BASES OF METAL PROCESSING OF METALS

Basic concepts of the theory of basing, editing and markup

1.1.1 Theory of workpiece based.  Base - a surface, line, point that determines the position of a part in a node during processing or control. There are design, technological and measuring bases.

Design bases -  assigned during the design and determine the mounting dimensions in the node.

Technological bases  - determine the position of the part (workpiece) in the machine relative to the headstock, spindles, cutting tool. From them measure the dimensions in the manufacture of parts.

Measuring bases  - determine the position of the surfaces of the parts relative to the measuring tool.

It is desirable that the design and technological bases coincide. For machined parts, the most processed surface is taken as technological base; for cylindrical billets or billets with holes, a flat surface parallel to the axis of the surface or the axis of the holes; untreated workpieces have one of the outer surfaces.

1.1.2 Editing  - an operation designed to eliminate distortions in the shape of the workpieces (dents, bulging, waviness, warpage, curvature, etc.).

Editing is performed on both cold and hot metal. Editing is performed manually (on a steel or cast-iron plate or on an anvil); on the right presses or on the right rollers. For manual dressing, hammers made of soft materials (copper, lead, hardwood) with a round polished brisk or smoothing and support (bars) are used. For hardened workpieces, hammers with a hardened shaped striker are used.

The curvature of the workpieces is checked by eye, by the gap between the dressing plate and the workpiece laid on it. Curved places are marked with chalk.

Editing raw material:

a) editing a strip curved in a plane  - In the most convex places inflict heavy blows with a hammer or sledgehammer. As you straighten, the force of the impact is reduced, the workpiece is periodically turned over;

b) editing a steel strip curved to the rib  - the workpiece is laid on the plate, dividing along the length into approximately equal in width to the curvature zone. Impacts are applied in rows from the center to the edges, starting from the concave part itself, the force of impacts decreases from the most curved part to the less curved (see fig. 1.2, and);

c) editing twisted stripes  - carried out by the method of unwinding; one end of the workpiece is clamped in a locksmith (stationary) vise, the other - in a manual vise, unwinding is carried out by a lever inserted into the special. hole of a manual vice;

g) editing sheet material  - chalk convex and wavy places; then strike according to the scheme (see fig. 1.2 b), from the edge to the center the force of blows

decreases; during editing, the sheet is turned in the horizontal plane so that the strokes are distributed in a circle over the entire area. If the sheet has undulations, then it is ruled first; the sheet in the middle is extended and the undulation disappears.

a - steel strip; b - sheet material; in - hardened square

Figure 1.2 Schemes of editing material

d) editing thin sheets  - it is carried out with a wooden hammer (with a mallet0 or with the help of a textolite gasket, which is placed on convex places; beat with defects with a hammer; foil materials are laid on a flat surface and ironed with smoothing machines - even plates with rounded edges;

f) dressing of hardened material  - carried out with a bench or straightening hammer with an elongated or rounded striker. The strip is laid bulge down, the blows are frequent, but not strong. Complex parts rule along the contour of the distortion, for example, corners. The scheme of striking, their strength and direction are shown in fig. 1.3, c.

1.1.3 Markup. Preparation of materials for work. To mark the surface is prepared in the following sequence.

1 Preparation of dyes.  For coloring unprocessed surfaces (castings, forgings, rolled) chalk solution is used (ground chalk is diluted in water). To protect the paint layer from abrasion and to quickly dry it, carpentry glue is introduced into the dye (600 g of chalk and 50 g of wood glue in 4 l of water).

Purely treated surfaces of the products are painted with a solution of copper sulfate (two to three teaspoons of crystals of copper sulfate in a glass of water) or with a special varnish for marking.

2 Preparation of the workpiece for painting. When preparing blanks for painting, they are cleaned of dust, dirt, scale and rust with a steel brush. The plates must not have any burrs or sharp corners. One plate is cleaned on both sides with a sandpaper, and the planes of the remaining plates are left untreated.

3 Surface painting.  When applying the dye, the workpiece is held in the left hand in an inclined position.

Figure 1.3 techniques for painting surfaces before marking

A thin and uniform dye layer is applied to the plane by cross vertical and horizontal brush movements. The solution should be typed only with the end of the brush in a small amount to avoid the formation of smudges. The stripped planes are painted with a solution of vitriol, and the untreated planes with a chalk solution. After coloring, the plates must be dried.

4 Markup- drawing on the workable surface of marking lines (scribbles), which show the boundaries of the workpiece. There are flat and spatial markings. (The difference is on their own).

a - scriber; b - dual gage; in - stangenrejmas; g - punch;

d - marking line before processing; e - marking line after processing

Figure 1.4 Tools for scribing

When marking, three types of tools are used (see figure 1.4, a - g):

a) for drawing and stamping of marks - scriber, single or double thicknesses, calipers, marking compasses, center punches;

b) to find the centers of circles (holes) - center punch-center-detector, square-center-finder, etc .;

c) marking devices - gaskets, jacks, rotary devices, uprights, dividing heads, center heads, etc.

Markup it is made on special marking plates from gray cast iron. The upper working plane and the side surfaces of the plate must be processed by scraping, be dry and clean. At the end of the work, wipe the plate with dry rags, grease it and close it with a wooden lid; Brush metal dust and chips into a dustpan. There should be a special litter box nearby.

