THE ACCURACY OF THE GEOMETRİCAL PARAMETERS OF THE RESTORED PLUNGERS AND FLANGES

ABSTRACT

When choosing effective processing modes, the results should be considered not only from the point of view of the productivity of the process and the reduction of roughness of the processed surface, but also from the point of view of the intensity of error recovery. After diffusion metallization, mechanical processing of parts (100 plungers and 100 carves) with various initial geometric errors (ovality, conicity, curvature) from the form was carried out to evaluate the precision of mechanical processing of plunger pairs. Processing of the entire batch of details was carried out according to the designed technology. The measurement of the processed details showed that the accuracy deviations did not exceed the allowable values for each operation.

АННОТАЦИЯ

При выборе эффективных режимов обработки результаты следует рассматривать не только с точки зрения производительности процесса и снижения шероховатости обрабатываемой поверхности, но и с точки зрения интенсивности восстановления ошибок. После диффузионной металлизации была проведена механическая обработка деталей (100 плунжеров и 100 вырезов) с различными исходными геометрическими погрешностями (овальность, конусность, кривизна) от формы для оценки точности механической обработки плунжерных пар. Обработка всей партии деталей осуществлялась по разработанной технологии. Измерение обрабатываемых деталей показало, что отклонения точности не превышали допустимых значений для каждой операции.

Keywords: diffusion metallization, mechanical processing, plunger pair, flange, ovality, conicity

Ключевые слова: диффузионная металлизация, механическая обработка, плунжерная пара, фланец, овальность, конусность

Introduction

Processing of the entire batch of details was carried out according to the designed technology. The measurement of the processed details showed that the accuracy deviations did not exceed the allowable values for each operation. The statistical analysis of the results of the measurement of plungers and hollows showed that the distribution of ovality, conicity and curvature dimensions after polishing, thread cutting, rough and final processing obeys the normal law or the Weibull law (see table 1) [1-6].

Main part

Graphs 1, 2, 3 show the distribution curves of the accuracy of the geometric parameters of the plungers and grooves after the final processing. It can be seen from the curves that the maximum values of ovality, conicity and curvature are lower than the allowable values of these parameters according to the technical conditions set by the manufacturer and DÜIST 250883 and OST 23 for the details of the plunger pairs of fuel pumps [2-7].

Figure 3 shows the circular diagrams of the plungers and grooves in three sections after processing. It can be seen from the circles that after mechanical processing, the ovality is within the limits of 0.2...0.4 μm. The analysis of the results of the measurements showed that the dispersion of the diameter dimensions of the plunger and the grooves were 32 µm and 26 µm before machining, and 32 and 47 µm after machining, respectively. This means that after machining, the plungers and grooves can be assembled using the assembly method. During machining after black finishing, 5 out of 100 engravings (5%) were broken because they had more than 0.003 mm of curvature, which is considered unacceptable by the manufacturer [3-8].

Table 1.

Statistical analysis of the results of measurements of plungers and carves

Figure 1. Ovality o_p (a) and taper k_p (b) distribution curves of plungers after final processing: 1-Differential curve, 2- Integral curve

Figure 2. Distribution curves o_f ovality o_p (a) and conicity k_p (b) of grooves after final processing: 1-Differential curve, 2-Integral curve

Figure  3. Distribution curves of the curvature of the gouges after finishing: 1-Differential curve, 2-Integral curve

Figure 4. Circles of plungers and gouges after finishing

After the final completion, the geometrical parameters of all the carvings were within acceptable limits. During mechanical processing, all 100 plungers had geometrical parameters with accuracy within the limits that could be released by the manufacturer-factory.

After final processing, the pre-tension surface of the plungers has a mirror-glossy surface (R_a=0.03...0.04 μm), but at the same time, small depressions - small pores were detected on the surface of the plunger during profilography. The formation of these pores can be explained by the removal of soft constituents located on the surface of the coating during mechanical processing. Pores on the pretension surfaces do not extend to great depths, so they will not significantly affect the performance of the plunger pairs, but at the same time, they can also have a positive effect on their washing [4-9].

Thus, the results of processing test batches of plunger pairs after diffusion metallization showed that the geometrical parameters of the details (non-roundness, conicity, curvature) meet the technical conditions of the manufacturer-plant for serial production [5-10].

The following conclusions can be reached on the basis of experimental studies of the process of mechanical processing of piston pairs restored by vapor phase diffusion chromating in vacuum.

Figure 5. Profilogram of the plunger (a) and the notch (b) after finishing

Conclusions

1. In modern times, when strengthening and restoring the preview details of high-pressure fuel pumps of ship engines, repair facilities are subject to strict conditions from different points of view: economic, technological process, working conditions, environmental safety and energy costs.
2. When developing a mathematical model, it is more expedient to use the theoretical foundations of production functions. In this case, it is possible to assess the effectiveness of certain costs that make up the technological process and choose the optimal method of recovery of worn parts of high-pressure fuel pumps of ship engines.
3. The theoretical basis of the technological process of restoration of worn parts should be based on the methods of restoration to ensure the required reliability of the restored parts. The optimal method of restoring worn parts will solve a number of problems by minimizing the cost of operating high-pressure fuel pumps of ship engines.

Reference:

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