Agricultural Engineering Technologies

Contents

Assignment for Course Engineering

Introduction

1. Part Connection Classification

2. Process Part

2.1 Definition of type of production and its characterization and justification

2.2 Part processability analysis

2.3 Unification factor of structural elements of the part

2.4 High-quality workability of the part

2.5 Selection of Procurement Type

2.6 Equipment selection, routing and operating map

2.7 Calculation of cutting modes

3. Development of Part Control Method and Instrument Design

Literature

Application

Introduction

The science "Engineering Technology" studies the general information and methods of machine production. The concept of "engineering technology" has a wide and narrow meaning. The broad concept of "machine building technology" includes all methods of producing blanks (casting, stamping, welding, etc.), mechanical and thermal processing of parts, assembly of products. The narrow concept of "engineering technology" mainly includes issues of mechanical processing of parts and assembly of machines.

The Mechanical Engineering Technology course usually addresses only mechanical machining, workpiece selection, and product assembly. This is due to the fact that the mechanical processing of parts and the assembly of machines in machine-building plants account for the maximum labor costs, and it is possible to fulfill the requirements for the accuracy and quality of the surface of parts mainly only by machining them.

The course "Technology of Agricultural Engineering" is designed for students of agricultural universities studying in the specialty "Technology of servicing and repair of machines in the agro-industrial complex." It is based on such disciplines as Materials Science, Structural Materials Technology, Metrology, Standardization, Certification, Machine Parts, etc. Successful mastering of disciplines is possible if students have good practical skills in working on the main types of metal cutting machines. The course, based on the knowledge gained from the study of other technological disciplines, provides comparative characteristics of various technological methods with the aim of their rational selection in the design of technological processes taking into account specific production conditions. The complexity of the subject "Engineering Technology" is due to the close interconnection of different technological areas. Thus, the development of machining processes of parts is carried out in close connection with thermal treatment, application of protective coatings, etc., and these operations can be included in the machining flows of parts.

Agricultural and tractor engineering as a branch of general engineering has some characteristic features. This is primarily a large range of products, which, of course, determines the variety of dimensions and masses of machines. Most agricultural machines and tractors operate in difficult conditions due to significant and uneven loads, the presence of dust and moisture. This implies high requirements for the perfection of structures and the quality of production of these machines.

The general principles of rational machining of parts and assembly of machines described in this course are used in many cases in the repair of machine parts.

1. Classification of part connections.

Assembly of machines - the process of connecting parts and assemblies into a whole machine in accordance with the specified specifications. Components of machines - parts and assembly units (units).

The assembly can be shared and subassemblied. General assembly - an assembly whose object is the product (machine) as a whole. A subassembly is an assembly whose object is a product component (subassembly).

The labor intensity of assembly work in tractor and agricultural engineering is 20... 30% the total labor intensity of machine manufacturing. For individual machines, the labor intensity of assembly work can reach 40... 60% the total labor intensity of the product.

The performance, reliability and durability of the machine largely depend on the quality of assembly work.

Initial data for design of assembly processes: assembly drawings of assemblies and general types of machines; For better familiarity with the machine, drawings of parts included in the units are required; the value of the program task and the duration of the program; information on the specific conditions of this production (active, reconstructed, new or its alternating development).

Assembly drawings of units and general types of machines shall contain: basic dimensions characterizing the unit (machine); Dimensional tolerances that determine the relative location of parts structural clearances; special requirements regarding the assembly of mating parts or the entire machine.

Attached to the drawings are: part specifications for each product; description of the article design; Acceptance Specification.

Part specifications for each product shall contain: the name of all parts; mass of parts; type of material and its brand; Procurement types number of parts per item; for gated or normalized parts and assemblies - GOST number or normal.

The description of the design of the article (machine, assembly) should give a complete understanding of the operation of the article, the purpose of its individual parts and their interaction during operation.

The specification for the acceptance of products defines the requirements for the product as a whole and for its individual elements.

