Lathe grinding machine. Types of metal grinding machines and their operational features

A grinding machine is a device used to process workpieces made of various materials with an abrasive tool and can provide surface roughness from 0.02 to 1.25 microns. Grinding machines, which can have different designs, make it possible to effectively solve problems associated with processing the surfaces of parts made of different materials.

Application of grinding machines

Using a grinding machine, you can carry out a number of technological operations:

• grinding of internal as well as external surfaces of parts having different shape and purpose;
• sharpening of tools for various purposes;
• peeling, grinding, as well as cutting of metal castings and products with complex profiles;
• processing of gear parts and threaded parts;
• formation of keyed and spiral-type grooves on steel bars.

A grinding machine is practically indispensable when working with parts made of ceramic and magnetic materials that are difficult to process and highly fragile. In addition, grinding machines are capable of performing technological operations of grinding and roughening at high speed modes, which makes such equipment efficient and productive. On these machines, it is possible to remove a large amount of metal from the surface of the workpiece in a short period of time during processing.

The video below shows the operation of a CNC cylindrical grinding machine:

All grinding machines operate on the same principle: metal processing is carried out by simultaneous rotation and movement or rotation of the workpiece. The working surface is the periphery or end of the abrasive wheel, and the workpiece moves relative to it along a straight or arc path. Any grinding machine contains in its design several kinematic chains that provide:

• movement of the work table in the longitudinal and transverse directions, which is possible thanks to a hydraulic drive;
• rotation of the working tool - the grinding wheel, carried out due to the individual drive of the working tool;
• feeding the workpiece or tool in the transverse direction due to a hydraulic or electromechanical drive;
• wheel dressing, which can be done manually using an electromechanical or hydraulic system;
• rotation of the workpiece or work table;
• supply of the working tool to depth, which can be performed using a hydraulic or mechanical drive.

Classification of grinding equipment

Depending on the application, grinding machines are divided into a number of types.

Cylindrical grinders

This equipment is designed for grinding cylindrical (Ø 25–600 mm) and conical workpieces. Such machines have in their design a spindle that rotates in a horizontal plane, which can move on a special slide. The part to be machined may be clamped in the chuck or between the centers of the tailstock and headstock.

Universal cylindrical grinders

Such machines are used for grinding the outer and end surfaces of cylindrical workpieces (Ø 25–300 mm), as well as conical parts. To perform processing, workpieces can be fixed in centers or in a chuck.

Plunge cylindrical grinders

Grinding machines of this type are used for processing cylindrical (Ø 150–400 mm), conical and profile workpieces, which are fixed in the centers of the equipment. Processing is carried out due to the transverse movement (cutting) of the abrasive wheel.

Centerless cylindrical grinders

Processing on such equipment can be carried out according to two schemes: by pass (cylindrical surfaces (Ø 25–300 mm)) and by plunge method (cylindrical, conical and profile surfaces). Distinctive feature The disadvantage of grinding machines of this type is that their design does not provide centers for fixing workpieces.

Roll grinders

This includes machines for grinding rolling rollers of cylindrical, conical and profile configurations. Fixation of workpieces on machines of this type is carried out using equipment centers.

For grinding crankshaft journals

On such machines, working using the plunge method, simultaneous or sequential grinding of the crankpins of crankshafts is performed.

Internal grinding

These devices allow the processing of cylindrical and conical holes in a wide range of sizes (with a diameter of 1–10 cm on a bench grinder and up to 100 cm on a production one).

Surface grinding

Processing on such equipment is performed with the end or periphery of the abrasive wheel. Grinding machines of this type can be equipped with additional devices, which makes it possible to process metal workpieces of complex configurations. Depending on the location of the spindle, they can be horizontal or vertical. The design of such devices may also include one or two columns.

Double-sided surface grinders

This equipment can simultaneously process two flat surfaces, which significantly increases its productivity. Such grinding machines, in which the workpieces are fixed on a special feeding device, can be of a vertical or horizontal type.

For grinding guides

The maximum length of guides that can be machined with these grinding machines is 1000–5000 mm. Guides of these types are equipped with beds, work tables, slides and other equipment components for various purposes.

