During the preparatory study, many different standard requirements were encountered and examined to ensure that all requirements would be fulfilled when designing the Smart Plug [13], [21], [22]. This was a necessary but time-consuming part. If deviations from the requirements were made, the developed product would not have been an acceptable product to sell due to personal safety concerns for the customer [16], [17], [20]. Due to the many requirements of dimensions for the plug and socket, the possibility to utilize the advantages of the traditionally used product development process were limited [14], [15], [38]. Another factor that partly prevented the possibility to effectively utilize the traditional product development process was the predeveloped PCBs’. Due to the position of the terminal springs, placement of certain components etc., certain parts had to be designed to be located in certain positions or placements, limiting the possibility of concept generation for the project [14], [15].
A Smart Plug is a power receptacle that allows the user to control any appliances that is plugged in the outlet. This means that it would be advantageous from a marketing standpoint if the Smart Plug itself is minimized in size since it would infer that the inserted plug protrudes less from the wall socket. It would also create a Smart Plug that is visibility minimized when mounted on the wall socket. The one concept solution that was produced in the concept selection phase had therefore as its main purpose of minimizing the Smart plug, both in length and width. This was achieved by forming the design alongside the PCB assembly in the horizontal direction, and by minimizing the distances in the vertical direction after required measurements and tolerances had been taken into account.
The concept and alterable parts that was generated through brainstorming was not performed in a group session. Brainstorming in group sessions is generally more advantageous since it can generate more concept solutions ideas. This may very well be a factor to the limited concept solution and alterable parts produced during concept generation [34]. Brainstorming was also the only concept generation method performed during this degree project. In order to attempt to generate more concepts solution ideas, the usage of other creative methods would have been beneficial [34].
Comparison with traditional concept development process
When comparing the traditional product development process to the one performed during this degree project, it is clear that not all steps were followed [34].
Systematic methods were performed when standard requirements were investigated. Creative methods were also performed, although not various variants of creative methods and not by numerous people in a group, which generally is the optimal method of performing creative methods [34].
A morphological analysis was not performed during this degree work, and the three-step evaluation only consisted of one step. This since only two alternatives per alternative parts were created, where only one of these alternatives per part got through the elimination matrix [34].
If more solution ideas would have been created, the traditional product development process may have been able to be followed. By following the traditional product development process, a better suited solution might would have been generated. More solution ideas may have been generated if more creative methods would have been performed during this phase. It may also have created more solution ideas if the creative methods were performed in groups. However, due to the limitations presented on start of the project, alterations to the traditional product development process had to be performed in order to be able to perform any sort of product development.
Product design
The developed product design fulfills all requirements and the designed Smart Plug is fully completed in all aspects apart from the surface finishing design where the company name or logo will be displayed. By determining the manufacturing method before designing the 3D-model, appropriate design additions were made when designing the product [35]. If the manufacturing method would have been determined after the design of the product was completed, alterations would have had to be made which could potentially delay the project work [35].
During the product design phase, the additive manufactured prototypes were of great assistance.
When the first prototype was manufactured, it became clearer what parts of the design that needed improvements. By being able to see and touch the designed Smart Plug, both advantages and disadvantages with the design at that stage were more easily identified and the disadvantages could thereafter be modified accordingly. After alterations were made by examining the first prototype, a second prototype was manufactured. Once again, the prototype helped to analyze the design of the Smart Plug, which after the creation of the second prototype did not need alterations.
Material selection
Only one material selection was performed on the entire casing. This could be seen as a disadvantage since different parts may have different constraints and loading conditions, creating different performance equations. It could therefore be advantageous to perform separate material selections for the different parts. From a recycling perspective however, it is
an advantage to only have one polymer to handle since it could be demanding to separate several polymers when recycling.
Although several material selections could have been performed, both the plug and socket design are distinctly visible to the consumer, making UV-radiation resistance an important factor. If the plug and socket were made from different materials, one part may obtain discolorations faster than the other which affects the visual appearance of the Smart Plug. Since the Smart Plug is intended to be a consumer product, visual appearance is an important aspect that should be taken into consideration. Even if two separate materials may have a good UV-radiation resistance, it is probable that they do not have an equally as good UV-resistance. This would result in visible uneven discolorations along the exterior of the Smart Plug [44]. Due to this, the optimal material for both the plug and socket should be the same material, as the one performed during this degree project.
The material selection was optimized for the plug and socket, which has more requirements due to their exterior visibility to consumers. The material selections for the other parts of the Smart Plug casing could have been performed separately from the plug and socket, as well as from each other. However, as mentioned above, this was not performed due to the limited time this degree project had.
PLA, that was the chosen material for the Smart Plug, has a low glass transition temperature.
However, the costumer requirement had an obligatory demand that the product must be able to operate during temperatures in the range of 0°C - 40°C, which PLA satisfies.
FE-analysis
On almost all drop simulations, the stresses absorbed by the Smart Plug casing were on some designed parts at, or over, the yield stress of the material. This mostly regard the design of the plug. An iterative process, in order to obtain the desired results, is a necessary next step to perform. This was however not possible to accomplish during this degree project due to time limitations.
The button also absorbed high stresses during front impact simulations. The entire button is constructed with PLA. A common way to design a button is to construct the actual button in Silicone, which could help lower the absorbed stresses. This would be a possible solution to the absorbed high stresses and would be a good next step to investigate for the design of the button.
The analysis performed on the Smart Plug was a linear elastic analysis. Even though this was a good approximation of how the structure behaves, it is important to further investigate the plug and button design since they absorbed stresses above the yield stress. When absorbed stresses surpasses the yield stress, the structure is subjected to plastic deformation and not elastic as the analysis assumes. Since high voltage runs through the Smart Plug when the Smart Plug is plugged in a wall socket, plastic deformation on the product is critical to further investigate and alter if necessary.