The body of a modern car is a complex structure that performs many important functions. Its renovation is the other side of the medal of importance and functionality. It is complex and labor intensive.

Conditionally body repair can be divided into two stages. The first is the elimination of dents, the replacement of elements beyond repair. Second - .

Particular attention should be paid to restoring the geometry and rigidity of the lower part of the body, hidden from view. It is these elements that are responsible for the safety and driving characteristics of the car. All suspension elements are attached to it.

When saving on materials and tools for body repair, it must be remembered that such savings can affect the quality of body repair and be the result of common mistakes. It is about how to avoid such errors that you should familiarize yourself with the main features.

Features of body repair

We offer

Welding elements with conventional electrodes

Connecting body elements by electronic welding is difficult, but real. At the same time, the quality of such a connection is very low.

Violation of the thermal regime

If the metal is not allowed to cool during welding, then the body may shift, which will have to be additionally puttied. However, such defects can not always be corrected with putty.

Replacing parts in strict order

First of all, the doors are replaced, then the wings and thresholds are set. This is the only way to avoid the formation of gaps.

Painting not in color

This often happens if one body part is painted without a smooth transition to another. Even if the paint is matched exactly with the original, the old paint on the body has a change in shade, which is associated with fading in the sun and other environmental factors.

Shrinkage

Appear with poor quality and its insufficient drying. Usually appear after repair, when the car stands in the sun. Usually you have to re-polish the places of putty after that.

Shagreen

This is the relief of the applied paint. After painting, there is usually a shagreen on the body, but it is removed by polishing. But there is one that cannot be removed by polishing. Usually a defect occurs when the paint is applied incorrectly, at high temperature in the chamber, viscous paint.

Dust in the paint

It usually occurs if the car is not painted in a special chamber. But when painting in a dirty chamber, it also takes place.

craters

Indentations from silicone, which had to be cut with a special knife.

Burned varnish

It appears if you work with a grinder at high speed or grind the same place for too long, not allowing the varnish to cool.

The manifestation of rust

If the welds are poorly cleaned and primed, then rust can occur in these places, which appears through the paintwork.

Fulfilling car body repair in particular welding work, then for welding work you need to use a semi-automatic or argon welding. With the help of such welding, metal up to 1 mm thick can be boiled and the possibility of burning through body elements is excluded.

Body damage can be mild, moderate or severe. Straightening usually does not require special skills and using professional tools and materials will be within the power of everyone. Only certain difficulties and the need for skills may arise during straightening work after medium and complex damage to the body.

If more than 70% of the body needs repairs, it will be cheaper to buy a new car, isn't it body repair and sell the old one for parts.

You need to paint the car with fresh paint. The primer will help you identify irregularities and putty them with a finishing putty. You can paint only after the putty and primer have completely dried.

For painting, use a special spray gun. The paint should dry in special conditions of the camera without direct sunlight. Polishing is permissible only after the complete drying of the paintwork.

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Introduction

Under the influence of natural, climatic and anthropogenic factors, as well as the human factor, the integrity of the body is violated: damage as a result of traffic accidents, corrosion, warping. To restore the car to the original or close to the original body repair is carried out. The main task of body repair is the restoration or replacement of body parts. But before doing repairs, it is necessary to design the site on which this repair will be carried out.

Technological design is a very time-consuming process, the operation of this site, the profit of the enterprise where it is located, entirely depends on it. It systematizes a large and diverse range of organizational, technological and economic issues. Their study will help a young road transport mechanical engineer to succinctly present and master almost all issues.

The purpose of the course project: the development of technological process TR car bodies.

To this end, it is necessary to solve the following tasks:

1. Develop a technological process for TRing car bodies.

2. Perform technological calculation of a specialized section according to TR of car bodies.

3. Select equipment for a specialized area according to TR for car bodies.

1. Development of technological process TR of car bodies

The body is a part of a car or other vehicle designed to accommodate passengers and cargo.

Body repair in its current state in terms of technological complexity and cost of equipment is not inferior to such serious areas as the repair of engines or electrical equipment. In addition, over time, the complexity of the hull geometry increases, new color effects of finishing coatings appear, and the requirements for corrosion resistance of coatings increase. All this requires the improvement of repair technology.

Today, dozens of pieces of equipment can be used by bodyshops, from a hammer to a draft stand, and each tool can be selected from a variety of representatives of its class. There are about ten painting systems that have worldwide distribution, each of which has its own pros and cons. In addition, there is a large selection of auxiliary materials and devices that facilitate certain operations. The right choice of workshop equipment, as well as the painting system, determine the future success of the enterprise, and the right choice of the technological chain in each specific case - saving the client's time and reducing the costs of the enterprise.

In Figure 1, you can see the basis of a modern passenger car body. Reinforcement elements are visible in the cab floor, in the area of ​​engine mounting and front suspension, as well as in the area of ​​the trunk and rear suspension. In addition, it becomes clear which body parts are included in the base and which are mounted: there are no mounted ones in the figure.

Figure 1 - The base of the car body

1.2 Malfunctions of body elements

The main malfunctions of the car body are its mechanical (dents, holes, cracks) and corrosion damage, destruction of the paintwork and anticorrosion coating.

Mechanical damage occurs in traffic accidents and when driving at high speeds on rough roads. The most destructive damage to the body is in frontal collisions and collisions with the front part of the body at an angle of 40 ... 45 ° or from the side. Such collisions usually occur between two moving vehicles whose speeds add up. In this case, the car body is destroyed, especially its front part, and the large loads acting in this case in the longitudinal, transverse and vertical directions are transferred to all closely spaced parts of the body frame, especially its power elements.

Up to 6% of the country's car park are annually involved in traffic accidents of varying complexity. Some of the collisions are minor and do not cause significant damage to body parts. But the bulk of damaged bodies requires the involvement of qualified specialists with the necessary skills and experience in body repair, special tools and equipment to perform restoration work.

The most devastating damage to the body occurs in collisions with the front of the car. Such collisions occur, as a rule, between two vehicles moving towards each other, the speeds of which are added upon impact. The amount of energy released on impact is enormous. This energy is absorbed by the deformation of the car in tenths of a second. In such collisions, the body of the car is destroyed, especially its front end. The large loads acting in this case are transferred to all adjacent parts of the body frame, and through them to the front parts of the entire body. The energy released during the impact is absorbed during the deformation of the spars, mudguards, thresholds and the floor tunnel. The gaps in the openings of the front doors, which are pressed by the front pillars, are reduced. The front doors through the hinges and locks press on the central pillars and so on until the impact energy is completely absorbed. Corrugations are formed on the thresholds, the floor tunnel, the roof panels. There is a general distortion of the base and body frame. The attachment points of the transmission and engine assemblies change their location. The absorption of impact energy cannot cause shrinkage and thickening of thin metal such as a sheet, so large folds are formed in the impact zone or the metal is pulled out when dents are formed. The degree of damage to the body and the amount of subsequent repair vary significantly, with seemingly equal collision conditions. Slight changes in speed or angle of impact, vehicle weight or force application, vehicle design or road conditions, vehicle age, etc. significantly different volumes of repair are obtained.

Damage to the body in an accident is light, medium and severe. Depending on the degree of damage, the straightening method and tool are selected. Classic car body straightening is not a very complex science, but requires certain skills for medium and severe damage.

Light damage - the consequences of inattention when maneuvering or parking, carried out at low speed. Removing minor damage, as a rule, takes no more than a few hours. The work consists in preparing the damaged surface for painting, followed by painting.

Light damage to the body, in most cases, can be removed with improvised means, such as: rubber and metal hammers, levers, mandrels. Light damage to the metal, with a whole paintwork, can be eliminated with a minilifter. This is a dent removal tool. body repair technological calculation

The tool base for removing dents without painting has a number of specific tools, which are divided into several groups.

Figure 2 - Tools for removing dents without painting

The first group includes hooks or levers, this is the main tool that allows you to carry out repairs in hard-to-reach places.

The use of one or another hook is determined by the location of the defect, in each case the master chooses one or another hook for high-quality dent removal.

Hooks or levers are made of high-alloy steel, have a different diameter and bend of the rod, the handle is made of high-strength plastic.

