# Using A Rotary Spring-Driven Gripper to Manipulate Objects of Diverse Sizes and Shapes
## 2 Materials and Methods
### Parts and Specification of the Mechanism
\begin{table}
\begin{tabular}{l c c} \hline \hline
**Part’s Name** & **Dimensions (cm) 1** & **Part No.** \\ \hline Outer Shell A & H = 14.7, OR = 14.3, T = 0.3 & 1 \\ \hline Outer Shell B & H = 14.7, R = 14.3, T = 0.3 & 2 \\ \hline Rectangular Slot Plate (Bottom) & OR = 13.9, IR = 8, T = 0.75 & 3 \\ \hline Bearing Ball & D = 1 & 4 \\ \hline Shutter & OR = 11, IR = 5, H = 15.25 & 5 \\ \hline Linear Slot Plate (Top) & OR = 13.9, IR = 6.8, T = 0.75 & 6 \\ \hline Curvilinear Slot Plate & OR = 13.9, IR = 6.8, H = 5.4 & 7 \\ \hline Top Cover & OR = 14.8, H = 24.6 & 8 \\ \hline Motor Cover & 6.3 \(\times\) 6.3 \(\times\) 7.8 & 9 \\ \hline Electronics Box & 10.2 \(\times\) 10.275 \(\times\) 14.7 & 10 \\ \hline Wire Cap & 10.2 \(\times\) 3.075 \(\times\) 5.19 & 11 \\ \hline Piston & R = 0.15, H = 6 & 12 \\ \hline Spring & R = 0.5, T = 0.05, H = 2.5 & 13 \\ \hline Piston Blocker & OR = 0.6, IR = 0.25, H = 0.4 & 14 \\ \hline \hline \end{tabular}  
* Only important dimensions are shown; in the dimension column, O = outer, I = inner, R = radius, T = thickness, and H = height.  
\end{table} 
Table 1: Designed parts with dimensions and part numbers. Figure 2: Shutter CAD model with balloon numbering as part numbers from Table 1.  
converting the motor's rotational motion into linear motion. The grasping state is achieved when the shutters come into contact and form a circular shape. During the design-to-assembly (DFM) process, meticulous attention is given to each part to ensure precise assembly and optimal performance. Carefully determined dimensions facilitate easy assembly and enable the gripper to effectively grasp objects with diameters of 5 cm to 9 cm, encompassing typical vegetables and fruits in grocery stores. However, this design is fully scalable to manipulate objects of different sizes based on user requirements and specific applications. The gripper's diameter can be adjusted to accommodate objects within different size ranges. Additionally, the springs can be readily replaced with alternative springs possessing distinct spring constants, thereby allowing for gripper customization based on the objects' texture (e.g., soft or fragile items) or maximum weight. In the current prototype, the overall assembly has a radius of approximately 14.3 cm, which corresponds to the radius of the outer shells (#1 and #2). The design's total height measures around 34.15 cm (excluding the wire cap), with the top part (#8) housing the motor and gearbox, adding to its height. The top part is rigidly connected to the outer shells. The motor, which is housed within the top cover part, imparts rotational motion, generating circular movement of the curvilinear guide plate (#7), which features a 120-degree slot mechanism that drives the top column of the shutter (#5). All circular plates have an outer diameter of 27.8 cm and a thickness of 0.75 cm. The shutters have outer and inner diameters of 22 cm and 10 cm, respectively, along with a height of 15.25 cm. Figure 2 depicts an image of the shutter with a column extending from its top face. This column maintains contact with the following two distinct plates: the linear guide circular plate (#6) and the curvilinear guide circular plate (#7). The linear guide plate incorporates a slider connection with 1 degree of freedom (DOF), while the curvilinear guide plate features a roller connection with 2 DOFs. A hidden rectangular extrusion is present on the bottom face, serving a similar function as the one on the top face. The motion is initiated when the motor rotates the curvilinear guide plate (#7), causing the circular column to follow the path defined by the slot. The linear guide plate (#6) constrains the motion, resulting in the linear movement of the shutter. The outer face of the shutter contains 12 precisely designed holes, intended for the integration of springs and pistons to provide grasping force. The springs are allowed to fully deflect, with a length of 2.5 cm.