Mechanization of thinning and through-cutting. Metal cutting purpose and purpose of metal cutting Study of mechanized methods of metal cutting
During thinning the ELHA unit can be used in apiaries 30-40 m wide. Skidding sights are laid at an angle to the technological corridor of 60 0 and trees are cut down onto it with an electric saw. The branches are cut off with it. The whips are skidded over the tops.
Promising variants of the “Dyatlov” could also be used. In 1984, at an exhibition in Moscow, a sample of the MVP-20 was exhibited on a self-propelled chassis with a 6-meter reach of the manipulator, cutting trees up to 22 cm. The high-performance version “Woodpecker-1D” has a trunk storage device on the boom.
Since the “Woodpeckers” only lay the trees on the skid, for their skidding they used the “Ant” bundle skidder, which was aggregated with the T-40A, MTZ-52 tractor and other narrow machines with four driving wheels. The skidder is an arrow that lifts a bunch of trees (wisps) by the butt.
In through-cutting, when selecting large-sized trees, a feller-buncher "Woodpecker-2" (LP-2) was used, created on the basis of the TDT-55 tractor with a second cabin on a turntable and a 10.5 m long boom, with a gripper and a console saw. In its development, the MVP-35 machine was designed with one cabin and a storage unit on the boom. The drive can accommodate 8 trees with a trunk diameter of 8-14 cm. The LP-54 machine was being prepared for production, based on the TT-4 tractor with a manipulator boom reach of 10 m.
During thinning and through cuttings, a wide-apiary technology of logging work with technological corridors laid every 60-100 m is promoted. Trees, logs (half-lengths), and assortments are skidded to them using a winch LT-100, LT-400, LT-600, ML-2000M or skidder tractor PDT-1, PDT-0.3. For example, the LT-400 winch is installed on a two-wheeled trolley, has a 65 m long cable and a base engine from a chainsaw, weighs 76 kg, and is operated by two people. Small whips are skidded in packs up to 0.4 m 3 using drags or chokers. Productivity with an average log diameter of 10 cm is 12-14 m 3. Tractor skidder PDT-0.3, in addition to a winch with a cable 65 m long, has a hydraulic manipulator for transferring the cleared wood along the drag.
Wide-grazing 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 crosscutting machine has been developed. Technological corridors 4 m wide are laid across crop rows every 80 m. Trees are felled with a chainsaw for skidding by the butt along the rows with a winch to a unit based on MTZ-82. Trees with a maximum butt diameter of 35 cm are processed. The assortments have a length from 1.5 to 6.0 m (multiples of 1.5) and are skidded by another machine.
The most common technology for mechanized thinning and through-cutting is medium apiary (width - 31-50 m) with felling of trunks with a chainsaw and skidding of trees or sticks by the tops with agricultural wheeled tractors equipped with a winch and shield, or skidding device LTP-2, LTN-1. Tractors T-5L, T-40A, T-25, MTZ-52, TL-28, etc. have proven themselves well. In areas where there are no technological corridors, technological corridors are prepared with a width of 2-3 m. More powerful tractors are also used: MTZ -82, MTZ-80 (with a factory skidding winch), LKT-80 and the TDT-55A tracked skidder, for which a 4-5 m wide drag is being prepared. The UTG-4.8 hydraulic grab can be installed on the MTZ-82 (80) .
Operating experience since 1982 of the forest wheeled tractor LKT-80 produced by Czechoslovakia has confirmed the possibility of developing a stable running system in the forest. Preparing for serial production in CIS countries wheeled skidder LT-19, equipped with a hydraulic manipulator for collecting the whips by the tops or butts using a hydraulic clamp. 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 for working on waterlogged soils.
On the skidding, trees begin to be felled from the far end, retreating from the boundary of the cutting area to the height of the tree (there is no need to lay a trail here, which also prevents damage to trees outside the cutting area), with the top in the direction opposite to the skidding. The branches of felled trees are cut off and placed near the growing trunks so as not to damage the cambium of the trunks and roots during skidding. Then, from the nearest side of the apiary to the upper warehouse (loading area), the trees are felled with their crowns onto the skid at an angle to it of no more than 40 0 for skidding the logs by the tops. The branches are cut off and the nearest ones are taken out on a trail to protect the soil and trees.
