Receiving device of a rough wire drawing mill. Drawing mills: types, types, technical characteristics, operating features and application in industry. Features when drawing copper wire
Drawing machines are designed for the production of smaller diameter wire from wire rod (rough drawing) or from larger diameter wire.
Approximate drawing ranges:
- Rough drawing: the input diameter in such machines is 8 mm for copper and 12-9.5 for aluminum, the output diameter is from 4 mm to 1.2 mm.
- Average drawing: input diameter 2.5mm - 3.5mm, output diameter from 1.5mm - 0.2mm.
- Fine drawing: input diameter, 2.5mm - 1.5mm, output 0.5mm - 0.05mm.
Decide on the receiving device. The wire can be placed in baskets or wound on bobbins. It can be wound onto bobbins using either a simple single receiver or a double automatic receiver (for high-speed ones), which allows you to change bobbins without stopping the mill.
It should be remembered that the drawing process requires continuous lubrication using an emulsion. To do this, it is necessary to build an oil station, which includes pumps, an emulsion reservoir and, depending on the region, additional cooling devices, such as radiators or cooling towers.
The emulsion filtration system should not be neglected. This system is especially important in the case of further wire drawing, since copper microparticles that enter the die along with the emulsion at the time of drawing are pressed into the wire and become the point of rupture during the next stage of drawing.
In addition, the drawing line must be equipped with additional machines and equipment, such as a sharpening machine, a cold and/or hot welding machine. This also includes dies (dies), the set depends on what output diameter is needed. The main indicators of product quality (wire/core) are resistance and elongation factor.
If you plan to sell products after drawing, then you may need laboratory equipment to measure these indicators, and if the kit for measuring resistance is not expensive, then for measuring elongation this is expensive equipment, especially for large diameters.
If you plan to use the resulting products yourself, then you can get by with a simple tester for measuring resistance, and elongation can be measured by building a simple device for stretching the wire.
Rough drawing is an energy-intensive process, coupled with annealing, high-speed lines consume about 300 kW/h. As a rule, 2 operators work on such lines. Electricity consumption for average drawing is about 100 kW, for thin drawing about 50 kW.
Cold or hot metal drawing is a type of metal forming. Using these methods, an assortment of round and shaped wires, rods, pipes and other products made of ferrous, non-ferrous metals and alloys are produced that are sold in the retail chain. For this purpose, drawing equipment is used, which, according to the kinematic principle, makes it possible to obtain products of the required diameter using single and multiple drawing methods. Twisted fittings, wire, metal ropes, mesh and fasteners are obtained from products made by drawing, where a drawing machine or machine is used. Products obtained by drawing are used in various industries, agriculture and by home craftsmen.
The essence of the drawing process is to pull a metal workpiece of a larger diameter through a hole of the required shape and obtain a product of a smaller diameter. Manufactured products are characterized by the quality of the outer surface, density and accuracy of cross-sectional dimensions. Operations are performed on special machines called drawing mills. They increase labor productivity: the labor intensity of manufacturing becomes much lower than when producing such products by other methods.
Drawing mills are produced by manufacturers with rectilinear movement of the workpiece and with winding on drums. In the latter case, they can be with one or more driving drums, which allows one or several workpieces to be drawn at the same time.
Types and methods of drawing
Drawing is performed on a drawing mill. Structurally, the device consists of the following main parts: a die (die), mandrels of various designs, broaching and auxiliary devices for automation and mechanization of the process. In this case, the drawing machine of a rectilinear design is distinguished according to the principle of operation of the main motor of continuous action (track), hydraulic, chain and rope.
The process is classified according to the following parameters:
- by type (wet, dry);
- heating the workpiece (cold, hot);
- number of drawn workpieces (1, 2, 4, 8);
- degree of purity of the resulting product (rough, finishing);
- mobility of the drag (stationary, movable);
- number of transitions (single and multiple);
- method of traction (hydraulic, drum, chain).
The variety of parameters has given rise to a huge number of manufactured units, differing in technical characteristics, work technology and productivity.
