Connections: purpose, types of connections. Examples, advantages, disadvantages of types of connections

Machines and machines, equipment and household appliances - all these mechanisms in their design have many details. Their qualitative connection is a guarantee of reliability and safety at work. What types of connections are there? Their characteristics, advantages and disadvantages consider in more detail.

Classification

Different types of connections can be divided into two main groups. The first of which, according to the principle of action:

• Movable. Parts can move relative to each other.
• Motionless. Both parts of the part are rigidly fixed to each other.

In turn, each kind of the previous classification can be carried out by two methods of connection:

• Detachable. It is used when periodic replacement of parts is required, assembly and disassembly of the mechanism as a whole. These are the following types of connections: threaded (with the help of running bolts), gear, keyway, etc.
• All-in-one. Such compounds can be dismantled only by mechanical action, in which the mating parts are destroyed. What are the types of connections? Among them - welding, gluing, riveting, flaring, crimping, fit fit, stitching, punching, etc.

So, let's consider in more detail the main types of joints of parts.

Threaded method

Old and long-tried option of fastening. For him, the following elements are used: bolts, screws, pins, screw ties and others. Fastening is carried out due to threads on the fasteners and in the hole of the part. Spiral ledges on the rod and in the process opening of the parts are called thread. Let's consider the basic fixing products:

• The bolt is a threaded rod, at one end of which there is a fixing head. Its shape is hexagonal, square, round, etc.
• The screw differs from the previous product in that a slot (slot) is located on the head for a screwdriver. It can be hexagonal, straight, crossed, etc. By the type of the head of the product can be secret, cylindrical, semicircular, half-secret.
• The stud is a rod with a thread at both ends. Unlike previous versions, it does not have a head.
• The fixing pin at one end has a slot.
• A nut is a prism with a through hole or plugged on one side.

These washers produce washers: flat, spring, deformable. This fixation is used everywhere.

Keyway

The dowels fix the shaft with the parts that impart rotation and oscillation. The design of such elements can be prismatic, wedge, segmented, tangential. Such fasteners form the following types of connections:

• Strains are carried out with the help of prismatic segmented keys. When assembling, there is no prestress.
• Strained are produced by tangential and segmented keys. The assembly voltage appears during assembly. Used for complex mechanisms.

Toothed (splined) joints

Fastening occurs due to protruding teeth on the shaft and deepening under them in the hub. The sizes are fixed by standards. This method is used for moving and fixed attachments.

There are three types of hardening fixation: light, medium, high. The difference is in the number and height of the teeth. It lies in the range of 6-20 pieces. Teeth form:

• Triangular are of little use. Used for small fixed shafts and with a small torque.
• Directly. They are centered along the lateral faces, both inside and outside diameter.
• Involute. Used for large shafts.

Where are these species used? The purpose of the connections of such a plan is the transfer of torque. The most famous application is power tools.

We looked at detachable mounts. Next, we will study the main types of connection of all-in-one.

Welding

What are they special about? Such types of joints are formed by heating and fusing the material at the attachment point to form a weld seam. This clutch is considered one of the most common. There are several options for welding. The most popular of them are:

• Electric arc welding. Three main subspecies can be distinguished: automatic under flux (high productivity and quality, used in mass production), semi-automatic under flux (used for short intermittent seams), manual (reduced speed of productivity, quality depends directly on the experience of the welder).
• Contact welding. It is used in mass production for fine-leaved metal. The seam is overlapped.

One of the popular mounting options is presented in the photo. Often used in suburban construction.

Soldering

Unlike welding at the time of soldering, the metal surface does not heat up to the reflow temperature. The role of the binder is performed by molten solder, which has a lower melting point. This method of adhesion is used for small parts. This is due to the restriction of the gap between the surfaces of the parts.

