Extractor for bearing rollers

Contents

Contents

Task

Introduction

1. Analysis of operation and description of main causes of loss

node serviceability

2.Select how to restore a part

3 Development of Job Instruction for Doubler Roller Recovery

T30.37.

4. Determining the Cost of Restoring a Part

5 Development of extractor for K- tractor roller bearings

5.1 Description of the accessory and operating principle

5.2 Calculation of extractor screw for K- tractor roller bearings

Literature

Application

Introduction

Repair production is a special type of partial production of machines or equipment, characterized by the unequal strength of their parts and the instability of adjustments, that is, having elements of different service lives in their original composition. It is organized in the field of consumption of these machines and equipment and consists in the periodic reproduction of their individual elements partially lost due to wear and tear.

When defecting parts, it was revealed that the number of suitable parts is 20... 40%, defective - 10... 20%, and suitable for restoration 40... 60%. At the same time, restoring parts is cheaper than buying new ones, and the resource of restored ones is equal to the resource of new parts.

Course work consolidates, deepens and summarizes the knowledge gained by students during lecture and practical classes on the basics of car production and repair technology. Course work should teach the student to use reference literature, state standards, tables, skillfully combining reference data and knowledge obtained during the course study.

During course work, special attention is paid to the student's independent creativity in order to develop his initiative in solving technical and organizational problems, as well as a detailed creative analysis of existing technological processes in modern repair production.

Analysis of operation and description of the main causes of unit failure

Doubler rollers operate under constant static wear loads. In this regard, they are made with high-strength and wear-resistant 50X steel.

Main defects encountered during operation of rollers:

1. wear of surface of slot for retainer;

2. wear of outer surface under crankcase;

These defects result from prolonged operation without repair or replacement by abrading forces.

Selecting How to Restore a Part

When recovering these defects, it is preferable to use methods of spraying or electrolytic deposition of metals, followed by grinding the surface 2 and the bore of the surface 1 with a shaped cutter.

When analyzing the methods of electrolytic deposition of metals, we conclude that it is more effective to use GVPHI - a galvanic wear-resistant chromium coating for the following reasons:

• type of base metal - steel of all grades and iron;

• view of recovery surface - external and internal cylindrical surfaces;

• the thickness of the extension is 0.01... 0.5 mm, which is enough to restore the part;

• coating - any types of loads;

• wear resistance ratio reaches 23, and in other ways 0.85... 1;

• endurance coefficient - 0.7, in other 0.62... 0.65;

• adhesion coefficient - 0.9, in other ways - 0.55... 0.8;

• micro-hardness - 4500-12000 MPa;

• specific total capacity of expansion - 13.817.8 n-h/m2.

The essence of the restoration of parts with galvanic coatings is as follows [4].

More than 85% of tractor and automobile parts and 95% of engine parts are rejected with wear of not more than 0.3 mm. It is advisable to restore them with galvanic coatings. Consider the advantages of this recovery method over others:

the absence of thermal effects on the parts, causing undesirable changes in their structure and mechanical properties;

obtaining with great accuracy the specified thickness of the coatings, which leads to minimizing the allowance for subsequent mechanical treatment and its labor intensity or completely eliminating the treatment;

deposition of coatings with given non-constant physical and mechanical properties in thickness;

simultaneous restoration of a large number of parts (dozens of parts are loaded into the bath), which reduces the labor intensity and cost of a unit of an item;

possibility of process automation.

Electroplating technology.

The process consists of three groups of operations: preparation of parts for building up, coating and subsequent processing.

Preparation of parts. The adhesion of the coating metal to the metal of the part is due to their intermolecular interaction. Intermolecular forces appear noticeably only if the distance between atoms is not more than 5105 μm. They decrease proportionally to the third degree of interatomic distance.

The surfaces to be covered are given the necessary roughness. Various contaminants, fat and oxide films are removed from them. The metal is deposited on an active pure cathode free of foreign particles. As a result, the coating is physically spliced with the base metal so firmly that it does not peel away from the part even when it is broken and works integrally with the base metal. Failure of preparation technology reduces its adhesion and can lead to peeling away from the part.

Machining is designed to remove traces of wear from the coated surface and give it the required roughness. In the process of restoration, the parts are usually ground to roughness corresponding to the 6... 7th class, or cleaned with skin (with small uniform wear).

