English| Masters of DonNTU | DonNTU | Russian | Ukrainian | English |
| Resume | Abstract |
INTRODUCTION
1. Analysis of modern ways of use in the grinding cutting regimes.
1.1. The classical method for finding the cutting conditions in grinding
1.2. Momentary current limited range of cutting ability
2. Buildung unit elastic pursing grinding wheels to model for internal grinding machines 3A227P.
2.1. Analysis of advanced designs of devices for grinding of elastic scheme
2.2. Development of a design wheelhead 3A227P Internal grinding machines for grinding of elastic scheme
2.3. Modernization of machine 3A227P for electro influences on the working surface of the circle
3. Calculation of the power belt tension links for the transfer of power needed
4. Investigation of power transmission belt tension "motor — grinding head" wheelhead in grinding on plan for elastic force podzhitiya working surface of terms to the surface of a sample
LIST OF REFERENCES
Relevance: Modern production is characterized by the use of materials with high hardness and wear resistance. As a consequence, their chipping causes some difficulties. For finishing materials such as a rule, use sand circles of superhard materials (SHM), which include diamond and cubic boron nitride. While circles are used to metal bond, which requires the use of electro edits and spark effects on the working surface of the circle (WSC)
The scientific significance of the work: At the Department of "Metal Machine and Tools DonNTU proposed a new method of finding the optimal treatment regimes using such thing as " instantaneous current limited range of cutting ability, a mathematical description which can be found by using an elastic circuit grinding. Method is widely used in the search mode vanadiyovih surface grinding of tool steels, carbide, sharpening tools, requires significantly less time compared to the classical method of finding the optimal modes of grinding, but it requires upgrading the machine to implement the elastic grinding circuit.
The practical value of the results: A review has shown, information about the modernization of the Internal grinding machines for elastic grinding circuits, in the literature.
Based on the above, the purpose of master's work is to develop a modernization of the Internal grinding machines 3A227P, which will provide instantaneous current study limited cutting ability of grinding wheels of superhard materials for internal grinding R6M5F3 steel and hard alloys of the VC on an elastic scheme
The input data for the determination of cutting conditions during grinding are: a) information about the processed materialsand dimensions shlifuetmoy surface; b) allowancefor processing and c) the requirements for precision machined surface roughness , andother indicators of quality; d) informationabout the machine; e) the stiffness system machine - detail - a device - a circle; f) the characteristic range of undergoing treatment for a given operation.
Cutting in grinding can be calculated by determining or appointed on the basis of practical recommendations. Calculation mode grinding expedient to carry out the conditions for mass production, where small deviations from the optimal processing requirements can lead to significant losses. Calculation of modes is also advisable to carry out the development of various standards and recommendations relating to the manufacture of grinding wheels.
The problem of determining optimal grinding is done in three stages: 1) Establishing a system of equations that describe the technical limitations imposed on the mode of cutting requirements for parts, machinery, tools and production requirements, 2) mathematical description of the objective function, ie function expressing the goal of optimization, 3) a joint review of technical requirements and the objective function and the definition on this basis the optimum conditions of grinding [1].
Technical limitations imposed on the mode of cutting requirements for products, the following: a) the maximum allowable height of roughness Ra on the machined surface, b) the necessary precision parts after grinding, с) the temperature of sanding the surface, the maximum permissible in terms of burns, residual stress or other indicators of the quality of the surface layer of detail.
Technical limitations imposed on the cutting conditions the machine, the following : a) capacity drive wheel, and b) the highest and lowest frequencies of spindle speed and the value of innings, provided the kinematics and design appropriate mechanisms for the machine (nmax, nmin, vmax and vmin, etc.). Due to the low values ?of the forces generated during grinding, the strength of the mechanism of the machine, as a rule does not limit the cutting conditions. Exceptions may be cases in rough grinding and machining of parts on the machines while grinding some circles.
Technical limitations naoagaemye mode to cut grinding wheel, the following: a) desired tool life, b) limiting the temperature at the cutting grains; strength of the circle.
Set of technical constraints describes the range of possible modes of grinding. If exposed to a complex optimization of the two elements of a regime of cutting, and other elements of the regime are given, then this area represents a flat shape, outlined by the respective lines. Fig. 1.1 in the general form of the scheme of constructing the field of possible cutting conditions when nahodetsya optimal combination of speed parts and cutting depth (lateral flow). Lines in the figure given the name restrictions TO1 - TR3, which were mentioned above. If the optimized set of the three elements of a regime of work, each constraint is described not by line, and the surface of any kind, and the range of possible modes of grinding into a three-dimensional space. With a large number of elements that characterize the mode of cutting, the range of possible modes rotate in four or more dimensional space.
Figure 1.1 - Scheme of possible modes
Target function is a mathematical description of the purpose for which optimizes regime grinding. Depending on the specific conditions of production in the optimization can be achieved at the lowest unit cost of processing the transaction, the achievement in the operation maximum performance, minimum cost of the tool. There may be other specific objectives of optimization.
