Repair of external balance beam of tractor DT-75

Contents

Contents

Paper

Introduction

1. Structure, operation analysis and characteristics of the main

causes of loss of operability of the assembly unit

2. Structural diagram of assembly disassembly

3. Part Defect Process

4. Part Repair Process

4.1. Part Recovery Routes. Combination of defects in routes

4.2. Choosing a rational way to eliminate the main defects of the part

4.2.1. Characteristics of defects and purpose of methods of their elimination according to the technological criterion

4.2.2. Evaluation of the assigned methods of defect elimination according to the technical criterion

4.2.3. Evaluation of assigned methods of defect elimination according to the techno-economic criterion

4.3. Part Recovery Process Maps

4.3.1. Routing Recovery Process Plan

4.3.2. Selection of technological equipment

4.3.3. Calculation of main process operation modes and technical rationing of main operations

4.3.4. Execution of process documents

Conclusion

Literature

PAPER

Course work consists of 32 s. Typewritten text, 2 tables, il., Library 7 sources. Graphic part - 2 drawings. FGOU VPO Kostroma GSHA. 2011.

The main methods of part defect, selection of part recovery method, selection of main equipment operation modes and quality control of the restored part are considered in the course work.

Introduction

Improving the quality of repair of machines while reducing its cost is the main problem of repair production. In the structure of the cost of overhaul of machines, 6070% of the costs are accounted for by the purchase of spare parts, which, even in the market, remain scarce with rising prices. The main way to reduce the cost of repairing machines is to reduce the cost of spare parts. Part of this can be achieved due to careful and competent disassembly of machines and defect of parts. However, the main reserve is the restoration and reuse of worn parts, since the cost of restoring most parts, as a rule, does not exceed 2060% of the price of the new part.

In addition, the restoration of parts is one of the main ways to save material and energy resources, solving environmental problems, since the cost of energy, metals and other materials is 2530 times less than the cost of manufacturing new parts. When remelting worn out parts, up to 30% of the metal is also irretrievably lost.

In the process of restoring a part, you can not only reduce the cost of repairing machines, but in many cases also improve its quality .

The purpose of the work is development of the external balance bar repair technology

Part Defect Process

After cleaning, parts are defected to determine process state. Defective is the process of process control of joints and parts and sorting them into groups according to technical requirements. In case of defect, suitability of joints and parts for further work is determined and need for their repair and rejection is revealed.

Defection is carried out in a workshop in a special area equipped with appropriate equipment, tools, devices and equipment. Work stations of controllers are equipped with special tables, which prevent damage of work surfaces of the part.

To supply parts from the assembly and assembly plant to the work stations of the supervisors, as well as to store parts that have been defected and send them for their intended purpose without additional overloads, it is necessary to use special packaging and vehicles that prevent damage, contamination and loss of parts. Parts coming to the defect must be clean, without oil and resin stains, coke, scale, corrosion products, residue of linings and sealing pastes. Quality of evaluation is controlled by standards with a sample with permissible contamination of their surfaces, established by the OTC of the workshop. Supervisors also check the quality of disassembly, paying attention to the trace of damage to parts due to violation of the technology or disassembly techniques, improper transportation of parts, the use of an unsuitable tool, etc.

The process requirements for defects define specific instructions on the nature of the defect for each part, permissible sizes, methods of control by the necessary instrumentation, instruments and devices, as well as a conclusion on the defect, in the presence of which the part should be restored or rejected.

The surfaces are monitored in the sequence defined in the defect maps. The part is inspected and checked whether there are damages and changes in its original shape: cracks, holes, balls, bent places are noticeable, twisting, warping, raging, etc. Defects are detected by which the part is married. To avoid arbitrary evaluation of permissible or unacceptable defects, which are most common, are selected for the main item of parts, forming with permissible defects, which are approved by the CTC as standards. Parts are divided into four groups:

--- serviceable, the nature and wear of which are within the limits specified in the technical requirements and permissible without repair (restoration) in connection with both the new and the part in service (parameters meet the requirements of the technical requirements);

--- serviceable, the nature and wear of which are within the permissible process requirements for use without repair (restoration) in connection with new or restored to the nominal size of the part;

--- to be repaired (refurbished);

--- defective, which, due to technical condition, have gone beyond the limits permissible by technical requirements, and cannot be restored for technical, technological or economic reasons.

The belonging of a part to a particular group is indicated according to the system approved at the enterprise.