Figure 3 - Hooks or levers

The second group includes knives for removing sealant in hard-to-reach places. With the help of a knife, the body sealant is removed, which interferes with the implementation of high-quality repairs. Also indispensable devices is a lamp with a vacuum clamp for quality control of the repair surface.

Figure 4 - Sealant removal knives

Figure 5 - Lamp with vacuum lock

The third group of tools includes a mini-lifter with a set of pistons and special adhesives for external pulling out of dents, to which there is no internal access.

Figure 6 - Minilifter

Thanks to this tool, minor irregularities are quickly leveled. As a rule, it takes no more than an hour.

Before proceeding with the repair, it is necessary to assess the degree of damage, determine the ways and steps for further action. To gain access to hard-to-reach places, you will have to dismantle decorative panels, lights, handles, sidelights, seals. Next, you need to install the lamp at a convenient angle to observe the behavior of the defect. The technology is based on the principle of impact from the inside, to restore the geometry of the body part. As we know from physics, a metal sheet has a molecular memory, which allows us to ultimately achieve a perfectly smooth surface.

To remove a deep dent, glue the plastic caps included in the minilifter kit.

Figure 7 - Plastic caps

Figure 8 - Reverse hammer

Figure 9 - Extraction with a reverse hammer

Figure 10 - Extraction with a reverse hammer

It should be noted that it is impossible for minilifters to completely restore the surface, so you will have to use hooks and levers to control the behavior of the dent with a suction cup lamp.

Figure 11 - Dent behavior control

Regular straightening a car takes much more time, as a different technology is used, which requires a different approach to business.

Medium damage - collisions at low speeds, when the body part can be restored by straightening. Such damages include: a broken wing arch, creases on the roof, hood, and so on. Probably, the damaged element will have to be dismantled for further restoration of geometry, preparation for painting, painting and installation of the restored element in its rightful place. Elimination of medium damage to the body takes from one to several days. In this course project, I will give an example of using a spotter.

Spotter (from the English spot - “point”) is a one-sided spot welding device, which has found its application precisely in the repair of car body panels. Spotters with electronically controlled welding modes are commonly called digital.

The most relevant is the use of a spotter when repairing bulky body parts that are difficult to get close to from the back (doors, thresholds, etc.). The spotter allows you to weld a fastener to a damaged surface, for which you can really pull out a dent, without wasting time on disassembly and assembly. Also, with the help of a number of spotters, you can heat the metal, which, with some minor damage, makes it possible to do without stretching at all - the metal itself takes on its previous shape.

Figure 12 - Spotter

Figure 13 - Spotter kit

1. To start work, you need to clean the work surface. All places of contact between the washer and metal must be thoroughly cleaned of paint and other materials.

Figure 14 - Cleaning the work surface

Figure 15 - Cleaned work surface

2. Grounding must be attached to the repair part, if the part is not removed from the car, it is necessary to disconnect the battery in order to avoid shorting the electronics.

3. With the help of a “spot gun”, we weld fasteners in the right places, for which we will “pull” the metal. (It can be washers, studs, "snake", triangles, etc.)

4. With the help of a reverse hammer, we pull out the necessary places. Other tools can also be used, for example: hydraulics, cables, chains, slipway.

5. Washers and rings that have acted as a "hook" can be easily removed with a twisting motion.

6. In the end, all that remains is to clean up the place of welding and start filling the car.

The most difficult blows are side and frontal. Usually in such cases, the geometry of the car body is greatly distorted. It is possible to perform such work qualitatively only with the availability of special equipment. In such situations, the slipway is used.

Stapel - equipment for restoring the frame and geometry of the car body, a device that allows you to straighten the body to the standard parameters by applying multidirectional efforts. A car is fixed on it in order to check the condition of its bottom and perform the necessary work on inspection and replacement of parts. The second name that a professional slipway has received is a body stand or straightening stand, which gives a complete picture of the area of ​​​​use of this type of equipment. It is extremely difficult to do without it - it allows not only to establish the cause and nature of the malfunction, but also to outline a repair plan and control its quality, both in the process and after completion of all necessary operations.

The scope of the slipway is quite wide: it is used both for fixing minor breakdowns, and for more serious and lengthy work - restoring a car after an accident or rollover, guaranteeing the car owner an attentive attitude to the problem and a wide range of basic and additional services. The slipway allows you to significantly reduce the time spent on car repairs, provide access to parts and mechanisms located both near the bottom and inside the body, which are extremely difficult to reach under normal conditions and is possible only if the car is partially disassembled, which slows down the repair process and automatically increases its value. And after all repair work is completed, the slipway provides the ability to monitor the vehicle's performance, if necessary, correct it.

The slipway has a relatively small size and minimal weight, it will easily fit even into the limited space of the service center. But at the same time, he is able to easily lift passenger cars into the air, the mass of which significantly exceeds his own mass. Strong fixation of the car and its protection against falling is provided by a special fastening system that has undergone rigorous testing for strength and reliability. At the same time, the slipway design eliminates damage to the car body or violations of its geometry both in the process of fixing and during repair work. In addition, it allows the use of sophisticated measuring technology during the repair process in order to establish the existing body geometry parameters with high accuracy and restore them to the required values.

Another important advantage of the slipway is the ability to create conditions for a more affordable repair of spare parts and auto body, while in the absence of the necessary equipment, it is necessary to change a non-working part, which entails large expenses. The presence of a body stand in a car repair shop is a guarantee of reasonable prices for car repairs and maintenance.

The use of a slipway with special control stands guarantees the correct position of the base points of the body, and this significantly improves the quality of repairs and labor productivity. The slipway consists of a base, a device for straightening a car body, a set of supports and a set of tools.

Fastening of the car body at the control points is provided by installing a set of interchangeable stands located on the transverse beams. Interchangeable supports provide the possibility of replacing body parts and are used in this case as base elements for determining the main overall dimensions of the body elements. This also allows the slipway to be used as a conductor for welding. For more reliable fastening, two clips are used for flanging the bottom of the body. Beam 2 for editing is fixed anywhere along the periphery of the support frame with wedge grips. The lever is connected to the beam at two points by means of a hinge, and through a hydraulic cylinder, and the lever is rotatable in the horizontal and vertical planes. The pressure in the hydraulic cylinder is generated by a pump.

Figure 16 - Building berth

Figure 17 - Building berth

Figure 18 - Slip for bodies

The body to be repaired is placed on appropriate supports and secured to them using locating pins and screws. One of the tools of the set is fixed on the damaged area and connected by chain 6 to lever 1. The pump drives the hydraulic cylinder rod and lever 1, which pulls the crumpled parts of the body through the chain in the right direction to the right size. For the final editing of individual elements, hand tools are used. If it is impossible to stretch and straighten some parts, then these parts are completely replaced by installing the replaceable elements at the control points of the slipway and their subsequent welding. The slipway is distinguished by smaller overall dimensions compared to the R-620 stand, compactness and mobility in the production of work. In addition, it allows you to restore bodies with large violations of geometric dimensions, which were previously considered unsuitable for restoration.

The service stations use special tools and devices to increase labor productivity and improve the quality of repair work. To remove sections of panels and replace body plumage elements that have significant mechanical damage and corrosion damage, a pneumatic hammer with a set of special cutters is used (Fig. 6). Providing high performance when cutting metal, the pneumatic hammer allows you to get good quality edges with a slight deviation from the applied markup. During the operation of the body, gas, electric arc, electric contact welding and in a shielding gas environment are used.

A characteristic feature of body assembly during repair is that the installation of parts on the body (wings, panels, inserts, etc.) is associated with their fitting in place. Using a set of special clamps for fast fastening and detachment of parts can significantly reduce the auxiliary time when installing parts. Shown in fig. 7 Clamps are available in four different gripping jaws. Clamp a is used to fasten parts of various configurations together, 9 for example, a sheet and a round bar, a round bar and a hexagon, etc. The clamp is designed to fasten large panels in case of the risk of warping during welding. The clamp is used practically for fastening all elements of the body plumage. Clamp g allows you to capture parts in hard-to-reach places hidden by large flanges. For the final dressing of individual body elements, a manual dressing tool is used. Body repair using special equipment makes it possible not only to increase labor productivity and production culture, but also to expand the list of services provided by service stations to car owners.

