A programming term for CNC tube-bending machines referring to the basic elements of motion which must be programmed into the machine’s controller to bend a tube. The elements of motion are:

transport — Y-axis motion, which is the forward and backward linear movement of the tubing material relative to the line of tangency.

plane of bend or orientation — B-axis motion, which is the rotation of the tubing material about the Y-axis.

degree of bend — C-axis motion, which is the rotation of the bend die.

These bend data do not technically constitute a polar coordinate system, but there are to be contrasted with the XYZ rectangular coordinates commonly used in the automotive industry to specify tubular components. The difference is that rectangular coordinates specify the location of the bend, whereas bend data specify the motion needed to make that bend.