Special machines are created to process certain parts or even to perform only certain operations and are mainly used in mass and large-scale production. When designing a special machine, you must:

a) reduce to a minimum the main technological time, which is achieved by using the most advantageous cutting tool designs, optimal cutting conditions, multi-tool processing;

b) reduce auxiliary time to a minimum - achieved by full automation of machine control;

c) reduce to a minimum the time spent on tune-up, which is achieved by the use of quick-change interchangeable tools and automation of tune-up.

Adjustment and adjustment of special stacks is carried out using interchangeable gears, interchangeable cams or copiers, which simplifies the design of the drive compared to a universal machine.

Special machines are manufactured in one copy or in a small series, so the designer, as applied to single and small-scale production, can more widely use welded structures instead of cast ones, processing machine parts by marking, etc.

Since special machines are used to process specific parts, we must strive to create them repurposable using the components of already mastered machines in their design.

Specialized machines occupy an intermediate position between universal and special machines. These machines with the help of interchangeable devices and fixtures can be reloaded in a relatively short period of time to process another part of the same name, but with different sizes. Therefore, specialized stacks are special machines with the possibility of readjustment; they can also be attributed to universal machines of a simplified design.

When designing a specialized machine, it is necessary to take into account the design features of both universal and special machines. Specialized machines should be created on the basis of normal series of general-purpose machines with maximum unification of the main components and details

In recent years, requirements for accuracy and quality on top of parts of most modern machines and devices have risen sharply. Such high requirements can be ensured only in the manufacture of parts on high-quality precision machines. Improving the accuracy of machine tools is achieved by improving the designs of individual elements and nodes, increasing rigidity and vibration resistance, reducing thermal deformation, improving the accuracy of manufacturing parts and the quality of assembly of machines.

To increase the rigidity of the machines should:

a) create closed frame structures of machines;

b) apply solid cast beds having a box-shaped shape with inner partitions and diagonal ribs;

c) reduce the number of joints and improve the quality of their processing;

d) properly design nodes in terms of the rational distribution of loads in the machines;

e) apply preloading (preload) in mates and bearings (especially spindle bearings);

e) apply the slide guides with preload:

g) increase the diameter of the spindle, reduce the length of its console;

h) apply ball and hydrostatic screw pairs in the feed drive;

i) reduce the number of links in the kinematic chains;

j) increase the rigidity of the fastening of tools;

k) apply reliable zakreilenpe moving nodes in the processing process.

To increase the vibration resistance of the machines should:

a) to improve their static and dynamic characteristics;

b) make waterproofing of machines with the aim of minimizing the influence of external disturbances transmitted through the base;

c) apply various damping devices;

d) to remove vibration sources from the machine - electric motors; pumps for hydraulic systems, lubrication and cooling systems, etc .;

d) apply an adjustable electric drive to reduce the number of gears that can be sources of disturbance; especially good result!.! gives a thyristor drive having a low noise level;

e) use a split drive;

g) use high-precision bearings in the spindle bearings;

h) use helical wheels instead of spur gears;

i) improve the accuracy of the manufacture of gears and pulleys of belt drives; use endless high quality belts in belt drives;

j) choose rational processing modes and tool geometry;

l) to balance the rapidly rotating parts of the machine and the electric motor;

m) to increase the accuracy of manufacturing parts and the quality of assembly of machines, etc.

To reduce the thermal deformation of machines, the following measures are taken:

a) create thermosymmetric structures of machine components;

b) apply designs that provide compensation for temperature deformations;

c) remove heat sources from the flock (electrical equipment, hydraulic system tanks, emulsions and lubricants);

d) apply intensive cooling of integrated drives;

d) reduce the loss of shatter in the drives;

e) select materials for mates with similar or identical linear expansion coefficients, and also apply materials with small linear expansion coefficients;

g) place the hydraulic drive of the table drive (or another unit) next to the machine, and not under the table;

h) devices for cooling hydraulic oil;

i) artificially straighten the temperature range of the stack by heating or cooling its individual parts, etc.

The accuracy and quality of the machine, in addition, are provided:

a) the choice of rational layout of the machine;

b) the right choice of materials and heat treatment for critical parts of the stack;

c) the use of rolling guides and hydrostatic guides;

d) the use of gear chains and other nodes of gears with a device for selecting gaps;

e) the use of devices for the protection of parasites;

c) the use of devices for fine purification of coolant in order to increase the purity of processing;

g) the use of suction devices to remove dust from the grinding zone and dressing circle;

h) the use of mechanisms to compensate for wear of the circle;

i) the use of digital size indication devices;

j) the use of automatic control of the dimensions of parts during processing with automatic adjustment of the size;

k) high-quality aging of the basic parts of the machine;

m) hardening and grinding of guides;

m) the use of more advanced methods of thin scraping guides;

n) increasing the general culture of production.

