Category Archive: Cable Assembly
In this post, we shall discuss the actual wire crimping process. Crimping can be done right with the proper materials and tools, and a clear step-by-step procedure. We will provide information to all these factors in this post.
Tools and Materials
Before starting any crimping work, ensure that you have all the tools and materials needed to perform this task correctly. You will need:
- Crimp tool
- Wire strippers
- Crimp terminals
- Heatshrink system
- A stranded wire with required specifications
Steps to Achieve Wire Crimping
The following showcase the entire procedure from start to completion.
- Choose the Wire: The type of wire you need will depend on the application. Hence, understanding the equipment’s requirement can help you to find the right type. First, look at the wire size; this is generally given as AWG (American Wire Gauge). An example of this would be 16 AWG. If you do not have access to this information, there is another way to determine the wire size. Strip a small length of the wire insulation. Count the individual wire strands, and measure the diameter of one strand. You can then multiply the number of strands by the diameter of one strand.
- Select the Crimp Terminal: There are a variety of crimp terminals to choose from. The quality of the crimp joint will depend a great deal on the terminal chosen. The following points need to be considered when choosing a terminal.
- Plating – Terminals with plating ensure that there will be low contact resistance, and protection against corrosion.
- Pre-insulation – These terminals consist of a metal sleeve, which is used to grip the wire.
- Turned Pin – These are constructed from rod materials, and are almost round in shape. They support the creation of connectors.
- Decide on the Crimping Tool: Crimping tools come in a variety of designs. However, it is important that you select the tool that the crimp terminal is designed to be crimped with. Consult the crimp terminal manufacturers website for tooling information. If that is not an option, be sure to get a tool that will accept the crimp terminal and has a ratchet design. This will ensure that the crimp has been formed correctly.
- Make the Crimp: The crimping process consists of a few additional steps.
- Determine the length of the wire, and strip the end. The stripping length should be such that when you insert the wire into the crimp, there should be at least 1 or 2 mm protruding from it. Cut the insulation off the end, and expose the wire strands.
- Insert the wire into the crimp. Ensure that all the strands have been inserted into the crimp.
- Place the crimp and wire into the crimping tool, and ensure that it is perfectly seated inside. Cycle the tool until it releases.
- Remove the crimp, and inspect the wire. Ensure that it is in the correct position, and that the insulation is secure. Give the crimp and wire a tug to check that they are secured.
- When Using Heatshrink: Fit the sleeve over the crimp and wire. Ensure that the sleeve is at the right position, and is not covering the crimp’s terminal end. Use a hot air gun to shrink the tubing.
Points of Warning
- Never choose a solid wire. Only choose wires with individual strands.
- Avoid any crimping tool that does not have a ratchet feature.
- It would be a good idea to perform test crimps on other wires before performing the crimping process.
A complete set of tools and materials, and step-by-step completion will produce an efficient, reliable, and long-lasting joint for your application equipment.
The manufacturing of cable assemblies and wire harnesses involves a variety of processes to ensure the final product’s strength, function, and performance. One of the critical processes is cable assembly testing. The goal of this testing process is to ensure that the product will meet or even exceed the application and industrial specifications. But what are the testing procedures performed on industrial wire and cable assemblies. We answer this question with this post.
4 Cable Assembly Testing Procedures
The testing procedures described below are performed by all cable manufacturers to ensure their products are fit for application use. The tests need to be performed while referring to IPC or WHMA guidelines.
- Electrical Testing: The entire cable assembly needs to be thoroughly checked for opens, shorts, and incorrect wiring. The method to perform this test is attach the assembly’s end connectors to mating connectors, which in turn is connected to a fixture. The fixture is the device that checks the assembly for open wiring, and short circuits between shields and conductors. It can also check if the pins of the assembly’s components are in the proper place.
- Visual Testing: As the name suggests, the cable is visually inspected for any defects and deformations. Components that are tested are sockets, connectors, markings, finishes, as well as basic design and construction. Dimension inspection is also performed to ensure the cable is up to specifications.
