GOST 2.703-2011
Group T52
INTERSTATE STANDARD
one system design documentation
RULES FOR THE IMPLEMENTATION OF KINEMATIC SCHEMES
Unified system of design documentation. Rules for presentation of kinematic diagrams
ISS 01.100.20
OKSTU 0002
Introduction date 2012-01-01
Foreword
Foreword
The goals, basic principles and basic procedure for carrying out work on interstate standardization are established in GOST 1.0-2015 "Interstate standardization system. Basic provisions" and GOST 1.2-2015 "Interstate standardization system. Interstate standards, rules and recommendations for interstate standardization. Rules for the development, adoption , updates and cancellations"
About the standard
1 DEVELOPED by the Federal State Unitary Enterprise "All-Russian Scientific Research Institute for Standardization and Certification in Mechanical Engineering" (FSUE "VNIINMASH"), Autonomous Non-Profit Organization "Research Center for CALS-Technologies "Applied Logistics"" (ANO NRC CALS-Technologies "Applied Logistics" ")
2 INTRODUCED by the Federal Agency for Technical Regulation and Metrology
3 ADOPTED by the Interstate Council for Standardization, Metrology and Certification (Minutes of May 12, 2011 N 39)
Voted to accept:
Short name of the country according to MK (ISO 3166) 004-97 | Abbreviated name of the national standards body |
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Azerbaijan | Azstandard |
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Ministry of Economy of the Republic of Armenia |
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Belarus | State Standard of the Republic of Belarus |
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Kazakhstan | State Standard of the Republic of Kazakhstan |
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Kyrgyzstan | Kyrgyzstandart |
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Moldova-Standard |
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Rosstandart |
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Tajikistan | Tajikstandart |
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Uzbekistan | Uzstandard |
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Gospotrebstandart of Ukraine |
4 By order of the Federal Agency for Technical Regulation and Metrology dated August 3, 2011 N 211-st, the interstate standard GOST 2.703-2011 was put into effect as the national standard of the Russian Federation from January 1, 2012.
5 INSTEAD OF GOST 2.703-68
6 REVISION. December 2018
Information about changes to this standard is published in the annual information index "National Standards", and the text of changes and amendments - in the monthly information index "National Standards". In case of revision (replacement) or cancellation of this standard, a corresponding notice will be published in the monthly information index "National Standards". Relevant information, notification and texts are also posted in the public information system - on the official website of the Federal Agency for Technical Regulation and Metrology on the Internet (www.gost.ru)
1 area of use
This standard establishes the rules for the implementation of kinematic diagrams of products in all industries.
Based on this standard, it is allowed, if necessary, to develop standards that establish the implementation of kinematic schemes for products of specific types of equipment, taking into account their specifics.
2 Normative references
This standard uses normative references to the following interstate standards:
GOST 2.051-2013 Unified system for design documentation. Electronic Documents. General provisions
GOST 2.303-68 Unified system for design documentation. lines
GOST 2.701-2008 Unified system for design documentation. Scheme. Types and types. General performance requirements
Note - When using this standard, it is advisable to check the validity of reference standards in the public information system - on the official website of the Federal Agency for Technical Regulation and Metrology on the Internet or according to the annually published information index "National Standards", which was published as of January 1 of the current year , and according to the corresponding monthly published information signs published in the current year. If the reference standard is replaced (modified), then when using this standard, you should be guided by the replacing (modified) standard. If the referenced standard is canceled without replacement, the provision in which the reference to it is given applies to the extent that this reference is not affected.
3 General
3.1 Kinematic diagram - a document containing in the form of conventional images or symbols mechanical components and their relationships.
Kinematic diagrams are performed in accordance with the requirements of this standard and GOST 2.701.
3.2 Kinematic diagrams can be made as a paper and (or) electronic design document.
Schemes in the form of an electronic design document are recommended to be single-sheeted, ensuring that this sheet is divided into the required formats when printed.
Note - If the kinematic diagram is performed as an electronic design document, GOST 2.051 should be additionally followed.
3.3 Complex diagrams for the most visual representation can be made dynamic (using multimedia tools).
3.4 Kinematic schemes, depending on the main purpose, are divided into the following types:
- fundamental;
- structural;
- functional.
4 Rules for the execution of schemes
4.1 Rules for the execution of circuit diagrams
4.1.1 The concept diagram of the product must present the entire set of kinematic elements and their connections intended for the implementation, regulation, control and monitoring of the specified movements of the executive bodies; kinematic connections (mechanical and non-mechanical) provided inside the executive bodies, between individual pairs, chains and groups, as well as connections with the source of movement, should be reflected.
4.1.2 The schematic diagram of the product is depicted, as a rule, in the form of a sweep (see Appendix A).
It is allowed to enter schematic diagrams into the contour of the product image, as well as depict them in axonometric projections.
4.1.3 All elements in the diagram are depicted by conventional graphic symbols (UGO) or simplified in the form of contour outlines.
Note - If the UGO is not established by the standards, then the developer performs the UGO on the margins of the diagram and gives explanations.
4.1.4 Mechanisms, separately assembled and independently regulated, are allowed to be depicted on the schematic diagram of the product without internal connections.
The diagram of each such mechanism is depicted as a remote element on the general schematic diagram of the product, which includes the mechanism, or is performed as a separate document, while a link to this document is placed on the product diagram.
4.1.5 If the product includes several identical mechanisms, it is allowed to carry out a schematic diagram for one of them in accordance with the requirements of Section 6, and to depict other mechanisms in a simplified manner.
4.1.6 The relative position of the elements on the kinematic diagram must correspond to the initial, average or working position of the executive bodies of the product (mechanism).
It is allowed to explain with an inscription the position of the executive bodies for which the scheme is made.
If the element changes its position during the operation of the product, then it is allowed to show its extreme positions in the diagram with thin dash-dotted lines.
4.1.7 On the kinematic diagram, without violating the clarity of the diagram, it is allowed:
- move the elements up or down from their true position, take them out of the product contour without changing the position;
- rotate elements to the most convenient positions for the image.
In these cases, the conjugated links of the pair, drawn separately, are connected by a dashed line.
4.1.8 If the shafts or axes intersect when depicted on the diagram, then the lines depicting them do not break at the intersections.
If in the diagram the shafts or axles are covered by other elements or parts of the mechanism, then they are depicted as invisible.
It is allowed to conditionally rotate the shafts as shown in Figure 1.
Picture 1
4.1.9 The ratio of the sizes of the symbols of the interacting elements in the diagram should approximately correspond to the actual ratio of the sizes of these elements in the product.
