Working stroke called the completed part of a technological transition, consisting of a single movement of the tool relative to the workpiece, accompanied by a change in the shape, size, surface quality and properties of the workpiece. The working stroke usually accompanies the continuous processing of one layer of the workpiece, for example, on a lathe - processing a shaft per pass, on a planer - one movement of the cutter during cutting.
Rice. 3. Processing the workpiece in three working strokes
With an auxiliary move called the completed part of the technological transition, consisting of a single movement of the tool relative to the workpiece, necessary to prepare the working stroke. For example, when rough turning a shaft, the cutter returns to its original position, making an auxiliary stroke.
2.2.6. Reception. Reception They call a complete set of human actions used when performing a technological transition or part of it and united by one purpose. Typically, the technique is an auxiliary action of the operator when operating the machine (manually), measuring the workpiece. Reception element- pressing a button, moving a handle, etc.
2.3. Workplace. A workplace is an elementary unit of the enterprise structure where the performers of the work, serviced technological equipment, part of the conveyor, and, for a limited time, equipment and objects of labor are located. Workplace - a section of the production area, equipped in accordance with the work performed on it (Fig. 1.9)
Rice. 1.9. Workplace diagrams for machine operator (a) and assembler (b):
Basic elements of workplace equipment :
Type of equipment Equipment elements
Basic technological
equipment: machines, machines, units, automatic lines, etc.
Auxiliary equipment: assembly, test stands, conveyors and other means of transporting products, etc.
Technological equipment: devices and tools (cutting, measuring, auxiliary)
Organizational equipment: means for placing and storing fixtures, tools, auxiliary materials and documentation; industrial containers for blanks and finished products; signaling and communication equipment, equipment and workplace care
When organizing the machine operator’s workplace, you should follow the instructions for operating equipment, safety precautions, sanitary standards, etc. The space occupied by the workplace is usually determined by calculation. This space must be sufficient to allow workers to make all the necessary movements and movements when performing production operations. It is also necessary alarm and communication system , ensuring the exchange of information between the worker and the foreman, as well as intra-shop maintenance services
Important characteristics of the technological process and operation are the cycle, technological operation, tact and rhythm of release.
Cycle, beat and rhythm of release
Cycle technological operation is the calendar time interval from the beginning to the end of a periodically repeating technological operation, regardless of the number of simultaneously manufactured products.
Tact refers to the time interval through which products or blanks of certain names, standard sizes and designs are periodically produced.
Rhythm release refers to the number of products or blanks of certain names, sizes and designs produced per unit of time.
It is desirable that the time spent on one operation be equal to the release takt time or a multiple of it. Such adjustment of the time spent on an operation is achieved by varying degrees of concentration of operations, the use of optimal processing modes, reducing auxiliary time due to multi-place devices, automation of loading, transportation, the use of more high-performance equipment, parallel work on the same type of backup machines, etc.
Self-test questions
1. Define a technological operation.
2. What is the reason for the division of the technological process into operations?
3. What is meant by a technological route?
4. Explain the structure of the technological operation.
5. What is meant by the principle of constructing a technological process
Technological operation is a completed part of a technological process performed at one workplace. Operation is the main element of production planning and accounting.
This part of the process is performed:
– over a specific workpiece;
– one or a group of workers;
– continuously;
- at one workplace.
The operation can be performed on separate technological equipment (machine) in conventional production or on an automatic line, which is a complex of technological equipment. Such equipment is connected by a unified transport system with technological equipment and a unified management and control system.
Main elements of the technological operation:
1. Installation is a part of a technological operation that is performed with constant fastening of processed workpieces or assembled assembly units.
2. Position - a fixed position occupied by a permanently fixed workpiece or assembled assembly unit together with a device relative to a tool or a stationary piece of equipment to perform a certain part of the operation.
3. Technological transition– a completed part of a technological operation, performed by the same means of technological equipment under constant technological conditions and installation.
4. Working stroke – a completed part of the technological transition, consisting of a single movement of the tool relative to the workpiece, accompanied by a change in the shape, size, quality and properties of the processed surface.
5. Auxiliary transition– a completed part of a technological operation, consisting of human and (or) equipment actions that are not accompanied by a change in the shape, size, quality and properties of the processed surfaces, but are necessary to complete the technological transition.
6. Auxiliary move– a completed part of a technological transition, consisting of a single movement of the tool relative to the workpiece, which is not accompanied by a change in the shape, size, quality and surface properties of the workpiece, and the working stroke necessary to perform.