Drawing is used to produce pipes with a diameter of 0.3÷500 mm with a wall thickness of 0.05÷6 mm. In this case, manufacturing methods can be as follows:
- draft;
- profiling method;
- hydrodynamic friction;
- on a special mandrel (fixed short, long movable, floating);
- on a deformable core;
- with distribution of a pipe-shaped workpiece.
The method, and therefore the equipment for it, is chosen depending on the requirements for the finished product and the brand of the workpiece used. Pipes are manufactured using a chain and drum drawing mill. In the latter case, drawing is called coil drawing.
Main stages of the process
The final product obtained by drawing is subject to certain requirements, which are indicated in the technological characteristics. The workpiece goes through certain stages that affect the final result. They are as follows:
- annealing of the workpiece to obtain a fine-grained structure and increase plastic properties;
- removing scale from the workpiece surface;
- washing the workpiece after etching in a sulfuric acid solution;
- applying a special layer, the composition of which depends on the material of the workpiece;
- drawing on the mill;
- elimination of hardening;
- finalization of the resulting products (trimming to the required length, finishing the ends).
As a rule, they affect the density, hardness, fluidity, electrical resistance of the material (increase), plastic, anti-corrosion properties (decreases). This manifestation, called cold hardening, is eliminated by heat treatment - normalization, patenting, tempering, annealing. The choice of method depends on the grade of metal or alloy and the conditions of the drawing process.
Equipment and machines for drawing
A drawing machine with a direct or alternating current drive can be used for single or multiple drawing. In the latter case, the metal workpiece passes through several dies, changing its profile or diameter downward sequentially. The single-shot drawing machine is used for workpieces with a diameter of 8 to 20 mm. From a special unwinding device, the workpiece, after passing through the die, is wound onto a drum whose diameter does not exceed 750 mm. All operations on such a device are automated: the drum is served by a lift, and the stacking of workpieces is done by a hoist. Such drawing machines are used for the production of wire shaped profiles from ordinary and difficult-to-deform grades of workpieces during the operation of wire sizing.
Drum and chain mills differ in the way they are wound. For drum devices, the winding of manufactured products is carried out on a special turntable; for chain devices, it cannot be wound.
In the video you can clearly see the wire making process:
Wire drawing is a relatively simple technological process that includes several different procedures.
1
Drawing is a process in which the workpiece is pulled through a tapering hole using special equipment. The initial workpiece can be copper, steel, aluminum. The tool in which the hole is made is called a die, and the hole itself, on the configuration of which the shape of the profile being made depends, is called a die.
The drawing method, compared to rolling, ensures many times greater cleanliness and precision of the surface of the wire, as well as various profiles, rods, and pipes. In addition, the drawn metal is characterized by a change (for the better) in mechanical parameters, which is due to the strengthening (removal of hardening) of the finished products. Drawing is actively used in the production of shaped, very precise profiles of pipes of different diameters, wire with a cross-section from 1–2 microns to 10 (and sometimes more) millimeters.
Electrochemical cleaning is an electrolytic type of etching. It can be cathodic and anodic, and the second method is considered more effective and safe. In this case, the anode is the workpiece being cleaned, and the cathode is copper, iron or lead. Cathodic etching is more dangerous, since it involves active release of hydrogen and poorly controlled separation of scale, which leads to the formation of so-called “etching brittleness.”
After removing scale using chemical reagents, the workpiece should be thoroughly washed. This allows you to get rid of iron salts, dirt, sludge, residual etching elements and acid solution. If washing is not carried out immediately after chemical treatment, all of these components will dry out. Let's add - washing is done first in hot water, and then under a pressure of about 700 Pa in cold water.
5
The drawing process in the production of copper wire is based on the use of cast blanks. They are first fused and then hot rolled. This process causes a film of oxides to appear on the wire rod. To remove it, the workpiece is treated with dilute acid, and only after that drawing is performed.
Copper wire is also produced using submersible molding technology. In this case, the surface of the wire rod is clean. In this way, the thinnest products (about 10 micrometers) are made. But when performing submersible molding, it is necessary to choose the right lubricant compositions that have high quality and special properties. These include the following lubricants: 
- complex solutions: nonionic surfactants, salts (alkaline) of sulfonated fatty oils, alkaline additives;
- emulsions: anti-foam, anionic, stabilizing compounds, synthetic esters, natural fatty and mineral hydrocarbon oil compositions;
- synthetic substances: salts (inorganic and organic), polymer solutions.
