Without a kinematic diagram, it is impossible to imagine any type of equipment. We are talking about cars, tractors, machine tools, and simpler types of mechanisms. In general, kinematics is a special department in mechanics, which is aimed at studying the properties of links in mechanisms. Science allows for kinematic analysis by studying the trajectories of movement of links, determining points, positions and speeds of elements. Achieving the final result is impossible without substantiating the concept of "kinematic scheme", which will be discussed in this article.
What is a kinematic scheme? Basic concepts
If you briefly answer this question, then the kinematic diagram is a kind of drawing or document, so to speak, which shows all the mechanical links with dimensions. Oftenthe circuit links are called kinematic pairs. If we define it in scientific language, then these are conjugated solid elements in the amount of 2 pieces, which, due to the conditions of communication, limit the movement of each other.
The presence of dimensions is necessary for conducting kinematic analysis, which studies the basics of the movement of mechanisms, their trajectories and speeds. Kinematics problems can be solved both graphically and experimentally.
In general, we talk about the kinematic scheme when we analyze the type of mechanism. They call it a certain system of bodies that transforms the movement of some for the required movement of others. The composition of any mechanical element includes links - several solid particles rigidly interconnected. A link that is considered fixed is called a rack.
An element of a kinematic pair or link is a system of surfaces and lines along which one link comes into contact with another. This point is also called the junction node.
Fields of application of kinematic schemes
The kinematic scheme is used in absolutely all areas of industry - mechanical engineering, machine tool building, etc. All execution rules are regulated by a special document - the so-called GOST.
Rules for the implementation of schemes
There are several basic laws for drawing up kinematic drawings:
- The document can be made both on paper and on electronic media. It is recommended to draw up design diagrams on one sheet with the possibility of dividing it into the required formatswhen printing.
- In the case of using complex schemes, the use of multimedia tools is allowed, that is, it is possible to show movement in dynamics in a visual way.
Kinematic drawings are divided into three types: principal, structural and functional. The rules for compiling them also differ from each other.
As for the circuit diagrams, the figure must necessarily show all kinds of connections between elements. The document is provided in the form of a scan. The principal kinematic diagram, the designations of which the developer indicates in the margins, must be depicted in the product outline in an axonometric projection. More detailed rules for their preparation can be found in GOST 2.303 and 2.701.
The main difference between block diagrams and circuit diagrams is that the first ones depict the functional parts of the product and the relationship between them. As a rule, they are presented in the form of graphic images or an analytical record.
Functional diagrams illustrate the relationship between parts of elements, which are represented by simple geometric shapes.
Who regulates the correctness of the schemes?
The rules for compiling are spelled out in interstate documents on standardization. Many countries of the world voted for the entry into force of this document many years ago. From time to time, changes are made to GOST, this is understandable - scientific progress does not stand still, science develops, and with it, regulatory documents undergo changes. Apart fromthe main standard, the rules for the implementation of kinematic diagrams are prescribed in the Unified System for Design Documentation.
Determination of the structure of mechanisms
As mentioned above, all mechanisms consist of a certain number of kinematic pairs. They are divided into several main ones:
- by type of connection - to lower and higher;
- according to the method of closing;
- for relative motion in pairs - for translational, rotational, cylindrical, etc.
Kinematic schemes of mechanisms determine their structure. If we give this concept a definition, then it is the totality of all elements of the device and the relationships between them. In addition, to determine the structure of the mechanism, you need to establish the composition of the incoming links.
Based on the above classifications, the main types of machine elements that determine its structure are distinguished:
- stand;
- rod;
- crank;
- creeper.
Types of mechanisms
There are a large number of different designs. Most often, mechanisms are divided into:
- lever or rod;
- friction;
- cam;
- mechanisms with flexible links;
- toothed and others
Among the main classifications of mechanisms, there is one that divides them into three groups:
- functional (according to the principle of the technological process);
- structural (by structure);
- structural-constructive (according to constructive principles).
More details about the kinematic diagrams will be described using the example of an electric drive.
What is a drive? Its purpose
Before talking about the kinematic scheme of the drive, you need to know what it is. The drive is a special device that drives the machine with the help of an engine. In other words, the mechanism begins to move from the flow of energy, which comes either from the engine or from additional elements. The kinematic scheme of the gearbox is indispensable when studying the concept of "drive". This device is a mechanism of worm or gear wheels that transmits rotation from the engine directly to the machine shaft. Its body is made up of bearings, shafts and gears.
Kinematic diagram of the drive
In any drive, all elements connected to each other have a certain influence on each other. That is, studying the movement of only one link will not be enough, it is important to take into account their mutual influence. To do this, all the forces in the structure are brought to a single point, usually the motor shaft. The kinematic scheme of the drive is called equivalent, and the parameters are called reduced.
The schemes of this equipment consist of such basic elements as:
- electric motor;
- open transfer;
- reducer;
- machine drive shaft;
- coupling.
This is a classic compositionkinematic diagram, some elements may be missing.
Kinetic diagram of other mechanisms
Kinematics is a science that studies various designs, therefore, for any type of equipment, the scheme has its own. Consider the drawing of the most common unit - the machine. Of course, there are a number of other mechanisms, and studying their schemes can take a lot of time. Images of complex structures are examined in more detail by scientists, mechanics and lovers of kinematics.
A machine tool is a simple example of a mechanism that is driven by certain forces. The executive bodies of the design are: table, caliper, spindle and other details. The machine kinematics chains consist of various gears, which are placed in a certain sequence. Kinematic transmission schemes may include belt, gear or worm mechanisms. In the drawing, all elements are indicated by special signs, which are prescribed in GOST 3462-61. The kinematic diagram of the machine necessarily includes the steps of the lead screws, worm entry modules, engine speed, power, etc.
Modern equipment has not only mechanical transmissions, often hydraulic or pneumatic devices are used, and, accordingly, in the passports of machine tools you can find not kinematic diagrams, but combined pneumohydraulic or electric ones.
The modern world of machines and parts is huge, there are thousands of different mechanisms and elements. However, every mechanic althe unit has its own kinematic scheme, whether it is a crane, a car suspension, a metal-cutting machine or a drilling rig. Kinematic drawings and design descriptions help to understand the structure and composition of mechanisms, facilitate the process of studying the movement of elements and links in a chain. Thanks to such schemes and the science of kinematics in general, scientific and technological progress does not stand still, more and more advanced mechanisms, machines and assemblies appear that are actively entering our lives.