The workpiece must not be moved over the slab to prevent scratches and nicks. The plate is placed on a stable foundation in a lighted place. Provides for general vertical and local lighting of the workplace.

Before work, the workpiece is cleaned with a steel brush and sandpaper about corrosion, scale and so on. Before marking, it is necessary to study the drawing of the part, compare the dimensions of the workpiece with the actual dimensions of the part, determine the technological base. After that, the types and sequence of markup operations are determined.

Methods of plane marking. First, all horizontal lines and risks are applied, then all vertical lines, then inclined ones. The last to be drawn are circles, arcs and conjugations. If center risks are chosen as the technological base, then markup begins with them. The marking is completed if the image on the plane is fully consistent with the drawing of the part.

Straight lines are applied with a scriber, tilted away from the ruler. The ruler or square is pressed firmly against the workpiece, draw a line once, without interrupting the movement of the hand. If the line (of risk) did not work out, it is painted over and drawn again. The division of the circle into equal parts is done by geometric constructions or using special tables. To mark a batch of identical parts using templates that are made of sheet steel. The configuration and dimensions of the template must exactly match the drawing of the part.

Methods of spatial marking. The difficulty of spatial marking is the need to link the markings of various surfaces with each other.

As a technological base, a surface is selected, relative to which you can mark the largest number of axes or planes, set

the main axis of the workpiece, the number of its positions on the plate and the marking sequence.

The workpiece is firmly installed without swinging on a marking plate so that each axis or plane of the part is perpendicular to the general plane of the plate. For installation and alignment of the workpiece, prisms, support pads, jacks, marking cubes and special devices (for example, rotary ones) are used. The first installation is made so that it is convenient to start marking from the selected technological base.

The methods of spatial marking basically coincide with the methods of planar marking.

Punching Marking Risks. After marking, the lines are tilted. Kerner is taken with three fingers of the left hand (thumb, forefinger and middle). The center punch is set exactly to the middle of the risks or to the intersection point of the pictures. Before the punch, the punch a little deviate from itself, and at the moment of impact turn vertically. The intended and tipped part is shown in fig. 1.4, d, e.

Practical lesson on the topic “Drawing up a routing map of material marking”. The time is 2 hours.

10 Lecture 2

Chopping and cutting of metal

1.2.1 Cutting blanks  carried out using a special cutting tool: chisels ( figure 1.5 a), crosshead ( figure 1.5, b) or groove ( figure 1.5, in) Cutting is carried out in cases where high precision machining is not required or when the part cannot be machined. With the help of cutting, the excess metal layer is removed from the workpiece, the workpiece is cut into pieces, holes are cut out, lubrication grooves are cut through, etc. The cutting of small blanks is carried out in a vice; large workpieces are chopped on a stove or on an anvil.

The chisel consists of three parts: working - 2 medium - 3   and shock - 4   (firing pin). Wedge-shaped cutting edge - 1 and the firing pin is tempered and released (HRC edge - 56 ... 61, firing pin - HRC 37 ... 41). The values \u200b\u200bof the angle of sharpness of the cutting edge are given in table 1.1. The crosshead is different from the chisel with a narrower cutting edge. It is used for cutting narrow grooves. The grooves are distinguished by the curved shape of the cutting edge and the working part.

The quality and performance of the cutting depends on the force of impact with a hammer and the position of the chisel. With a wrist stroke, only the hand with the hammer bends. Such a strike is used when performing precise and light work. With an elbow strike, the arm bends at the elbow, and the strike is more powerful. Frequency of strokes: with a hand stroke - 40-60 strokes per minute, with an elbow stroke - 30-40 strokes per minute. The angle between the workpiece (the upper plane of the jaws of the vice) and the axis of the chisel should be 45 about, the angle of inclination of the chisel - 30-35 about.

Table 1.1 & The sharpening angles of the cutting part

When cutting strip and sheet metal, the part of the workpiece that goes into shavings. It should be located above the jaws of the vice, and the risk of marking - exactly at the level of the jaws without distortions. When cutting metal on a wide flat surface, marking risks should protrude 5-10 mm above the jaws. At the same time, grooves 8-10 mm wide are cut through with a crosshead first. The gaps between the grooves should be 0.8 times the length of the cutting edge of the chisel. Then, with a chisel, the formed protrusions are cut off.

When chopping brittle materials, they do not reach the opposite edge of the workpiece by 1.5-2 mm, or they first make a bevel at an angle of 45 °. When cutting grooves and lubrication grooves, a groove with a depth of 1.5-2 mm is cut through with a kreimeysel in one pass. Then the remaining irregularities are cleaned with a groove, they are also given the groove with the final depth, width and shape.

When cutting a shaped blank from sheet material, the latter is laid on a plate or anvil. Initially, with brush strokes, the intended contour is cut to a depth of 2-3 mm. Next, the sheet is cut with strong elbow blows. If the sheet is thick, it is turned over and finally cut through from the back.

Manual cutting is a difficult and inefficient operation. To facilitate the work of a locksmith, pneumatic hammers (knife switches or riveters) are used. The domestic industry produces pneumatic rivets KE-16 - KE-32 grades weighing 8-12 kg and lightweight rivets MP-4 - MP-5 weighing 4.2 kg.

a - a chisel; b - crosshead; in - groove

Figure 1.5 Tool for cutting metal

1.2.2 Cutting  - separation of the workpiece into parts manually or mechanically. Manual cutting, depending on the profile of the workpiece and the cross-sectional area, is done with hacksaws, metal scissors, gas-flame burners.