To process metal by drawing, machines are used, on which the drawing technology itself is carried out. With the help of this equipment, metal blanks are processed, which consists of pulling them through holes. The dimensions of these holes are significantly smaller than the dimensions of the workpieces, i.e. their sections. The workpieces are crimped; due to their crimping, their shape and cross-section change, which leads to an increase in their length. See fig. 1.
Metal processing This method for the production of parts with round and shaped sections has a number of positive characteristics:
- high profile accuracy;
- surface cleanliness.
And during production cold drawing method There are also additional advantages:
- increase in yield strength;
- strength;
- hardness of the drawn workpiece.
Many areas of industry and national economy widely use drawing products.
Drawing methods used:
- upon receipt of wire with a minimum diameter of 5 microns;
- for the production of thin pipes, pipes with a diameter of max. 400 mm.
Modern machines for processing metal parts by drawing are quite advanced. They are today:
- with increased productivity;
- good surface quality of the manufactured product;
- with increased die resistance;
- with improved safety conditions.
Good control and measuring technology makes it possible to accurately carry out drawing processes, which are already largely automated.
High tenacity dies enable significant increases in speed to be achieved and wire drawing beyond the fine diameter. Very stringent requirements are placed on the accuracy of wire diameter dimensions.
Devices of various designs are used to process workpieces by broaching. And there are two types of drawing machines.
Functional device The drawing device determines the purpose of the drawing mills. There are mills where the material is pulled in a straight line. This:
- chain,
- mills equipped with caterpillar traction,
- with reciprocating moving carriages,
- rack and pinion,
- hydraulic.
There are mills with a drum designed for winding the processed metal.
The purpose of mills with the movement of material being processed in a straight line:
- for drawing rods,
- pipe drawing,
- other products that are not wound into bundles.
Purpose of mills with winding material into coils:
- wire drawing with a special profile,
- drawing pipes with a minimum diameter.
They are characterized by the number of drums, the principle of their operation and are divided into:
- one-time;
- multiple, with sliding function;
- multiple, without sliding function;
- multiple, with reverse tension.
The name of single-pass drawing mills speaks for itself: the drawing process is performed in one pass. On multiple mills - in several passes.
Modern units for the production of steel wire by drawing are entire complex lines, which include equipment that ensures the execution of operations for the production of wire from various materials: low-carbon, high-carbon or alloy steels. The drawn material, which will be drawn, undergoes a series of technological preparatory operations or heat treatment. This is due to the future purpose of the wire.
The wire must be properly prepared for drawing. It must be pickled, maybe with a protective coating, subjected to hot and cold washing and drying.
After the above procedures for preparing for drawing, the wire is transferred to the drawing section of the production. Depending on the purpose of use, the wire after drawing is either heat-treated, oiled, tied or packaged. In case of partial use of wire by the same enterprise, it is transferred to the appropriate workshops or departments. It is transmitted on large reels or reels.
Auxiliary equipment
Each unit is equipped with main and auxiliary equipment. The main equipment performs the drawing operation.
Auxiliary equipment:
- unwinders,
- winders,
- devices for sharpening wire,
- lubrication equipment,
- packaging equipment for bundles,
- for cutting wire,
- for welding wire, etc.
One type of drawing mill, which we mentioned above, has a drum for winding the material. The number of passes during the drawing process and the type of mill do not change the basic equipment of the drawing mill. It includes: pulling drum, gearbox, electric motor.
Steel wire drawing equipment is different from non-ferrous wire drawing equipment. But the line between these types of equipment is blurring today. The process technology itself determines the specific requirements for the designs of drawing equipment and its main characteristics.
Drawing equipment can be either universal or standardized. In production areas with large capacities and a narrow assortment, specialized equipment is usually used, while in the production of a wide assortment it is advisable to use universal equipment.
Non-ferrous metal (copper, aluminum) has less strength than steel. This characteristic is the most decisive when choosing the main parameters of a drawing mill and its design.