Figure 19 - Pneumatic hammer and a set of cutters

Figure 20 - Clamp for fastening body parts

Wrinkled areas on body door panels are repaired in different ways, depending on the location of the damage and its size. To straighten small dents on the outer door panel, use holes and mounting hatches in the inner door panel or pierce a special hole with a beard. Insert a support, screwdriver or appropriate spoon into the existing or obtained hole and squeeze out the dent until the surface of the outer panel is leveled. If necessary, the dent is finally leveled with solder or plastic and cleaned flush with the base metal of the panel.

When repairing the outer panel of a door that has large dents, metal deflection with tension, deflection with sharp transitions or the presence of cracks and breaks, it is partially replaced. To do this, using a hacksaw, a slotted grinding wheel, a chisel or a gas burner, cut out the outer lining and remove the damaged panel. Then the door frame is corrected, gaps and cracks are welded, and if necessary, these places are strengthened. According to the existing template, a blank of a new panel is cut out and installed in place. Attach the outer panel in several places to the frame and to the remaining part of the panel by welding. Then they are adjusted and checked along the doorway of the body. After that, the new part of the panel is finally welded using a gas burner. The resulting welds on the outer surfaces are treated with abrasive wheels, and then finally leveled with solder or plastic. Stands are used to fix doors during repairs.

Wrinkled areas on the wings, hood, trunk lid, mudguards and other body parts are corrected by punching and straightening, filling irregularities with solder or plastic, and heavily dented and rusted areas are replaced with new elements.

The process of preliminary alignment of dents is performed in the following sequence. The part is laid on the plate with a surface having a dent, and with the blows of a straightening hammer it is knocked out to the level of the undamaged part of the part. Then, with a wooden or rubber mallet, trim the surface. After preliminary leveling, straightening is used to finish the panel and give it a smooth surface. Parts are straightened manually, using machine tools and pneumatic hammers.

For manual straightening, straightening hammers, supports, stands with supports corresponding to the profile of the concave surfaces of the repaired parts are used. Working on a stand with a fixed support greatly facilitates the work of a tinsmith, since there is no need to hold the support and it becomes possible to easily move the straightened part along the support surface. For straightening, straightening and stripping the body, use a set of hand tools. In cases where the metal is stretched, local heating of the part is used to simplify the correction of dents.

Before proceeding with the elimination of body skew, its value is determined by comparing the damaged area with the same undamaged one, or a template is applied, made according to the shape of the opening in the body, for example, under the windshield or rear window. Distortions of the front spring brackets in relation to the rear and to the axle of the body are checked with templates.

Distortions are corrected mainly in a cold state with the help of mobile mechanical or hydraulic stretch marks. Mechanical is a pipe, at the ends of which threaded bushings are welded - one with a left-handed, the other with a right-handed thread. On the free ends of the screws screwed into these nuts, they put on and fix the heads with the help of conical pins. The heads are shaped to match the profile of the stretchable surfaces. In the middle of the pipe there is a through hole into which a rod is inserted to rotate it; while the screws respectively converge or diverge.

Stretching with a hydraulic device for correcting body distortions consists of a hydraulic cylinder, on one side of which an extension tube is screwed, and on the other, an additional lever with a rubber head. The plunger, on the outer end of which a rubber head is mounted, is driven by hydraulic pressure generated by a hand pump. A hydraulic device with a hand pump can generate a force of up to 10 tf.

Ties differ from extensions only in their mandrels, the working part of which is made according to the profile of the parts to be tightened. When installing stretch marks in the body, one head should rest against a fairly rigid base, and the other will allow you to correct the skew.

Some types of curvature on the doors, the roof of the trunk are corrected with screw clamps with appropriate linings. Cracks and breakages existing or formed as a result of stretching are welded, the welding spots are cleaned, after which the parts are finally straightened. To increase strength in places of body cracks, linings are welded, made of sheet steel with a thickness of 1-2 mm and fitted in place of the body from the non-front side.

The entire process of repairing and assembling a car body before painting is divided into separate operations. The sequence of body assembly operations depends on the design and occurs in the reverse order of disassembly. Initially, repaired metal parts or new spare parts are installed, then the body is painted, an anti-corrosion coating is performed inside and out. The final operations for the installation of units, electrical equipment, upholstery and fittings are performed after painting the body, mainly at the same work stations where disassembly operations were carried out.

Another factor in the failure of bodies in operation is corrosion - the destruction of metal when interacting with the environment. Corrosion develops especially strongly in places that are difficult to access for inspection and cleaning. These are closed cavities of the load-bearing body, structural pockets, sinuses, flanging, flanges, welds, etc., where moisture, dust, salt solutions periodically get and remain there for a long time, gradually and inevitably converting the metal into rust. Atmospheric pollution by emissions from industrial enterprises, vehicle exhaust gases and saline solutions from roads greatly accelerate corrosion processes.

Car corrosion is the destruction of the metal parts of the car (body, etc.) under the influence of an aggressive environment, due to irrational design and careless handling.

The car can be subjected to both chemical corrosion and electrochemical. A striking example of chemical corrosion is the destruction of the exhaust tract of the engine under the influence of exhaust gases. Also, gas chemical corrosion of a car can also be observed in its fuel system, if hydrogen sulfide, mercaptans, elemental sulfur, etc. are present in the fuel liquids. This corrodes the metal bearing shells.

But in most cases, the car is still susceptible to electrochemical corrosion, which affects more of the constituent parts of the car and takes place only in cases where an electrolyte is present on the metal surface. Studies have shown that under atmospheric conditions, a film of moisture is always present on the surface of any metal. Its thickness depends on temperature, air humidity and other indicators.

Any metal surface of a car is electrochemically inhomogeneous (some areas have a difference in electrode potentials). The surface with a lower value of the electrode potential (in contact with the electrolyte) becomes anodic, and with a large value - cathodic. Each pair of heterogeneous sections forms a short-circuited galvanic cell. There are a lot of such working galvanic cells on the surface of the car. In this case, only the anode sections are destroyed. The potential difference can occur for many reasons, which can be read in articles about external and internal factors of electrochemical corrosion.

If the metal surface is not protected, then there are always conditions for the occurrence of corrosion processes. The car can be subjected to local (spotting, pitting, filiform, through, intergranular, pitting, subsurface) corrosion damage.

Corrosion damage occurs due to the spontaneous destruction of metals as a result of their chemical or electromechanical interaction with the external environment, as a result of which they pass into an oxidized state and their physicochemical properties change. According to the mechanism of formation and course of the corrosion process, electrochemical and chemical corrosion are distinguished.

Electrochemical corrosion occurs when two different metals form a galvanic cell in the connection. Such corrosion can also occur when there is no contact between different metals with each other. The steel from which the body is made corrodes with water and oxygen. On the surface of the body there are areas with different electrode potentials, which is associated with local deviations in the chemical composition of the metal, leading to the formation of galvanic microelements. The rate of the process of electrochemical corrosion increases in the presence of pollutants, salts and acids in the environment.

Chemical corrosion occurs as a result of the oxidation of metals under the influence of atmospheric oxygen, salts, sulfur compounds.

Figure 21 - Corrosion of the car body

2. Technological calculation of the body shop for the repair of cars

2.1 Initial data

The initial data for the technological calculation of the project are taken on the basis of the results of the marketing research, i.e. for 2015; part of the data is selected from the statistical information. Initial data are given in Table 2.1.1

Table 2.1.1 - Initial data for technological calculation

Name	Designation	Meaning
Brand of serviced vehicles	cars
The number of arrivals of one car per year at the service station
Average annual mileage of serviced vehicles, km
Number of serviced vehicles per year, pcs.
Number of potential customers whose cars need body work, pcs.
Average labor intensity of light body repair, person h
Average labor intensity of repairing a medium-damaged body, people h
Average labor intensity of a complex body repair, people h

2.2 Mode of operation of the body shop

The mode of operation is characterized by the number of working days per year, the duration of the shift and the number of shifts. At the same time, the mode of operation should be selected based on the most complete satisfaction of the needs of the population in services with minimal production costs. The values ​​of the listed characteristics for the reconstructed service station are given in Table 2.2.1

Table 2.2.1 - Service station operation mode

Based on the data in the table, we are able to determine the fasting time fund, h:

D work.G T CM S, (2.2.1)

255 1.5 8=3060h.