Universal sharpening

Such grinding machines are used for sharpening various tools with a maximum diameter of 100–300 mm (taps, reamers, countersinks, cutters, etc.). The technical capabilities of equipment of this type make it possible to equip it with additional devices for processing cylindrical workpieces, as well as for internal and end grinding.

Roughing and grinding

This grinding equipment is used for roughening and cleaning the surface of workpieces by grinding. These machines use abrasive wheels with a diameter of 100–800 mm.

Flat lapping

This grinding equipment is used to grind workpieces with flat and cylindrical surfaces. The diameter of the abrasive discs that are installed on such machines is 200–800 mm.

Circular lapping

This equipment is used to grind in calibration and measuring instruments made of metal. The maximum diameter of gauges and tools that can be processed on machines of this type is 50–200 mm.

Grinding and lapping

With the help of such equipment, holes are ground in, the maximum diameter of which is 100–300 mm.

Grinding and finishing

These are machines designed to perform finishing (lapping) operations. Such devices process various metal products: crankshafts with a maximum diameter of 100–200 mm, equipment spindles, pistons, etc.

Polishing

Such machines are used to polish metal parts. This universal equipment can be used to polish flat, cylindrical, conical, internal surfaces, as well as workpieces of complex configurations. An endless belt with a width of 100–200 mm or a soft polishing wheel with a diameter of 100–200 mm can be used as a working tool on these machines.

Honing

There are also honing machines that are used to perform fine grinding (0.04–0.08 mm per diameter).

Making a simple grinding machine with your own hands

Considering the fact that serial grinding equipment is not cheap, it makes sense to think about making such a machine yourself. Even the simplest homemade machine, which is not at all difficult to make, will allow you to high efficiency and high quality grinding of workpieces of various configurations.

Load-bearing element homemade machine to perform grinding work there is a frame on which two drums and an electric motor are mounted. To make the frame, you can use a thick steel sheet, from which a platform of the required size is cut out.

With the engine, everything is much simpler: it can be removed from an old washing machine that has already served its useful life. The drums can be made in sets; for this it is convenient to use a chipboard, from which discs of the required diameter are cut.

Drive shaft mount Driven drum Motor mount

As an example, we will analyze the sequence of steps for manufacturing, the frame of which has dimensions of 50x18 cm. First of all, the frame itself is cut out of a steel sheet, as well as the work table on which the electric motor will be mounted. The dimensions of such a table will be approximately 18x16 cm.

It is important that the ends of the bed and work table, which will be connected, be cut as evenly as possible. The thick sheet of metal from which you will make the frame and work table is difficult to cut by hand, so it is better to perform this procedure on milling machine. It is necessary to drill three holes in the frame and work table and securely connect them with bolts. Only after this is the motor installed and securely connected to the surface of the work table so that the base of the motor fits snugly to the surface of the platform.

When choosing an electric motor for your homemade grinding equipment, it is important to pay attention to the power: it should be at least 2.5 kW, and the rotation speed should be about 1500 rpm. If you use a drive with more modest characteristics, the machine will have low efficiency. You can avoid the need to use a gearbox if you correctly select the diameters of the drive and tension drums.

The diameters of the drums should be selected depending on the speed at which the abrasive belt will move. So, if the belt speed should be approximately 20 m/sec, then it is necessary to make drums with a diameter of 20 cm. To install the tension drum, a fixed axis is used, and the drive one is fixed directly on the electric motor shaft. To make rotation of the tension drum easier, a bearing assembly is used. It is best to make the platform on which the tension drum is installed with some bevel; this will ensure smooth contact of the abrasive belt with the workpiece being processed.

It won’t be particularly difficult to make drums for a homemade grinding machine. To do this, you need to cut square blanks measuring 20 by 20 cm from chipboard, and drill a hole in the center of each of them. These blanks are then assembled into a 24 cm thick package, which is machined to form a cylindrical drum with a diameter of 20 cm.

To prevent the abrasive belt from slipping on the drums, you can stretch wide rubber rings onto their surface, which are usually cut from the inner tube of a bicycle or moped. The width of the abrasive tape, which you can make yourself, should be about 20 cm.

