## 2 Materials and Methods
### Overview of the Case Study
#### 2.3.1 Traditional vs. Smart Manual Assembly Workstation  
The main advantage of a smart manual assembly workstation is that it not only advances in the development of the visualization but also takes over the entire assembly process, i.e., it takes into account the individual worker, prevents errors with appropriate instructions and smart technologies and takes care of ergonomic suitability of the workplace. On this basis, the worker can carry out error-free assembly of the product without additional training in process and technology. Figure 6 shows the methodology of the case study, which is divided into a description and functioning of a traditional and smart manual assembly workstation, as well as a description of experimental work involving workers, the product and a DHM simulation to determine ergonomic suitability. The study provides results on the time required to perform the assembly process, the number of errors at a smart and traditional workplace during the assembling the product and the assessment of the ergonomic design.  
The functionalities of traditional workstations in the case study are (i) seated workstation, (ii) height-adjustable classic chair, (iii) workbench at a fixed height, (iv) fixed position and angle of the grab containers, (v) industrial lighting, but unfortunately too weak with an illuminance of 166 lux for detailed work with small parts (the recommendation for this work is 1000-1500 lux [36]), (vi) instructions on the papers so that the workers have to turn the pages and follow the assembly sequence all by themselves, and (vii) fixed assembly nest (Figure 7a).  
Figure 6: Overview of the case study.  
The functionalities of our smart assembly workstation are beside the intelligent algorithm: (i) optional sitting/standing workstation, (ii) height-adjustable workbench (set at the height recommended by [33; 37]) for each worker), (iii) distance and angle adjustable grab containers. They move within the reach of the worker if they contain a part by product structure for the assembly operation, or they move out of reach if they do not contain the part required by the assembly structure. Six grab containers, which are attached to the same rails are adjusted simultaneously. To avoid the mistakes of finding the right part in one of these six grab containers, the smart manual workstation also features (iv) Pick-by-Light technology. This technology guides the worker through the structure of the product and displays the grab container with the relevant part that the worker needs to use during assembly. Other smart technologies and tools implemented include (v) adjustable lights that independently focus on the assembly nest, (vi) interactive digital instructions, named LPM software that guides the worker through the assembly process/product structure; it is only the worker's job to confirm the completed assembly task by clicking the \"Next\" button, and (vii) rotatable assembly nest that rotates according to the optimal direction of the assembly operations. We have also implemented AR and VR on a smart workstation, but these technologies are not relevant to the experiment in this study (Figure 7b).