Super Flexible Wire Designs: High strand count conductors

A super flexible wire design requires two things, a flexible insulation material and the right conductor stranding. Even with the most flexible wire insulation, the flexibility of the wire will depend on the conductor stranding. Conductor construction is key in achieving a noodle like flexible wire. There are two things to look at when choosing the right conductor:

1. Number of strands. Conductors are made of many fine strands which are cabled together to meet the required gauge size. Conductor stranding is available from one strand (solid) to hundreds depending on the gauge size. The higher the strand count the more flexible and resistant to flexing fatigue the wire will be. For example a 24AWG wire the stranding options are from 1 strand (solid) all the way to 105 strands. That’s quite a range.

2. Conductor construction. How these fine strands are put together is as important as the strand count. The most common configuration is concentric. Concentric conductor may be defined as: a central wire (strand) surrounded by one or more layers of helically laid wires in a geometric pattern. Rope stranding has the advantage of increasing flexibility by using a larger number of finer strands while maintaining a tighter diameter tolerance than a simple bunched construction.

Flexing vs. Flexibility

High Strand Silicone Wire

To some flexibility means to withstand repetitive flexing, while to others it means how much the wire will bend and rigidity. For both types of applications a high stranded conductor is recommended. For repetitive flexing one should consider using an alloy material for higher strength and flex cycles. For noodle like flexibility a standard copper conductor is fine.

Flexible cables

Flexible cables also use high strand conductors, but there are more factors involved controlling the flexibility; Such as, Shielding, outer jacket material, cable lay construction and type of conductors just to name a few.

It's always best to discuss your flexibility needs and the conductors available with a wire and cable manufacturer, especially one that works with high strand count conductors. Off the shelf (commodity) wire manufacturers usually work with solid, 7 and 19 strand conductors which are less flexible than the high strand conductors.

Silicone Cable- 5 Things you didn't know about Silicone Wire

Silicone wire is extremely flexible and resistant to high temperatures, everyone knows that. There are some misconceptions regarding silicone wire and silicone cables. Listed below are five facts you probably didn't know about silicone insulated wire that I get asked frequently.

1. It doesn't have to be tacky. Recently at a trade show I handed a visitor a sample of our silicone wire and he said: "Wow, this isn't sticky, we stay away from silicone because it's always sticky." Silicone rubber is normally tacky, this can be a problem especially in medical applications where you don't want dirt sticking to the cable. Silicone cables can be made so they are not tacky or sticky. This is accomplished with manufacturing techniques and formulas can be used to make the jacket smooth and not tacky. Normally silicone wire and cable is coated with Mica to keep it from sticking to itself during the manufacturing process, this coating is not acceptable in some applications that requiring clean environments. The alternative is to manufacture the silicone so it is not sticky from the start.

2. Available in ribbon cables. Silicone cables can be manufactured as ribbon cable a few different ways. Silicone ribbon cables can be extruded, bonded and even molded into ribbon and flat cables. Silicone ribbon cables can be extruded as a ribbon cable which offers the tightest center to center tolerances. Bonding the ribbon cable involves extruding the individual silicone wires separately then they are bonded together, this method is less expensive than extruding the ribbon cable because there isn't any additional tooling. Bonded silicone ribbon cables work best with IDC connectors and soldering. Molded ribbon cables are usually silicone wires encapsulated with a silicone outer jacket, this method allows for unique flat shapes.

3. Low outgassing formulas are available. Aerospace, specifically space applications often have outgassing restrictions for the wire and cable. Recent advancements with silicone formulas and manufacturing techniques have created low outgassing silicone cable. For space craft and satellite applications Calmont manufactures silicone wire and cable products which meet NASA .01% TML requirement. Depending on your outgassing requirements, check with your silicone cable manufacturer to find out what is available. Click here to view Aerospace insulation properties chart.

4. Reinforced silicone is available. High strength silicone formulas are now being used to increase abrasion resistance of silicone wire and cable. Fluorosilicone has better abrasion resistance than the standard silicone. Additional measures can be taken to reduce abrasion such as strength members between layers and nylon outer braid to protect the silicone insulation.

5. Doesn't burn. Silicone insulation is self extinguishing, it will not burn. Flame retardant additives can be added to meet flame requirements such as VF1

Medical Cables Choosing the Right Materials for Medical Cables

Medical cables are manufactured in a variety of materials. Knowing which type of medical grade insulation or jacket material to choose from medical cable manufacturers is important. Before designing a cable, you need to answer these basic questions:

• Is the cable disposable or reusable?
• Will there be patient contact? Bio-compatibility requirements?
• Will the cable be sterilized? If so how?