7. Setup – preparation of technological equipment and accessories for performing a technological operation. Adjustment includes installation of the fixture on the machine, alignment to the size of the cutting tool, etc.
8. Adjustment – additional adjustment of technological equipment or technological equipment when performing a technological operation to restore the parameters achieved during adjustment.
9. Technological equipment– these are means of technological equipment in which, in order to perform a certain part of the technological process, materials or workpieces, means of influencing them, as well as technological equipment are placed.
10. Technological equipment– means of technological equipment that complement technological equipment for performing a certain part of the technological process.
The internal combustion engine is still the most popular invention. It is designed to power a wide variety of mechanisms. This invention revolves around quite serious terminology, which is not clear to all drivers. Today you will learn what engine stroke (piston stroke) is and.
ICE piston stroke
To know what it is, you need to understand. The power stroke is the movement of the piston during which the motor performs a useful task, namely, converts thermal energy into torque.
To begin with, let's analyze all the cycles of the engine and get to the point where the piston does this most useful work. The first step is the intake stroke. At this time, the piston moves down and the valve that allows the air-fuel mixture to enter opens. It is supplied in a certain ratio and completely fills the combustion chamber. This continues until the piston reaches bottom dead center.
As soon as the piston goes up, the valves are closed, at which point the mixture is compressed and the pressure inside the chamber increases. As soon as the piston reaches top dead center, the piston stroke begins. A spark will appear at the spark plug electrodes, which will ignite the mixture and cause a small explosion that will force the piston down. As long as the piston is directed to the lowest point of the cylinder, this segment will be considered its working stroke. Then the entire cycle is repeated due to the inertia of the crankshaft.
It is worth noting that the power stroke is the main indicator of the engine’s operating efficiency, which means we completely determine its efficiency.
At this time, all the rest of the work spent on inertia: compression of the mixture and its supply - all this creates an extra load on the crankshaft, however, without this, engine operation is impossible. Many car mechanics increase the piston stroke and increase the cylinder volume in order to achieve the greatest efficiency by increasing the stroke and volume of the mixture to be burned.
Video - Idle and other engine modes
What is engine idling?
Idling of any internal combustion engine is an operating mode in which the required mechanism is absent. This mode is typical not only for internal combustion engines, it is also actively used for many other types of power plants, but it has become more widespread in these types of engines.
This mode is ensured by the clutch, which can “break” the transmission of torque from the flywheel to the input shaft, as well as the neutral position of the gearbox handle, in which there is no transmission of torque to the drive or driveshaft.
Running the engine at idle allows you to maintain its speed at the required level without stopping. The fact is that when there is a load on the crankshaft, the internal combustion engine always tends to stop, so oxygen in this case is consumed in small quantities. This mode also allows you to warm up the engine, and on injection engines it creates work in which the content of harmful substances in the exhaust smoke is minimized.
There are a large number of “legends” surrounding the idle mode. For example, many drivers consider idling to be the most economical mode. However, this is not the case; rather, on the contrary, idling becomes the cause of the maximum fuel consumption. The fact is that when the engine does not stop completely, the fuel supply system ensures an increase in the content of gasoline in the combustion chamber, and when the throttle is opened, the level of gasoline in the mixture decreases, as oxygen consumption increases. In this mode, the engine rather operates due to the resulting inertia after the useful stroke of the piston. It is generally accepted that the most economical mode of operation of an internal combustion engine is when the speed is at around 3000 rpm. At this moment, the throttle valve opens fully, and the fuel level in the combustion chamber is at a minimum.
The stability of the idle speed is maintained by the fuel supply system. It depends on it how the motor will operate when there is no load on the shaft and the throttle valve is closed.
That's all you need to know about the most confusing terms in internal combustion engine theory. All this applies not only to car engines, because such a motor is also installed on motorcycles, chainsaws, boats and even airplanes.
Technological transition represents a completed part of a technological operation, performed on one or more workpiece surfaces, by one or more simultaneously working tools, without changing or with automatic changes in the operating modes of the machine.
Elementary transition- part of a technological transition performed by one tool over one area of the surface of the workpiece being processed in one working stroke without changing the operating mode of the machine.
Auxiliary transition- a completed part of a technological operation, consisting of human and equipment actions that are not accompanied by a change in the shape, size and surface roughness of objects of labor, but are necessary to complete a technological transition (installation of a workpiece, changing tools, etc.).
Working stroke
Auxiliary move- a completed part of a technological transition, consisting of a single movement of the tool relative to the workpiece, not accompanied by a change in the shape, surface quality or properties of the workpiece, but necessary for preparing the working stroke.