For the process of drawing wire from soft materials, for example, non-ferrous metal, drawing machines with a sliding function are used. This is due to the fact that when sliding a wire made of a soft material, friction losses are less than when drawing a steel material. The increased ductility and lower strength of non-ferrous metal in any case makes it easier to fill the mill. In the production of steel wire, mills with a sliding function are used less frequently, mainly in the production of thin wire of minimum diameter and wire for special applications.
Single-pass drawing mills produce thick wire of various profiles and round sections, with a diameter of 25-40 mm, pipes made of ferrous and, to a greater extent, non-ferrous metals. When drawing large-diameter pipes, drums of also large diameter are used. The larger the diameter of the pipe, the larger the diameter of the drum chosen.
The workpieces are placed on the drum in only one row, which reduces the mass of the riot. The die moves along the drum, the material is wound without moving the turns along the drum. In this way, the surface and profile of the coils are protected from damage. Rice. 2 shows a mill with a moving die.
Single-shot drawing machines are designed for a force of 0.05-200 kN. This is determined by the characteristics of the material being drawn: cross-section, profile, quality. The drawing speed reaches 5 m/sec.
In single-shot mills, productivity increases due to an increase in the mass of revolts. This occurs both on the unwinding side of the source material and on the winding side of the finished wire. The larger the diameter of the wire being drawn, the greater the weight of the coils, which can be increased by welding.
A single drawing machine with all auxiliary components is shown in Fig. 3.
Gearbox 1, gearbox 2, electric motor 3, unwinding figure 4, sharpening device 5, lift 6 and rack 7.
Receiving devices are used to transfer the wire to subsequent operations. The mill stops only when the receiving devices are changed, which occurs at the moment it is filled. This is a fairly quick procedure. For coils with a large mass of up to 3 tons, special receiving devices are used. The sequentially fed coils are transferred to drawing without stopping the mill, without reducing its speed.
Motors on single-shot drawing mills can be of both direct and alternating current. They must ensure the operation of the mill at creeping speed, smooth start-up of the unit, jog operation, speed control during drawing, and the possibility of emergency stop.
2. Double drawing mills
Double drawing machines perform the drawing process in two passes, in other words, when two broaches are enough. This is necessary to ensure a given wire size or when production volumes are small. With two broaches, the material is subjected to fourfold compression.
The simplest version of such a mill is to use a two-stage drum. At the first stage, the drum has a smaller diameter, which ensures the sliding of the wire. Different wear of the rolls makes it possible to install the hood 1-2% higher than the hood due to the difference in the diameters of the steps.
Sliding occurs at the bottom step, otherwise the wire may break. There is no possibility to give high compressions here.
Differential double drawing machines operate on both stages without slipping, but allow high as well as low reductions. We see a differential mill operating on the principle of double drawing in Fig. 4. It has two drawing drums located on the same axis.
3. Multiple stuns
Multiple drawing mills are equipment in which the workpiece is drawn through several dies simultaneously. This is done in order to increase the extraction of the processed material. The dies are located one after another in series.
To determine the drawing ratio, the dimensions of the material being processed, its cross-section, the specified size of the final product and its mechanical properties are essential. Usually the multiplicity is set in the range of 2 - 25, but more can be set.
The stronger the material, the more difficult it is to stretch. There is not enough tension behind the last die to simultaneously pull the material through all the dies of the multiple line. For this purpose, a separate pulling drum is used after each drawing. The pulling drum rotates, the drawn material, leaving the die, is wound onto the drum, at the same time unwinding, and moves on to the next die.
Multiple mills with sliding function
There is a proportion or ratio for all dies of the multiple drawing mill.
This condition is the key to the successful operation of the unit:
F1v1 = F2v2 = ... = Fnvn,
in this case F1, F2, ..., Fn is the cross-sectional area of the wire when it leaves the die;
v1,v2, ..., vn - speed when winding the wire onto the drum, when the wire comes out of the die.
The volume of material that is pulled through one die in a certain time must be the same for all dies of the mill, otherwise the wire will tear, throw off loops, and then get tangled.