Belts for belt sanding machines

Both in production and at home, grinding machines are often used, the working tool of which is a cloth belt with a layer of abrasive powder. The basis of such tapes is dense material (calico, twill) or special paper, and the abrasive layer is fixed on them using an adhesive composition.

The effectiveness of using such a tape depends on a number of parameters: the density of application of the abrasive powder and the composition of its grains. Belts on which the powder occupies no more than 70% of their area are more effective. This is explained by the fact that the processed material does not get clogged between the abrasive grains of such a tape. Both natural and artificial materials can be used as an abrasive powder applied to the working surface of the belt, but all of them must have high hardness.

Belts installed on a grinding machine are classified by a number indicating the size of the abrasive grains, expressed in hundredths of a millimeter. The reliability and effectiveness of such a tape also depends on the type of glue that is used to fix the abrasive grains. Today, two types of such glue are used: flesh and synthetic resin.

Specialists machine-building enterprises, visiting foreign exhibitions metalworking equipment, are witnesses to the success of such technical solution, as the combination of several technological operations and even processes on one machine, and in various combinations. It seems that there are no operations left in production, even the most difficult to combine, that would not be combined in an attempt to increase the accuracy and productivity of processing by reducing the number of reinstallations.

This idea, which originated a long time ago and was actually implemented in 1992 by Emag, which presented an inverted vertical lathe at the METAV92 exhibition, became a real material force just a few years later. Proof of this is over 5,000 machines of this configuration, sold to various factories, mainly automobile and tractor ones. On its basis, it became possible to combine turning, predominantly hard turning, for difficult-to-cut steels and alloys with a hardness of over 45HRC, with abrasive processing, also for the first time in the world, carried out in 1998 by the same company Emag, but already together with the company Reinecker, which was part of it, on a machine Maud. VSC250DS (Fig. 1).

When the benefits are obvious

Since then, the advantages of this arrangement have become apparent to many other German, Swiss and Italian companies producing both lathes and grinding machines. For turning centers, they consist in the possibility of using dry and hard turning, and in some cases, grinding in one setup parts of small diameter (up to 400 mm, only the G 250 machine from Index has a processing diameter of 590 mm), but of a fairly large length. There are many such parts such as gears and various disks found in the automotive industry.
In addition, processing productivity is increased, since the allowance for grinding after turning can be increased to several hundredths of a millimeter (in reality it usually reaches several tenths), and its accuracy, which is ultimately determined by grinding. To date, such combined machines are produced by several companies, mainly German, whose main field of activity is, as shown in Table 1, the production of not only turning centers (Emag, Index, Weisser), but also grinding machines (Junker, Buderus Schleifmaschinen, Schaudt Mikrosa BWF). Their cost varies widely and is determined, first of all, by the layout, design and configuration.

The EMO 2003 exhibition showed that interest in combined machines for hard turning and grinding is growing. Along with the companies Emag, Index, Weisser, Buderus, Schaudt Mikrosa BWF, which previously exhibited machines for combined turning and grinding, similar products were demonstrated by other manufacturers of machine tool equipment. For example, the Tacchella company (Italy) showed a prototype of the Concept cylindrical grinding machine, equipped with an 8-position turret with fixed tools (Fig. 2), and the Meccanodora company (Italy) showed a serial Futura machine for hard turning and milling, as well as external and internal grinding transmission parts. The Stratos M, first shown by Schaudt Mikrosa BWF at the EMO 2001 exhibition, was additionally equipped with an 8-position turret.

Combined processing

For parts passing through a turning-grinding center, for example, electric motor shafts, in most cases it is not necessary to grind all surfaces - mainly only the supporting ones or the most worn ones. For the rest, turning is quite enough. IN similar cases, when tight dimensional tolerances and high quality surfaces are needed only in certain areas of the part; the use of lathes with grinding capabilities is fully justified, especially since processing on them occurs in one setup. If the workpiece has many steps, most of which is subject to grinding, it must be processed on a grinding machine with the ability to turn.

Thus, processing is carried out on a grinding machine if:

• the workpieces are made of materials that are difficult to machine, not amenable to or difficult to turn;
• the required tolerances exceed those achievable during turning;
• the required surface quality is so high that it cannot be achieved during turning, including hard turning.

