SHALLOW MILL MILL MAIN LINE REDUCER

Contents

Table of contents

INTRODUCTION

1. VIEW OF EXISTING GEARBOX STRUCTURES OF MAIN LINES OF GRADE ROLLING STANDS WITH VERTICAL ARRANGEMENT OF ROLLS

4. ANALYSIS OF THE PRACTICE OF USE OF WELDED BODY PRODUCTS IN THE MANUFACTURE OF MACHINES AT HEAVY MACHINERY PLANTS

6. GEARBOX PERFORMANCE STUDY

6.1 CALCULATION OF GEARBOX MAIN PARAMETERS

6.2 CALCULATION OF FORCES IN ENGAGEMENT

6.3 CALCULATION OF SHAFT SUPPORTS REACTIONS

6.3 CALCULATION OF VOLTAGES IN GEARBOX HOUSING

6.4 CALCULATION OF STRENGTH-RESISTANT ELEMENTS

6.5 SHAFT STRENGTH CALCULATION

7. MACHINE OPTIMIZATION PROPOSALS

8.STRUCTURE DESCRIPTION AND OPERATING PRINCIPLE OF MODERNIZED MACHINE

CONCLUSION

BIBLIOGRAPHIC LIST

Introduction

In the history of metallurgical machine structures, the following options are possible:

the design of the mechanism remains unchanged for a long period of time, and subsequent options are a development of the main design solution;

over a long period, multivariability of structures of mechanisms that perform the same technological operation is noted.

The first option is a sign of achieving the required level of operational reliability. The second option is to find an optimal or rational design in the design. The initial prerequisites for the design change are fixed failures and their established causes. In this regard, we can recall the invariability of the designs of skip lifts and the variety of design solutions for the mechanism of turning the arch of the electric arc furnace. But there is a third option - when the design solution, remaining fundamentally unchanged, is used in the design of mechanical equipment of metallurgical enterprises for a long time. There are differences in the design of the individual assemblies and the overall arrangement of the mechanisms. Such solutions include combined reduction gears for driving rolling stands.

The set of machines and mechanisms of the rolling mill includes various special reduction gears used both in the main drives and in auxiliary equipment. The conventional drive scheme of any rolling mill includes a main reduction gear that provides the required gear ratio between the motor and the work stand, and a gear stand for distributing the transmitted torque between the rolls of the work stand. Universal or toothed spindles are used to connect the gear and working stands, which provide the possibility of the drive operation when the distance between the working rolls changes after each of their turning.

One of the directions of improving the working lines of the mill is the combination of the main reduction gear with the gear stand and other mechanisms, which allows to reduce the production areas, reduce the labor intensity and cost of the created object.

Thus, the design and calculation of the combined reduction gear are one of the most important issues that need to be given a sufficient amount of time and approach the calculations as accurately as possible, since the rolling force depends directly on the reduction gear itself, which is one of the main parameters of the rolling mill.

One of the main parts of the reduction gear box of the rolling stand, which requires careful calculation, is its body. In modern mechanical engineering, along with cast, welded body parts are also used. Welded structures are mainly used in small-scale and individual production. Welded frames usually have a lower weight than cast ones, since due to the high modulus of elasticity of steel compared to cast iron, the same rigidity can be obtained with a smaller wall section. With a small thickness of the sheets from which the welded part is made (3-6 mm), the necessary stiffness is achieved due to welded partitions and ribs. Therefore, the labor intensity of making welded parts from thin sheets is higher .

It is customary to calculate the welded body in machine building approximately, neglecting many parameters, compensating for all assumptions with a large safety margin. Modern computational methods approach calculations on the other hand: with the help of computer programs, you can calculate voltages at each point of the designed body without spending a lot of time and without neglecting various parameters. This became available after the FEA (finite element method) was developed. The idea of ​ ​ this method in its name. The region in which the solution of differential equations is sought is divided into a finite number of subareas (elements). In each of the elements, the type of approximating function is arbitrarily selected. In the simplest case, this is a polynomial of the first degree. Outside of its element, the approximating function is zero. The function values at the element boundaries (in nodes) are the solution to the problem and are not known in advance. The coefficients of approximating functions are usually sought from the condition of equality of the value of neighboring functions at the boundaries between elements (in nodes). Then these coefficients are expressed through the values ​ ​ of the functions in the nodes of the elements. A system of linear algebraic equations is compiled. The number of equations is equal to the number of unknown values ​ ​ in the nodes on which the solution of the original system is sought, directly proportional to the number of elements and is limited only by the capabilities of the computer. Since each of the elements is associated with a limited number of neighboring ones, the system of linear algebraic equations has a sparse form, which significantly simplifies its solution.