The branches removed from the trail are scattered or piled into small piles up to 0.5 m high. The exception is winter through cuttings in spruce-aspen plantations, where, in order to avoid attracting moose that damage the spruce, skidding should be carried out with the crown. In other cases, along with whip skidding, it is permissible to skid wood with half-lengths or assortments.
Burning logging residues necessarily in coniferous plantations on dry and fresh soils near railways and near other fire-hazardous objects. In other cases, logging residues should be considered as natural fertilizer. On dry and fresh poor soils (types of forest growth conditions A 0, A 1, A 2, B 1), spreading logging residues in the conditions of the Bryansk forest increases the moisture content of the upper soil horizons by 2 times, and the content of nitrogen, potassium, phosphorus in the litter - by 2-4 times. The soil temperature becomes optimal for the roots, which increases the growth of pine by 10-20% (Slyadnev, 1971). To prevent the spread of fire, it is better to localize such areas with mineralized strips. In Kazakhstan (in the field of dry forestry) to accelerate the mineralization of branches and weaken fire danger Crushing them with scattering along technological corridors at a distance of 10-20 m turned out to be effective. A self-propelled chipper LO-63B was mentioned for crushing.
It should be noted that agricultural tractors were not designed for work in the forest, and the chassis often has to be repaired. Because of this, arborists are forced to use skidding crawler tractors designed for clear-cutting. But they require wide portages and cause great damage to the forest. The need for serial production of wheeled tractors with an active semi-trailer has long been overdue: TL-28 (6 kN) based on a self-propelled chassis, ALP-1 (9 kN) based on the T-40AM, etc. The MTN-36 log carrier with a semi-trailer has been developed on the basis of the MTZ-80 PL-4 AOOT (Velikoluksky Plant) and semi-trailer loader PPD-6 (VNIILM).
In narrow apiaries, it is used for skidding of logs and assortments. 10-meter skidding manipulator MTT-10 based on MTZ-82 and LHT-55. During cut-to-length harvesting, the removal of logs from the corridor strips is carried out by a log truck equipped with a manipulator for loading and unloading logs up to 4.5 m long. The log truck transports the wood to the logging road.
Log carriers (forwarders) widely used in Scandinavia, where they work in combination with felling, delimbing and cross cutting machines (harvesters). High labor productivity in through fellings (up to 6.0 m 3 / person-hour) in a coniferous plantation 20 m high at a skidding distance of 100 m was demonstrated by the Harvester Lokomo 919/750N felling, delimbing, and cross-cutting machine with removal of stacked material from technological corridor 4 -meter-long timber transporter - Lokomo forwarder with a 10-meter hydraulic manipulator. Within a radius of 5 m, the harvester's electric saw is brought to a trunk with a diameter of 6-50 cm. The length of the cut logs is measured with an accuracy of ± 5 cm using a special roller, and information about the logs is transmitted to the operator's cabin on the display. The branches are cut simultaneously with the measuring and bucking of the trunk and fall in front of the machine, weakening the formation of ruts during further movement of the forwarder. To reduce root damage, the first harvester track is used for the forwarder. Then the first one, going 10 m deeper, moves between the trees, laying logs near the first ones, and, moving forward another 10 m, places them near its future track and the passage of the log truck. So the distance between the passes of the log truck is 25-30 m. Productivity is 90-160 m 3 .
Since 1989, we began to produce domestic “harvesters” and “forwarders” in our country together with the Terratek company from components from Finland, Sweden and other countries. Tests of these machines and other Finnish-Swedish samples have not yet given satisfactory results, since about 20% of the cutting area with wet soil turns into deep (up to 20-80 cm) ruts with the root system of nearby trees cut here, other trunks receive external and internal damage (up to 30% of trees in total). This technique is acceptable in winter time or for uniformly gradual and clear felling with preservation of undergrowth.