Washing with an organic solvent (gasoline, kerosene, etc.) is used when it is necessary to additionally clean the part from dirt and oil accumulated in depressions, holes, etc.

Insulation of surfaces of parts that are not to be coated with current-conducting materials serves to preserve geometric dimensions of surfaces, prevent loss of electric power and metal. It is carried out using permanent insulators (box, tube, washer, etc.) or insulating materials (thin rubber, sheet celluloid, insulating tape, film polymer materials, ceresin, plastisol, etc.).

Installation of parts on suspension is performed for their hanging into bath with electrolyte. The suspension design shall provide reliable electrical contact with the parts to be covered and the bath bar. Parts are arranged vertically or obliquely to remove hydrogen from surfaces.

According to the number of simultaneously mounted parts, individual and group suspensions are distinguished.

Degreasing is intended for removal of fat contaminants. This process is based on the fact that animals and vegetable fats under the influence of hot alkali break down and form soap (saponified), which is easily washed with hot water. Mineral non-washable fats, such as lubricating oils, form emulsions under the influence of alkali.

The solid film breaks and the oil is collected in separate droplets which are separated from the surface of the parts and remain in solution in a finely divided suspended state. To facilitate emulsification, special substances called emulsifiers are added to the alkaline solution. These include liquid (soluble) glass, surfactants, etc.

Degreasing in alkaline solutions can be carried out by chemical and electrochemical methods. In the chemical method, the parts are immersed in a hot alkaline solution and kept in it for a certain time.

Duration of the process (5... 60 minutes) depends on the temperature of the solution and the degree of contamination of the articles. For degreasing of steels and cast iron, it is recommended to use a solution containing up to 50 g/l of caustic soda, according to 15... 35 g/l of trisodium phosphate and soda ash and 3... 5 g/l of DS10 synthanol. To the solutions is added 3... 5 g/l liquid glass or sodium metasilicate. Approximate alkalinity of solution (pH) at degreasing of ferrous metals up to 12.

The essence of electrochemical degreasing lies in the fact that articles immersed in alkaline solution are included in the electric current circuit as a cathode or anode. Gas bubbles (hydrogen at the cathode, oxygen at the anode) are rapidly released on the surface of the electrodes. They facilitate emulsification of fats and oils, mechanically tear and remove their films, thereby accelerating the process several times. The velocity of the latter depends little on the concentration and temperature of the solution (60... 80 0C) and is determined by the current density, which is usually 3... 10 A/dm2. The more fat contaminants on the surface of the parts, the greater the current density.

To avoid various complications, either anodic degreasing should be used (3... 10 min), or combined treatment - first degrease on the cathode for 4... 5 min, and then switch the parts to the anode and degrease for 1...... 2 min. Steel plates are used as the electrode. The distance between the electrodes is 50... 150 mm.

After degreasing, the parts are thoroughly washed first with hot (70... 80 0C), and then with cold water. If it spreads evenly and wetts the entire surface of the part, rather than being collected in droplets, then the quality of the treatment is good.

Etching is intended for removal of oxide films and defective layer from coated surfaces, detection of crystal structure and increase of metal activity. It is carried out by chemical and electrochemical methods.

Chemical etching of ferrous metals is carried out in aqueous solution of sulfuric or hydrochloric acid or in their mixtures. Usually a 15... 25% solution of sulfuric or 10... 20% solution of hydrochloric acid is used. When etched in a solution of sulfuric acid, it is often heated to 50... 60 0C. The duration of the process (30 min more) depends on the surface condition of the part, the concentration and the temperature of the solution.

In repair enterprises, this method most often serves in preparing methyses and other small parts for galvanizing and cleaning the surfacing wire from rust.

Electrochemical etching should be used to accelerate the process and increase the adhesion strength of galvanic coatings. Its velocity increases tenfold and its acid consumption decreases. Solutions of acids, more commonly sulfuric, and salts of the corresponding metals, are usually used to etch ferrous metals. Parts are wrapped in bath and included as cathode or anode in electric circuit.

The most common anode etching occurs due to the electrochemical dissolution of the metal, chemical dissolution and mechanical separation of oxides from its surface by oxygen released on the anode.

