Technological operation- completed part of the technological
process performed at one workstation. For surgery
the time standard is determined and the operation is thus
unit for planning the volume of work and jobs in the workshop
A technological operation is the main structural unit of a technological process. This part of the technical process associated with the processing of one or more simultaneously processed workpieces, by one or more simultaneously working workers, at one workplace and continuously.
Continuity condition operations means performing the work provided for by it without moving on to processing another product or the same product, but at a different workplace. For example, processing a stepped roller in the centers on a lathe represents one technological operation if it is performed in the following sequence: install the workpiece in the centers, grind the roller at one end, remove the workpiece, reinstall the clamp and reinstall the workpiece in the centers, grind the roller from the other end.
Work on a roller similar in content can be performed in two operations:
Fasten the clamp, place the workpiece in the center, grind one end and remove the clamp
Attach the clamp to the other end of the workpiece, install it in the centers and grind from the other end.
However, these actions will be included in different operations if the secondary installation and processing of the second end of the roller does not follow immediately after processing the first end, but with a break for processing other workpieces of the batch (i.e., first all workpieces are processed from one end, and then everything from the other). The example given shows that the composition of the operation is established not only on the basis of purely technological considerations, but also taking into account organizational expediency.
A technological operation is the basic unit of production planning and accounting. Based on the operations, the labor intensity of manufacturing products is determined and time standards and prices are established.
Technological transition
operations performed by the same means
technological equipment with constant technological
modes and installation.
Auxiliary transition - completed part of the technological
operations consisting of human and/or/ equipment actions,
which are not accompanied by changes in the properties of objects of labor, but
necessary to complete a technological transition /example -
installing a workpiece, changing tools, etc./. Auxiliary
transitions are not recorded in the process map. At
simultaneous processing of several
transition on surfaces is called combined. Often found
operations consisting of just one technological transition.
Working stroke - completed part of the technological transition,
consisting of a single movement of the tool relative to
workpiece and is accompanied by a change in shape, size, quality
surface and properties of the workpiece.
Technological transition refers to the completed part of a technological operation performed by the same means of technological equipment under constant technological conditions and installation. If a tool was changed when turning the roller, then processing the same surface of the workpiece with this tool will be a new technological transition (Fig. 1.6). But the tool change itself is an auxiliary transition.
Rice. 1.7. Sketch of turning operation
a – simple transitions;
b – difficult transition
2.2.2. Auxiliary transition refers to the completed part of a technological operation, consisting of human and (or) equipment actions that are not accompanied by a change in the properties of the object of labor, but are necessary to complete the technological transition.
Transitions can be combined in time due to the simultaneous processing of several surfaces, i.e. they can be carried out sequentially (roughing, semi-finishing, finishing turning of a stepped shaft or drilling four holes with one drill), in parallel (turning a stepped shaft with several cutters or drilling four holes at once four drills) or parallel-sequentially (after turning a stepped shaft simultaneously with several cutters, simultaneous chamfering with several chamfering cutters, or drilling four holes sequentially with two drills).
Installation
Installation- part of the technological operation performed with unchanged fastening of the workpieces being processed or the assembled assembly unit. Rotating parts to any angle is a new installation. If the roller is first turned in a three-jaw chuck with one setting, and then it is turned over and turned, then this will require two settings in one operation (Fig. 1.7).
2.2.4. Position. A workpiece installed and secured on a rotary table, subjected to drilling, reaming and countersinking, has one setting, but with the rotation of the table it will take a new position.
Position is a fixed position occupied by a rigidly 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. On multi-spindle and semi-automatic machines, the workpiece, when it is secured, occupies different positions relative to the machine. The workpiece moves to a new position together with the clamping device (Fig. 1.8).
When developing a technological process for processing workpieces, it is preferable replace settings with positions, since each additional setting introduces its own processing errors.
The product is obtained as a result of the manufacturing process.
Manufacturing process This is the totality of all the actions of people and production tools necessary at a given enterprise for the manufacture or repair of manufactured products.
The production process includes not only the main processes directly related to the manufacture of parts and assembly units, but also all necessary processes, for example: preparation of production; receipt, transportation, control and storage of materials (semi-finished products); equipment repair, etc.
Technological process(TP) is a part of the production process that contains actions to change and subsequently determine the state of the item of production.
Technological method- a set of rules that determine the sequence and content of actions when performing shaping, processing or assembly, movement, including technical control, testing in the technological process of manufacturing or repair, established without regard to the name, standard size or design of the product.
Based on the execution method, there are three main parts of the technological process: forming, processing and assembly.
When changing the position of the workpiece being processed, the operation may consist of several settings and positions.
Installation- this is part of the technological operation performed with constant fastening of the workpieces being processed or the assembly unit being assembled.
Position- this is 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 part of the operation.
Reception- a complete set of human actions used when performing a transition or part of it and united by one purpose. For example, the auxiliary transition “installing a workpiece in a fixture” includes the following techniques: take a workpiece, install it in a fixture, and secure it.
General allowance for processing is a layer of material that represents the difference between the dimensions of the workpiece and the dimensions of the final processed part.
Base surface the workpiece being processed is the surface with which the workpiece is installed in the fixture and oriented when processing on the machine relative to the cutting tool.
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.