2.3 Calculation of the annual volume of work of the body shop and the number of vehicles serviced

According to statistics, 70% of body repairs are light repairs, 23% - to eliminate distortions of medium complexity, and 7% of work - to eliminate complex and especially complex damage to the body.

Thus, taking into account the data obtained and the data in Table 1, we determine the number of cars that can be serviced on the projected site.

The calculation data are presented in Table 2.3.1.

Table 2.3.1 - Distribution of the scope of work by type of repair and forecast of the number of serviced vehicles

Let's determine the number of work posts for the reconstructed area:

Where?? - coefficient of non-uniformity of cars entering the body section;

The average number of workers simultaneously working at the post, people;

The coefficient of use of the working time of the post;

b - share of guard work;

Annual volume of body work.

We accept: ??=1; ; ??=1; b=1.

Let's take the number of working posts = 1.

The annual volume of acceptance and delivery of vehicles, man-hours, is determined by the formula:

where is the one-time labor intensity of work on the acceptance and delivery of cars, man-hours. Accept =0.5

By formula (3) we find:

Find the annual volume of auxiliary work, which is determined by the formula:

where b VSP is the share of auxiliary work, we accept 10%.

2.4 Distribution of annual volumes of work on the site

The annual volume of work of the TR section of passenger car bodies is distributed in accordance with the formula (5):

Table 2.4.1 - Distribution of the scope of work by type and place of their release

completion

Type of work	Scope of work
		At posts
Reinforcing

Harvesting and washing works are carried out before TR; they can be considered as an independent type of service, at the rate of 1 car arrival per 800 - 1000 km of run.

The annual volume of cleaning and washing work of city service stations, man-hours, is determined by the formula:

One-time labor intensity t U.M. (accepted according to Appendix A, Table A.1); for cars of an especially small class, we accept t U.M. = 0.15 man-hours

Table 2.4.2 - Distribution of auxiliary work

2.5 Calculation of the number of employees on the site

The technologically necessary number of workers at the body post, person-hour, is determined by the formula:

where T G - the annual volume of the type of work at the post.

F T is the time fund of a technologically necessary worker, equal to 2024 hours.

To determine the regular number of workers at posts, the time fund of a full-time worker is first established:

1832 hours for washers, cleaners, maintenance and repair mechanics, motorists, electricians, tire fitters, machine operators, carpenters, upholsterers, fitters, tinsmiths;

The number of workers at a post or in a workshop is determined by the formula:

The calculation results are entered in table 2.5.1.

Table 2.5.1 - Number of workers at posts

Type of work	At posts
			R ShP calculated, pers.	R ShPP accepted, pers.	T C man-h.		R ShTs estimated, pers.	R ShPC accepted, pers.
Body and aggregate (tin, copper, welding)
Reinforcing
Cleaning and washing
Total number of workers	At the posts? R ShPP = 2	In workshops? P ShPC = 0

Table 2.5.2 - Number of auxiliary workers

Type of work	T VSP i person-h.		R W calculated, pers.	R ShP accepted, pers.
Repair and maintenance of technological equipment
Acceptance, storage and issuance of material assets
Cleaning of industrial premises and territory
Car driving
Acceptance and delivery of cars
Total number of support workers?R GSP

2.6 Calculation of the number of posts and car-waiting places

The number of working posts for the i-th type of work is determined by the formula:

Body and assembly (tin, copper, welding) works:

Reinforcing works:

where T P i - the labor intensity of guard work of the i-th type, person-h;

P CP - the average number of employees at the post.

To determine the number of cleaning and washing posts, the daily number of car arrivals is first calculated using the formula:

The number of cleaning and washing posts during their mechanization is determined by the formula:

where c U.M. - coefficient of non-uniformity of the arrival of cars at the site of cleaning and washing works (for a site with up to 10 working posts u U.M = 1.3-1.5);

T U.M. - working hours of the cleaning and washing works area;

N U.M. - the productivity of the washing plant (accepted according to its

passport);

h - the coefficient of use of the working time of the post, equal to

The calculation results are entered in table 2.6.1.

Table 2.6.1 - Number of working posts

Body and aggregate (tin, copper, welding)
Reinforcing
Cleaning and washing
The total number of work posts? Х Рп i

The number of auxiliary posts is determined by the formula:

The number of auxiliary posts also includes receiving and issuing posts, the number of which is determined by the formula:

where all parameters are taken in relation to the points of acceptance and issuance.

The number of car-waiting places (places for cars waiting to be placed at work or auxiliary posts) is determined by the formula:

The number of car-places of storage (accepted for repair and ready for delivery) is determined at the rate of three car-places per one working post according to the formula:

The number of car-storage places of a road service station is determined by the formula:

The number of places for storing cars in the open parking lot of the store is determined by the formula:

where D 3 - the number of days of car stock in the store; usually take

d WORK.M - the number of days the store is open.

The number of car spaces for staff and clients in an open parking lot (located outside the station) is determined by the formula:

3. Equipment selection

The requirements for two-post lifts are best met by the following:

- Two-column lift Stankoimport PGN2-4.0(B);

- Two-column lift Peak 208;

- Two-column lift LAUNCH TLT235SB;

- Lift Peak 212.

We will choose a specific model of the lift by determining the value of the compliance of a piece of equipment with the requirements,% according to the formula:

, (3.1)

where - the value of satisfaction of a piece of equipment according to the k-th indicator;

- weight of the k-th indicator, %.

The main technical characteristics of two-post lifts, as well as the values ​​​​of the quantities included in the formula (3.1) are given in table (3.1).

Table - 3.1- Technical characteristics of two-column lifts

k-value	Weight, bk, %	Two-column lift Stankoimport PGN2	Two-column lift Peak 208
		Indicator value	Ac satisfaction value	Indicator value	Ac satisfaction value
Load capacity, kg
Power, kWt
Distance between racks, mm
Lifting height, mm
Mass of the device assembled, kg
k-value	Weight, bk, %	Two post lift LAUNCH TLT235SB	Lift Peak 212
		Indicator value	Ac satisfaction value	Indicator value	Ac satisfaction value
Load capacity, kg
Power, kWt
Distance between racks, mm
Lifting height, mm
Mass of the device assembled, kg

Based on the data in table (3.1) according to the formula(3.1) we have the opportunity to determine the value of the compliance value of a piece of equipment with the requirements.

So, for the lift Stankoimport PGN2 we get:

50 1+10 1+15 1+10 1+15 0,9=98,5

for lift Peak 208 we get:

50 0,9+10 1+15 1+10 0,9+15 1=94

for lift LAUNCH TLT235SB we get:

50 0,9+10 1+15 0,8+10 0,9+15 1=91

for lift Peak 212 we get:

50 1+10 0,9+15 1+10 1+15 0,8=96.

Table 3.2 - Compliance values ​​for two-post lifts with the requirements

Stankoimport PGN2

From the analysis of Table 3.2 it follows that the requirements for two-post lifts are more consistent with the two-post lift Stankoimport PGN2.

Equipment used in this area for the repair of car bodies.

Figure 20 - Two-column lift Stankoimport PGN2

A car lift is a special equipment for facilitating the repair and maintenance of vehicles, designed to lift cars and hold them in a raised position at a certain height, can be used in conjunction with other equipment and tools, as well as to save space in car workshops and garages.

Table 3.3 - Technical characteristics of the lift Stankoimport PGN2

Figure 21 - Stand for straightening car bodies PROFESSIONAL KS-105 P-10 SIVIK

Stapel - equipment for restoring the frame and geometry of the car body, a device that allows you to straighten the body to the standard parameters by applying multidirectional efforts.