Suitable parts are transported to the picking compartment of the workshop, and the parts to be repaired are sent to the warehouse, which are awaiting repair (ECD warehouse), and are folded along the racks in accordance with the numbers of technological routes for their restoration.

Parts are accumulated in the ECM warehouse, which are planned to be restored centrally.

The defective parts are sent to the waste or partially used as a material for making others.

In our case, there are the following defects in the balance bar of the external balance carriage of the tractor DT-75

The wear of a surface under bearing 7909M the admissible size is 100.03 mm

Damage to the thread, nicks, dyeing, failure of more than two thread threads is not allowed.

Surface wear under bushings permissible size 80.06 mm

Part Repair Process

Part recovery - a set of technological operations to eliminate defects of the part, ensuring the resumption of its operability and geometric parameters, established by the regulatory and technical documentation.

Defect - each individual non-compliance of the products with the established requirements.

A defective part is a part whose quality indicators have unacceptable deviations from the requirements of the regulatory and technical documentation for repair. The part to be repaired is a defective part, the elimination of defects of which is technically possible and economically feasible.

Method of part restoration - a set of operations characterizing the technological process (surfacing, spraying, etc.). A typical surface is a surface characterized by the unity of working and wearing conditions in a joint for a group of surfaces with common structural features.

Technological processes are divided into typical, single and group processes. A typical process is designed to restore a group of products with common structural and technological features. A single process is used to restore a group of products of the same name, type and version. The group process is necessary when restoring a group of products with different design but common technological characteristics.

A process recovery operation is a complete part of a process performed at one workplace.

Depending on the form of organization of production, determined by the volume and nomenclature of restored parts, the following types of restoration production are distinguished: enterprise, workshop, site, workplace, flow-mechanized line (PML).

Centralized restoration of parts means such a method of organizing production, in which parts are restored in special workshops, on sites and PML not only for their own needs, but also for other (or only for other) enterprises. (1, page 166)

4.2. Choosing a Rational Way to Repair Basic Part Defects

Selection of rational method of part defect elimination is performed according to three criteria:

technological (applicability criterion);

technical;

techno-economic.

To eliminate each defect (group or complex of the same defects), a rational method, i.e. technically sound and economically feasible, must be chosen.

The rational method of restoring parts is determined using criteria: technological (applicability), technical (durability) and technical and economic (generalizing). (3, page 132)

Depending on the physical nature of processes, process characteristics, and other characteristics, existing methods can be divided into ten groups:

Mechanical machining: machining for repair size (RP); installation of additional repair part; processing until wear traces are removed and regular geometrical shape is imparted; overpowering.

Plastic deformation: drawing, drawing; editing (on presses, gluing); mechanical distribution; hydrothermal distribution; electrohydraulic distribution; rolling out; mechanical compression; thermoplastic crimping; precipitation; extrusion; rolling; electromechanical landing.

Putting polymeric materials: dusting is gas-flame, in a fluidized layer (vortex, vibration, vibrovortex), etc.; pressure testing; injection molding; application with spatula, roller, brush, etc.

Manual welding and surfacing: gas; arc; argon-arc; blacksmith; plasma; termite; contact.

Mechanized arc welding and surfacing: automatic under flux; in the environment of protective gases - argon, carbon dioxide (carbon dioxide), water vapor, etc.; with combined protection; arc with plasma protection; vibratory; powder wire or tape; wide-layer; a recumbent electrode; plasma (compressed arc); multi-electrode; with simultaneous deformation; with simultaneous machining.

Mechanized arc-free welding and surfacing methods: induction (high-frequency); electroshlag; contact welding and welding; friction; gas; e-beam; ultrasonic; diffusion; laser; termite; explosion; magnetic pulse; furnace cooking.

Gas thermal application (metallization): arc; gas flame; plasma; detonation; high-frequency; electropulse; ion-plasma.

Galvanic and chemical coatings: direct current iron; periodic current ironing; flowing iron; local ironwork (extravagant); chromium plating; chromium flow, jet; Medenium, galvanizing; application of alloys; application of composite coatings; electrocontact application (electrification); galvanomechanical method; chemical nickel plating.

Thermal and chemical-thermal treatment: tempering, tempering; diffusion boring; diffusion galvanizing; diffusion titanation; diffusion chromium plating; diffusion chromatication; diffusion chromoazotization; cold treatment.

Other methods: filling with liquid metal; freezing; baking; soldering; soldering welding; electric spark build-up and doping.

