With increasing dependence on electronic equipment, there is a huge need for cable assemblies that are reliable in performance, and durable in service. One industry that depends immensely on cable assemblies is the medical sector. Diagnostic equipment like ECG and EKG, imaging systems like X-ray, CT, MRI, PET, as well as automated laboratory machines and systems depend on medical cable assemblies for support.

Points for Custom Cable Assembly Design

Every cable assembly is different, and is designed to meet particular needs of an application. Hence, there are a variety of companies that design and produce assemblies for application areas such as hospitals, nursing homes, health clinics, research laboratories, etc.

Custom cable manufacturers work with a customer to design the perfect assembly for his needs. Customers need to provide specific information that will ensure that the cable assembly will be built according to their requirements.

Here are a few points to remember when designing a custom medical cable assembly:

• Sterility Requirements: Every equipment used in a medical application needs to meet certain standards of hygiene prescribed by the FDA. The cable assembly will have to be designed depending on the number of times that the equipment is washed down or sterilized.
• Choice of Disposable or Reusable Cables: The design of the cables will also differ if they are disposable or reusable in nature. Disposable cables can be constructed from materials like PVC, which is less expensive. Reusable cables need to be sterilized prior to usage. Therefore, the insulation needs to be constructed from a material like polyurethane, which can withstand repeated sterilization procedures.
• Beneficial Operation Characteristics: As each application area and environment is different, the insulation and outer protective jacket will have to be designed to protect the cable from environmental hazards such as moisture, chemicals, abrasions, extreme temperatures, etc. Depending on the application space, the assembly will have to be flexible for installation and repair.

For a manufacturer, understanding a medical application is the first step in helping the customer choose the right materials for cable assembly construction. With the information provided by the client, industrial designers can produce the ideal medical cable assembly for medical applications.

Military Specification (MIL-SPEC) cable assemblies are designed to provide benefits of reliable performance and durability in demanding applications. The success of military equipment depends a great deal on the high signal integrity provided by the assemblies.

Supporting Military Applications :

MIL-SPEC cable assemblies can support personnel and equipment in various military applications. Here are a few examples:

• Soldier Worn Systems: Many devices are worn by soldiers on the field. Cable assemblies can be designed with elastic materials, which allow the cables to be stretched when worn outside military gear. They can also be integrated into the protective armor and clothing. Various RFI shielding options can protect the devices, while maintaining high signal strength in applications with contaminants such as sand, water, and dirt.
• Aviation: For military and aviation applications, cable assemblies are designed with high temperature wires and custom connectors. They can be constructed out of lightweight materials such as carbon fiber, rather than heavy metallic components. The connectors can comprise a simple click design for installation and removal.
• Defense Vehicles: Vehicles like cars and trucks endure immense stress on the field. For such applications, connectors can be optimized to be lightweight and small in size. The result of this would be an increase in application space, without adding to the weight of the vehicle. Waterproof cables can be used to ensure that the vehicles do not shut down when travelling in rain, or passing through water-filled areas.
• Communication: Military communication requires the most amount of protection, as they are used in a wide number of settings. For this application sector, cable assembly manufacturers offer material choices such as beryllium copper, tinned copper, carbon fiber, PVC, HDPE and Teflon. Custom connectors can be designed using overmolding process for improved protection. A few common applications include radios, Push-To-Talk (PTT) systems, and interconnecting headsets.

MIL-SPEC cable assemblies can prove to be extremely useful in a variety of military applications. The right choice of material and design, can lead to the manufacturing of reliable and durable products.

At Carr Mfg. Co., we get a number of first time clients who are interested in getting wire and cable harness assemblies designed for an application. We also get a number of enquiries from customers who are interested in our products, but do not have a lot of information on their design, operation, and benefits.To solve the queries of such customers, we are providing basic information about wire and cable harness assemblies in this post.

Wire Harness and Cable Assembly FAQs :

To ensure that the information is simple and easy to understand, we are providing the information in a question and answer format.

