In general, the planning information of bending machine is to show the drawing data of pipe fittings by the coordinates of the connecting points on the drawing, while the numerical control system in CNC bending machine processing needs not the coordinate data of connecting points, but the incremental tube shape data dedicated by the numerical control bender.
Therefore, it is necessary to convert the pipe shape data from the drawing or the positive coordinates of Cartesian coordinate system to the incremental pipe shape data before machining the bend pipe.
The bending machining is different from the general cutting machining, which uses vector bending machining skills. Vector elbow is based on vector theory, which regards pipe fittings as a series of straight lines and arcs.
In the Decard coordinate system, the center line of the straight segment of the pipe fitting is indicated by a series of space vectors. Firstly, the coordinates of each intersection point are obtained, that is, the coordinate values of the connecting points on the bending drawing. Then the basic concept and operation law of vector are used to calculate the theoretical incremental data of pipe shape, namely the machining data of pipe fitting bending. The machining data of the pipe fitting bend was input by numerical control machining program method, and the system corrected it by "springback". Finally, the controller executes the corrected pipe fitting bending processing data to control the three-dimensional space pipe shape required by the bender for active bending processing.