The assembly of machines is characterized by various joints of parts or assemblies. Joints are classified according to structural and technological characteristics. According to structural features, connections are fixed and movable. Stationary, in turn, are divided into non-detachable (riveting, welding, soldering, gluing, hot fits) and detachable (bolts, screws, studs, cotter pins, wedges, locks, fixed landing presses).

Movable joints are characteristic of kinematic pairs (sliding, screw, toothed, worm, etc.). Movable connections are in most cases detachable, although non-detachable movable connections are possible (for example, a pair of screw and nut with split ends of the screw).

According to technological features, threaded, press, welded, soldered, riveted, glued, rolling, bending joints are distinguished.

Stages, structure and organization of assembly processes

Assembly process stages.

1. Preparation for assembly of individual parts by means of grouting, grinding of burrs and surfaces, stuffing, lapping, polishing, hole drilling in place, hole unfolding, trailing, bending. Preparation for assembly is characteristic of single production, occurs in mass production and is unacceptable in mass production.

2. Connection of parts into assembly units and assemblies from assembly units.

3. General assembly - assembly of the entire machine.

4. Adjustment - check of correct interaction of machine parts.

5. Run-in of the machine (for example, engines).

6. Machine test - check of machine operation with removal of required characteristics.

Structure and organization of the assembly process. The product assembly process is divided into separate operations.

An operation is a complete part of the assembly process of a unit or machine, carried out by one or more workers in one place. The operation consists of transitions.

Transitions are part of an operation performed without changing the tool by one or more workers. When assembly works are timed, the transition is divided into working methods.

Working acceptance - part of the transition, consisting of the simplest working movements performed by one worker.

Stationary assembly is performed at fixed working place. It is most characteristic of individual and serial production. In mass production, a stationary assembly finds a large mass for the product.

During movable assembly the article (assembly) moves from one work station to another. Each work center has a specific recurring option. Movable assembly is used in mass production and mass production.

To increase the efficiency of the assembly process, an in-line assembly of assembly works is used. In most cases, in-line assembly, the assembly object is movable (although the in-line method is also possible with a fixed assembly object). In-line assembly is characterized by the following features: fixing assembly operations to certain jobs; Location of work centers in the order of the operation sequence rhythmicity (synchronism) of the operation over time; in this case, the time for the operation is adjusted to the stroke (one workplace), two strokes (two workplaces), etc.: interchangeability of parts, as a result of which it is not necessary to fit the parts in place.

For mobile in-line assembly, the following transport devices are used: roller wagons, rail and rail-free trolleys, moved manually or by an electric motor; various conveyors and conveyors, including suspended conveyors; carousel tables.

In an in-line movable assembly, the product feed may be continuous or discontinuous.

The main initial value for the calculation of the in-line assembly is the release cycle?. If the assembly is performed at continuous supply of the article, then the cycle of the article release from the in-line line is equal to the cycle of operation:

τ= .

During assembly with periodic supply of the article, the operating stroke plus the time to move the article from one work station to another:

.

Conveyor speed in continuous motion, m/min,

v= ,

where l-length of workplace (distance between centers of two workplaces), m.

conveyor speed depends on specific production conditions and can reach 5 m/min.

L=m*l=m*z*( =( ,

Where is the m-number of jobs; z- number of the product at the workplace; - distance between adjacent products, m;,, - number of operations with duration equal to one, two, three, etc. A-length of the workplace, m; T time of passage of the entire length of the conveyor, min; valid working time fund (year, month, etc.), min; - production building of the conveyor for this product for the same calendar unit of time.

If it is produced with a periodically moving conveyor, then the total time of the production process is equal to the time of assembly and the time of movement of the conveyor with the product

=m* +

Fixed in-line assembly is used for products of large mass in small-scale production. The process of assembling the article is divided into approximately identical operations, the number of these operations becoming smaller compared to the movable assembly. Often, the duration of these operations is adjusted to the duration of a half or entire shift. In this case, heavy parts of the assembled machines are supplied to workplaces after working hours (after the end of the shift or during work breaks). Each collector team performs one operation and after completion of work goes to another workplace. Thus, unlike a movable in-line assembly, the assembled product is stationary, and a team of collectors together with tools moves.