Brief description of methods. For the first group of methods, wear of surfaces is eliminated by locksmithing or machining with changing their original dimensions. To obtain the necessary fit, connected parts with changed parameters are used and wear compensator (rings, shrouds, bushings, threaded spiral inserts, etc.) is installed. Sometimes the surface of the part is processed to give it the correct geometric shape (pressure discs, cylinder head planes, etc.).

During plastic deformation, dimensions of worn-out surfaces are restored due to metal redistribution from non-working parts to working ones. The volume of the part remains constant. The main advantages of these methods: there is no need for an additive material, simplicity, high productivity and quality.

The technology of restoring parts with polymeric materials is simple and affordable (used in the field), low cost, high performance and good quality.

Manual welding and surfacing are widely used due to simplicity and accessibility. At the same time, it is low-productivity, material-intensive, does not always provide high quality.

Mechanized welding and surfacing methods can be automatic and semi-automatic. Most of these methods provide high performance and quality.

In arc methods, the heat source for melting the additive material and the surface of the part is the heat of the electric arc. With arc-free methods, this source is the loss from eddy currents (TVH), Joule heat (electroshlag surfacing, contact welding), the heat of burned gases, etc.

Manual and mechanized welding and surfacing methods have received the most use (70... 80% of the total recovery). Their disadvantages are the thermal effect on the main metal, including on non-recoverable surfaces, deformation of parts, significant features on mechanical processing. Most of these methods are useful for restoring highly worn parts.

When sprayed, the molten additive material (wire or powder) is sprayed with compressed air and applied to the prepared surface of the part. Methods of spraying are distinguished depending on the source of heat: arc - heat of an electric arc, flame gas - heat of a gas flame, etc. Spraying metals, polymers, etc. When spraying metal, the process is called metallization. Most spraying methods are characterized by high productivity, allowing sufficiently precise adjustment of the thickness of the coating and the allowance for machining. A serious disadvantage of spraying is the low adhesion of coatings to the base. To increase it, application of a special sublayer, subsequent melting, etc. is used.

The basis of galvanic methods is the phenomenon of electrolysis. They are distinguished by the type of deposited metal, the type of current used, the deposition method, etc. Galvanic methods are highly productive, do not have a thermal effect on the part, make it possible to accurately control the thickness of coatings and minimize or completely exclude mechanical treatment, provide high quality coatings with cheap raw materials. Such methods are used to restore little worn parts. The disadvantage of electroplating is the multioperability, complexity and environmental harmful nature of the technology.

Thermal treatment is used to strengthen and restore the physical and mechanical properties of parts (spring elasticity, etc.). In chemical-thermal methods, diffusion saturation of the surface of the part with refractory metals (chromium, titanium, etc.) occurs with a certain change in size. These methods are used to restore and increase the wear resistance of low-worn parts (plungers, etc.). (1, page 167170)

4.2.1. Nature of defects and purpose of methods of their elimination according to technological criteria

According to the technological criterion, the methods are selected based on the possibilities of their use to eliminate a specific defect of a given part, taking into account the magnitude and nature of wear of the part material and its structural features. According to this criterion, all kinds of methods are assigned, which in principle can be used to eliminate a particular defect.

Calibration is used to repair thread damage, and in cases where more than two thread threads are torn off, threaded inserts are installed. Wear of the surface for bearing 7909M is used for curling. Wear of the surface under the bushings can be restored by pressing the repair bushings.

Evaluation of methods is not done at this stage.

Conclusion

The design examined the device, analysis of operation and characteristics of the main causes of loss of operability of the assembly unit.

Structural diagram of disassembly of DT-75 tractor outer suspension carriage balancer has been developed

The part defect process has been developed.

The technological process of restoring defects of the external suspension carriage balancer of the DT-75 tractor has been developed

In the process of course work, the device and principle of operation of the DT75 tractor outer carriage balancer, the characteristic of the main causes of the unit's loss of operability, were studied. They also presented a structural diagram of disassembly of the unit and developed a technological process for restoring and defective the part.

We developed the necessary recovery routes for the part and determined the combination of defects in them.

They chose rational ways to eliminate the main defects proposed by the teacher.

They gave a brief characteristic of the defects and assigned methods of eliminating the defects according to the technological criterion. The assigned methods for elimination of defects were evaluated according to technical and technical-economic criteria.

Developed Job Instructions for Part Recovery. They drew up a plan of operations for the process of restoring the part along the routes.

They made a choice of technological equipment. The main process operation modes and technical normalization of these operations were calculated.

Basic technological documentation was developed and presented.