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Elena works as a design engineer, designing harnesses and wiring for piston engines. Using personal experience, she talks about how to make an electric harness for auto and motorcycle purposes with her own hands: how to do it and not to do it, about available materials, and the nuances of step-by-step laying and laying the harness.
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Cars are currently subject to high requirements for build quality and reliability. Accordingly, each unit and part of the car must meet these requirements.
An integral element of the car is the electrical wiring (wiring harnesses). A wiring harness is a finished product consisting of individual wires fastened together in a bundle, the ends of which are reinforced with contacts that are assembled into blocks or protective elements (tubes, rubber caps, covers) are put on them. The wires are fastened into bundles: bandages made of PVC adhesive tape, cable ties (toothed clamps made of thermoplastic polymers); heat shrink tube.
A modern car has harnesses with a total number of wire segments of about three hundred (and more often more), reinforced with various contacts. The reliability of such a complex product depends on several factors. First of all, these are increased requirements for the quality of components and materials. Which, in turn, is influenced by the choice of supplier and the conduct of incoming control.
The next factor is the use of modern high-performance and precise production and control - measuring equipment that meets the requirements of international standards. And, finally, the most important factor of reliability is the specialists involved in the production process. The quality and reliability of the product depends on their professionalism.
Autotractor harnesses can be divided into: low and high voltage wiring harnesses (battery and starter wires are most often single, less often - consisting of two or three wires).
The technological process of manufacturing a wire harness is divided into several basic operations: cutting wires, stripping the ends of wires from insulation, reinforcing wires with lugs or contacts, fastening wires into bundles (binding), installing detachable connectors, quality control.
In order for you to better understand what components the wire harnesses consist of and in what sequence they are used in their manufacture, we tried to give a detailed description of the main operations for the manufacture of harnesses and the types of equipment used.
For a better understanding of the assembly sequence of any harness, in this section we will introduce the general concepts of the structure of the harness, which will be encountered later in the text. The harness can be divided into parts and give them names.
- The trunk of the harness is the part of the harness with the largest number of wires collected in a bundle.
- Branch - a bundle of wires extending from the trunk of the harness or other branch.
- Branch point - the place where two or more bundles of wires diverge at some angle (s).
- Tips - elements that allow the installation and dismantling of a harness with cold contacts.
- Connecting devices - devices complete with lugs that allow simultaneous connection of one or more pairs of "pin - socket".
- Protective elements - rubber products designed for mechanical and chemical protection of the junction of the tip or connecting device with devices and other electrical equipment of the vehicle.
Harness manufacturing operations.
If you put together the elements that make up the bundle, then they would look something like the one shown in the photo (Fig. 2.) To assemble a bundle from them, you first need to know the sequence of operations for assembling the bundle. The manual assembly sequence (Fig. 3) for a non-serial harness is described below:
Wire cutting.
Wire cutting is carried out using a manual device or a wire cutter. Depending on the program for the production of bundles, a manual or automated cutting method is used.
Bonding wires into bundles (knitting).
The wires in bundles are fastened with bandages made with PVC adhesive tape according to GOST 16214 - 70, cable ties (toothed clamps made of thermoplastic polymers according to GOST 22642.3-80) manually or using a special tool, by welding the wires laid out on the same plane to the fastening element made in the form of a PVC tape or one of the wires of the zigzag bundle.
By agreement with the consumer, wires in bundles can be protected and bundled with a PVC tube, wrapped with PVC adhesive tape, spiral tape or corrugated tube.
The PVC tube and the spiral tape on the bundle must be fixed with a bandage or in other ways that exclude its movement and unwinding, respectively. The ends of the corrugated tube are usually protected by a heat-shrinkable tube or special rubber covers, which are selected according to the diameter of the tube.
Bandages are also applied at each branch point and on the branches themselves in such a way that the distance between the bandages is no more than 250 mm, if the distance is not indicated on the drawing. A splitter is installed on the bundles in the corrugated tube at the branch point to prevent the tube from moving at the junction and to protect the branch point from mechanical influences.
Stripping the ends of the wires from insulation.