- Environmental Testing: These tests are designed to check whether the cable can continue performing despite exposure to various environmental elements. The cable is subjected to the following types of elements:
- Thermal shocks
- High humidity levels
- Salt sprays for corrosion
- Elevated and decreased temperatures
- Mechanical Testing: This stage of testing focuses on the connectors, and the overall durability of the product. The connectors are disconnected, and then reconnected to determine how much force is required to connect or disconnect the assembly. Product durability is tested by subjecting it to a set number of flexing cycles. This helps the tester determine the approximate service life of the assembly.
It is important to come up with a testing plan, which comprises the necessary tests to ensure the performance of the product. Thorough cable assembly testing will ensure that cable will perform as required in extreme environments, and have a long service life.
When selecting an electrical cable for the project, various important factors need to be considered such as the type of application, load bearing capacity, etc. Beyond these primary considerations, the wiring expert should understand the difference between a stranded and solid cable, and their contribution to the project.
A solid cable features a single thick conductor made of solid metal, which tends to be more rigid. The conductor is usually made of copper. A stranded cable is composed of several small conductor strands (typically 7) that are twisted or grouped together to form a large wire.
Stranded vs. Solid Cable
Below are three arguments for stranded vs. solid cable.
- Flexibility: Cable flexibility is an important factor when considering cables for an assembly project. A solid cable with a single metal wire is not bendable, so is perfect for applications that don’t require bending. Stranded cables consist of a large number of small individual strand conductors grouped together. Hence, stranded cables can withstand over-bending and over-flexing.
- Applications: Solid cables are used for structured wirings as well as semi-permanent and permanent installations. Other applications of solid cables include long distance cable horizontal and backbone cable runs, wall jacks, HD applications, and power over Ethernet (PoE) applications.
Generally, stranded cables are used in patch panels for workstations. Since they are flexible, they can be used for applications, where over-flexing is common.
- Attenuation: Stranded cables are recommended for short distances because they possess higher attenuation than solid cables. Attenuation is a term for a reduction in signal strength – analog and digital. Sometimes, attenuation is a consequence of long distance transmission.
Stranded cables are usually recommended for applications 20 feet underground.
Whether you select a stranded cable or a solid cable, proper installation is key to its performance.
An overmolded cable assembly combines the connector and cable in a single design. A molten material is introduced into a mold cavity, which assumes its form on cooling. The color of the molten material can be matched to the color of equipment or cable jack being used. The types of material used for overmolding are rubber, ABS plastic, PVC, PP, PE and macro melt.
4 Important Features of an Overmolded Cable Assembly
Below are four key attributes of an overmolded cable assembly.
- Improved Protection from Abrasion and Weather Elements: During overmolding, all sensitive electrical components are encapsulated, which makes them resistant to abrasion and harsh weather elements. Thus, overmolded cables are considered cost-effective alternatives to conventional cables with black shell and EMI foil. In various industrial verticals, overmolded cables are often subjected to rough use. So a basic idea of the application environment and appropriate material to be used will help an overmolding assembly manufacturer to manufacture the right product. For example, Polyurethane is used for overmolding cable assemblies used in the military and healthcare sector. Polyurethane is abrasion resistant, has a high load capacity, and can withstand high temperature.
- Customization: An overmolded cable assembly is customizable. There permutations and combinations for materials, colors, wire types, and style options are endless. Custom colors, configurations, shapes, and imprints allow OEMs to achieve the highest aesthetic standards. A customized overmolded cable may feature a company name or logo.
- Improved Shelf Life: Overmolded cable assemblies have an improved shelf life than traditional cables because the overmolding offers complete strain relief, high pull strength, and flexible support at the cable exit.