The most common cutting with a hand hacksaw. Hacksaw (see figure 1.6 a) consists of a frame (machine) 2 in which a steel plate with teeth is clamped (hacksaw blade) 5 . Hacksaw blade inserted into the slots fixed 3 and moving 6   prismatic heads and pins. Web tension is done with wing nut 1 . To reduce friction on the lateral surfaces, the teeth of the hacksaw blade are bred in different directions. Tooth sets are done on the tooth or on the canvas. Depending on the material. From which the web is made, cutting is performed with a certain frequency: tool alloy steels - no more than 60 double passes per minute, tool carbon steels - no more than 30.

When cutting, the workpiece is securely clamped in a bench vise, providing a minimum distance between the jaw line and the cut line. When cutting thin steel billets or billets of soft material, it is clamped between two wooden bars and sawing is carried out with them. When cutting thick-walled workpieces, the cut is not brought to the end by 3-5 mm. After cutting, the workpiece is broken off.

When cutting workpieces from materials with low thermal conductivity (plastic), the cutting zone must be watered with water or kerosene.

Sheet material is cut with scissors for metal. To mechanize the process of cutting sheet material, electric or pneumatic scissors are used.

The working part of the electric scissors is shown in figure 1.6, b. Slider 4   placed inside the case 3   gearbox and together with a movable knife 6   makes a reciprocating motion. Fixed knife 2   mounted on a coiled holder 7 . adjustment of knives by an eccentric 5   and nut 1 .

a - a hacksaw; b - electric scissors;

Figure 1.6 Metal Cutting Tool

1.2.3 The procedure for compiling route maps.To perform locksmith and other work with the material, a route map is compiled - a list of operations for sequential execution of work. The routing map is usually made by technologists for the worker. It includes the following sections (table columns):

- operation number;

- the name of the operation;

- a graphic image (what changes occur with the workpiece) with dimensional characteristics;

- equipment operations, ie, a list of tools (fixtures, equipment, materials);

- a brief description of the actions;

- notes, supporting information.

An example of such a map can be seen in table 1.2.

Table 1.2 & Route map of the technological operation (sample)

Cutting is called an operation  to remove a layer of material from the workpiece, as well as cutting metal (sheet, strip, profile) into parts by cutting tools (a chisel, crosshead or groove with a hammer). The processing accuracy during cutting does not exceed 0.7 mm. In modern engineering, the metal cutting process is resorted to only in those cases when the workpiece for one reason or another cannot be processed on metal-cutting machines. Chopping perform the following work: removal of excess layers of material from the surfaces of the workpieces (die-casting, welds, hole cutting for welding, etc.); chipping of edges and burrs on forged and cast billets; cutting into pieces of sheet material; cutting holes in the sheet material; cutting through lubrication grooves, etc.

Cutting is carried out in a vice on a stove or on an anvil. Large-sized blanks during cutting are fixed in a chair vise. Trimming of castings, welds and tides in large parts is carried out on site. Manual cutting is a very difficult and time-consuming operation, so you must strive to mechanize it as much as possible.

Cutting Tools

The tools used in the cutting are related to cutting, they are made of carbon tool steels of grades U7, U8, U8A. The hardness of the working part of the cutting tools after heat treatment should be at least HRC 53 ... 56 over a length of 30 mm, and the impact part - HRC 30 ... 35 over a length of 15 mm. The dimensions of cutting tools for cutting depend on the nature of the work performed and are selected from the standard range. As a percussion instrument when cutting, hammers of various sizes and designs are used. Most often, when felling, they use hand hammers with a round striker of various weights.

The chisel (Fig. 2.20) consists of three parts: working, medium, impact. As with any cutting treatment, the cutting part of the tool is a wedge (Fig. 2.20, a).

The action of the wedge-shaped tool on the metal being processed varies depending on the position of the wedge and the direction of action of the force applied to its base. There are two main types of wedge operation during cutting:

The axis of the wedge and the direction of action of the force applied to it are perpendicular to the surface of the workpiece. In this case, the workpiece is cut into pieces (Fig. 2.20, b);

The axis of the wedge and the direction of action of the force applied to its base form an angle less than 90 ° with the surface of the workpiece. In this case, the chips are removed from the workpiece (Fig. 2.20, c).

The planes bounding the cutting part of the tool (see Fig. 2.20, c) are called surfaces. The surface on which the chips come off during the cutting process is called the front, and the surface opposite to it, facing the workpiece’s surface, is called the back. Their intersection forms the cutting edge of the tool. The angle between the surfaces forming the working part of the tool is called the angle of sharpening and is indicated by the Greek letter b (beta). The angle between the front and the machined surfaces is called the cutting angle and is indicated by the letter 8 (delta). The angle between the front surface and the plane drawn through the cutting edge perpendicular to the cutting surface is called the front angle and is denoted by the letter y (gamma).

The angle formed by the back and machined surfaces is called the back angle and is denoted by the letter a (alpha).