The accuracy and roughness of machined surfaces on precision machine tools is largely dependent on the accuracy of the spindle bearings. Multi-bearing plain bearings are used in the spindle assemblies of precision machine tools

Fig. 90. Methods of adapting preload (dashed lines show ball angular contact bearings)

oil wedges (see Figs. 77 and 78), hydro and aerostatic bearings and special rolling bearings.

Rolling bearings. To eliminate the gaps between the rolling elements and the bearing rings and to increase the stiffness of the bearings, two additional tightnesses are also used. For this bearing I ^

This is a technological machine that is designed for processing materials by cutting. The purpose of the machine is to obtain parts of a given shape and size (with the required accuracy and quality of the machined surface). On the machines workpieces are processed not only from metal, but also from other materials, therefore the term “metal-cutting machine” is conditional.

By the type of work performed, metal cutting machines are divided into groups, each of which is divided into types, united by common technological features and design features.

Serial models of machines are assigned a digital or alphanumeric designation. As a rule, a designation consists of three to four numbers and one to two letters. The first digit is the number of the group to which the machine belongs, the second is the type number of the machine, the third and fourth characterize one of the main parameters of the machine or the workpiece processed on it (for example, center height, bar diameter, table dimensions, etc.).

The letter after the first or second digit indicates that the machine has been upgraded, the letter after the numbers indicates the modification (modification) of the basic model of the machine. If the letter is at the end of the model designation, then it indicates the accuracy class of the machine.

By the degree of versatility, machines are divided into universal, specialized and special.

Universal machines are designed for processing parts of a wide range in individual and small-scale production. These machines are characterized by a wide range of speed and feed control. Universal machines include turning, screw-cutting, turning-revolving, drilling, milling, planing, etc. (both with manual control and CNC).

Specialized machines are used to process parts of the same name, but in different sizes. These include machines for processing pipes, couplings, crankshafts, as well as gear and thread processing, turning-backing, etc.

Specialized machines are characterized by quick readjustment of interchangeable devices and accessories; they are used in serial and large-scale production.

Special machines are used to process parts of the same name and size; they are used in large-scale and mass production.

In the designation of specialized and special machines before the model number enter the manufacturer's index of one or two letters.

By the degree of accuracy of processing, machines are divided into five classes:

H - normal accuracy; most universal machines belong to this class;

P - increased accuracy; machines of this class are manufactured on the basis of machines of normal accuracy, but the requirements for precision machining of critical machine parts, assembly quality and regulation are much higher;

B - high accuracy achieved through the use of a special design of individual units, high requirements for the accuracy of manufacturing parts, the quality of assembly and regulation of the machine as a whole;

A - particularly high accuracy; for these machines are even more stringent requirements than for class B machines;

C - particularly accurate, they produce parts for machines of accuracy classes B and A.

Machines of accuracy classes A, B and C are called precision (from French precision - precision). These machines are best used in thermoconstant workshops, the temperature and humidity in which are automatically regulated.

A metal cutting machine (or, more generally, a machine tool) is a technological machine on which, by removing chips from a workpiece, a part is obtained with a given size, shape, relative position and surface roughness. On the machines workpieces are processed not only from metal, but also from other materials, therefore the term "metal-cutting machines" becomes obsolete and becomes conditional. A workpiece is called a work item from which a part is made by changing the shape, size and surface properties. The latter is a product of labor - a product intended for sale (in the main production) or the company's own needs (in auxiliary production).

Machines can be classified according to various criteria, the main of which are discussed below.

By the degree of versatility distinguish universal, specialized and special machines.

Universal machines  (or general-purpose machines) are used to process parts of a wide range, limited only by marginal dimensions, a set of tools and technological operations.

Specialized machines  used for processing similar parts (pipes, couplings, crankshafts and fasteners) in a certain range of sizes.

Special machines  used to process one specific part, less often - several parts of the same type.

Specialized and special machines are mainly used in large-scale and mass production.

By the degree of accuracy of processing, machines are divided into five classes:

• normal accuracy  (H); most universal machines belong to this class;
• high accuracy  (P); in the manufacture of machines of this class on the basis of machines of normal accuracy, they impose increased requirements on the accuracy of processing critical parts, the quality of assembly and adjustment of the machine;
• high precision  (B) achieved due to the special design of individual units, high requirements for the accuracy of manufacturing parts, the quality of assembly and adjustment of the machine as a whole;
• particularly high precision  (A) in the manufacture of which they impose even more stringent requirements than in the manufacture of class B machines;
• particularly accurate  (C) machine tools, or master machines.

