Wiring Harnes News Nov-Dec 2021 - Page 31

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Altering Design Parameters to Strip Fluoropolymer Cable Jackets

By Dick Chen Aerospace Wire & Cable ___________________________

As all we know , it can be quite difficult to strip fluoropolymer cable . It has excellent insulative properties for many applications , but its slippery nature makes it a challenge to process .

Generally speaking , you need to purchase an expensive , specially designed and very expensive piece of equipment to do the job without damaging the insulation ( Fig 1 ). It ’ s an even bigger challenge in long-run and second-end terminations in an aircraft or in the field , such as a fire alarm system . It is time consuming and mistakes will be costly .
Most people don ’ t realize that producers of wire and cable can control some of the parameters in the manufacturing process to meet the needs of specific customer applications , thus reducing the effects of these stripping challenges . Sadly , not all manufacturers are willing to work with customers to produce these custom solutions .
As a fluoropolymer cable manufacturer , Aerospace Wire & Cable has long carved out a niche in the industry with their willingness to produce custom extrusion solutions to meet specific industry and customer needs . If , for example , the customer can specify the maximum force required to pull the jacket off at a certain length ( four inches long with maximum one lb . of force ), they can do their best to produce a more suitable product .
Here are some of the engineering procedures they can tweak to improve the stripping characteristics of fluoropolymer cable jackets .
1 . Design the extrusion die and tip to get Draw Ratio Balance and Draw Down Ratio *. Typical draw ratios for Fluoropolymer are 50- 150 with special techniques is > 150 . Draw Ratio Balance ** shall always keep as 1 .
2 . Set up proper extrusion parameters for process temperature , extrusion speed , cooling distance etc . depending on different Fluoropolymer .
3 . Select suitable Fluoropolymer for easy strip . For example , Harlar is easier to strip than FEP .

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Figure 1 . Damaged or Nicked Insulation
4 . Add high temperature ripcords or tapes to facilitate an easier strip . ( Fig 2 , 3 page 34 )
5 . Design the cable configurations to facilitate an easy strip . They do this by offering a different lay for the wire pairs , or by using a different type of cable to enhance roundness .
There are many considerations to design a cable for different purposes . Some end users want the jacket to be loose , others want it to be tight . If a fluoropolymer has been selected for the jacket material , ease of the stripping process will be one of the main parameters for a qualified engineer to consider .
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