- Compact Integration and Lighter Equipment: When compared to traditional cable assemblies, over molded electronic assemblies are smaller and allow OEM to reduce cost and the size of their equipment. Additionally, overmolding allows inclusion of circuit analysis resistors or reverse polarity protection diodes, PC board assembles, and more.
Most cable assembly manufacturers delivering custom overmolded cable assemblies follow production steps such as potting, premolding, and overmolding to determine the abrasion resistance, waterproofing, and electrical performance of the final product. Customized overmolded cables can reduce the total cost of production and improve performance. No doubt, Overmolded cable assemblies will add value to any electrical application with the above-mentioned attributes.
Industrial cables are designed in different types of sheathing materials to protect wires in applications. Every sheathing is designed to serve a specific purpose. Choosing the wrong cable, or using a cable with insufficient sheathing can be a waste of time, effort, and money. Hence, it is important that you understand the different types of electrical cable sheathing before you choose a wire for your application.
General Cables and Their Insulations
When discussing standard or custom cable manufacturing, there are three types of insulations that are used. These are elaborated in the points in below.
- Non-metallic Cables: Commonly referred to NM, non-metallic cables contain sheathing produced from cardboard or weighted paper, which is encased in plastic. Generally, these cables are used in applications where the chances of damage are extremely minimal, and they are protected from moisture and water. Application examples include outlets, electrical switches, and other types of building wiring.
- BX Cable: BX cable wire is wrapped in a flexible metallic sheath. The metal part of the sheath eliminates the need for a ground wire. The flexible part of the sheath allows the cable to be used in tight spaces. For this reason, BX cable are used in applications like basements – areas that contain great amounts of moisture.
- UF Cables: Underground Feed cables are designed with insulations comprising heavy paper and plastic. While the sheathing design is similar to NM, this insulation is tightly wrapped around the wire. As the name suggests, these cables are used in underground applications like subways, well lamps, and branch circuits.
The type of insulation can make a huge difference to the performance of the cable. By understanding the basic types of sheathing, you will be in a better position to choose the right cable for your application. However, it is always better to consult a cable manufacturer before making a decision.
Cable assemblies are utilized in a variety of industrial applications, which can exhibit electrical noise. Electrical noise can lead to Electromagnetic Interference (EMI) in cable assemblies. When a cable assembly receives or generates electromagnetic interference, it can cause poor signal quality and loss of data. It can also disrupt the function of electronic equipment and other components around it. Hence, it is necessary to use special shielding to protect cable assemblies from EMI.
Shielding for Protecting Cable Assemblies from EMI
Cable shielding is used to resolve the issue of EMI in cable assemblies. A cable shield encapsulates the conductor within the cable to provide effective protection. The shielding impacts EMI in two ways.
- The first way is by reflecting the electromagnetic energy.
- The second way is by picking up noise, and grounding it.
Although some energy will pass through the shielding, but it will be so highly attenuated that it won’t have any impact on the assembly.
Types of Shields Used In Cable Assemblies
Various types of shields are used in cable assemblies based on the application they will be used in. Commonly used shields in cable assemblies are:
- Foil Sheaths: Foil shields comprise a thin layer of aluminum or copper attached to a carrier such as a polyester or Polypropylene film. A foil sheath provides 100% coverage to the cable or components. The foil shield consists of a drain wire for terminating and grounding the EMI.
- Metal Braids: A braid shield is constructed as a woven mesh around the cable core. It is constructed from bare or tinned copper wires. For special applications, stainless steel or silver plated copper braid construction is also used. Metallic braids provide improved termination and lower DC resistance than foil sheaths, which makes them ideal for low frequency interference.
A cable assembly needs to have appropriate shielding according to the application it will be used in. However, it is also important that the equipment connected using the cable assembly should be properly grounded.
If you are designing products for military purposes, then you will need to use MIL-Spec cable assemblies. However, it is not just simply about using these types of cables. You have to use wires and cables with exact specifications according to the product and the application’s requirement. Choose wrong, and the product may not function properly. This is why when creating a military electronic product, you need to pay attention to the military standards.
