Modeling, analysis and performance optimization for material handling of compliant sheet metal parts

Material handling of compliant sheet metal parts is one of the most critical yet underresearched areas in the stamping process. Material handling systems for large compliant parts can significantly impact both part dimensional quality and production rate. The intrinsic cause is the compliance-induced sheet metal part deformation.; Currently, the practice of setting up and running material handling equipment is based on a trial and error method. There has been very little research completed concerning the material handling for compliant sheet metal parts. This dissertation develops a systematic methodology to model the material handling system, analyze its impact on the handled part deformation during the handling process, and optimize its performance as measured by part dimensional quality and transfer time. The methodology can be implemented into the design stage of a stamping line and serve as a guideline for improvement of part dimensional quality and production rate.; The systematic methodology includes: (1) Optimization of part holding end effector layout. This extends the design of “N-2-1” fixturing layout by adding part movability conditions and is realized by integrating FEA modeling of part deformation with an optimization algorithm. Experimental results verified the methodology developed. (2) Development of a dexterous part holding model. The model has the flexibility to reflect real characteristics of the vacuum cup type of end effectors. It advances the rigid point model by predicting part deformation behavior more accurately for different modes of part deformation and for the entire domain of part-holding end effector locations. A method for the model structure design is presented and an algorithm for estimation of the model parameters is developed. Experiments verified the validity of the development. (3) Time optimal trajectory planning for compliant part transfer. This development addresses an important research topic by considering the deformation of compliant parts in trajectory planning. Part deformation determined by transfer dynamic parameters is considered as a nonlinear constraint, which is obtained from FEA modeling and data processing. Part permanent deformation, trajectory smoothness, and static obstacle avoidance can also be handled. The methodology is validated by simulations in various motion conditions and obstacle configurations.