Within analysis of secondary machine elements the bearing seats of the gear shaft were investigated. Alternative manufacturing technologies for the finish process of the bearing seats were also evaluated. The technologies had to meet a number of requirements and conditions, including:
? Material: case-hardened steel 20MnCrS5
? Surface hardness: HRA 81-83
? Surface roughness: Rz = 2 μm
? Concentricity: 0.02 mm ? Circularity: 0.004 mm
? Parallelism: 0.06 mm ? Retain fitting tolerance
? Retain accuracy grade of cylindrical shaft
? Right angularity tolerance of contact surfaces
? Free of damage and pores
? Economic manufacturing
During rough analysis, five manufacturing technologies were identified that are able to manufacture the bearing seats with the necessary requirements.
Because the project’s focus was on innovative manufacturing technologies and conventional processes (grinding, hard-turning), a hybrid manufacturing process known as “ultrasonic-assistedturning” was considered. In addition, a second process step was considered for manufacture of the surface proper- ties should the first process step prove incapable of meeting all requirements. For this step, hard-roller burnishing—a process not yet common to this field— was employed. Within rough analysis the manufacturing technologies were assessed considering the impact factors. This assessment was conducted by experts from the industry and research institute. The results show that hard-turning and plunge-grinding are the preferred manufacturing processes. As a possible second step, hard-roller burnishing should be used (Fig. 3).
Figure 1 Calculation result.
Figure 2 Alternative manufacturing technologies for bearing seats.
Figure 3 Results of rough analysis
Figure 4 Results of surface roughness tests.
To assess the surface quality that can be achieved with the manufacturing technologies discussed here, a Fourier analysis was performed, enabling assessment of the possible surface roughness of the bearing seats. The advantages and disadvantages of these alternative manufacturing technologies are listed below; results of the surface roughness tests are shown in Figure 4.
? Hard-turning without ultrasonic sup- port
? Low ripple
? Higher amplitudes during lower wave numbers
? Ripple is influenced by self-excited (regeneration effect) and separately excited (imbalances, SLS-radial deviation) oscillations
? Quick point grinding
? Higher amplitudes than ecp. longitudinal grinding are machine-based
? Higher machine stiffness
? Lower oscillations than ecp. longitudinal grinding
? Ultrasonic-assisted turning
? Low fundamental oscillation
? Very good concentricity
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