SYNCHRONIZED CABLE CUTTING AND BEADING PROCESS (02-Feb-2010)

            Some medical devices include cables that are formed from a number of individual wires.  In some instances, the individual wires are arranged parallel to each other while in other instances, the individual wires are wrapped in a helical fashion.  In some instances, a cable may include a core formed from a number of wires arranged in parallel fashion and an outer layer or layers formed from a number of wires that are helically coiled around the core.  In some instances, the cable may be encased in a polymeric material.

            In some instances, at least one end of the cable is further processed to include a bead that covers all of the individual wire ends in order, for example, to provide corrosion resistance and to facilitate subsequent processing steps such as extending the end of the cable into or through other structures to which it will be attached. In some instances, a cable such as an implantable cardioverter defibrillator (ICD) cable may be formed from a number of individual wires having silver cores with MP35N cladding.

            In some instances, cutting and beading may be accomplished in a single step. As shown in Figure 1, either end of a coated cable 10 may be fitted into collets 12 and 14.  In some instances, such as that illustrated, the left hand collet 12 may be stationary while the right hand collet 14 may be subjected to a spring force to exert a tensile force on the cable 10 to be processed.  In some instances, a spring 16 (as illustrated) or a precision frictionless air cylinder may be used to provide an appropriate force to the cable 10.  If the applied force is too low, the cable 10 may melt and resolidify without being cut into two pieces.  Alternatively, if the applied force is too high, an irregular-shaped bead may be formed.

A laser beam 18 may be applied to a desired location on the cable 10 between the left hand collet 12 and the right hand collet 14.  The laser cuts an uncoated portion of the cable 10 and forms the bead.  In some instances, during the laser beading process, the MP35N material can flow and at least partially coat the silver wire cores.

In some instances, the cable 10 is tilted at an appropriate angle during laser processing such that gravity and the viscosity of the molten material form a desirably shaped ...