CAPSTONE: blndr | Bohlig Portfolio

Mechanical Engineering Capstone: blndr

Northeastern May 2022 - April 2023

Set Up:

Capstone at Northeastern University is a year-long program to research, outline, prototype, and build a solution to problems proposed by faculty. Each team has 5-6 members and an advisor. All work must be completed by Capstone Day where poster presentations, formal presentations, and judging occurs.

Without blndr

With blndr

Background:

Have you ever tried to blend something thick and the blades spin but no food in the jar is moving? This happens because the material is no longer forming a vortex and moving toward the blades. Blenders rely on cavitation, which introduces air into the material and when the air pops it emulsifies the food.

Food processors do not use caviation to blend food and when blending can only achieve subpar, grainy results.

The team wanted to design something that would be a hands-off, add-on solution for any blender user (think 'As Seen on TV').

Problem Statement:

Design a hands-off system that facilitates vortex formation in order to fully blend the contents of a blender.

Prototype Iterations:

Initial testing showed that if the food can be pushed into the blades of the blender, a vortex could be created and the food would flow and blend. The team set out to create a system that would push the food onto the blades without human intervention.

Proof of Concept

Prototype 1

Simple Arduino motor with spatula attached
Proved food could be pushed to facilitate vortex

We used an overpowered motor to test for maximum torque required for system
Motor connected to power supply, final version was battery

Final Design:

Secure lid with gasket
Enclosed battery and motor with an on/off switch for the user
Removable custom spatulas

The final design had four subgroups:

Electronics
Lid and Body
Attachment System
Spatula Over Molding

All custom parts were 3D printed.

Cross Section of Final CAD

Prototype 2

First prototype with battery
Motor was contained to lid
Detail wasn't there yet

Video of blndr

Technical Focus - Spatula Design and Blend Success:

There were many areas of technical focus with this project, I led the vortex formation analysis, testing, and spatula design as well as the interchangable spatula feature.

Problem:

I wanted to quantify success for blndr as a product for producing a vortex, but I also wanted to determine the optimal spatula design for our product. Two spatula options were identified early on to have an affect on vortex formation, flexing tip and scraping the wall of the blender.

The following testing proved blndr decreased the time to vortex formation and found that without wall scraping and a flexible tip had the fastest vortex creation.

Method:

n = 2

200g cooked (boiled) sweet potato, cut to 1"x1"x1" cubes

25 secs of blending

Variables:

1. Scraping the Wall

2. Flexing Tip

Control:

Tested Results:

Technical Focus - Interchangable Spatula Attachment:

For testing, many spatula designs had to be created and I decided to make a spatula attachment system that mimicked the Kitchenaid interchangable attachment style.

Market Research

Prototype 1

Double attachment locations meant double the hardware and complexity
Could allow different spatulas to be used on each side
Sticks screwed in from top with heat set inserts

Final Design

Single attachment location
Spatula sticks printed and filled with metal core then stuck to insert
Simple, low cost, low hardware

Human Factors Research:

To keep the spatulas engaged, a strong spring is preferred. However, since it would be a customer touchpoint, human factors had to be considered on the feel of the spatula change.

I researched grip standards and found an applicable style, the One-Handed Pinch-Grip shown below. Then I selected some OTS springs, calculated their displacement and final spring force. The 4.26 lb spring highlighted had the best feel, kept the spatulas put, and met the standard.