§ Flexibility requirements?

§ How will the cable be used?

Medical cables fall into two categories, reusable and disposable. Disposable one patient use cables are normally made of less expensive material such as PVC and are not subject to repetitive sterilization due to short term use. Reusable cables often times have to withstand many cycles of sterilization such as, autoclave, gamma, E-Beam, and chemical sterilization. Knowing how the cable will be sterilized is important in order to narrow down your jacket options as some materials will break down or can’t withstand certain types of sterilization.

Medical grade insulation and jacket materials differ depending on the type of contact it will have with the patient. Implantable grade insulation materials are usually Teflon or silicone rubber. Common jackets are silicone rubber or implant grade Polyurethanes. For other uses medical grade materials include PVC, TPE, polyethylene, FEP, PFA, and polyurethane.

Medical cables application and use vary from sensors to complex surgical devices. Relaying this information to your cable manufacturer is important. Cables can be subjected to repetitive flexing, abrasion, getting stepped on or rolled over by carts. Choosing a material that can withstand the day to day use will prolong the life of the cable.

The aerospace industry has applications which can be very critical of weight

The aerospace industry has applications which can be very critical of weight; Such as, missiles, rockets and satellites. When looking for ways to cut down equipment, payload, or satellite weight, the cable can be the last thing considered. One way to accomplish weight reduction in aerospace cables is to use metal clad aramid fibers for the shield and braid material instead of the standard copper. Aracon® is one such material which provides exceptional EMI shielding, strength and flexibility. Typically Aracon® fibers can reduce weight 60% in the braid, an overall reduction in cable weight of 26% on the average. Aracon® is combined with DuPont Kevlar® to provide high tensile strength and excellent conductivity. The large number of fine threads and the tendency of yarn to flatten and spread give this material more shielding coverage than copper. In the first photo you can see the amount of fibers on the end of the braid

Benefits for switching from copper braid to Aracon include:

• Overall cable weight reduction
• Added flexibility
• Increased strength
• Withstands repetitive flexing
• Improved EMI shielding coverage

Aracon® fibers are manufactured by only one company Micro-coax Inc. The Aracon® braid can be purchased either with the braid only (sock) or having the braid manufactured onto cables by cable manufacturers such as Calmont Wire & Cable. Calmont has had great success manufacturing cables using Aracon® for the space and military related applications.

The cost of using this type of material is considerably more expensive than the standard copper braid. The cost savings for applications such as satellites where weight savings equate to rocket fuel cost, definitely makes it a value. Depending on your shielding requirements, Aracon® is available with several metallic coatings, thickness and fiber sizes to meet your resistance needs. Consult your cable manufacturer or Micro-Coax for options available to you.

If you would like to learn more about EMI shielding, Aracon® or similar materials contact Calmont today. Your comments are welcome and if you find this article useful, please share it.

ARACON® is a registered trademark of Micro-Coax, Inc. KEVLAR® is a registered trademark of E.I. du Pont de Nemours and Company

Conductor Stranding: How important is it?

Conductor stranding can be a bit confusing. Wire and cable is manufactured in a variety of configurations, not all wire is the same. The conductors for wire (aside from solid core) are made of multiple strands of fine wire bunched or twisted together. Conductor stranding plays an important part of the flexibility and the performance life of the wire. The more individual wire strands in a wire, the more flexible, break-resistant and stronger the wire is. Hi flex applications where repetitive flexing is required use different stranding than wire used to wire a building or home. "Off the shelf wire normally is available in solid, 7 strand and 19 strand constructions which is fine for applications not requiring flexibility or repetitive movement.

Repetitive flexing can cause conductor strands to break over time which lowers the conductivity of the wire. Using higher strand wire helps eliminate this problem. High strand wire is used in medical handheld devices, robotics and even headphones.

Many custom wire and cable manufacturers offer high strand wire which you cannot obtain easily from distribution. For example, a 20AWG wire can be manufactured with a solid conductor or solid core all the way to 168 strands. Knowing which conductor stranding option will best suit your needs is important.

Identifying the conductor call out: A typical call out is XX (YY / ZZ). The "X" is the gauge of the wire, "Y" is the number of strands and "Z" is the gauge size of those strands. Once you understand what these numbers mean, identifying the conductor construction is simple. A wire gauge chart is a handy tool to view wire gauge stranding options

The more common conductor stranding configurations are concentric (true concentric, equilay concentric, unidirectional concentric, and unilay concentric), bunched and rope.

