Various cutter strategies have been developed during milling freeform surface. Proper selection of the cutter path orientation is extremely important in ensuring high productivity rate, meeting the better quality level, and longer tool life. In this work, finish milling of TC17 alloy has been done using carbide ball nose end mill on an incline workpiece angle of 30°. The influence of cutter path orientation was examined, and the cutting forces, tool life, tool wear, and surface integrity were evaluated. The results indicate that horizontal downward orientation produced the highest cutting forces. Vertical downward orientation provided the best tool life with cut lengths 90–380 % longer than for all other orientations. Flank wear and adhesion wear were the primary wear form and wear mechanisms, respectively. The best surface finish was achieved using an upward orientation, in particular, the vertical upward orientation. Compressive residual stresses were detected on all the machined surfaces, and vertical upward orientation provided the minimum surface compressive residual stress. In the aspect of tool wear reduction and improvement of surface integrity, horizontal upward cutter path orientation was a suitable choice, which provided a tool life of 270 m, surface roughness (Ra) of 1.46 μm, and surface compressive residual stress of −300 MPa.

This paper investigates grinding force and grinding temperature of ultra-high strength steel Aermet 100 in conventional surface grinding using a single alumina wheel, a white alumina wheel and a cubic boron nitride wheel. First, mathematical models of grinding force and grinding temperature for three wheels were established. Then, the role of chip formation force and friction force in grinding force was investigated and thermal distribution in contact zone between workpiece and wheel was analyzed based on the mathematical model. The experimental result indicated that the minimum grinding force and the maximum grinding force ratio under the same grinding parameters can be achieved when using a CBN wheel and a single alumina wheel, respectively. When the phenomenon of large grinding force and high grinding temperature appeared, the workpiece material would adhere locally to the single alumina wheel. Grinding temperature was in a high state under the effect of two main aspects: poor thermal properties of grinding wheel and low coolant efficiency. The predicted value of grinding force and grinding temperature were compared with those experimentally obtained and the results show a reasonable agreement.

Residual stresses induced by finish machining processes have significant effect on fatigue strength of ultra-high strength steel in large structures. In this study, an experimental investigation was carried out to explore the residual stress and affected layer in grinding Aermet100 by using a resin bond white alumina (WA) wheel and cubic boron nitride (cBN) wheel, respectively. The grinding force and temperature were measured, and then the affected layer of residual stress, microhardness, and microstructure by a WA and a cBN wheel was obtained. The comparisons of surface residual stress studies and thermal–mechanical coupling mechanism on the affected layer were discussed in light of the current understanding of this subject. Experimental results show that grinding with cBN wheel can provide compressive residual stress and a smaller affected layer owing to its better thermal conductivity; the coupling effect of wheel speed and grinding depth plays a more significant role on surface residual stress; when grinding with parameters vw = 18 m/min, vs = 14 m/s, and ap = 0.01 mm, compressive residual stress and hardening effect appeared on ground surface, and the depth of residual stress layer is 40~50 μm; the depth of hardened layer is 30~40 μm and the depth of plastic deformation layer is 5~10 μm.

The great mass of machining allowance for blisk is removed in the rough milling, so improving the rough machining efficiency for the blisk’s tunnel is the key of realizing high-efficiency machining of blisk. According to the structure characteristic of open blisk’s tunnel, a four-axis plunge slot rough milling with high-efficiency and low machining cost is advanced. First, the plunge slot process for blisk and the generation process of the ruled enveloping surface for the freeform surface of the blisk’s blade are put forward. Then, the generating method of the ruled enveloping surface for the blade’s freeform surface and the tool path generation method of four-axis plunge slot milling for blisk are studied. The rough milling region of open blisk’s tunnel is determined by generating the ruled enveloping surface of blade’s offset surface, and the algorithm of tool path for four-axis plunge milling is given. When using a ruled surface to approach a freeform surface, the problem of getting boundary is solved, and the error from the calculation of tool path is avoided by the algorithm. At last, the experiment shows that comparing to the traditional side slot milling, the cutting force of four-axis plunge milling can be reduced by 60% and even the rough machining efficiency can be increased to more than double.

•An integrated multi-objective optimization method is developed.•Surface integrity of multi-axis ball-end milling Inconel 718 is optimized.•Grey relational grade is significantly improved by 62.87%.•The proposed method shows a larger advantage than that of the original GRA.Multi-axis ball-end milling is the most commonly used operation in machining aerospace engine parts. Because of multi-output characteristic, the process improvement often requires multi-objective optimization. Recently, the grey relational analysis (GRA) has been more and more widely used in engineering manufacture with multiple responses. But, the original GRA method only suits for the optimization problem in discrete space. This paper proposes an integrated multi-objective optimization method with GRA, radial basis function (RBF) neural network, and particle swarm optimization (PSO) algorithm. Compared with the original GRA, it expands the optimal solution space to continuous space. This approach is subsequently applied to the multi-objective optimization of multi-axis ball-end milling Ni-based superalloy Inconel 718. The purpose is to simultaneously obtain minimum surface roughness and maximum compressive residuals tress by optimizing the inclination angle, cutting speed, and feed. A hybrid experiment scheme with single factor design and orthogonal array is utilized to generate the sample data set. The multi-response optimization problem is successfully converted into the single objective optimization of grey relational grade (GRG). Then, the RBF neural network is employed to establish the mapping relation between the GRG and the process parameters. And its adequacy is proved by five test experiments with a low prediction error of 6.86%. Finally, the PSO algorithm is adopted to optimize the process parameters. Verification experiments show that a higher improvement of the GRG is obtained with the proposed method (62.87%) than that of the original GRA (50.00%). The developed approach is proved to be feasible and can be generalized for other multi-objective optimization problem in manufacturing industry.

Compressive residual stress is important to improve the fatigue life of components. This paper proposed an empirical model to predict the compressive residual stress profile induced by the integration manufacturing processes (firstly milling, then polishing, finally shot peening). An exponential decay function was used to describe the compressive residual stress profile induced by milling process. Moreover, a sinusoidal decay function was proposed to describe the compressive residual stress profile induced by shot peening process. The integration manufacturing processes model was a deterministic function of the combination of exponential decay function, sinusoidal decay function, and their interaction term. Additionally, an impact coefficient was introduced to describe the influence of polishing process on compressive residual stress profile. The coefficients of the proposed models were related to the input machining parameters. Experiments of TC17 alloy were carried out utilizing response surface methodology and full factorial design to construct these models. Flank wear, tool inclination angle, axial depth of cut, shot peening intensity, and shot peening coverage were selected as five input machining parameters. According to the experimental results obtained, the evolution of compressive residual stress profile after the integration manufacturing processes was investigated, and the proposed models had been developed. The empirical model was validated by two extra experiments and a significantly good prediction was achieved.

During milling process of ball end mill, the tool orientation is important to the surface quality of workpiece. In this work, a series of milling experiments are done by carbide ball end mill on a workpiece of titanium alloy TC17, using the rotational angle and the inclination angle of tool axis to describe the tool orientation and the effect of tool orientation on surface integrity are studied. The results show that the surface roughness in both directions (feed direction and step direction) is optimal when the rotational angle is within the scope of 0° to 90° with a constant inclination angle. The change of the inclination angle has little effect on the roughness in feed direction, but much larger or smaller angle leads to a bigger roughness in step direction. The various tool orientations have an enormous impact on surface morphology. Compressive residual stress can be detected on all machined surface during changing the rotational angle and reached the maximum when it is 90°. The surface residual stress reduces with the increase of the inclination angle. The tool orientation makes little effect on the microhardness due to the lower degree of work hardening.