06.1 - Project Proposal
Introduction
Manual vegetable slicing is a common kitchen task, but also a significant source of injury. Approximately 350,000 Americans visit emergency rooms annually due to kitchen-related cutting accidents. Beyond safety concerns, hand slicing often produces inconsistent results and can be physically challenging for children or individuals with limited strength or mobility. The project aims to create a safe, automated mechanism that enhances both efficiency and consistency in vegetable slicing.
Description of the problem
Traditional slicing methods require direct human contact with sharp blades, creating safety hazards and inconsistencies in cut thickness. There is a need for a mechanism that can slice vegetables safely, uniformly, and efficiently without relying on user strength or precision. The main challenge lies in converting a motor’s rotational motion into a controlled linear cutting motion while designing an intake mechanism that automatically feeds vegetables through the cutter, eliminating the need for manual handling.
Description of a proposed mechanism that could solve this problem
The proposed design will translate rotational motor motion into linear vertical cutting motion with a linkage system. A feeding mechanism will automatically move the vegetable toward the cutting blade. The system must maintain precise synchronization between the feed rate and cutting cycle to achieve consistent slice thickness. Speed control for the conveyor will allow adjustment of slice size. After the development of a first prototype with the mechanism of cutting and feeding separately, we will investigate the development of a mechanism that synchronizes both movements.
The cutting mechanism will be a 4-bar slider crank linkage that translates the rotational movement from a motor into a linear, up-and-down motion for the blade. Linear motion will be used instead of a knife pivoting about a joint, to allow use to be consistent with different-sized vegetables. It also keeps the blade unexposed, keeping the cutting station safer.
The conveyor mechanism will be a standard conveyor belt design that will use intermittent motion to stop when the knife is cutting through the vegetable and resume movement when the knife is outside of the vegetable. Changing the speed of the motor will allow for different thicknesses of the vegetable.
To explore using synchronized motion between the two mechanisms using only one motor, there will be additional factors to take into consideration. If we want to continue having different settings for the thickness of the vegetable, we will have to explore using some sort of gear switcher.
Proposed scope of work for final project
The project will deliver a functional mechanism capable of:
Accepting straight, firm vegetables like carrots or cucumbers and slicing them automatically with no manual cutting.
Adjusting slice thickness through variable speed control of the feeding system.
Limitations include the exclusion of soft or irregular produce, like bananas and hard-shelled items.
The work will be divided as follows:
A first prototype will be developed with a 4-bar mechanism that moves the blade up and down, coupled with a second separate mechanism to move the vegetable axially. The mechanism will be tested on a softer material, like a cheese stick, and then on a carrot. A position and velocity analysis will be performed to maximize the mechanical advantage at the point of contact between the blade and the surface of the vegetable. Finding a motor strong enough to cut through the vegetable will be a key part of this project.
We will measure the accuracy of the system as the difference between the expected slice thickness and the actual one. We will measure this value for different vegetables, and we will use the different results to improve our prototype.
Finally, a mechanism that incorporates both movements as proposed before will be developed and tested. The use of gear switchers will be explored to allow for different slice thicknesses.
The success of the project will be determined by:
the successful creation of a mechanism able to cut vegetables like carrots and cucumbers;
The synchronization between the mechanism for cutting the vegetable and the feeder determines the slice thickness. The accuracy between the expected slice thickness and the average obtained one will measure the validity of our system. We expect a relative accuracy better than 20%. For instance, a thickness of 5 mm is expected to have an accuracy of about ± 1 mm.
Finally, for a certain slice thickness, the successful creation of a system that connects both mechanisms: the cutter and the conveyor.
Preliminary design ideas
The images above show a side and front view of the proposed mechanism. The first image shows one way we can link the motor to control both the cutting and roller mechanisms. The second image shows the slider crank mechanism for the cutting itself. This is a Grashof 4-bar with one degree of freedom (using Greubler's formula), where the input angle from the motor alone determines the state of the linkage.
We know we will need to maximize cutting force, and as such will design the mechanism so that the transmission angle while cutting is as close to 90o as possible. This will be done by carefully relating the crank and connecting rod link lengths, as well as the angle at which the crank is at when the blade is cutting.