Material and Process Selection for Ice Maker blades

Root Cause Analysis:
A root cause analysis was conducted on a recalled countertop ice maker, focusing on the failure that led to a safety concern. This analysis was done using data from the United States Consumer Product Safety Commission website. The investigation revealed that the failure stemmed from the auger blade, which posed a significant risk of causing lacerations to users, making it a critical safety issue that needed to be addressed.

Process Plan and Methodology Development:
A comprehensive process plan and methodology were developed to redesign the auger blade, with a strong focus on selecting the appropriate materials and manufacturing processes. This redesign process was informed by mechanical parameters such as mechanical loading and fatigue strength, which were gathered through an extensive literature survey. The goal was to ensure that the new design would be robust enough to avoid the type of failure that occurred in the recalled product.

Redesign Using SolidWorks and Material Selection with Ansys Granta EduPack:
The redesign of the auger blade was executed using SolidWorks, a leading 3D CAD software. The material selection was conducted using Ansys Granta EduPack, a specialized tool for materials engineering. The selection process included strict constraints like fatigue strength to prevent future failures. Free variables in the selection process included the shape of the blade, the materials used, the objective functions for performance, and the material index, which helped in evaluating and ranking materials based on their suitability.

Objective Functions Considered:
Two specific objective functions were prioritized based on the outcomes of the root cause analysis:

Material Screening and Final Selection:
Material screening was a critical step, where constraints such as fatigue strength, resistance to fast fracture, and abrasion resistance were used to filter potential materials. A ranking system was applied using normalized values of the material index, which allowed for a systematic comparison of materials. Out of an initial pool of 422 materials, only 45 met all the criteria after rigorous screening. Among these, Carbon Steel, SA216 (Type WCC), Cast, Normalized was selected as the optimal material due to its superior properties in terms of strength, durability, and cost-effectiveness.

Manufacturing Process Selection:
The selection of the manufacturing process was carefully considered, taking into account the chosen material, available processes, cost implications, and the production volume. The Replicast casting process was selected as the most suitable manufacturing method. This process was chosen because it met all the constraints, including the ability to produce the required number of units (8,000) while maintaining high quality and cost efficiency.

Enhancing Material Properties:
To further enhance the material properties of the auger blade, additional constraints were introduced. These included the need for anti-corrosive properties and a refined surface finish, as the auger is constantly exposed to water. The surface finish and coating were critical for prolonging the blade’s life and maintaining its performance. After evaluating various finishing processes, Plasma chromizing using chemical vapor deposition (CVD) was selected. This treatment was chosen based on its ability to provide a refined surface finish, its compatibility with the selected material, cost considerations, and the production volume of 8,000 units. This treatment significantly improved the blade’s resistance to corrosion and wear, ensuring that the redesign would meet safety and durability standards.

Project Report