In repair production, such etching is used to restore worn-out parts by ironing and chromium. During ironisation, it is carried out in an electrolyte with a content of 365 g/l of sulfuric acid (30% solution) and 10... 20 g/l of iron sulphate (FeSO4 • 7H2O). Process temperature 18... 25 0С. Parts are hung on anode rod. Cathodes are lead plates, the area of ​ ​ which is 4... 5 times the area of ​ ​ the covered surfaces. Steel parts are treated at anode current density 50... 70 A/dm2 for 2... 3 min, and cast iron - at 18... 20 A/dm2 for 1.5... 2.0 min.

Some time after the start of etching, the voltage on the bath increases and the current decreases. This is due to the transition of the metal from the active state to the passive (passivation of the surface) and is accompanied by a rapid release of oxygen. The bubbles of the latter tear off the etching sludge, and the treated surface becomes clean with a clearly identified crystal structure and a specific microrelief.

The quality of the treatment is controlled visually: the correctly etched parts are characterized by a light gray matte surface without gloss, dark spots and traces of etching sludge.

For large weight and complex configuration parts made of high alloy steels and especially hardened to high surface hardness, such etching does not always achieve good adhesion strength. Therefore, double etching is used: first in an iron chloride solution (iron electrolyte), and then in a 30% sulfuric acid solution. Steel parts are etched in the iron bath at an anode current density of 40... 80 A/dm2 for 2... 5 min (depending on the surface state of the parts), and cast iron - at 15... 20 A/dm2 for 1... 2 min.

Prior to chromium plating, the parts are anodically etched in a solution containing 100... 150 g/l chromium anhydride and 2... 3 g/l sulfuric acid, or directly in an electrolyte for chromium plating. Steel parts are processed at anode current density 25... 40 A/dm2 for 30... 60 s (the more carbonaceous and alloyed steel, the shorter the etching time), and cast iron - at 20... 25 A/dm2 for 5... 10 s. Electrolyte temperature 50... 60 0С. Coating. In the repair production of galvanic coatings, iron is most often used and less often chromium, galvanizing and nickel plating.

Chromization serves to obtain fine-grained coatings with a microhardness of 4000... 12,000 MPa with low coefficient of friction and high adhesion. Chromium is chemically resistant against the effects of many acids and alkalis, heat resistant, which provides parts with high wear resistance even in heavy operating conditions, exceeding in 2... 5 times the wear resistance of tempered steel. The highest wear resistance of the coating is obtained with a hardness of 7000... 9200 MPa.

However, chroming is an energy-intensive, expensive and low-productivity process. It is used for the following purposes:

protective and decorative chrome plating of automotive fittings, bicycles, motorcycles, wagons, etc.;

increased wear resistance and service life of presses, dies, measuring and cutting tools, friction surfaces of machine parts (piston rings, rods of hydraulic cylinders, plungers of fuel pumps), etc.;

restoration of low-worn critical parts of cars, tractors and various equipment;

high reflectance when making mirrors, reflectors and reflectors.

This process, unlike others, is characterized by the following features.

1. The main component of the electrolyte is chromic anhydride (CrO3), which forms chromic acid (CrO3 + H2O = H2CrO4) when dissolved in water. The main component in other processes is the salt of the deposited metal. Chromium precipitates only if there are a certain amount of foreign anions in the electrolyte, most often sulfates (SO4 2). It is hexavalent in the electrolyte. Divalent metallic chromium is deposited on the cathode. The mechanism of its deposition is very complex and has not yet been sufficiently studied.

2. Most of the current is spent on side processes, including water decomposition and abundant hydrogen release, as a result of which the current output of chromium is small (10... 40%). As the concentration and temperature of the electrolyte increases, the current output decreases, while when other metals are deposited, on the contrary, it increases.

3. The chromium anode dissolves during electrolysis with an anode current output of 7... 8 times the current output at the cathode. As a result, the concentration of chromium ions in the electrolyte increases continuously. Insoluble anodes made of lead or lead alloy with 6% antimony are used. When using insoluble anodes, the electrolyte is constantly depleted and must be periodically controlled and corrected by adding chromium anhydride.

Simple sulfate electrolytes No. 1.2 and 3 consisting of chromic anhydride, sulfuric acid and water are used for chromium plating.

