Electric Fruit and Vegetable Slicing Machine

Motivation

We set out to design a fruit and vegetable chopper for users with limited grip strength or dexterity. The goal was to create a device that mimics the slicing motion of a knife but is safer, ergonomic, and reliable — first manually, then automatically.

Phase 1: Manual Chopper

Objective: Develop a manually operated chopper that replicates realistic cutting motion while staying within a 7x7x10 in. constraint.

Result: The prototype successfully cut soft foods (bananas, mozzarella sticks) and demonstrated feasibility of a one-handed, ergonomic design.

Mechanism Selection: Modeled and tested multiple linkage options; settled on a four-bar crank-rocker linkage to replicate the tip-to-base rocking motion of a knife.

Kinematic Analysis: Calculated link ratios to satisfy Grashof’s condition, ensuring continuous rotation of the crank and eliminating toggle points.

CAD & Prototyping: Designed the linkage in SolidWorks, produced parts via 3D printing, and assembled with push-fit dowels for smooth operation.

Validation: Conducted motion tracking on the blade tip to compare experimental paths against predicted kinematics.

Phase 2: Automatic Chopper

Objective: Automate the slicing process with synchronized feeding and cutting.

Result: Both slicer and feeder worked individually, but synchronization issues caused interference and gear shear. This highlighted tolerance challenges in multi-subsystem designs.

Process & Tools

Linkage Design (Orange Mechanism): Used a Grashof Class I four-bar linkage for the slicer, ensuring realistic cutting motion.

Feeder Mechanism (Blue Mechanism): Designed a rack-and-pinion with dwell periods calculated to synchronize push/pull motion with blade cycles.

Dwell: ~73.5° during slice, 143° rise/fall for reset.
Gear Train: Designed an 11:1 gear ratio train to drive both slicer and feeder off a single DC motor.

Kinematic & Dynamic Analysis

Position, Velocity, Acceleration (PVA): MATLAB simulation verified linkage motion.

Dynamic Force Analysis (DFA): Estimated torque requirements using experimental force data (5–9 N to cut food).

Tracking Analysis: Compared experimental blade paths with MATLAB outputs to validate model accuracy.

Fabrication and Assembly

Combined laser-cut acrylic housing (transparent for visibility) with 3D-printed gears, racks, and brackets, tuned for tight tolerances.

Key Takeaways

Applied mechanism theory (Grashof condition, DOF analysis) to select and validate linkages.
Used MATLAB simulations for kinematics (PVA), dynamics (DFA), and synchronization analysis.
Validated with experimental tracking to compare real vs. theoretical motion paths.
Iterated through fabrication constraints, learning how tolerance, dwell timing, and synchronization impact real-world system reliability.

Future iterations would improve gear strength, synchronization tolerances, and dwell timing to achieve reliable automated slicing.

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