In most cases, when determining the optimum cutting conditions in order to optimize should be getting a minimum cost operation. Studies in [2] shows that, as a rule, a variant of the cutting, which provides the smallest single-part time with this is the most economical option. Bearing in mind that the solution of the problem for the objective function requires a minimum time, is the most simple, than the objective function, which requires the lowest cost, and results in both cases are close enough, it is useful as a basis for optimization of grinding to achieve maximum process performance.
Calculation of the cutting drastically simplified with fewer variables to be optimized. In this regard, in some cases, keeping in mind that the vast majority of the grinder does not have a device to regulate the spindle rotation frequency range, the calculation of the rate of grinding is not performed, shall be based on practical recommendations.
The disadvantage of the considered classical method of finding the optimum conditions for grinding of new materials or community with new features is that it requires considerable time to find the dependencies, which describe the technical limitations. In addition, it produces results that can not be used when the modes of processing vyhodityat outside, which were found by the equation of technical limitations, but also does not account for the change PKK cutting ability at work.
If diamond grinding processing performance depends on the cutting ability range, so you need to find a parameter regime of cutting, through which it will be possible at any time to equalize treatment of the material that is supplied to remove the expense of workers' movements, and the amount of material that can remove the worktop range due to its cutting ability. For this we use a parameter - the instantaneous current limited cutting ability of a circle [3] - which represents the volume of material removed per unit time, at any time of treatment, at the same time carry out the technical limitations on processing mode quality of the machined surface or a tool (such as temperature threshold for the phase-structural transformations in the surface layer, temperature graphitization of diamond, its durability, etc.).
The most convenient parameter regime grinding, by which to compare the processing performance and cutting ability of the circle is the instantaneous actual depth of grinding. From these calculations, it follows that the change in the actual grinding depth should be implemented discretely through time equal to one of the table with a flat plunge grinding time or one turn of the details - with a round or through them multiple times. When sanding with filing the actual grinding depth should be replaced by a single pass or a multiple thereof.
Definition of modes of the maximum productivity with use of cutting ability of a circle as the limiting parameter is carried out in following stages:
Performing the transition from elastic to rigid schemes, in which the working machine, mass-produced, which is determined by the time one stroke in plunge grinding (pass when sanding with the filing), and then, depending on the regression, calculates the actual grinding depth for each i-th move (pass) during the period of durability of the grinding wheel.
For a flat grinding of elastic scheme circles with a broken surface of the device is used [4], which provides a constant radial force Py (Fig. 2.1).
Fig. 2.1. Device that provides surface grinding with a constant force P [4]
In [5] used the device for compression of the working surface of the PKK in the sample with the diamond-spark grinding.
Fig. 2.2. A device for surface grinding of elastic scheme [5]
To study the cutting ability of the circle of elastic interaction scheme sanding of the sample with the working surface of the instrument used a special device [6] (Fig. 2.3).
Fig. 2.3. Fixture for testing laps on an elastic circuit grinding carbide tips [6]
For grinding of elastic circuit designs with a large arc of contact with the workpiece and the PKK to use the device [5] (Fig. 2.4).
Fig. 2.4. Diagram of the device for grinding with an increased arc of contact on an elastic scheme with a given time [5]
Fig. 2.4. Scheme of the device for grinding with an increased arc of contact on an elastic scheme with a given time [5] Fig. 2.4. Diagram of the device for grinding with an increased arc of contact on an elastic scheme with a given time [5]
Fig. 2.5. A device for grinding with a constant clamping force of the sample to a circle [7]
As noted in [8], hydraulic Poggio sample in terms of providing the most stable damping characteristics as compared with mechanical pidzhatiem through a lever or by a calibration spring
For the implementation of an elastic cylindrical grinding circuit uses the device shown in Fig. 2.6 [9]. It allows you to set a fixed center of the different parts or samples.
Fig. 2.6. Scheme of the device for cylindrical grinding with a constant radial preload [9]
As already noted, the essence of an elastic grinding is that the grinding is performed with a constant force compression of the working surface of the disk to the hot surface, ensuring consistent quality of machined surface during the grinding regardless of time and a simplified way of optimizing treatment regimes.
The problem is solved by the fact that the grinding wheel head is set to head to move relative to the table in the horizontal plane. On the case of fixed loading device, such as cargo, which provides the opportunity of pressing the working surface of grinding wheel to the work surface with a constant force, in addition, the axis passing through the centers of the pulleys of the motor and grinding head, arranged in a vertical plane (Fig. 2.8).
Fig. 2.8 Streamline wheelhead
Using an elastic grinding circuit provides for reducing the complexity of optimal search conditions and improve processing performance of up to 30%.
The proposed grinding head can be applied to machine-building enterprises and in laboratory conditions in research. The design of the head of Ukraine received a patent for an invention.