The multiple drawing line shown in Fig. 5a, consists of 7 dies (item 1), sequentially located one after another, and 7 drums (item 2 and 3). The wire for drawing is put on the figure (item 4) (not driven). All seven reels are pulling. Drive pos. 5 and gearbox pos. 6 drive each drum installed for each die for drawing wire.
Several turns of wire are wound onto each drum, position 2. In operating mode, each revolution of the drum corresponds to winding one turn. In this case, one turn is wound from above. This is how a constant number of turns on the drum is ensured. The drawn wire as a finished product is wound onto a drum pos. 3.
During the operation of the mill, its dies naturally wear out. There may be inaccuracies in the manufacture of dies. Both aspects can cause a discrepancy between the peripheral speed of the drums and the speed of movement when pulling the wire between the dies.
It may turn out that the pulling speed will be some value greater than the peripheral speed of the intermediate drum. The drum will not be able to produce pulling force. In this regard, on mills of this type, with a sliding function, the peripheral speed of the internal drums is chosen to be 2-4% higher than the speed of the wire when it leaves the die. Due to this difference in the relative speeds of the drums, except for the last drum, the wire slips. This determines the name of the drawing mill "sliding mill".
Repeated drawing machines with sliding function are suitable for wire drawing production of soft materials such as copper, aluminum and mild steel. Made from durable steel, the wire slips only slightly. Otherwise, if there is strong sliding, the wire will become very hot, and significant wear on the surface of the drum will occur. And the surface of the wire itself will become rough.
When producing thin wire (less than 0.5-0.1 mm in diameter), step mills are used. For an example of such a mill, see Fig. 6. The designs of such mills include max. four drawing spindles and a maximum of 25 dies. In this case, it is necessary to select the dimensions of the dies and the diameters of the drums in stages. We see the wire drawing speeds on today's multiple mills in the following table:
Twin Drum Mills
In multiple drawing mills, where wire accumulates and can begin to curl, new ideas have been developed and applied. These developments are aimed at a method for winding wire onto drums and transporting it to the next die.
Shown in Fig. 8 mill represents a structure made of blocks. The number of blocks is equal to the drawing ratio. This type of design differs from the designs of conventional mills in that the spindle is equipped with two drums. The drums are installed one above the other. The drum at the bottom is fixed to the spindle with a key. The upper drum rotates freely thanks to the rolling bearings on which it is mounted on the spindle.
The wire is guided by a roller from bottom to top. It is wound onto the drums in opposite directions. See Figure 9. The wire, accumulating on both drums, upper and lower, goes down the rollers (2 guide rollers) to the drag of the next block. The process is repeated in the same way as in the 1st block.
The ends mounted on the drums fix the maximum and minimum wire reserves on the drums. When the maximum supply is reached, the end is triggered and stops the drum. As soon as the wire supply is again minimal, the other end gives a signal to start the drum.
If the upper drum is at rest, the guide roller rotates slower than the lower drum (twice). This promotes equal accumulation of wire on both drums with the same diameters.
With a slower winding of wire from the upper drum compared to winding on the lower drum, the accumulation of wire on both drums increases, and the guide roller makes rotation around the spindle axis slower than the difference in speed of the two drums, exactly twice.
If the amount of wire removed from the upper drum is equal to the amount of wire that was formed as a result of winding on the lower drum, then the guide roller does not rotate around the spindle axis. When the amount of wire wound from the upper drum exceeds the amount formed as a result of winding on the lower drum, the wire accumulates more slowly. The roller begins to rotate in relation to the rotation of the lower drum in the opposite direction, and the speed of rotation of the roller is lower than the difference between the rotation speeds of the upper and lower drums (exactly twice).
The drums of these mills are equipped with individual drives. The design of these mills has, along with a number of advantages (the wire does not twist, the finished wire can be removed from the drum and the spools can be replaced without stopping the unit, any drum can be stopped separately, an AC drive can be used) its disadvantages, which consist in numerous bends of the wire. As a result, it is difficult to thread the mill when there is wire with a large cross-section, which is intended for the drawing process.
Mills with a different drum design work on the same principle of operation, when they are placed one inside the other. Mills that have a counter-tension function are considered improved.
Multiple counter-tensioning machines or loop machines.