4.1.10 On the schematic diagrams, they are depicted in accordance with GOST 2.303:
- shafts, axles, rods, connecting rods, cranks, etc. - solid main lines with a thickness of ;
- elements shown in simplified form as contour outlines, gears, worms, sprockets, pulleys, cams, etc. - solid lines with thickness ;
- the contour of the product, in which the scheme is inscribed, - by solid thin lines with a thickness of ;
- lines of interconnection between the conjugated links of the pair, drawn separately, by dashed lines with a thickness of ;
- lines of interconnection between elements or between them and the source of motion through non-mechanical (energetic) sections - by double dashed lines with a thickness of ;
- calculated relationships between elements - triple dashed lines with a thickness of .
4.1.11 On the schematic diagram of the product indicate:
- the name of each kinematic group of elements, taking into account its main functional purpose (for example, feed drive), which is applied on the shelf of the leader line drawn from the corresponding group;
- the main characteristics and parameters of the kinematic elements that determine the executive movements of the working bodies of the product or its components.
An approximate list of the main characteristics and parameters of the kinematic elements is given in Appendix B.
4.1.12 If the circuit diagram of the product contains elements whose parameters are specified during adjustment by selection, then these parameters are indicated on the diagram based on the calculated data and the inscription is made: "Parameters are selected during regulation."
4.1.13 If the circuit diagram contains reference, dividing and other precise mechanisms and pairs, then the diagram indicates data on their kinematic accuracy: the degree of transmission accuracy, the values of permissible relative displacements, turns, the values of permissible backlashes between the main driving and actuating elements, etc. .d.
4.1.14 On the circuit diagram it is allowed to indicate:
- limiting values of the number of revolutions of the shafts of kinematic chains;
- reference and calculated data (in the form of graphs, diagrams, tables), representing the sequence of processes over time and explaining the relationship between individual elements.
4.1.15 If the circuit diagram is used for dynamic analysis, then it indicates the required dimensions and characteristics of the elements, as well as the largest values of the loads of the main leading elements.
Such a diagram shows the supports of the shafts and axles, taking into account their functional purpose.
In other cases, shaft and axle supports may be depicted by general conventional graphic symbols.
4.1.16 Each kinematic element shown in the diagram, as a rule, is assigned a serial number, starting from the source of movement, or alphanumeric reference designations (see Appendix B). Shafts are allowed to be numbered with Roman numerals, other elements are numbered only with Arabic numerals.
Elements of purchased or borrowed mechanisms (for example, gearboxes, variators) are not numbered, but a serial number is assigned to the entire mechanism as a whole.
The serial number of the element is put down on the shelf of the leader line. Under the shelf, leader lines indicate the main characteristics and parameters of the kinematic element.
Characteristics and parameters of kinematic elements are allowed to be placed in the list of elements, drawn up in the form of a table in accordance with GOST 2.701.
4.1.17 Replaceable kinematic elements of setting groups are indicated on the diagram by lowercase letters of the Latin alphabet and the characteristics for the entire set of replaceable elements are indicated in the table. Such elements are not assigned serial numbers.
It is allowed to perform the characteristics table on separate sheets.
4.2 Rules for the execution of block diagrams
4.2.1 The block diagram depicts all the main functional parts of the product (elements, devices) and the main relationships between them.
4.2.2 Structural diagrams of the product are either a graphical representation using simple geometric shapes, or an analytical record that allows the use of an electronic computer.
4.2.3 The block diagram should indicate the names of each functional part of the product, if a simple geometric figure is used to designate it. In this case, the names, as a rule, are entered inside this figure.
4.3 Rules for the execution of functional diagrams
4.3.1 The functional diagram depicts the functional parts of the product involved in the process illustrated by the diagram, and the relationships between these parts.
4.3.2 Functional parts are depicted with simple geometric figures.
To convey more complete information about the functional part inside geometric figure it is allowed to place the appropriate designations or an inscription.
4.3.3 The functional diagram should indicate the names of all depicted functional parts.
4.3.4 For the most visual representation of the processes illustrated by the functional diagram, the designations of the functional parts should be placed in the sequence of their functional relationship.
It is allowed, if this does not violate the visibility of the process representation, to take into account the actual location of the functional parts.
Annex A (informative). An example of the implementation of the principal kinematic diagram
Annex A
(reference)
Appendix B (informative). An approximate list of the main characteristics and parameters of kinematic elements
Annex B
(reference)
Table B.1
Name | The data indicated on the diagram |
1 Movement source (engine) | Name, type, characteristic |
2 Mechanism, kinematic group | Characteristics of the main executive movements, range of regulation, etc. Gear ratios of the main elements. Dimensions that determine the limits of movement: the length of movement or the angle of rotation of the executive body. The direction of rotation or movement of elements, on which the receipt of specified executive movements and their consistency depend. It is allowed to place inscriptions indicating the modes of operation of the product or mechanism, which correspond to the indicated directions of movement. Note - For groups and mechanisms shown in the diagram conditionally, without internal connections, the gear ratios and characteristics of the main movements are indicated. |
3 Reading device | Limit of measurement or scale division |
4 Kinematic links: | |
a) belt pulleys | Diameter (for replacement pulleys - the ratio of the diameters of the driving pulleys to the diameters of the driven pulleys) |
b) gear wheel | Number of teeth (for gear sectors - the number of teeth on a full circle and the actual number of teeth), module, for helical gears - the direction and angle of inclination of the teeth |
c) gear rack | Module, for helical racks - direction and angle of inclination of the teeth |
d) worm | Axial module, number of starts, type of worm (if it is not Archimedean), direction of the coil and diameter of the worm |
e) lead screw | The course of the helix, the number of visits, the inscription "lion." - for left-hand threads |
e) chain sprocket | Number of teeth, chain pitch |
g) cam | Parameters of curves that determine the speed and limits of movement of the leash (pusher) |
Annex B (recommended). Letter codes of the most common groups of elements
Table B.1
Letter code | Group of mechanism elements | Element example |
Mechanism (general designation) | ||
Elements of cam mechanisms | Cam, pusher |
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Miscellaneous elements | ||
Elements of mechanisms with flexible links | Belt, chain |
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Elements of lever mechanisms | Rocker, crank, rocker, connecting rod |
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Movement source | Engine |
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Elements of Maltese and ratchet mechanisms | ||
Elements of gear and friction mechanisms | Gear wheel, gear rack toothed sector, worm |
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Clutches, brakes |
UDC 62:006.354 | ISS 01.100.20 | ||
Keywords: design documentation, kinematic diagram, circuit diagram, block diagram, functional diagram |
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Electronic text of the document
prepared by Kodeks JSC and verified against:
official publication
Moscow: Standartinform, 2019
Designers who develop various machines and mechanisms often perform kinematic diagrams . At the same time, they are guided by the norms and requirements set forth in such a fundamental document as GOST 2.770–68.