The ratio between the concentrations of chromic anhydride CgOz and sulfuric acid H2SO4 has a great influence on the process. To deposit coatings of good quality and with the highest current output, it is necessary that it is equal to 100 (a change from 90 to 120 is allowed). For the same purpose, the electrolyte should have 1... 2% (of the amount of CgO3) of trivalent chromium ions, which are obtained by working out the electrolyte with a current density of 4... 6 A/dm2 at a temperature of 45... 50 ° C and a ratio of SK: Sa = 4... 6.

Conventional chromium coatings are poorly wetted with oils and are mined. In order to increase the wear resistance of parts operating at high pressure and temperature and insufficient lubrication, porous chrome plating should be used. Porous chromium is a coating on the surface of which a large number of pores or a network of cracks are specially created, wide enough for oil to penetrate into them. It can be obtained by mechanical, chemical and electrochemical methods.

The most widely used electrochemical method. It consists in the fact that the coating is deposited with a grid of microcracks. To expand and deepen them, the coating undergoes anode treatment in an electrolyte of the same composition as during chromium plating (the surface of the cracks is more active and dissolves much faster than other areas of chromium). Depending on the chroming mode and anode etching, channel and point porosity can be performed.

To form porous coatings, the part is chromized in a universal electrolyte at a current density of 40... 50 A/dm2, and then the polarity of the bath is switched and anode etching is carried out at the same density. Channel porosity is obtained at electrolyte temperature 58... 62 0C and etching duration 6... 9 min, and point porosity - 50... 52 0C and 10... 12 min. The anode etching is allowed to 0.01... 0.02 mm per diameter.

Porous chroming of piston rings increases their wear resistance by 2... 3 times, and the sleeve wear resistance by 1.5 times.

Machining of parts after coating. After coating, the parts are washed with water and neutralized in alkaline solutions to remove traces of electrolytes and prevent corrosion. For example, after chromium plating, they are neutralized in a solution of soda ash (20... 70 g/l) at 15... 30 C for 15... 30 s. It is especially necessary to carefully treat the parts coated in chlorine electrolytes, since the remaining chlorine ions cause intense corrosion of the coating in a humid atmosphere. To do this, they are washed and neutralized in a 10% m alkali solution at a temperature of 60... 80 ° C for 5... 10 min.

The heat treatment serves to dry or improve the properties of the coatings. Parts are dried in a drying cabinet at 50... 100 0С for 5... 10 min.

During electrolysis, hydrogen is released, which is embedded in the coating, which increases brittleness, reduces the fatigue strength of the part and the adhesion of the coating. Therefore, responsible chrome parts operating at high dynamic loads or requiring increased accuracy and dimensional stability (plunger pairs) are dewatered by heating them at a temperature of 180... 230 0C for 2... 3 h.

During machining, soft coatings are sharpened and hard coatings are ground or honed.

It is recommended to grind parts restored by chromium grinding with electrocorundum circles (24A25SM2K and 34A40SM2K) on a ceramic bond with a grain size of 25... 40 medium soft hardness. Wheel rotation speeds and parts 25... 35 m/s and 25... 60 m/min, grinding depth up to 0,012 mm, longitudinal feed 0.1... 0.3 wheel width, abundant cooling (at least 10 l/min).

Development of Job Instruction for Recovery of T30.37.114 Doubler Roller

The routing includes all major recovery operations.

The following are the initial data for the task list development:

-a part sketch showing dimensions and defects, taken into account the requirements

ESKD;

- technical conditions and instructions on defects of parts and joints during repair of the machine;

-Process list albums for parts recovery.

The doubler roller has the following defects: wear of the surface of the slot for the retainer (surface 1, wear of 1.5 mm per diameter), wear of the surface for the crankcase (surface 2, wear of 0.255 mm).

The roadmap for elimination of these defects will take the form:

1. Galvanic operation: perform the rest of surfaces 1 and 2;

2. Current operation: bore surface 1;

3. Grinding operation: grind surface 2.

1. Operation: galvanic

The galvanic coating process includes a number of operations for preparing the surface for coating (mechanical treatment, degreasing, washing, decapitation, etching, suspension of parts on the accessory, loading of parts into the bath), operations for coating the part and operations performed after coating (washing, drying, removal from suspensions, mechanical processing).