Counter-tension helps reduce die wear and the wire becomes more uniform in thickness. This makes it possible to perform the drawing process at high speeds.
Counter-tension is created by adjusting the speed of rotation of the drums, thereby preventing the wire from sliding along the drum. Such mills are equipped in the same way as other multiple drawing mills: several drums located one behind the other and dies installed between the drums.
See fig. 10. The designs of the drums on such mills are similar to the designs of the drums of new mills equipped with a sliding function. Motors are frequency controlled. Adjusting the speed of the drums ensures continuous wire drawing without slipping.
The wire goes around the drum, heading towards the tension roller, then goes around the idle roller, which is motionless, moving towards the die. After leaving the die, the wire goes to the next drum, and the process repeats. We see the direction of the wire in Fig. 10. It is indicated by arrows.
1 — finishing drum block; 2 — intermediate drum block; 3 - buffer; 4 - tension roller; 5 — speed controller; 6, 8, 10 — soap dishes; 7 — stepped drum block; 9 — guide roller; 11 — fan; 12, 13 — under-engine plates; 14 — gear coupling; 15 — electrical blocking of the panel; 16 — drawing speed meter: 17 — plate under the blocks; 18 — electric motor; 19 — shield; 20 - oil drain; 21 - foot barrier; 22 - manual barrier
In Fig. 12 shows an intermediate drum.
The drum position 1 is mounted on the spindle position 2. Motor drive using a gear coupling, multi-start worm pos. 4 and the worm wheel pos. 3 sets the drum in motion. A separate block consists of a drum pos. 1, spindle pos. 2, gear housing, represented by the upper pos. 6 and lower pos. 5 parts of it. The number of passes during the drawing process determines the number of blocks subsequently mounted on the frame. Due to the fact that such drawing machines are high-speed, only a few turns are wound on the drums, the drum and wire are heated, and they need to be cooled. Water is supplied to cool the drums. The wire is cooled with air. The dies are mounted in a so-called soap box and cooled with water. The mill structure is shown in Fig. 13.
The emergency switch turns off the unit if the wire gets tangled. Mills equipped with a counter-tension function have a number of advantages:
- when transporting wire between drums, it does not twist;
- counter-tension is created by automatically adjusting the speed of the drums;
- the counter-tension function helps reduce wear on the dies and reduce heating of the wire; this improves the quality of the wire and ensures high-speed drawing;
- there is no need to remove the wire from above, which eliminates injury to operating personnel.
This design of loop drawing mills has a number of disadvantages:
- when producing wire from high-strength steel, it is difficult to feed the mill;
- a large number of rollers (tension rollers, guides) creates additional bends for the wire;
- counter tension is adjustable within a small range;
- the forced use of direct current leads to increased cost and complexity of this design.
These disadvantages are not inherent in straight-through mills with a counter-tension function.
Loopless mills (direct flow)
In Fig. 14 cm another mill design with counter-tension function.
On this unit, only a few turns are wound onto the drums (from 6 to 10 wire turns per drum). These turns are quite enough to create the necessary friction force concentrated between the drum and the wire. The strip is pulled through the dies without slipping. The wire is transported without rollers, which prevents the strip from twisting during the transition.
Counter tension on loopless mills is created by electric motors. This allows higher counter-tensions to be applied and adjusted over wider ranges. The fact that these mills do not have so many different rollers makes it easier to thread the mill when drawing thick wire from high-strength materials. Not all types of wire allow large crimps. It is for them that the use of countertension is important and effective. Shaped wire is produced using small crimps. This reduces wear on the dies.
When producing low and high carbon steel wires, the back tension used is max. 10-15% of the total drawing force. In Fig. Figure 14 shows a mill for the production of wire from high-carbon steel grades by drawing. The mill drums are equipped with an individual DC drive. The drums are connected in series.
The torque is adjusted so that its excess determines the amount of counter-tension. The speed is adjusted only on the finished wire drum, the other drums are adjusted automatically based on the rotation speed of the finished wire drum and the reductions used in each die.
When threading the mill, the motor adjustment continues until its torque is sufficient to pull the wire through the die and create tension to turn the drum (back tension). It reduces pressure on the walls, and thereby reduces friction and heating.
