Theoretical and numerical investigation of workpiece jamming in fixture using block and palm case study

Jamming is defined as sudden and unwanted immobilization of workpiece during its loading/unloading into the fixture. Investigation of workpiece jamming in fixture and prediction of its occurrence during fixture design process may induce to modification of the fixturing plan, reduction of the fixture fabrication costs and decreasing of the jamming-related consequences. The present study focuses on the numerical investigation of workpiece jamming in fixture using block and palm case study and comparison of its results to the theoretical predictions. For this purpose, numerical analysis of block and palm case study is conducted using Adams® software. Results of numerical analysis represent that jamming is occurred for block by traveling of distance equal to 0.754 on the horizontal surface. Numerical results are compared to the theoretical predictions. Theories for prediction of jamming incorporate two main methods; first, development of dynamics equation for calculation of velocity and acceleration at the contact points and second, the minimum norm principle. Agreement of the numerical results to the predictions of the first-category theoretical analyses (calculation of the velocity and acceleration at the contact points) confirmed the accuracy of the numerical results. Also, effects of the parameters including coefficient of friction between the workpiece and base plate, angular velocity of palm and mass of block are studied on the block’s jamming distance.