Cutter radius compensation

When you program a part on a lathe, you program the finished surface — the actual part dimensions. But the cutting tool has a nose radius, so the tool tip follows a slightly different path than the one you programmed. For straight cuts the error is negligible, but on tapers, radii, and contours it adds up fast.

Cutter compensation handles this automatically. Program the part geometry. The FluidBoard offsets the tool path by the nose radius for you.

This is standard practice on industrial lathes. On most hobby controllers, it simply doesn't exist.

How it works

Enable compensation, and the controller shifts the tool path perpendicular to the cutting direction by the tool's nose radius (looked up from the tool table):

• G41 — compensate to the left of the programmed path
• G42 — compensate to the right
• G40 — cancel compensation and return to the programmed path

T1 M6                  ; Load tool 1 (radius 0.4mm from tool table)
G43 H1
G42 D1                 ; Right compensation using tool 1's radius
G1 Z0 X20 F0.1        ; Cut — path is offset by 0.4mm automatically
G1 Z-30
G1 X25
G40                    ; Cancel compensation

The D word selects which tool's radius to use. Omit it or use D0 for the current tool.

When to use it

Cutter comp matters most on profiles with curves and tapers. On a straight facing or turning cut, the nose radius has minimal effect. But the moment you cut a taper, a radius, or a contour, the error from the nose radius compounds — and compensation eliminates it.

Corner handling

The controller handles corners automatically:

• Outside corners — a smooth arc is inserted to round the transition
• Inside corners — the controller calculates the correct intersection point

Supported planes