1. How many Wires comprise an Assembly? How are the Specifications Decided?
   • There is no general number of wires in an assembly. The wires are selected depending on the application and the various systems that the harness will be connected to. A simple system may require a cable assembly with five to seven wires. Larger assemblies may consist of more wires. The cables are selected based on the kind of data that they will be transmitting. The length, insulation material, wire size, and power capacity, are all decided based on the application.
2. What are the Benefits of Cable Assemblies?
   The following points showcase the benefits of cable assemblies.
   • Security and Safety: The harness is constructed out of an insulated material. It ensures that the bundle will not flex, reducing the chances of abrasions and short circuiting.
   • Simple Installation: Wire harnesses eliminate the need to connect individual wires to their respective systems. Many application systems have existing cable assemblies. Hence, the newly installed wire harness simply needs to be linked with the existing one. Thus, no time is wasted in the wire installation process.
   • Reduced Wire Derangement: As the wires are bundles, the assembly reduces chances of wire cluttering. Also, the harness requires less space in terms of installation.
3. What is the General Lead Time for Cable Assembly Delivery?
   • Every cable manufacturer will offer a different delivery lead time. The delivery depends on a variety of factors, include material availability, production requirements, and inspection time. At Carr Mfg., we can typically deliver your products within two to four weeks.
4. What kind of Testing Procedures are Performed for Standard and Custom Assemblies?
   • Testing is performed during and after the manufacturing process. As the wire assemblies are being produced, the products and components are continually checked for aspects such as weld peel, overmolding, pull and wire retention forces.
   • Other testing procedures performed during and post manufacturing include:
     • Leak testing
     • Hi-pot testing
     • Impact testing
     • Connector separation force testing
     • Mate and unmate cycle testing
5. What types of Cable Assembly Designs are Generally Offered by Manufacturers?
   • Cable assemblies can be designed in a variety of ways. Some of the common designs include:
   • Point-to-point Assemblies: This consists of terminal strips, which are used to create interconnections between two individual points.
   • Multi-Termination Type Assemblies: These consist of multiple fiber cables, which are pre-terminated. This means that connectors are added to each fiber cable before the assembly is created.
   • Ribbon Assemblies: Ribbon assemblies are named after the insulated wires, which are connected together to form a flat ribbon. Ribbon assemblies can be subcategorized into high-speed, shielded and jacketed non-PVC, split or multi-branch cable assemblies.
   • Radiation Tolerant Designs: These cable assemblies are designed to maintain their performance in applications with high amounts of radiation. Generally, radiation tolerant assemblies have a tolerance range from 5 to 200 Mrad.
   • Crush Resistant Designs: These assemblies can withstand immense amounts of pressure. You can find assemblies with the ability to withstand over 250 lbs. per inch.

These are some of the basic questions that first time customers need to know when procuring cable assemblies. Ensure that you have every query answered before you order a product. Clear knowledge of the products, its features and benefits, can help you make a wise decision.

In the previous post, we had discussed the initial steps to building a harness. We began by creating a wiring diagram, collecting the tools, stripping the wires, and cutting and attaching the heat shrink. We also showcased the steps for connecting and crimping the terminal and wire, and shrinking the heat shrink. In this post, we will take a look at the remaining steps involved in building a wire harness.

Steps to Build a Wire Harness :

The following points showcase the basic requirements and steps to be taken to build a wire harness.

• Interlacing Multiple Wires: The method shown here is just one way to splice multiple wires. Cut the insulation off the ends of the wires, and insert them into a crimp tubing. Ensure that the wires go all the way through the tubing. Pass the wires through the heat shrink tubing as well. Using a crimping tool, apply force to the crimp tubing. Then use the heat gun to shrink the heat shrink tubing.
• Examine the Connectors: As most wire harnesses are built for demanding applications in extreme environments, it is suitable to use weather pack connectors. These are similar to factory connectors, but slightly different. These connectors consist of a male and female housing, and each housing comprises seals and terminals.
• Sealing & Crimping the Wire: First strip about 3/8ʺ of insulation from the wire. Then slide a seal onto the wire. Using a crimping tool, crimp the wire terminal. Ensure that crimping is done only to the crimp area, and not to any other part of the terminal.
• Attach the Terminal: Insert the wire with the seal into the terminal while it is still in the crimper. Squeeze down and make the crimp. You can also attach small metal strips to hold the rubber seal in place.
• Attach the Wire to the Male Housing: Now the wire is ready for assembly. Insert the terminal into the male housing. Keep pushing the terminal inside till you hear a click. Once this is completed, close the housing flap. The flap will go around the wire.
• Connect the Wire to the Female Housing and Attach the Connectors: Perform the same procedure with the female housing. You can use a zip tie to hold all the wires together. Place a large green seal on the outside of the female housing. Then slide the male housing over the female housing, and connect them together.

These are the basic steps to build a wire harness. After this, the harness can be installed into the application equipment. A bit of practice and patience can help you to create a harness of immense quality.

Building a wire harness can be a time consuming and difficult task. There are two basic reasons why a person will choose to create a wire harness – either to improve its overall appearance, or customize it for an application. Every wire harness is different, however, the basics of wire harness construction is pretty much the same. If you take your time, you will find the process to be less demanding.

Steps to Build a Wire Harness :

The following points showcase the basic requirements and steps to build a wire harness.