To ensure the accuracy of the work of class B, A and C machines, it is necessary to maintain constant, automatically controlled values ​​of temperature and humidity in production facilities.

The degree of automation distinguish between mechanized and automated machines (automatic and semi-automatic).

Mechanized machine has one automated operation, such as clamping a workpiece or feeding a tool.

MachineCarrying out processing, it makes all the working and auxiliary movements of the cycle of the technological operation and repeats them without the participation of the worker, who only observes the work of the machine, controls the quality of processing and, if necessary, adjusts the machine, that is, adjusts it to restore the accuracy achieved during adjustment mutual arrangement of the tool and the workpiece, the quality of the workpiece. (A cycle means a period of time from the beginning to the end of a periodically repeating technological operation, regardless of the number of simultaneously manufactured parts.)

Semiautomatic device  - a machine operating with an automatic cycle, the repetition of which requires the intervention of a worker. For example, a worker must remove a part and install a new workpiece, and then turn on the machine for automatic work in the next cycle.

By the location of the spindle, the machines are divided into horizontal, vertical, inclined and combined.

Depending on the mass, light (up to 1 t), medium (up to 10 t) and heavy (over 10 t) machines are distinguished, among which it is possible to distinguish especially heavy, or unique (more than 100 t).

The totality of all types and sizes of manufactured machines is called type. To designate the model of the machine, which is produced in series, the classification adopted by the Experimental Research Institute of Metal-Cutting Machines (ENIMS), according to which all the machines are divided into nine groups, is adopted. Each group, in turn, is divided into nine types characterizing the purpose of the machine, its layout and other features.

The machine model is indicated by three or four digits with the addition of letters in some cases. Thus, the designation of the model 16K20P screw-cutting lathe should be deciphered as follows: a screw-cutting lathe (first two digits) with a center height (half of the largest machining diameter) 200 mm, increased accuracy P and another modification K. When designating machines with numerical control (CNC) add more letters and numbers, for example 16K20PFZ (ФЗ - numerical control of three coordinate movements).

To designate special and specialized machines, each machine-tool plant is assigned an index of one or two letters, after which the registration number of the machine is placed. For example, Moscow Machine-Tool Building OJSC “Red Proletariat” has an MK index.

test questions

1. What is a metal cutting machine?
2. How are metal-cutting machines classified according to the degree of versatility, accuracy, automation?
3. Tell us how the model of the machine is designated?

Metal-cutting machines produced by domestic manufacturers are divided into several categories, which are characterized by the corresponding classification. You can determine which category this or that equipment belongs to by marking it, which says a lot to those who understand it. However, no matter what category the metal-cutting device belongs to, the essence of processing on it comes down to the fact that the cutting tool and the part make forming movements, namely they determine the configuration and dimensions of the finished product.

The most common types of machine tools: 1-6 - turning, 7-10 - drilling, 11-14 - milling, 15-17 - planing, 18-19 - long, 20-24 - grinding.

Types of metal cutting equipment

Metal-cutting machines, depending on the purpose, are divided into nine main groups. These include the following devices:

1. turning  - all varieties (in the markings are indicated by the number "1");
2. drilling and boring  - machines for drilling operations and boring (group "2");
3. grinding, polishing, lapping  - metal-cutting machines for lapping, grinding, grinding and polishing technological operations (group "3");
4. combined  - metal cutting devices for special purposes (group "4");
5. thread and gear processing  - machines for processing elements of threaded and gear joints (group "5");
6. milling  - machines for milling operations (group "6");
7. mortising, planing and lingering  - metal cutting machines of various modifications, respectively, for planing, grooving and broaching (group "7");
8. split  - equipment for cutting work, including saws (group "8");
9. various  - examples of such metal-cutting units - centerless-peeling, saw-cutting and others (group "9").