Transition 1: Increase surface 1 from diameter 16.43 to diameter 14.53 mm

We determine the current strength by the formula:

Auxiliary residence time is 0.2 min [5].

Additional time 8% of operational time, Tdop = 15.6 0.08 = 1.2, preparatory and final time Tp.z. = 10 min [5];

We determine the time norm by the formula

Transition 2: Build surface 2 from diameter 19.66 to diameter 20 mm at length 125 mm

We determine the current strength by the formula:

Time of part holding in bath is determined by formula:

thickness of the coating layer taking into account grinding allowance of 0.27 mm.

Additional time 8% of operational time, Tdop = 4.5 0.08 = 0.4, preparatory and final time Tp.z. = 10 min [5];

We determine the norm of time

Tn = 4.5 + 0.4 = 4.9 min.

The norm of time for all operation is equal to Ton = to T1 + to T2 =18+4.9=22.9min

2. Turning operation: drill surface 1 from diameter 14.53mm to 14.73mm

Processing allowance is calculated by formula [3]

It is necessary to remove 0.1 mm thick metal layer to the side. To do this, we use a lathe 162K with a shaped cutter.

In our case, the cutting depth is equal to the length of the machined surface.

We choose the feed. For steel at a cutting depth of 0.1mm, it will be S = 0.05 mm/v [3]. Determine rotation speed by formula [3]

We accept the maximum rotation speed n = 1000 min-1 for machine 162.

The main time will be determined by the formula

3. Grinding operation: grind surface 2 from diameter 20 to diameter 19.975 mm on length 125 mm

Transverse feed is taken equal to 0.04 mm.

Longitudinal feed is accepted:.

Feed is given in parts of grinding wheel width.

Since you can use different circles, we calculate the feed by

Determining the Cost of Restoring a Part

The total cost of restoring a part is determined by the formula:

The full wages of workers are determined by the formula:

Rop - workshop general production expenses, accepted 100... 150% from Spr.n, rubles. [5]

Full wages of workers are determined by the formula

1,025…1,039 [5].

Cost of galvanic works:

We accept the hourly tariff rate for the fifth category equal to Sh = 32.64 rubles.

Development of extractor for K-700 tractor roller bearings

5.1 Description of the accessory and operating principle

The extractor is designed to extrude the roller bearing of the conical two-row and roller bearing 122 (for example, to extrude the bearing from sattelites). This accessory is used when repairing the driving axle of the K700 tractor.

Extractor consists of clamp (1), tie rod (2), screw (3), rod (4), nut (5), heel (6) and ball (7) (Fig.1).

Before pressing out screw (3) is fully twisted. Then, with the help of clamps 1, the extractor is fixed and the screw 3 is swirled. The heel (6) rests against the bearing and at subsequent screwing it acts on the bearing, pushing it out of the seat. The heel 6 is stepped so that the load on the outer and inner rings of the bearings is evenly distributed. So that there is no jamming of the heel, a ball 7 is installed inside it.

5.2 Calculation of extractor screw for K-700 tractor roller bearings

The most loaded part of the extractor is the screw, since all the load is transmitted through it.

We accept the following conditions for calculations: the material of the bolt is steel 45 with a strength limit [αm] = 450MPa. External load applied to the screw is found from conditions of bearing pressing and is taken equal to F = 100kN.

We find the design strength according to the formula

Thus, in order for the screw to withstand the load when pressing out bearings, its diameter must be at least 24mm. When designing, we take it equal to 24mm

Literature

1 Complete system of machine maintenance and repair in agriculture. - M.: GOSNITI, 1985

2 V.D. Sherstobitov. Methodological guidelines for coursework in the discipline "Reliability and repair of machines" for students of the 5th year of the Faculty of Agricultural Mechanization. Kirov: RIO VGSHA, 1993

3 I.S. Serykh, A.P. Smelov, V.E. Cherkun. Course and diploma design for reliability and repair of machines 4th ed. revised and supplemented - M.: Agro-industrial publishing house. 1991.184c il.

4 Equipment and equipment for repair shops of collective farms and state farms. Directory. Colos.1975: il.

5 V.A. Matveev I.I. Pustovalov. Technical rationing of repair work in agriculture - M.: Kolos. 1979288s.: il.

6 I.S. Livitinsky. Organization of repair and design of agricultural repair enterprises. - M.: Kolos.1977.