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Urgency of research
The purpose and problems
1 Technological processes and condition of a superficial layer of deteils machines
Concusions
Prospects of the further researches
The list of references
Transition to market relations in economy has pushed into the foreground the problems connected with release of mechanical engineering competitive production. In its turn, the high level of requirements to modern machines has caused a line of the problems connected with the technology of machines details processing. Increase of physicomechanical characteristics of durability, hardness and wear resistance of constructional materials has defined the general tendency to their workability decrease, that results in the raised deterioration of the tool, increase in efforts, deformations and temperatures of cutting, and consequently – to decrease in accuracy of processing and quality of the processed surfaces. The set of problems is caused by design features of machines details. The gradual tend to reduction of metal quantity for the certain detail for designs that results in decrease of rigidity and the capacity to resist vibrations of details during processing. Complexity of details configuration causes non-uniform elastic deformations during cutting and errors of processing corresponding to them. In these conditions the special urgency is typical for the technologies based on removal of thin shavings that provides small efforts of cutting, deformation of details and their high accuracy.
The general problems of processing are aggravated during reception of exact apertures that is connected with unfavorable conditions of cutting and reduction of the tool rigidity. Parameters of processing accuracy and quality of apertures surface are formed on all an extent of technological process in view of the different problems that are solved at stages of first complete and finishing processing.
Thus achievement of simultaneous productivity increase effect, profitability, accuracy of processing and quality of details surfaces always was and will be further one of mainstreams of mechanical engineering development technology.
In connection with everything mentioned above the large scientific and technical problem is actual as its decision is directed on creation of scientific bases of exact apertures processing technology, search of the ways of efficiency increase for technological process of their reception, new ways of management development for previous and final processing of apertures, expansion of technological opportunities of the equipment and cutting tool is stated.
The purpose of masters’ work is the increase in productivity, improvement of quality, decrease in prime price input and the cost price at manufacturing a frame of a combine 4PP-2Ì.
Therefore for the decision of the stated object, the following tasks are formulated:
1 Technological processes and condition of a superficial layer of machines details
Serviceability of details in many respects depends on a condition of superficial layers. Requirements to their quality continuously grow in process of an intensification of operating modes of details. Still recently quality of superficial layers was characterized basically by hardness and roughness. Now frequently it is necessary to create residual pressure of the certain sign in superficial layers, not to admit formation of the released sites. It is established, that overheated metal at grinding reduce a limit of endurance on a bend of 25-30 %, and grinds cracks — up to three times. Decarbonating and decrease in hardness of all on 5 units HRC can reduce durability of cogwheels up to elimination tooth’s in 2-3 times. For the details working in conditions of contact loadings, the great importance has absence in superficial layers of residual àóñòåíèòà, and also cementation grids.
With the growth of requirements to the surface roughness the its estimation only on roughnesses height and an average arithmetic deviation (Rz and Ra) frequently appears insufficient. From fig. 1 it is visible, that the height of roughnesses does not give the exhaustive characteristic of roughness. At the same height of microroughness they can have the various form, create various conditions for the deterioration course, it is especial at his initial stage — during the period of the initial work. Researches of last years show, that at an estimation of a roughness it is necessary to take into account a step and character of an arrangement of microroughnesses, radiuses of circled tops and hollows, size of the basic surface. The more it is the less is, the probability of occurrence contact destruction centers, teases formation, etc.
Figure 1.1 – Profilogramma and curves of the basic surfaces that are processed
à – sharpening; á – initial work; â – initial work during vibration.
The technology has sufficient means to receive a required roughness. Except for diamonds and cubic nitride of a pine forest, wide application was provided for the ways of harder-fair processing, such as coating of external surfaces, rolling apertures. These processes differ by higher efficiency, than grinding, provide in many cases reception of surface roughness higher class, they possess a lot of other advantages.
As a result of performance of the given work technological process of manufacturing of a large-sized case detail has been investigated and developed. The opportunity of processing of the large-sized details on multioperational machine tools is considered.
The method of submissions division is in details investigated at boring of the basic apertures.
The analysis of processing methods of the large-sized case details basic apertures is made and the equipment for processing of the basic apertures is analyzed.
The cutting and measuring tool for maintenance of the best accuracy is provided and analyzed at processing of the basic apertures and all elements of a large-sized case detail of a combine 4PP-2Ì.
Prospects of the further researches
The prospects of research in the given problem are the following:
1 Technological processes and condition of a superficial of machines details
Conclusions
Prospects of the further researches
The list of references