The smaller the angle of sharpening of the cutting wedge, the less force must be applied when cutting. However, with a decrease in the cutting angle, the cross section of the cutting part of the tool, and therefore its strength, also decreases. In this regard, the value of the angle of sharpening must be selected taking into account the hardness of the material being processed, which determines the cutting force necessary to separate the metal layer from the surface of the workpiece, and the impact force on the tool, necessary to create a cutting force.

With increasing hardness of the material, it is necessary to increase the angle of sharpening of the cutting wedge, since the force of impact on the tool is large enough and its cross section should provide the necessary cross-sectional area to perceive this force. The values \u200b\u200bof this angle for various materials are approximately: cast iron and bronze - 70 °; steel of medium hardness - 60 °; brass, copper - 45 °; aluminum alloys - 35 °.

The back angle a determines the amount of friction between the back surface of the tool and the workpiece’s work surface, its value ranges from 3 to 8. The back angle is adjusted by changing the inclination of the chisel relative to the work surface.

Kreuzmeisel (Fig. 2.21) differs from the chisel by a narrower cutting edge. Crossheads are used for cutting grooves, cutting keyways and the like. In order to prevent jamming of the crosshead during operation, its working part has a gradual narrowing from the cutting edge to the handle. The heat treatment of the working and impact parts, as well as the geometric parameters of the cutting part and the procedure for determining the sharpening angles of the cutting part for crossheads are exactly the same as for the chisel.

Groove(Fig. 2.22) is used for cutting lubrication grooves in the liners and bushings of sliding bearings and profile grooves for special purposes. The cutting edges of the groove can have a straight or semicircular shape, which is selected depending on the profile of the cut groove. The groove differs from the chisel and crosshead only in the shape of the working part. The requirements for heat treatment and the choice of sharpening angles for grooves are the same as for a chisel and crosshead.

Bench hammers  (Fig. 2.23) are used when chopping as a percussion tool to create cutting forces and come in two types - with a round (Fig. 2.23, a) and square (Fig. 2.23, b) striker. The end of the hammer, opposite the striker, is called the toe; it has a wedge-shaped shape and is rounded at the end. The hammer is fixed on the handle, which during operation is held in the hand, striking the tool (chisel, crosshead, groove). To reliably hold the hammer on the handle and prevent it from slipping during operation, use wooden or metal wedges (usually one or two wedges), which are hammered into the handle (Fig. 2.23, c) where it enters the hole of the hammer.

Small size cutting  (up to 150 mm) of sheet material, wide surfaces of steel and cast iron billets of small sizes, as well as grooving in bearing shells, are performed in a vice.

On a plate or anvil, chopping the blanks into parts or cutting along the contour of blanks from sheet material is performed. Cutting on the stove is used in cases where the workpiece being processed is impossible or difficult to fix in a vice.

In order to give the working part of the chisel, crosshead or groove the necessary angle of sharpening, it is necessary to sharpen it.

Sharpening of the cutting tool is carried out on grinding machines (Fig. 2.24, a). The tool to be sharpened is mounted on the handrail 3 and with light pressure it is slowly moved along the entire width of the grinding wheel. During sharpening, the tool is periodically cooled in water.

Sharpening the cutting wedge surfaces  lead alternately - then one side, then the other, which ensures uniform sharpening and obtaining the correct angle of sharpening of the working part of the tool. The grinding wheel during operation must be closed by a casing 2. Eye protection against ingress of abrasive dust is carried out using a special protective shield 1 or goggles. The control angle of the cutting tool during sharpening is carried out using a special template (Fig. 2.24, b).

With thinningan ELHA unit can be used in apiaries 30–40 m wide. Under-skid visors are laid at an angle to the technological corridor 60 0 and trees are cut down with an electric saw. She is cut off by branches. Whips mash over the peaks.

Could get use and promising options "Woodpeckers". In 1984, the MVP-20 prototype was exhibited at an exhibition in Moscow on a self-propelled chassis with a 6-meter reach of the manipulator that cuts trees up to 22 cm. The Woodpecker-1D variant with a barrel storage on the boom is highly productive.

Since the Woodpeckers only lay the trees on a dribble, for their skidding they used the Muravei skidder skidder, aggregated with the T-40A tractor, MTZ-52 and other narrow machines with four driving wheels. A skidder is an arrow that lifts a bundle of trees (whips) behind a komli.

At logging sites, when sampling large trees, the Woodpecker-2 feller buncher (LP-2) was used, which was created on the basis of the TDT-55 tractor with a second cabin on a turntable and a 10.5 m boom, with a grip and a cantilever saw. In its development, the MVP-35 machine was designed with one cabin and a drive on the boom. 8 trees with a trunk diameter of 8-14 cm can enter the drive. The LP-54 machine based on the TT-4 tractor with a reach of the manipulator boom of 10 m was preparing for release.

At thinning and through cutting, a wide-cutting technology of logging operations is promoted with technological corridors laid 60-100 m apart. Trelings of trees, whips (half-whips), and assortments are carried out with an LT-100, LT-400, LT-600, ML-2000M winch or tractor poddelevshchik PDT-1, PDT-0.3. For example, the LT-400 winch is mounted on a two-wheeled trolley, has a cable length of 65 m and a base engine from a chainsaw, weight 76 kg, it is served by two people. Small whips are pulled by bundles of up to 0.4 m 3 with drags or chokers. Productivity with an average diameter of 10 cm whips - 12-14 m 3. Tractor shift gear PDT-0.3In addition to a winch with a cable length of 65 m, it has a hydraulic manipulator for transporting undermanned wood along the draper.