| Designation | Name |
| Shaft, axle, rod, etc. | |
| Radial plain and rolling bearings on the shaft | |
| Thrust plain and rolling bearings on the shaft | |
| Plain bearings, radial | |
| Rolling bearings, radial | |
| Angular contact rolling bearings | |
| Coupling | |
| Coupling elastic | |
| Clutch (managed) | |
| Brake | |
| Flywheel on the shaft | |
 |
Ratchet gear mechanism with external gearing |
 |
belt transmission |
 |
chain transmission |
 |
Cylindrical compression springs |
 |
Tension springs, cylindrical |
 |
Spur gears with external gearing |
 |
Gear gears cylindrical with internal gearing |
 |
Bevel gears with intersecting shafts |
 |
Gears with cylindrical worm |
 |
Rack and pinion gears |
| Drum cams, cylindrical | |
| Rotating cams |
In engineering, a diagram means graphic image, which shows the component parts of the product, their design features, as well as the relationships existing between them using simplified symbols and symbols. As part of the design documentation packages, diagrams play a rather important role. They are present in general descriptions products, instructions for their installation, commissioning and operation. Schematic drawings provide invaluable assistance to personnel involved in the installation, commissioning, repair of machines, mechanisms and individual units. Diagrams allow you to quickly understand what are functional connections exist between mechanical, hydraulic, electrical and other links and systems of technical devices.
When the development of a machine is just beginning, the designers draw a general sketch of the future product by hand, that is, they make up its initial scheme. It conditionally displays all the main nodes, and also shows the relationship between them. Only after the schematic diagram of the device has been worked out, the development of drawings and other design documentation begins.
In modern mechanical engineering, the greatest application is found by those machines in which the transmission of motion is based on mechanical, hydraulic or electrical principle functioning.
Kinematic schemespurpose kinematic schemes is a reflection of the connection in which the working mechanism and the drive consist. It should be noted that in modern cars, machine tools and other technological equipment, mechanical transmissions are very complex and contain many elements. Therefore, in order to correctly create diagrams of such structures, you need to know perfectly well all the conventions that are used to graphically depict the principle of operation of a machine or mechanism without specifying their design features. For example, the kinematic diagrams of machine tools reflect exactly how the rotational movement of the motor shaft is communicated to the spindle, and the contour of the machine is shown (or not shown) with a thin line.
If non-standardized symbols are used on the diagrams, then they require explanation. As for the external outlines and schematic sections, they are depicted in the diagrams in a simplified way, in accordance with what kind of design each element of the product has.
On schematic images, leader lines are drawn from each of their component parts. From solid lines they start with arrows, and from planes - with dots. On the shelves of leader lines, the serial numbers of positions are indicated. At the same time, Roman numerals are used for elements such as shafts, and Arabic numerals for the rest. Under the shelves of leader lines, the parameters and main characteristics of the components of the circuits are indicated.
| Name | Designation | Name | Designation | |
| Shaft | Gears: | |||
| Connection of two shafts: | cylindrical wheels | |||
| deaf | ||||
| blind with overload protection | bevel wheels | |||
| elastic | ||||
| articulated | screw wheels | |||
| telescopic | ||||
| floating clutch | worm | |||
| gear clutch | ||||
| Shaft connection: | ||||
| free to rotate | rack | |||
| movable without rotation |  | |||
| with pull-out pin | Lead screw transmission with nut: | |||
| deaf | one-piece | |||
| Plain bearings: | detachable | |||
| radial | Couplings: | |||
| cam one-sided | ||||
| cam double-sided | ||||
| Rolling bearings: | conical one-sided | |||
| radial | ||||
| angular contact one-sided | disk one-sided | |||
| double-ended angular contact | disc double-sided | |||
| Belt drives: | electromagnetic unilateral | |||
| flat belt | ||||
| electromagnetic double-sided | ||||
| overrunning unilateral | ||||
| V-belt | ||||
| overrunning double-sided |  | |||
| Brakes: | ||||
| conical | ||||
| chain transmission |  | |||
| shoe | ||||
| disk |
with wheel z6 it is necessary that the block freely passes by the wheel z8 without hitting it with a wheel z9. This is possible if z7 – z9 > 5. Otherwise, it is necessary to apply the transmission scheme shown in Fig. 2.15, b. On fig. 2.15, V brute force transmission is shown. Shaft I can receive rotation from the wheel z5 when turning on the cam clutch of the wheels z1 And z4. With the clutch disengaged and the wheel engaged z4 With z3 rotation on the shaft I is transmitted through gears z1/z2, shaft II and wheels z3/z4 .
Rice. 2.15. Gear box mechanisms: A─ with two
mobile blocks; b─ with a three-crown block;
V─ with enumeration; G─ with friction double-sided clutch
Transmissions with sliding blocks and dog clutches are simple in design, reliable in operation and easy to control, but do not allow switching during rotation and have big sizes in the axial direction. On fig. 2.15, G a transmission is given that is devoid of these shortcomings. wheels z2 And z4 freely mounted on the shaft II and are constantly engaged with the wheels z1 And z3, rigidly fixed on the shaft I. The transfer of motion to the shaft II from the shaft I occurs when the friction double-sided clutch is turned on, which rigidly connects the wheels to the shaft II z2 And z4. In this case, the speed can be changed on the go.
In modern machine tools with automatic gearboxes, one and two-way friction electromagnetic clutches are used.
On fig. 2.16, A shows the mechanism of the meander with a captive wheel z0, which allows you to double the gear ratios when you turn on the adjacent pair of gears. If we accept shaft I as the leading one, and shaft II as the driven ones, and z \u003d z 2 \u003d z 3 \u003d z 6= 56, and z 1 = z 4 = z 5 = z 7= 28, then we get the gear ratios of the mechanism:
Rice. 2.16. Mechanisms meander feed boxes:
a ─ with a captive wheel; b ─ with a movable wheel
The meander mechanism is also called the “multiplying mechanism”. The cap wheel mechanism has the disadvantage that it does not provide a constant center distance between the cap wheel z0 And z2, since the swivel lever 2 is fixed with a non-rigid movable cylindrical latch 1.
On fig. 2.16 b a more perfect design of the meander mechanism is shown, from which the cap wheel with a swivel lever is excluded.
The connection with the wheels of the blocks is made by a movable wheel z, which ensures the constancy of the center distances.
Norton's mechanism (Fig. 2. 17) is a cone made of gears with a cap wheel mounted on a rotary lever with a cylindrical lock. Cap wheel z0 can alternately engage with all the wheels of the cone ( z1 – z6) and transfer motion from shaft I to shaft II. Thus, six different gear ratios can be obtained. The choice of the number of teeth of the cone wheels is not related to the constancy of the center distance between the driving and driven shafts. The advantage of this mechanism is compactness, the disadvantage is low rigidity. The main purpose of this mechanism is to create an arithmetic series of gear ratios. Mainly used in universal screw-cutting lathes.