Insulation stripping is carried out automatically, when cutting with a dimensional cutting machine, or manually using insulation stripping pliers, depending on the bundle release program. The use of machines and special hand tools guarantees high-quality stripping without insulation residues and without cutting copper wires.
Reinforcement of wires with tips.
Reinforcement of wires is made by method of cold pressing in the manual or semi-automatic way. This method ensures reliable contact of the wire with the tip. The cross section of the wire in the place of the molded tip has the shape of a "heart". Each strand wire is deformed, losing its round shape, filling the voids and thereby providing the maximum contact area with the tip. Tips corresponding to normative and technical documentation are used to ensure high-quality contact.
The use of modern presses gives a reliable mechanical connection, the breaking force of which meets the requirements of GOST 23544-84 and is controlled by special devices.
In the manufacture of battery and starter harnesses, after pressing, tinning is used. It gives a better electrical contact, a more reliable mechanical connection and protection against corrosion. The overestimated requirements for the quality of the connection of the tip with the wire are explained by the fact that the place of contact between the wire and the tip experiences an increased current load and thereby increases the heating of the contact area. During operation, this can lead to wire breakage, short circuits, or even wiring fires.
Installation of connecting devices.
After reinforcing the wires with lugs, connecting devices (blocks, connectors) are installed where they were provided.
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Several "crickets" settled in the car. At times they disappear, at times they reappear and poison life. The most unpleasant of them live under the door cards and under the shelf at the back.
Of course, you can turn the music up louder, but then hearing problems may appear).
It was not possible to find some kind of thin material for soundproofing the interior in local markets - they offer either foam rubber or other adhesive-based foam material. However, these options are good for soundproofing the body, trunk or roof of a car.
To eliminate the squeaks of plastic parts on body elements or among themselves, a completely different approach is needed - the material must be thin, insulating the rubbing parts of the car interior from each other.
Those who are "crickets" or disheveled braids of wires do not give rest, I invite you under the cut).
Today, the heroine of the micro-review will be a textile non-woven tape for fastening wire harnesses and gaskets between the decorative elements of the car to eliminate squeaks and extraneous noise.
Regarding squeaks and noises, the solution suggests itself here - something thin on an adhesive basis that is not capable of disturbing the initial relief. Electrical tape is good for fastening wire harnesses, be it plastic or fabric, but the inventors of the monitored tape used it here too - let's see what comes of it.
Came from a distant eastern country in an unsightly, well-sealed package.
Ribbon spool inside
The coil, due to the properties of the material of the tape, is soft and I do not recommend putting pressure on the center of the coil.
The material of the tape is fibrous, reminiscent of agrofabric, but thinner and perforated, due to which it stretches a little, but to break it, you will have to make a noticeable effort.
As you can see, the bottom of the tape is smeared with glue and clings well to surfaces.
Hung for an hour, did not fall off. The weight of the coil is certainly not weight at all, but it still holds up perfectly and peels off with a characteristic sound.
The width of the tape, as promised, is 19-20 mm. I hope they wound all 15 meters) - I didn’t unwind.
Fastening the wires into a bundle was carried out on an old power supply from a computer.
The tape is wound well and creates a tight tourniquet.
You can’t count on water resistance, but out of contact with moisture, the tourniquet will turn out to be what you need.
In addition to the “crickets” in the car, the tape helped to get rid of the rattle of the old TV case at high volume. It was worth making the sound louder and the body began to rattle. Once I saw a similar tape on the TV “from the factory”, but then they saved it.
I made such stickers around the perimeter and the rattle disappeared.
I am sure that I will achieve the same result in the fight against creaking in the car, but I will have to wait for spring - it is already cold outside, and I will not risk removing plastic parts at low temperatures, because there is a chance of damaging the fasteners. Let them creak until spring, maybe even where they appear, then I will catch all the “crickets” at once.
There is nothing special to say about the pros and cons - a simple way to get rid of squeaks, extraneous noise and a convenient tool for harnesses. There is nothing special about the tape, but it is convenient.
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A bundle is a collection of cut wires and cables fastened together in some way and, if necessary, equipped with electrical installation elements (lugs, connectors, etc.).
According to their purpose, harnesses are divided into intrablock and interblock.