Mechanization of assembly works. To accelerate and improve the quality of machine assembly, mechanized assembly tools and machines, as well as assembly devices, are widely used, especially in mass production. Machines and tools include electric sawdust and grinding machines, electric and pneumatic teeth, wrenches, screwdrivers, riveting machines, presses, valve lapping machines, etc.

Assembly devices are used to install and connect, lift, turn or change the position of assembled parts, check accuracy, etc.

Ways to reduce labour intensity of assembly works. These include interchangeability machining with the exception of part fitting processes; removing as many assembly operations as possible from a common assembly to a subassembly; timely supply of parts, assembly units and necessary accessories to assembly places; extensive use of mechanized tools and special assembly devices; organization of assembly according to the principle of in-line production.

Assembly flow diagrams. Scope of work in designing the product assembly process

Prior to development of the process of assembly of the product (assembly), process diagrams of the general and node assembly are made. These diagrams depict the sequence of assembly of a machine, node or subassembly from its elements. As initial material for drawing up the scheme of assembly serves the drawing of a product (knot, a subnode) with the specification of the entering elements (details, knots, subnodes).

Each part (subassembly, subassembly) in the assembly diagram is depicted as a rectangle divided into three parts, in which the number of the part (subassembly, subassembly) according to the specification, the name of the part (subassembly, subassembly) and the number of assembled parts (subassembly, subassembly) are indicated.

When designing an assembly diagram, you first select the so-called base part or base subassembly (subassembly). Such a basic element is an element of the assembled unit (machine), on which other parts and sub-units (units) are installed.

A straight line is drawn from the base element, to which rectangles are brought, indicating assembly elements in the order of their connection. At the end of the line, a rectangle indicates the assembly. To facilitate assemblies of subnodes, knots and details, raspoznavny on the scheme, the rectangles designating subnodes and knots circle with the double line.

Sometimes parts are distinguished from nodes (sub-nodes) in another way. Parts are placed above the line connecting the base element with the assembled unit (sub-unit, article), and sub-units (sub-units) - under this line.

Assembly flow diagrams indicate how connections are made if they are not defined by the type of parts to be assembled.

Based on the process diagrams of the assembly of sub-assemblies, assemblies and products, it is possible to judge its processability from the point of view of meeting the requirements of the assembly. The condition of assemblability is the possibility of dividing the product into more units and sub-units and parallel assembly (simultaneously in several places) of units (sub-units) with a reduction in the cycle of assembling the product.

Assembly diagrams are made up in the following sequence: first general, then node. The process diagrams of the assembly are the main ones for the subsequent design of the process processes of the assembly. With these schemes, the development of assembly technology is greatly simplified.

Depending on the organization of the process and the volume of product production, the assembly is consistent, parallel-serial and parallel. In sequential assembly of a product, all assembly operations are arranged one after the other in the order in which they are performed (this is typical for single and serial production). With a large production volume, the assembly of products can be parallel (mass production) when several assembly conveyors work. During parallel-sequential assembly of the article, part of assembly operations is carried out in parallel, and the other - in series. Parallel-sequential assembly is characteristic of large-scale production.

The process of assembling a product is developed in several stages.

1. Constructions of assembly drawings of the article and units are worked out for processability.

2. Rational methods of achieving assembly accuracy (complete, incomplete, with adjustment and fitting) are established.

3. Depending on the volume of production of products, an expedient form of assembly is established.

4. Degree of differentiation or concentration of assembly operations rational in these conditions is determined.

5. Sequence of joints of assembly units and parts of article is established and diagrams of general assembly and assembly of units of article are developed.

6. The most economical methods of assembly, control and testing of the product are chosen.

7. Select the required standard process equipment and process equipment (accessories, mounting, cutting and measuring tools) or design them if necessary.

8. Technical standardisation of assembly works is performed, grades of works are determined, economic indices of assembly works are calculated.

9. Draw up technical documentation for assembly works. It includes the development of roadmaps and operational charts of technological processes for assembly, assembly and electrical works, a picking map, a BOM, process diagrams for assembling the product and its assembly units.