Table 3.4 - Technical characteristics of the stand for straightening car bodies PROFESSIONAL KS-105 P-10 SIVIK

Figure 22 - Spotter VS-6

A spotter is a contact welding device. In fact, the spotter is a welding machine, the principle of which is based on the emission of a significant amount of thermal energy at the point of contact of the materials to be welded during the passage of current.

Table 3.5 - Specifications of Spotter VS-6

power, kWt
Welding current, A
Voltage, V

Figure 23 - FORCE 905M4 Body Vacuum Reverse Hammer

Its purpose is to correct small dents on the pillars, sills, arches, i.e., in areas where there is no access from inside the body.

Table 3.6 - Specifications of FORCE 905M4 bodywork vacuum breaker

Figure 24 - Rubber spinning hammer MATRIX 10986

Steel balls and fine lead shot inside the case dampen rebound after impact.

Table 3.7 - Specifications of the MATRIX 10986 rubber freewheel hammer

Figure 26 - Clamp for straightening the body FORCE F62502

Table3.9 - Specifications of FORCE F62502 body straightening clamp

Figure 27 - OMAS TRK1205 hydraulic reverse action coupler

Table 3.10 - Technical characteristics of the OMAS TRK1205 hydraulic reverse action tie

Figure 28 - Hydraulic stretcher TORIN TRK0210A

Table 3.11 - Technical characteristics of hydraulic stretching TORIN TRK0210A

Figure 29 - Measuring system for body repair TROMMELBERG EMS-1-A-Light electronic

Table 3.12 - Specifications of the measuring system for body repair TROMMELBERG EMS-1-A-Light

Figure 30 - J-T16 Pneumatic Random Orbital Sander

Angle grinder with small circle diameters (115, 125, 150 mm) is designed for grinding and other similar work, and with large circle diameters (180, 230 mm) for cutting.

Table 3.13 - Specifications of J-T16 Pneumatic Random Orbital Sander

Figure 31 - Clamp for straightening the body FORCE F9M1604 with a loop

A clamp is installed at the repair site to carry out repair work.

Table 3.14 - Specifications of FORCE F9M1604 body straightening clamp with loop

Figure 32 - Professional hydraulic pump MATRIX 51325

It is intended for creation of pressure in systems with a hydraulic drive.

Table 3.15 - Technical characteristics of the professional hydraulic pump MATRIX 51325

Figure 33 - Straightening hammer FORCE 9M1501

Designed to repair dents and other defects on metal surfaces and to clean up corrosion.

Figure 34 - Leveling support FORCE F68354

Designed to support a sheet of metal from the inside during straightening.

Figure 35 - Leveling canvas

Designed for sheet metal work. Also for filing soft materials where high material removal rates and good surface finish are required.

Figure 36 - Professional figured hole punch

The puncher is intended for a punching of openings manually.

Figure 37 - JONNESWAY AB010002 047652 windshield removal kit

Figure 38 - A set of mandrels and a blade ...

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Abstract on the topic:

"Body and Cabin Repair"

Is done by a student

3 courses 33-AK group

Speciality:

Maintenance and car repair. and tr-a

1. Defects of bodies and cabins…………………………………………3

2. Technological process of repair of bodies and cabins……………. 4

3. Repair of equipment and mechanisms of the body and cabins………….. 6

4. Repair of non-metallic body parts……………………. 6

5. Assembly and control of bodies and cabs………………………………….. 7

REPAIR OF BODIES AND CABINS.

Defects of bodies and cabins.

Typical defects in body parts, cabs and plumage (Fig. 1.) Are corrosion damage, mechanical damage (dents, breaks, tears, bulges, etc.), violation of geometric dimensions, cracks, destruction of welded joints, etc.

Corrosion damage is the main type of wear of a metal body and cabins. Here, an electrochemical type of corrosion takes place, in which the metal interacts with an electrolyte solution adsorbed from air. Corrosion develops especially strongly in places that are difficult to access for cleaning, where moisture periodically getting into them persists for a long time, and, due to an increase in ambient temperature, intensification oxidation reactions. Corrosion damage also occurs as a result of contact of steel parts with parts made of duralumin, plastic, wet wood and other materials.

Cracks occur as a result of metal fatigue, a violation of metal processing technology, the use of poor shaft quality, defects in the assembly of units and parts, insufficient structural strength of the unit, as well as in places subject to vibration.

Destruction of welded joints occurs as a result of poor-quality welding, exposure to corrosion, vibration and stress during normal operation of the vehicle or as a result of accidental damage.

Mechanical damage (dents, distortions, breaks, etc.) are the result of overstressing of the metal as a result of impacts and bends, as well as due to loose connection of parts.

A

Fig.1. Characteristic damage :

A -all-metal body car :

1 - front and rear windshield openings;

2 - doorways;

3 - racks under the roof;

4 - front and rear spars;

5 - left and right thresholds of the base;

6 - bottom;

7-left and right rear mudguards

8 - violation of geometric dimensions;

9 - top and bottom, respectively, of the left and right rear mudguards;

10 - left and right front mudguards;

b - truck cab :

1 - destruction of welding seams; 2 - breaks; 3 - dents and bulges; 4 - deflection and distortion of the racks; 5 - holes; 6 - corrosion; 7-cracks

Technological process of repair of bodies and cabins.

The technological process of body and cab assembly repair includes dismantling, complete or partial removal of old paint, troubleshooting, repair of components or their replacement, assembly, painting and quality control.

Dismantling of bodies and cabins is carried out in two stages. This is the dismantling of all parts and assembly units installed on the inside and outside of the bodies and cabs, followed by disassembly of the body for repair after removing the old paintwork and identifying all its defects. Since in most cases all-metal bodies of bodies and cabs are one-piece (connected by welding), the body is not completely disassembled into panels and parts. It is carried out only to such an extent that it is possible to make a defect and, if necessary, replace or repair the elements of the body that form the frame.

Depending on the economic feasibility of repairing bodies and cabs, various methods are used to eliminate defects present on their surfaces.

The greatest labor intensity and cost of repairing bodies and cabs is the work to eliminate defects on their all-metal welded bodies. Repair of a body hull with various defects includes straightening panels, removing damaged sections of hulls, eliminating cracks and tears, fixing DRD in place of removed panels, forging and cleaning old seams, final straightening and leveling surfaces.

Irregularities in the panels are leveled by spraying powder plastics or epoxy compositions. To level dents in hard-to-reach places, a Tool of various shapes is used (Fig. 2). The bent end of the mandrel is inserted into the hole of the inner panel and the wrinkled surface is leveled by hammer blows on its handle. To eliminate shallow shallow dents, a hole with a diameter of 6 mm is drilled in it, into which a rod with a curved end is inserted and the concave part of the panel is pulled out to its normal position. The hole is then sealed with solder or epoxy.

Rice. 2. Dent Removal Tool Set:

1...6 - hammers; 7 and 8 - mallets; 9 - mandrels (spoons)

Editing panels with emergency damage provides for work on stretching, leveling, squeezing and knocking out deformed parts of the body or cab to give them their original shape and size. When performing these operations, it is necessary that the tensile force be applied at the same angle at which the force that caused the damage was applied. In order for the tension to be controlled, an opposing force must be applied opposite the point of application of the tensile force. When performing these works, it is necessary to control the stretching process, as well as possible accompanying deformations caused by the tensile force.

Editing emergency bodies and cabs is performed on stands (Fig. 3) using a set of devices (Fig. 4). Tensile and compression forces are created by working cylinders 1, 3 (Fig. 3), in which the liquid comes from the pump. For editing the body 4 set on stands 6, which are fixed on the base frame 2. The power transverse pipes rest on the supports, which are fixed with the jaws of the clamps to the stiffening ribs of the body sills. The fastening of the latter to the frame is performed by braces 5. Deep dents are eliminated by preliminary editing (Fig. 4, b) bends (Fig. 4, V) and distortions (Fig. 4, G). Since cracks or gaps may form during the straightening process, which must be eliminated in the future, straightening is carried out before welding.

Removal of damaged sections of bodies and cabs perform gas cutting, electrified milling tool or pneumatic cutter. The advantages of a pneumatic cutter are high labor productivity (0.08 ... 0.1 m/s) compared to gas cutting (0.02 m/s) and better edge quality at the cutting points. Defective areas are marked with templates and chalk, and then removed. When removing defective sections of the body or cab, it is necessary to protect the body from geometry distortion due to the weakening of its rigidity and under the action of its own weight.

