Nowadays it is a very effective method using numerical simulation technology combined with robust optimization technology to solve the forming quality stability problem in mass production condition. Using these two techniques, the robust optimal technological parameters for multi-process hydroforming of a tubular sub-frame were obtained. According to the sensitivity analysis, the key process factors which influence the thinning rate of the tubular subframe are: velocity of the pressure die, lubrication coefficient in bending process and max pressure in hydroforming. The optimization result of the key process parameters that influence the thinning rate of tubular sub-frame was given by means of robust optimization technology.

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