The Finnish Makeri machine turned out to be acceptable for thinning. This is a basic small-sized tractor, with a caterpillar chain on wheels, equipped in two versions, as a feller-buncher and a feller-delimbing-crossing 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; Giltz et al., 1986).
Other new machines can be found in the “Index of current regulatory and technical documentation for standardization in forestry.”
To organize and carry out mechanized thinning, plan the need for equipment, as well as labor and monetary costs, and draw up projects for organizing forestry for individual regions of the country, calculation and technological maps (CTCs) have been developed. Production form technological map is given in the Manual on thinnings.
Manual cutting is a labor-intensive and low-productivity operation. It should be used when machine processing (planing, milling, etc.) cannot be used.
To mechanize the cutting process, pneumatic or electric chipping hammers are used; special tools and devices; special machines, on which the cutting operation is performed 8-10 times faster than manually.
When chopping, hold the pneumatic hammer with both hands: right hand by the handle, and with the left hand by the end of the barrel, guiding the chisel along the cutting line (Fig. 100). The hammer should be put into operation after the cutting edge of the tool is pressed onto the surface being processed.
Rice. 100. Chopping pneumatic hammer
Special chisels are used as a tool for chopping with a pneumatic hammer. Cutting productivity when using a mechanized tool increases 4-5 times.
In electric hammers, the rotation of the electric motor shaft mounted in the housing is converted into a reciprocating movement of the striker, at the end of which a chisel or other tool is attached.
Our industry produces Various types pneumatic chipping hammers. The MP-4 hammer is designed for light chopping: the number of blows per minute is 3500, power is 0.54 kW, striker stroke is 41 mm. MP-5 is used for medium cutting: number of blows per minute - 2200, power - 0.43 kW, striker stroke - 71 mm. MP-6 is used for heavy cutting: with a number of blows of 1600, striker stroke - 106 mm, power - 0.42 kW.
Safety regulations
When cutting metal, the following safety precautions should be followed.
- the hammer handle must be well secured and free from cracks;
- when cutting with a chisel and cross-cutting tool, the mechanic must use safety glasses;
- When cutting hard and brittle metal, be sure to use a fence: mesh, shield;
- To protect your hands from damage (during uncomfortable work, as well as during training), you should put a safety rubber washer on the chisel, and a safety visor on your hand.
Self-test questions
- How are a chisel and a cross-cutting tool sharpened for cutting various materials?
- List the safety rules when cutting.
- How does the point angle, back and front angles affect the cutting process?
- What mechanized cutting tools are used in your workshop?
The development of modern technologies affects all spheres of human activity. New methods are being especially actively introduced in mechanical engineering, where every year the requirements for accuracy and quality of processing increase. Instead of the usual lathes or milling machines, CNC machines are used, while manual cutting, which is a labor-intensive and complex process, is replaced by mechanized cutting.
Modern mechanized methods of metal cutting are a whole complex of operations, the main distinctive feature which is the use of a special tool. As a rule, mechanized cutting is carried out with chisels equipped with pneumatic and electric drives. The main working tool in them are chisels, both with narrow and wide blades. Also, at large enterprises, mechanized felling cannot be done without special tools and devices, special machine equipment.
Advantages of mechanized cutting
Today, using the features mechanized methods chopping metals, you can achieve mass unique advantages, among which are the following:
- High cutting speed metal blanks and cutting of finished parts. The productivity of mechanized cutting compared to manual cutting is almost 4-5 times higher.
- Increased accuracy metal blank in the place of the log house. Modern chisels and other tools for mechanized cutting have a wear-resistant surface, and the equipment itself ensures the absence of scuffing and other defects.
- Metal saving. Special cutting equipment allows you to reduce the amount of waste, thereby reducing the cost of producing parts.
- Versatility. Using mechanized tools and machines, you can process any type of metal, from steel to non-ferrous alloys.
- Safety. Thanks to modern technologies the same pneumatic or electric chopping hammers are as safe as possible for workers, which helps reduce the number of injuries at work.
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Chopping is a metalworking operation in which, using cutting tool(chisel, cross-cutter or groover) and impact tool (machinery hammer) p. workpieces or parts, excess layers of metal are removed or the workpiece is cut into pieces.