Rope stranding is conductor construction consisting of single strands assembled together into concentric or bunched configurations. Rope constructions consist of concentric or bunched members stranded together into the final concentric or bunched configuration. Rope stranding has the advantage of increasing flexibility by using a larger number of finer strands while maintaining a tighter diameter tolerance than a simple bunched construction. Ropes are more evident in the larger AWG sizes, such as 8 AWG and larger, but there are also many applications that require the flexibility of rope constructions in the smaller gauges. Constructions vary and can contain hundreds or thousands of strands.

Depending on the use, the type of conductor is important. Hi flex and load bearing applications would require conductors with higher tensile strength such as alloys. Copper conductors are normally for less rigorous flexing

Flexible wire is a term which can be interpreted in many ways from hi flex to the actual flexibility of the wire. Letting your cable manufacturer know what your expectation is for the flexibility of your wire or cable will help in choosing the right conductor stranding. Calmont has manufactured extremely flexible large gauge wire and cable as big as 4/0 which is limp and flops over the end of a table. Of course insulation and jacket material also plays an important role in making a flexible cable, but the conductor stranding is where you start

Medical Cables: Often Overlooked

Medical cables are as important to a medical device as the device itself. Medical device designers many times focus on the device and overlook the wire and cables that is needed for the device to perform its function. Medical cables tend to be more specialized due to the many types of uses and environments it is subjected to. The wire and cable is many times not thought of until the end of the design process, which may be too late. Knowing your medical cable limitations and the options available to you in the beginning is important especially when designing housing or specifying connectors. Some things to keep in mind when specifying wire and cable for a medical device:

• Size- With the size of devices becoming smaller many times smaller gauge wire and cable is needed. Off the shelf wire and cable usually go as small as 28AWG. Fine wire and custom cable designs are usually needed.
• Flexibility- Handheld devices and medical robots require flexible cables which can withstand repetitive flexing. Higher stranded conductors and sometimes alloys are needed to achieve this.
• Sterilization- Sterilization can be done with alcohol, steam or gamma to name a few. Cable jackets need to withstand the sterilization process.
• Bio-compatibility- Medical grade cables are needed depending on the level of contact with the patient. Bio-compatible and implantable grade compounds are available for medical devices.
• Construction- Cables sending signals, power and even gas/fluid can be constructed in on jacket. Constructions can vary from the simple wire to complex hybrid cable.
• Unique- Medical devices are all unique in regards to application, requirements and environment. You should not use an off the shelf mass produced cable designed for to meet the generic needs of a variety of industries for a specialized medical device.
  

Considering your wire and cable needs from the early stages of your product design will prevent problems down the line in regards to failures in the field, design issues and time constraints. Designing custom medical cables for your application ensures you have a medical device that will exceed performance and longevity you require.

Depending on the type of use a variety of medical grade insulation materials are available. Reusable medical cables are built to endure constant flexing and extended cycles of sterilization. Insulation may be Teflon®, TPE or silicone rubber with TPR or silicone jackets. For disposable medical cables PVC and PE are the insulation most commonly used. Discuss your application with your custom cable manufacture in order to choose the right material for your medical device.

Working with a custom wire and cable manufacture is easier than you think. Custom wire and cable engineers work with you every step of the way to determine and suggest the best materials and construction for your medical application. It's like having a wire and cable expert on your team. Cable designs are usually modified throughout the design process to accommodate changes to the device design. Many custom wire and cable manufacturers are able to produce small quantities for prototypes and clinical trials.

Silicone Ribbon and Flat Cables: More Flexibility

When you think of extremely flexible wire, silicone insulated wire comes to mind because of its flexible properties. But what about using silicone in ribbon cable? Manufactures turn to silicone ribbon cables when applications require flat cables with specialized requirements or extreme flexibility. Flat cables and ribbon cables are often used when space is a factor ribbon cables can also be easily mass terminated using

an insulation displacement connector (IDC). Ribbon cables are manufactured in a variety of materials and configurations including silicone; the most common and least expensive insulation is PVC.

Space is a luxury as devices become smaller. Manufacturers are using flat and ribbon cables for more applications.

Industries include:

Aerospace
Automation/Robotics
Medical
Industrial
Automotive
Telecommunication

These types of applications often need insulation materials other than PVC due to special requirements such as extreme temperature, low smoke, flammability, flexibility, sterilization and chemical contact. Silicone is an excellent choice for these types of requirements. Not only is silicone wire extremely flexible, it can withstand millions of flex cycles, and has good steam and chemical resistance. Silicone ribbon cables can be extruded or bonded depending on the type of termination that is used. Extruded ribbon cables have a tighter center to center tolerance than the bonded ribbon cable. When using a bonded ribbon cable, terminating with IDC is recommended. Extruded ribbon cables normally require tooling to control shape and pitch which may add to initial cost. Bonded ribbon cables normally do not have special tooling used.

