STUDY OF A CYLINDRICAL SURFACE DURING DIAMOND GRINDING

ABSTRACT

High speed milling (HSM) is becoming not only laboratory but also industrial. However, this is usually considered a new production technology. The high speed milling method has many advantages over conventional milling. High-speed milling is often an easy way to increase efficiency at the expense of higher cutting speeds than simple use. The article discusses the significant advantages to achieve, with the use of high-speed milling in the manufacture of products from modern materials.

АННОТАЦИЯ

В статье приведены сведения о развитии современного машиностроения, приборостроения и многих других отраслей промышленности, о механической обработке высокопрочных материалов. Коррозия и выход из строя режущего инструмента в процессе механической обработки деталей влияет на качество и цену изделия. В статье представлена зависимость пускового усилия при алмазном шлифовании различными типами инструментов: пневмоинструментом и пневмоинструментом подпружиненным, в отличие от инструмента единой конструкции.

Keywords: lathe, fixture, diamond grinding, spring air tool, single tool, calibration, pneumatic tool, friction, power.

Ключевые слова: токарный станок, приспособление, алмазное шлифование, пружинный невмоинструмент, одиночный инструмент, калибровка, пневматический инструмент, трение, мощность

Using tools of different constructions, the forces can change and change direction when grinding details with a round profile diamond. When the direction of the force changes, the friction on the surface changes and this affects the wear of the tool. Diamond grinding can be done both from the beginning of the movement of the part and during its movement [1,2].

Experimental part. As equipment for experimentationNT-250-01 Lathe-universalmachine is used. A synthetic diamond indenter with a radius of R1.5 mm is used for all experiments. In the comparative experiments, a 12X18N10T threaded detail was used for external processing. The detail is mounted on machine tool centers. To prevent radial kicking, the outer surface of the part is processed. A hole detail made of D16T material is used for internal processing. A three-component dynamometer 5233A1 of the company "Kistler" [4] is installed instead of the cutter, and all kinds of tools with diamond tips are installed directly on it. The axis of the grinder must exactly match the axis of the machine centers. I-20 industrial oil is used as a lubricating fluid for polishing. During the diamond grinding process on a lathe, two movements occur, the rotary movement of the workpiece and the thrust movement. All power changes are recorded on the computer. There is always a temporary break between actions to get an accurate reading. In order to compare different grinding wheels, the following external grinding wheels were used: a) single wheel; b) dynamometer device (power element - flat spring with damper) c) pneumatic device with receiver (power element - blower with compressed air); d) receiver (force element - compressed air bellows) pneumatic tool for internal grinding installed on flat springs; e) dynamometric test; f) receiver (force element - compressed air bellows) pneumatic device mounted on flat springs [5]. The article presents two cases for comparison.

Pneumatic tool for external grinding. A pneumatic tool with a power element in the form of a pneumatic spring or bellows belongs to the type of elastic fastening tools and allows processing the external cylindrical surfaces of the part with radial kick or deviations in shape. The bellows is an elastic corrugated chamber that compresses during grinding. To stabilize power, a receiver is added to the "diamond triple" system, which allows you to significantly reduce pressure changes in the bellows by increasing the volume of compressed air. The volume of compressed air is 10 times greater than the volume of the working chamber of the bellows. Grinding is carried out at a certain pressure force [5,6], which is set using the air pressure in the system and controlled by a pressure gauge.

The design features of the pneumatic actuator should ensure the consistency of the grinding force Py, even with a large surface leakage, the change in the volume of the bellows is small compared to the volume of the receiver, so the change in pressure in the bellows and the grinding force are also small.

Figure 1. Built-in pneumatic tool

Calibration using a three-component dynamometer

To determine the required pressing force, it is necessary to select the required pressure in the receiver [6,7]. The bellows path is limited by a screw pressed through the ball.

Figure 2. Screw spring bearing: 1-adjustment screw;2-screw spring; 3-clock type indicator; 4-indentor

Figure 3. Dependence of grinding force components Ry, Rx and RZ:[N] on time T[s] Rsf = 2 mm; S = 0.05 mm/month; V ≈ 0.02 m/s; ω = 1.3 rad/s

Due to the relaxation of the pneumatic system, the radial force Py decreases slightly over time. Due to the protrusion of the tool relative to the dynamometer, the force Py directed along the axis changes. (Figure 2).

At the beginning of the unilateral movement, the force dependence of the grinding force is carried out in the same way..

Measurements were made according to the following criteria: in the direction of the cutting movement; 100N, 200N and 300N according to the level of loading forces; and on the use of lubricants.

Figure 4. Change of the force directed along the white

Figure 4 shows the movement of forces in different directions when 100N force and lubricants are used under the same conditions. Px takes different values under load. This is observed in all graphs. This phenomenon can be explained by the construction of the case. The diamond is fixed in a bushing that moves along the hole with the force and tilts in different situations. Fluctuations in the radial force Py can also occur due to seizure associated with the bushing, but seizure on the surface of the part associated with tool bending may also occur.

As a result of the study of the touch on the pneumatic tool, it was found that the indicator often skews when the force is applied. This happened due to the design of the case. Visual bending was not observed, as this can occur inside the case. Spring pneumatic tool for external alignment. For diamond grinding, the power element tool in the form of a pneumatic spring and a flexible support is designed for processing the external cylindrical and shaped surfaces of details, as well as the surfaces of eccentrically installed details.

The construction of the tool includes the following: a diamond indenter mounted on a bushing, which, in turn, is firmly fixed on a spring support. The spring support consists of four flat springs, reinforced with plates to prevent contact between the moving part of the frame and its body and the bending of the spring. This support allows you to move around the starting point with a small amplitude: ± 3 mm. Smoothing power is provided by a pneumatic bellows - a hollow metal corrugation. The constant air pressure in the bellows provides a constant pressing force of the working element of the tool against the surface of the workpiece. Constant pressure is achieved by increasing the volume of air in the receiver several times compared to the volume of air in the bellows, thus preventing significant changes in air pressure due to compression of the bellows and reduction of air volume. This should reduce the amount of force fluctuation of the force element compared to the amount of force it generates. A pressure gauge is installed in the receiver to control the pressure in the system.

To determine the required pressure force, it is necessary to select the required pressure in the receiver. There is already a calibration table for this job, so only a check is done. Air leakage from the air system is detected.

On the graph (Fig. 4) a test calibration was carried out using a dynamometer. The pressure is selected relative to the required strength. At first, air was trapped in the system. Then, the measurement process started and the air was gradually removed from the receiver at intervals. The deviation of the force Px, which is a longitudinal force, is a large protrusion of the tool. Based on the tangential component Pz, we can say that the axis of the indenter is below the axis of the machine centers.

Figure 5. Strength test graph

At the beginning of the unilateral movement, the measurement of the force dependence of the grinding force is carried out in the same way as for the bikr operation. Measurements are made according to the following criteria: in the direction of movement; 100N, 200N and 300N according to the level of loading forces; in the information and illustrations on the use of lubricants given. Graphs are shown with 5 times smoothing.

Conclusions. A spring-backed pneumatic tool allows grinding with a constant direction of the force vector. As can be seen from the graphs, the radial component of the Py force remains unchanged during movement. The same thing happens with the friction force during the tangential rotation movement Pz, and the axial force Px for the longitudinal movement of the support. The graph shows the beginning of the movement. The change in the coefficient of friction from the grinding force is the same, but changes depending on the direction of movement.

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