Medical Cables: What’s the difference?

Medical cables do differ from cables used in other industries. It isn't recommended to use standard/ generic wire and cable in your medical device design unless the wire or cable doesn't need to meet any medical requirements or is used internally in your device. Every industry has it's unique requirements when it comes to wire and cable. The medical industry is no exception. Medical wire and cable is readily available "off the shelf" however, many medical industry engineers turn to custom medical cables due to their application's unique requirements. What makes medical wire and cable different? Medical devices are designed to be precise whether it is for diagnostics, patient monitoring, surgical or provides imaging/video. Medical device cables may need to provide multiple functions with just one cable such as, data, power fluids or air. Medical cables can be complex or a simple design, in either case custom medical device cables offer the performance and longevity needed for this type of application.

Another unique feature of medical device cables is the insulation and jacket compounds are formulated to meet the specific requirements of medical applications such as:

• Sterilization - Sterilization techniques include autoclave, E-beam, chemicals to name a few. What insulation and jacket materials can withstand do vary and it is important to take this into consideration when designing your medical device. Sterilization properties chart is a helpful tool, but discussing your requirements with a custom medical cable manufacturer can save you research time.
• Bio-compatibility - Patient contact is another requirement for medical device cable. Contact can be from exterior to implantable. Medical wire and cable jacket compounds are available in many grades and the extent of patient contact should be discussed with your medical cable manufacturer.

Disposable or reusable?

Disposable cables are normally used for a limited usage and do not undergo repeated sterilization before being disposed. Disposable wire and cable are made of less expensive materials such as PVC. Reusable medical cables normally have to withstand anywhere from hundreds to over a thousand sterilization cycles.

Medical device wire

Medical device lead wires can also differ from generic wire. Sensors and monitoring devices are becoming smaller, wireless and their functions are more complex. Patient monitoring devices often require lightweight, small gauge, ultra flexible wire for patient comfort while being monitored. Patient monitoring devices are sometimes worn for long periods or even implanted. The need for small extremely flexible wire is becoming more evident with these types of medical applications.

A few examples of long term patient monitoring include:

• Fetal monitoring devices - Fetal monitors can be wired to a receiver or wireless for extended monitoring. The monitor is connected to a unit which sends information to a receiver allowing the patient to move freely. Small gauge very flexible wire and cable is used for this type of product.

• Sleep monitors - Patient comfort is important with this type of device. The ultra flexible wire need to be lightweight and a small gauge using flexible insulating materials such as TPE or silicone.

• Heart monitors - This type of long term device normally uses cables instead of lead wires. Heart monitor devices can be connected to an implant then to a battery/power pack or sending unit which sends information to a receiver/recorder. Cables may be required to send data, supply power, be flexible and be resistant to abrasion and cleaning solutions. Other types of heart monitors may be connected to sensors externally on the body for extended periods.

When considering your medical device wire and cable for your product be sure to speak with a custom medical cable manufacturer to find out what materials and construction will work best for your device.

High Voltage Wire- Robotics Wire Solutions

When you are in the market for robotics wire, it will be easy for you to find everything that you need if you know where to look. High voltage wire is a specialty item, but it is available online and you have many more options than you might have before. Getting your hands on the latest technology in wiring for robotics and other high-tech applications isn’t difficult as long as you take the time to look. Use the internet to your advantage to learn everything that you need to know and then some.

Robotics wire is used in many robotics and technology applications. There are a variety of different uses and industries that rely on this type of solution, allowing everyone to take advantage of technology in different ways. The most common industries include: healthcare robotics, military robotics, consumer robotics, and industrial robotics. Of course, whenever you need this type of high voltage wire, the application doesn’t matter so long as you find the right solutions and brands for your needs.

