## 2 The Development of Typical Rotating Motion Mechanisms
### Ratchet and Pawl Mechanism
#### 2.5.3. New Ratchet Mechanism for Multi-Material Additive Manufacturing Technology
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Types** & **Advantages** & **Disadvantages** & **Applications** \\ \hline \multirow{3}{*}{Elastic deformation [94]} & 3D printing multi-material & \multirow{3}{*}{Easy to fatigue, limited load capacity} & \multirow{3}{*}{Small load scenario} \\  & integrated molding, no spring, compact space & & \\ \cline{1-1}  & Adjustable number of & & \\ \cline{1-1}  & & & \\ \cline{1-1}  & & & \\ \cline{1-1}  & & & \\ \cline{1-1}  & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Comparison of different types of multi-material 3D-printed new ratchet wheels. Figure 40: Four types of ratchet mechanisms (12 teeth and 24 teeth) were printed using PLA and ABS materials. The ratchet and pawl transmission mechanism achieves one-way intermittent transmission through meshing or friction between teeth, which has the advantages of compact structure, reliable directional locking, and flexible modular design. However, it also has common problems such as noise, wear, and limited load. The traditional ratchet adopts a single-claw fixed-tooth-pitch design, which is simple in structure and low in cost but has poor high speed performance and evident noise, mainly suitable for low speed and low load scenarios. Flexible ratchet wheels can be divided into three categories based on the loading method: bending loading type, which replaces spring hinges with cantilever beams to achieve low cost and lightweight but has weak fatigue resistance and is mainly used in light machinery and low-end equipment; Stretch loading type enhances stiffness through short, flexible pivots to achieve high torque ratios, but requires strict material strength requirements, commonly found in electric tools and industrial transmissions. The compression loading type adopts a rigid tooth and flexible segment separation design, which reduces friction while achieving an ultra-high torque ratio. However, the manufacturing process is complex and suitable for heavy machinery and automotive components. In addition, the MEMS micro ratchet, which is based on a silicon-based integrated microstructure, breaks through the limitation of miniaturisation. It has no wear, but due to its minimal output and easy failure, it specialises in microelectromechanical systems and sensors. Modular ratchet gears are designed with multiple discs, claws, and elastic teeth to achieve high load capacity and low noise in response to the demand for high speed transmission. However, their complex structure leads to increased costs, and they are mainly used for pulse transmission in heavy machinery. The micro high speed ratchet adopts an elastic rod design to achieve low friction transmission, but due to low load and insufficient reliability, it is limited to micro-mechanical systems. The elastic deformation type ratchet wheel generated by the new multi-material 3D printing technology replaces springs and gears with an integrated structure, which is compact in space but prone to fatigue and suitable for low load scenarios. The gear optimisation type achieves lightweight and low noise through parameterised tooth profile modeling and PLA/ABS material printing. Although limited by material strength and durability, it still demonstrates cost advantages in low torque scenarios such as small electromechanical equipment and automation instruments. This technology system covers cross-scale applications from micrometer-level sensors to heavy machinery, and its innovative direction is focusing on material composites, structural flexibility, and the integration of additive manufacturing technology.