Cable harnessing assembly is a common practice in the construction and automobile industry that binds cables that transmit power from point A to B. The objective is to have a compact cable connection and avoid a scenario where many different power transmitting cables are loose and all over the place which is hazardous. In cable harness assembly, the said wires are bound by conduit, electrical tape, cable ties, straps, cable lacing, sleeves, a weave of thrusted out string or even a combination of two or more of the above. Cable harnessing is extremely advantageous especially for automobiles, aircraft, and buildings as without it; wires would hang loosely making a mess, a potential hazard not forgetting the amount of space such wires would occupy; a few kilometers at the least.
When cables are harnessed, they are protected from the effects of vibrations, moisture, and abrasions. The different ways that wires are harnessed into depends on their intended use as well as the electrical and geometric requirements. When power transmitting wires are bound together, the risk of getting an electric shock is minimized, and binding them into flame-retardant sleeves, reduces the chances of electrical fires.
The Purpose of Cable Harnessing
Items that require wire harnessing are all around us; from household items like the washing machine, refrigerator, and dryers to heavier and more complex machines such as cars, industrial equipment, and construction machinery.
When building a large electrical device, wire harnessing simplifies the process by integrating the wiring into a single unit or many small units for easier installation. This also helps a lot in the event single wire malfunctions as diagnosis and troubleshooting can be easier to accomplish compared to if the wires are not harnessed.
When it comes to installation, instead of say 100 wires, the original equipment manufacturer has only one item to connect. This also saves a lot of time, energy and man hours. In addition, the wire harness allows the wires and supply of electric power to be stable and secure by narrowing the wires in a non-flexible bundle while also saving on much-needed space.
Wire Harness Assembly Process
The process of wire harnessing is delicate and a process that is carried with a lot of care as if one wire does not transmit power, the entire process has to be re-done. Mostly, the assembly and testing go hand in hand to compliment each other.
The first important step in this process is to get the design of where the completed harness will be used. When that is accomplished, the wires that will be harnessed are cut to length and markings are used to identify them, and this could be courtesy of labels or different wire colors. At the end of the wires, pins or contacts are fixed, and this could be by soldering them, crimping or welding to hold them in place. After this process, they are then inserted into connectors depending on the specifications. Sometimes all the wires are fitted into connectors, other times; it’s only some of the wires. When that process is completed, the wires are then terminated with spades, ring lugs or left bare to be terminated at their final destination.
Once the completed harness has been finished, it is then tested to ensure the wires transmit power. Errors are discovered at this stage, if there are any, and in case some are discovered, the harness is sent back to the assembly area for repair and to correct the defect. When being repaired, the harness has to be connected to a source of power to be able to identify the problem correctly.
Wire Harness Testing
The wire harness assembly plant tries very hard to detect any problems as early as possible to save time, and maintain quality while bringing assembly costs down. In the process, valuable lessons are learned on root cause problems for future reference.
The system that most wire harness assembly plants use to install harness boards and detect issues is a combination of software and hardware which provide a seamless process for construction and subsequent tests. The software system can be used to control the CR tester and the high voltage CH2 tester. When harness boards are back-wired, testing can be carried out with little or no modification required which saves time. This process is called by assemblers the easy wire system.
This system comes with accessories that help the assembler to put together the harness board and include; bracket bases, grid tiles, brackets, connector holders and nail brackets.
Harness Board Set-Up
In cases where a harness board is required, plywood is cut to the required size and 3.85-inch margins are made on the board’s right and left sides. Each grid tile measures 3.85 inches. The tiles are then joined by clips and placed down and screwed to the plywood edge. The drawings that the assembler has are then compared to the grid board to ensure they are square. Finally, the brackets are attached to the board, and the wires are connected.
Test programs can be created within the software, or electronically imported and contain all the information needed to build and test the harness.
First and second end pinning.
Most of the time, wire harnesses are assembled using the two end method’ where one end of each wire is terminated and installed into a main or trunk connector. The opposite ends are then routed to other connectors.
The assembler has to connect each wire to its respective cavity then and in the event, the wires are labeled, the operator reads the label, looks up the corresponding cavity in a table and then connects the wire. This is a very error-prone and time-consuming process especially when it comes to connectors with hundreds of wires.
With the easy wire system, it is much simpler as the operator only has to touch a wire at the end point connector and automatically it shows where the wire comes from, and where it is to be connected. This is courtesy of an on-screen graphic of the touched connector displayed, with the target cavity highlighted in green.
If the wrong connector is inserted into the wrong cavity, there is a sharp beep which alerts the operator. While when the connector is inserted in the right cavity, the beep tone is not sharp which means the connector is in the right cavity.