Intra-block harnesses are used for the electrical connection of individual units, blocks and electrical parts inside the device, and inter-unit harnesses are used for electrical connection of various radio equipment and devices into a single system. Depending on the location of the nodes in the body, the bundles can be flat or voluminous.
To protect against environmental influences, mechanical damage or for the purpose of shielding, the bundles are wrapped on the outside with a keeper, nylon, lavsan or polyvinyl chloride tape, varnished or enclosed in a shielding braid.
1) different colors of wire insulation;
2) coloring or numbering of PVC tubes used to fix the ends of the insulation (the tubes are numbered
on the machine, in special stamps or inscribed by hand with marking ink);3) plastic tags with a symbol for the connection point, put on the wires.
Harnesses in which failed wires cannot be replaced are provided with spare wires. Their number is taken at the rate of 8 ... 10% of the total number in the bundle, but not less than two wires. The length and section of the spare wires must be equal to the largest length and section of the wires present in the bundle. The length of the harness leads must be sufficient for connection to the nodes and elements of the device circuit without tension; in addition, there must be a margin of 10 ... 12 mm for re-stripping and attaching each end of the wire.
A typical technological process for manufacturing a tow includes the following operations:
cutting wires and insulating tubes;
laying wires on the template and knitting them into a bundle;
termination of the ends of the wires of the bundle with their simultaneous marking;
harness control (continuity); protection of the harness with insulating tape;
output control (visual inspection for compliance with the standard, well, and continuity).
The length of the prepared wires must correspond to the dimensions indicated in the technological map or the table of wire blanks. Wires and shielding braids are cut on automatic machines, as well as using assembly or guillotine scissors and wire cutters.
It is more expedient to make a blank of wires of the same length and knit them into a bundle without branches on a special device (Fig. 1.25), which consists of two racks mounted on a board (the distance between the racks depends on the length of the prepared wires).
On the outer sides, the racks have grooves. First, the wire is wrapped around the posts, while the number of turns of wire should be half the number of wires in the bundle. Then the coils of wire located between the uprights are tied into a bundle with thread or twine. After tying, the turns of wire are cut in places located opposite the grooves in the racks.
With the manual method of harvesting wires for bundles, their length is determined using samples or a ruler. In serial production, special machines are used for measuring wire cutting to a predetermined length.
The wires are laid on the template in a certain order (according to the scheme printed on the surface of the template), after which they are tied with a thread or twine into a bundle. Template markup for
the wiring harness is laid according to the wiring diagram, the layout of the node or device in which the harness will be installed, and the mounting table of connections. On the marked template, the wires are first laid out and then knitted into a bundle (Fig. 1.26). Depending on the design of the device, the bundles are flat or voluminous.
When laying out, the ends of the wires are cut along the transverse "marks, marked and fixed. The laying of wires on the template starts with spare and long working wires and ends with the shortest wires. Shielded wires included in the bundle are wrapped with keeper tape and placed inside harness or in an insulating tube.
The harness should be knitted in one direction with cotton thread No. 00 or linen No. 9.5/5. For hand knitting, the device shown in Fig. 1.27 a. A spool 3 with threads is inserted into the body 4 of the device. Covers 5 and 2 serve to center the coil. In the top cover 5 there is an eye for giving the thread a certain direction, and a hook 1 is attached to the bottom cover.
To facilitate the winding of the thread from the spool, a slot and an outlet for the outer end of the wound spool are made in the body. First, a wound coil is inserted into the body of the device, the upper end of which is inserted into the slot of the body. Next, the lid is closed and the end of the thread is threaded through the eyelet.
The harness is knitted in accordance with the loop formation scheme. It takes 0.5 ... 1 s to knit one knot. To perform the operation, it is necessary to take the thread (see Fig. 1.27, b), hook the loop, stretch it under the tourniquet and thread the device through two loops, tightening the thread. At the moment of tightening the knot, the thread passing through the body must be pressed with a finger to its surface. The device helps to improve the quality of knitting harnesses and reduce the complexity of their knitting by 15...20 times. Recommended knitting methods are shown in fig. 1.28.
Loops are recommended to be knitted with tension at regular intervals (no more than 50 mm), as well as in places where wires branch off.
