Curve Precision Explained
Every CAM program turns curves into a series of short straight segments, because that is what a machine executes. Curve precision is the length of those segments, and it is set per operation.
Where it is
The Curve precision section appears at the bottom of every operation window: contour milling, pocket machining, contour engraving, area engraving and contour cutting.
It is a single field, in the current document unit. A default value can be stored in the postprocessor, under the default values section, so new operations start from a sensible number.
What the value means
It is a length, not a percentage or a quality level.
A larger value produces longer segments. Fewer points, a smaller program, faster generation, lower accuracy on curves.
A smaller value produces shorter segments. More points, a larger program, slower generation, higher accuracy.
Straight lines are unaffected. A rectangle produces the same program whatever the setting, because there is nothing to approximate.
Where it becomes visible
On a large shape, a coarse setting is invisible. The segments are far shorter than anything the eye or the finger can detect at that scale.
On small work it is obvious. At 4 mm cap height, a coarse setting shows as flats on every round stroke of every letter. The lettering looks faceted rather than smooth, and no amount of adjusting feeds and speeds will fix it, because the toolpath itself has corners in it.
This is why the setting is per operation rather than global. The fine lettering on a plate and the outline of the plate itself have completely different requirements, and forcing both to the same value either wastes program size or spoils the text.
Picking a value
Work back from the size of the smallest feature that has to look smooth.
For fine engraved text, a value well below the width of the thinnest stroke. For a large contour cut, something considerably coarser is fine.
If you are unsure, err on the fine side and check the program size. A larger file is a cheaper problem than visible facets.
Seeing the effect
Generate the program and look at the 3D view in the NC program section. The third icon on the right of the panel shows or hides the node positions.
With nodes visible, the segments are laid out plainly: far apart at a coarse setting, dense at a fine one. Zoom in on a curve to compare.
What it does not affect
The accuracy of positions. Straight moves and coordinates are unaffected.
Circles and arcs in your drawing. Whether they can be output as arcs depends on the postprocessor and the controller, not on this setting.
Machine speed directly. More segments mean more lines for the control to process, which on a simple controller can slow motion on curves. On a control with good look-ahead this matters much less.
The practical rule
Set it once for each kind of work and store the value in your default settings so it starts where you want.
Then adjust only when a job differs: finer for small lettering, coarser for a large rough cut. Treating it as a per-job decision rather than a fixed setting is where the benefit is.
A note on program size
On very fine settings applied to large amounts of curved geometry, programs can become long enough that generation takes noticeably longer and older controllers struggle to read them at speed.
If a program is unexpectedly large, this setting is the first place to look.