Modeling of the holding force in an electromagnetic chuck

This paper addresses the modeling and prediction of the normal holding forc e in an electromagnetic chuck used in precision machining applications. Kno wledge of the normal holding force is necessary to determine if a given chu ck is capable of preventing workpiece slip during machining. First, an anal ytic model termed the magnetic circuit model was developed and compared wit h experimental holding force data. It was found that this model, although s imple in form, was limited in its ability to accurately predict the holding force over the entire range of conditions investigated. The discrepancies in the model were attributed to its inability to accurately model the leaka ge flux and nonuniform distribution of the magnetic flux. A three-dimension al finite element model was then developed to overcome these limitations. P redictions with this model were found to be in better agreement with experi ments, yielding prediction errors within 25 percent in most cases. The fini te element model also provided an explanation for the observed decrease in the measured holding force at current values beyond a certain threshold. [S 1087-1357(00)01503-3].