Wide-safety technology is especially recommended in forests with a dense network of roads that are used as technological corridors. In Ukraine, a thinning technology with a delimbing and bucking machine has been developed. Technological corridors 4 m wide are laid across the rows of crops through 80 m. The trees are felled with a chainsaw for skidding over the stumps between the rows between the rows with a winch to the unit based on MTZ-82. Trees with a maximum diameter of 35 cm are processed. The assortments have a length of 1.5 to 6.0 m (multiples of 1.5) and are skimmed by another machine.

The most common technology for mechanized thinning and clear-cutting is the mid-section (width - 31-50 m) with a tree trunk felled with a chainsaw and skidding of trees or whips at the top with agricultural wheeled tractors equipped with a winch and shield, or LTP-2, LTN-1 skidding device. T-5L, T-40A, T-25, MTZ-52, TL-28 and other tractors have proven themselves well. In areas where there are no technological corridors, technological corridors are prepared 2-3 meters wide. More powerful tractors are also used: MTZ -82, MTZ-80 (with a factory skidding winch), LKT-80 and a TDT-55A crawler skidding tractor, for which a 4-5 m wide fiber is being prepared. UTG-4.8 grip can be installed on MTZ-82 (80) .

The operating experience since 1982 of the forest wheeled tractor LKT-80 manufactured by Czechoslovakia confirmed the possibility of developing a stable running system in the forest. Prepares for serial production by CIS countries wheeled skidder LT-19equipped with a hydraulic manipulator for collecting whips for the peaks or for the butt with tick-borne hydraulic gripping. Its productivity at a skidding distance of 300 m is 38 m 3 per shift. It is planned to create a set of machines based on a caterpillar tractor to work on waterlogged soils.

The trees begin to felling at the far end, departing from the edge of the cutting area to the height of the tree (there is no need to lay a draw here, which also prevents damage to trees outside the cutting area), with the apex in the direction opposite to skidding. Branches are cut off at the dumped trees and laid near growing trunks, so as not to damage the cambium of trunks and roots during skidding. Then, from the nearest side of the apiary to the upper warehouse (loading bay), trees are felled with a crown on the dragging at an angle to it of not more than 40 0 \u200b\u200bfor skidding of whips beyond the peaks. The branches are chopped off and the nearest ones are pulled out to protect the soil and trees.

Branches remote from the drag are scattered or stacked in small piles up to 0.5 m high. The exception is winter felling in spruce-aspen stands, where skidding should be carried out with a crown in order to avoid attracting moose damaging spruce. In other cases, along with whip skidding, skidding of wood by half-logs or assortments is permissible.

Burning of logging residues is compulsory in coniferous stands on dry and fresh soils near railways and near other fire hazardous facilities. In other cases, chopping residues should be considered as a natural fertilizer. On dry and fresh poor soils (types of forest growing conditions A 0, A 1, A 2, B 1), scattering of cutting residues in the conditions of the Bryansk forest mass increases the moisture content of the upper horizons of the soil by 2 times, and the content of nitrogen, potassium, phosphorus in the litter - in 2-4 times. Soil temperature becomes optimal for the roots, which increases pine growth by 10-20% (Slyadnev, 1971). To prevent the spread of fire, such areas are best localized with mineralized stripes. In Kazakhstan (in the field of dry forestry), to speed up the mineralization of knots and reduce the fire hazard, it turned out to be efficient to crush them and spread them along technological corridors to a distance of 10-20 m. The LO-63B self-propelled chopping machine was mentioned for grinding.

It should be noted that agricultural tractors were not designed for work in the forest, and often the chassis has to be repaired. Because of this, foresters are forced to use skidder skidders designed for clear-cutting. But they require wide dragging, causing great damage to the forest. The need has long overdue for serial production of wheeled tractors with an active semi-trailer: TL-28 (6 kN) based on a self-propelled chassis, ALP-1 (9 kN) based on T-40AM, etc. Based on MTZ-80, an MTN-36 short-haul truck with a semi-trailer has been developed PL-4 AOOT (Velikoluksky Plant) and the semi-trailer loader PPD-6 (VNIILM).

With narrow apiaries, it is used for undercutting of whips and assortments. MTT-10 10-meter skidder  based on MTZ-82 and LHT-55. In assortment harvesting, assortments are transported from the near-lane lanes by a sortiment carrier equipped with a manipulator for loading and unloading assortments up to 4.5 m long. The assortment truck carries wood to the timber road.

Short log trucks (forwarders)  widely used in Scandinavia where they work in conjunction with feller-delimbing-and-cross-linking machines (harvesters). Harvester Lokomo 919 / 750N felling-delimbing and shearing machine showed high productivity at the clearings (up to 6.0 m 3 / man-hours) in coniferous stands 20 m high with a skidding distance of 100 m and hauling folded at the technological corridor 4 -meter-sized timber sortimentovozom - forwarder Lokomo with a 10-meter hydraulic manipulator. Within a radius of 5 m, the harvester’s electric saw is fed to the trunk with a diameter of 6-50 cm. The length of the cut assortments is measured with an accuracy of ± 5 cm using a special roller, and the assortment information is transmitted to the operator’s cabin on the display. The branches are cut at the same time as measuring and bucking the trunk and fall in front of the machine, weakening the formation of a rut with further movement and the forwarder. To reduce damage to the roots, the first track of the harvester is used for the forwarder. Then the first one, moving deeper by 10 m, moves between the trees, laying assortments close to the first ones, and, moving forward another 10 m, puts them near its future trail and the passage of the sortimentovoz. So the distance between the aisles of a short log truck is 25-30 m. Productivity - 90-160 m 3.

