Technical Report on Hand Mixer for Grip Impairment

Product Pitch:

By creating a fixed stand hand mixer designed for people with impaired grip strength, we eliminate the need for the user to bear weight and maintain grip, therefore reducing pain and increasing efficiency and comfort in overall use.

Product Technical Explanation:

The product is clamped to a table, and the user slides the inner pole of the telescoping rods vertically and affixes it with a pin. The mixer mounting plate sits atop the inner rod and velcro straps secure the hand mixer in place. The user only needs to start and stop the mixer.

Simple Stress and Failure Analysis

Assumptions:

•  2D symmetry

• Any x-direction forces are negligible

• weight of mixer can be estimated as a point load at the center of the platform

• neglect weight of stand

•  moment about y-axis from mixer blades spinning in batter is negligible because resisting the force from batter is small, and assume it is frictionless where the blades turn

The inner rod of the stand is the component of our design that will be used for analysis. This component was chosen because it will experience the greatest stresses due to its geometry, and it is imperative to the concept of our design that this piece is sturdy and able to balance the forces which it will be subjected to. The inner pole is vital to the height adjustment.

Possible failure modes:

• Bending, due to the moment acting on the rod from the placement of the weight on the platform

• Failure due to axial loading

The focus of our design is to create a sturdy stand to support a hand mixer so that people with impaired grip strength do not have to. We wanted to make sure that our design is made with a reliable material that can withstand the job which is required of it, but also have a good lifetime in a hectic environment like a kitchen. To accomplish this, for the inverse analysis the parameter we chose to optimize was the material yield strength of the rod, since that is the component most likely to fail. 

Assumptions:

• 2D symmetry

• Evenly distributed loads

• Any x-direction forces are negligible

• P1 = P2  because symmetry

Factor of Safety: 10

W = 1.45 lb

L = 5 inches

Do = 0.7 inches

Di = 0.63inches

To maintain a factor of safety of 10, we need a material with a yield strength of at least 2700 psi.

Complex Stress and Failure Analysis

Comparison of Simple and Complex Analysis:

The maximum stress from the complex analysis was 56.5 psi and the minimum FOS was 529.9. From simple analysis, the maximum bending stress was 270 psi and the FOS we used was 10. The FOS difference makes sense because we calculated to optimize the material to be used. The FOS of 10 was the baseline we were looking for, so then we only looked for material that had a greater yield stress than 2,700. By using a material with greater yield stress but then keeping the load stress constant, the FOS is forced to be greater due to its direct correlation. Then with the difference is stress, due to the fact that in Solidworks, the load is distributed across the plate instead of being a concentrated point load, therefore explaining why the Solidworks stress is lower. Solidworks was doing a three dimensional simulation where our simple calculations are in two dimensions.

Manufacturing and GD&T

1. For the inner tube, we chose an extrusion manufacturing method, specifically to make seamless tubing. We chose not to go with the other commonly used method of welding so that the welding seam would not impact our tolerances between the inner and outer tube.

2. We chose Stainless Steel 304 as the material of our tubing because it is a food grade material and the extrusion manufacturing method is meant for stainless steel.