Shown in fig. 2.15, A The scheme of a six-speed gear box is a conventional multiplier structure, consisting of one kinematic chain with a series connection of movable blocks (gear groups), and provides a geometric series of circular output shaft speeds. This structure allows you to successfully create rational drives of the main movement. However, in some cases, for example, in universal screw-cutting lathes, with an increase in the range of speed control, it is impossible to create a simple drive that meets the requirements on the basis of such a structure. Therefore, in the machine tool industry, so-called folded structures are used. Folded is the structure of a multi-speed stepped drive, consisting of two, less often three kinematic chains, each of which is a conventional multiplier structure. One of these circuits (short) is for higher drive speeds, the others (longer) for low speeds. As an example, in fig. 2.18 shows a diagram of a gear box for 12 spindle speeds (output shaft), which has a folded
Continuation of the table. 3.1
Continuation of the table. 3.1
The end of the table. 3.1
Among the transmissions of motion from the drive to the working bodies of the machine, mechanical transmissions are most widely used (Fig. 3.1).
According to the method of transferring motion from the driving element to the driven element, mechanical transmissions are divided as follows: gears with direct contact (gear - Fig. 3.1, a; worm - Fig. 3.1, b; ratchet; cam) or with a flexible connection (chain); friction transmissions with direct contact (friction) or with a flexible connection (belt - Fig. 3.1, c).
The main kinematic parameter that characterizes all types of mechanical transmissions of rotational motion is the gear ratio - the ratio of the number of teeth of a larger wheel to the number of teeth of a smaller one in a gear, the number of teeth of a wheel to the number of worm entries in a worm gear, the number of teeth of a large sprocket to the number of teeth of a small one in a chain transmission, as well as the diameter of a large pulley or roller to the smaller diameter in a belt or friction drive. The gear ratio characterizes the change in speed in the transmission
where and - the speed of rotation of the driving I and driven shafts II, min -1 or s -1 (see Fig. 3.1, a, b and c).
So, for gear (see Fig. 3.1, A) and chain drives
where is the number of teeth of the larger gear or sprocket; - the number of teeth of the smaller gear or sprocket.
For worm gear (see fig. 3.1, b)
where is the number of teeth of the worm wheel; - the number of visits of the worm.
For belt drive (Fig. 3.1, c)
where is the diameter of the driven (larger) transmission pulley, mm; - diameter of the driving (smaller) transmission pulley, mm.
To convert rotational motion into translational or vice versa, rack and pinion are used (Fig. 3.1, G) or screw (Fig. 3.1, e) transmission. In the first case, the axis of rotational motion and the direction of translational motion are perpendicular, and in the second, they are parallel.
Gears that convert rotational motion into translational motion are characterized by the distance that the moving element translates in one revolution of the drive shaft.
In a rack and pinion (see Fig. 3.1, d), the rack moves in one revolution of the gear (gear)
where is the number of teeth of the wheel; - engagement module.
Rice. 3.1. Gears in machine tools: a - gear: I - drive shaft; - number of gear teeth; - frequency of rotation of the drive shaft; II - driven shaft; - number of teeth of the wheel; - frequency of rotation of the driven shaft; b - worm: and - rotational speed and number of worm entries, respectively; and - frequency of rotation and the number of teeth of the wheel, respectively; c - belt: and - frequency of rotation of the drive roller and its diameter, respectively; and - frequency of rotation of the driven roller and its diameter, respectively; g - screw: - screw pitch; - the direction of movement of the nut; d - rack: - direction of movement of the rail; - rack teeth pitch; - number of teeth of the wheel; - wheel rotation direction
A screw-nut pair is used in the feed mechanisms of almost all machine tools. Turning the screw one turn moves the nut to the right or left (depending on the thread direction) one step. There are designs in which the nut is fixed and the screw rotates and moves, as well as designs with a rotating and moving nut. For screw-nut transmission, the translational movement of the moving element
where - screw pitch, mm; - number of screw starts.
When several gears are arranged in series, their total gear ratio is equal to the product of the gear ratios of the individual gears
where is the total gear ratio of the kinematic chain; - gear ratios of all elements of the kinematic chain.
The speed of the last driven shaft of the kinematic chain is equal to the speed of the drive shaft, divided by the total gear ratio,
Travel speed (mm/min) of the finite element (node) of the kinematic chain
where is the frequency of rotation of the drive shaft of the initial element; - displacement of a translationally moving element per revolution of the drive shaft, mm.
The mathematical expression of the connection between the movements of the leading and driven elements (initial and final links) of the kinematic chain of the machine is called the kinematic balance equation. It includes components that characterize all elements of the chain from the initial to the final link, including those that transform movement, for example, rotational into translational. In this case, the balance equation includes the unit of measurement of the parameter (lead screw pitch - when using the screw-nut transmission or module - when using the gear-rack transmission), which determines the conditions for this transformation, millimeter. This parameter also allows you to coordinate the characteristics of the movement of the initial and final links of the kinematic chain. When transmitting only rotational motion, the equation includes dimensionless components (gear ratios of mechanisms and individual gears), and therefore the units of measurement of the motion parameters of the final and initial links are the same.
For machines with the main rotational movement, the limiting values of the spindle speed and provide the processing of a workpiece with a diameter of the machined surfaces in the range from to.
The spindle speed control range characterizes the operational capabilities of the machine and is determined by the ratio of the highest speed of the machine spindle to the lowest:
The rotational speed values from to form a series. In the machine tool industry, as a rule, a geometric series is used in which adjacent values differ by a factor of (- the denominator of the series: ). The following values of the denominator 1.06 are accepted and normalized; 1.12; 1.26; 1.41; 1.58; 1.78; 2.00. These values form the basis of the table series of spindle speeds.
3.2. Typical parts and mechanisms of machine tools
Beds and guides. The carrier system of the machine is formed by a set of its elements, through which the forces that arise between the tool and the workpiece during the cutting process are closed. The main elements of the carrier system of the machine are the frame and body parts (crossbars, trunks, sliders, plates, tables, calipers, etc.).
Bed 1 (Fig. 3.2) serves for mounting parts and assemblies of the machine, moving parts and assemblies are oriented and moved relative to it. The bed, as well as other elements of the carrier system, must have stable properties and ensure the possibility of processing workpieces with specified modes and accuracy during the service life of the machine. This is achieved by the correct choice of the material of the frame and the technology of its manufacture, wear resistance of the guides.
Rice. 3.2. Machine beds: a - screw-cutting lathe; b - lathe with program control; in - surface grinding; 1 - bed, 2 - guides.
For the manufacture of frames, the following basic materials are used: for cast frames - cast iron; for welded - steel, for the beds of heavy machine tools - reinforced concrete (sometimes), for high-precision machines - an artificial synthetic material made from crumbs of mineral materials and resin and characterized by slight temperature deformations.
Guides 2 provide the required relative position and the possibility of relative movement of the nodes that carry the tool and the workpiece. The rail design for moving the assembly allows only one degree of freedom of movement.