This isn’t something that you can just buy at the local hardware store. You really have to take the time to find specialty robotics wire solutions. These professionals know all about applications for this wire, how to buy it, and which styles and types are most in-demand. There are a lot of considerations that you have to think about when buying high voltage wire, including things like:

-Durability

-Flexibility

-Lifespan

-Strength

With the best wires, you will be able to trust that you are getting what you deserve. The wires should be made from specially compounds and materials that are placed over high-strength stranded alloy wires. It doesn’t matter what you have in mind because you can find twisted pairs, coaxial cables, hookup wire, silicone wire, and other solutions online.

Engineers and anyone working with welding or painting robots, rotary tables, conveyors, animatronics, or pick-and-place devices will be able to see the value of this type of wire. Robotics wire comes in all shapes, sizes, and lengths to give you everything that you deserve out of your investment, no matter what you have in mind. Make sure that you take the time to figure out exactly what you want and need because the internet makes it easy for you to get the best high voltage wire for every application, no matter what you have in mind.

Robotic Wire and Cable Selection Tips

It would be nice to go online and simply purchase robotic wire or cable for your robotic application. The truth is, selecting the right wire for robotics isn't that easy. Robotic movements vary and have different levels of demand on the robotic wire. Movement includes repetitive flexing, torsion/twisting and bending at multiple points. Off the shelf wire and cable normally isn't manufactured to endure these types of robotic movement. Robotic wire and has to be manufactured based on the type of movement and use. Construction and material selection are key factors in preventing robot failure. Robotic cable designs begin with material selection. Tell your custom cable manufacturer all about your robotic application and include:

• The type of movement is required of the wire or cable, number of cycles.
• The environment which it will be operating in. Include temperature, contact with fluids or moisture and abrasion resistance.
• Other requirements such as, voltage, EMI, flammability and any special needs.

The more your custom cable manufacturer knows about your application the better your cable design will be.

Material choices depend on the robotic requirements and begin with the conductors. Conductors (except solid core) are made up of multiple strands of fine wire, the more strands in the construction the more flexible and resistant to flex damage the conductor will be. The use of high strand count alloy conductors is recommended for high flex cycles and torsion. Alloy materials are stronger than standard copper conductors and can withstand repetitive flexing and vibration. High strand count conductors are available in several types of configurations), your cable manufacturer can recommend the right one for you.

Insulation and jacket materials also play an important role in the Robotic wire or cable's performance. Selection will depend on the surrounding environment. Silicone insulation and jackets are ideal for chemical resistance, high temperatures and super flexible cable designs. Silicone is not as resistant to abrasion as other materials. Understanding the material properties will help narrow down the choices.

High Voltage Wire and Cable: What you need to know before you buy

High Voltage (HV) wire (also referred as leadwire) and cable are used in a variety of applications such as, ignition systems, instruments, AC and DC power transmission in just about every industry.

The wire and cable construction and material are determined by three main factors:

• Voltage- To determine the thickness of the insulation

• Current capacity- To determine the cross-section size of the conductor(s)

• Environment- Temperature, chemical, UV exposure and mechanical impact to determine the cable construction and material of the outer jacket.

High voltage wire has two factors which require special attention. The first is the type of insulation needed to prevent arcs to nearby components, wiring or people. The other is the insulation diameter necessary to reduce corona loss. Reduction of corona is important because a common high voltage problem for insulation is damage to the insulation caused by corona discharge resulting in pinholes. With all high voltage applications, it is important that the insulation of the cable not deteriorate due to the high voltage stress.

Popular insulation materials for hookup type wire are polyethylene, PTFE, FEP, PFA, and silicone. Insulation such as PTFE is less bulky than silicone and is preferred where smaller sizes are required. If a flexible wire is required, PTFE is not a good choice. Silicone insulation is a common choice for high voltage applications especially when co-extruded. Silicone insulated wire is an extremely flexible wire, even at extreme temperatures, excellent electrical properties and is resistant to most chemicals and moisture to name a few.



Why co-extrusion?

