The influence of working parameters on precision in processing short, circular honing, processing of pieces made of cast iron 200.

Tabacaru, Lucian

1. INTRODUCTION

One of the main issues of the technical progress in Machines design is the mechanism and device reliability of the machine--tool. In order to satisfy these increased requirements the hole accuracy most be enhanced. Based on this assumption there is a need to improve the machining technology. Honing is a technological process which provides high precision. Thus the study of the influence of working parameters on surface quality will lead to a better accuracy of short interior circular surfaces.

2. TECHNOLOGY USE

Honing is a surface finishing process using a set of abrasive bars or diamonds, interlinked, and assembled in a honing head. The hydraulic pressure ensures the permanent contact between the head and the surface to be machined. There are two main movements of the honing head: spinning at the speed [v.sub.t] and rectilinear alternative movement at the speed [v.sub.1]. Appropriate lubrication is used for cooling and oiling. There are several important characteristics of the honing process (Yokoyamak, I., 1983 & Yokoyamak, I., 1989).

* A large surface between the surface and honing bars;

* Low pressure upon the surface to be machined,

* Low cutting speeds.

These characteristics lead to:

* Low surface roughness;

* Increased dimensional accuracy;

* Correction of initial geometrical errors;

* Relative high productivity.

1.1 The honing machine. For testing, it was used a single axis, vertical honing machine, model ZG 833 (figure 1) design for diameters range 30 to 165 mm of the pieces which could be assembled on the machine table

1.2 The honing head. Figure 2 shows a 6 bars honing head actually used in the research, covering a diameter range between 95 and 110 mm, its main elements are:

1--double cone action rod;

2--honing head;

3--driving bolt;

4--abrasive bar holder;

5--abrasive bar;

6--spring for continuous contact between the bar support and the double cane plunger pin;

7--elastic element for plunger return to initial position during the time when it does not work;

1.3 Abrasive bars. The bars are produced by S.C. ABROM Birlad and have the following technical specifications: 22C180[J.sub.6][V.sub.18][T.sub.3], and the size 100x13x13.

1.4 Working material. The piece is made of cast iron: 200 SR ISO 185 - 94 - [[PHI].sub.int] = 95 mm., [[PHI].sub.ext] = 115 mm, L=140 mm.

[FIGURE 1 OMITTED]

Before honing, the piece had been fine turned using the following working parameters: n=63 rev/min. s=0.1 mm/rev., t=0.25 mm tip radius r=2 mm. The roughness obtained after lapping, as an average of 10 units varies [R.sub.a]=4.83 - 4.63 [micro]m.

1.5 The working parameters (Tabacaru, L., 1998 & Tabacaru, L., Pruteanu, O.V., 2004)

a. Tangential speed

Considering the number of rotations/ min available on the honing machine (155, 280, 400 rot/min) and the working diameter three values had been obtained for tangential speed: 46.25, 83.56 and 119.37m/min.

b. Longitudinal speed

There are three speeds available on the honing machine ZG 833 (8,11.5 and 18 m/min).

c. Pressure--can be computed using the equations: p = Fn/A = S/A; S = Q/ tg ([alpha]1 + [phi]>1) + tg ([alpha]2 + [phi]2) = 43/ 0,826 = 52 daN

p = 52/ 10x1,3 = 53/ 13 = 4 daN /[cm.sup.2]

For all experiments the pressure had a constant value.

d. Machining time

Machining times used was 1; 2; 3; 4; 5 min.

e. Cooling liquid

[FIGURE 2 OMITTED]

[FIGURE 3 OMITTED]

[FIGURE 4 OMITTED]

It had been used a mixture of kerosene (60:1) and oil (8:1) in a proportion of 86.6% kerosene.

1.6 Experimental research on the influence of working parameters on precision in process.

To study the deviation from circularity [AF.sub.c] in processing by honing of cylinders using the vertical honing machine (Pruteanu, O.V., Nedelcu, D., 1996)., model ZG 833 (figure 1), it was used a Russian production coordinate holing machine, model 2D-450 and a measurement machine including three main elements: the palpation element, the dial comparative with a precision of 0,001 mm and the element to catch hold of tool machine. It was used the coordinate holing machine model 2D-450 because it was possible the adjustment on the two directions 0x and 0y, with a precision of 1 [micro]m, and the superposition of the revolution axis of the piece over the rotation axis of measurement machine.

The measurements were effected at every 300, for the two sections A and B (figure 3).

The influences of the longitudinal speed upon circularity in two different sections are presented in figure 4 and 5.

[AF.sub.C] = 30,9205 - 0,2652574 [V.sub.t] + 1,816299E-03 [V.sup.2.sub.t] - 3,540013 [V.sub.1] + 0,1507697 [V.sup.2.sub.1] [s.sub.min] = 1,300001 (1)

[AF.sup.t] = 42,84639 - 0,3685379 [V.sub.t] + 2,660099 E-03 [V.sup.2.sub.t] - 4,887184[V.sub.1] + 0,2037378 [V.sup.2.sub.1] [s.sub.min] = 2,091666 (2)

3. CONCLUSIONS

1. Referring to the honing operation, the values of longitudinal speed parameter are greatest than the values of tangential speed parameter and reveals that longitudinal speed has a great influence on deviation from circularity and cylindricality than the tangential speed parameter. We could affirm that longitudinal speed influences 13-14 fold the deviations from circularity and 10-11 fold the deviation from cylindricality than the tangential speed.

2. An increase of longitudinal speed leads to a decrease of deviation from circularity to a certain value [V.sub.1] = 11,5 m/min. An increase over this value leads to an increase of deviations from circularity.

3. An increase of tangential speed leads to a slowly decrease of deviations from circularity values to the value [V.sub.t] = 83,56 m/min A continuous increase of tangential speed determines a faster increase of deviations from circularity.

4. The lowest values of the deviations from circularity were obtained for the following values of the working parameters: tangential speed:

[V.sub.t] = 83,56 m/min Longitudinal speed:

[V.sub.j] = 115 m/min The minimal deviation from circularity:

[AF.sub.c] = 1,4/h 2 [micro]m

[FIGURE 5 OMITTED]

On the future I want to develop this research for others metals like steel with industrial implementation on machine manufacturing.

5. REFERENCES

Pruteanu, O.V., Nedelcu, D., (1996). The stress analysis on deformation roll, Proceedings of 7th International DAAAM Symposium, Katalinik, B. (Ed.), pp. 361-362, ISBN 3-901509-02-X, Vienna, Austria, October 1996, Vienna

Tabacaru, L., (1998) Studiul comparative intre honuirea si vibrohonuirea suprafetelor interioare de revolutie, scurte, The comparative study between the honing and vibro-honing of interior surfaces, short, Ph.D. Thesis, Iasi

Tabacaru, L., Pruteanu, O.V., (2004), The influences of cutting speed on the efficency of superfinishing, Bulletin of Politechnical Institute, Fasc. 1-2, pp. 34-38, Iasi

Yokoyamak, I., (1983) Analyses of Thermal Deformation of Workpiece in Honing Process (2nd Report) "Bulletin of the Japan Society of Precision Engineering" V17, No 4, pp. 56-60, Publishing Japan Society, Japan

Yokoyamak, I., (1989) Analyses of Thermal Deformation of Workpiece in Honing Process (5th Report) "Bulletin of the Japan Society of Precision Engineering", V22, No 1, pp. 60-64, Publishing Japan Society, Japan