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

Tabacaru, Lucian ; Nedelcu, Dumitru

1. INTRODUCTION

Vibro-honing is a technological finishing which uses a set of abrasive or diamond bars interlinked, mounted in a vibro-honing head. This device (the head) ensures continuous contact between the set of bars and the piece surface. It has several working speeds (equation 1).

Two components of the cutting speed, the longitudinal speed [v.sub.1] and the tangential speed [v.sub.t];

A high frequency oscillatory movement, of low amplitude, with oscillatory speed [v.sub.0]. This supplementary movement could be either the piece or the vibro-honing head.

Equation (1) represents the optimal ratio which should exist between the three working speeds (Yokoyamak., 1983, 1989).

[v.sub.t] : [v.sub.o] : [v.sub.1] = 3 : 2 :1 (1)

2. TECHNOLOGY USE

During the experiments the high oscillations were made by the piece. Figure 1 depicts the mechanical device designed and used during the experiments. Its functional scheme is represented in Figure 2.

The permanent contact between the pick-up roll and frontal cam 3 is made through a set of spiral springs. A change in the frontal cam speed will modify the frequency. The amplitude could be changed by mounting or descending the roll on the cam and can be set through a radial movement of the pick-up device.

Figure 2 presents the formulae for the calculus of oscillatory speed.

[v.sub.o] = a[omega] = [a[pi]n.sub.cama]/30 = [A[pi]n.sub.cama]/60 [m/min.] (2)

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

[FIGURE 3 OMITTED]

1.1 The honing machine. For testing it, we used a single axis, vertical honing machine, model ZG 833 (figure 3) 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 4 shows a 6 bars honing head actually used in the research, covering a diameter range between 95 and 110 mm; its main elements are:

1.3 Abrasive bars. The bars were 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 1083 - 93 - [[PHI].sub.int] = 95 mm., [[PHI].sub.ext] = 115mm, L=140 mm.

Before vibro-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 roughnesses obtained after lapping, as an average of 10 measurements varies [R.sub.a]=4.83 - 4.63 [micro]m.

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

a. Tangential speed

[FIGURE 4 OMITTED]

Considering the number of rotations/ min available on the honing machine (155, 280, 400 rot/min) and the working diameter, there had been obtained three values 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. Oscillatory speed. During the research there had been used the following values for oscillatory speed: [v.sub.0] = 30.84; 55.70; 79.58 [m/min]

d. 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=52daN, 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

A mixture of kerosene (60 1) and oil (8 1) in a proportion of 86.6% kerosene was used.

3. Data analysis. In order to obtain a general equation [AF.sub.c]=f([v.sub.t], [v.sub.l], [v.sub.0]) and [AF.sub.1]=f([v.sub.t], [v.sub.l], [v.sub.0]) a computer software was developed using TURBO PASCAL. The following equation was found using the software (Pruteanu & Nedelcu, 1996):

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (3)

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (4)

[FIGURE 5 OMITTED]

[FIGURE 6 OMITTED]

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

3. CONCLUSIONS

The longitudinal speed and the tangential speed influence the circularity deviation the same way the honing process does for small speed values. For oscillatory big values of speed and tangential big values of tangential speed, the curve is changeable, the increasing of the longitudinal speed leads to increasing the circularity deviation. Around the values of longitudinal speed about Vl=11,5m/min when the deviation value remains constant.

The smallest values of circularity deviation were obtained taking into account the following parameters: tangential speed 83,56 m/min; longitudinal speed 11,5 m/min; oscilatory speed 30,84m/min; the minimum value of circularity deviation obtained (1,7-2) um.

4. 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 cutiing 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