With less heat, you can set a high speed during the drawing process. Excessive heating destroys the lubricant and reduces the quality of the wire and its surface. In such units, water is supplied to the drums and dies for cooling purposes, and cooling air is supplied to the wire.
Cooling helps to reduce the heating temperature of the wire and increases its tensile strength.
Mills of this type have the following positive aspects:
- when drawing the wire does not twist,
- provides drawing of wires of various profiles and non-circular cross-sections,
- wide range of counter-tension adjustment,
- there is no difficulty in refueling the mill,
- no rollers - no unnecessary wire bends,
- no speed controller,
- simplified diagram of the unit (mechanical and electrical).
Perhaps, the use of low voltage DC electric motors (less than 110 V) is one of the significant disadvantages of this design of such mills.
In Fig. 16b demonstrates the following type of drive, which creates a differential transmission. It is located between the electric motor and the gear train. Setting the speed of the drums directly depends on changing the compression mode. The speed is adjusted automatically.
When changing the compression mode, it is necessary to change the gear ratio on all drums. This is done on all straight-through mills that are equipped with AC drives. And the drives can be both individual and group. Individual - each block has a separate drive, and group - this is when one common drive is installed on all blocks at once.
The rapid change of modes during the operation of such mills is an indicator of its productivity. And the faster the mill operators begin to acquire skills in operating and servicing the unit. By turning the handle of just one switch on a mill equipped with a DC drive, the operator switches all the drums to a different speed. AC drives are more complex for such a simple switching of drawing speeds; here it is associated with switching gears in all gearboxes and in gearboxes, or switching is undertaken in both control units at once.
And most importantly, on AC drives it is difficult to enable soft start or smooth acceleration, which is very important when switching speeds, especially in the direction of increasing it.
This problem can be improved through the use of hydrodynamic couplings, because they help to significantly reduce the dynamic loads on gears when changing modes, when starting or stopping the unit, and also reduce the likelihood of wire breakage due to switching from one operating mode of the mill to another.
Mills with an AC drive cost less in terms of money than mills with a DC drive. But the latter, i.e. DC drives are more convenient to maintain and control. They have a much larger speed control range on all reels, and when changing the compression mode, the speed is adjusted automatically.
4. Production lines for wire drawing
Multiple drawing mills are, as is known, production lines. This means that the process on the line goes on continuously, from the delivery of blanks to the receipt of the finished wire, without stopping the line. Such mills process wire, deforming it as much as possible, stretching it between heat treatments or immediately crimping it to a given size.
Using this technology, it is possible to combine several single drawing mills in one line. By combining units in this way that were previously located in different parts of the workshop, time is saved on the costs of operations and transportation of workpieces.
Production lines are assembled from similar equipment according to power data, otherwise the overall productivity of the newly equipped production line may drop.
Combination of mechanical descaling and drawing operations
Today there are many combined lines known. Just as units for removing scale from products mechanically are combined with pickling lines, today devices for removing scale (mechanically) are combined with drawing mills (single and multiple drawing).
With this combination of two units we have the following positive aspects:
- there is no need to feed wire rod from the warehouse to the pickling line,
- then pickle there, do washing, liming or apply protective coatings,
- subsequently transport the wire rod to the drawing production.
The pickling line, which occupies large areas in the workshops, is difficult to combine with the drawing mill.
However, new mechanical descaling equipment, which is as productive as a modern drawing mill, makes it possible to create a combination of these two units.
Combining these offers the following advantages:
- staff reduction,
- reduction of associated costs,
- mechanical descaling equipment costs significantly less than chemical equipment,
- the descaling unit does not take up as much space in the workshop as a full-fledged pickling line,
- there will be no waste from the pickling unit and the environment will be clean.
Combination of drawing and annealing operations
Combined lines for continuous annealing and drawing processes are becoming more and more famous today and becoming widespread. A similar unit in Fig. 17. These combinations are of greatest value for processing copper wire (0.1-4.0 mm in diameter) in drawing production. The annealing speed varies depending on the thickness of the wire (its diameter). If it has a diameter of 0.15-0.4 mm, then it is annealed at a drawing speed of 22-25 m/sec, wire with a diameter of 0.4 to 1.0 mm is annealed at a maximum speed of 20 m/sec. Large diameter wire (1-4 mm) is annealed slowly (up to 6.5 m/sec.).
