Final Designs

Instruction Manual for Enclosure Assembly 

Picking Your Enclosure

Our design process began by utilizing several different enclosure designs and materials. We identified the Hex design as a basis for the final product due to several advantages, such as: 

• Ease of assembly 

  • No tools or hardware are required to seal the enclosure

• Easy to 3D print due to simple design

  • Two parts: lid and base

• Easy field deployment

We first explored 3D printing as a solution, as it requires little time to modify to a user's specific demands. As the project progressed, we expanded the design and applied it to both 3D printing and PVC fabrication. This was an ideal solution as it would allow end users to create their enclosure based on their resources and needs. We also created a manual which included both instructions and recommendations for the designs. 

Below is a table comparing the PVC and 3D printed enclosure designs. This was made as a tool to quickly provide an overview of the design solutions to users interested in creating an enclosure. 

Enclosure Performance

Testing was done to ensure the enclosures' waterproofing capabilities. This included submerging the enclosures in a marsh environment for one week. We track the humidity of the enclosure to detect any leakage issues. The results are shown below: 

The final PVC enclosure design uses four off-the-shelf standard PVC Schedule (SCH) 40 components to create a watertight enclosure. This includes a female socket end cap, 20.32 cm section of cut PVC tube, male threaded adapter and a threaded end cap, as seen in the exploded view. PVC cement is used to seal and secure the flat end cap and adapter, while the threaded end cap is secured using Teflon tape. Primer is also necessary to use PVC cement to ensure a strong bond. Cable glands are installed into the flat end cap to allow for easy access. An optional 3D printed insert is also glued into the bottom of the enclosure to allow for the ENTS node holder to be easily inserted, removed and secured during deployment. This enclosure takes 30 minutes to manufacture which includes using a bandsaw/saw to cut the PVC tube to length, drilling holes for cable glands, applying PVC primer/cement and waiting for it to dry, printing and installing the insert, and finally applying Teflon tape to the threads. 

The final 3D printed enclosure design is made using off-the-shelf PLA material and measures 22.5 cm long with a diameter of 12.4 cm, seen in the exploded view. In this project, Cerakote sealant was used due to its waterproofing ability and small ecological impact. The final design has holes at the bottom for mounting cable glands for passage of cables similar to the installation of cable glands in the PVC design above. These gland holes are adjustable and scalable per end user depending on their own node configuration and how many wired sensors will be deployed in the field. The 3D print includes an O-ring groove at the top for a waterproof seal. Additionally, when the top screws on, it helps distribute even pressure on the O-ring contributing to its sealing properties. This enclosure was printed using the a Prusa 3D printer at UCSD. With 7 perimeters and 40% infill, the print typically took about 26.75 hours to print when printing both the lid and base simultaneously. If each part was printed on two separate printers, the print time could be reduced down to 14 hours. Manual cable gland and O-ring installation, and sealant coating took an additional 10-20 minutes all together. 

Filament

As 3D printing becomes more popular, different filaments enter the market with the intent of producing varying results. Three different 3D printing filaments were considered, PLA, ASA, and PETG. These options were first compared through online research and analytical methods before the final options, PLA and ASA were tested using test samples. Table 2 below compares the three options considered. 

Our team mainly used PLA for the 3D printed enclosures, as it is the most easily accessible material for most users. Sealants were used to reduce the effect of its disadvantages. 

Sealants

Silicone-based sealants were used to fulfill the functional requirements of the enclosure that 3D printing alone could not complete. These were intended to increase the waterproofing and longevity of the 3D printed enclosure as well as reduce its toxicity to environment by acting as a barrier to the material decomposing in the environment. 

Node Support Insert

Our team also designed an optional insert that would keep the node in place during deployments and help with cable management. It also required minimal rotation to avoid cable tangling and used a twist lock mechanism to allow for easy removal. This insert was configured for both the PVC and 3D printed enclosures. It requires access to a 3D printer to manufacture the component and four 10mm M3 bolts and locknuts to attach the node and optional battery pack.