Flexible Wire- Conductor and Insulation selection for flexible wire and cable

Medical device, aerospace and automation manufacturers often require flexible cables for their products. Flexible wire and cable can have many interpretations. Sometimes a simple description such as, “the wire needs to be as limp as a wet noodle” is enough to understand your needs. The choice of type of conductor and insulation can greatly influence the flexibility of the cable performance. Understanding what the flexibility requirements are will help to determine the materials and construction for the flexibility of the wire or cable.

When specifying a flexible cable you need tell your cable manufacturer what the intended use will be.

• Do you need to route it through equipment or a tight space?
• Will it be subject to repetitive flexing?
• Do you need the cable to flexible during use?

There are several factors which make a cable flexible, a few are:

• Conductor stranding
• Shield types
• Cable lay
• Insulation materials.

Typically in conductor stranding, the more strands a conductor has the more flexible the wire will be. Normally “off the shelf” wire and cable is stranded in 7 or 19 strand configurations, is not flexible enough for most applications requiring flexible or high flex cycles. The general rule is the higher the strand count of the conductor, the more flexible the wire or cable will be. Stranded conductors are composed of un-insulated “strands” of wire twisted together. The advantages of stranded conductor over a single strand are increased flexibility and flex-fatigue life. When you see 22AWG (19/34) for example, what the description means is that there are 19 strands of 34 AWG making up the 22 AWG conductor. Other common options for a 22 AWG is a single strand (solid) up to 168/44 strands. The construction of the conductor also plays a role in the cable’s flexibility, for example a rope stranding is the most flexible. For repetitive flexing applications such as robotics and automation, the use of high strand alloy material is recommended.

Choosing the right insulation can add to the cable’s flexibility. Silicone is one the most flexible of the compounds used. Silicone wire is used to meet a variety of demands such as extreme high and low temperature requirements, flame resistance, flexibility, strength and purity. The application and environment also play a role when choosing jacket material. Harsh environments, chemicals, and abrasion will narrow down your insulation and jacket options. Discussing your flexible wire application with a cable manufacturer can help you choose the right materials for the performance and longevity of your product