Operation is a technological process of a system aimed at achieving a goal through a controlled transformation of the products of the operation. Depending on what level of a particular system the operation is performed, it can be classified as one of the following types:
7. Concept of working and idling speed, installation and position
Working stroke- this is a completed part of a technological transition, consisting of a single movement of the tool relative to the workpiece, accompanied by a change in the shape, size, surface quality and properties of the workpiece.
Idling- the operating mode of a device, usually a source of mechanical or electrical energy, when the load is disconnected.
Installation refers to the part of the technological operation performed with constant fastening of the workpieces being processed or the assembled assembly unit.
Position is called each fixed position occupied by a permanently fixed workpiece or assembled assembly unit together with a device relative to a tool or stationary piece of equipment to perform a certain part of the operation
8. Technology as a science and as a process
Technology is understood as a set of techniques and methods for obtaining, processing or processing raw materials, materials, semi-finished products or products carried out in the process of production. Technology (or technological processes ) are also called a certain sequence of production operations, actions that ensure the production of any product of a given quality. Accurate execution of all operations and adherence to their sequence are a guarantee of the production of products of the specified quality and in the required quantity.
Technology as a science deals with identifying physical, chemical, biological patterns in order to develop and use the most efficient and economical production processes.
There are a lot of technologies. Each sphere of human activity has its own specific technologies. But there are technologies that every person should own. This is, first of all, communication technology, housing care technology, etc. There are also a number of very common technologies that are included in the content of the work of people working in the most popular professions. These are technologies for processing wood and metal, technologies for repair and construction work in the house, etc. In classes in the academic discipline - technology - you will become familiar with the technology for processing the most common materials - wood and metal, technology for repair and construction work, elements of home culture.
9. Technological documentation. types and contents of documents.
Technological documentation refers to documents that regulate the implementation of the technological process of manufacturing parts. Technological documentation thus serves as the basis for guiding the production process.
In order for the technical process to be carried out at each workplace without delays or disruptions, it is necessary to carry out special preparatory work. Therefore, technological documentation must contain comprehensive information not only for performing the technological process itself, but also for preparing production.
The types of technological documents are established by GOST 3.1102-70, and the rules for preparing general-purpose documentation are established by GOST 3.1105-71.
The technological documentation for machining processes includes: route map, operational map, map of sketches and diagrams, specification of technological documents, technological instructions, material list, equipment sheet and other documents. Technological documents are divided into text and graphic.
Text includes instructions, descriptions and other documents containing continuous text, as well as process maps, statements and other documents where the text is divided into graphs. A route map (MK) is a document containing a description of the technological process of manufacturing a product for all operations in the technological sequence, indicating the relevant data on equipment, tooling, material, labor and other standards. Operational card (OC) - a document containing a description of the operations of the technological process of manufacturing a product with a division of operations into transitions and indicating operating modes, design standards and labor standards.
A map of sketches and diagrams (SC) is a document that contains a graphic illustration of the technological process of manufacturing a product and its individual elements, supplementing or explaining the content of the operations.
A technological instruction (TI) is a document containing a description of specific work methods, methods for controlling the technological process, rules for using equipment and devices, safety measures, as well as a description of the physical and chemical phenomena that occur during the performance of individual operations of the technological process.
A bill of materials (BM) is a document containing preliminary data for preparation of production. It is compiled for the materials used in the technological process of manufacturing the product. VM is a detailed and summary statement of material consumption rates. Equipment list (VT) is a document containing a list of special and standard devices and tools necessary to equip the technological process of manufacturing a product. This statement is compiled on the basis of process maps.
10. General classification of engineering materials
1. Structural steels and alloys.
1.1. Carbon structural steels.
1.2. Alloyed structural steels.
1.3. Construction low-carbon steels.
1.4. Reinforcing steels.
1.5. Steels for cold stamping.
1.6. Structural (machine-building) cemented (nitro-carburized) alloy steels.
1.7. Structural (machine-building) upgradeable alloy steels.
1.8. Steels with increased cutting machinability.
1.10. High-strength steels with high ductility (TRIP or PNP steels)
1.11. General purpose spring steels.
1.12. Ball bearing steels.
1.13. Wear-resistant steels.
1.14. Corrosion-resistant and heat-resistant steels and alloys.
1.15. Cryogenic steels. 1.16. Heat-resistant steels and alloys.
2. Tool steels and hard alloys.
2.1. Steels for cutting tools.
2.2. Steels for measuring instruments.
2.3. Steels for cold forming dies.
2.4. Steels for hot forming dies.
2.5. Hard alloys.
3. Steels and alloys with special physical properties.
3.1. Magnetic steels and alloys.
3.2. Metal glasses (amphora alloys).
3.3. Steels and alloys with high electrical resistance for heating elements.
3.4. Alloys with a given temperature coefficient of linear expansion.
3.5. Alloys with “shape memory” effect.
4. Refractory metals and their alloys.
11. Physical, mechanical and technological properties of materials
A technological process is usually divided into parts called operations.
