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To increase productivity and the material removal rate, an increasing number of factories have been employing multiple tools for simultaneous cutting. Among these tools is parallel orthogonal turn-milling, which is an important parallel-processing method. However, a dynamic interaction occurs during the cutting processes due to the waviness induced on the shared cutting surface and the dynamic coupling through the machine structure, creating machining vibrations, or chatter, which affect the quality of the machined surface. Therefore, to reduce or avoid the vibration problem during the cutting process, chatter stability of parallel orthogonal turn-milling was examined in this study. Initially, a chatter mechanism model of parallel orthogonal turn-milling was designed, and the limit-critical axial depth of the cut formula was obtained. Next, the model parameters of the machine tool were obtained based on the hammer test method. A parallel orthogonal turn-milling stability lobe diagram (SLD) with tool tip runout was constructed. Finally, the experimental results were verified on a high-efficiency turn-milling machine tool. The results showed that chatter can be predicted for parallel orthogonal turn-milling and an SLD can provide a reference for the selection of machining parameters. In addition, the SLD can also guide the formulation of processing technology specifications. Our results are extremely significant for ongoing research in the field of machining methods.

To study structural seakeeping stability of the marine compound NC machine tool in the ship environment, this research analyses the effects of extreme wave loads including transient slamming and harmonic swings on the machine tool, and the coupling methods of transient reaction, static structural analysis and harmonic response are used to solve the problems. The results show that the major guide pairs of the column are the weakest parts in the machine tool in a ship environment, so the column working deflection angle of the machine tool should be consistent with the ship heading angle to reduce influence of wave loads on dynamic stability of the machine. The data indicate that the minimum safety factor is 3.43 under an extreme surge acceleration of 41.8 m/s2, and the normal safety factor of 3.0 shows that the guide pairs are able to endure extreme slamming wave loads of H1/3=7.6 m at the maximum velocity of the ship. In addition, the machine tool has a maximum deformation of 0.032 mm and a peak stress of 5.07 MPa under extreme harmonic wave excitation. Importantly, the machine's cutting accuracy was suitable for the rapid manufacturing requirement to maintain a ship's broken components.

Arc spraying of Fe-Al-based coatings is widely used in for remanufacturing and other requirements due to its high performance; however, the bond strength between coating and substrate is about 50 MPa, so the changes therein are important in the cutting process. Moreover, such coatings are thin, and their surface is coarse, so this predefines two cutting steps in any subsequent machining process. It indicates that three factors affect the bond strength including the following: machine tool natural vibration, cutting tool regenerative vibration, and forced vibration due to the rough surface. This work presents a spindle-tool-workpiece vibration model of the coating machining process and studies the effects of transient cutting force, residual stress, and cutting parameters on the bond strength. The results show that the transient maximum influence of cutting force on the bond strength is 7.27 MPa, and the residual stress affects the material to a depth of 1.6 mm. Then, a bond strength calculation model was obtained to calculate the bond strength reduction as induced by choice of cutting parameters. The calculation model was verified experimentally, and it was shown that cutting depth was the main factor affecting bond strength. Combined with SEM inspection, this work showed that the interface gap was amplified during cutting. Importantly, to achieve the necessary bond strength, the first cutting depth should be less than 0.1 mm (allowing for the surface dimensional difference), and the cutting depth of other cutting steps should be less than 0.2 mm; in addition, the finishing coating thickness should be more than 0.2 mm.

The arc-spraying Fe–Al-based coating cutting process is a spindle-tool-workpiece vibration system dependent upon the machine tool's dynamic performance, cutting tool vibration, the coarse coating surface and its thin cutting depth. To investigate the cutting force, this research indicates the coating cutting fundamental mechanics; furthermore, it represents two cutting steps and cutting force models in the machining process avoiding an analysis of the natural vibration parameters of the machine tool itself. In the first cutting step, there is a transient cutting force due to forced vibration of the rough surface; the second cutting step has a steady machining feature based on the first cutting surface and the reduced hardness of the inhomogeneous region. According to the different characteristics of each cutting step, this research presents dynamic cutting calculation models including cutting parameters, tool vibration and cutting depth effects in the first cutting step. A steady cutting model is based on three cutting parameters including cutting velocity, cutting feed and cutting depth. Piezoelectric force and acceleration sensors were used to obtain accurate experimental data. Then, response surface methodology (RSM) and the principle of least squares estimation of polynomial regression (PLSEPR) were applied to analyse the resultant cutting data. The results showed that cutting force calculation models were suitable for the coating machining.