A lathe is used for processing when:

• the complex geometry of the workpiece makes processing with a blade tool with a point cutting edge (for example, a cutter) more effective than with a relatively wide grinding wheel;
• the volume of material removed is relatively large and exceeds the capabilities of removal by grinding;
• processing of discontinuous surfaces is necessary.

Many parts have both requirements, so combining grinding with hard turning on one machine increases its flexibility and allows each operation to be optimized.

Design features of the machines

An analysis of the machines presented in Table 1 shows that the vast majority of them have a vertical layout, which for relatively short parts (with a diameter greater than the length), usually subjected to turning and grinding, turned out to be more effective than a horizontal one. Processing of fairly long shafts (from 600 mm for the Emag HSC250DS model to 1400 mm for the Index G250 model) remains an exception and is carried out only on horizontal machines. In addition, most machines, in order to increase their efficiency, are equipped with conveyors for feeding workpieces and removing finished parts from the working area. One of the means of increasing the rigidity of machines subjected to increased loads during combined processing is the use (for machines from Emag, Schaudt BWF Mikrosa and some others) of polymer concrete frames that have good damping properties, as well as (for machines from Buderus) frames made of natural granite.

Almost all machines are equipped as standard with more than one grinding spindle in order to be able to carry out both external and internal machining. In this case, the straightening mechanism is built directly into the machine. Note that almost all companies offer linear motors as options, not only along the longitudinal axis, along which maximum movement occurs, but also along the transverse one. This means that the productivity of such machines can be further improved.

Of course, lathe manufacturers such as Emag and Index and grinding machine manufacturers such as Junker, with the common goal of providing high flexibility, productivity and machining efficiency when choosing an approach to the design of their equipment that combines hard turning with grinding or vice versa - are guided by various considerations. As a rule, this design is made in such a way that the machine, in addition to turning and grinding, has the ability to perform other operations, if necessary.
So, the machine mod. Index's V300 has an inverted vertical spindle design (inspired by Emag) and is designed to handle a wide range of workpieces of any type (castings, forgings, etc.). Their loading and unloading is done automatically. Thanks to the modular design, the machine, which is equipped with a large number of tool heads and blocks that can be combined in any order (Fig. 3), designed to perform various operations of turning, drilling and grinding, can work in both small- and medium-scale production. During the processing process, the spindle moves the workpiece, bringing it to various tool blocks installed on the bed, which carry out the specified operations of turning, drilling, external and internal grinding. To perform combined hard turning and grinding, a turret with stationary and rotating tools is mounted on the frame. The external grinding unit uses grinding wheels with a diameter of 400 mm and a width of 40 mm from traditional and superhard materials, for example, CBN, rotating at a frequency of up to 6000 rpm from a 7.5 kW drive. They are edited automatically. The unit has a built-in electromagnetic grinding wheel balancing system. Internal grinding is carried out with wheels made of the same materials, but mounted on mandrels with a HSK32 cone to obtain maximum precision and rigidity of the grinding spindle. The high-frequency spindle for their rotation has a power of 2 to 15 kW and is designed for a rotation speed in the range of 45,000-100,000 rpm. Additional operations on this machine can be performed using a diode laser built into manufacturing process to perform hardening of the outer surfaces, as well as the ends and individual sections on the workpiece clamped in the spindle chuck internal surfaces. An additional operation is also rolling, performed on a mod machine. CNC 435 from Buderus.
Multifunctional machines—the most successful type of blade machining equipment currently in many respects—are not particularly new to the abrasive industry. Using grinding wheels, built-in, for example, into the magazines of some milling machining centers, semi-finishing and finishing machining of complex surfaces of parts made of difficult-to-machine materials, such as turbine blades, has long been performed. The main technological advantages of such centers are the reduction in the number necessary equipment and, accordingly, the required production space and the number of operators, the possibility of transferring finished parts directly to assembly - are also preserved for multifunctional grinding-based machines. However, this equipment for combined grinding and turning has a number of differences and advantages. It should be noted, in particular, the significant predominance of grinding operations over turning, milling and drilling, the mandatory cooling of the working area, and the presence in some cases of a wheel changing mechanism during grinding. It is also necessary to consider as an advantage that when performing lathe, milling, thread-cutting and other blade operations on grinding machines, greater accuracy is achieved than when performing them on lathes and/or milling machines, because grinding machines that are converted into multifunctional ones initially have more higher accuracy than, for example, in turning machines, which are given the ability to grind. Such machines are produced by the Swiss company Magerle and the German company Junker.
The modular MMS machine (Fig. 4), first shown by Magerle at the EMO2003 exhibition, has a symmetrical portal design, which, together with ball screws along the coordinate axes, ensures its static and dynamic rigidity and thermal stability. Movements along three coordinate axes (500x250x200 mm) through these gears are performed by the table, which allows you to install horizontal, vertical or inclined grinding heads on the machine and manually or automatically load it from four sides. At the exhibition, in particular, a version of the machine was shown with a vertical motor spindle with a power of 30 kW and a built-in tool changer (five grinding wheels with a diameter of 300 mm, a width of 60 mm and a weight of no more than 20 kg, or 20 wheels with a diameter of no more than 130 mm), produced in 3 seconds. The rotation speed of the circles is recommended within 1000-8000 min -1. The HSK-A-100 spindle cone can also accommodate cutters, drills and other blade tools, which, when combined with a two-axis dividing head and a satellite changer, allows the processing of small pump blades, turbine blades and other complex parts. This is facilitated by the ability to supply coolant through the center of the spindle at a pressure of 80 bar.
A prototype of the Concept multifunctional machine, which was also shown for the first time at this exhibition by the Italian company Tacchella Macchine, is a combination of a conventional cylindrical grinding machine with an eight-position turret in which stationary tools are installed. Two large-diameter circles made of CBN are rotated on the machine 180 degrees relative to each other and can be rotated in turn into the working area. The machine bed is made in the form of a rigid ribbed cast iron casting. Movements along the X and Z axes can be performed using linear motors or ball screws. Hydrostatic guides are used to move the working parts. The disadvantages of this machine include the fact that it does not have separate working areas for turning and grinding. In the future, apparently, rotating tools will also be installed in the turret, which will expand the technological capabilities of the machine, and the number of turrets can be increased to two.
On the Hardpoint 300 series machine of modular design from Junker with an inclined bed, hardened and non-hardened parts such as rotation bodies with a diameter of 80 mm and the same length (Fig. 5) in addition to grinding and honing with wheels and CBN heads can be used for turning, drilling and reaming in one setup , as well as cutting threads and removing burrs. The machine is implemented in four versions with a number of spindles from two to four, in which up to four parts can be processed simultaneously with or without transmission from one spindle to another. The machine is controlled along six coordinate axes from the Sinumerik 840D CNC device. The machine can be loaded manually or automatically.