Technological operation refers to a completed part of a technological process performed at one workplace. An operation covers all actions of equipment and workers on one or more jointly processed or assembled production objects. So, when processing on machines, the operation includes all the actions of the worker to control the machine, as well as automatic movements of the machine associated with the process of processing the workpiece until it is removed from the machine and proceeds to processing another workpiece.
The operation is characterized by the immutability of the workplace, technological equipment, subject of labor and performer. When one of these conditions changes, a new operation takes place.
The content of the operation is determined by many factors and, above all, factors of an organizational and economic nature. The range of work included in the operation can be quite wide. The operation may consist of processing just one surface on a separate machine. For example, milling a keyway on a vertical milling machine. The production of a complex body part on an automatic line consisting of several dozen machines and having a unified control system will also be an operation.
A technological operation is the main element of production planning and accounting. Based on the operations, the labor intensity of the process, the necessary equipment, tools, devices, and the qualifications of workers are determined. For each operation, all planning, accounting and technological documentation is drawn up.
The operations included in the technological process are performed in a certain sequence. The content, composition and sequence of operations determine process structure .
The sequence of passage of a blank part or assembly unit through the workshops and production areas of an enterprise during the technological process of manufacturing or repair is called technological route .
Distinguish intershop And in-shop technological routes.
The structure of an operation involves dividing it into its component elements - settings, positions and transitions.
To process a workpiece, it must be installed and secured in a fixture, on a machine table or other type of equipment. When assembling, the same should be done with the part to which other parts must be attached.
Installation- part of a technological operation performed with constant fastening of the workpieces being processed or the assembly unit being assembled.
Each time the workpiece is removed again and then secured on the machine, or when the workpiece is rotated at any angle to process a new surface, a new setting takes place.
Depending on the design features of the product and the content of the operation, it can be performed either from one or from several installations. In the technological documentation, installations are designated by letters A, B, IN etc. For example, when processing a shaft on a milling and centering machine, milling the ends of the shaft on both sides and aligning them is performed sequentially in one installation of the workpiece. Complete processing of the shaft workpiece on a screw-cutting lathe can be carried out only from two workpiece installations in the centers of the machine, since after processing the workpiece on one side (installation A) it must be unfastened, turned over and installed in a new position (installation B) for processing on the other side. In case of turning a workpiece without removing it from the machine, it is necessary to indicate the angle of rotation: 45 o, 60 o, etc.
An installed and secured workpiece, if necessary, can change its position on the machine relative to the tool or working parts of the machine under the influence of linear movement devices or rotary devices, taking a new position.
Position is called each individual fixed position occupied by a permanently fixed workpiece or assembled assembly unit together with a device relative to a tool or a stationary piece of equipment when performing a certain part of the operation. When processing a workpiece, for example, on a turret lathe, the position will be each new position of the turret head. When processing on multi-spindle automatic and semi-automatic machines, the invariably fixed workpiece occupies different positions relative to the machine by rotating the table, which sequentially brings the workpiece to different tools.
Technological transition– a completed part of a technological operation, performed by the same means of technological equipment under constant technological conditions and installation. The technological transition, therefore, characterizes the constancy of the tool used, the surfaces formed by processing or connected during assembly, as well as the constancy of the technological regime.
For example, technological transitions will be obtaining a hole in a workpiece by processing with a twist drill, obtaining a flat surface of a part by milling, etc. Sequential processing of the same hole in the gearbox housing with a boring cutter, countersink and reamer will consist of three technological transitions, respectively, since during processing with each tool a new surface is formed.
In the turning operation, the diagram of which is shown in Fig. 11a, two technological transitions are performed. Such transitions are called simple or elementary. A set of transitions when several tools are simultaneously involved in the work is called combined transition(Fig. 11, b). In this case, all tools operate at the same feed and rotation speed. In the case when a change occurs in successively processed surfaces with one tool with a change in cutting modes (speed when processing on hydrocopying machines or speed and feed on CNC machines) with one working stroke of the tool occurs difficult transition.