Groups and types of machine tools (click to enlarge)

In addition, metal cutting machines can be one of the following types:

• multi- and single-spindle, specialized (semi-automatic and automatic), multi-cutting, revolving, drilling-detachable, rotary, frontal and special;
• equipment for performing technological operations of boring and drilling: multi- and single-spindle, semiautomatic devices, vertical, horizontal and radial type, boring devices of coordinate, diamond and horizontal type, different drilling models;
• various types of grinding machines (flat, internal and circular grinding), peeling and polishing equipment, grinding and specialized units;
• types of metal-working machines designed for machining elements of gear and threaded joints: gear-cutting (including those designed for machining bevel gears), gear-cutting - for cylindrical gears, gear-milling, thread-cutting, thread-and gear-grinding, gear-finishing, testing, thread-milling, devices for processing the ends of teeth and elements of worm pairs;
• metal-cutting machines related to the milling group: cantilever (vertical, horizontal and wide-universal models) and non-cantilever (vertical devices, longitudinal, copy and engraving models);
• planing equipment and models for this purpose: longitudinal machines on which one or two racks are installed; horizontal and vertical broaching devices;
• cutting equipment: equipped with either a smooth metal disk, a cutter or saws of various designs (tape, disk, hacksaw); correct cutting types of metalworking machines;
• other types of machines for processing metal billets: dividing, used to control drills and grinding wheels, filing, balancing, right and centerless-peeling, sawing.

Vertical milling machine - one of the representatives of an extensive milling group

The classification of metal cutting machines is also carried out according to the following parameters:

• by weight and overall dimensions of the equipment: large, heavy and unique;
• by level of specialization: machines designed to process workpieces of the same size - special; for parts with different but identical sizes - specialized; universal devices on which it is possible to process parts of any size and shape;
• according to the degree of processing accuracy: increased - P, normal - N, high - B, especially high accuracy - A; also distinguish machines on which you can perform particularly precise processing - C, they are also called precision.

Machine marking

The classification of equipment intended for the processing of metal blanks suggests that, having seen its marking, any specialist will be able to immediately tell which metal cutting machine is in front of him. This marking contains alphanumeric characters that indicate individual characteristics of the device.

The first digit is the group to which the metal cutting machine belongs, the second is the type of device, its type, the third (and in some cases the fourth) is the main unit size.

After the numbers listed in the marking of the model, there may be letters that indicate whether the model of the metal cutting machine has special characteristics. These characteristics of the device may include its level of accuracy or an indication of a modification. Often in the designation of the machine the letter can be found after the first digit: this indicates that you have a modernized model, in the standard design of which any changes have been made.

As an example, the marking of the 6M13P machine can be decoded. The numbers in this designation indicate that we have a milling machine ("6") of the first type ("1"), which belongs to the 3rd standard size ("3") and allows you to perform processing with increased accuracy (letter "P" ) The letter "M", present in the labeling of this device, indicates that it has undergone modernization.

Automation levels

Types of lathes, as well as devices for any other purpose, which are used in conditions of mass and large-scale production, are called aggregate. They got this name due to the fact that they are completed from the same type of units (assemblies): bed, work heads, tables, spindle units and other mechanisms. Completely different principles are used to create machines that are necessary for small-scale and single production. The design of such devices, which are highly versatile, can be completely unique.

The classification of lathes (as well as equipment of any other categories) according to the level of automation implies their division into the following types:

1. manual models, all operations on which are carried out in manual mode;
2. semi-automatic, in which part of the technological operations (installation of the workpiece, start-up of the device, removal of the finished part) is performed in manual mode (all other operations related to auxiliary operations are automatic);
3. automatic, for which you only need to set the processing parameters, all other operations they perform independently, in accordance with a given program;
4. metal-cutting units with CNC (all processes on such machines are controlled by a special program that contains an encoded system of numerical values);
5. metal cutting equipment belonging to the category of flexible automated modules.

The most prominent representatives of machine tools are CNC devices, which are controlled by a special computer program. Such a program, which the operator enters into the machine’s memory, determines almost all parameters of the unit operation: spindle speed, machining speed, etc.

All types of metalworking machines, equipped with CNC system, contain in their design the following typical elements.

• An operator’s console (or console) through which a computer program is stored in the machine’s memory that controls its operation. In addition, with the help of such a remote control, it is also possible to carry out manual control of all parameters of the unit operation.
• The controller is an important element of the CNC system, with the help of which not only control commands are transmitted to the working elements of the equipment and the correctness of their execution is monitored, but also all necessary calculations are made. Depending on the degree of complexity of the model of the unit, both a powerful compressor and a conventional microprocessor can be used as a controller for equipping it.
• Screen or display acting as a control and control panel for the operator. Such an element allows real-time monitoring of the operation of the metal-cutting machine, control of the machining process, and, if necessary, promptly change the parameters and settings.

The principle of operation of metalworking machines equipped with a CNC system is simple. A program is pre-written that takes into account all the requirements for processing a particular workpiece, then the operator enters it into the machine controller using a special programmer. Commands incorporated into such a program are sent to the working elements of the equipment, and after they are executed, the machine is automatically turned off.

The use of metal-cutting machine tools equipped with numerical program control allows machining with high accuracy and productivity, which is the reason for their active use for equipment of industrial enterprises producing products in large series. Due to their high level of automation, such units are perfectly integrated into large automated lines.