High performance machine mod. CNC235 from Buderus Scheiftechnik (Fig. 6) is achieved by installing two spindles on it, allowing external and internal grinding (with special heads) and hard turning (with separate cutters or a turret) of workpieces with a diameter and length of up to 150 mm, as well as a belt conveyor.

Multifunctional machines designed for hard turning and grinding of heat-treated workpieces are widely used high demand among consumers abroad and are gradually beginning to penetrate into Russia. There is information about the installation of one such machine (by Buderus) at the Volgoburmash plant. Two machines mod. Stratos M was delivered to VAZ in 2004. At the same time, 60 such machines are already operating in Europe, the USA and Southeast Asia. The reason for such a sharp difference lies in the insufficient level of development of most branches of our industry and the insufficient efficiency of such complex and expensive equipment in our economic conditions, and, consequently, the minimum demand for it. Therefore, in the near future one should not expect the appearance of a large number of machines for dry turning and grinding at Russian factories, except perhaps at individual enterprises in the automotive industry and several enterprises producing equipment for the oil and gas industry.

Vladimir Potapov
Magazine "Equipment: market, supply, prices", No. 07, July 2004.

Modern trends in the integration of combined machining have meant that grinding can also be carried out on lathes. When quality problems come to the fore, attention is always paid to the finishing process, which is called grinding - performing mechanical action in several passes to reduce initial errors. It is impossible to carry out finishing using a turning tool with the same quality as when using grinding heads due to the rounding of the cutting edge. Also, do not forget that vibration may occur on a lathe at small feeds, which will lead to errors. For this reason, even with the emergence of new materials that can withstand heavy impact for a long time and not change their shape, grinding remains the main method used to obtain a surface of a high class of roughness.

