Give it the tube OD, the centerline radius (CLR), and the X-Y-Z coordinates of each bend point from your drawing — it returns the cut length, every bend angle, each arc, and the roll rotation between bends. Or use the quick single-bend check.
Bend angle is the included angle between legs (as drawings usually call it); DOB is the degree the machine bends through (180° − included). Rotate is the roll about the tube between one bend plane and the next. Springback is not applied — overbend per your own test bends. Material stretch uses the factor you enter above.
A rotary-draw bent tube is defined by a series of straight segments joined by constant-radius arcs. This calculator takes the node points of the tube centreline — the X, Y, Z coordinates read straight from the part drawing — and returns the two numbers a fabricator actually needs at the machine: the developed cut length of the raw tube, and the bend procedure (bend angle and rotation at each station).
The flat, uncut tube is longer than the sum of the straight legs because each bend consumes material around its arc. For a bend of included angle θ (degrees) at centreline radius CLR, the arc length contributed is CLR × θ × π / 180. The developed length is the sum of every straight run plus every arc length. Because this tool measures the centreline, the arc term uses CLR directly — there is no separate bend-deduction or setback table to look up, and no K-factor approximation, which is where flat-pattern sheet methods introduce error. The result is exact for the geometry you enter; the only real-world correction is tube stretch, which the readout flags separately.
Most shop bend calculators ask you to enter bend angles and straight lengths that someone has already extracted from the drawing by hand — a step where transcription errors and sign mistakes creep in. Entering the node coordinates directly lets the tool derive the bend angles and plane-of-bend rotations itself, from the same numbers the CAD model exports. Three consecutive points define one bend; every additional point adds one more bend. This is the same coordinate data the XYZ–to–YBC converter turns into machine feed/rotate/bend commands.
The geometry above is nominal. In production, elastic springback opens every bend by a small angle that depends on material, wall factor, and bend severity, and the tube stretches slightly on the outer fibre. Tooling and first-article correction absorb these; the calculator reports exact nominal geometry so your correction is applied to a known baseline, not stacked on top of an approximation.