Since 1989, they began to produce domestic “harvesters” and “forwarders” from components of Finland, Sweden and other countries in our country together with the Terratek company. Tests of these machines and other Finnish-Swedish samples have not yet yielded satisfactory results, since about 20% of the forest area with moist soil turns into deep (up to 20-80 cm) ruts with the root system of the nearest trees cut here, other trunks receive external and internal damage (up to 30% of trees). This technique is acceptable in the winter or for uniformly gradual and clear cutting with the preservation of undergrowth.

Acceptable for thinning was the Finnish Makeri machine. This is a basic small-sized tractor, with a caterpillar chain on wheels, equipped in two versions, like feller-buncher and feller-delimbing-cutting machine. Power cutting felling knives cut trunks with a diameter of up to 25 cm. Machine width - 1620 mm, length - 2.6 m, height - 2.2 m, weight - 2-4 tons, engine power - 22 kW, traction force - 0.5 kN, productivity - 3.5-4.6 m 3 / h. It damages 5-10% of the number of trees and 10-15% of the soil surface (Nerman et al., 1984; Gilz et al., 1986).

Other new machines can be found on the "Index of current regulatory and technical documentation for standardization in forestry."

For the organization and conduct of mechanized thinning, planning the need for equipment, as well as labor and money costs, drawing up forest management projects for certain regions of the country, design and technological maps (RTK) have been developed. The form of the production flow chart is given in the Manual on thinning.

Metal processing is concluded in several operations, one of which is cutting. At the same time, the workpiece is divided into more convenient pieces, preceding the cutting process. Further, it is considered in detail by what methods metal cutting is carried out, possible problems, the difference between mechanical and manual operation and the types of equipment used.

Metal felling is a locksmith operation consisting in the action of a cutting or percussion instrument on a metal workpiece. The process allows you to divide it into parts, get rid of excess layers of material, as well as get grooves and grooves. The cutting tool for cutting metal is a crosshead or a chisel, and a hammer is a percussion hammer. The latter is always used for manual work, and the first two - depending on the desired result.

The chisel is designed for rough work and cutting burrs. It consists of 3 parts:

• working (cutting);
• medium (the master holds the chisel for her);
• shock (hit with a hammer on it).

Kreutzmeisel - a tool for cutting grooves and narrow grooves; for wide, a modified fixture with a different shape of the cutting edge (“groove”) is used.

Manual processing of workpieces in production is an energy-consuming and low-productivity process. Often it is replaced by a mechanical one.

The sequence of metal cutting with a chisel is as follows:

• the workpiece is placed on a stove or anvil, and better - fastened in a vice;
• the chisel is placed on the marking line (the place of chopping off) vertically;
• the hammer strikes lightly along the contour;
• followed by a deep cutting along the manifested contour;
• the workpiece is turned over;
• blows with a chisel are made on the other hand until the cutting is completed.

It is important to leave a small portion of the blade in the slotted groove so that the process is accurate. Now - a couple of words about the problems that arise during manual cutting of metal.

Possible defects

Manual cutting of metal is bad in that there is a chance of damage to the workpiece, although the whole process was strictly controlled. The following are common defects and their causes.

1. Curvature of the chopped edge (weak fixing of the part in a vice).
2. Edge "ragged" (strikes were carried out with a blunt chisel or incorrectly sharpened crosshead).
3. The parallelism of the sides of the product is violated (distortion of the patterns or workpiece in a vice).
4. The depth of the grooves varies in length (the slope of the crosshead was not regulated; the impact was uneven).
5. The appearance of nicks on the part (blunt chisel).
6. The presence of chips on the edge of the part or inside the groove (the bevel was not removed from the workpiece).

To avoid these problems and not to spoil the metal template for work, it is recommended to observe a number of rules:

• firmly fasten the part, if possible;
• keep the angle of inclination of the chisel at least 30 degrees;
• accurately mark the workpiece;
• work only with sharpened chisel and crosshead, monitor the angle of their inclination;
• chamfer the part before work;
• strike evenly.

Manual felling of sheet metal was the only way to work 50 years ago. Today, the masters are provided with equipment that requires only timely control from them, which works accurately, efficiently and without damage to the workpieces.

Guillotine cutting machines

Any enterprise engaged in the production or production of metal is equipped with special equipment. The advantages of its implementation are obvious:

• labor productivity is growing;
• staff safety is ensured;
• material processing is becoming better.

The most famous metal cutting machine in the production environment is known as the “guillotine”. It happens:

• manual;
• mechanical;
• hydraulic.

The first is a compact device for local work. It cuts sheet metal of small thickness (up to 0.5 mm) and is driven by human effort. The use of a manual machine for cutting reinforcement, iron, steel and other products is more effective than working with a chisel or crosshead, however, labor productivity will still be small. The reason is the need for human effort.

