Thin-walled parts have been widely employed as critical components in high-performance equipment due to the high specific strength and light weight. However, owing to their relatively weak rigidity and poor damping properties, chatter vibration is likely to occur during the milling process, which severely deteriorates surface quality and decreases machining productivity. Therefore, chatter suppression is essential for improving the dynamic machinability of thin-walled structures and has attracted extensive attention over the past few decades. This paper reviews the current state of the art in research concerning chatter suppression during the milling of thin-walled workpieces. In consideration of the dynamic characteristics of this process, the challenges in design and application of chatter attenuation methods are highlighted. Moreover, various chatter suppression techniques, involving passive, active, and semi-active methods, are comprehensively discussed in terms of basic concepts, working mechanism, optimal design, and application. Finally, future research opportunities in chatter mitigation technology for thin-wall milling are recommended.

Due to the advantages in weather resistance, light transmittance and dimension stability, PMMA has been widely used in various fields such as aerospace and optical engineering. However, fully automatic robot systems are seldom used for polishing complex PMMA parts with high surface integrity. Therefore, a robotic polishing system with a new active end-effector is developed in this paper. In the system, a 6-degree-of-freedom industrial robot is utilized to polish the part profile along the preprogrammed paths, and then the system configuration is introduced in detail. For precisely controlling the normal contact force, both a linear voice coil motor and a force sensor are used in the designed end-effector. Meanwhile, a tilt sensor is also used to compensate the gravity component of the polishing tool along the force-controlled direction. Subsequently, a hybrid force controller, which consists of a PID controller and a Fuzzy controller, is designed to maintain the contact force between the polishing tool and the part within an allowable range. Finally, validation experiments are conducted with the designed robotic polishing system on a complex PMMA part. The experimental results show that the proposed robotic polishing system can strictly control the normal contact force and ensure high surface integrity of the PMMA part.