## 2 The Development of Typical Rotating Motion Mechanisms
### Cam Mechanism
#### 2.4.4 3D-Printed Cam Formed by Melt Deposition  
[PERSON] et al. [88] compared the performance differences in dimensional accuracy and surface quality between fused deposition forming (FFF) 3D printing and CNC milling manufacturing of fixed-width camshafts, as shown in Figure 37. They proposed a kinematic design method based on Bezier curves to meet the innovative design framework of geometric confinement. Research has shown that the cam made of polylactic acid (PLA) material for 3D printing has a radial dimension error (0.12%) similar to that of a traditional aluminium CNC cam (0.07%). Still, due to the layer-by-layer stacking characteristics, its axial dimension error (1.64%) is significantly higher than that of the milling process (0.54%). The surface roughness (Ra = 10.41 um) is about 20 times worse than that of CNC-machined parts (Ra = 0.50 um). The main advantages of this technology are reflected in rapid prototyping, low cost, and lightweight characteristics, making it suitable for low power transmission scenarios such as educational models; however, its insufficient interlayer bonding strength and surface quality limitations make it difficult to withstand high load and high-wear industrial scenarios, such as automotive camshafts. The research innovatively verified the feasibility of plastic cams in non-power-intensive mechanical systems, providing an experimental basis for applying additive manufacturing  
Figure 36: (**A**) Schematic diagram of a cylindrical cam actuator. (**a**) Extended state, (**b**) mid-stroke, and (**c**) compressed state; (**B**) physical cylindrical cam shock absorber. in customised motion mechanisms, especially suitable for engineering scenarios with low dynamic performance requirements but requiring rapid iteration. Table 6 summarizes and compares the transmission performance of the different cam mechanisms mentioned above. Single-row chain transmission (such as a sleeve roller chain) has a simple structure, easy maintenance, low cost, and long service life. However, it has problems such as high noise, lubrication, low transmission accuracy, and high speed vibration. It is suitable for low load scenarios such as bicycles and motorcycles; multi-row chain transmission improves load-bearing capacity and material utilisation through multi-row tooth design, and cold forging technology is used to reduce stress concentration. However, the processing equipment requires high precision parameter control, making it suitable for industrial machinery, high load, or long-distance transmission. Silent chain transmission is characterized by low noise, high precision, and high efficiency but is limited by torque and speed and is commonly used in high speed precision equipment such as automotive engines and machine tools. The bidirectional chain drive suppresses the polygonal effect through phase difference, enhances stability and wear resistance, and has a lightweight structure but high installation accuracy requirements, making it suitable for high speed and high precision transmission systems. Composite material chain drives (such as glass fiber reinforced IPN resin) have the advantages of being lightweight, corrosion resistant, and vibration and