Cracks and breaks in the body of bodies and cabs are eliminated by semi-automatic arc welding in carbon dioxide or gas welding. When repairing, preference is given to welding in a carbon dioxide environment, since the productivity of this process and the quality of the weld are higher. Welding is carried out by semi-automatic devices powered by direct current sources of reverse polarity with a power of 40 A and a voltage of 30 V, using electrode wire Sv-08GS or Sv-08G2S with a diameter of 0.7 mm. To limit the propagation of a crack during welding, its ends must be drilled with a drill with a diameter of 8 mm.

Gas welding eliminates cracks and gaps in panels made of sheet steel 0.5 ... 2.5 mm thick, with VSM-53 or GS-53 burners with tips No. 1 (for sheets with a thickness of B.5 ... mm) and No. 2 (for sheets 1.0 ... 2.5 mm), using for this wire Sv-08 or Sv-15 with a diameter of (0.5L + 1) mm, where h is the thickness of the metal being welded. So that the part does not lose its willow shape when heated, first welding is carried out at separate points with an interval of 10 mm, and then, as necessary, individual sections are welded with a continuous seam from the ends of the crack to the middle.

Fig.3. Stand for editing the car body:

1,3 - working cylinders;

2 - frame;

4 - body;

5 - bracing device;

6 - stand

Production of an additional repair part they start with straightening the steel sheet, cutting it and cutting blanks according to the markup. After it, the part is bent or molded on special equipment, the finished parts are cut, drilled, straightened and cleaned. The material for the manufacture of the repair part is thin-sheet cold-rolled mild steel with a thickness of 0.7 ... 1.5 mm.

Rice. 4. Devices for editing deformed body area:

A- a set of devices for eliminating distortions and kinks;

b, V And G- use of tools for editing;

1 - mandrel for drawing concave parts;

2 And 3 - self-locking hydraulic clamps;

4 - mandrel with teeth for gripping the straightened panel;

5 - pump;

6 - double grip;

7 – tension cylinder with pulling device;

8 – tension cylinder with grips;

9 - correct device

Forging and cleaning of welded seams necessary to strengthen the welding site and give it the required profile. It is performed with a pneumatic hammer using a set of supports and strikers. After forging, the welding spots are cleaned with an abrasive wheel installed in pneumatic or electric portable machines.

Final editing and straightening body panels and cabs is designed to ensure assembly accuracy and remove small dents and bulges remaining on surfaces. Straightening is performed by a pneumatic straightening device or manually. Repair weld damage.

Repair of equipment and mechanisms of the body and cabins.

Fittings of bodies and cabs include power windows, locks, door stops, door hinges, hoods, etc.

Power windows may have the following defects: cracks and broken parts; skew and deformation of clips, frames and guides; loosening of rivet connections; damage to rubber seals; parts corrosion. Power windows and glass fastening mechanisms are subject to disassembly, washing, flaw detection, repair and assembly. In case of fault detection, the following are rejected: parts with broken parts; springs that have lost their elasticity; clips with worn glass, not amenable to compression; rivets that cannot be tightened; damaged rubber seals and other parts with wear on surfaces that affect the normal operation of the mechanism. Cracks in the parts are eliminated by welding, followed by cleaning of the welds, the curvature of the parts is straightened in a cold state.

Door locks may have the following defects: cracks and breaks, damage to the threaded holes, corrosion on the surfaces of the part, weakening of the springs and rivets fastening the parts, wear on the surfaces of the parts. Repair of locks consists in their disassembly, washing in kerosene, defect detection, restoration of damaged parts, assembly and adjustment. Parts that have deep traces of corrosion, worn surfaces and breaks, springs that have lost their elasticity are subject to rejection. Cracks in the lock body are welded. Broken off screws in threaded holes are removed. The damaged thread in the hole is welded, the welding spot is cleaned flush with the base metal, the hole is drilled and the thread is cut in accordance with the size on the working drawing. Minor deposits of corrosion on the surfaces of parts are cleaned with a scraper or sanding paper and washed off with kerosene.

door hinges may have defects: cracks and breaks, wear of holes and axles, curvature. Worn door hinge pins are replaced with new ones. Cracks and hole wear are eliminated by welding followed by machining. Worn holes for the hinge axis are expanded to the repair size, and the curvature of the hinge is eliminated by editing.

Repair of non-metallic body parts.

At car manufacturing non-metallic materials are widely used: wood, plastics, synthetic leather, glass, rubber, etc. Most of the parts made from these materials cannot be restored during repair, but are replaced with new ones made at a repair company or manufacturer.

Wooden parts of the platform and body are made from lumber coniferous species (pine, spruce) having humidity no more than 18%. The main defects are breakages, cracks, spalls, hole wear. Parts that have destroyed spikes or sockets for spikes are replaced with new ones. The wooden parts of the body platform are repaired by increasing them in length or by replacing unusable boards. Boards or bars are cut into blanks of certain sizes, planed from all sides, ends are cut, lugs, grooves are cut, holes are drilled, etc. For gluing wooden parts, phenol-formaldehyde adhesives such as VIAMB-3 and casein are used. The sequence of work: the surface intended for gluing is treated so that the parts fit snugly against each other and ensure that the adhesive film is uniform in thickness; the glue is applied with a brush on the surfaces to be glued (the exposure time in air for the VIAMB-3 glue is 4 minutes); assembly exposure of parts under pressure of 0.2 ... 0.3 MPa at a temperature of 16 ... 20 ° C for 5 hours; holes from fallen knots, bolts, screws are sealed with wooden cylindrical inserts from the same type of wood as the part being repaired on the glue, and the cracks are filled with mastics, wood putty, resin glue, or by placing wooden inserts on the glue, tightly fitted in place divided crack.

sheathing textile materials or leather substitutes during the repair of cars are replaced with a new one, since during operation the material ages, loses elasticity and other physical and mechanical properties.

Cabin and body glass may have scratches, turbidity, yellowness, iridescence, brush wear and other defects. Windshields and side windows with yellowness, iridescence and wear from brushes are rejected. Risks and scratches are eliminated by grinding, followed by polishing. The glass to be restored is cleaned of dirt, dust and grease. The areas of glass marked with chalk are polished with a felt upholstery of the circle, on which a layer of paste is applied, which is an aqueous solution of pumice, with a circle rotation frequency of 300 ... glass with an aqueous solution of crocus or polyrite with a circle rotation frequency of 700 ... 800 min - "until the required transparency is obtained. After processing, the glass is degreased.

Assembly and control of bodies and cabins.

WITHassembly of bodies and cabins when repairing cars, they perform in the following sequence:

before painting, all parts and assembly units to be painted together with the body (doors, hood, plumage, trunk lid, etc.) are installed on them, maintaining the required gaps between mating parts;

after applying paint coatings, installation of the ceiling, sidewalls and interior trim panels of doors, windows, seats, noise and heat insulating gaskets, door seals, electrical equipment, instrument panel, system parts ventilation and interior heating, etc.

Subject to control: geometric deviations in the dimensions of the arrangement of groups of holes, interconnected functionally, using control and measuring equipment for this; openings of bodies and cabs and interfaces are controlled by templates according to the shape of the mating part; tightness and dust tightness of the body and cab. The tightness of the assembled body is checked in sprinkling installations at a water pressure of 2 kgf/cm2 for 6 minutes, while the penetration of water and the formation of condensate in lighting and signaling devices are recorded. The tightness of the door to its opening is determined by rubbing the seals with chalk. When the door is slammed, a uniform imprint of chalk should remain on the body or cab. Adjustment of the tightness of the door seals is achieved by moving the latch of the lock.

Deviation of the geometrical parameters of the body from the regulated values.

The car body has elastic properties, and with an increase in the length of the body, these properties increase. This affects the geometrical parameters of the body the stronger, the greater the overhang of the front of the car. The high mass of the nodes located in the front of the car (from the front of the body to the place where the front clamps for attaching the car are installed) pulls it down. If you dismantle the nodes located in this place, the front will rise slightly. The value of such a kind of "spring travel" should be indicated in the sheets for monitoring the parameters of the body, carried out by means of a specific universal measuring system. The points to be controlled and additionally specified for the case of dismantling vehicle units are usually located at the points of attachment of these units.