The knitting step of the loops is set by the designer, depending on the diameter of the bundle.
After knitting the wires into a bundle, their ends are terminated. First, all ends of the wires are marked according to the wiring diagram, and then the correct layout of the wires is checked with a dial tone. In the case of using electrified templates for making harnesses, continuity can be omitted.
The control of complex harnesses is carried out on special semi-automatic stands according to a given program. The harness on the panel of the stand is fixed manually, and the correct layout of the wires and the resistance of their insulation are controlled automatically.
First, control is carried out for compliance with the electrical wiring diagrams, that is, checking the correct layout of the wires. For this purpose, the required voltage is sequentially applied to one of the ends of the tested wire. With the correct layout of the wires, the voltage should be fixed in all wires of the bundle electrically connected to the wire under test. Next, you need to make sure that there is no voltage in the wires of the bundle, which are not electrically connected to the wire under test. All information about the control is issued automatically in the form of coded holes on a punched tape or as a record on a tape with digital and alphabetic designations.
When monitoring the insulation resistance of wires, a consistent supply of constant voltage is automatically carried out to electrically isolated wires (circuits), while fixing the insulation resistance.
If necessary, the harness is protected with insulating tapes or a shielding braid. Finished bundles are laid according to the wiring diagram and the drawing of the device. Simultaneously with laying, the ends of the wires of the bundle are bred to the corresponding places in the device circuit and soldered. At the same time, it is necessary to ensure that individual wires do not obscure the markings and inscriptions of the nominal values on the parts.
Attention! When laying the harnesses in the device, care must be taken to avoid breakage and breakage of the conductive cores of the wires and conclusions of the hinged radio components, as well as the short circuit of the bare conductive places.
Inside the device, the harness is attached to the chassis or walls with metal brackets (Fig. 1.29), under which you must first
put insulating materials made of polyvinyl chloride, varnished cloth or pressboard. The edges of the gaskets should protrude from under the bracket by at least 5 mm. The brackets are made double-sided (attached with two screws) and one-sided (attached with one screw). The design of mounting brackets, especially single-sided ones, must be sufficiently rigid to prevent them from bending or deforming when attached to the chassis together with the harness.To ensure the transition of unshielded (and, if necessary, shielded) harnesses from one unit of the device to another through the wall of the chassis or screen, insulating bushings are provided in this place.
Very useful and necessary harnesses for grabbing wires can be made from a plastic bottle. Harnesses can be of almost any size and any number of wires can be laid in them. To anyone who has a computer at home, I recommend taking this master class to heart. Since thanks to him you can easily organize order near the PC, where bundles of wires always lie.
Of course, the use is not limited to this. The bundles additionally insulate the wire, protect it from mechanical influences, from excessive bending, etc. So there are just a lot of options for use and application. And most importantly, everything is made from useless recyclable materials - a plastic bottle.
It will take
- 5 washers.
- 2 screws.
- Wooden block.
- Nail.
- Blade from a clerical knife.
- Some copper wire.
Making a twisted tourniquet from a bottle
The first step is to make a bottle cutter, which will cut a plastic bottle into a narrow ribbon. We put two shabs on a wooden block at a short distance.
From above we put the blade from the clerical knife and the washer on the edge of the blade without a hole. To reduce the blade blade should be broken off to the desired length.
We fix the entire structure with self-tapping screws. The bottle cutter is ready. The thickness of the two lower washers determines the thickness of the future tape, so if you need a thicker tape, put one or more washers on each side.
Now we fix the bar. Cut off the bottle skirt with irregularities.
We dress the bottle on the bottle cutter. We press on the neck and turn the bottle with a rotary motion so that the knife begins to cut the skirt.
Next, we grab the ribbon that appears and pull without reducing the pressure on the neck from above.
We reach the top of the bottle and we can stop there.
We take a nail and fasten the beginning of the tape at its head.
We wind tightly the coil to the coil of the tape on the nail and fix it with a wire on the other side.
We blow with a building hair dryer for one minute the twist along the entire length. Instead of a hair dryer, you can lower the twist into boiling water for 1-2 minutes.
We remove the clamps from the wire.
The harness now retains its shape.
Stretches well and returns to its original position.