What are Military Standards?
Military standards, also known as MIL-Spec, are a group of specifications created by US Government organizations. They are the regulations that should be kept in mind when using cable assemblies in harsh military environments. They are particularly important for electronic devices that are exposed to chemicals, abrasive materials, or extreme temperatures. Mil-Spec wire can be used in various applications, including aircrafts, weapon systems, and military ground vehicles.
What do the Standards Comprise?
These standards are used primarily during the manufacturing of military cable assemblies. Cable manufacturers refer to the standards when deciding on various aspects of the wire or cable, such as:
- Type of Application
- Application Environment
- Manufacturing Materials
- Cable Construction
The standards are also referred to when choosing Mil-Spec electronic components. These include:
- Ground wires
- Airframe wires
- Point to point wiring
- Shielding and protective covering
Primary MIL-Spec Standards Organizations
There are a variety of military standards used by cable assembly manufacturers. However, the two most important organizations are the National Electrical Manufacturers Association (NEMA), and the Qualified Products List (QPL).
- NEMA: This organization focuses on developing public policies for cable manufacturers, as well as technical standards.
- QPL: As the name of this organization suggests, the QPL focuses on identifying different types of materials, which can be used in military projects. It also identifies cable product suppliers who can be approved for government projects.
There are a variety of regulations that come into play when creating Mil-Spec cable assemblies. By following the military standards, you will ensure that your products will comply with all the requirements of Department of Defense organizations.
An overmolded cable assembly is a type of cable assembly, which is seamlessly constructed to combine the cable and the connector into a single cable assembly. The process of overmolding a cable involves injecting molding. It utilizes a molten material that is injected into a mold cavity. This molten material conforms to the contour of the mold cavity, and solidifies into a desired shape when cooled.
Custom Solutions for Overmolded Cable Assemblies
The mold cavity can be designed with markings to produce custom molded cables. Custom cable molding options can include a company name, logo, extended area for strain relief, and flanges to be used as attachment points.
Custom cable molding also allows to encapsulate cable connectors in almost any shape. Also, the cable assembly can be produced in various materials, colors, and finishes. Primarily thermoplastic materials are utilized to produce custom cable assembly solutions. These include:
- Polyvinyl chloride (PVC)
Rubber or ABS (Acrylonitrile-Butadiene-Styrene) material is also used for certain unique applications.
How are Overmolded Cable Assemblies Produced?
The production process involves premolding, potting, and overmolding. This is followed by a careful review in order to determine the perfect combination of characteristics and performance to meet the customer’s expectations.
Generally, a two-cavity system is used to produce overmolded cable assemblies. In most cases, each cavity is identical that creates the same shape. Instead, unique forms of cavity can also be used to create different aspects of the assembly during a single cycle. A particular application of this includes an initial pre-shot of non-colored natural materials, which is followed by a colored, finishing material for the outer mold. Moreover, overmolded cables can be designed with straight, right-angle, or any type of connectors for custom applications.
Overmolded Cable Assemblies offer Enhanced Features
Overmolded cable assemblies can enhance your application by offering the following features:
- Flexible support
- Abrasion resistance
- Increased pull strength
- 360 degree strain relief
- Water, moisture, and heat resistance
- Increased EMI (Electro Magnetic Interference)
Speak to a manufacturer to understand how custom overmolded cables can improve your applications.
There are several factors to consider when choosing an electrical wire or cable. However, the most important factors to take into account are the electrical requirements of your application.
Selecting an Appropriate Wire or Cable
Mentioned below are the electrical requirements to consider when selecting an appropriate wire or cable.
- Current Carrying Capacity: This term refers to the calculation of the amount of current a cable can carry. The current carrying capacity of the wire or cable is directly proportional to its size. Current is expressed in amperes (Amp). The larger the wire size, the more current it can carry.