• Create a Wiring Diagram: Before any of the wire cutting can begin, you need to create a wiring diagram of your system. This can be performed by using a computer program like CAD. Generally, a wiring diagram consists of two parts – a schematic, and a harness. The schematic will showcase the parts, their locations, and how they are connected. The harness diagram will help you create an exact plan of how all the wires and connectors will be put together. You can also color the diagram to represent different parts. For example, colored circles can symbolize connectors. This will help you to keep things organized, and make the process easier.
• Collect Your Tools: The next aspect is to collect all the necessary tools to get the job done. You will require the following:
  • Wires
  • Zip ties
  • Heat gun
  • Terminals
  • Connectors
  • Multimeter
  • Wire cutter
  • Crimping plier
  • Heat shrink tubing
  • Wire stripper (manual or automatic)

  The size of the heat shrink tubing used will vary depending on the sizes of the terminals. As wire harnesses are generally used for demanding applications, GXL wire with PVC insulation would be a good choice. This is a high temperature wire, and is ideal for harsh environments. The wire provides resistance to heat, fire, moisture, and chemicals.

• Strip the Wire: Use the wire stripper to remove a small part of the insulation from one end of the wire. The wires will be attached to terminals, so you need to make sure that the length of the cut is according to the terminal size.
• Cut the Heat Shrink: Cut the heat shrink tubing of a length a little longer than that of the stripped wire. Insert the heat shrink over an unstripped area of the wire.
• Attach a Terminal: Take a terminal, place its seam into the crimp pliers, and crimp the terminal slightly. Insert the terminal into the wire, then use the pliers to squeeze the wire and terminal together. Use enough force such that the two parts will be crimped, but not so much that the wire gets damaged.
• Cover the Wire: Once the above step has been completed, pull the heat shrink over the crimped wire edge and terminal seam. Ensure that the tubing closes tightly over the two parts.
• Shrink the Tubing: This is where the heat gun needs to be used. Turn on the gun, set it to the required temperature, and allow it to warm up. Direct the gun’s hot air over the heat shrink tubing. The tubing will reduce to the appropriate size, thus protecting the parts.

These are the initial seven steps in the wire harness manufacturing process. The post will discuss the forthcoming points, including joining connectors and installation.

The process of assembling box build assemblies is quite simple. It involves a Bill of Materials (BOM), the customer providing Gerber files, CAD design, assembly, and delivery. Many customers assume that once the Gerber files are handed over, the Electronic Manufacturing Services (EMS) provider will take care of the rest. There are certain points that need to be discussed before any of the above mentioned steps can take place.

Points to Discuss with your EMS Provider

If you are getting an electronic manufacturing services (EMS) provider to design and produce your box build assemblies, then there are certain points you need to consider.

• Unambiguous Bill of Materials: The first point of discussion between the client and the EMS provider is the BOM. It is imperative that the BOM be clear in terms of the materials and components, which will be used to create the box build assembly. The BOM also needs to specify the materials that the provider will source, and those that the client will provide.
• Define the Components: As each component will make a difference to the assembly and operation of the product, it is important that you specify certain components. Although the provider can source the large components, you can specify on smaller yet important materials. Examples of these would be adhesives, fasteners, heat shrink tubing, wires, etc. Defining such components can help you to maintain your costs, and ensure delivery of the product on the expected date.
• Specify Characteristics: Aspects like finishes, weight, size, and tolerances are usually left to the freedom of the provider. However, if not properly specified these can lead to issues at the time of assembly and quality testing. Ensure that such aspects are also specified. Size and weight are also important points to consider for storage and handling purposes.
• Provide CAD Layouts: This is an option for customers. There are many reasons why providing a CAD model will help move increase the entire process speed:
• The designers do not need to visualize the product and its assembly.
• It can include a drawing where all the components will be placed.
• A customer’s personal design followed to the letter can ensure that the box build assembly is manufactured to industry compliances.
• Many CAD software offer free drawing options.
• Decide on the Build Method: You need to decide on the most optimum build method for the electrical systems. Consider methods like prepared cables, or point to point wiring, and create a schematic for the same. If possible, provide this in an electronic format as well.
• Enquire about the Testing Methods: If possible, ask the EMS provider if he can perform specific tests to ensure that quality and efficiency of the product. You can specify functionality testing, electrical safety testing, etc. Also, you can find out from your service provider the best choice of tests for the assembly.
• Request for Delivery Method: Depending on the type of box build assembly, you can specify the type of packaging and the mode of transport for delivery. You can ask for shrink wraps, or special boxes, or even pallets.

Outsourcing box build assemblies is a process that requires the customer and the EMS provider to work in unison. Providing the right information before any process is begun can help in the design, production, testing, and delivery of an assembly of world class quality.