Currently, a lathe is widely known. The history of its creation begins in the 700s. The first models were used for wood processing, 3 centuries later, an aggregate for working with metals was created.
First mention
In the 700s A.D. an assembly was created, partially resembling a modern lathe. The story of its first successful launch begins with the processing of wood by rotation of the workpiece. Not a single detail of the installation was made of metal. Therefore, the reliability of such devices is rather low.
At that time, a lathe had a low efficiency. The history of production is restored according to the surviving drawings, drawings. To unwind the workpiece required 2 strong apprentices. The accuracy of the products is low.
The history dates back to remotely resembling a lathe, history dates back to 650 BC. e. However, the general principle of these machines was only the processing principle - the rotation method. The remaining nodes were primitive. The workpiece was literally set in motion by hand. Used slave labor.
The created models in the 12th century already had a semblance of a drive and could receive a full-fledged product on them. However, there were no tool holders yet. Therefore, it was too early to talk about the high accuracy of the product.
The device of the first models
An old lathe clamped the workpiece between the centers. The rotation was carried out by hands only a few turns. A stationary tool was cut. A similar processing principle is present in modern models.
As a drive for the rotation of the workpiece, the craftsmen used: animals, a bow with arrows tied with a rope to the product. Some craftsmen for these purposes built a semblance of a water mill. But it did not work out to significantly increase productivity.
The first lathe had wooden parts, and with the increase in the number of nodes, the reliability of the device was lost. Water devices quickly lost relevance due to the complexity of the repair. Only by the 14th century did the simplest drive appear, which greatly simplified the processing process.
Early drive gears
Several centuries have passed since the invention of the lathe until the implementation of the simplest drive mechanism on it. You can imagine it in the form of a pole fixed in the middle on the bed over the workpiece. One end of the eyeglass is tied with a rope that is wrapped around the workpiece. The second is fixed with a foot pedal.
This mechanism worked successfully, but could not give the necessary performance. The principle of operation was built on the laws of elastic deformation. When the pedal was depressed, the rope was tensioned, the pole bent and experienced significant tension. The latter was transmitted to the workpiece, setting it in motion.
Having turned the product 1 or 2 turns, the pole was released and bent again. With the pedal, the master regulated the continuous operation of the ochep, forcing the workpiece to rotate continuously. At the same time, the hands were occupied with the tool, performing wood processing.
The following versions of machines that already had a crank mechanism inherited this simplest mechanism. A similar drive design was subsequently produced by mechanical sewing machines of the 20th century. On lathes with a crank, they achieved uniform movement in one direction.
Due to the uniform movement of the master began to receive products of the correct cylindrical shape. The only thing missing was the rigidity of the nodes: centers, tool holders, drive mechanism. Cutter holders were made of wood, which led to their extraction during processing.
But, despite these shortcomings, it became possible to produce even spherical parts. Metal processing was still a difficult process. Even soft alloys by rotation did not yield to real turning.
A positive development in the design of machines was the introduction of versatility in processing: machining of workpieces of various diameters and lengths was already carried out on one machine. This has been achieved by adjustable holders and centers. However, large parts required significant physical costs for the master to implement the rotation.
Many craftsmen adapted a flywheel made of cast iron and other heavy materials. The use of inertia and gravity facilitated the work of the processor. However, it was still difficult to achieve industrial proportions.
Metal parts
The main task of the inventors of machine tools was to increase the rigidity of the nodes. The beginning of technical re-equipment was the use of metal centers clamping the workpiece. Later, gears from steel parts have already been introduced.
Metal parts made it possible to create screw cutting machines. Rigidity was already enough for processing soft metals. Gradually improved individual nodes:
- a workpiece holder, later called the main unit - the spindle;
- conical stops were equipped with adjustable mechanisms for changing the position along the length;
- working on a lathe became easier with the invention of a metal tool holder, but constant chip removal was required while increasing productivity;
- a cast-iron bed increased the rigidity of the structure, which made it possible to process parts of considerable length.
With the introduction of metal nodes to untwist the workpiece becomes more difficult. The inventors thought about creating a full drive, wanting to exclude human manual labor. The transmission system helped to implement the plan. The steam engine was first adapted for rotating workpieces. It was preceded by a water engine.
The uniformity of movement of the cutting tool was carried out by a worm gear using the handle. Thanks to this, a cleaner surface of the part was obtained. Replaceable blocks allowed to realize universal work on a lathe. Mechanized designs have been refined for centuries. But to this day, the principle of operation of the nodes is based on the first inventions.
Scientist inventors
At the moment, buying a lathe, technical specifications are analyzed first. They provide basic processing capabilities, dimensions, rigidity, and production speed. Earlier, with the modernization of the nodes, parameters were gradually introduced according to which the models were compared among themselves.
The classification of machines helped to assess the degree of perfection of a particular machine. After analyzing the collected data, Andrei Nartov, a domestic inventor from the time of Peter the Great, upgraded previous models. His brainchild was a real mechanized machine that allows you to make various types of treatments for bodies of revolution, cut threads.