What is the amount of "spring travel"? In general, the difference in the position of the base points of the body in height for installed and dismantled units is 3-5 mm. Some manufacturers of measurement systems provide information on inspection sheets, others provide it during training or provide it in the service manuals of their systems. Meanwhile, this figure has recently been declining. Since the bodies have been made from high-strength steel sheet and extruded laminates, their rigidity has increased. Studies show that in modern passenger cars, the "spring stroke" does not exceed 1-2 mm. Exact knowledge of this parameter can only be given by practice.

Methods for restoring the shape of the body.

Elimination of deformations in body parts by straightening.

To correct dents and restore the shape of the surfaces of body elements, a hand tool is used, presented in the design part of the graduation project. A large range of straightening hammers involves the use of one or another hammer, depending on the nature of the dent and the shape of the surface. A number of hammers have a polished head, which makes it possible to achieve high cleanliness of dressing, and in some cases to repair damage without destroying the paintwork.

Anvils and shaped plates serve to support the sheet during the straightening of the dent with a hammer. The shape and dimensions of the plates and anvils are made taking into account the most common curvature of body parts and make it possible to use them when restoring various parts of the body.

The levers are designed to correct various dents. The design of the levers and the length of some of them provide for their use in hard-to-reach places through technological windows and holes in body parts.

Restoring the shape of body parts using a straightening tool.

Editing of bulges is performed in a cold or heated state. The elimination of bulges in the cold state is based on stretching the metal along concentric circles or along radii from the bulge to the undamaged part of the metal (Fig. 1). When editing, a smooth transition is formed from the highest part of the bulge to the panel surface surrounding it. To do this, in the direction from the metal surrounding the bulge to the curved part of the surface, a successive series of blows in a circle is applied with a hammer. As the hammer approaches the border of the bulge, the impact force is reduced. The greater the number of circles on the panel during straightening, the smoother the transition from the bulge to the undamaged part of the metal will be.

Rice. 1 Elimination of bulges in body panels without heating:

a - sections of the panel with a bulge, b - diagram of the direction of blows with a hammer (indicated by arrows); 1 - bulging; 2 - panel; 3 - sections of the panel to be stretched by straightening with a hammer; 4- curvature of the panel after straightening the bulge

Editing of deformed surfaces on a straight section of the front panels using a base plate and a mallet is shown in fig. 2, a. Correction of deformations on parts with non-circular surfaces is performed using a mallet and shaped plates or anvils of a special profile (Fig. 2, b). On fig. 2, c, shows the process of straightening minor dents on the front panels of the body, such as the roof, doors, hood, trunk lid, fenders, etc. The sequence for correcting dents on body parts with a rounded front surface is shown in fig. 1.39, city

Rice. 2. Restoring the shape of parts using a straightening tool:

a - elimination of deformations in the straight sections of the front panels; b - correction of deformations on parts with non-circular surfaces (the dotted line shows the original shape of the original part);

c - elimination of minor dents on the front panels of the body; d - elimination of dents on the front parts with a rounded surface (the numbers indicate the sequence of hammer blows)

Significant plastic deformation, which occurs when stretching the metal to eliminate the bulge by straightening in the cold state, increases the true surface of the metal in the restored area and degrades the resistance of its oxide film. As a result, the corrosion resistance of the metal deteriorates. Therefore, the editing of uneven (wavy, small concave surfaces) body panels and plumage is carried out without hardening and increasing the metal area using a base plate 2 and a special hammer 1 (Fig. 3), which has a notch on the working part.

Rice. 3. Straightening of small deformed sections of panels:

a - a diagram of the straightening process; b - defective area after straightening.

When removing dents in this way, the metal is not stretched, and the length of the panel 3 is restored to its original shape and size. To restore the surface of body parts in easily accessible places, various straightening tools are used in accordance with the curvature of the restored profile of the part, i.e., taking into account radii, transitions of various curvature and stiffeners. On fig. 4 shows the options for using shaped plates, anvils, mandrels and a straightening hammer when restoring the surface of the front wing of the body in section A-A.

Rice. 4. Straightening the surface of the body in an easily accessible place (front fender) using various straightening tools

Dents in body panels and plumage, in which the metal is not stretched after impact, are most often leveled by extrusion or pulling of the concave section until it is given the correct curvature and, if necessary, by subsequent straightening of the extruded surface. The bulges formed in the panel during high tension of the metal cannot be straightened by straightening, since in the process of straightening the top of the bulge may lose stability and move to the other side of the sheet. This circumstance, taking into account that in order to eliminate the bulge, it is necessary to deposit excess metal, determines the method of its editing.

Hand tools are used to correct dents and restore the shape of the surfaces of body elements.

Electrical alignment.

With this method, the deformed part is heated by passing an electric current of high strength and low voltage. Recall that spot welding easily heats red-hot metal compressed by two electrodes. The general principle of operation of all industrial spot welding machines is the rapid local heating of the metal in contact with the carbon electrode installed in the holder. Depending on the type of holder and the different installation of the electrodes, welding can be carried out with points, straight stitches, curved stitches. One wire supplies voltage to the electrode holder, and the second connects the sheet to the mass to eliminate the bubble in this way, preparatory work is carried out. First straighten the deformed part using conventional tools. If the dents are small, you can do without editing. Paint is removed from the processing sites (it is an insulator). The operation can be performed both manually with a scraper, and with a grinder, they also clean the junction with the ground.

An electrode is installed in the holder, corresponding to the work performed, if this is provided for by the design of the apparatus: an electrode with a flat or convex tip to perform shrinkage points; electrode with a sharp tip for shrink stitching. The voltage is regulated on the secondary winding.

In repair practice, two main types of devices are used to heat the dressing zone:

Apparatus with built-in sponge consists of an electrode holder, the electrode itself and a power cable that feeds the electrode holder. The wire is connected to an arc welder, usually using coated electrodes, and is connected in place of the wire that feeds the standard electrode holder. The copper electrode is installed inside the electrode holder and passes through the central hole of the annular jaw, installed in the body of electrically insulating material. A separate wire connects the metal being processed to the ground.

For thin sheets, a minimum current of 40 A is sufficient. When processing thicker sheets or aluminum, the current is increased. The sponge is moistened with water and installed in the housing. The role of the sponge is to limit the heating zone and cool. The electrode is briefly brought into contact with the metal in the dressing zone. Each contact of the electrode causes local heating of the metal to a red color as a result of the resistance of the metal to the passage of current. If the apparatus is not moved to the sides, then hot spots are obtained. If the apparatus is moved, shrink rows are obtained. You can not keep the electrode in contact with the sheet for a long time, so as not to flash it through.

Other type of device With extended sponge. It contains an electrical transformer with a current regulator, a silon wire with an electrode holder and an electrode, a power cable connecting the apparatus to a source of electric current. The operating voltage of this machine is smaller and comparable to the voltage of the spot welding machine. The secondary winding current regulator is set to a position corresponding to the type and thickness of the metal being processed. After each contact of the electrode with the sheet, the heated zone is wiped with a damp sponge. Depending on the nature of the deformation, heating is carried out in points or rows. First, the metal is cooled around the contact points, and then their tops.

In a cold state, the bubble can be removed only if the bubble size is small and the metal is not strongly elongated. To do this, the manual anvil is replaced with a soft support, made, for example, of hard wood, processed with a rasp in the shape of the contour of the part, or cast and lead. By blows of a straightening hammer, a metal screed resting on a support is produced, starting from the edges of the bubble and moving towards the center.

When the sheet is straightened, the support undergoes deformation, which contributes to the equilibrium distribution of metal molecules. The result depends on the degree of metal drawing. To obtain a suitable result, it is necessary that the metal of the sheet be sufficiently ductile, and the bubble should have a slight bulge.

Napayka.

If impacts cause damage in hard-to-reach places of the body, it becomes necessary to disassemble, which is long and troublesome.

