Proctor Silex Knife Accessibility Redesign
Project Overview & Client
The purpose of this project was to redesign a common household object to better serve Emily, a user with cerebral palsy. In response to her specific needs and challenges, I undertook a comprehensive design process to create a more accessible and functional version of the object. This involved analyzing Emily’s requirements, brainstorming and prototyping solutions, and refining the design to improve usability and comfort. The final redesign aimed to enhance Emily’s safety and accuracy of cutting while using the knife.
My Role
Human Factors Engineer
My Team
1 Human Factors Engineer
2 Mechanical Engineers
Type of Project
ME 40: Engineering Design Semester Project
Project Timeline
Spring 2022
Part 1: Evaluating The Original Design
Before starting the redesign process, it was crucial for me to become thoroughly familiar with the existing Proctor Silex Electric Knife. I took a hands-on approach by observing how users interacted with the knife, disassembling it to analyze its components, and then reassembling it to understand how everything fits and functions together. This thorough examination helped me fully grasp the knife’s design and pinpoint areas where improvements were needed.
User Research
I gathered information before examining the physical product to get a comprehensive view of the knife’s intended use, user needs, and potential design issues from a broader perspective. This approach helped me understand key design considerations, like its versatility and suitability for different users, and pinpoint areas for improvement. By grasping these aspects early on, I was able to build a solid foundation for more detailed analysis and refinement in the redesign process.
External Product Overview
After conducting user research, I turned my attention to the physical design of the electric knife to gain a comprehensive understanding of its user interactions. I identified four key areas to focus on for my redesign: the On-Off Interface, which users activate like a gun trigger; the Blade Release Interface, which is less frequently used due to its more challenging operation; the Slot for inserting additional components; and the Handle, designed for ergonomic comfort. This detailed examination was essential for narrowing my focus to these critical interaction points. By understanding how users engage with these interfaces, I could pinpoint specific aspects that required improvement to enhance overall usability and safety in the redesign process.
Task Analysis of Novice User
Following our initial user research, I conducted live observations and completed 4 task analysis’s to see how different users interacted with the knife. I documented their unpacking, assembly, and usage, noting how each of them made cuts and adjusted their grip. We assessed the impact of factors like unstable surfaces and poor lighting on efficiency.
Disassembly: Decomposition Table
After observing the knife’s use and reviewing feedback, I disassembled it to study its internal structure, focusing on the four key features: the motor, blades, handle, and control mechanisms. Creating a Decomposition Table helped analyze where each component fit in relation to each other to achieve the knife’s overall function.
Disassembly: Function Structure
Creating a function structure diagram was essential for understanding not only how the components of the Proctor Silex Electric Knife fit together but also how information flows through the various subcomponents to enable its functionality. This diagram allowed us to map out how different parts, like the motor, blades, and control mechanisms, interact and how data and power move through the system.
Reassembly using 3D SOLIDWORKS
Recreating the original product in SOLIDWORKS was a crucial final step because it allowed us to model and analyze all components in 3D. This step provided a detailed blueprint for refining the product in our subsequent redesign phase.
Part 2: Redesign For Emily
Problem Statement
Emily experiences shakiness and limited mobility in her arms and hands, which hinders her ability to make precise cuts of meat in her kitchen, leading to a high risk of injury. Our solution aims to enhance Emily's ability to maintain a correct holding position and incorporate a mechanism that minimizes the risk of accidental injury caused by difficulties in maintaining a proper grip.
Defining Emily’s Needs & Requirements
As the first step in my redesign process, I defined Emily’s needs through a few difference lenses. I focused on operational requirements like automating the cutting process for one-handed use, and functional needs such as managing excess heat and ensuring easy on-off adjustments. I also considered system requirements, including size, compliance with safety standards, and ease of use. This initial focus was important because it provided a clear framework for the redesign, ensuring that the knife would be practical, safe, and tailored to Emily’s specific needs.
Market Research on Existing Solutions
I conducted market research to pinpoint gaps and opportunities in electric knives by examining patents and existing assistive kitchen tools. I discovered that grip texture and the angle between the grip and blade are vital for usability, especially for users with different physical abilities. Insights from stabilization techniques used in products like Liftware and Swedish cutting boards highlighted the need for improved safety features, ergonomic design, and better control in our redesign to enhance accessibility and user experience.
Defining Engineering Specifications
Defining the engineering specifications for the redesigned knife involved a structured approach, similar to how I defined Emily’s needs. I pinpointed specific requirements such as safety features, grip texture, and blade angle, and organized them into a detailed framework tailored to this design. Setting these constraints helped me define clear boundaries that focused my process, guiding me to address essential elements like accommodating users with limited wrist extension and ensuring consistent cutting performance.
Ideation Techniques
Brainstorming with tools like the Memory Map and Dimension-Time-Cost (DTC) Operator helped me understand how to work within design constraints creatively. Imagining extreme cases, such as a chainsaw for large dimensions or laser beams for rapid cutting, highlighted how to balance size, time, and cost constraints effectively. This experience reinforced the importance of defining clear constraints, which guided me to develop practical and user-focused solutions for the knife.
Idea Development
In my approach to idea development, I concentrated on four key areas: physical changes to the product, workflow adjustments, environmental adaptations, and safety features.
Down Selection
By combining insights from market research with our own concepts, I evaluated each option based on how well it met requirements for safety, ergonomic design, and accuracy. This process allowed me to narrow down to the most effective solution for our final prototype, ensuring it was both innovative and practical while directly addressing Emily’s specific challenges with grip and handling.
Final Prototype
We considered both physical alterations and additional extension pieces to enhance safety and accuracy for Emily. By incorporating a clamp with an opposable arm, we minimized the risk of the knife falling and ensured it remained secure if the user lost their grip. We also improved comfort with a textured, rubbery grip and adjusted the knife’s orientation to a right-angle position. Comparing our risk matrix to the original Proctor Silex knife, our redesign significantly reduced the chances of discomfort and accidents associated with oblique grips and small error tolerances, which posed a high risk to Emily.
How Redesign Addresses Key Findings
Power Grip
Elimination of oblique holding position will improve Emily’s grip on the device, thereby leading to increased accuracy of her knife skills.
Support in Motion
The clamp attachment with ball & socket arm design can connect device to the edge of Emily’s kitchen counter, altering the catatonical use of this product to be from a seated position. This attachment can also help alleviate excess strain on Emily’s hand and arm and counteract involuntary movements.
Visual Safety Cues
Along with vibrational feedback, the inclusion of an LED light at the back of the device will visually indicate system status to Emily.
Simplified Controls
Pressure button for activation of the knife is easier to maintain with grip on the product than pull toggle design of original product. Simplification of this design also reduces the sequences of movement required to active and deactivate the product for more efficient use.
Reflections
Innovation through Constraint-Based Creativity
I learned how constraints can be a powerful catalyst for innovation. The limitations of safety standards and ergonomic requirements pushed me to think outside the box and come up with creative solutions that I might not have considered otherwise. This experience reinforced my belief that constraints are not obstacles but opportunities for inventive thinking.
Be Proactive (Early & Often)
This project revealed how essential it is to be proactive by immersing oneself in the intricacies of both the product and its intended use. By diving deep into the Proctor Silex knife’s design and understanding Emily’s unique needs, I could foresee potential safety and usability issues before they surfaced. This thorough grasp allowed me to weave in preventative measures and safety features from the start, leading to a more streamlined development process and a final product that was both robust and user-centric.