A plus in the design of Nartov was the ability to change the speed of rotation of the moving center. They also provided for replaceable gear blocks. The appearance of the machine and the device resemble the modern simple lathe TV3, 4, 6. Modern processing centers also have similar nodes.
In the 18th century, Andrei Nartov introduced the world to a self-propelled caliper. The lead screw transmitted uniform tool movement. Henry Maudsley, an English inventor, introduced his version of an important site by the end of the century. In its design, the change in the speed of movement of the axes was carried out due to the different pitch of the lead screw thread.
Main nodes
Lathes are ideal for machining 3D parts by rotational cutting. Overview of a modern machine contains the parameters and characteristics of the main components:
- Bed - the main loaded element, the frame of the machine. They are made of strong and hard alloys, perlite is mainly used.
- Caliper - an island for mounting rotating tool heads or a static tool.
- Spindle - acts as a holder of blanks. The main powerful rotation unit.
- Additional nodes: ballscrews, sliding axes, lubrication mechanisms, coolant supply, air samplers from the working area, coolers.
A modern lathe contains drive systems consisting of complex control electronics and an engine more often synchronous. Additional options allow you to remove chips from the working area, measure the tool, apply coolant under pressure directly to the cutting area. The mechanics of the machine are selected individually for the tasks of production, the cost of equipment also depends on this.
The caliper contains units for locating bearings that are mounted on a ball screw (ball screw pair). Also, elements are mounted on it for contact with sliding guides. Lubrication in modern machines is automatically supplied, its level in the tank is controlled.
In the first lathes, a person moved the tool, he chose the direction of his movement. In modern models, all the manipulations are carried out by the controller. It took several centuries to invent such a site. Electronics has greatly expanded processing capabilities.
Control
Recently, CNC lathes for metal are widely used - with number-program control. The controller controls the cutting process, tracks the position of the axes, calculates the movement according to the parameters laid down. The memory stores several stages of the cut, up to the release of the finished part.
CNC metal lathes can have a visualization of the process, which helps to check the written program before the tool starts moving. The whole cut can be seen virtually and correct code errors in time. Modern electronics control the axle load. The latest software versions allow you to identify a broken tool.
The methodology for controlling broken plates on the holder is based on a comparison of the axle load schedule during normal operation and when the emergency threshold is exceeded. Tracking occurs in the program. Information for analysis to the controller is provided by the drive system or power sensor with the ability to digitize values.
Position sensors
The first machines with electronics had limit switches with microswitches to control extreme positions. Later, encoders began to be installed on the screw couple. At present, high-precision rulers are used that can measure a backlash of several microns.
Equipped with circular sensors and axis of rotation. The spindle assembly could be controllable. This is required to implement the milling functions that were performed by the drive tool. The latter was often built into the turret.
Measurement of the integrity of the instrument is carried out using electronic probes. They also facilitate the work of finding snap points to start the cutting cycle. Probes can measure the geometry of the resulting contours of the part after processing and automatically make corrections that are laid down in the repeated finishing.
The simplest modern model
The TV 4 lathe belongs to educational models with the simplest drive mechanism. All control is carried out manually.
Handles:
- adjust the position of the tool relative to the axis of rotation;
- set the direction of threading right or left;
- serve to change the speed of the main drive;
- determine the pitch of the thread;
- include longitudinal movement of the tool;
- responsible for fastening nodes: tailstock and its pintles, heads with incisors.
Flywheels move the nodes:
- quill of the tailstock;
- longitudinal carriage.
The design provides a lighting circuit for the working area. A safety system in the form of a protective screen protects workers from chips. The design of the machine is compact, which allows it to be used in classrooms, service rooms.
The TB4 screw-cutting lathe belongs to simple designs, where all the necessary nodes of a full-fledged metal processing design are provided. The spindle is driven through the gearbox. The tool is mounted on a caliper with a mechanical feed, driven by a screw pair.
Dimensions
The spindle is controlled by an induction motor. The maximum size of the workpiece may be in diameter:
- no more than 125 mm if to carry out processing over a support;
- no more than 200 mm if processing is carried out over a bed.
The length of the workpiece clamped in the centers is not more than 350 mm. The assembly machine weighs 280 kg, the maximum spindle speed of 710 rpm. This rotational speed is critical in finishing. Power is supplied from a 220V network with a frequency of 50 Hz.
Model Features
The gearbox of the TB4 machine is connected to the spindle motor by a V-belt drive. On the spindle, rotation is transmitted from the box through a series of gears. The direction of rotation of the workpiece is easily changed by phasing the main engine.
The guitar is used to transmit rotation from the spindle to the calipers. It is possible to switch 3 feed rates. Accordingly, three different types of metric threads are cut. The smoothness and uniformity of the stroke is ensured by the lead screw.
The handles specify the direction of rotation of the headstock screw pair. The handles also set the feedrate. The caliper runs only in the longitudinal direction. Units should be lubricated according to the regulations of the machine manually. Gears take grease from the bath in which they work.
The machine has the ability to work manually. For this, flywheels are used. There is a gearing of a rack gear and a gear rack. The latter is bolted to the bed. This design allows you to include manual control of the machine if necessary. A similar flywheel is used to move the tailstock pintles.