## 2 Materials and Methods
### Structural Design of the Removal System
#### 2.2.2 Rolling Extrusion Separation Module Design  
Based on the design requirements of the separation system and experimental results of adhered foreign object separation, this paper proposes a rolling-squeezing separation module to achieve effective separation of adhered foreign objects. The module design includes structural design of the inner and outer housing for the rolling unit, structural design of the squeezing unit, and drive system design for the separation mechanism. The housing of the rolling-squeezing separation module adopts a double-layer configuration (Figure 10). The inner housing and the upper section of the outer housing feature a frustum-shaped geometry with a slope angle of 66\({}^{\circ}\), while their lower sections adopt a cylindrical form. All components are fabricated from 304 stainless steel, with overall dimensions measuring 570 mm \(\times\) 294 mm \(\times\) 294 mm. The frustum design facilitates natural downward flow and gradual dispersion of materials under gravity. The conical inclined surface effectively guides materials into the interstitial gap between the inner and outer housings, preventing accumulation or blockage that could compromise separation efficiency. The outer surface of the inner housing incorporates regularly distributed protruding structures. These protrusions increase the contact area and frictional force with materials, generate agitation effects during rotation to enhance separation efficiency, and maintain structural integrity under operational loads. The outer housing remains stationary through fixation to an external framework, ensuring process stability and controllability. The inner housing rotates via a shaft supported by bearing blocks at its top end. A uniform interstitial gap of 9 mm is maintained between the inner and outer housings. This gap allows the passage of raisins and adhered foreign objects while avoiding excessive compression that could damage the products. A feed inlet with dimensions of 62 mm \(\times\) 28 mm is integrated into the sidewall of the outer housing to ensure stable material input. At the bottom of the inner housing, four material collection plates are strategically positioned. After separation, materials fall into the interstitial gap at the housing base, where the collection plates guide them toward the discharge outlet, completing the collection process. The squeezing module serves as the core mechanism for rolling-squeezing separation in this system, with its overall structure illustrated in Figure 11a. Composed of multiple squeezing modules, the assembly includes components such as a flexible squeezing head, compression spring, fixed column, sliding sleeve, and upper/lower fasteners. A composite buffering mechanism is primarily employed to ensure thorough separation of adhered foreign objects while preventing material damage. The individual module structure, shown in Figure 11b, features a flexible material coating on the exterior of the squeezing head, with its interior connected to the sliding sleeve via a compression spring and mounted on fasteners. When materials enter the squeezing module, the flexible surface layer initially de  
Figure 10: Inner and outer housing design. forms to absorb the transient impact generated during raisin-shell squeezing. Subsequently, the spring system provides secondary buffering through axial displacement, reducing peak stress on the raisin surface. Additionally, the squeezing module connects to the rotating shaft via shaft couplings and bearing blocks. The axial floating movement of the spring-loaded sliding sleeve, under centrifugal force generated by motor rotation, creates a compound motion trajectory that enables comprehensive rolling-squeezing action on the raisins. The drive structure of the rolling extrusion separation module adopts a motor-driven system integrated with belt transmission.