Arcs change to short line segments

[ger21]

That's why they have both "Draw Arc" and "Draw Curve" commands.

[Renaissance]

I appreciate all of your thoughts on this.
All of the arcs created in this project were created from a straight line segment, then when in node editing mode, the line segments were changed to arcs. The arcs radii were then adjusted dynamically with the node on the arc radius.

[ger21]

Then they are not arcs. Node editing results in Bezier curves, not arcs. Bezier curves always translate to straight G1 moves, unless you fit arcs the the curves.

[LittleGreyMan]

All of the arcs created in this project were created from a straight line segment, then when in node editing mode, the line segments were changed to arcs. The arcs radii were then adjusted dynamically with the node on the arc radius.

Do you have a particular reason to follow this process?

You cant convert a bunch of segments to arcs in a single command with the "fit curves to selected vectors" feature.

[LittleGreyMan]

Good point Gerry, once you edit the nodes the curves are converted. This explains the phenomenon, but I'm still curious of the process.

[gregk]

Then they are not arcs. Node editing results in Bezier curves, not arcs. Bezier curves always translate to straight G1 moves, unless you fit arcs the the curves.

Node editing will not change arc segments to beziers, not when you only manipulate nodes. It will only happen if you make nodes smooth or explicitly convert segment to a bezier.

Greg K

[Leo]

Interesting

I created a circle again - same as before.

This time I changed the spans to bezier which changed the nodes into smooth nodes.

The g-code is now all G1 line segments.

There is always more to learn

[TReischl]

The secret lies in knowing what a bezier curve actually is. As someone mentioned earlier, it is similar to a spline, but it is not a spline.

Bezier curves are extremely useful for artistic work, splines not as much.

Internally a bezier curve is NOT a series of small line segments. It is nodes and control handles(points). The software that implements the bezier curve creates the number of small segments as output. In other words, the software "plots" the curve defined by the nodes and controls and outputs points along that curve.

Normally lots of small segments are not a problem on a cnc machine, unless you are running a really fast machine. If the control cycle loop time is longer than the time it takes to execute the commands the machine will start to stutter. I have run industrial laser cutters at high speed, think in excess of 800 IPM, and had them empty the look ahead buffer and begin stuttering because of very small short segments. The only solution is to convert those small segments into true arcs.

Most of us will never see that on our machines, so it is not a worry. I run my router at 250-300 IPM most of the time and have never had a problem.

Here is a link that explains it pretty well: https://en.wikipedia.org/wiki/B%C3%A9zier_curve

[gregk]

I gave it some more thought. If all the arc were changed, I think it is likely that following happened. The distort vector tool was used. When distorting arcs, they will change to beziers.
Afterwards, many operations (e.g. offsetting) will turn beziers into series of straight lines.

Have you used distort vector tool Renaissance?

Greg K

[Renaissance]

Hi Greg
Didn't use distort vector tool, just checked what that is.

[ger21]

What process or tools did you use to add the arcs?

[Renaissance]

All of the arcs created in this project were created from a straight line segment, then when in node editing mode, the line segments were changed to arcs. The arcs radii were then adjusted dynamically with the node on the arc radius.

[ger21]

then when in node editing mode, the line segments were changed to arcs.

How are you changing them to arcs?

[Adrian]

Only way I've been able to replicate something similar that could catch someone maybe unaware is to create a drawing with arcs (I used the A shortcut in node edit to convert spans to arcs), resize in one direction (easy to do by accident with a drag handle), obviously arcs can't then be maintained so they are converted to beziers which look very similar. At that point an offset operation or some other operation would cause the beziers to be replaced by lots of short spans.

Similar to what Greg suggested with the distort tool but it's something that could happen with the user being unaware.