Machines and machine tools, equipment and household appliances - all these mechanisms in their design have many details. Their high-quality connection is a guarantee of reliability and safety at work. What types of compounds are there? Their characteristics, advantages and disadvantages will be considered in more detail.
Classification
Different types of compounds can be divided into two main groups. The first of which is based on the principle of action:
- Movable. Parts can produce movement relative to each other.
- Motionless. Both parts of the part are rigidly fixed to each other.
In turn, each type of the previous classification can be carried out in two ways of connection:
- Detachable. It is used when periodic replacement of parts, assembly and disassembly of the mechanism as a whole is required. These are the following types of connections: threaded (with the help of running bolts), gear, key, etc.
- One-piece. Such connections can only be dismantled by mechanical action, in which the mating parts are destroyed. What kind of compounds are these? Among them are welding, gluing, riveting, flaring, crimping, interference fit, stitching, punching, etc.
So, let's take a closer look at the main types of joining parts.
Threaded method
An old and long-tested mounting option. The following elements are used for it: bolts, screws, studs, screw ties and others. Fastening is carried out due to the thread on the fasteners and in the hole of the part.
Spiral protrusions on the rod and in the technological hole of the parts are called threads. Consider the main fasteners:
- The bolt is a threaded rod, at one end of which there is a mounting head. Its shape is hexagonal, square, round, etc.
- The screw differs from the previous product in that there is a slot (slot) under the screwdriver on the head. It is hexagonal, straight, cross, etc. By type of head, the products are countersunk, cylindrical, semicircular, semi-secret.
- A hairpin is a threaded rod at both ends. Unlike previous options, it does not have a head.
- The mounting pin at one end has a slot.
- Nut - a prism with a through hole or plugged on one side.
Washers are produced for these hardware: flat, spring, deformable. This fixation is used everywhere.
Keyed
The dowels fix the shaft with parts that transmit rotation and oscillation. The design of such elements can be prismatic, wedge, segment, tangential. Such fasteners form the following types of joints:
- Unstressed are carried out using prismatic segment keys. There is no prestress during assembly.
- Tense are produced by tangential and segment keys. During assembly, mounting voltage appears. Used for complex mechanisms.
Toothed (spline) joints
Fastening occurs due to the protruding teeth on the shaft and the recesses under them in the hub.
The sizes are fixed by standards. This method is used for movable and fixed mounts.
Three types of fixation by stiffness are distinguished here: light, medium, high. The difference is in the number and height of the teeth. It lies in the range of 6-20 pieces. Teeth Shape:
- Triangular are not very popular. Used for small fixed shafts and with low torque.
- Straight-line. They are centered on the side faces, along the inner and outer diameters.
- Involute. Suitable for large shafts.
Where are these species used? The purpose of the connections of such a plan is the transmission of torque. The most famous application is power tools.
We examined detachable mounts. Next, we study the main types of one -piece connections.
Welding
What are they special about? These types of joints are formed by heating and depositing material at the attachment point with the formation of a weld. This clutch is considered one of the most common.
There are several welding options. The most popular of them:
- Arc welding. Three main subspecies can be distinguished: automatic submerged arc (characterized by high productivity and quality, used in mass production), semi-automatic submerged arc (used for short intermittent seams), manual (reduced productivity rate, quality depends directly on the experience of the welder).
- Contact welding. It is used in mass production for sheet metal. The seam is lapped.
One of the popular mounting options is shown 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 clutch method is used for small parts. This is due to the limitation of the gap between the surfaces of the parts.
Adhesive joints
Such fastening does not require heating surfaces.
For each type of metal, its own glue is selected, which will provide a tight grip. For such operations, parts are prepared. The surface is ground, degreased, a special primer is applied, after which the gluing operation is performed. The compositions used are distinguished by additional properties and adhesion to various surfaces.
Riveting fixation
This coupling method is mainly used for joining sheet metal and shaped profiles. The technological hole in the surfaces is carried out by drilling, then riveting is inserted.
Due to mechanical action, the rod and head are deformed, fill and fix the hole. Such an operation is performed manually and mechanized. Rivets fix material that is not amenable to welding, soldering, gluing, and to parts where the destructive process must be delayed.
Interference fit
It is made by fitting the seats of the parts. Coupling is due to friction. Basically, this species is considered one-piece. But this is conditional. In practice, they still dismantle and replace parts.
Advantages, disadvantages of types of compounds
Each fastener is distinguished by its characteristics. Consider all 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 use mechanization, low cost. Disadvantages: increased amount of stress concentrates, reduces resistance.
- Keyed. Simple design, easy installation and disassembly. Disadvantages: a groove for veneer by reducing the cross section of the shaft and the hub weakens them. This also occurs due to the concentration of torsion and bending stresses. The laborious process of manufacturing fasteners.
- Toothed. It forms good adhesion and the exact direction of axial movement, transmits more torque, fewer parts, reliability under reverse and dynamic loads, less shaft weakening, and a shorter hub length. Disadvantages: increased price, sophisticated production technology.
- Welding. Low cost of work, the connection is tight and tight, the use of automated processes, the ability to work with a thick profile. Disadvantages: in manual welding, the quality depends directly on the qualifications of the worker, deformation of the surface of the parts during heating, low reliability under vibration and shock.
- Soldering. No deformation of the surfaces of the parts, high accuracy, the possibility of desoldering. Disadvantages: a complex process of preparing the grounds, a minimum clearance should be ensured.
- Glue. Low cost, there is no weakening of the working section, the possibility of combined use with other types of fasteners, the tightness of the joint, increases the anti-corrosion properties of the seam, resistance to water, chemicals, temperature extremes, prostate coating technology. Disadvantages: thorough preparation of the base, strength selection may decrease if the composition is incorrectly selected.
- Riveted. The ability to apply to materials that are not amenable to welding, reliability, prevents the appearance of fatigue cracks. Disadvantages: laboriousness, material consumption, during the process there is a deformation of the surfaces of the parts due to mechanical stress.
- Interference fit. The design is quite simple, good arrangement of parts relative to each other, withstands heavy loads. Disadvantages: difficult assembly, strength dissipates under the influence of vibrations and vibrations.
As you can see, each species has its advantages and disadvantages. Given these factors, select the optimal types of fasteners in each case. Consider where various compounds are used.
Types of connections. Application examples
Threaded, adhesive, welded joints are found everywhere in any industry. For example, construction, furniture, in heavy industry and so on. Key and slotted fixings are widely used in power tools, equipment, and mechanical engineering. Tight joints are installed on the shafts of the gear rings, worm wheels. Soldering is often used in electronic systems where maximum precision is required. Riveting is used for stitching sheets of thin metal. However, as shown in the last photo, using rivets you can fasten a fairly large channel. This is just an insignificant list of the use of individual mounting options.
We can say that with technological progress, clutch technology is developing rapidly, and this means that new types of part connections will appear. The modern world is filled with aggregates, machines and mechanisms. The quality and service life of the units 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 you observe them, then the number of emergency situations at enterprises will be reduced by several times, and the units themselves will last a very long time.
So, we found out what types of joining parts exist.