Ninja Digital Air Fry Oven

Background

For my third co-op, I worked at SharkNinja as a mechanical engineer on the Ninja Heated R&D team. This division focused on consumer cooking appliances, and my team specifically was responsible for the ​Ninja® Foodi™ Digital Air Fry Oven, which has since been released to market. As a member of a small, interdisciplinary R&D team, I worked hands-on daily with oven prototypes to perform root cause analysis and develop a strong fundamental understanding of the oven's thermal behavior. Through this work, I helped optimize the oven's performance and inform critical decisions involving mechanical design, control systems, and user experience. 

​Modular Thermocouple Test Fixture

​A major area of work performed by the Ninja Heated R&D team is temperature testing of prototypes and competitive products. This is typically performed using an array of thermocouples taped to a low-mass accessory like a wire rack. For competitive oven testing, the process of taping a wire rack with up to twenty thermocouples is laborious, time consuming, and must be undone if the wire rack needs to be used for actual food testing. In order to make this process more efficient, I designed, fabricated, and tested a modular thermocouple test fixture.

The fixture is constructed of miniature t-slotted aluminum framing and modified off-the-shelf fittings. The fixture's width and depth are adjustable to accommodate the largest and smallest air fry ovens currently on the market. It uses small nut plates to clamp down the ends of thermocouples so they can be easily added and removed. Since the fixture itself acts as a thermal mass within an oven, many factors such as mass, surface area, and specific heat capacity were considered to ensure it did not significantly affect the thermal response of the oven being tested. 

I tested this fixture using an array of clamped thermocouples and compared it to typical baseline data from thermocouples taped to a wire rack. Although it slightly affected the initial temperature rise, it did not affect average steady state temperatures. Interestingly, the effect the fixture had on the temperature rise sparked the idea among my team to add more thermal mass to the fixture to simulate food loads as a more real-use case. The fixture proved to be a significantly more efficient tool than the team's previous taped wire rack method, and will be used by R&D for further temperature testing. 

Temperature Testing & Thermal Data Analysis

The Ninja Digital Air Fry Oven was the first oven project SharkNinja had ever attempted. Even in the later engineering build phases, there was still a lot unknown about the oven's thermal behavior. A major part of my role on the R&D team was learning how exactly the oven functioned on a system level to fine tune its performance per cooking function. Some of the equipment I used when designing experiments included voltage transformers, power meters, thermocouples, current sensors, and data acquisition systems.

I often handled large amounts of temperature data and used Excel to create templates and pertinent graphs to analyze thermal profiles. I distilled hours of testing into key takeways for both technical and non-technical teams to easily understand, including upper-management. By evaluating temperature profiles across different functions and understanding the relationship between the oven's thermistor and the rest of the system, I determined top and bottom heating element power distributions that yielded the most effective and even cooking performance. These power distributions were implemented to certain functions for mass production. ​

Oven Modifications & Prototyping

​At the start of my co-op, the air fry oven project had just reached tool start and entered its engineering build phase. I prototyped various tool-safe oven and accessory modifications using standard shop tools, mainly for metal working. For one project, I used a brake to form sheet metal into a ramp designed to reduce grease buildup in the rear of the oven.

In order to achieve more even cooking performance using functions like Air Fry and Air Roast, I prototyped different veins located within the oven's fan shroud to test the effects of different air flows.

I explored a variety of heating element guard geometries to dictate the percentage of open area for radiation to pass through. There was a fine balance between providing sufficient and even radiation to a variety of food loads while compensating for extra heat loss from the front door of the oven.

Through experimenting hands-on with oven accessories, components, and mechanical features, I explored the balance between different modes of heat transfer and worked to produce the highest level of performance capable within our oven architecture.