Depending on the purpose and design, there is the following classification of guides:
By type of movement - main movement and feed movement; guides for rearranging mating and auxiliary units that are stationary during processing;
Along the trajectory of movement - rectilinear and circular motion;
In the direction of the trajectory of the movement of the node in space - horizontal, vertical and inclined;
By geometric shape - prismatic, flat, cylindrical, conical (only for circular motion) and their combinations.
Rice. 3.3. Examples of sliding guides: a - flat; 6 - prismatic; in - in the form of a "dovetail"
Sliding guides and rolling guides are the most widely used (in the latter, balls or rollers are used as intermediate rolling bodies).
For the manufacture of sliding guides (Fig. 3.3) (when the guides are made as one piece with the frame), gray cast iron is used. Wear resistance of guides is increased by surface hardening, hardness HRC 42…56.
Steel guides are made overhead, usually hardened, with hardness HRC 58…63. Most often, steel 40X is used with HDTV hardening 1, steels 15X and 20X are followed by carburizing and hardening.
Reliable operation of the guides depends on protective devices that protect the working surfaces from dust, chips, dirt on them (Fig. 3.4). Protective devices are made from various materials, including polymers.
Spindles and their supports. The spindle - a type of shaft - serves to secure and rotate the cutting tool or fixture that carries the workpiece.
To maintain the accuracy of processing during a given service life of the machine, the spindle ensures the stability of the position of the axis during rotation and translational motion, the wear resistance of the supporting, seating and basing surfaces.
Spindles, as a rule, are made of steel (40Kh, 20Kh, 18KhGT, 40KhFA, etc.) and subjected to heat treatment (carburizing, nitriding, bulk or surface hardening, tempering).
To secure a tool or fixture, the front ends of the spindles are standardized. The main types of machine tool spindle ends are shown in Table. 3.2.
Rice. 3.4. The main types of protective devices for guides: a - guards; b - telescopic shields; c, d and e - tape; e - harmonica-shaped furs
Sliding and rolling bearings are used as spindle supports. The structural diagram of adjustable plain bearings made in the form of bronze bushings, one of the surfaces of which has a conical shape, is shown in fig. 3.5.
Spindle bearings use a lubricant in the form of a liquid (in hydrostatic and hydrodynamic bearings) or gas (in aerodynamic and aerostatic bearings).
There are single and multi-wedge hydrodynamic bearings. Single wedges are the simplest in design (sleeve), but do not provide a stable position of the spindle at high sliding speeds and low loads. This disadvantage is absent in multi-wedge bearings, which have several bearing oil layers covering the spindle neck evenly from all sides (Fig. 3.6).
Table 3.2
The main types of ends of machine spindles
Rice. 3.5. Adjustable plain bearings: a - with a cylindrical spindle neck: 1 - spindle neck; 2 - split sleeve; 3 - body; b - with a tapered neck of the spindle: 1 - spindle; 2 - solid sleeve
Rice. 3.6. Grinding wheel spindle support with hydrodynamic five-piece bearing: 1 - self-aligning liners; 2 - spindle; 3 - clip; 4 - screw; 5 - rolling bearings; 6 - screws with a spherical support end; 7 - cuffs
Hydrostatic bearings - plain bearings, in which the oil layer between the rubbing surfaces is created by supplying oil under pressure from the pump to them - provide high accuracy of the position of the spindle axis during rotation, have high rigidity and provide a liquid friction mode at low sliding speeds (Fig. 3.7 ).
Gas-lubricated bearings (aerodynamic and aerostatic) are similar in design to hydraulic bearings, but provide lower friction losses, which allows them to be used in high-speed spindle bearings.
Rolling bearings as spindle supports are widely used in machine tools of various types. Increased requirements are imposed on the accuracy of rotation of spindles, therefore, bearings of high accuracy classes are used in their supports, installed with a preload, which eliminates the harmful effects of clearances. Preload in angular contact ball and tapered roller bearings is created when they are installed in pairs as a result of axial displacement of the inner rings relative to the outer ones.
This displacement is carried out with the help of special structural elements of the spindle assembly: spacer rings of a certain size; springs that ensure the constancy of the preload force; threaded connections. In roller bearings with cylindrical rollers, the preload is created by deforming the inner ring 6 (Fig. 3.8) when it is tightened onto the tapered neck of the spindle 8 using a bushing 5 1. The bearings of the spindle bearings are reliably protected from contamination and leakage of lubricant by lip and labyrinth seals 7 .
Rolling bearings 4 are widely used as thrust bearings that fix the position of the spindle in the axial direction and perceive the loads arising in this direction. The preload of ball thrust bearings 4 is created by springs 3. The springs are adjusted with nuts 2.
Rice. 3.7. Hydrostatic bearing: 1 - bearing shell; 2 - spindle neck; 3 - a pocket that creates the bearing surface of the bearing (the arrows show the direction of supply of lubricant under pressure and its removal)
Rice. 3.8. Front support of the lathe spindle on rolling bearings: 1 - nuts; 2 - adjusting nuts; 3 - springs; 4 - thrust bearings; 5 - bushings; 6 - roller bearing inner ring; 7 - seals; 8 - spindle
An example of using angular contact ball bearings to absorb axial loads is shown in fig. 3.6. The preload is created by adjusting the position of the outer
bearing rings 5 with nut 4.
Typical mechanisms for the implementation of translational movement. Translational motion in the machines under consideration is provided by the following mechanisms and devices:
Mechanisms that convert rotational motion into translational: a gear wheel or a worm with a rack, a lead screw - a nut and other mechanisms;
Hydraulic devices with a pair of cylinder - piston;
Electromagnetic devices such as solenoids, used mainly in drives of control systems. Let us give examples of some of these mechanisms (see Table 3.1 for symbols).
The gear-rack pair has a high efficiency, which determines its use in a wide range of rack speeds, including in the drives of the main movement, which transmit significant power, and in the drives of auxiliary movements.
A worm-and-rack gear differs from a gear-rack pair in increased smoothness of movement. However, this transmission is more difficult to manufacture and has a lower efficiency.
The mechanism of the lead screw - nut is widely used in drives of feeds, auxiliary and installation movements and provides: a small distance that the moving element moves in one revolution of the drive; high smoothness and accuracy of movement, determined mainly by the accuracy of manufacturing the elements of the pair; self-braking (in pairs of sliding screw-nut).
In the machine tool industry, six accuracy classes have been established for lead screws and sliding nuts: 0 - the most accurate; 1, 2, 3, 4 and 5 classes, with the help of which they regulate the permissible deviations in pitch, profile, diameters and surface roughness parameter. The design of the nuts depends on the purpose
mechanism.
Pairs of lead screw - sliding nut due to low efficiency are replaced by rolling screw pairs (Fig. 3.9). These pairs eliminate wear, reduce frictional losses and can eliminate gaps by preloading.