Equipped with foot drive. Its dimensions are impressive, and the allowable thickness of the materials for cutting is increased to 0.7 mm. By using the power of the legs, not the arms, productivity grows by a few percent.

Standing apart is a hydraulic guillotine that works autonomously and does not require human intervention. It is equipped with a control unit, in which up to a dozen parameters are set (type of metal, cutting angle and others). Permissible thickness of the workpiece varies depending on the model and reaches a few millimeters.

The above types of metal cutting are supplemented by equipment that is structurally different from guillotines and has an expanded scope.

Features of combined devices

The equipment includes press scissors and angle cutting machines.

The first cut and cut strip, sheet, shaped, long products. Press shears are indispensable for punching holes in workpieces, cutting open grooves. These combined cutting machines can cope with any profile (channel, corner, tee / double tee, circle, square and others).

Angle cutting machines are also called die cutting dies. They are distinguished by:

• simplicity of design;
• high productivity;
• increased accuracy of output products.

Are applied to angular processing of any materials. The compact design includes a measuring scale and chisels for cutting. The stamp for the process is selected depending on the thickness of the sheets.

Some tools used in metal cutting combine manual and mechanized labor. These include:

• pneumatic and electric chipping hammers;
• special machines, where standard methods of cutting with a chisel are accelerated by 5-10 times due to the use of special devices.

So that you have a clear idea of \u200b\u200bthe characteristics of the devices, then we will consider one example. In particular, the machine for cutting reinforcement SMZH 172.

Device features

The machine tool SMZh 172 is designed for cutting reinforcing steel, strips, metal profiles with a maximum allowable tensile strength of 470 MPa. It has several modifications:

• SMZH-172 A (continuous knife stroke);
• SMZH-172 BAM (continuous and single stroke).

Chopping machine for reinforcement SMZh 172 has the following technical characteristics:

• power - 3 kW;
• diameter of cut reinforcement - up to 40 mm;
• strip dimensions - 40x12 mm;
• cutting a square with a side up to 36 mm;
• backstage stroke frequency - 33 rpm (9 rpm - for a single stroke);
• maximum effort - 350 kN;
• weight - 430/450 kg.

The design of the machine for cutting reinforcement smzh 172 is supplemented by an adjustable emphasis with rack gearing, which allows you to get a smooth perpendicular cut.

The advantages of using equipment are:

• the ability to replace consumables (blades) at the workplace without the help of special stands;
• permissible long-term storage of the machine if it is not used (in accordance with the manufacturer's recommendations);
• ease of disassembling the mechanism in order to adjust the parameters.

The machine is unique, because it can work both autonomously (continuous movement of the chisel) and at the right time (single stroke when the handle is pressed). Felling the guillotine, for example, does not yet have such functionality. You can see the work of the CSF 172 machine in the video below.

Video: Manual cabin of metal on the machine tool SMZh 172.

Cutting metal billets is one of the main production processes. Heavy human labor is being replaced by machine work, and this is worth using. The listed tools for cutting materials cope with different workpieces. It is only important to choose the right equipment.

Currently, chainsaws, motor units are used in forestry on thinning.

Got distribution on cutting of trees when carrying out departures in young growth of brush cutters.

Self-propelled motor unit SMA-1 is designed for selective cutting of trees and shrubs with a diameter of up to 18 cm in forest crops and plantings of natural origin during clarification, cleaning and thinning.

The LT-400 mobile winch is used for pulling trees, whips and assortments from apiaries into technological corridors during cleaning and thinning in cultural and natural young animals.

The tractor PTT-1 wood skimmer is designed to be pulled from apiaries into technological corridors and stacked in bundles of trees or whips when cleaning and thinning. It is mounted on a MTZ-52 tractor. The unit is served by 2 people: a tractor driver and a choker.

The ant-free skidder of wood “Ant” is used for skidding of trees, whips and assortments for thinning, thinning and clearing.

When thinning, through passage and sanitary cutting, ordinary machines and mechanisms used in main cutting are also used. In some cases, the LP-2 machine can be used. Its application requires strict adherence to technology.

The technology for carrying out thinning with the use of mechanization means consists of the following operations: organizing a cutting area, sawing a tree, transporting a sawn tree to a cutting site or a consumer. In the areas reserved for thinning, cut corridors, if possible using the road network. The direction of the draggers is chosen taking into account the cargo flow of wood. The width of the drag can vary from 2 to 3 m, and the distance between them is 30–40 m, depending on the age of the stand (height) and thinning technology. The total intensity of the initial thinning is established taking into account the optimal area of \u200b\u200btree nutrition and can reach 40-50%, including cut down mass in the corridors. The work is carried out by a team of 3-5 people according to the developed technological maps.

In recent years, foresters, technologists, designers and economists have faced the challenge: how to turn heavy, low-productivity work on thinning forests into modern industrial work and at the same time protect the forest stand and soil from damage that leads to disruption of the balance of the forest environment and a decrease in forest productivity.

Integrated mechanization of work under the forest canopy is effective only if economic indicators meet the requirements of forestry. The mechanization of forestry production is impossible without appropriate improvements in the organization of the territory, the enlargement of care facilities, and the solution of a number of issues related to biological and technical optimization. The system of optimal organization of thinning of forest care includes the following elements: 1) establishment of target tree species; 2) the allocation of the stages of formation of target plantations; 3) building an optimally productive forest canopy; 4) determination of the optimal number of trees per unit area; 5) organization of the territory; 6) the technical conduct of a particular type or method of forming target stands.