If we talk in matrix terms, then the so-called stiffness matrices (or Dirichlet matrix) and masses are collected. Further, boundary conditions are imposed on these matrices (for example, under Neumann conditions, nothing changes in the matrices, and under Dirichlet conditions, rows and columns corresponding to boundary nodes are drawn from the matrices, since due to boundary conditions the value of the corresponding components of the solution is known). Then a system of linear equations is assembled and solved by one of the known methods.

From the point of view of computational mathematics, the idea of ​ ​ the finite element method is that the minimization of the functionality of the variation problem is carried out on a set of functions, each of which is defined on its own sub-domain, for a numerical analysis of the system allows us to consider it as one of the specific branches of diacoptics - the general method of studying systems by dissecting them .

4. analysis of the practice of using welded hull products in the manufacture of machines at heavy engineering plants

Most often, the body parts are made cast from castings of gray cast iron of grades SCH 2140 and SCH 1532 or modified cast iron.. To make a cast part, you must first make a model, core boxes and casting equipment. This is due to additional costs and a significant extension of the production time of machines.

Blanks for body parts are sometimes made in single production welded from sheet steel or welded, they have a lower weight, and in some cases a lower cost compared to cast [2].

Along with die-welded blanks, welded blanks are also used. This is especially common in the manufacture of blanks for a number of body parts characterized by a wide variety of structural shapes, sizes, masses and materials. The workpiece is divided into a number of simple parts obtained by casting, and then they are joined by welding, forming a welded workpiece of a part. So, for example, press crossarms, turbine stators, machine frames, etc. This type of workpieces drastically reduces the labor input and metal input of the article. Along with cast in machine tools, welded body parts are also used. Welded structures are mainly used in small-scale and individual production. Welded frames usually have a lower weight than cast ones, since due to the high modulus of elasticity of steel compared to cast iron, the same rigidity can be obtained with a smaller wall section. With a small thickness of the sheets from which the welded part is made (3-6 mm), the necessary stiffness is achieved due to welded partitions and ribs. Therefore, the labor intensity of manufacturing welded parts from thin sheets is higher [6].

Heavily loaded body parts of special machines to be produced in single copies should be welded, and parts bearing a moderate load and to be produced in significant quantities should be cast. With a large release, the cost of once made models per part is negligible. At low load high mechanical qualities of steel will not be fully used [3].

The question of the preference of the welded or cast structure of the body part of the designed machine is decided on the basis of the totality of technical and economic indicators of both options, as well as the capabilities of the foundry and welding workshop of the plant at which the machine will be manufactured. For moderately loaded body parts, especially in large-scale and mass production, the advantage is on the cast iron side. Welded structures in mechanical engineering are used for large, but simple in configuration heavily loaded body parts formed by a combination of the simplest geometric surfaces.

Advantages of welded structures over cast structures:

mechanical qualities of steel are higher than that of ordinary cast iron, at the same loads, safety and rigidity reserves, the weight of the welded steel part is less than that of cast iron.

at the same load and the same size of steel and cast iron elements, the ratio of the safety factor for cast iron to the safety factor for steel is equal to the ratio of the corresponding strength limits.

the welded part, if necessary, is easy to correct - further strengthen, increase its stiffness, change its shape and dimensions. In a cast part, it is much more difficult to make such corrections. The possibility of corrections and alterations is a valuable advantage of welded parts for prototypes of machines.

Cast structures also have an advantage over welded structures:

When working on compression, the comparison in terms of weight is in favor of cast iron, if you do not use better quality heat-treated steel than St for the manufacture of the corresponding element. 3 or St. 5.

In fact, the savings in metal consumption when replacing a cast iron steel part are highly dependent on the design of both options.

By comparing the advantages and disadvantages of both options, the areas of their rational application can be identified as follows:

Heavily loaded body parts of special machines to be produced in single copies should be welded, and parts bearing a moderate load and to be produced in significant quantities should be cast. With a large release, the cost of once made models per part is negligible. Under low load high mechanical qualities of steel will not be fully used [5].

In particularly critical cases, the choice of a design option is determined by a comparative feasibility study. At the same time, the specified time for the production of machines, the production capabilities of the manufacturer, the possibility of co-operation and other conditions are taken into account.

Moving from general to private, we will consider the practice of using housing parts of reduction gears.

The gearbox housing is its basic part, the overall dimensions of which are determined by the type of transmission mechanisms that make up the gearbox; number, dimensions and relative arrangement of parts of these mechanisms in the internal cavity of the housing; adopted system for lubrication of gears of reduction gear and its bearing units.

Gear cases have a box-like design, as a rule, of a rather complex configuration. The main reliability criteria of the body parts are strength, rigidity, wear resistance and durability. In most cases, the body parts have a complex configuration with many reinforcing elements (ribs, bosses, etc.). This greatly complicates strength and stiffness calculations. They are studied in detail in special courses. Calculations are carried out by methods of resistance of materials, theory of elasticity, in critical cases strength and rigidity are determined experimentally.