The disadvantages inherent in pairs of sliding screw-nut and screw-rolling nut, due to the peculiarities of their operation and manufacture, are excluded in the hydrostatic screw-nut transmission. This pair works in friction with a lubricant; The transmission efficiency reaches 0.99; oil is supplied to pockets made on the sides of the nut thread.
Typical mechanisms for the implementation of periodic movements. In the process of work in some machines, periodic movement (change of position) of individual nodes or elements is required. Periodic movements can be carried out by ratchet and Maltese mechanisms, cam mechanisms and overtaking clutches, electric, pneumatic and hydraulic mechanisms.
Ratchet mechanisms (Fig. 3.10) are most often used in the feed mechanisms of machine tools, in which the periodic movement of the workpiece, cutting (cutter, grinding wheel) or auxiliary (diamond for dressing the grinding wheel) tool is performed during the overrun or reverse (auxiliary) stroke (in grinding and other machines).
In most cases, ratchet mechanisms are used for rectilinear movement the corresponding node (table, caliper, quill). With the help of a ratchet gear, circular periodic movements are also carried out.
Couplings are used to connect two coaxial shafts. Depending on the purpose, there are non-disengaging, interlocking and safety clutches.
Non-disengaging couplings (Fig. 3.11, a, b, c) are used for a rigid (deaf) connection of shafts, for example, a connection using a sleeve, through elastic elements or through an intermediate element that has two mutually perpendicular protrusions on the end planes and allows you to compensate for the misalignment of the connected shafts .
Rice. 3.9. A pair of rolling screw-nut: 1, 2 - a nut consisting of two parts; 3 - screw; 4 - balls (or rollers)
Rice. 3.10. Ratchet Diagram: 1 - ratchet; 2 - doggy; 3 - shield; 4 - thrust
Interlocking couplings (Fig. 3.11, d, e, f) are used for periodic connection of shafts. The machines use interlocking cam clutches in the form of disks with end teeth-cams and gear clutches. The disadvantage of such coupled clutches is the difficulty of their inclusion with a large difference in the angular velocities of the driving and driven elements. Friction clutches do not have the disadvantage inherent in cam clutches, and allow them to be switched on at any speed of rotation of the driving and driven elements. Friction clutches are conical and disc. In the drives of the main movement and feed, multi-plate clutches are widely used, which transmit significant torques with relatively small overall dimensions. The compression of the leading disks with the driven ones is carried out using mechanical, electromagnetic and hydraulic drives.
Rice. 3.11. Couplings for connecting shafts: a - rigid bushing type; b - with elastic elements; in - cross-movable; g - cam; d - multi-disk with a mechanical drive: 1 - washer; 2 - pressure plate; 3 - balls; 4 - fixed bushing; 5 - sleeve; 6 - nut; 7 - springs; e - electromagnetic: 1 - slotted bushing; 2 - electromagnetic coil; 3 and 4 - magnetically conductive disks; 5 - anchor; 6 - sleeve
Safety couplings (Fig. 3.12) connect two shafts when normal conditions work and break the kinematic chain when the load increases. A chain break can occur when a special element is destroyed, as well as as a result of slippage of mating and rubbing parts (for example, discs) or disengagement of the cams of two mating parts of the coupling.
As a destructible element, a pin is usually used, the cross-sectional area of \u200b\u200bwhich is calculated to transmit a given torque. The disengagement of the mating elements of the clutch occurs under the condition that the axial force arising on the teeth, cams 1 or balls 5
, during overloads exceeds the force generated by the springs 3 and regulated by the nut 4. When displaced, the movable element 2 of the coupling acts on the limit switch, which breaks the electric power circuit of the engine
drive.
Overrunning clutches (Fig. 3.13) are designed to transmit torque when the kinematic chain links rotate in a given direction and to disconnect the links when rotating in the opposite direction, as well as to transmit rotations of different frequencies to the shaft (for example, slow - working rotation and fast - auxiliary ). The overrunning clutch allows you to transfer additional (fast) rotation without turning off the main chain. In machine tools, roller-type clutches are most widely used, which can transmit torque in two directions.
Ratchet mechanisms are also used as overtaking clutches.
Rice. 3.12. Schemes of safety clutches: a - ball; b - cam; 1 - cams; 2 - movable element of the clutch; 3 - springs; 4 - nut; 5 - balls
Rice. 3.13. Overrunning roller clutch: 1 - clip; 2 - hub; 3 - rollers; 4 - driving fork; 5 - springs
3.3. Drives for main movement and feed movement
A set of mechanisms with a source of movement, which serves to actuate the executive body of the machine with given characteristics of speed and accuracy, is called a drive.
Metal-cutting machines are equipped with an individual drive; on many machines, the main movement, feed movement, auxiliary movements are carried out from separate sources - electric motors and hydraulic devices. The change in speed can be stepless and stepped.
As drives for metal-cutting machines, electric motors of direct and alternating current, hydraulic motors and pneumatic motors are used. Electric motors are the most widely used as machine tool drives. Where stepless regulation of the shaft speed is not required, asynchronous AC motors are used (as the cheapest and simplest). For stepless speed control, especially in feed mechanisms, thyristor-controlled DC motors are increasingly being used.
The advantages of using an electric motor as a drive include: high rotation speed, the possibility of automatic and remote control, as well as the fact that their operation does not depend on the ambient temperature.
Among the transmissions of motion from the engine to the working bodies of the machine, mechanical transmissions are most widely used. According to the method of transmission of movement from the leading element to the driven, mechanical transmissions are divided as follows:
Gears by friction with direct contact (friction) or with flexible connection (belt);
Direct contact gears (gear, worm, ratchet, cam) or with flexible connection (chain).
Friction transmissions with a flexible connection include belt transmissions (Fig. 3.14). In these gears, the pulleys of the drive and driven shafts are covered by a belt with a certain tension force, which ensures the appearance of a friction force between the belt and the pulleys necessary to transmit the force. The tension, limited by the strength of the belt, is regulated by pushing the shafts apart or by a special tensioner.
Belts are made of leather, rubberized fabric, plastic, they have a different cross-sectional shape. Belts with a flat section (Fig. 3.14, b) is used when transmitting high speed (50 m/s and above) with relatively little effort. Large power is transmitted by several V-belts (Fig. 3.14, c) or a poly-V-belt (Fig. 3.14, d). Gears with belts with a circular cross section (Fig. 3.14, e) are used for small relative forces and in gears between cross shafts. V-ribbed belts are widely used (see Fig. 3.14, d) to increase the friction force (at the same tension as for flat belts).
In friction and belt drives, slippage always occurs between rubbing surfaces, so the real gear ratio for them is:
where is the theoretical gear ratio; - slip coefficient.
To prevent slippage, toothed belts are used (Fig. 3.14, e).