One of the signs of the classification of machines is their degree of universality. It characterizes the variety of parts and operations for which the machine is suitable. The greater this diversity, the greater the technological capabilities of the machine.

From this point of view, all machines are divided into 4 groups:

General purpose machines  (widely-universal) - screw-cutting, vertical and horizontal milling, vertical and radial drilling, circular grinding, etc.

General purpose machines with increased productivity  - turning-revolving, turning automatic machines and semiautomatic devices, longitudinally and rotary-milling, centerless grinding, etc. (less versatile, have a smaller range of rotational speeds and feeds).
Machines of a specific purpose (specialized)  - gear cutting, gear milling, turning and copying, etc. (for operations of one name, a certain type of parts).

Special machines  - to perform only one operation in a single process. Special machines are divided into two types: ordinary special and aggregate.

The most widely used aggregation for machine tools drilling and boring groups.

In some cases, a special machine is created by upgrading any machine of another group, then they are called specialized. For example, it turns a lathe into a copy-milling machine (for machining the blade blade of a gas turbine engine), etc.

In ENIMS, a modern classification of machine tools has been developed. As the defining parameters of the classification, taken the detailed and target specialization, as well as the degree of automation of the equipment.

When describing the detailed specialization of systems, it is considered expedient to use the above terminology. According to the degree of automation, machines are divided into automatic, automated and non-automated.

In addition, the machines are further divided into single-purpose and multi-purpose (this term appeared together with CNC machines).

The following classification criteria is the accuracy of the machines:
   H - machines of normal accuracy - 16K20.
P - machines of high accuracy, which is provided by improving the quality of manufacture and assembly of machines of normal accuracy - 16K40P, 53A30P.
   B - high precision machines (special design of individual units and high requirements for the manufacture, assembly and adjustment of the machine) - 3U10V.
   A - machines of especially high accuracy (higher requirements for manufacturing than in class B) - 16B16A, 3U10A.
   C - machines of particular precision - master machines (intended for the manufacture of parts for machines of classes A and B) - 2421С - coordinate-boring.
   The machines of classes B, A, C are operated in rooms with constant temperature and humidity.

Technological processes are being developed both in the design of new workshops and factories, and for existing workshops. In the first case, focus on the latest machine tools. In the second - develop TP taking into account the available equipment.
   When choosing equipment you should be guided by the following:

1. Technological appointment of machines - compliance with a specific operation.
2. Dimensions of the machine, its power and range of modes of its operation.
3. The accuracy of the machine and the required accuracy of manufacturing parts.
4. The volume of production of products - the performance of the machine.
5. The cost of equipment.

The range of machine quality indicators in GOST 4.93-83 is more fully described.

Machine tools depending on the type of treatment , divided into nine groups, and each group - into ten types (subgroups), characterizing the purpose of machines, their layout, degree of automation or the type of tool used. Group 4 is designed for EDM, ultrasonic and other machines.

The designation of the machine model consists of a combination of three or four numbers and letters. The first digit indicates the group number, the second number of the subgroup (machine type), and the last one or two digits are the most characteristic technological parameters of the machine.

For example:

1. 1E116 means single-spindle automatic turret with the largest diameter of the bar being machined 16 mm;
2. 2Н125 means vertical drilling machine with the largest nominal drilling diameter of 25 mm.

The letter after the first digit indicates the different versions and upgrades of the basic basic model of the machine. The letter at the end of the digital part means the modification of the base model, the accuracy class of the machine or its features.

The following indexing of machine tool models with program control is adopted:
   C - with cyclic control;
   F1 - with digital position indexing, as well as with a preliminary set of coordinates;
F2 - with positional CNC system,
   FZ - with contouring CNC system; F4 - with a combined CNC system.
   For example:

1. 16D20P - high-precision turning lathe;
2. 6Р13К-1 - vertical milling console machine with a copier;
3. 1G340PTs - turning-turret machine with a horizontal head, high accuracy, with cyclic program control;
4. 2Р135Ф2 - vertical drilling machine with a revolving head, a cross table and with a positional system of numerical control;
5. 16K20FZ - lathe with contour numerical control system;
6. 2202VMF4 - a multi-purpose (drilling, milling and boring) horizontal machine of high precision with a tool magazine and with a combined CNC system (the letter M means that the machine has a tool shop).

Special and specialized machines are designated by the letter index (of one or two letters) assigned to each plant, with the model number of the machine. For example, mod. MSH-245 - semiautomatic reysoshiruyushchy of the increased accuracy of the Moscow plant of grinding machines.