The essence of the diamond-spark grinding is to combine the cutting process with electroerosion influence on the sample and the instrument through the introduction of a cutting area of pulsed power technology in the environment of conventional grinding Cutting coolant.
Modernization of the machine is to provide a reliable tool for isolation and treated sample from the assembly machine and fed to the cutting area of technological power (Figure 2.9).
Ris.2.9 scheme modernization Internal grinding machines 3A227P
The machine 3A227P sanding head with fixed terms of five isolated from the machine body spacers 6, and three-jaw chuck with sample 4 - Special textolite flange 3.
Technology talk to the instrument is supplied through the graphite brush and the grinding head pulley, and to sample - the chain: "Brush 2 - Ring 1 - chuck. Source of technological current ITT 35, which provides conversion of three-phase AC electric power and frequency in the unipolar pulsed current of 50 Hz is used to perform elekroeroziynoi edits and control actions on the PKK simultaneously with polishing the sample.
In the modernized machine transfer momentum from the electric motor to the sanding head is performed using flat belt drive. In this case, the belt is performed by moving the motor (Figure 3.1)
Figure 3.1 Flat belting Internal grinding machines 3A227P
The methodology used for forces of the belt is put method of calculating the variable transmission as described in [7]. Calculation of force seat-belt pretensioners So, which provide the processing power of 1, 2, and 3 kW performed according to the geometric and kinematic relationships of transmission (Figure 3.2)
Figure 3.2 Scheme for calculating the geometric, kinematic and power relationships of a belt transmission
Figure 3.3 Scheme of the control belt tension
After making all the necessary calculations of force seat-belt pretensioners and boom deflection branch of the belt, the results have brought to the table 3.1
Table 3.1 - Power of the belt and the corresponding deflection of the branches of the belt (G = 49Н, t = 344 мм)
Experimental studies of influence of the belt to force the PKK podizhima to the sample surface was carried out on internal grinding machine 3A227P, modernized for the grinding of the elastic diagram (Figure 4.1). To create a force load wheelhead used loads of different weights. By pressing the PKK to the workpiece surface was measured with a torque table model 100 and the UDM model oscilloscope C8-17. In controlling the strength of branches belt pre-tensioners their loading was carried out using a dynamometer tension and magnitude of deflection measured with dial indicators with a scale division of 0.01 mm (Figure 4.2).
Figure 4.1 General view of the upgraded machine 3A227P with means for studying the effect of force on the belt tension by pressing the PKK in the sample
Fig.4.2. Control scheme forces the belt pre-tensioners
1 - Belt, 2 - load cell elongation, 3 - Indicator
Prior studies performed dynamometer calibration table UDM 100 with a weight (Fig. 4.3, Table. 4.1).
(a)
(b)
Fig. 4.3 The general form of (a) and scheme (b) The dynamometer calibration table UDM 100
1 - cargo, 2 - roller, 3 - dynamometric Table 4 - corps, 5 - oscilloscope
Table 4.1 - Minutes of calibrating torque table UDM 100
According to the table. 4.1 was constructed calibration chart (Fig.4.4) and the least-squares regression equation is found
Figure 4.4 Torque calibration chart table UDM 100
We solve the equation for the force loading. We have:
(a)
(b)
Fig.4.5. General view (a) and scheme (b) study the effect of belt force on force loading wheelhead
1 - cargo, 2 - sanding head, 3 - dynamometric Table, 4 - Oscilloscope
After statistical analysis results tables 4.2 (design criteria Cochran: g1 kW = 0,3389; g2 kW = 0,1083; g3 = 0.3426 kW;-valued criterion Cochran gtabl = 0.5981 [8] for f = 3 and k = 5 = 0.09826) and to determine 95% confidence intervals for the experimental conditions (tcr = 2.02 [9]; s = 0,3134; n = 4; N = ± 0,32) were used to explore the values ??of the relations C = FH / Fn on the force compressing the PKK to the surface and found correlations C = f (Fn) (Fig. 4.6).
Table 4.2 - Effect of belt force to the pressing force the PKK to the sample surface
As seen from Table 4.2, the force compressing the PKK to the surface effect forces the belt, as well as the load grinding head, while with increasing belt force ratio C = FH / Fn increases with the increase of the load - reduced
Fig. 4.6 Effect of clamping force the PKK to the sample surface by the ratio of C = FH / Fn
Using the correlations C = f (Fn), shown in Figure 6, a known force compressing the PKK to the surface, found from the conditions of implementation of technical limitations, we can calculate the power load wheelhead FH.
Accordingly, for the forces of the belt, providing the transmission capacity of 1, 2, 3 kW:
By a known force FH load mass for loading grinding head is given by:
© Благодарный Антон Олегович, ДонНТУ 2011
© Blagodarnyi Anton, DonNTU 2011
| Resume | Abstract |