Welded body parts are economically more profitable in single or small-scale production, when the cost of manufacturing tooling (chicks, rods, etc.) is not justified or casting at the enterprise is not mastered. Parts are made from rolled stock or in combination with stamped, forged, cast elements. Moreover, the material of the latter should have good weldability (low-carbon steels, some alloyed steels), otherwise the welding process is greatly complicated. When designing a welded product, it is necessary to take into account the appearance of welding deformations, both in individual parts and throughout the product. Therefore, responsible parts have to be annealed or subjected to prolonged "stalking" (aging).

You should limit the minimum number of type elements, maximize the use of bent and stamped elements, it is desirable to limit the contours of elements to straight lines; ribs, slashes should not have sharp angles, since in this area, during welding, the weld is not fully functional. The shape of the elements to be welded and their mutual arrangement should not hinder welding.

Machine Optimization Suggestions

One of the basic parts of the combined gearbox of the rolling stand is the housing, the main task of which is to prevent shaft misalignment, which means that its main parameters are rigidity and strength. You can increase these indicators by increasing the wall thickness and additional stiffening ribs. There are also many elements in the design that can be unified and standardized, which will greatly simplify and reduce the cost of manufacturing this machine.

Unified elements: shaft covers (for each shaft two);

Standardized items:

bolts (of 10 threads, 4: M12, M24, M36, M48);

bearings (considering that the production of this gearbox will be in Russia, then we bring the international structural elements to GOST, thereby also making production cheaper);

The structure also contains a complex seal of the second shaft, which is more efficiently replaced by a cover, which presses the sleeve through the gasket and thereby fixes the bearing.

In order to take advantage of each element of the structure, we choose a bevel gear with the left direction of the tooth, which rotates counterclockwise, thereby the radial bearing of the wheel takes the greatest radial loads, and the axial loads of the gear are taken by a cover fixed by bolts.

To achieve equal strength on the body, the stiffness edges reduce the thickness and length.

To reduce the stresses in the studs on the output shafts, the most optimal version of diameters in the design was selected.

Description of the design and principle of operation of the modernized machine

Reduction gear is designed to transfer power from engine to drive shaft of machine with decrease of angular speed and increase of torque.

Assembly drawing consists of housing (30), in which there are located: shaft-gear (1) and shafts-gears (3,5,7,8), on which gears (2,4,6) are installed respectively. Shaft-gear (1) and gear wheel (2) have oblique conical engagement, other shafts-gears and wheels have oblique cylindrical engagement. The gear shaft (1) has a smaller diameter and is connected to the engine. Through conical gear, torque from (1) is transmitted to conical gear wheel (2), the wheel betrays the torque on the shaft-gear (3) through an interference fit, then on the same principle the shaft-gear(3) transmits the moment to the gear cylinder wheel (4), which transmits the moment to the shaft-gear (5), then through interference fit on the cylinder gear (6), then by means of landing, the moment goes to the gear shaft (7) and through engagement with the gear ratio equal to one at the output of the reduction gear box there are two shafts. Lubricants are used to reduce wear of teeth and bearings, as well as to increase efficiency. On the gearbox housing for inspection there are hatch-holes closed by the cover.

Gearbox assembly:

Prior to assembly, inner cavity of reducer housing is thoroughly cleaned and covered with oil-resistant paint.

Assembly is performed in accordance with gearbox assembly drawing, starting from shaft assemblies:

Key is put into high-speed shaft, then sleeve, bushes, collar, rolling bearings (radial-thrust roller conical, radial roller spherical) are fitted, round nut is twisted.

On shaft-gear (2) conical wheel (3) is pressed, bushing, sleeve, bearing are fitted, shaft is fixed with covers from both ends. Similar assemblies are assembled from shaft-gear (4) and cylindrical wheel (5), shaft-gear (6) and cylindrical wheel (7), rolling bearings and bushing are fitted on shaft-gear (8).

In order for one support to be floating and the other fixed, bushings on one side of the shaft are used, which tightly abut against the covers of the housing and the outer ring of bearings, and bushings are internally abutted against;

The aggregative units are set so that engagement occurs;

No clamping of bearings is checked by turning the shafts and the covers are bolted;

Using a set of gaskets for sealing, the high-speed shaft is closed in a composite cover, and the two output pinion shafts are closed with a cover for collecting oil, the pinion shafts are also closed with covers.

All parts of the housing are fixed relative to each other by studs and bolted connections.

Conclusion

In this work, the reduction gear of the main drive of the rolling stand of a small-grade mill was investigated using the Solidworks, ANSYS programs, options for optimizing this machine in order to increase operational properties were proposed, and drawings of the housing and gear roll were made.

2V-1-Model.cdw

Внутренности.cdw