There are a number of combined lines, which include a number of units, for example, for the processes of drawing, annealing, tinning and applying insulating coating to wire. All these processes are continuous and high-speed, so at the beginning and end of the line there are, respectively, unwinders and coilers, which guarantee continuous supply of workpieces and removal of finished wire without stopping the line.
The advantages of such combined lines:
- great economic effect,
- the need for auxiliary equipment is reduced,
- significant reduction in production space,
- significant reduction in production costs,
- there is no transportation of raw material for transfer from one process department to another.
Multi-thread drawing
We come across the concept of “multi-filament drawing” when drawing particularly thin wires made of non-ferrous metals. Multifilament mills operate in continuous production mode; stopping the unit is not required to thread each coil or remove the finished wire. Wire drawing in such installations is combined with the process of annealing and coating the product. In combinations of this kind, the speed of the slower processing takes priority. There are 18-thread drawing machines, where the processing speed is no higher than 5 m/sec. In total, the speed reaches 90 m/sec.
Advantages of low speed on a similar mill:
- maintenance of the mill is simplified,
- the likelihood of wire breaks is reduced,
- stability in obtaining quality enameled wire.
If the operations are not combined, the mills are equipped with systems for two- and ten-thread drawing, here processing occurs at a speed of 10-15 m/sec.
The more threads on the mill, the lower the processing speed, and, accordingly, the lower the productivity. But this is explained by the fact that eliminating the consequences of a wire break on a multi-thread mill is associated with a huge loss of time in comparison with a single-thread mill. To increase productivity on a multi-thread mill, you should carefully prepare the material for the process (drawing), select technological lubricant and cooling means for the wire.
Today, the production of metal products is the most popular industry. These types of production include the production of metal products such as wire, iron rods, and pipes that are not too large in diameter. It is worth noting that the manufacture of all these metal products requires special equipment, which directly includes a drawing machine.
Drawing mill device.
This equipment is designed to pull the product through the so-called die, in other words, a special eye, while its cross-sectional size is smaller than the cross-sectional size of the source material. Drawing mills, directly depending on their operating principle, can be divided into mills in which the movement of metal is linear. And mills in which the processed metal is wound on a drum device.
Drawing mills of the first category can be rack and chain. They are used for drawing and sizing products such as rods, small diameter pipes and other similar products. Such material does not need to be wound into special coils.
The second type of drawing mills, in which metal is wound onto a drum device, is most often used for the production of materials such as metal wire, as well as special profile material. It is worth noting that this type of mill can, in turn, be divided into single-action mills. For multiple mills that work with sliding. To multiple mills, which operate without sliding, and finally, to multiple mills, which operate with counter-tension.
This equipment includes three main working elements, these working parts are a device for unwinding metal material, the part itself that performs drawing, and the finished product.
Operating principle of a drawing machine.
The operating principle of this device is as follows. The material to be drawn through the basket of the receiving compartment and also through special roller devices of a guiding nature is delivered to the roller, and then to the roller installed in a compensating type carriage. Already from this carriage the material is delivered directly to the drawing device itself.
The use of a device such as a compensating carriage is important in order to prevent wire breakage in the event of sudden braking of the die or a sudden stop of the entire device. The essence of this working mechanism is extremely simple: during a sudden stop when feeding a workpiece, the equipment blocks continue to rotate for some time and, accordingly, require the issuance of a certain amount of workpiece material. At this time, the compensating carriage of the drawing machine moves in an upward direction and thus releases the required amount of material, which actually enters the drawing device and thus breakage does not occur.
At the last stage of drawing, the material being drawn is supplied to the lower double-type drawing drum, after which, through a reversible type roller, it is delivered to the drum located at the top, which is accumulative. It is precisely because the upper drum accumulates the wire that it can be fed in the event of sudden braking of the device.
After the drawing procedure, the wire is fed to a special straightening device, which serves to give the product bends and a given shape. The drawing machine operates directly from an electric motor.