Adhesive joints

For such fastening, no heating of the surfaces is required. Under each kind of metal, its glue is selected, which will ensure tight adhesion. For such operations, the parts are prepared. The surface is ground, degreased, a special primer is applied, then the gluing operation is performed. The compositions used have additional properties and adhesion to different surfaces.

Locking fixation

This method of adhesion is used mainly for joining sheet metal and shaped profiles. Technological hole in the surfaces is carried out by drilling, then rivet is inserted. Due to the mechanical action, the rod and the head are deformed, fill and fix the hole. Such an operation is carried out manually and mechanically. The rivets fix a material that is not amenable to welding, soldering, gluing, and to details where it is necessary to delay the destructive process.

Connections with interference

It is made by fitting the seats of the parts. Coupling occurs due to the frictional force. In general, this species is considered to be one-piece. But this is conditional. In practice, however, dismantling and replacement of parts is carried out.

Advantages, disadvantages of types of connections

Each fastener has its own characteristics. Consider all the options in terms of advantages and disadvantages:

• Threaded. Withstands heavy loads, reliable grip, a wide range of products, ease of installation and dismantling, the ability to apply mechanization, low cost. Disadvantages: increased number of stress concentrates, reduces resistance.
• Keyway. Simple design, easy installation and dismantling. Disadvantages: the slot for veneer due to the reduction of the section of the shaft and the hub weakens them. This is also due to the concentrations of torsional stresses and bending stresses. Labor-intensive process of manufacturing fasteners.
• Toothed. It creates good grip and precise direction of axial movement, transfers more torque, fewer parts, reliability with reversible and dynamic loads, less weakening of the shaft, reduced length of the hub. Disadvantages: increased price, complex production technology.
• Welding. Low cost of work, the connection is sealed and dense, the use of automated processes, the ability to work with a thick profile. Disadvantages: for manual welding, the quality depends directly on the qualification of the worker, the deformation of the surface of the parts during heating, low reliability in vibration and impact.
• Soldering. There is no deformation of the surfaces of parts, high accuracy, the possibility of soldering. Disadvantages: complex process of preparation of the bases, minimum clearance should be provided.
• Adhesive. Low cost, there is no weakening of the working section, the possibility of combined use with other types of fasteners, tightness of the joint, increases the anticorrosive properties of the joint, resistance to water, chemistry, temperature changes, prostate application technology. Disadvantages: thorough preparation of the substrate, if the composition is incorrectly selected, strength characteristics may be reduced.
• Knotty. The possibility of applying to materials that can not be welded, reliability, prevents the appearance of fatigue cracks. Disadvantages: labor intensity, material consumption, the process of deformation of the surfaces of parts due to mechanical action.
• Connections with interference. The design is quite simple, a good arrangement of parts relative to each other, withstands high loads. Disadvantages: uneasy assembly, strength is dissipated under the influence of vibrations and vibrations.

As you can see, each species has its advantages and disadvantages. Considering these factors, they select the optimal types of fasteners in each specific case. Consider where different connections are used.

Types of connections. Application examples

Threaded, glued, welded joints are found everywhere in any industry. For example, construction, furniture, heavy industry and so on. Keying and spline fixation is widely used in power tools, equipment, machinery. Connections with interference are installed on the shafts of the toothed rings, worm wheels. Soldering is often used in work with electronic systems, where maximum accuracy is required. Padded is used to sew sheets of thin metal. However, as shown in the last photo, with the help of rivets it is possible to fasten a fairly large channel. This is only a small list of application of individual mounting options.

We can say that with the technical progress the technology of coupling is developing rapidly, and this means that new types of joints of parts will appear. The modern world is filled with aggregates, machines and mechanisms. The quality and service life of the nodes depend on how firmly the parts are fixed. It is also important that the connection does not distort the shape of the product and does not introduce additional changes to the design. Therefore, it must comply with technological standards. If they are observed, the number of emergencies at the enterprises will be reduced several times, and the units themselves will last very long.

So, we found out what kinds of joining parts.