Three-dimensional tube geometry control for rotary draw tube bending, Part1: Bend angle and overall tube geometry control

Traditional trial-and-error springback compensation methods have the proble ms of high scrap rate, low efficiency, high cost of fixtures and operator e xperience dependency. The method presented in this paper uses on-line measu red springback data from the same batch to predict and compensate for sprin gback. Because there are no springback data for the first bend, bend-rebend control is used to make the first bend to eliminate trial tubes. In additi on to springback, relaxation and radial growth are also estimated and compe nsated for to make a bend more accurate. A process control method is develo ped to optimize the overall control strategy such that the overall tube err or is minimized without increasing the required hardware accuracy. The opti mal process control strategy has significantly higher accuracy than the tra ditional trial-and-error method. The details of statistical analysis of tub e tolerance and adaptive bend correction algorithm are presented in Part 2 of the paper.