Wiring Harness News Sep-Oct 2022 - Page 27


Processing Electric Vehicle Heavy Cables

Continued from page 25 ____________ there is synergy between them . The size of these wires requires hundreds of filaments to make the conductor core . As we all know , tightly twisted cores require more material per inch as compared to loosely twisted cores . For this reason , these wires contain “ bunched ” filament cores . Bunched cores are notoriously prone to uneven concentricity . They have peripheral filaments located either by themselves or in bunches away from the apparent core periphery . In order to avoid cutting or damaging these “ satellite ” filaments , the operator may sometimes limit the penetration parameter of the tangent rotary blades . This action creates a significant area around the core which is not physically separated from the insulation ’ s cross section . Even if allowing the operator to cut through the satellite strands , there still is an untouched cross section leftover around the remaining peripheral strands which is still attached to the rest of the insulation sleeve ( Figure 5 ).
it more difficult to cleanly dislodge the slug . Pulling against the material “ unravels ” the polymer molecules and extends the length of the material while reducing its cross section . When the elastic material gets close to its failure or rupture point , the polymer chains increase their resistance to the point that you need to exert added force to overcome the molecular resistance to split apart . The elongation limit of the material is dependent on its composition but an elongation of 115 % ( my own experimenting with a physical sample of an insulation section ) at resting length is very possible .
Elastic attributes , thermal .
Rubbery materials present a particular reaction to heat . Increases in temperature cause polymer molecules to compress and loss of heat loosens the molecular structure . I am not knowledgeable on the exact methodology used to manufacture these wires , but I would assume that


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Figure 5 . Closeup showing attached cross section insulation elastic strands being pulled in the stripping action .
Elastic attributes , mechanical .
Some elastic materials are made out of randomly oriented cross-linked polymer chains such as the model depicted in Figure 6 . The mechanical and thermal characteristics of these types of plastics inherently work against the slug removal process . In mechanical terms , pushing against the material compresses the polymer molecules . This action increases the wrapping force exerted on the underlying conductor core thus making considerable heat needs to be applied to the raw plastic material in order to make it fluid enough for the extrusion process . I would further assume that ( because of the heat ) the extrusion process deposits compressed polymer chains around the core periphery , forming the insulation cover . The resulting product is a wire which ultimately presents an insulation sleeve exerting some de-
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TTI and the experts at TE Connectivity ( TE ) understand the unique challenges of working with Hybrid & Electric Mobility Solutions ( HEMS ) cables . Knowing the potential problem areas can help wiring harness manufacturers address issues before they begin to impact project outcomes .
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Figure 6 . Model of cross-linked polymer chain molecules .
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