ISSN 1068798X, Russian Engineering Research, 2010, Vol. 30, No. 8, pp. 798–799. © Allerton Press, Inc., 2010. Original Russian Text © A.I. Rubakhin, 2010, published in Vestnik Mashinostroeniya, 2010, No. 8, pp. 66–67.

Roughness and Precision when Machining Holes in the Rollers of ContinuousCasting Machines by a Combined Tool A. I. Rubakhin OAO Novolipetskii Metallurgicheskii Kombinat (LPMK), Lipetsk email: [email protected] Abstract—The roughness and geometric precision of deep holes in the rollers of continuouscasting machines produced by a combined tool are investigated. Mathematical models derived from the results per mit the calculation of tolerances on the holes in billet and the parameters of the transforming system on the basis of the required shape precision and surface roughness of the holes. DOI: 10.3103/S1068798X10080113

In the present work, we consider the influence of technological factors—the clearance at the rollers, the machining speed, and the supply—on the roughness and geometric precision of deep holes produced by a combined tool in the rollers of a continuouscasting machine. By reducing the noncircularity of the holes and improving the surface quality and roughness, the performance of the equipment is improved—in par ticular, its life and reliability—and the downtime for roller replacement and repair is reduced. There has been extensive research regarding improvement in shape precision when machining deep holes in cylin drical parts [1–4]. Experiments are conducted on the roughness and geometric precision of deep holes produced by a com bined tool—with drilling and burnishing sections—in a batch of ten rollers on a LR543MF4 drilling machine; the part is based in narrow prisms. The goal of the experiments is to establish the dependence of the roughness Ra of the machined surface, the deviation ε of the hole’s longitudinal profile, the plastic deforma tion δ, and the deviation of the cross section Δ on tech nological factors: the clearance at the rollers i, mm (i = d – dini, where d is the tool diameter at the rollers, mm; dini is the hole diameter after passage of the cutting part of the tool, mm); the supply S, mm/turn; and the machining speed v, m/min. Analysis of the experimental data yields powerlaw regression equations δ = 0.0209i ε = 0.0406i

0.2325 – 0.2202

S

– 0.3293 0.3115

S

Ra = 0.4634i Δ = 0.5261i

v

v

– 0.4250 0.4169

S

– 0.3864 0.3695

S

0.1919

;

– 0.2509

v

v

(1)

;

– 0.3604

– 0.3921

.

(2) ;

(3)

δ, mm 0.050 0.045 0.040 0.035 0.030 0.025 0.020 ε, mm 0.040 0.035 0.030 0.025 0.020 0.015 0.010 Ra, mm 0.350 0.300 0.250 0.200 0.150 0.100 0.050 Δ, mm 0.350 0.300 0.250 0.200 0.150 0.100 0.050 0

(a) 1 3 2 4

(b)

4 2 3 1 (c)

4 2 3 1 (d)

4 2 3 1 0.01

0.02

0.03

(4)

In obtaining the regression equations, we employ the upper and lower boundaries of the ranges for the tech 798

Fig. 1.

0.04

0.05

0.06 i, mm

ROUGHNESS AND PRECISION WHEN MACHINING HOLES IN THE ROLLERS

nological factors. Excel software is used for computer analysis of the data. From the results, we plot the rough ness Ra of the machined surface (c), the deviation ε of the hole’s longitudinal profile (b), the plastic deforma tion δ (a), and the deviation of the cross section Δ (d) as a function of the following technological factors (Fig. 1): 1) v = 90 m/min; S = 0.05 mm/turn; 2) v = 90 m/min; S = 0.15 mm/turn; 3) v = 50 m/min; S = 0.05 mm/turn; 4) v = 50 m/min; S = 0.15 mm/turn. According to Eq. (1), the plastic deformation δ increases with increase in i, and declines with increase in S and the machining speed v. According to Eqs. (2)–(4), Ra, ε, and Δ decrease with increase in i but increase with increase in S and v. The factor with the greatest influence on δ, Ra, and ε is i; the factor with the greatest influence on Δ is v. The factor with the least influence on δ, Ra, and ε is v; the factor with the least influence on Δ is S.

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The experimental results indicate that the mathe matical models in Eqs. (1)–(4) permit the calculation of tolerances on the holes in the blank and the param eters of the transformation system on the basis of the required shape precision and roughness of the hole. REFERENCES 1. Osnovy tekhnologii mashinostroeniya (Manufacturing Principles), Korsakov, V.S., Ed., Moscow: Mashinos troenie, 1965. 2. Vittenberg, Yu.R., Correlation Characteristics of the Surface Roughness and Their Relation to Technologi cal Factors, Vestn. Mashinostr., 1970 no. 2, pp. 57–59. 3. Granovskii, V.A. and Siraya, T.N., Metody obrabotki eksperimental’nykh dannykh pri izmereniyakh (Analysis of Measurement Data), Leningrad: Energoatomizdat, 1990. 4. Suslov, A.G. and Dal’skii, A.M., Nauchnye osnovy tekhnologii mashinostroeniya (Manufacturing Princi ples), Moscow: Mashinostroenie, 2002

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