VTube Reverse Calc from MIL-D-9898C Absolute Bender Data to Centerline XYZ Data

This military spec bender chart data chart can converted by VTube-STEP and VTube-LASER in the LRA grid section of the Part Data menu. (As of Version 2.7) This specification was created decades ago when CONRAC benders were popular with the military. CONRAC benders have been obsolete for decades, but legacy tube shape data is still maintained with this specification.

General Principals for the Military Specification

This bender data spec uses ABSOLUTE LENGTHS between bends as if they were derived from a tape-measure attached to the Feed axis of a bender. CONRAC benders had tape measured riveted along the rail of the carriage that moves along the length of the bender. The lengths indicate where each bend begins. The bender data uses ABSOLUTE ROTATION data (twist angle between the planes of the bends). It is absolute because it always depends on the rotations in all preceding bends accumulated. The dial on an absolute rotation spindle reads from 0 to 360. The dial puts all rotations at the top of the dial. It starts with "0" at the top of the dial. Although it seems to be ambiguous in the specification, most military prints assume DRAW bending versus COMPRESSION bending - which means the LENGTH values move the carriage so that the tube is positioned at the start of each bend (for clamping and drawing around the die) rather than the end of each bend (for clamping with rollers or wipers and compressing around the die).