Simplify arcs with less control points


When I draw a arc I see often more control points than 3 and I can’t simplify the arc.
If I save it as dwg and open it in acad you see 3 controlpoints but when I import dwg in to rhino again I see more control points again.

I need for cnc cutting as few program lines as possible

Why is this,

arcs.3dm (25.0 KB)

Arcs of more than 90° in Rhino will have more than 3 control points. This is totally normal. They are still arcs. An arc is an arc, it doesn’t matter if it has 3 or 5 control points. A circle will have 8.

For CNC, if your controller can understand arcs, then machining the full arc takes one line - G02 or G03. If your controller cannot accept arcs, they will be broken up into a series of G1 line segments for machining in any case, so the control points on the original arcs don’t matter anyway.

but if I have a straight line I can do simplifycrv what gives me less program lines (lowest 2 lines) but 3 arcs connected (arc on top) you can’t simplify with a command that you get it like the arc below the top one.

Dunno, Simplify seems to work here…

Also works with a total of the 3 arcs of less than 90° to get a 3-point arc after simplifying:

I did a simple test too like you and that works here as well.
now find out wich case it doesn’t
Also thought simplify was only for curves and not arcs, but I was wrong :pensive:

In cases where it fails, it may be that the arcs are not 100% tangent to each other at the joints (within tolerance)…

Yes I think that is one of the promblems to check

@Helevetosaur, if Edward wants to use the curves for CNC routing shouldn’t he run the Convert command to change them to arcs?

no that is not the problem.
For that I have a python script converteercnc what works great, but still I want to keep my cnc files as small as possible.
So every improvement is welcome

They already are… If they are not, and they are within tolerance of a true arc, Simplify will convert them back into arcs (V5 had a bug where that didn’t work in all cases though)

Oh, and I guess it’s important to note that if you do use the Convert command to convert splines to a series of arcs, be very careful what angle tolerance you specify on the command line, the adjoining arcs that result will not be tangent to each other better than that value.