Felling is carried out in cases where high precision processing is not required. The processing accuracy achieved when cutting is 0.4-0.7 mm.
Chopping is used to remove (cut down) large irregularities (roughness) from the workpiece, remove hard crust, scale, burrs, sharp corners edges on cast and stamped parts, for cutting out keyways, lubrication grooves, for cutting cracks in parts for welding (cutting edges), cutting off rivet heads when removing them, cutting out holes in sheet material.
In addition, cutting is used when it is necessary from rod, strip or sheet material cut off some part.
The cutting is done in a vice, on a plate or on an anvil. When cutting, small-sized blanks and castings are secured in a chair vice. Trimming of weld defects and bosses in large parts is carried out on site.
Cutting metal with a hand chisel is a very labor-intensive and difficult operation. Therefore, it is necessary to strive to mechanize it as much as possible.
The means of mechanizing metal cutting are: replacing the cutting with an abrasive tool, as well as replacing the manual chisel with a pneumatic or electric chipper.
When starting chopping, the mechanic must prepare his workplace. Taking a chisel and a hammer out of the workbench box, he places the chisel on the workbench on the left side of the vice with the cutting edge facing him, and the hammer with right side vice with the striker pointing towards the vice.
Of great importance for cutting is correct position locksmith body. When chopping, you need to stand steadily at the vice, half-turning towards it; The worker’s body should be to the left of the vice axis. Place your left leg half a step forward so that the axis of the foot is located at an angle of 70-75° relative to the vice. Move your right leg back a little, turning your foot at an angle of 40-45° relative to the axis of the vice.
The hammer must be taken by the handle so that the hand is at a distance of 20-30 mm from the end of the handle (Fig. 32, a). The handle is grasped with four fingers and pressed against the palm; in this case, the thumb is placed on the index finger and all fingers are squeezed tightly. Hold the chisel with your left hand, without squeezing your fingers too tightly, at a distance of 20-30 mm from the head (Fig. 32, b).
During the chopping process, the chisel should be directed at an angle of 30-35° relative to the surface being processed (Fig. 33, a). At a smaller angle of inclination, it will slide rather than cut (Fig. 33, b), and at a larger angle, it will go too deep into the metal and produce large processing unevenness (Fig. 33, d).
Essential to the process manual cutting in a vice also has correct installation chisels towards vertical plane fixed vise jaw. The normal setting of the cutting edge of the chisel should be considered an angle of 40-45° (Fig. 34, a). At a smaller angle, the cutting area increases, the cutting becomes heavier, and the process slows down (Fig. 34, b). At higher angle shavings, curling,
Creates additional shear resistance, the cut surface is rough and torn; it is possible to shift the workpiece in the vice (Fig. 34, c).
The quality of the cut depends on the type of swing and hammer blow. There are blows of the hand, elbow and shoulder. In a wrist swing, hammer blows are made with the force of the hand. This blow is used for light work to remove thin chips or when removing small irregularities. With an elbow strike, the arm bends at the elbow, resulting in a more powerful blow. The elbow strike is used in ordinary cutting, when it is necessary to remove a layer of metal of medium thickness, or when cutting grooves and grooves. With a shoulder strike, the swing is greatest, and the blow is the most powerful. The shoulder blow is used when chopping thick metal, when removing large layers in one pass, cutting metal and processing large planes.
When chopping using a wrist blow, an average of 40-50 blows per minute is made; with heavier work and shoulder impact, the cutting rate is reduced to 30-35 beats per minute.
The impact of the hammer on the chisel should be as precise as possible. It is necessary that the center of the hammer striker falls into the center of the chisel head, and that the hammer handle and chisel form a right angle. You can chop only with a sharply sharpened chisel; a blunt chisel slips from the surface, this quickly tires the hand and, as a result, the correctness of the blow is lost.
The size of the chips removed by a chisel depends on physical strength working, the size of the chisel, the weight of the hammer and the hardness of the metal being processed. The most productive is considered to be cutting, in which a layer of metal 1.5-2 mm thick is removed in one pass. When removing a layer of greater thickness, the mechanic quickly gets tired, and the cutting surface turns out to be unclean.