Technological transitions can be carried out sequentially (Fig. 11,a) or parallel-sequentially (Fig. 11,b).
When processing workpieces on CNC machines, several surfaces can be sequentially processed by one tool (for example, a scoring cutter) as it moves along a trajectory specified by the control program. In this case, they say that the specified set of surfaces is processed as a result of executing instrumental transition.
Examples of technological transitions in assembly processes include work related to connecting individual machine parts: giving them the required relative position, checking the achieved position and fixing it with fasteners. In this case, the installation of each fastener (for example, a screw, bolt or nut) should be considered as a separate technological transition, and the simultaneous tightening of several nuts using a multi-spindle impact wrench should be considered as a combination of technological transitions.
A technological operation, depending on the organization of the technological process, can be carried out on the basis of concentration or differentiation of technological transitions. With the concentration of transitions, the structure of the operation includes the maximum possible number of technological transitions under given conditions. This organization of the operation reduces the number of operations in the technological process. In the limiting case, the technological process can consist of only one technological operation, including all the transitions necessary for the manufacture of the part. When differentiating transitions, one strives to reduce the number of transitions included in a technological operation. The limit of differentiation is such a construction of the technological process when each operation includes only one technological transition.
A characteristic feature of technological transition in any process (except hardware) is the possibility of its isolation at a separate workplace, i.e. isolating it as an independent operation. In the case of a one-transition operation, the concept of an operation may coincide with the concept of a transition.
When organizing the processing process according to the principle of differentiation of the construction of an operation (and not a transition), the technological process is divided into one- and two-transition operations, subordinate in duration to the release cycle. If operations (for example, gear hobbing, spline milling) last beyond the exhaust cycle, then backup machines are installed. Consequently, the limit of differentiation is the release stroke.
The principle of concentration of operations is divided into the principle of parallel concentration and sequential one. In both cases, a large number of technological transitions are concentrated in one operation, but they are distributed among positions in such a way that the processing time for each operation is approximately equal to or less than the production cycle. Based on the longest time for positions, the time norm for the operation will be determined. According to the principle of sequential concentration, all transitions are performed sequentially, and the processing time is determined by the total time for all transitions.
A technological transition during cutting processing can consist of several working strokes.
Under working stroke understand the completed part of a technological transition, consisting of a single movement of the tool relative to the workpiece, accompanied by a change in the shape, size, surface quality or properties of the workpiece. The number of working strokes performed in one technological transition is selected based on ensuring optimal processing conditions, for example, reducing the cutting depth when removing significant layers of material.
An example of a working stroke on a lathe is the removal of one layer of chips continuously with a cutter, on a planing machine - removal of one layer of metal over the entire surface, on a drilling machine - drilling a hole to a given depth.
Working strokes occur in cases where the amount of allowance exceeds the possible depth of cut and it has to be removed in several working strokes.
When repeating the same work, for example, drilling four identical holes sequentially, there is one technological transition performed in 4 working strokes; if these holes are made simultaneously, then there are 4 combined working strokes and one technological transition.
The operation also includes elements associated with the implementation of auxiliary movements and necessary for the implementation of the technological process. These include auxiliary transitions and techniques.
Auxiliary transition– a completed part of a technological operation, consisting of human and (or) equipment actions that are not accompanied by a change in shape, size or surface properties, but are necessary to perform a technological transition.
Auxiliary transitions include, for example, securing a workpiece on a machine or in a fixture, changing a tool, moving a tool between positions, etc. For assembly processes, auxiliary transitions can be considered transitions for installing a base part on an assembly stand or in a fixture on a conveyor, moving parts attached to it and etc.
To perform a technological operation, auxiliary moves and techniques are also required.
Auxiliary move– a completed part of a technological transition, consisting of a single movement of the tool relative to the workpiece, necessary to prepare the working stroke.
Under reception understand the complete set of worker actions used when performing a transition or part of it and united by one purpose. For example, the auxiliary transition “install the workpiece in the fixture” consists of the following techniques: take the workpiece from the container, install it in the fixture, secure it.
Auxiliary moves and techniques are taken into account when studying the cost of auxiliary time to perform an operation.
Any technological process takes place over time. The calendar time interval from the beginning to the end of any periodically repeating technological operation, regardless of the number of simultaneously manufactured or repaired products, is called cycle of technological operation .
Preparation of technological equipment and technological equipment for performing a technological operation is called adjustment . Adjustments include installing the fixture, switching the speed or feed, setting the set temperature, etc. Additional adjustment of technological equipment and (or) equipment during operation to restore the parameter values achieved during adjustment is called adjustment .