Corona resistant wire (HVCR) is typically constructed with a conductor surrounded by a semiconducting sheath, which is then surrounded by the insulation. The semiconducting sheath effectively increases the diameter of the wire, reducing the tendency for corona discharge. Co-extruded wire and cable are common for many high voltage applications for it's ability to effectively reduce corona. Co-extruded wire is the same construction with the semi-conductive layer and outer jacket are extruded simultaneously. The co-extrusion process prevents air and gaps between the conductor and insulating layers thus reducing if not eliminating corona.

Custom wire and cable manufacturers can assist you with material choices and cable construction based on your high voltage requirements. Having the right cable from the start will save time and money down the line.

Flexible cables or high flex?

Robotic and automation applications require specialized cables that can handle repetitive flexing and movement. Design engineers must consider using custom cables designed to withstand flexing to prevent product failure and down time down the road. Robotic wire applications don't always require extremely flexible wire and cable, withstanding hi-flex environment is usually the main concern.

Flexible cables or high flex? These two terms are often misunderstood. Flexible can mean the limpness of a wire or cable and is used by some to describe high flex. The term high flex wire and cable is usually used to describe repetitive flexing. Can you have both? Yes you may. Ultra flexible wire designs use high strand count conductors for higher flexibility as does high flex wire. High flex wire normally will use alloys for the conductor material while maintaining the high strand count. High strand count conductors are made up of many fine strands of wire, the higher the number of strands the more flexible and resistant to breaking the wire will be. Depending on the wire gauge, strand counts can be in the thousands. Typical off the shelf wire is available in solid, 7 or 19 strands. These stranding configurations are better suited for static type of applications. When a wire has fewer strands, the strands will fatigue and begin to break under repetitive bending, vibration and flexing situations. As the strands break, conductivity will be compromised and may result in damage to the wire insulation. Conductor stranding is available in a variety of configurations.

For best results for high flex robotic cables need to be designed with high strand count conductors preferably using an alloy for added strength. Insulation can vary depending on the application. When designing the insulation and jacket, the environment must be considered. A few considerations are:

• Chemical resistance
• UV resistance
• Abrasion resistance

For super flexible cables, silicone insulation and/or jacket is a great choice. Silicone is resistant to chemicals and one of the most flexible of material choices. The downside to silicone is abrasion resistance. Other flexible wire insulation and jacket materials choices include TPE, polyurethane and Calmont's Superflex which is a special flexible PVC to name a few. Cable construction and shielding options also play a role in flexible wire and cable. Consulting a custom cable manufacturer and discussing the application, environment and use of the robotic cables prior to product design is recommended. Making the right cable design choices from the start will prevent down time and product failure in the future.

Medical cables and UL certification.

There are times where medical cable designs requiring super flexible wire and the available UL styles don't match the design requirements. This happens often. UL sets the standards for different categories of wire and cable. The standards include wall thickness, material, voltage rating, flammability, type of conductor and other factors. What these standards do not take into account are the requirements for individual medical devices for ultra flexible wire or cable, high flex wire applications and sterilization techniques. Custom wire and cable manufacturers can manufacture the same construction to meet the UL specification while making improvements on performance for example using higher strand conductors, alloys for added flexibility and strength or insulation and jacket material improvements.

Recently, we received design request for a flexible flat medical wire for a two conductor cable with multiple lumen, the customer required a UL style for the wires but not the lumen. We often receive requests for medical cable designs requiring UL certified conductors but not all the components in the cable.

The reality is that UL certification for individual components becomes null and void when used in medical devices. If the device needs to be UL certified then the entire device needs certification not just the components individually. Custom cables can be manufactured to perform better than a UL cable. Some examples of improvements are:

• More flexible construction and materials
• Withstand sterilization and chemicals
• Hi-Flex and vibration resistant
• Conductor sizes outside the UL style

There are many UL styles for wire available and finding a close match to your needs is possible however, finding a close match is not the same as having a cable to meet or exceed your requirements. Wire can be designed to meet voltage, flame and other requirements and doesn't have to be UL certified to do so. When designing your wire and cable it is important to look at your individual product requirements and design the wire to meet those needs.