Biotechnological optimization, combining bioecological formation factors with technological ones, suggests the most advantageous methods of forming highly productive stands in the forestry and economic aspects.

High efficiency of machines and mechanisms, as well as high performance of integrated teams are ensured at the same time due to a well-organized territory of detachments. The forestry effect (increase in productivity) is obtained by keeping the best trees on the root, which ensure the formation of an optimally productive forest canopy, as well as by preserving the forest environment.

The advantage of a mechanized method of forest formation is that two processes of different significance are simultaneously being implemented here. One of them is the process of creating better growth conditions for the main tree species remaining at the root by removing trees that do not meet environmental conditions. At the same time, the skidding loops formed fulfill a biological purpose: the sunbeam, reaching the soil surface, warms up and thereby makes soil nutrients more accessible to trees already at the beginning of the growing season, i.e., when the control sites not touched by thinning are still lies snow.

Another equally important advantage of this method is the use of corridors as logging, fire, protective, and utility roads, gradually improved and used to deliver workers, products and other necessary materials to the facilities. In addition, corridors in young growths and darts in ripe forest stands ensure the safety of young growth when harvesting dry stumps left after tree felling. With this method, it is convenient to carry out operational technical control of any site, regardless of its location.

For plantations of artificial origin, a linear breeding method of thinning has been developed, which allows you to perform a full range of work operations during thinning, as well as use modern machines and mechanisms. At the same time, trees are selected for formation of an optimally productive forest canopy.

According to the VNIILM technology, pruning of branches is carried out by the ОВ-1 mechanism. For cutting trees intended for felling, as well as trees located in a row, use "Secor", gas cutting BS-1, self-propelled unit SMA-1, LP-2. Trees are skimmed with a mobile LT-400 winch, PDT-1 podrelevshchik with a winch for pulling trees up to 500 m and a hydraulic manipulator for removing trees and whips from the apiary to the fiber and laying.

For skidding of trees and whips, the T-54L narrow-sized caterpillar tractor is used. In mountain forests, lightweight wire rope installations, wire rope slopes, a mobile chipper POND, trailers for transporting wood chips and others work.

Thus, the formation of target forests in the process of thinning of the forest and increasing their productivity is carried out by rational distribution of plantings according to the appropriate growing conditions. To achieve this goal, a scientific organization of forestry has been introduced in enlarged soil-typological sites, allowing concentration of measures based on mechanization. Qualitatively distinct periods in the process of formation of stands in time are allocated, in relation to which intensity, time and repeatability of thinning are assigned.

The structure of an optimally productive forest canopy is formed from target trees that are identified in the forest according to certain criteria. The number of trees that need to be left per unit area is determined for each stage using specially developed mathematical models that include biological and technological requirements for the formation of targeted stands of high productivity.

The economic efficiency of mechanization in thinning is especially high for clarifications and cleanings.

Complex mechanization was not used properly due to the fragmentation of the sections on which machines and mechanisms were to work. The average acreage in some forestries in the European part of the USSR was 1.5–2 ha. In such small areas, machines and mechanisms are difficult to use efficiently. The struggle for the rational use of each hectare of forest area required the development of a new system for organizing thinning.

In recent years, it has become clear that the appointment of thinning on the basis of congestion is not enough. Conducting regular departures with thickening, for example, in aspen forests growing on sandy soils, is inexpedient: by the age of ripeness, a class III bonitet plantation is formed. It is undesirable to keep low-density plantations on the vine in anticipation of the formation of the completeness necessary for thinning, because the aspen has occupied soils on which pine forms high-productivity forest stands.

In addition, young stands that have occupied soils not characteristic of them must be reconstructed regardless of age. The class of boniteta, often used as a criterion for determining the intensity of thinning, may not always fulfill this role with sufficient justification, since completely different conditions of growth can be characterized by one class of boniteta. At the same time, poor thinning should be carried out with weak thinning.

On poor waterlogged soils, a significantly greater effect will be obtained by conducting drainage work. The rational use of each hectare of forest land requires the unification of small areas on the basis of common environmental conditions and economic goals.

For 1970-1976 these problems were solved on the basis of introducing a quarterly or block method of organizing work. In areas united by common ground communities and target plantations, not only forest thinning is concentrated, but also various other activities that need to be carried out in the plantations in order to best accommodate tree species in space and obtain high productivity from each hectare of forest area.

The concentration of thinning has provided significant forestry and economic benefits. The qualitative composition of forests is improving due to the proper use of the lands of the state forest fund. Planting productivity increases as a result of the best satisfaction of the nutrient requirements of trees in the soil. An optimally productive forest canopy created during the formation of forest stands improves the process of photosynthesis. All this creates optimal conditions for the growth and development of trees. The organization of thinning by blocks or quarters is also carried out in Belarus, Ukraine, and the Baltic republics.

The enlargement of the territories made it possible to apply advanced technological processes, improve working conditions for integrated teams, significantly facilitate technical control over work in the forest, increase efficiency in organizing the fight against forest fires and forest pests, and reduce the cost of labor and funds for caring for mixed young growth compared to mechanical removal of unwanted trees, increase labor productivity and thus obtain the greatest forestry and economic effects.