Chopping brittle metals (cast iron, bronze) should be done from the edge to the middle of the workpiece to avoid chipping off the edge of the part. When cutting tough metals (mild steel, copper, brass) cutting edge It is recommended to periodically moisten the chisels with machine oil or soap emulsion.
Chopping in a vice can be done at the level of the jaws of the vice or above this level - at the marked marks. At the level of the vise jaws, thin metal is most often cut, and above the level - wide surfaces of the workpiece.
When chopping wide surfaces To reduce time, you should use a cross-cutting tool and a chisel. First, grooves are cut with a cross-section, and then the resulting protrusions are cut off with a chisel.
To perform chopping correctly, you need to have good command of the chisel and hammer, that is, hold the chisel and hammer correctly, without slipping, and correctly swing and hit the head of the chisel with the hammer.
Currently, in forestry, chainsaws and motorized units are used in thinning areas.
Motorized brush cutters have become widespread in cutting trees when caring for young trees.
The 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 lightening, clearing and thinning.
The mobile motorized winch LT-400 is used for pulling trees, canes and assortments from apiaries into technological corridors when carrying out cleaning and thinning in cultivated and natural young stands.
The tractor-mounted wood skimmer PDT-1 is designed for pulling trees or tree trunks from apiaries into technological corridors and stacking them into bundles during cleaning and thinning. It is mounted on the MTZ-52 tractor. The unit is serviced by 2 people: a tractor driver and a choker operator.
The chokerless wood skidder “Ant” is used for skidding trees, logs and assortments during forest maintenance felling, thinning and clearing.
During thinning, through-cutting and sanitary felling, conventional machines and mechanisms used in final felling are also used. IN in some cases the LP-2 machine can be used. Its application requires strict adherence to technology.
The technology for thinning using mechanization consists of the following operations: organizing the cutting area, cutting down the tree, transporting the cut tree to the cutting site or consumer. In areas allocated for thinning, corridors are cut, using the road network whenever possible. The direction of the drags is chosen taking into account the wood traffic flow. The width of the trail can vary from 2 to 3 m, and the distance between them is 30-40 m, depending on the age of the tree stand (height) and thinning technology. The overall intensity of the initial thinning is set taking into account the optimal feeding area of the trees and can reach 40-50%, including the 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 last years Foresters, technologists, designers and economists were faced with a task: how to transform hard, low-productivity work in forest thinning into modern industrial work and at the same time protect the tree stand and soil from damage that leads to an imbalance in the forest environment and a decrease in forest productivity.
Integrated mechanization of work under the forest canopy is effective only if the economic indicators meet the requirements of forestry. Mechanization of forestry production is impossible without appropriate improvements in the organization of the territory, consolidation of care facilities, and resolution of a number of issues related to biological and technical optimization. The system for optimal organization of forest maintenance fellings includes the following elements: 1) setting target tree species; 2) identifying the stages of formation of target plantings; 3) building an optimally productive forest canopy; 4) determining the optimal number of trees per unit area; 5) organization of the territory; 6) technical carrying out one or another type or method of forming target tree stands.
Biotechnical optimization, combining into one whole bioecological formation factors with technological ones, suggests the most profitable in forestry and economic aspects methods for forming highly productive tree stands.
High efficiency of machines and mechanisms, as well as high performance complex teams are provided with the help of a well-organized territory of departments. The silvicultural effect (increased productivity) is obtained by leaving trees standing the best trees, ensuring the formation of an optimally productive forest canopy, as well as through the preservation of the forest environment.
The advantage of the mechanized method of forest formation is that here two processes of different importance are carried out simultaneously. One of them is the creation process better conditions growth for the main tree species remaining standing due to the removal of trees that do not meet environmental conditions. In this case, the resulting skidding trails fulfill a biological purpose: 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 there is still snow in control areas not affected by thinning.
Another equally important advantage of this method is the use of corridors as skidding, fire-fighting, protective, and utility roads, which are gradually improved and used to deliver workers, products, and other materials to sites. necessary materials. In addition, corridors in young stands and trails in mature stands ensure the safety of young stands when harvesting dry stumps remaining after cutting trees. With this method it is convenient to carry out operational technical control any site, regardless of its location.