If your medical device is required to be UL certified, then design the wire and cable to meet your product's needs instead of designing your device around available UL styles. In the end the entire device will need to be certified.

Flexible Flat Cables: Having it your way

Need a super flexible flat cable? Need a 36AWG ribbon cable with 21 conductors all in pink? No problem.

Off the shelf flat cables are often available in limited sizes and flexibility which creates problems for designers who need more robust or flexible flat cables. Off the shelf flat cables are normally made of PVC and the conductor stranding is 7 or 19 strand. For applications requiring high flex cables, resistance to chemicals or flexibility off the shelf cables may fail to meet your expectations. Off the shelf cables do not give options for:

• Flexibility and hi-flex applications
• Odd number of conductors
• Uncommon sizes
• Unusual configurations
• Custom colors
  
  

Flexible flat cables are ideal for hand held devices, automation and robotic applications. Engineers and product designers do have options by working with custom wire and cable manufactures to design exactly what they need. Custom wire and cable manufacturers can offer a variety of sizes, configurations and flexible flat cable options. There are two basic types of flat cables:

Ribbon cables - Ribbon cables are multiple conductors connected in a parallel configuration where the conductor spacing is controlled. Silicone ribbon cables are a popular choice for applications where an ultra flexible ribbon cable is needed. Using silicone along with high strand count conductors and/or alloys for added strength and resistance to fatigue for hi flex applications will add to a ribbon cable's flexibility other flexible material are TPE, Polyurethane, and even PVC (Calmont's Superflex PVC).

Top 3 Choices for Ultra Flexible Wire or Cable

Flexible wire in terms of how limp it is starts with the wire design options. The choices you make can greatly impact how flexible the wire or cable will be. The right choices can make the difference between flexible wire and a super flexible wire. Designing a flexible wire or flexible cable begins with the design. We start at the core, conductor stranding and construction.

1. Conductor stranding: Conductors are made up of fine strands of wire assembled together into several configurations. The more strands in the construction, the more flexible and resistant to repetitive flexing the conductor will be. Conductor stranding options range from a solid strand (one strand) to over a thousand strands depending on the wire gauge. The construction of conductor stranding is important as well. Stranded conductors can be manufactured in a variety of configurations, the most common being concentric (true concentric, equilay concentric, unidirectional concentric, and unilay concentric), bunched and rope.

Conductor stranding with rope construction makes for a more flexible wire. This construction 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. To achieve the most flexible wire design, be sure to use the higher stranded conductors. For flexible wire with repetitive flexing applications, consider using an alloy for fatigue resistance.

2. Insulation: Flexible wire and cable requires a flexible insulation material. There are many choices for insulating materials. The most flexible wire insulation is silicone, together with the right conductor stranding can be as limp as a wet noodle. While silicone is the most flexible wire insulator, it does have poor abrasion resistance. Choosing the right material will depend on your application and use, consult your wire and cable manufacturer to determine which material will work best for your application. Flexible insulation and jacket materials include TPE/TPR, polyurethane and even PVC, Calmont's Superflex® uses a special PVC formula for increased flexibility. When choosing an insulation or jacket material, consider your requirements. Is your application requiring sterilization? Is abrasion resistance required? Temperature, chemical contact and bio-compatibility are other requirements to consider. Calmont's insulation and jacket material chart is a helpful tool.

3. Cable construction: Cable construction is another component for super flexible cables. Cable lay length and shielding can increase the cable's flexibility. The cable lay is how the conductors are cabled together, the wires can run parallel or be twisted around each other. The length between each twist can be adjusted for maximum cable flexibility. Shield options include spiral, braid and Mylar or foil wrap. The application is important when considering shield types. For flexible cables which undergo repetitive flexing, spiral and foil type shield are not good options as the shield coverage will be compromised over time.

If you want a more flexible cable design, contact Calmont Wire & Cable to learn more about material choices.