Requirement for grinding heads

The production of rotating bodies on lathes has been carried out over the past several decades. As a rule, grinding was carried out using other equipment. This moment was determined by the following technological process:

1. performing rough turning to remove a large layer of metal;
2. performing fine turning to prepare the part for the finishing stage of the technological process;
3. finishing on a cylindrical grinding machine.

Such a technological process determines an increase in costs due to the installation of a special machine for finishing processing. When creating a large batch of products, purchasing a grinding machine pays off, but when small-scale production its purchase will lead to an increase in the cost of one product. A way out of the situation is the use of special grinding heads, which can also be used to obtain a surface with a high roughness class.

Design Features

Grinding heads are a special design that is used to significantly expand the capabilities of a turning group machine. This mechanism conventionally refers to equipment. TO design features can be attributed:

1. the presence of its own electric motor, the power of which can be from 1 kW or more. This point determines that the head can become equipment for various models of lathes. as a rule, turning equipment has a closed gearbox and does not have a separate drive for connecting the equipment in question;
2. the installed electric motor is connected to the lathe circuit, which determines the versatility of the entire structure. there is also a three-phase plug for inclusion in a separate power circuit;
3. the head has its own frame, which, during modernization, can be rigidly attached instead of a standard tool holder. this moment determines what the equipment allows you to receive quality surfaces with high mechanization of the process. steel is used in the manufacture of the frame, which helps prevent vibration during operation by increasing the rigidity of the structure;
4. rotation is transmitted using a belt drive to reduce speed.

The design is quite simple. When considering it, it is worth paying attention to the type of frame. This is due to the fact that only a certain type of bed can be used instead of a tool holder for a certain model of lathe.

Using the equipment in question, steel and cast iron can undergo finishing on a lathe. In this case, it is possible to achieve the same roughness index as when using cylindrical grinding equipment. Model 200 differs from the considered power of the installed electric motor and the maximum diametrical dimensions of the installed circles. Similarly, the cost of producing parts can be reduced by increasing the versatility of the equipment used. At the same time, we note that the equipment is suitable for old and new turning equipment, as it has universal application.

You may also be interested in the following articles:

Checking lathes for geometric and technological accuracy
Preparing the foundation for lathes Dividing heads for milling machines

Lathes, according to their functionality, can be divided into types: according to groups, and features of application.

1. Lathe-screw-cutting group. Equipped with additional equipment for drilling and cutting various threads. This machine allows you to shape parts into cones, cylinders and make complex combinations of these and other shapes. You can also use it to: drill and ream holes, make boring, countersink holes, cut threads, both internal and external.

2. Turning and milling machines are universal equipment; they make it possible to work with any material: plastic, iron, wood, etc. Functionality of work: turning, drilling holes, including deep ones, milling.

An excellent solution from PROMA will be a universal tabletop metal lathe. Suitable if production requires a small amount of turning work without compliance high levels accuracy, or for home use.

The equipment allows you to perform the following types of operations:

• workpiece end processing;
• countersink;
• drill and ream holes;
• cut the thread.

A universal CNC lathe is used in mass production enterprises. Multi-purpose lathes have the maximum functionality among such machines. It allows you to perform an expanded range of work in addition to turning. With its help you can drill and mill after completion primary processing blanks.

A given shape is given to the workpiece using a processing tool, in particular a cutter fixed in a tool holder. When it moves along a rotating workpiece perpendicularly or at a given angle, layers of metal of the required thickness are ground down. This operation gives the part a new shape.

Buy metal lathes

A universal metal lathe is designed to shape workpieces made from a variety of materials. They allow you to do the following:

• cut;
• sharpen;
• cut threads;
• bore holes;
• perform deep drilling.

Processing of a workpiece on a lathe is carried out with its constant rotation.

The presence of a tool holder in the design of a lathe is the main difference between a machine for metal processing. The main task of this device is to hold the processing tool while working with metal.

The PROMA company provides a catalog of screw-cutting lathes of European quality on its website. Here you will find machines for home and industrial use.