Rice. 3.14. Scheme of belt transmission (a) and transmission with a flat belt (b), V-belt (c), poly-V-belt ( G), round belt (d), toothed belt ( e): 1 - pulling metal cable toothed belt; 2 - the base of the toothed belt made of plastic or rubber; 3 - pulley; - leading roller; and - the center of rotation and the diameter of the drive roller, respectively; - driven roller; and - the center of rotation and the diameter of the driven roller, respectively; - belt tension force; - distance between the centers of rotation of the driving and driven rollers
Chain drives (Fig. 3.15) (for lubrication and cooling systems), like toothed belt transmission, transmit rotation speed to the driven shaft more stably and can transmit high power.
Rice. 3.15. Chain drive: - drive sprocket; - driven sprocket
The gear train (Fig. 3.16) is the most common gear, as it provides high stability of rotation speeds, is capable of transmitting high powers and has relatively small overall dimensions. Gears are used to transmit rotation between shafts (parallel, intersecting, crossing), as well as to convert rotational motion into translational (or vice versa). The movement from one shaft to another is transmitted as a result of mutual engagement of gears forming a kinematic pair. The teeth of these wheels are specially shaped. The most common gearing is in which the profile of the teeth is outlined along a curve called the involute of a circle or simply involute, and the gear itself is called involute.
The drive with gear boxes is the most common drive for the main movement and feed movement in machine tools and is called the gearbox and feed box respectively.
Gearboxes (Fig. 3.17) are distinguished by their layout and by the method of switching speeds. The layout of the gearbox determines the purpose of the machine and its size.
Gearboxes with replaceable wheels are used in machine tools with a relatively rare drive setting. The box is characterized by simplicity of design, small overall dimensions.
Gearboxes with movable wheels (Fig. 3.17, a) are widely used mainly in universal manual machines.
Rice. 3.16. Types of gears for rotational movements: a and b - spur gear with external and internal gearing, respectively; in - helical cylindrical gear of external gearing; g - spur bevel gear; d - chevron wheel; e - worm gear
Rice. 3.17. Kinematic diagrams of gearboxes: a - with movable wheels: - gear wheels; b - with cam clutches: 0, I, II, III, IV - gearbox shafts; - gear wheels; - electric motor; Mf1, Mf2, MfZ, Mf4 - friction clutches; - claw clutch
The disadvantages of these boxes are: the need to turn off the drive before changing gears; the possibility of an accident in case of violation of the blocking and the simultaneous inclusion of two gears of the same group between adjacent shafts; relatively large dimensions in the axial direction.
Gearboxes with cam clutches (Fig. 3.17, b) are characterized by small axial displacements of the clutches during switching, the possibility of using helical and chevron wheels, and low switching forces. The disadvantages include the need to turn off and brake the drive when switching speeds.
Gearboxes with friction clutches, unlike boxes with dog clutches, provide smooth gear shifting on the go. In addition to the disadvantages inherent in boxes with cam clutches, they are also characterized by a limited transmitted torque, large overall dimensions, reduced efficiency, etc. Despite this, boxes are used in lathes, drilling and milling groups.
Gearboxes with electromagnetic and other clutches that allow the use of remote control are used in various automatic and semi-automatic machines, including CNC machines. To unify the drive of the main movement of such machine tools, the domestic machine tool industry produces unified automatic gearboxes (AKS) of seven overall dimensions, designed for a power of 1.5 ... 55 kW; number of speed steps - 4... 18.
Depending on the type of mechanisms used with gears that serve to adjust the feeds, the following feed boxes are distinguished:
With replaceable wheels at a constant distance between the axes of the shafts;
With movable wheel blocks;
With built-in stepped cones (sets) of wheels and exhaust keys;
Norton (with cap gear);
With guitars of interchangeable wheels.
To obtain feed boxes with desired characteristics, they are often designed using several of the listed mechanisms simultaneously.
Norton gearboxes are used in feed drives of screw-cutting machines due to the possibility of accurately implementing the specified gear ratios. The advantages of boxes of this type are a small number of gears (the number of wheels is two more than the number of gears), the disadvantages are low rigidity and accuracy of pairing of the included wheels, the possibility of clogging gears in the presence cutout in the box.
Feed boxes with interchangeable wheel guitars (Fig. 3.18) make it possible to adjust the feed with any degree of accuracy. The features of guitars with interchangeable wheels make them suitable for use in various types of machine tools, especially in serial and mass production machines. Such machines are equipped with appropriate sets of interchangeable wheels.
Rice. 3.18. Kinematic scheme (a) and design (b and c) of the guitar of replaceable gears: 1 - backstage; 2 - nut; 3 - screw; K, L, M, N - gears
3.4. General information about the technological process
machining
The process of creating wealth is called production.
The part of the production process that contains purposeful actions to change and (or) determine the state of the object of labor is called the technological process. The technological process can be attributed to the product, its component parts or to the methods of processing, shaping and assembly. The objects of labor include blanks and products. Depending on the execution method, the following elements of technological processes are distinguished:
Shaping (casting, molding, electroforming);
Processing (cutting, pressure, thermal, electrophysical, electrochemical, coating);
Assembly (welding, soldering, gluing, nodal and general assembly);
Technical control.
The completed part of the technological process, performed at one workplace, is called a technological operation. The definition of these terms is given in GOST 3.1109-82.
In production, a worker most often encounters the following types of descriptions of technological processes in terms of their level of detail:
A route description of a technological process is an abbreviated description of all technological operations in a route map in the sequence of their execution, without specifying transitions and technological modes;
Operational description of the technological process, a complete description of all technological operations in the sequence of their execution, indicating transitions and technological modes;
Abbreviated description of technological operations in the route map in the sequence of their execution, with full description individual operations in other technological documents is called a route-operational description of the process.
The description of manufacturing operations in their technological sequence is given in compliance with the rules for recording these operations and their coding. For example, cutting operations performed on machine tools are divided into groups. Each group is assigned certain numbers: 08 - program (operations on machine tools with program control); 12 - drilling; 14 - turning; 16 - grinding, etc.
When recording the content of operations, use established titles technological transitions and their conditional codes, for example: 05 - bring; 08 - sharpen; 18 - polish; 19 - grind; 30 - sharpen; 33 - grind; 36 - mill; 81 - fix; 82 - configure; 83 - reinstall; 90 - remove; 91 - install.
Part of the technological operation, carried out with a constant fixing of the workpieces, is called at camp. A fixed position occupied by a workpiece that is invariably fixed in a fixture relative to a tool or a fixed piece of equipment to perform a certain part of an operation is called a position.
The main elements of the technological operation include transitions. A technological transition is a completed part of a technological operation performed by the same means of technological equipment under constant technological conditions and installation. An auxiliary transition is a 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.
When registering technological processes, a set of technological documentation is created - a set of sets of documents of technological processes and individual documents necessary and sufficient to perform technological processes in the manufacture of a product or its components.
unified system technological documentation (ESTD), the following documents are provided: route map, sketch map, operational map, equipment list, material list, etc. Description of the content of technological operations, i.e. a description of the route technological process is given in the route map - the main technological document in the conditions of a single and pilot production, with the help of which the technological process is brought to the workplace. In the route map, in accordance with the established forms, indicate data on equipment, tooling, material and labor costs. The presentation of the operational technological process is given in operational maps compiled in conjunction with sketch maps.
