thank you, greetings Jan

1 Like

Mathematically, for a circular arc, i’d need the radius of the circle to know how much curvature there is in the shape you’re describing.

The radius of the circle could be as small as 20cm, but the radius could be hundreds of meters if the intention was to have a very shallow circular arc.

We could define a quarter of an ellipse with the two numbers you’ve provided but that’s all I can gather.

I would draw the circle or ellipse with the ellipse tool then draw rectangles to provide guides for ‘Cut Shapes’.

I’d love to know more.

Knowing the chord length c and depth m, the circle radius is:

```
r = (m² + c²/4) / 2m
r = (64 + 400/4) / 16
r = 10.25
```

You could figure the angle, but I’d use a shortcut:

- Draw a circle with diameter 2r at a convenient point
- Draw a square with side 2r centered on the same point
- Translate the square along Y by +r-c (use the
`Numeric Edits`

toolbar) - Subtract the square from the circle

That will leave the segment (in red):

The blue lines show the circle and the offset square. Dimensions in millimeters, but that’s the general idea.

If you want just the arc, not the segment, delete the chord using the `Node Editor`

tool.

I do this type of work in CAD software… LB is remarkably capable, but sometimes there ARE better alternatives.

Hi,

Thank You.

I don’t need exact circular arcs, they just have to be visually consistent from application to application.

Would it be possible to construct a normal semicircle and then edit its length and width?

So you could save yourself the complicated construction or am I making a mistake here?

Thanks & Greetings

I have emphasized construct …, my Math Teacher has always said that I am a lazy one

(2x10.24 = 20.48 … sorry for the last 0.2 mm, inaccuracy ;-))

Thanks. That should be enough

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