Project Goal: Eliminate air bubbles from the custom, in-house potting process that Apogee Instruments uses to pot and isothermally fill their in-house made parts. These parts are usually sent to various environments which requires full insulation and isothermal properties of all components.

Problem Description: Apogee Instruments uses a two part potting compound to protect and house their electronic sensors. During the mixing process of the potting, air is introduced and can become trapped within the potted sensor. These air bubbles create poor insulation within sensors, and increase the risk of part failure. Currently, these air bubbles are eliminated using a blowtorch which increases the time of the potting process. In the current state, potting is mixed by hand using a plastic cup and spoon. Potting is mixed daily according to the demands of instrument production during any given time. The purpose of this project is to find a new method or develop a device to minimize and eliminate the air bubbles that are introduced in the potting mixing process. This device will be used to accelerate the mixing process so that constant observation and popping of bubbles is not required. The main goal is to remove bubbles to ensure that the sensors are insulated and filled correctly.

Updated Performance Review

Design Process

Initial ideas such as a centrifuge, vibration tables, and a small scale vacuum chamber were considered. Testing deemed these ideas insufficient. Testing led the team to, as close as possible, combine the heating and vacuum element of our design process.

The best combination of the heating and vacuum process came in the form of a mounting board that had a two step process: initially heating our epoxy, then simultaneous heating and degassing of the combined epoxy and catalyst.

Other parts of our mounting board include a heating pad temperature monitor, power strips, and handles. These parts are considered secondary to the design.

Outside of the mounting board involves two key parts of our refined potting process: a fume extractor (not mounted due to size), and an isopropyl alcohol spray bottle (not mounted due to replaceability).

Testing Process

Initial testing explored the abilities of the both the catalyst and the epoxy that Apogee uses to make their in house potting compound.

Secondary testing explored custom fixes as followers: vibration machines, centrifugal force based machines, vacuum based machines. Other testing fully explored subsidiary solutions like alcohol spray that lowers the surface tension, and high heat that maintains the malleability and mixability of the potting compound.

From the secondary testing, we decided to combine various methods to yield the best results. The final design combines heating, vacuuming, and the alcohol spray. An initial trial of this combination gave promising results.

Final testing explored the use of an infrared lamp to maintain the temperature while in the vacuum chamber, mixing before placing in the vacuum chamber, and pouring the potting into the sensor capsules

Conclusion

The most important requirement to fulfil was to eliminate air bubbles in the potting process. This was achieved, while also maintaining a small device size, that allows for mixing of large quantities of potting within a safe temperature range. Our design is also easy to clean and maintain.

Our group learned the true worth of testing. In theory, many different applications could have achieved good results for this project. However, only through thorough testing, could a true working design be found. Other ideas like a centrifuge, vibrations tables, or radial heating were tested with high hopes, and did not work.

A simple step by step manual will come along with our mounting board. The manual will also outline likely replacements in the coming years, like the pump motor and infrared light bulbs. We recommend our design be implemented ASAP at Apogee Instruments