A technological document can be graphic or textual. It alone or in combination with other documents defines the technological process or operation of manufacturing the product. A graphic document, which, according to its purpose and content, replaces the working drawing of a part in this operation, is called an operational sketch. The main projection on the operational sketch depicts the view of the workpiece from the side of the workplace at the machine after the operation. The machined surfaces of the workpiece on the operational sketch are shown by a solid line, the thickness of which is two to three times the thickness of the main lines on the sketch. The operational sketch indicates the dimensions of the surfaces processed in this operation and their position relative to the bases. You can also provide reference data indicating "dimensions for reference". The operational sketch indicates the maximum deviations in the form of numbers or symbols of the tolerance and fit fields according to the standards, as well as the roughness of the machined surfaces, which must be ensured by this operation.
The rules for recording operations and transitions, their coding and filling the cards with data are defined by standards and teaching materials the parent organization for the development of ESTD.
Control questions
1. Give formulas for determining the cutting speed during the main rotary motion.
2. How are the gear ratios of kinematic pairs of machine tools found?
3. What is the regulation range?
4. What are the requirements for machine beds and guides?
5. Tell us about the purpose and design of spindle assemblies and bearings.
6. What couplings are used in machine tools?
7. Define a drive and tell us about the drives used in machine tools.
8. What are the main elements of machine tool drives do you know?
9. Tell us about the types and designs of gearboxes.
10. What designs of feed boxes are used in machine tools?
11. What is called the technological process? Name the components of technological processes.
When the drawings do not need to show the design of the product and individual parts, but it is enough to show only the principle of operation, the transmission of motion (the kinematics of a machine or mechanism), diagrams are used.
scheme a design document is called, on which the component parts of the product, their relative position and relationships between them are shown in the form of symbols.
A diagram, like a drawing, is a graphic image. The difference lies in the fact that the details are depicted in the diagrams using conditional graphic symbols. These designations are greatly simplified images, reminiscent of details only in in general terms. In addition, the diagrams do not show all the details that make up the product. They show only those elements that are involved in the transmission of the movement of liquid, gas, etc.
Kinematic schemes
Symbols for kinematic diagrams are established by GOST 2.770–68, the most common of them are given in Table. 10.1.
Table 10.1
Symbols for kinematic diagrams
|
Name |
visual image |
Symbol |
|
Shaft, axle, roller, rod, connecting rod, etc. |
||
|
Plain and rolling bearings on the shaft (no type specification): A– radial b- persistent one-sided |
||
|
Shaft connection: A- free to rotate b– movable without rotation V- deaf |
||
|
Shaft connection: A- deaf b- articulated |
||
|
Clutch: A– cam one-sided b - cam double-sided V– friction double-sided (without specifying the type) |
||
|
Stepped pulley mounted on the shaft |
||
|
Flat belt transmission open |
||
|
Chain transmission (without specification of chain type) |
||
|
Gear transmissions (cylindrical): A b-c direct in – from oblique teeth |
||
|
Gear transmissions with intersecting shafts (bevel): A- general designation (without specifying the type of teeth) b-c direct in - with spiral g - s circular teeth |
||
|
Rack and pinion transmission (without specifying the type of teeth) |
||
|
Screw that transmits motion |
||
|
Nut on the screw that transmits the movement: A - one-piece b - detachable |
||
|
electric motor |
||
|
A - compression b - sprains V - conical |
As can be seen from the table, the shaft, axle, rod, connecting rod are indicated by a solid thickened straight line. The screw that transmits the movement is indicated by a wavy line. Gears are indicated by a circle drawn by a dash-dotted line on one projection, and in the form of a rectangle circled by a solid line, on the other. In this case, as in some other cases (chain transmission, rack and pinion gears, friction clutches, etc.), general designations (without type specification) and private designations (with type indication) are used. On a general designation, for example, the type of gear teeth is not shown at all, but on private designations they are shown with thin lines. Compression and extension springs are indicated by a zigzag line. To depict the connection of the part with the shaft, there are also symbols.
Conventional signs used in diagrams are drawn without adhering to the scale of the image. However, the ratio of the sizes of the conventional graphic symbols of the interacting elements should approximately correspond to their actual ratio.
When repeating the same signs, you need to perform them in the same size.
When depicting shafts, axles, rods, connecting rods and other parts, solid lines with a thickness s. Bearings, gears, pulleys, couplings, motors are outlined with lines about twice as thin. Axes, circles of gears, keys, chains are drawn with a thin line.
When performing kinematic diagrams, inscriptions are made. For gears, the module and number of teeth are indicated. For pulleys, their diameters and widths are recorded. The power of the electric motor and its speed are also indicated by the type inscription N= 3.7 kW, P= 1440 rpm.
Each kinematic element shown in the diagram is assigned a serial number, starting from the engine. The shafts are numbered in Roman numerals, the rest of the elements in Arabic.
The serial number of the element is put down on the shelf of the leader line. Under the shelf indicate the main characteristics and parameters of the kinematic element.
If the diagram is complex, then the position number is indicated for the gears, and the specification of the wheels is attached to the diagram.
When reading and drawing up diagrams of products with gears, one should take into account the features of the image of such gears. All gears, when they are depicted as circles, are conditionally considered transparent, assuming that they do not cover the objects behind them. An example of such an image is shown in Fig. 10.1, where in the main view the circles show the engagement of two pairs of gears. From this view, it is impossible to determine which of the gears are in front and which are behind. This can be determined from the view on the left, which shows that a pair of wheels 1 – 2 is in front, and a pair 3 – 4 located behind her.
Rice.10.1.
Another feature of the image of gears is the use of so-called expanded images. On fig. 10.2, two types of gearing scheme are made: non-deployed (a) and deployed ( b).
Rice. 10.2.
The location of the wheels is such that in the left view the wheel 2 covers part of the wheel 1, as a result, there may be ambiguity when reading the diagram. To avoid errors, it is allowed to do as in Fig. 10 .2 , b, where the main view is preserved, as in Fig. 10.2, A, and the left side view is shown in expanded position. In this case, the shafts on which the gears are located are spaced from each other at a distance of the sum of the radii of the wheels.
On fig. 10.3, b an example of a kinematic diagram of a gearbox of a lathe is given, and in fig. 10.3, A its visual representation is given.
Reading kinematic diagrams is recommended to start with the study of the technical passport, according to which they get acquainted with the device of the mechanism. Then they proceed to reading the diagram, looking for the main details, while using their symbols, some of which are given in Table. 10.1. Reading the kinematic diagram should start from the engine, which gives movement to all the main parts of the mechanism, and go sequentially along the transmission of motion.
