Nowadays people make big demands on the quality of assembling and reliability. That means that every assembly and every car’s detail must meet these requirements.

A composite element of a car is an electric wiring loom. A loom is a complete product, which consists of fastened together separate wires, the ends of which are terminated with contacts. These ends are collected into blocks and different protective elements, like tubes, rubber caps or covers, can be put on them. The wires are clamped into looms by a casing, made of sticky tape PVH, cable clamping and termotubes.

Today’s automobiles have got looms consisting of 300 + wires, terminated with different contacts. The reliability of such a complex product depends on several factors. Firstly, these are demanding requirements on the quality of materials and complete sets, these influences a choice of a supplier.

The next factor is the usage of modern, highly productive and accurate measuring equipment, which meets world standard requirements. And, finally, the most important factor is the specialists, which take part in the production process. Their professionalism influences the quality and reliability of the product.

The looms for tractors can be divided into looms with wires of low and of high tension (storage and starter wires are very often single, rarely consists of two or three wires).

A technological process of loom production is divided into several stages: cutting of the wires, stripping insulation off the ends of the wires, terminating of the wires with lugs or contacts, binding of the wires into looms, setting of demountable joinings and quality control.

So that you could better imagine the peculiarities of complete sets, which construct the looms and in what order they are used in the production process, we managed to give a detailed description of the main stages of loom production. You will also be able to learn different kinds of complete sets, which are used in this process.

In this section we introduce the structure of a loom, so that you could better understand the succession of a loom assembly. A loom can be divided into several parts and each part bears its own name. Here (pic.1) you can see the example of a loom, which consists of:

1. a stem of a loom – the part of the loom with the biggest quantity of the wires, bound together
   
   
2. a tapping - a bundle of the wires, which is connected with the stem of the loom or with the other tapping
   
   
3. a place of the tapping – the place of divergence of two or more bundles of the wires at an angel (angles)
   
   
4. a lug – the elements, which help to mount or to dismount a loom with cold contacts
   
   
5. connection devices – the devices, which help to connect simultaneously one or more pairs like “loom - contact”
   
   
6. protective elements – rubber products, which serve for mechanical or chemical protection of the tapping place of the lug or of the connection device with instruments and other electric equipment of a car

Stages of loom production

If we collected all the elements of the loom, they would look like it is shown in the pic.2. To collect a loom you should know the succession of the stages of loom assembly. Just below you can read about the succession of hand assembly of a custom-made loom (pic.3).

Cutting of wires

Cutting of wires can be carried out with the help of hand devices or a special machine for cutting. The choice between hand and computer-aided ways of cutting depends on the process of loom production.

Clamping of wires into looms

Wires are clamped into looms with the help of tyres, made of sticky tape PVH (GOST 16214-70), and also with the help of cable braces (pic.5). This process is hand-made or special instruments can be used. Here (pic.6) the stem of the loom is shown: cable braces bind the wires.

Taking into account wishes of the customers, wires in the looms can be protected and bound into the looms by the tube PVH or wound by sticky tape PVH (pic.7), spiral tape (pic.8) or by a crimped tube.

A tyre or other elements should fasten a tube PVH and a spiral tape. That protects it from unwinding. The ends of the crimped tube are protected by a termotube (pic.9) or by special rubber coverings, which are selected according to the diameter of the tube.

The tyres are put on every place of tapping so that the distance between the tyres is not more than 250 mm (in case if the distance is not shown in the drawing). What concerns the looms in the crimped tube, here a branch is put on the place of tapping in order to protect it from mechanical influence.

Stripping insulation off the ends of the wires

Stripping insulation off the ends of the wires is carried out automatically while cutting or by hands (pic.11) with the help of a pair of pincers in order to strip insulation off. The usage of machines and special hand instruments guarantees qualitative process of stripping.

Terminating of wires with lugs

Terminating of wires is carried out by the method of a cold pressure test (pic.12 – a hand-method, pic.13 – a half-automatic machine). This method provides a reliable contact of a wire with a lug. A section of the wire, where the lug is pressed, has a form of a heart. Every wire is deformed and it looses its round shape, filling in the vacuum and in that way providing a maximum square for the contact with the lug. The lugs, which correspond to the technical standards, are used to provide a high quality contact.

The usage of modern pressure tests provides a reliable mechanical connection and the exertion of the break meets the demands of GOST 23544-84 and is controlled by special devices (pic.14).

In the process of loom production tinning is used after the pressure test. It produces more qualitative electric contacts, more reliable mechanical connections and gives protection from corrosion. High demands to the quality of the connection between the wire and the lug can be explained by the increased current tension in the place of their contact. And it increases the heating of the contact. While the product is in use, it may lead to the break, to the short circuit and even to the inflammation of the wire.

A check–up of the quality

It’s the last stage, where loom’s ability to work is tested. It consists of several phases; some of them are intervening in the process of loom production:

• checking of terminating of wires with lugs (pic.14)
  
  
• checking of stripping insulation off the ends of the wires
  
  
• checking of maximum size divergence of the loom elements
  
  
• checking of fastening of wires into looms
  
  
• checking if the structure of the loom corresponds to the documentation
  
  
• checking of the integrity of electric circuits

You can get aquatinted with every method of testing in
GOST 23544-84.

In the company “Complexzchgut” there are electrical stands where one can check the integrity of electric circuits. All kinds of looms, which can be placed into the connection devices of the stands, can be tested here.