Sometimes this can be avoided. In order not to make a big disassembly for the sake of eliminating a small dent, you can level the dent in another way.

The oldest method that can be used for such cases is tin soldering.

The technology is as follows. After cleaning the surface of the sheet, it is tinned, and then the dent is sealed with tin solder. The solder is filed (with a file with a bent handle), then the surface is polished.

The solder coating has sufficient hardness and adhesion. But there is a drawback: the need for heating - tin solder melts at a temperature close to 250 "C.

Puttying.

There is another way to seal dents, which consists in the use of putties based on polyester resins, applied to a carefully cleaned sheet surface.

Putties quickly harden and do not shrink. The surface of the fillers is also filed and polished. The durability of putties applied in most cases depends on the thoroughness of application and adhesion (adhesion) of the first layer.

Hood.

If hollow body parts have undergone deformation, they are most often replaced. These details include: thresholds; body pillars; wings, doubled and hard to reach from the inside; traverse and some others. But depending on the circumstances, including material ones, in most cases the elimination of the deformation is possible from the outside with the help of so-called nails welded to the dent. The most commonly used method and a set of tools called a nail puller. What is its essence? This is a tool kit equipped with a transformer similar to that of spot welders. Power is supplied by electric current with a voltage of 220/380 V. The nail welding machine is similar to a large gun, at the end of which there is a copper nozzle-clamp, nails are placed in it, and a ring is installed on the edge. Nails are steel cylindrical rods with a diameter of 2 to 3 mm, depending on the type. The end of the rod forming the head is welded to the cleaned area of ​​the deformed body part. Structurally, the dressing tool is a cylindrical rod along which the load slides. At the upper end of the rod there is a stop, and at the lower end there is a chuck for clamping nails.

The preparation of the surface of the deformed part is that it is cleaned of paint and other insulating products in order to expose the metal of the sheet and ensure good contact. Next, editing begins.

A nail is fixed in the nozzle of the gun, the gun is connected to a power source. Set the average shutter speed of the pistol time relay. The holding time determines the welding time, i.e. the time of passage of the electric current.

It is best to conduct several test welds before starting to edit the body to determine the best mode. Tests are carried out on a sheet of the same thickness and of the same steel grade as the part sheet.

The gun is attached to the deformed zone and welding is started from the edges of the dent, if it is extensive. The gun is pressed so that its ring comes into contact with the sheet and provides the passage of current for welding. After welding the nail, the gun is retracted. Then a small nail puller cartridge is inserted onto the nail and clamped, several hoods of the deformed area are made with the help of a nail puller, striking the stop with a load.

To complete the editing, you can continue the extraction manually (by the nail), without hitting the load and simultaneously knocking out along the edges of the dent using a forging or ironing hammer. This method gives the best results. After straightening, the nails are boiled using the same gun.

Nowadays, the so-called spots. This is an electrode that is temporarily welded to the metal for subsequent drawing. In fact, this is the same nail puller. There are many options for such a device. It is possible to weld an electrode with metal, weld transition elements of various shapes. The tip is equipped with a hook or collet. The pulling force is generated by a lever or reverse hammer.

By the way, with a carbon tip spotter, you can anneal and upset the bulges or “poppers” described above. The main value of the method is the ability to work from the front side, it is often possible to do without disassembling the interior, which saves time and money.

Power equipment (jacks) . The use of power equipment when straightening bodies requires knowledge and experience. Only knowledge of technology and safety regulations will make the use of such equipment efficient and safe.

First of all, it should be noted that the force on the jack rod can reach impressive values ​​​​at the beginning of the stroke and gradually decrease towards the end of the stroke.

In each specific case, it is necessary to use such extensions and inserts that would provide the best working conditions, in other words, editing should begin even when the jack is compressed, and not when the rod ends.

It is necessary to constantly monitor the oil level in the jack. If oil leakage is observed, the seal must be replaced. The use of chain jacks requires a number of precautions to ensure they are used efficiently and do not cause injury to the operating personnel. When securing chains, the following circumstances must be taken into account. The dressing angle must be opposite to the angle formed as a result of deformation. To meet this condition, the chains should be placed perpendicular to the damaged area. The angle formed by the tensioned chain must in all cases be close to a straight line. A pronounced obtuse angle does not ensure the accuracy of the dressing direction, and an angle that is too sharp limits the stroke of the jack.

Proper placement of the jack inside the chains also determines the quality of the stretch. The angle on one and the other side of the jack (between the jack and the chain) must be symmetrical and within 30-60 °C with the chain attachment base.

As with direct stretching, stretching starts with a minimum jack stroke to utilize the full force and maximum jack stroke.

Straightening with a hydraulic square is usually carried out on a bench or on the floor of a workshop, while keeping in mind the following:

Before any stretching, first of all, the square is fixed,

placing it on the central axis perpendicular to the deformed area.

The chain is placed in the center of the deformed area and attached to it with

The chain is attached to the vertical lever perpendicular to the square, exactly

observing the straightening axis and taking into account that the maximum power reserve of the jack is provided on the jack head.

As the height of the chain fastening on the lever increases, the jack force smoothly

decreases.

The minimum tensile force is generated at the upper end of the vertical

Stretching begins with a minimum stroke of the jack rod.

The vertical arm forms an acute angle with the horizontal elbow, which allows it to be moved the amount needed for straightening without shortening the chain.

If the result of a collision with a car is a significant deformation, it is first necessary to remove the mechanical units, only in this way can the folds be carefully straightened and parts that cannot be repaired can be replaced. In addition, this will remove residual stresses that may arise and remain after straightening. When the car is moving, residual stresses can cause stresses in the mountings of shock absorbers and bushings, and sometimes breaks.

But in some cases, pre-straightening the body with installed mechanical units can facilitate access to the units to be removed, for example, to the propulsion unit in cars with front-wheel drive, to the front or rear axle. In this case, care must be taken to replace the mounting bolts and shock absorbers. This operation is performed on the stand.

If a blow to the front or rear half-axle caused deformation of the base of the body, it is also possible to straighten the body by fixing (hooking) the stretching mechanism to mechanical units, such as wheel rims or suspension arms that have received deformation. Editing is done in the direction directly opposite to the impact. Performing such an operation is possible only if the blow fell directly on the front or rear half-axle and its replacement is necessary.

It is also necessary to replace the ball joints and steering rods without fail. Straightening with a jack or other hydraulic mechanism based on a jack is used to restore the shape or straighten a deformed part. However, when starting work, one should not forget that with a very sharp editing of a body part, deformation of the adjacent deformed zone may occur. Therefore, when stretching, i.e., simultaneously with the action of the jack, it is recommended to accompany the restoration of the linearity of the body by tapping out the folds. And after drawing out with a jack, it is necessary to remove all internal stresses by tapping (using a straightening hammer) the entire area that has been straightened.

In order to be sure that there will not subsequently be a reverse movement of the straightened sections of the body due to residual stresses, the surface is tapped through the wooden lining in the direction of impact. If at the same time the straightened body does not change its shape, then the editing operation was performed correctly. Otherwise, you should edit again until the geometry is within the tolerances specified by the vehicle manufacturer.

If the car received side kick , this causes deformation of the base of the body, accompanied by a decrease in the length of the body on the side of the damaged surface, which is easy to determine. When editing on the stand, the performer must take this circumstance into account. In practice, straightening is carried out by stretching in two directions simultaneously: lateral and longitudinal, which makes it possible to restore the original geometry of the body base.

An example of the restoration of the side surface is the alignment of the middle rack, which is wrapped with a pull chain. To protect the rack from damage and evenly distribute the force between the rack and the chain, a wooden plank is laid.

Longitudinal stretching, performed simultaneously with lateral stretching, can be performed in various ways. If the deformation is concentrated in the lower part of the body, the base is straightened directly, fixing the clamps to the flanging of the thresholds. The jack is placed between two clamps and under pressure moves them in the longitudinal direction as the simultaneous lateral stretching is carried out. If the deformation is concentrated in the upper part of the body, stretching is carried out in the longitudinal direction from the front and rear parts of the body.

Work on straightening and checking new spars must be carried out on precision equipment.