Wiring Harness News Sep-Oct 2021 - Page 41

structions . However , there are some basic steps that apply to almost all of them and these steps pertain to properly stripping the cable and loading the ferrules .
1 . Remove outer jacket & foil
Cables without a foil layer around the shield are naturally easier and faster to strip . These cables can be stripped with radiused fixed blades , rotary stripping blades , or a laser stripper .
Radiused fixed blades will likely be the fastest but perhaps not the safest for quality . If one blade is sharper than the other , the blades will not penetrate the insulation evenly and may damage the shield . If the cable is not very concentric , it is nearly impossible not to damage the shield . Finally , changing to a different cable size requires a blade size change as well .
Laser stripping is popular since there is no way to damage the shield because the laser beam is reflected off of the shield . However , if the shield is not woven tightly , the laser can penetrate the shield and damage the inner layers . Laser strippers require fume extraction since some fumes are toxic . They are also the most expensive , compared to other stripping methods .
Rotary stripping will provide the cleanest cut using blades and conductor detection systems that can prevent damage to the shield . Special processes can be used for non-concentric cables .
When the outer jacket is molded into the shield , it makes it more difficult to remove the jacket without disturbing the shield . For these cases , manipulating the slug in certain directions while pulling it off of the cable helps the slug break away from the shield .
If the cable has a foil layer , it must be stripped cleanly , flush with the outer jacket with no flags remaining . This is nearly impossible with fixed blades . It is certainly possible with a laser system unless the foil is bonded to the outer jacket . Laser systems require space for the laser to get to the foil . However , if the foil is bonded to the outer jacket , any pulling of the slug may cause the foil to tear unevenly . Furthermore , lasers will not cut where the foil overlaps .
With rotary stripping blades , it is possible to score the foil without pulling the slug . The jacket slug and foil can be removed simultaneously by manipulating the cable and twisting the slug as it is removed . The result is a clean foil cut that is flush with the outer jacket .
2 . Assembling the inner ferrule
Loading the ferrule onto the cable is critical but not overly challenging if done manually . However , as mentioned , different connectors use different ferrules . Therefore , it should be possible to change over to different ferrules with a few cable- and ferrulespecific parts . The system should also have the ability to detect if the ferrule is the correct type and if it is properly oriented on the cable .
Installing the ferrule onto the cable is a step that could be done manually to save costs since automatic loading systems are quite expensive .
3 . Cutting / removal of the shield
Properly cutting the shield consistently with a traditional rotary stripping unit is very challenging for HV cables especially if the cable has nonconcentric layers or is otherwise out-of-round . The integrity of the dielectric and filler are critical for proper performance of the cable and traditional rotary stripping machines risk damaging the inner layers . An anvil and punch system guarantees the inner layers will not be damaged and cuts the shield cleanly and evenly , 360 ° around the cable .
The resulting shield length will depend upon the ferrule being used since it will be wrapped around it . The cut must be clean and consistent , otherwise long strands may cause shorts with other components and short strands may degrade the integrity of the ferrule crimp .
Sometimes the shield length is longer than the length of the dielectric . These applications require that the shield is opened and folded back after it is trimmed so that the inner layers can be stripped .
4 . Fold shield
The shield gets folded back over the ferrule but in some cases , not completely . Different connectors require different fold angles to ensure the connector fits together properly . The fold angle may be between 90 ° to 180 ° but the fold must be even , 360 ° around the ferrule . The shield strand ends must fall within the specified tolerances to ensure proper performance . Strands that are too may cause shorts and short strands might not secure the shield properly when the outer ferrule is crimped .
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