In modern automated manufacturing systems, there is a need for
work-holding devices that provide for precision, accuracy, reliability,
flexibility and remoteness of control. One of such devices is the
diaphragm chuck which utilizes the strain energy of its varying thickness
diaphragm plate for gripping action. The jaw-carrying diaphragm
plate is deflected by a thrust load, and the jaws are bored or ground
to the nominal diameter of the workpiece. Gripping action occurs when
the workpiece is inserted into the jaws and the thrust is relieved.
Designers and manufacturers of diaphragm chucks have in the past
been limited to the use of empirical data for diaphragm chuck design.
This design limitation has been caused by complex problems due to factors such as the varying thickness encastre diaphragm plate, the
gripping couples and the stiffening effects of the jaw slides.
This work involved the establishment, by theory and experimental
verification, of the design and performance parameters of a diaphragm
chuck, and the provision of diaphragm chuck design methodology. The
designer is therefore able to achieve the a priori design of the diaphragm
chuck. In addition, the user is able to adapt existing diaphragm plates
to achieve required gripping forces within existing constraints.
The scope of this research is the static gripping action for
any number of symmetric jaws. The design method is for diaphragm plates
with small thickness taper, and carry detachable jaw slides.
The concept of the equivalent constant thickness is applied to the
diaphragm plate. Gripping action is divided into two major phases - the
separate deflections of the diaphragm plate by a thrust load and symmetric
couples. These deflections are equated to obtain the gripping force.
This research concludes that the gripping force of a diaphragm
chuck is closely predicted by the equivalent constant thickness method.
Design data and methodology are provided for diaphragm chuck design.
Thus, a designer can now design a diaphragm chuck based on a desired and
pre-specified gripping force requirement