- Inductance: Inductance is the property of a wire or circuit that induces an electromotive force when the value of current changes. It causes the voltage to lag behind. This can occur in the same wire, or in a neighboring wire. It is expressed in microhenries per foot (μH/Ft). Higher inductance can hinder the flow of current in the wire.
- Impedance: Electrical impedance is the total opposition that a circuit or wire presents to the alternating current (AC) when voltage is applied. Impedance is expressed in Ohms (Ω). The length of the cable has no effect of its impedance, but the impedance at the transmitting and receiving end should be same.
- Capacitance: Capacitance is the measure of the amount of charge a cable can store within itself. Capacitance is expressed in Pico farad per foot (pF/ft). High capacitance can hamper the performance of a cable at high frequencies.
- Resistance: The electrical resistance of a cable is a measure of the difficulty it faces in passing an alternating current (AC) through it when voltage is applied. It is expressed in Ohms (Ω). There should be little to no resistance in a cable or wire.
- Velocity of Propagation (Vp): This term refers to the speed at which a signal travels through the length of a cable compared to its speed in free air. In practical applications, a cable slows the speed of electrical signals. This slowing effect is directly dependent on the dielectric material of the cable. Vp is expressed as a percentage of the speed of signal in free space. The lower the Vp, the longer the delay. Hence, choose a wire with high Vp percentage.
- Voltage (Volt): It is the measurement of electrical pressure along the conductor wire. The voltage rating is directly proportional to the insulation thickness of a cable. The thicker the insulation, the higher the voltage rating. Following are the generally used insulation thicknesses and maximum permitted voltage:
- 0.016″ insulation = 300 volts (UL Standards)
- 0.010″ insulation = 600 volts (Military Specifications)
- 0.016″ insulation = 1000 volts (Military Specifications)
- 0.032″ insulation = 600 volts (UL Standards)
Following these guidelines will help you choose a high-performance, and durable wire or cable. If you need further assistance, contact an expert manufacturer, he will be happy to help you choose the appropriate cable for your application.
The growing complexity of modern electronic and electrical systems, along with the ever increasing distance signals are required to travel, have increased the electrical interference in cables. In order to diminish the effects of signal interference in cables appropriate shielding is vital.
Types of Signal Interferences
The primary function or the shielding is to limit the signal from escaping the wire or cable. Besides, it also prevents external interference or signals from flowing into the wire. Depending on the kind of application, cables can be affected by different types of signal interferences. These include:
- Electrostatic interference
- Electromagnetic interference
- Radio frequency interference
Types of Cable Shielding Popularly Used in the Industry
Mentioned below are the most popular types of cable shielding that are used in the wire and cable industry today:
- Foil Shields: They are generally constructed of a Mylar and aluminum composite tape. They are lightweight, economical, and easy to use. They are normally grounded with a drain wire, and provide 100% shield coverage. Although foil shielding provides good flexibility, it can be damaged in high-flex applications.
- Braid Shields: This is the oldest form of shielding, and is still used in the industry. It is a woven pattern consisting of small gauge wires. Braid shields are mostly made up of bare, tinned, or silver plated copper, and aluminum or steel. They have a typical coverage of 55% to 95%.
- Spiral Shields: This shielding is made up of single strands of wires, which are spirally wrapped around the cable core. This shield is more flexible, and easier to terminate than the woven braid. They have a typical coverage of 95% to 98%. As they are most effective in the audio frequency range, they are typically used in audio and microphone cables.
- Tape Shields: This shielding is made from various types of materials. They normally comprise a laminate of aluminum and polyester layers, which is combined together with an adhesive. These shields are fragile, and offer considerable mechanical strength. Some of the popularly used tape shielding are:
- Bonded Aluminum Polyester
- Aluminum/Polypropylene (AP)
- Aluminum/Polyester/Aluminum (APA)
The cable shielding types mentioned above serve specific applications. Hence, you must consult a manufacturer or supplier to understand which shielding can suit your needs.