The process of producing electric harnesses:
Cutting and stripping of wires
The first step in making cable harnesses is cutting and stripping of cables. The cables are cut in accordance with the demand for the length of the planned harness and the tolerance of the length of the finished product is taken into account. Normally, the customer specifies the tolerance of the cable length, which we take into account in the final dimensions. In addition to cables and harnesses, heat-shrinkable insulations, conduits, tubes and others are cut at the same time.
For the appropriate cutting of electrical cables, our company has a dedicated machine park equipped with precise machines for automatic wire cutting and insulation stripping. Automation of the process of cutting and stripping of wires allows for a significant increase in efficiency and precision of wiring harnesses. Cables with insulation are cut simultaneously, and with one / two / three / four-wire cables, the insulation can be removed automatically. In the case of cables with more wires or when they are made of materials difficult to machine, the cutting is divided into two stages. The first is to automatically remove the outer insulation during cutting. The second step is manual stripping of the internal wires, which also allows the wires to be twisted to obtain a frayed, uniform end of the bundle.
Labeling and marking
This activity is aimed at speeding up the process of identifying the type of a given cable. It also facilitates the subsequent assembly process at the customer’s site, as well as maintenance and finding the cause of a possible failure. Our company has dedicated printers for labels and a laser marking machine, which are perfect for the correct marking of wires.
How is the wire marking process performed? The most common and easiest way to mark individual wires is to use different colors of their insulation. However, you can also use markers made of heat shrinkable tubing that additionally act as insulation.
There are five basic groups of wire coding according to color:
- brown or black – phase wire,
- blue – neutral wire,
- yellow-green – PE protective conductor,
- red – direct current cable plus,
- black or blue – direct current wire minus.
In practice, however, the colors of the cables are much more diverse.
Wiring harnesses are also marked with letters and numbers. Such marking informs about the conductor structure and usually consists of three parts:
- letter – informs about the structure and material of the conductor, the material used to create the insulation and coating, as well as other supplementary information,
- digital – informs about the rated voltage of the insulation,
- digital – informs about the number and section of conductor.
There are times, however, when color coding is insufficient to be considered adequate, unambiguous information. Then, printed markers are used, most often made on a self-adhesive tape, heat-shrinkable tube, the so-called self-laminating label or protective tube. This method allows you to use several colors of markers, as well as the imprint made on them, and above all, it allows you to place any text content desired by the customer.
Crimping or soldering the terminals
almost every wiring harness has terminals, that is, various types of contacts. Sometimes also called pins. There are two basic types of contacts – open barrel and closed barrel. Crimping can be done with hand tools but the best option is to use a press with applicators for connectors. An electric, pneumatic or semi-pneumatic press allows you to connect electric wires and wires with electronic components in a fully automatic way. There is also a different solution, which are non-stripping connectors which perforate the insulation during crimping, this is the so-called IDC (insulation displacement connection). They are most often used with ribbon cables. They allow you to easily obtain a multi-core connection, mainly for cables that do not need large wire cross-sections i.e. signal cables or low currents.
Taping or binding with cable ties
the main purpose of taping and binding with cable ties is to keep order among various types of cables and to protect them from possible damage. Additionally, this process enables the bundle to be formed and kept in the desired shape. Thanks to this step, it is possible to properly fix, group and segregate cable bundles and wires. This facilitates assembly and avoids cable tangling, which contributes to safer functioning. It also allows transparency in the event of repair or service.
Various types of ties are used for the cable harness, often with specialized applications, depending on the conditions in which the cable will be located.
There are three main types of cable ties: inner and outer serrated, and with no serration. The former are intended for bundling standard cable bundles and wires, the latter are intended for cables with delicate insulation, while the latter are used to organize cables with large diameters. In addition, there are also fastened (temporary, reusable) and non-detachable (permanent) ties. During this process, the assembly of covers (e.g. corrugated tubes, smooth tubes, braids) is also performed, and in the strapping process – conduits, tension, artificial and metal braids.
a mandatory step during the entire production process of cable harnesses and it is conducted according to the, so-called, control plan. It consists of the careful examination of the correctness of the harness design, its target length and precise cutting, as well as appropriate condition of the insulation. The heat treatment of heat-shrinkable elements (e.g. made with a hot air heat gun, spot or industrial heat gun) is also controlled. The check consists of setting the appropriate temperature so that the harness does not lose its operation. The correct shrinkage of the insulation (e.g. 1:2, 3:1) relative to the initial diameter is also monitored. Each of the production stages is carefully controlled so that the harness as a final product is of the highest quality.
Installation of the wiring harness
one of the last stages of the production of wiring harnesses is their assembly. The assembly of electrical harnesses in the machine takes place on the customer’s request and differs in the degree of complexity depending on the type of machine to which the harness is attached. The assembly of electrical connectors includes placing the contacts in the housings and connecting. The exact fit of the contact and proper seating in the connector is checked. The tongue and pawl must be inserted into the coupling in a tight, well-fixed way. Sometimes, however, you need to tighten the harness using the right amount of force. Overtightening will prevent the harness from conducting properly.
Final quality control of the finished wiring harness
checking the correct operation and overall execution of wiring harnesses is a key step carried out before sending to the customer. The quality control of the harnesses is performed at every stage of cabling production, checking such elements as the dimensional accuracy of the cut, insulation, crimping geometry, tensile strength, etc. At the end, however, the correctness of the harness operation and compatibility with the device to which it is to be connected are carefully checked. The finished product is tested for correct electrical connections, no short circuits and continuity of insulation.