Angle of beam convergence

[evansd2]

I calculated it once to be about 1.4 degrees.

Kerf wider at the top? Surely everybody can't be wrong?

Yes, by cutting face down. (laser theory follows) There is no way to get a inverted kerf profile with the glowforge, focus height won’t do it, nothing will. It’s all down to the physics of the laser and the circular cross section of the light beam. It can help to think of it like a series of “dots” of light. You can model it pretty effectively with semitransparent circles in your favorite image editor: Imagine the laser is a circle of uniform light density (it is, mostly), you get this so…

What that translates to in terms of your material is not going to be exactly 1.4 degrees, that will depend on lots of factors. If you read through that whole thread I linked you’ll see some really smart people theorizing about the processes at play. Particularly interesting is @timjedwards diagram.