For artificial plantings, a linear-selection thinning method has been developed, which allows you to perform a full range of working operations during thinning, as well as use modern machines and mechanisms. At the same time, selective selection of trees is carried out to form an optimally productive forest canopy.
According to VNIILM technology, branches are pruned using the OV-1 mechanism. To cut trees intended for felling, as well as trees located in a row, use “Secor”, a petrol-powered pruner BS-1, a self-propelled unit SMA-1, LP-2. Trees are cleared with a mobile winch LT-400, a skidder PDT-1 with a winch for pulling trees up to a distance of 500 m and a hydraulic manipulator for carrying trees and tree trunks from the apiary to the drag and laying.
A narrow-sized T-54L crawler tractor is used for skidding trees and logs. In mountain forests there are lightweight rope installations, rope descents, a mobile chipper PRUD, trailers for transporting wood chips, etc.
Thus, the formation of target forests in the process of thinning and increasing their productivity is carried out through the rational placement of plantings according to the appropriate growing conditions. To achieve this goal, a scientific organization forestry on enlarged soil-typological areas, allowing for concentrated activities based on mechanization. Qualitatively distinct periods are identified in the process of formation of forest stands in time, in relation to which the intensity, time and frequency of thinning are assigned.
The structure of an optimally productive forest canopy is formed from target trees identified in the forest according to certain characteristics. The number of trees that need to be left per unit area is determined for each stage using specially developed mathematical models that include the biological and technological requirements for the formation of target stands of high productivity.
The economic efficiency of using mechanization in thinnings is especially high during clearing and clearing.
Complex mechanization was not used properly due to the fragmentation of the departments in which the machines and mechanisms were supposed to work. The average plot area in individual forest districts of the European part of the USSR was 1.5-2 hectares. In such small areas, machines and mechanisms are difficult to use effectively. The struggle for the rational use of every hectare of forest area required the development new system organization of forest maintenance fellings.
In recent years, it has become clear that planning thinnings based on overcrowding is not enough. Carrying out regular maintenance in case of thickening, for example, in aspen trees growing on sandy soils, is impractical: by the age of ripeness, a planting of quality class III is formed. It is also undesirable to keep low-density plantings standing while waiting for the formation of density necessary for thinning, because aspen has occupied the soils on which pine forms highly productive forest stands.
In addition, young plantings that have occupied soils that are not typical for them, regardless of age, must be reconstructed. The bonitet class, often used as a criterion for establishing the intensity of thinning, cannot always fulfill this role with sufficient justification, since one bonitet class can characterize completely different conditions habitat. At the same time, weak thinning should be carried out on poor dry soils.
On poor, waterlogged soils, a significantly greater effect will be obtained by drainage works. Rational use Each hectare of forest land requires the combination of small plots based on common environmental conditions and economic purposes.
For 1970-1976 these problems were solved on the basis of the introduction of a quarterly or block method of organizing work. In areas united by common soils and target plantings, there is a concentration of not only forest thinning, but also various other activities that need to be carried out in the plantings in order to best distribute tree species in space and obtain high productivity from each hectare of forest area.
The concentration of thinning has provided significant silvicultural and economic benefits. Improves high-quality composition forests at the expense correct use state forest fund lands. The productivity of plantings increases as a result of better meeting the needs of trees for nutrients, located in the soil. An optimally productive forest canopy, created during the formation of tree stands, improves the process of photosynthesis. All this creates optimal conditions for the growth and development of trees. Organization of thinning in blocks or quarters is also carried out in Belarus, Ukraine, and the Baltic republics.
The consolidation of territories made it possible to apply advanced technological processes, improve working conditions for complex teams, significantly facilitate technical control over work in the forest, increase efficiency in organizing the fight against forest fires and forest pests, reduce labor and cost costs for caring for mixed young stands compared to mechanical removal unwanted trees, increase labor productivity and thus obtain the greatest silvicultural and economic benefits.
