The influence of the constructive and technological parameters of the tool system on the surface finish at grinding.

Buzatu, Constantin ; Bancila, Daniel

1. INTRODUCTION

It is shown that to increase the reliability and the working life of the parts, which have an important functional role in the engineering equipment structure, they are subjected to surface treatments and grinding operation to improve their dimensional accuracy.

The optimization of grinding operation requires even from the design step, the knowledge of the quantitative and qualitative influence of the factors that determine the technological parameters which give the accuracy needed to the parts according with the technical requirements (Buzatu, 1981).

To improve the parts quality it is possible to modify the technological and constructive parameters of the grinding operation.

Besides the technological and constructive parameters of the grinding operation, the influence of the cooling liquid has been least researched under quantitative aspects, an applicative study being imposed.

Based on these considerations, in the paper are presented the theoretical and experimental studies and researches regarding the influence of these technological and constructive parameters on the surface finish.

2. THE THEORETICAL EQUATION OF THE ROUGHNESS SURFACE OBTAINED IN GRINDING OPERATION

Based on the theoretical modelling of machining process with abrasives, in the conditions of simplifying assumptions (Secara et al., 1989), according with the schematic illustration from fig.1 and after a series of theoretical calculations (Buzatu et al., 2007), the next equation for the maximum height of the profile Ry, at grinding cylindrical surfaces was found:

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (1)

where: t--is the depth of cut, in mm, [S.sub.l]--is circular feed of work piece in mm/sec, [V.sub.s]--is angular speed of tool in mm/min, e--Gmed = average dimension of the abrasive grain from the grinding wheel in [micro]m, D--is the grinding wheel diameter in mm, k1 = 0.7--0.9 is a coefficient that depends of the number of abrasive grains that work at maximum capacity, [mu]--is the friction coefficient between abrasive grain and work piece surface in the presence of cooling liquid, [gamma]--is the rake angle of the abrasive grain in radians(fig.1).

[FIGURE 1 OMITTED]

3. STUDY REGARDING THE INFLUENCE OF TECHNOLOGICAL AND CONSTRUCTIVE PARAMETERS ON THE SURFACE ROUGHNESS AT INFEED GRINDING

The Ry equation (1) can be written synthetically as:

Ry = h = f ([S.sub.l], [V.sub.s], t, [mu], D, e) (2)

where, [S.sub.1], [V.sub.s], t and [mu], represent the technological parameters, D and e, are the constructive parameters of the too, system. Taking into account the values recommended in the literature (Vlase et al., 1985), (Picos & Pruteanu, 1992), which are used frequently at grinding ([S.sub.1] = 0.001--0.075 mm/rev; [V.sub.s] = 0.0005 - 0.002 m/min; t = 0.1--0.4 mm; e = 100--300 [micro]m; D = 200 500 mm; [micro] = 0.01--0.2), if fig. 2--fig. 7 are shown the graphical dependences between roughness and variable parameters from equation (2) in certain working conditions.

Also, using a special software were deducted the mathematical models of these dependences, adopted based on the optimal correlation coefficients presented on the graphical dependences.

[FIGURE 2 OMITTED]

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In fig. 8, the dependence of the roughness Ry = h, according to all considered parameters is shown.

Also, from fig.8 results the optimal domain of values to obtain the roughness at grinding between Ra = 0.8--1.6 um.

By using the mathematical models and data of different parameters (technological and constructive), other bi or three dimensional graphic dependencies can be obtained.

[FIGURE 7 OMITTED]

[FIGURE 8 OMITTED]

4. OBSERVATIONS AND CONCLUSIONS

Based on the previous data the next observations arise:

--The graphical dependencies from fig.2--fig.7 and their mathematical models present an optimal choice of the cutting and constructive parameters of tool according with the requirements of the part design;

--It can easily be observed (fig. 5), that the cooling liquid has an important influence on the roughness of the surface;

--The friction coefficient u has a great influence on the roughness and it depends on the cooling liquid characteristics.

5. REFERENCES

Buzatu, C. (1981). Contributions on the factors study which affect increasing the accuracy of parts made by turning and external grinding. Doctoral thesis, Transilvania University of Brasov, Brasov, 1981

Buzatu, C.; Lepadatescu, B. & Dumitrascu, A.E. (2007). Studies regarding the influence of the process parameters on the surface roughness at manufacturing by grinding, Annals of DAAAM for 2007& Proceedings, pp. 127--128, ISBN 3-901509-58-5

Picos, C.; Pruteanu, O. (1992). Design of manufacturing technologies. Design handbook, Universitas Publishing House, ISBN 5-362-00971-0, Chisinau

Secara, Gh.; Rosca, D.; Mares, Gh.; Ditu, V.; Bodocan, S.; Lupulescu, N.B. & Deaconu, V. (1989). Fundamentals of cutting and surface generating, University of Brasov

Vlase, A.; Sturza, A.; Mihail, A. & Bercea, I. (1985). NCutting parameters stock removal and cutting time, Technica Publishing House, Bucharest.