PSI - Issue 81

Igor Stoiko et al. / Procedia Structural Integrity 81 (2026) 447–454

453

b L

use the diagram (Fig. 6) and formula (14), meaning:  + The achievable accuracy of the CA angle is determined using the scheme (Fig. 8) considering centering error Δγ . 2 0,76 0,02. i D  =

Fig. 7. Locating scheme for curved axis using two centers in the plane of symmetry and an axial center.

The tolerance for the angle of intersection of geometric axes Δ γ obtained by this locating scheme equals the sum of angle tolerances 2  for machining from both sides and the angular centering error of the workpiece Δ γ : 2 ;      =   ; 2      =− = − . (16) cos ; i x L +  = cos . 2 x L  =  Using (14), the following equations are obtained: 2 cos 0,76 0,02 2 arccos . D L L   +  +  = (17) Then from (16) it is obtained: 2 cos 0,76 0,02 2 arccos . 2 D L L    +  +   = − (18) Substituting data (19) into (16), the achievable deviation of the angle of intersection of geometric axes for this locating scheme is obtained: 2 cos 0,76 0,02 2 2 arccos . D L L       +  +     = −           (19) The analyzed locating schemes for curved axes using three center holes can be practically applied independently of one another. In each specific case, it is necessary to consider the axis design and other structural elements that complicate the application of a particular scheme. Furthermore, before selecting a machining scheme, it is advisable to verify the achievable axis angle accuracy for different locating schemes using the calculation methods examined thus far, comparing them with the specified requirements.

a)

b)

Fig. 8. Machining of curved axis using three centers: a – fixture scheme for turning operations; b – turning of the axis.

Comprehensive experimental investigations have established the magnitude of the offset coefficient for machining using three center holes, which has the following values: К ZM = 0,007…0,01 for workpiece centering on a vertical drilling machine using a rotary indexing fixture; К ZM = 0,004…0,006 for workpiece centering on a machining center type machine tool. A dedicated software suite was used to investigate the stress – strain state of a curved axle. The analyses were performed in the