Flat cables can be manufactured in a variety of constructions which may include zip cords, ribbon cables and flat cables with an outer jacket. Custom cables can also be constructed with shielded twisted pairs, overall shield, and with tubing or lumens. Custom flat cables are also available in smaller gauges which you cannot find "off the shelf".

Silicone insulated wire and cables do have their drawback. Silicone has poor abrasion resistance, which can be a critical problem for applications where the cable comes in contact with sharp objects. Higher abrasion resistant formulas are available for silicone. Consult your wire and cable manufacturer regarding your application to find out the options available to you.

To find out more about flat cable options or if silicone cables are right for your application contact Calmont for assistance with your design or request a quote. Feel free to leave a comment.

Silicone wire: Art Using Custom wire and Cable

Custom wire and cable in art? One usually doesn't think of custom cable and art. From time to time we are contacted by artists looking for custom wire and cable for their art projects which are usually in the way of sculptures. Often times the custom wire is part of the art piece. In 2007 Claude Zervas an artist in the Seattle area needed an extremely flexible wire for an electronic art piece he was working on. The flexible custom wires needed to be placed in a way to be aesthetically pleasing and not to take away from the art piece as the wire becomes a part of the art.

"Since the wire is often exposed and becomes a formal part of the sculpture it needs to have certain physical properties such as color and flexibility. The high flex silicone insulated wire is perfect since it resists kinking and drapes like string or rope" says Claude.

His challenge was "off the shelf" wire was too stiff and could not be draped and arranged properly. The wire Claude chose is a silicone insulated wire with a high strand count conductor. This is an extremely flexible wire which was easy to incorporate into the art piece. Silicone insulation is used in a variety of industries and applications requiring super flexible wire, high voltage or high temperature.

The silicone wire was used in a sculpture commissioned by the King County Arts Commission for the exhibition hall at the Brightwater Treatment Facility (pictured on left). Happy with the performance and look of the wire, he has been using the silicone wire for other art pieces as well.

The photos below illustrate the layout and a close up of Claude's sculpture. The silicone wire plays a part in the design and function of the art piece.

"Diatomoton 5" The layout A closer look at Diatomoton 5

Here's a video of Diatomoton 5 in action:

About Claude

Claude Zervas' artwork uses technology and a variety of media to explore representation of landscape, social ecology, and memory. He creates 2D, 3D, and time-based work using video or custom computer programs. He has stated, “I grew up in a rural part of Whatcom County and I have been greatly influenced by the physical landscape, the social topology, and the transformation of this region. I am interested in how the idea of place evokes emotion, the way emotion affects memory and how memory in turn affects perception.”

After attending art school at Western Washington University Zervas fell into a career as a software engineer, eventually returning to art full-time. He leverages many of the skills acquired from his engineering experience to produce his art. Click here to see more examples of Claude's art.

If you have questions or an application requiring custom wire or cable contact Calmont for assistance. Please feel free to comment or share this article.

D5 from Claude Zervas on Vimeo.

Silicone Wire- Popular Applications of Silicone Insulated Wire and Cable

Silicone insulated wire is a popular choice for a variety of industries due to its operating temperature range, extreme flexibility, and voltage properties. Silicone wire and cable compounds are available in special grades and formulas are available for specific requirements such as, medical grade/implantable, low smoke/halogen-free, increased resistance to abrasion , flame retardant and more.

Silicone wire advantages include:

• Service temperatures from –50 to +200 °C
• Special grades are available for use in a temperature range from –90 to +300 °C
• Excellent aging resistance, even under extreme conditions
• High resistance to many different chemical substances
• Outstanding electrical properties
• Extreme flexibility

Aerospace

Aerospace and space applications often require low smoke halogen-free wire and cable. Silicone insulated cable can be manufactured with low smoke halogen-free grades. Low smoke halogen-free silicone cables offer several advantages over conventional cable products:

• Silicone does not emit any corrosive gases.
• Flame resistance - Ensures reduced flame propagation.
• Halogen-free cables generate little smoke, ensuring clear visibility during fires.

Commonly used Mil-Specs for silicone wire, is the MIL-W-16878

• MIL-W-16878/7 Wire, Silicone Insulated, 200°C, 600 Volts.
• MIL-W-16878/8 Wire, Silicone Insulated, 200°C, 1000 Volts.
• MIL-W-16878/29 Wire, Silicone Insulated, 150°C, 600 Volts.
• MIL-W-16878/30 Wire, Silicone Insulated, 150°C, 1000 Volts.
• MIL-W-16878/31 Wire, Silicone Insulated, 150°C, 1000 Volts, Glass Braid, Abrasion Resistant.
• MIL-W-16878/32 Wire, Silicone Insulated, 200°C, 1000 Volts, Glass Braid, Abrasion Resistant.

Other Mil-Specs using silicone insulated wires with FEP Jacket include MIL-DTL-8777, MS25471 and MS27110.

Medical Applications

Medical device manufactures use silicone insulated wire and cable because can be used in an autoclave, its chemical resistance and ultra flexible nature. Silicone is widely used in applications that include medical robotics, implantable, sensors and handheld devices just to name a few. Silicone wire is also manufactured for medical tubing and is typically used in applications such as catheters, drains, feeding tubes, and peristaltic pumps. Manufacturers considering silicone for these types of applications can choose from special grades that meet stringent health agency requirements.

Automation and Ribbon Cables

Typical ribbon cables are not designed for repetitive flexing. These cables are generally made of PVC which is brittle and not resistant to harsh chemicals. For applications in the automation and robotics industries a cable designed specifically for hi flex applications is needed. Silicone ribbon cables can withstand millions of flex cycles and can be extruded or bonded from as little as two conductors to over twenty and can be manufactured up to 40AWG. Applications such as multi-axis motion systems, robotic equipment, linear motor stages and packaging equipment all require flexible flat cable designed to achieve reliable performance. Silicone ribbon cables are also used in static installations where a flexible cable is required.

Automotive

temperatures, tight spaces, and contact with fluid and chemicals. This type of environment is perfect for silicone wire and cables. Silicone insulated wire is normally used in the automotive industry for ignition, battery and spark plug wire. Custom silicone cables can be manufactured to improve the engine's performance. High performance options for ignition wires can include EMI suppression, Kevlar strength members, fiberglass braid, nickel alloy conductors.

There are many applications suited for silicone wire and cable. This article only named a few. If you would like to discuss your application or have questions, please contact Calmont. Feel free to leave a comment or share this article. To find out more about silicone insulation visit our silicone page or our Insulation and jacket materials page.

Custom wire and cable: Reducing your cost.

With custom cable it is not uncommon to hear “Copper prices just dropped, why didn’t my cable price go down?” Copper prices are a major factor affecting custom wire and cable prices but not the sole factor. Custom cable is normally made to order and many times in smaller quantities which is affected by the prices of materials at the time of ordering. “Off the shelf” commodity wire is usually made continuously and in large volumes which absorb day to day cost fluctuations of copper/metals, compounds and labor/set up keeping the price more stable.

Here are just a few factors which affect the prices of custom wire and cable products

Petroleum prices- Which can range from transport and freight costs to the actual compounds which are made from petroleum products.beside copper:

• Material shortages- An example is the fluoropolymer (FEP), earlier this year due to the earthquake in Japan affected production for Daikin and DuPont which are the only manufacturers of fluoropolymers in the world today. In addition with China cutting back on their fluorospar exports which happened at the same time resulted in an increase of 20-30% for the compounds.


• Material minimums- Custom cable designs sometimes use conductors and compounds which are not commonly used and are subject to minimum buys which are factored into the per foot price of the cable.
• Set up- Setting up equipment takes time and material, the higher the volume the less the set up costs affect final price.

There are ways to help keep your cost down, for example:

• Plan ahead – Placing blanket orders, scheduling orders over multiple shipments over time. Buying higher volumes helps absorb minimums by amortizing material, set up and labor costs. Sometimes the overall cost for ordering 1000 feet is less than ordering 200- 500 feet. Ask for price breaks to evaluate your options.

• Request samples – Custom wire is usually specialized to the design however you can check to see if your manufacture has a similar item they can sample you. This is helpful when you need prototype of proof of concept quantities. Many custom cable manufacturers have sample stock and overruns available which may be similar to what you need.

• Wait for it- If you time to wait, ask your cable manufacture if they have any upcoming jobs using the same material. Running your order along with another may save you on set up costs and/or minimums. It's a long shot, but can be done if your material is a more common one.

• Substitutions- Ask what is driving the price. If a material minimum is involved, find out if there is a substitute material which may be readily available you can use. Sometimes just changing the plating or strand count can make the difference.